Nitrifying

Water Sci Technol, 2003, 48(11-12), 199 - 206
Treatment of domestic sewage at low temperature in a two-anaerobic step system followed by a trickling filter; Elmitwalli TA et al.; The treatment of domestic sewage at low temperature was studied in a two-anaerobic-step system followed by an aerobic step, consisting of an anaerobic filter (AF) + an anaerobic hybrid (AH) + polyurethane-foam trickling filter (PTF) . The AF+AH system was operated at a hydraulic retention time (HRT) of 3+6 h at a controlled temperature of 13 degrees C, while the PTF was operated without wastewater recirculation at different hydraulic loading rates (HLR) of 41, 15.4 and 2.6 m3/m2/d at ambient temperature (ca . 15-18 degrees C) . The AF reactor removed the major part of the total and suspended COD, viz . 46 and 58% respectively . The AH reactor with granular sludge was efficient in the removal and conversion of the anaerobically biodegradable COD . The AF+AH system removed 63% of total COD and converted 46% of the influent total COD to methane . At a HLR of 41 m3/m2/d, the COD removal was limited in the PTF, while at HLR of 15.4 and 2.6 m3/m2/d, a high total COD removal of 54-57% was achieved without a significant difference between the two HLRs . The PTF was mainly efficient in the removal of particles (suspended and colloidal COD removal were 75-90% and 75-83% respectively), which were not removed in the anaerobic two-step . The overall total COD removal in the AF+AH+PTF system was 85% . Decreasing the HLR from 15.4 to 2.6 m3/m2/d, only increased the nitrification rate efficiency in the PTF from 22% to 60% . Also, at HLR of 15.4 and 2.6 m3/m2/d, PTF showed a similar removal for E . coli by about 2 log . Therefore, the effluent of AF+AH+PTF system can be utilised for restricted irrigation in order to close water and nutrients cycles . Moreover, such a system represents a high-load and a low-cost technology, which is a suitable solution for developing countries.

Water Sci Technol, 2003, 48(11-12), 161 - 7
A small scale hydroponics wastewater treatment system under Swedish conditions; Norstrom A et al.; A treatment plant using conventional biological treatment combined with hydroponics and microalgae is constructed in a greenhouse in the area of Stockholm, Sweden . The treatment plant is built for research purposes and presently treats 0.559 m3 of domestic wastewater from the surrounding area per day . The system uses anoxic pre-denitrification followed by aerobic tanks for nitrification and plant growth . A microalgal step further reduces phosphorus, and a final sand filter polishes the water . During a three week period in July 2002 the treatment capacity of this system was evaluated with respect to removal of organic matter, phosphorus and nitrogen . 90% COD removal was obtained early in the system . Nitrification and denitrification was well established with total nitrogen reduction of 72% . Phosphorus was removed by 47% in the process . However, higher phosphorus removal values are expected as the microalgal step will be further developed . The results show that acceptable treatment can be achieved using this kind of system . Further optimisation of the system will lead to clean water as well as valuable plants to be harvested from the nutrient rich wastewater.

Water Sci Technol, 2003, 48(11-12), 147 - 52
Intermittent sand filtration for wastewater treatment in rural areas of the Middle East--a pilot study; Sabbah I et al.; This paper concentrates on Intermittent Sand Filtration (ISF) as a polishing stage for effluent from a facultative pond . During the three-year research program, the system operated with an influent flow-rate of 500-1,000 L/day and an average BOD concentration of 200-400 hydraulic and BOD loadings of 110-200 L/m2/day and 20-40 gBOD/m2/day, respectively . Flow to the ISF was applied intermittently with a different number of doses in each run . In addition, the effects of the frequency and the duration of rest periods (no feeding) were studied . Removal of 90-95% of BOD and 75-90% of COD and TSS was achieved consistently throughout the study period . Elevated levels of nitrification were observed with 95-100% removal of NH3 . The ISF performed best when fed with 5-10 doses/day . Reducing the daily number of doses to 3/day at the same hydraulic loading rate resulted in a 20-30% reduction in removal efficiency . The 2-4 week rest period had no effect on the biological activity in the subsequent run . However, rest periods of more than 30 days were found to negatively affect removal efficiency.

Lett Appl Microbiol, 2004, 38(2), 106 - 12
Growth kinetics of aerobic granules developed in sequencing batch reactors; Yang SF et al.; AIMS: This paper attempts to develop a kinetic model to describe the growth of aerobic granules developed under different operation conditions . METHODS AND RESULTS: A series of experiments were conducted by using four-column sequencing batch reactors to study the formation of aerobic granules under different conditions, e.g . organic loading rates, hydrodynamic shear forces and substrate N/COD ratios . A simple kinetic model based on the Linear Phenomenological Equation was successfully derived to describe the growth of aerobic granules . It was found that the growth of aerobic granules in terms of equilibrium size and size-dependent growth rate were inversely related to shear force imposed to microbial community, while a high organic loading favoured the growth of aerobic granules, leading to a large size granule . The effect of substrate N/COD ratio on the growth kinetics of aerobic granules was realized through change in microbial populations, and enriched nitrifying population in aerobic granules developed at high substrate N/COD ratio resulted in a low overall growth rate of aerobic granules . CONCLUSIONS: The proposed model can provide good prediction for the growth of aerobic granules indicated by the correlation coefficient >0.95 . SIGNIFICANCE AND IMPACT OF THE STUDY: The kinetic model proposed could offer a useful tool for studying the growth kinetics of cell-to-cell immobilization process . The study confirmed that the growth of aerobic granules and biofilms are subject to a similar kinetic pattern . This work would also be helpful for better understanding the mechanism of aerobic granulation.

Environ Manage . 2004 Jan 28; {Epub ahead of print}
Effects of Silvicultural Practices on Soil Carbon and Nitrogen in a Nitrogen Saturated Central Appalachian (USA) Hardwood Forest Ecosystem; Gilliam FS et al.; Silvicultural treatments represent disturbances to forest ecosystems often resulting in transient increases in net nitrification and leaching of nitrate and base cations from the soil . Response of soil carbon (C) is more complex, decreasing from enhanced soil respiration and increasing from enhanced postharvest inputs of detritus . Because nitrogen (N) saturation can have similar effects on cation mobility, timber harvesting in N-saturated forests may contribute to a decline in both soil C and base cation fertility, decreasing tree growth . Although studies have addressed effects of either forest harvesting or N saturation separately, few data exist on their combined effects . Our study examined the responses of soil C and N to several commercially used silvicultural treatments within the Fernow Experimental Forest, West Virginia, USA, a site with N-saturated soils . Soil analyses included soil organic matter (SOM), C, N, C/N ratios, pH, and net nitrification . We hypothesized the following gradient of disturbance intensity among silvicultural practices (from most to least intense): even-age with intensive harvesting (EA-I), even-age with extensive harvesting, even-age with commercial harvesting, diameter limit, and single-tree harvesting (ST) . We anticipated that effects on soil C and N would be greatest for EA-I and least with ST . Tree species exhibited a response to the gradient of disturbance intensity, with early successional species more predominant in high-intensity treatments and late successional species more predominant in low-intensity treatments . Results for soil variables, however, generally did not support our predictions, with few significant differences among treatments and between treatments and their paired controls for any of the measured soil variables . Multiple regression indicated that the best predictors for net nitrification among samples were SOM (positive relationship) and pH (negative relationship) . This finding confirms the challenge of sustainable management of N-saturated forests.

Water Res, 2004 Feb, 38(3), 523 - 30
Bioaugmentation for nitrification at cold temperatures; Head MA et al.; Bioaugmentation of nitrifying bacteria for short solids retention time (short-SRT) nitrification is an attractive alternative for wastewater treatment plants in cold climates or for those in the process of upgrading to include nitrification . One possible source of ammonia for the production of nitrifying bacteria is the liquor generated during the dewatering of anaerobically digested sludges . The objectives of this study was to determine the impact of sudden decrease in temperature on nitrification rates and to determine if nitrification could be accomplished in sequencing batch reactors (SBRs) at 10 degrees C by seeding nitrifying bacteria acclimated to 20 degrees C . In this research, biomass produced during warm nitrification of dewatering liquor was seeded into cold SBRs at various hydraulic retention times from 43.3 to 96 h . The average decreases in nitrification rates were 58%, 71% and 82% for biomass cooled to 10 degrees C when the biomass was acclimated to 20 degrees C, 25 degrees C and 30 degrees C, respectively . The seeded SRTs of the cold SBRs were raised above the minimum solids retention time (SRT(min)) required for nitrification . Full ammonia nitrogen removal was achieved in cold SBRs that were operated at an apparent SRT less than SRT(min).

Huan Jing Ke Xue, 2003 Sep, 24(5), 97 - 101
{Performance and its influencing factors of a zeolite biofilter for dilute domestic wastewater treatment}; Tian W et al.; To reuse dilute domestic wastewater in power plant region as the makeup of recirculating cooling water, a renovate reactor--zeolite media biological aerated filter (ZBAF) was developed . A pilot scale ZBAF of 0.2 m in diameter and 3 m in media height was tested to treat dilute domestic wastewater . The results showed that turbidity, BOD5, CODcr and NH4(+)-N in effluent was 3.2 NTU, 3.2 mg/L, 14.5 mg/L and 0.5 mg/L when the corresponding influent concentration was 59 NTU, 30 mg/L, 81 mg/L and 16 mg/L, respectively, under the conditions of t = 12 degrees C-17 degrees C, HRT = 1.4 h and gas/liquid = 4:1 . The effluent quality met the water quality standards of the treated water reused for cooling water makeup . The removal rate of BOD5, COD and turbidity did not change much with the change of HRT and the ratio of gas to liquid, but NH4(+)-N removal rate changed greatly . The parameters along the depth of ZBAF showed that the biofilm phase was abundant in carbon-oxidation/nitrification(C/N) zone and simplex in nitrification (N) zone . Ciliate was plentiful in C/N zone . Biofilm in N zone was mainly consists of nitrifiers . The point that the number of ciliate decreased apparently was the boundary of the two zones.

Huan Jing Ke Xue, 2003 Sep, 24(5), 92 - 6
{Rural sewage treatment performance of constructed wetlands with different depths}; Liu C et al.; The treatment performance, for low concentration rural sewage, through constructed wetlands of different depths(60 cm and 40 cm), was comparatively investigated by using pilot-scale apparatus in Lake Dian-chi area, Yunnan province, China . The experiment results showed, under a high hydraulic loading rate of 30 cm/d, that the removal efficiencies of COD, total nitrogen, ammonia-nitrogen and total phosphorus in the constructed wetland of 60 cm depth were 66.4%, 57.7%, 78.7% and 63.2%, respectively, and were 63.8%, 59.1%, 82.1% and 61.3% in the 40 cm depth, respectively . The removal efficiencies of COD and total phosphorus in the constructed wetland of 60 cm depths were higher than those in the 40 cm depth, but the nitrogen removal efficiency in the latter was higher than that in the former . Nitrogen and phosphorus removal mechanisms were studied . The results showed that nitrogen removal through nitrification/denitrification and the phosphorus removal through absorb and sedimentation were their main removal mechanisms . The nitrogen and phosphorus removed by plant harvesting were amounting to 10% and 9% of input TN and TP, respectively, which was also an important removal pathway for nitrogen and phosphorus.

Huan Jing Ke Xue, 2003 Sep, 24(5), 75 - 80
{Effect and mechanism of removal of nitrogen in the mimic sewage using bio-zeolite system}; Zhang X et al.; On the spot, the removal effect of pollutants such as NH3-N, N, NO3(-)-N, NO2-(-)N, TN and COD in the mimic sewage by bio-zeolite system was studied . The following results were obtained: it was obvious and stable for the removal of NH3-N by bio-zeolite with a removal efficiency over 95%, but the removal effect of NO3(-)-N was affected deeply by hydraulic retention time, according to the different removal mechanism; chemical adsorption and ion exchange were the main reasons for the removal of NH3-N as well as nitrification by microbe, while denitrification was the main reason for the removal of NO3(-)-N . Nitrification intensity of bio-zeolite was affected by the concentration of dissolved oxygen in the solution, so the nitrification intensity of bio-zeolite on the surface of the zeolite bed was two times of that in the middle in vertical direction . Denitrification intensity changed with different values of C/N in the study, and it could reach the maximum while COD/TN was 5; as for denitrification velocity, it was largest in the first six hour.

Huan Jing Ke Xue, 2003 Sep, 24(5), 70 - 4
{Effects of colloidal organic substrate on nitrification in biofilms}; Li J et al.; The effects of colloidal and soluble organic substrates on nitrification in biofilms were investigated in biological aerated filters . The results showed that the hydrolysis process of colloidal organic matter took place rapidly, which could not be the limiting step of its oxidation in the biofilm . Some 70% organic matter oxidation was accomplished at the 40 cm at the bottom of the both filters, while the increase of organic matter in the influent resulted in the displacement of nitrification from the bottom to the upper part of filter bed . It was observed that the greater reduction on nitrification was caused by colloidal organic matter than by soluble organics at the same COD concentration.

J Plant Physiol, 2003 Dec, 160(12), 1517 - 23
Dicyandiamide and 3,4-dimethyl pyrazole phosphate decrease N2O emissions from grassland but dicyandiamide produces deleterious effects in clover; Macadam XM et al.; The application of nitrogen fertilisers leads to different ecological problems such as nitrate leaching and the release of nitrogenous gases . N2O is a gas involved in global warming, therefore, agricultural soils can be regarded as a source of global warming . Soil N2O production comes from both the nitrification and denitrification processes . From an ecological viewpoint, using nitrification inhibitors with ammonium based fertilisers may be a potential management strategy to lower the fluxes of N2O, thus decreasing its undesirable effect . In this study, the nitrification inhibitors (NIs) dicyandiamide (DCD) and 3,4-dimethyl pyrazole phosphate (DMPP) have been evaluated as management tools to mitigate N2O emissions from mineral fertilisation and slurry application in grassland systems (experiments 1 and 2), and to assess the phytotoxic effect of these inhibitors per se on clover (experiment 3) . Both nitrification inhibitors acted in maintaining soil nitrogen (N) in ammonium form, decreasing cumulative N2O emissions . DCD, but not DMPP, produced phytotoxic effects and yield reduction in white clover . A nutrient imbalance, which led to a senescence process visually observed as chlorosis and necrosis at the border of the leaves, was noted.

Biotechnol Bioeng, 2004 Jan 5, 85(1), 86 - 95
Analysis of size distribution and areal cell density of ammonia-oxidizing bacterial microcolonies in relation to substrate microprofiles in biofilms; Okabe S et al.; A fine-scale in situ spatial organization of ammonia-oxidizing bacteria (AOB) in biofilms was investigated by combining molecular techniques (i.e., fluorescence in situ hybridization (FISH) and 16S rDNA-cloning analysis) and microelectrode measurements . Important parameters of AOB microcolonies such as size distribution and areal cell density of the microcolonies were determined and correlated with substrate microprofiles in the biofilms . In situ hybridization with a nested 16S rRNA-targeted oligonucleotide probe set revealed two different populations of AOB, Nitrosomonas europaea-lineage and Nitrosospira multiformis-lineage, coexisting in an autotrophic nitrifying biofilm . Nitrosospira formed looser microcolonies, with an areal cell density of 0.51 cells microm(-2), which was half of the cell density of Nitrosomonas (1.12 cells microm(-2)) . It is speculated that the formation of looser microcolonies facilitates substrate diffusion into the microcolonies, which might be a survival strategy to low O(2) and NH(4) (+) conditions in the biofilm . A long-term experiment (4-week cultivation at different substrate C/N ratios) revealed that the size distribution of AOB microcolonies was strongly affected by better substrate supply due to shorter distance from the surface and the presence of organic carbon . The microcolony size was relatively constant throughout the autotrophic nitrifying biofilm, while the size increased by approximately 80% toward the depth of the biofilm cultured at the substrate C/N = 1 . A short-term ( approximately 3 h) organic carbon addition experiment showed that the addition of organic carbon created interspecies competition for O(2) between AOB and heterotrophic bacteria, which dramatically decreased the in situ NH(4) (+)-uptake activity of AOB in the surface of the biofilms . This result might explain the spatial distribution of AOB microcolony size in the biofilms cultured at the substrate C/N = 1 . These experimental results suggest O(2) and organic carbon were the main factors controlling the spatial organization and activity of AOB in biofilms . These findings are significantly important to further improve mathematical models used to describe how the slow-growing AOB develop their niches in biofilms and how that configuration affects nitrification performance in the biofilm .

Water Sci Technol, 2003, 48(8), 195 - 202
Application of a membrane bioreactor system for opto-electronic industrial wastewater treatment--a pilot study; Chen TK et al.; The membrane bioreactor (MBR) system has become more and more attractive in the field of wastewater treatment . It is particularly attractive in situations where long solids retention times are required, such as nitrifying bacteria, and physical retention is critical to achieving more efficiency for biological degradation of pollutants . Although it is a new technology, the MBR process has been applied to industrial wastewater treatment for only the past decade . The opto-electronic industry, developed very fast over the past decade in the world, is a high technological manufacturing industry . The treatment of the opto-electronic industrial wastewater containing a significant quantity of organic nitrogen compounds, with a ratio over 95% in organic nitrogen (Org-N) to total nitrogen (T-N), is very difficult to meet the discharge limits . The purpose of this research is mainly to discuss the treatment capacity of high-strength organic nitrogen wastewater, and to investigate the capabilities of the MBR process . A 2 m3/day capacity MBR pilot plant consisting of anoxic and aerobic tanks and a membrane bioreactor was installed for evaluation . The operation was continued for 130 days . Over the whole experimental period, a satisfactory organic removal performance was achieved . The COD could be removed with an average of over 94.5% . For TOC and BOD5, the average removal efficiencies were 96.3 and 97.6%, respectively . The nitrification and denitrification were also successfully achieved . The effluent did not contain any suspended solids . Only a small concentration of ammonia nitrogen was found in the effluent . The stable effluent quality and satisfactory removal performance mentioned above were ensured by the efficient interception performance of the membrane device incorporated within the biological reactor . The MBR system shows promise as a means of treating very high organic nitrogen wastewater without dilution . The effluent of TKN, NOx-N and COD can fall below 20 mg/L, 30 mg/L and 50 mg/L.

Water Sci Technol, 2003, 48(8), 143 - 50
Enrichment of nitrifying microbial communities from shrimp farms and commercial inocula; Paungfoo C et al.; Nitrifying bacteria were selected from shrimp farm water and sediment ("natural" seed) in Thailand and from commercial seed cultures . The microbial consortia from each source giving the best ammonia removal during batch culture pre-enrichments were used as inocula for two sequencing batch reactors (SBRs) . Nitrifiers were cultivated in the SBRs with 100 mg NH4-N/l and artificial wastewater containing 25 ppt salinity . The two SBRs were operated at a 7 d hydraulic retention time (HRT) for 77 d after which the HRT was reduced to 3.5 d . The amounts of ammonia removed from the influent by microorganisms sourced from the natural seed were 85% and 92% for the 7 d HRT and the 3.5 d HRT, respectively . The ammonia removals of microbial consortia from the commercial seed were 71% and 83% for these HRTs respectively . The quantity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was determined in the SBRs using the most probable number (MPN) technique . Both AOB and NOB increased in number over the long-term operation of both SBRs . According to quantitative fluorescence in situ hybridisation (FISH) probing, AOB from the natural seed and commercial seed comprised 21 +/- 2% and 30 +/- 2%, respectively of all bacteria . NOB could not be detected with currently-reported FISH probes, suggesting that novel NOB were enriched from both sources . Taken collectively, the results from this study provide an indication that the nitrifiers from shrimp farm sources are more effective at ammonia removal than those from commercial seed cultures.

Water Sci Technol, 2003, 48(8), 119 - 26
Molecular assessment of ammonia- and nitrite-oxidizing bacteria in full-scale activated sludge wastewater treatment plants; Robinson KG et al.; Nitrification was assessed in two full-scale wastewater treatment plants (WWTPs) over time using molecular methods . Both WWTPs employed a complete-mix suspended growth, aerobic activated sludge process (with biomass recycle) for combined carbon and nitrogen treatment . However, one facility treated primarily municipal wastewater while the other only industrial wastewater . Real time PCR assays were developed to determine copy numbers for total 16S rDNA (a measure of biomass content), the amoA gene (a measure of ammonia-oxidizers), and the Nitrospira 16S rDNA gene (a measure of nitrite-oxidizers) in mixed liquor samples . In both the municipal and industrial WWTP samples, total 16S rDNA values were approximately 2-9 x 10(13) copies/L and Nitrospira 16S rDNA values were 2-4 x 10(10) copies/L . amoA gene concentrations averaged 1.73 x 10(9) copies/L (municipal) and 1.06 x 10(10) copies/L (industrial), however, assays for two distinct ammonia oxidizing bacteria were required.

Water Sci Technol, 2003, 48(8), 103 - 10
Membrane bioreactors for final treatment of wastewater; Galil NI et al.; The full-scale existing treatment plant in a paper mill in Hedera, Israel, includes equalization, solids separation by either straining or by dissolved air flotation and biological treatment by activated sludge . The operation of the existing biological process is often characterized by disturbances, mainly bad settling, voluminous bioflocs, followed by wash-out of the biosolids . This paper summarizes the results obtained in a study based on a pilot plant including a membrane biological reactor (MBR) compared to the "conventional" activated sludge process in the aerobic treatment of the effluent obtained from an anaerobic reactor . During the pilot operation period (about 90 days after achieving steady state) the MBR system provided steady operation performance, while the activated sludge produced effluent characterized by oscillatory values . The results are based on average values and indicate much lower levels of suspended solids in the MBR effluent, 2.5 mg/L, as compared to 37 mg/L in the activated sludge . As a result, the total organic mater content was also substantially lower in the MBR effluent, 129 vs 204 mg/L as COD, and 7.1 vs 83 mg/L as BOD . The MBR enabled better nitrification . The ability to develop and maintain a concentration of over 11,000 mg/L of mixed liquor volatile suspended solids in the MBR bioreactor enabled an intensive bioprocess at relatively high cell residence time . As a result the biosolids which had to be removed as excess sludge were characterized by relatively low volatile/total suspended solids ratio, around 0.78 . This could facilitate and lower the cost of biosolids treatment and handling . The results of this comparative study indicate that in the case of MBR there will be no need for further treatment, while after activated sludge additional filtration will be required . The study leads to the conclusion that MBR will be the best technology for aerobic treatment of the anaerobic effluent of the paper mill.

Water Sci Technol, 2003, 48(8), 35 - 41
Long term effects of temperature and substrate level on BNR with an external nitrification reactor; Ha JS et al.; This study was conducted with a BNR (biological nutrient removal) process with an external nitrification and switching arrangement of anoxic and oxic stages . It was observed that the SPRR (specific phosphorus release rate) and SDNR (specific denitrification rate) were greatly affected by the organic loads, and SDNR had a higher temperature effect than other kinetic rates including nitrification . It was further observed that the stoichiometric values like PHA (poly hydroxyalkanoate) stored for P release and PHA consumed for P uptake also varied . Variations of % Px (phosphorus content) and PHA as intracellular matter suggest the PAOs were more active at lower temperatures with this process configuration, where more than 70% of NH4-N and phosphorus were removed at temperatures below 10 degrees.

Water Sci Technol, 2003, 48(8), 27 - 34
Biological nitrification and denitrification of opto-electronic industrial wastewater; Chen TK et al.; Development and application of biological nutrient removal processes accelerated significantly over the past decade due to more stringent nutrients (nitrogen and phosphorus) discharge limits being imposed on wastewater treatment plants . The opto-electronic industry has developed very fast over the past decade in the world . The wastewater often contains a significant quantity of organic nitrogen compounds and has a ratio of over 95% in organic nitrogen (Org-N) to total nitrogen (T-N) . In this study, a 2-stage Anoxic/Aerobic pre-denitrification process was established and the efficiency of wastewater treatment was evaluated . Wastewater from an actual LCD-plant was obtained as the sample for looking into the feasibility of opto-electronic industrial wastewater treatment . Hydraulic retention time (HRT) and mixed liquor recycle rate (MLR) were controlled independently to distinguish between the effects of these two factors . Under suitable HRT and mixed liquor recycle ratio, effluents of NH4-N, NOx-N and COD can fall below 20 mg/l, 30 mg/l and 80 mg/l.

Water Sci Technol, 2003, 48(8), 19 - 26
Advanced nitrogen elimination by encapsulated nitrifiers; Sievers M et al.; By introducing a mixed population of nitrifiers encapsulated in gel lens beads a more selective nitrification process was found in treatment of settled sewage in lab scale at a hydraulic retention time (HRT) of about 30 to 60 minutes . The reaction rates for oxidation of soluble chemical oxygen demand (SCOD) were found to vary between 25 to 150 mg/L x h while nitrification takes place around 50 mg nitrogen per hour and litre reaction volume . However, based on this SCOD removal in the nitrification step, a consequent post-denitrification process without nitrate recycle and dosage of external carbon sources has been proven to reach substantial nitrate elimination of up to 20 mg nitrogen per litre at COD/N-ratios of approx . 6 in settled sewage . At such COD/N-ratios, suitable nitrogen elimination seems to be possible, because the bioflocs of settled sewage, produced so far by SCOD oxidation and entrapment of particulate COD, are passing through the nitrification process having a substantial contribution to the denitrification rate additionally to the remaining SCOD.

Water Res, 2004 Jan, 38(2), 475 - 85
A comparative study of Cyperus papyrus and Miscanthidium violaceum-based constructed wetlands for wastewater treatment in a tropical climate; Kyambadde J et al.; The treatment efficiencies of constructed wetlands containing Cyperus papyrus L . (papyrus) and Miscanthidium violaceum (K . Schum.) Robyns (synonymous with Miscanthus violaceum (K . Schum) Pilg.) were investigated in a tropical climate (Kampala, Uganda) . Papyrus showed higher ammonium-nitrogen and total reactive phosphorus (TRP) removal (75.3% and 83.2%) than Miscanthidium (61.5% and 48.4%) and unplanted controls (27.9% ammonium-nitrogen) . No TRP removal was detected in control effluent . Nutrients (N and P) were significantly higher (p<0.015) in papyrus than Miscanthidium plant tissues . Plant uptake and storage was the major factor responsible for N and P removal in treatment line 2 (papyrus) where it contributed 69.5% N and 88.8% P of the total N and P removed . It however accounted for only 15.8% N and 30.7% P of the total N and P removed by treatment line 3 (Miscanthidium violaceum) . In addition, papyrus exhibited a significantly larger (p=0.000) number of adventitious roots than Miscanthidium . Nitrifying bacteria attached to papyrus (2.15 x 10(6)+/-1.53 x 10(5) MPN/g DW) and Miscanthidium roots (1.30 x 10(4)+/-8.83 x 10(2) MPN/g DW) and the corresponding nitrification activities were consistent with this finding . Epiphytic nitrifiers appeared more important for total nitrification than those in peat or suspended in water . Papyrus root structures provided more microbial attachment sites, sufficient wastewater residence time, trapping and settlement of suspended particles, surface area for pollutant adsorption, uptake, assimilation in plant tissues and oxygen for organic and inorganic matter oxidation in the rhizosphere, accounting for its high treatment efficiency.

Water Res, 2004 Jan, 38(2), 347 - 54
Enhanced ammonia nitrogen removal using consistent biological regeneration and ammonium exchange of zeolite in modified SBR process; Jung JY et al.; The modified zeo-SBR is recommended for a new nitrogen removal process that has a special function of consistent ammonium exchange and bioregeneration of zeolite-floc . Three sets of sequencing batch reactors, control, zeo-SBR, and modified zeo-SBR were tested to assess nitrogen removal efficiency . The control reactor consisted of anoxic-fill, aeration-mixing, settling, and decanting/idle phases, meaning that nitrogen removal efficiency was dependent on the decanting volume in a cycle . The zeo-SBR reactor was operated in the same way as the control reactor, except for daily addition of powdered zeolite in the SBR reactor . The operating order sequences in the zeo-SBR were changed in the modified zeo-SBR . Anoxic-fill phase was followed by aeration-mixing phase in the zeo-SBR, while aeration-mixing phase was followed by anoxic-fill phase in the modified zeo-SBR to carry NH4(+)-N over to the next operational cycle and to reduce total nitrogen concentration in the effluent . In the modified zeo-SBR, nitrification and biological regeneration occurred during the initial aeration-mixing phase, while denitrification and ammonium adsorption occurred in the following anoxic-fill phase . The changed operational sequence in the modified zeo-SBR to adapt the ammonium adsorption and biological regeneration of the zeolite-floc could enhance nitrogen removal efficiency . As a result of the continuous operation, the nitrogen removal efficiencies of the control and zeo-SBR were in 68.5-70.9%, based on the 33% of decanting volume for a cycle . The zeo-SBR showed a consistent ammonium exchange and bio-regeneration in the anoxic-fill and aeration-mixing phases, respectively . Meanwhile, the effluent total nitrogen of the modified zeo-SBR showed 50-60 mg N/L through ammonium adsorption of the zeolite-floc when the influent ammonium concentration was 315 mg N/L, indicating the T-N removal efficiency was enhanced over 10% in the same HRT and SRT conditions as those of control and zeo-SBR reactors . The ammonium adsorption capacity was found to be 6-7 mg NH4(+)-N/g FSS that is equivalent to 40 mg NH4(+)-N/L of ammonium nitrogen removal.

Water Res, 2004 Jan, 38(2), 335 - 46
Development of a biological filtration model applied for advanced treatment of sewage; Hidaka T et al.; A mathematical model of biological filtration process is developed in this paper . A biological filtration process has advantages that filtration action and biological activities are combined in a single reactor with aid of filter media . Both physical and biological functions are incorporated in this developed model to simulate both mechanisms . Backwashing is expressed by the assumption that a mean captured solids concentration is input as data, and a captured solids concentration is kept at that value during each filtration run . The developed model is applied to explain the experimental performance with biological filtration reactors, in which batch cultivation of autotrophic bacteria and continuous treatment of actual sewage are carried out . Its applicability is discussed by comparing the simulated results with the experimental data . This model can favourably estimate maximum accumulation of autotrophic bacteria on the medium in batch cultivation, long-term treatment performance in continuous treatment, details of water quality profiles through the filter bed, and biomass . Required hydraulic retention time for nitrification and an appropriate recirculation ratio in a winter season are discussed with this model . This model predicts that a HRT of 1.1 h or above is required to achieve nitrification with remaining NH4(+)-N of less than 1 mgN/L and that an appropriate recirculation ratio is 2-3.

J Environ Qual, 2003 Nov-Dec, 32(6), 2436 - 43
Nitrification and denitrification rates of Everglades wetland soils along a phosphorus-impacted gradient; White JR et al.; Little information is available on the effect of phosphorus (P) enrichment on nitrogen (N) biogeochemical cycling in wetland soil . Of particular importance are the coupled nitrification-denitrification reactions that regulate the microbially mediated loss of N from wetland systems . Soils from the northern Florida Everglades have been affected by P loading from surface waters over the past 40 years . Elevated P levels have been show to have an effect on the size and activity of the microbial pool and a decrease in the N to P ratio of the microbial biomass . The objective of the study was to determine if P enrichment in soils affected microbial activities related to nitrification and denitrification in these flooded, peat soils . Potential nitrification rates of soil and detritus were determined using constantly stirred reactors under aerobic conditions while denitrification rates were determined from anaerobic incubations of slurry . Nitrification rates showed two distinct linear phases, a slower initial rate, signifying activity of nitrifiers present, followed by a sharp increase in the NH4+ conversion rate indicative of maximum potential rates . Initial rates of nitrification were highest in the surficial detrital layer decreasing with soil depth and did not correlate to soil total P . The potential rates of nitrification were 13 times greater than the initial rates . Potential denitrification rates were highest in the detritus and 0- to 10-cm soil interval with significantly lower values in the 10- to 30-cm soil interval, significantly correlated to total P of the soil . A significant (P < 0.01) relationship was seen between potential denitrification rates and soil total P suggesting an increased rate of N removal from P-enriched regions of the northern Everglades.

J Environ Qual, 2003 Nov-Dec, 32(6), 2414 - 20
Potential nitrification and denitrification on different surfaces in a constructed treatment wetland; Kallner Bastviken S et al.; Improved understanding of the importance of different surfaces in supporting attached nitrifying and denitrifying bacteria is essential if we are to optimize the N removal capacity of treatment wetlands . The aim of this study was therefore to examine the nitrifying and denitrifying capacity of different surfaces in a constructed treatment wetland and to assess the relative importance of these surfaces for overall N removal in the wetland . Intact sediment cores, old pine and spruce twigs, shoots of Eurasian watermilfoil (Myriophyllum spicatum L.), and filamentous macro-algae were collected in July and November 1999 in two basins of the wetland system . One of the basins had been constructed on land that contained lots of wood debris, particularly twigs of coniferous trees . Potential nitrification was measured using the isotope-dilution technique, and potential denitrification was determined using the acetylene-inhibition technique in laboratory microcosm incubations . Nitrification rates were highest on the twigs . These rates were three and 100 times higher than in the sediment and on Eurasian watermilfoil, respectively . Potential denitrification rates were highest in the sediment . These rates were three times higher than on the twigs and 40 times higher than on Eurasian watermilfoil . The distribution of denitrifying bacteria was most likely due to the availability of organic material, with higher denitrification rates in the sediment than on surfaces in the water column . Our results indicate that denitrification, and particularly nitrification, in treatment wetlands could be significantly increased by addition of surfaces such as twigs.

Ann Chim, 2003 Sep-Oct, 93(9-10), 791 - 5
Biohydrolysis of urea from urea-bearing wastewater; Pathe PP et al.; Biological stabilization of urea is a two staged process; (i) urea hydrolysis and (ii) ammonia stripping/nitrification-denitrification . Ammonia thus produced is either stripped off by usual methods or after converting into nitrate using chemoautotrophic bacteria . On denitrification, nitrate is finally converted into nitrogen gas by means of heterotrophic bacteria . Details of stabilization of urea from urea bearing wastewater using urea biohydrolyser are presented in this paper.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(12), 2933 - 42
Using oxidation-reduction potential (ORP) and pH value for process control of shortcut nitrification-denitrification; Gao DW et al.; A new low cost technology for simultaneous carbon-nitrogen removal from soybean wastewater has been developed in this study . The technology is performed through shortcut nitrification-denitrification . The process operated under realtime control of aeration and mixing time . The shortcut nitrification-denitrification in sequencing batch reactor (SBR) was achieved efficiently and steadily by controlling temperature (28 +/- 0.5 degrees C) and using real-time control strategies . This enabled the prevention of nitrite oxidation, leading to lower operational costs . The feasibility of oxidation-reduction potential (ORP) and pH value as control parameter for shortcut nitrification-denitrification process was also investigated . Results showed that the average removal efficiency of ammonium was more than 95%, and nitrosation rate (NO2(-)-N/NOx(-)-N) was reached to 96% . At the same time, the variation of oxidation--reduction potential (ORP) and pH value was well related to organic matter degradation and ammonium oxidation in SBR . So that judgment on the ending of nitrification and denitrification can be based on the inflection point on the varied curve of ORP and pH throughout each SBR processing cycle, and thus reducing aeration and mixing time for saving energy source . The method saves organic energy up to 40% of chemical oxygen demand (COD) in denitrification process, which should reduce the need for an extra external source of organic carbon . Shorter hydraulic retention time should allow the volume of the reactors to diminish, and thus diminish investment costs . Lower oxygen demand of about 25% gives lower exploitation costs.

Environ Technol, 2003 Oct, 24(10), 1283 - 90
Performance evaluation of leachate treatment system using innovative sulfur circulation method; Kim SK et al.; A pilot-scale experimental study was carried out to evaluate the performance of an innovative method for early stabilization of landfill . This method employs sequential processes of: leachate collection; nitrification through aeration; sulfate addition in effluent tank; and leachate injection back to the landfill . This study focused on: 1) decomposition of recalcitrant organic matters, 2) the characteristics of denitrification, 3) sulfide oxidation for sulfate recovery, and 4) nitrification by aerating discharged leachate . It was found that, when sulfate (SO4(2-)) added leachate was introduced inside the landfill, sulfate-reducing bacteria decomposed recalcitrant organic matters like lignocellulose by using SO4(2-) as an electron acceptor and simultaneously sulfur-oxidizing bacteria denitrified the leachate using sulfides (H2S, HS-, S2-) as electron donors . These two types of bacteria existed not competitively but symbiotically on substrate utilization . Sulfate-reducing bacteria produced S2- while sulfur-oxidizing bacteria oxidized S2- to SO4(2-) . During aeration, the concentration of NO3(-)-N increased from near zero up to 925 mg l(-1) . Eventual denitrification efficiency in the simulated waste landfill was observed to be approximately 92.3% . Also, S2- present in the discharged leachate was converted to SO4(2-) again in the aeration process . Sulfate needed in this process could be recirculated . Therefore, the amount of sulfate required in the operation of this method could be maintained marginal after the initial addition of sulfate in the effluent tank . Decomposition of recalcitrant organic matters and denitrification hastened the stabilization of landfill . The results of this study indicated that this innovative method was effective and economic.

Plant Soil, 2003 Oct, 256(2), 371 - 8
Nitrification in a zeoponic substrate; McGilloway RL et al.; Clinoptilolite is a zeolite mineral with high cation exchange capacity used in zeoponic substrates that have been proposed as a solid medium for growing plants or as a fertilizer material . The kinetics of nitrification has not been measured for NH4+ saturated zeoponic substrate . Experiments were conducted to evaluate the production of NO2- and NO3-, and nitrifier populations in zeoponic substrates . Small columns were filled with zeoponic substrate inoculated with a commercial inoculum or soil enrichment culture of nitrifying bacteria . In addition to column studies, a growth chamber study was conducted to evaluate the kinetics of nitrification in zeoponic substrates used to grow radishes (Raphanus sativus L.) . The zeoponic substrate provided a readily available source of NH4+, and nitrifying bacteria were active in the substrate . Ammonium oxidation rates in column studies ranged from 5 to 10 micrograms N g-1 substrate h-1, and NO2- oxidation rates were 2 to 9.5 micrograms N g-1 substrate h-1 . Rates determined from the growth chamber study were approximately 1.2 micrograms N g-1 substrate h-1 . Quantities of NH4+ oxidized to NO2- and NO3- in inoculated zeoponic substrate were in excess of plant up-take . Acidification as a result of NH4+ oxidation resulted in a pH decline, and the zeoponic substrate showed limited buffering capacity.

Appl Environ Microbiol, 2003 Dec, 69(12), 7091 - 100
Nitrification and nitrifying bacteria in the lower Seine River and estuary (France); Cebron A et al.; The Acheres wastewater treatment plant, located just downstream of Paris, discharges its effluents into the lower Seine River . The effluents contain large numbers of heterotrophic bacteria, organic matter, and ammonium and are a source of nitrifying bacteria . As a result, degradation of organic matter by heterotrophic bacteria and subsequent oxygen depletion occur immediately downstream of the effluent outlet, whereas nitrifying bacteria apparently need to build up a significant biomass before ammonium oxidation significantly depletes the oxygen . We quantified the potential total nitrifying activity and the potential activities of the ammonia- and nitrite-oxidizing communities along the Seine River . In the summer, the maximum nitrifying activity occurs in the upper freshwater estuary, approximately 200 km downstream of Acheres . The quantities of nitrifying bacteria, based on amoA gene copy numbers, and of Nitrobacter organisms, based on 16S rRNA gene copy numbers, were correlated with the potential nitrifying activities . The species composition of ammonia-oxidizing bacteria was investigated at two sites: the Triel station just downstream from Acheres (km 84) and the Seine freshwater estuary at the Duclair station (km 278) . By means of PCR primers targeting the amoA gene, a gene library was created . Phylogenetic analysis revealed that the majority of the analyzed clones at both sites were affiliated with the genus NITROSOMONAS: The Nitrosomonas oligotropha- and Nitrosomonas urea-related clones represented nearly 81% of the community of ammonia-oxidizing bacteria at Triel and 60% at Duclair . Two other ammonia-oxidizing clusters of the beta subclass of the Proteobacteria, i.e., Nitrosomonas europaea- and Nitrosospira-like bacteria, were found in smaller numbers . The major change in the ammonia-oxidizing community between the two stations along the Seine River-upper estuary continuum was the replacement of the N . oligotropha- and N . urea-related bacteria by the Nitrosospira-affiliated bacteria . Although the diversities of the ammonia oxidizers appear to be similar for the two sites, only half of the restriction patterns are common to both sites, which could be explained by the differences in ammonium concentrations, which are much lower in the upper estuary than in the river at the effluent outlet . These results imply a significant immigration and/or selection of the ammonia-oxidizing bacterial population along the continuum of the Seine River from Paris to the estuary.

Environ Microbiol, 2003 Nov, 5(11), 1155 - 67
Linking autotrophic activity in environmental samples with specific bacterial taxa by detection of 13C-labelled fatty acids; Knief C et al.; A method for the detection of physiologically active autotrophic bacteria in complex microbial communities was developed based on labelling with the stable isotope 13C . Labelling of autotrophic nitrifying, sulphur-oxidizing and iron-oxidizing populations was performed in situ by incubation with NaH{13C}O3 . Incorporated label into fatty acid methyl esters (FAMEs) was detected and quantified using gas chromatography-mass spectrometry in single ion monitoring mode . Before the analyses of different environmental samples, the protocol was evaluated in pure culture experiments . In different environmental samples a selective labelling of fatty acids demonstrated which microbial taxa were responsible for the respective chemolithoautotrophic activity . The most strongly labelled fatty acids of a sample from a sulphide treating biofilter from an animal rendering plant were cis-7-hexadecenoic acid (16:1 cis7) and 11-methyl hexadecanoic acid (16:0 11methyl), which are as-yet not known for any sulphide-oxidizing autotroph . The fatty acid labelling pattern of an experimental biotrickling filter sample supplied with dimethyl disulphide clearly indicated the presence and activity of sulphide-oxidizing bacteria of the genus Thiobacillus . For a third environmental sample from an acid mining lake sediment, the assignment of autotrophic activity to bacteria of the genus Leptospirillum but not to Acidithiobacillus could be made by this method, as the fatty acid patterns of these bacteria show clear differences.

Water Sci Technol, 2003, 48(6), 301 - 9
A membrane assisted hybrid bioreactor for the post treatment of an anaerobic effluent from a fish canning factory; Oyanedel V et al.; An innovative membrane assisted hybrid bioreactor was used to treat a mixture of two streams produced in a fish canning factory: a highly loaded stream that had previously been treated in an anaerobic contact reactor, and a second stream with a relatively low COD and N concentration . Experiments were carried out during two experimental stages: an aerobic stage, which is focused in the study on the aerobic oxidation of ammonia and COD and a nitrification-denitrification stage in which the study was mainly focused on the removal of nitrogen . Results of the aerobic period pointed out that it was feasible to achieve ammonia and COD removals of around 99% at OLR of 6.5 kg COD/m3 x d and NLR of 1.8 kg N-NH4+/m3 x d . Specific nitrifying activities of up to 0.78 g N-NH4+/g protein x d and 0.25 g N-NH4+/g VSS x d, were recorded for the attached and suspended biomass, respectively . Around 50-60% of the nitrifying capacity of the reactor was a result of the nitrifying capacity of the biofilm . During the nitrification-denitrification stage 76% of nitrogen removal was attained at an NLR of 0.8 kg N-NH4+/m3 x d . The biofilm nitrifying activity was not affected by the operating conditions of the system, as a result of the preferential consumption of COD by suspended biomass in the reactor . Thus, the combination of a hybrid system, with both suspended and attached biomass, and an ultrafiltration membrane module might be an alternative for treating wastewaters in compact biological systems . The intrinsic characteristics of the system made it feasible to operate at high OLR without problems related with the settling properties of the sludge or the drop in the nitrogen conversion . There were no solids in the effluent as a result of the use of the membrane filtration module.

J Biotechnol, 2003 Dec 5, 106(1), 77 - 86
A novel granular sludge sequencing batch reactor for removal of organic and nitrogen from wastewater; Yang SF et al.; Microbial granules were developed at different substrate N/COD ratios in sequencing batch reactors (SBR) . Results showed that heterotrophic, nitrifying, and denitrifying populations could peacefully co-exist in microbial granules, while increased substrate N/COD ratio led to significant shifts among three populations in granules . Enhanced activities of nitrifying and denitrifying populations were obtained in microbial granules developed at high substrate N/COD ratios, however, heterotrophic populations in granules tended to decrease with the increase of substrate N/COD ratio . It was found that dissolved oxygen (DO) concentration had a pronounced effect on the efficiency of denitrification by microbial granules, meanwhile the results also indicated that a certain mixing power would be provided to ensure mass transfer between liquid and granules during denitrification . It was demonstrated that complete organics and nitrogen removal can be achieved in single granule-based SBR with high efficiency and stable performance . This is the first study to show the capability of microbial granules in simultaneous removal of organic carbon and nitrogen from wastewater.

Sci Total Environ, 2003 Dec 30, 317(1-3), 149 - 57
Seasonal change in the level and the chemical forms of aluminum in soil solution under a Japanese cedar forest; Umemura T et al.; The level of dissolved aluminum and its chemical forms in soil solutions consecutively collected by a porous cup vacuum sampler were monitored over a period from January 2001 to December 2001 at a Japanese cedar (Cryptomeria japonica) forestry area susceptible to acid deposition to characterize current soil dynamics and to evaluate potential tree damages . Distinction and characterization of Al species with differential toxicities were performed by two complementary speciation techniques; cation-exchange HPLC with fluorometric detection using 8-hydroxyquinoline-5-sulfonic acid (HQS) and size-fractionation/inductively coupled plasma atomic emission spectrometry (ICP-AES) . The concentrations of free Al (mainly Al3+ and Al(OH)2+) and inert Al (existing as the complexed and/or colloidal forms) ranged between 0-150 microM and 10-50 microM, respectively . The concentrations of inert Al were mostly below 40 microM during an annual cycle and showed no marked seasonal variation, while free Al concentrations showed a clear tendency to increase in the spring and summer seasons (in the period from April to August) probably due to the enhanced activity of microbial nitrification and the resultant soil acidification . Major cations and anions were also regularly determined and their seasonal changes were correlated with that of the dissolved Al concentration . Correlations between total Al (mainly existing as free Al) and the related species (and environmental conditions) were as follows: Al and Mg (R=0.96, P<0.01), Al and Ca (R=0.97, P<0.01), Al and NO3- (R=0.68, P<0.01), Al and temperature (R=0.68, P<0.01), Al and solution pH (R=-0.61, P<0.01), solution pH and NO3- (R=-0.65, P<0.01).

J Basic Microbiol, 2003, 43(6), 483 - 98
Increased solubility of (heavy) metals in soil during microbial transformations of sucrose and casein amendments; Gramss G et al.; Unsterile soil samples pH 6.8 were amended with 10% sucrose or 0.1% NH4NO3/2% casein to influence solubility of metal cations . Microbial formation of aliphatic carboxylic acids reduced pH of sucrose soil to 4.3 and increased the solubility of heavy metals by 60-fold due to the increased presence of H+, and the metal-chelating and humic-molecule fragmenting properties of carboxylic acids . Soil pH increased finally to 7.8 upon the degradation of the carboxylic acids . In casein soil, ammonia production increased pH initially to 8.5 and promoted solubility of metal-containing humic compounds . Subsequent nitrification reduced pH to 5.6 to increase concentations of Ca and Mg in the soil solution, which prevented a comparable increase in the solubility of heavy metals competitively . It is concluded that amendment with sugar and nitrogen occasionally increases the concentrations of (hazardous) elements in the soil solution to facilitate their uptake by metal hyperaccumulating plants.

Appl Microbiol Biotechnol, 2004 Feb, 63(6), 715 - 21 Epub 2003 Nov 18.
Use of the ammonia-oxidizing bacterial-specific phylogenetic probe Nso1225 as a primer for fingerprint analysis of ammonia-oxidizer communities; Calvo L et al.; Autotrophic ammonia-oxidizing bacteria (AOB) are an essential component of nitrifying wastewater treatment systems . The molecular tools used in group-specific studies are mostly based on the sequence of the 16S rRNA gene, but they have not proved to be fully specific . In this study, the sequence of the FISH probe Nso1225R was used as a reverse primer in order to analyze the AOB composition of several environmental samples by denaturing gradient gel electrophoresis (DGGE) . For this purpose, samples from several environments, including aerated reactors, water treatment wetlands, and pilot plants, both aerobic and anaerobic, were analyzed . PCR fragments displayed a DGGE pattern consisting of bands melting between 30 and 40% denaturant, and a series of unresolved bands above 45%, mostly corresponding to AOB and beta-non-AOB, respectively . This second set of bands corresponded to environments subjected to severe oxygen restrictions . AOB sequences showed similarity percentages higher than 92% with those of known beta-AOB . Nso1225R, therefore, proved to be a good molecular phylogenetic marker for AOB samples from well-aerated systems, showing a higher specificity than the group-specific primers used previously.

Water Sci Technol, 2003, 48(5), 191 - 8
Oxygen flux implications of observed nitrogen removal rates in subsurface-flow treatment wetlands; Tanner CC et al.; Nitrification, an oxygen-requiring microbial process, is generally considered the rate-limiting step for N removal in subsurface-flow constructed wetlands treating organic wastewaters . We used a simplified model of sequential N transformations and sinks to infer required rates of oxygen supply at 5 stages along experimental wetland mesocosms supplied with four different organic wastewaters with contrasting ratios of COD: N and forms of N . Mass balances of water-borne organic, ammoniacal and nitrate N, and plant and sediment N uptake showed average net rates of N mineralisation ranging from 0.22-0.53 g m(-2) d(-1), nitrification 0.56-2.15 g m(-2) d(-1), denitrification 0.47-1.99 g m(-2) d(-1) (60-84% of measured N removal) and plant assimilation 0.28-0.47 g m(-2) d(-1) . The nitrogenous oxygen demand (NOD) required to support the observed nitrification rates alone was high compared to expected fluxes from surficial and plant-mediated oxygen transfer . In the presence of high levels of degradable organic matter (COD removal rates up to 66 g m(-2) d(-1)), heterotrophs with significantly higher oxygen affinities and energy yields are expected to outcompete nitrifiers for available oxygen . Problems with commonly held assumptions on the nature of coupled nitrification-denitrification in treatment wetlands are discussed.

Water Sci Technol, 2003, 48(5), 175 - 82
Nitrogen removal from domestic effluent using subsurface flow constructed wetlands: influence of depth, hydraulic residence time and pre-nitrification; Bayley ML et al.; This paper describes two studies into the BOD and TN removal performance of horizontal subsurface flow wetlands (reed beds) in subtropical Australia . The aim of the first study was to determine the influence of HRT and vertical position on BOD and TN concentration and removal performance in a 0.5 m deep reed bed (System 1) by taking samples from three levels (or layers) in the water column at five points along the length of the bed . The aim of the second study was to investigate the TN removal performance of a treatment train consisting of a vertical flow intermittently dosed sand filter preceding a reed bed (System 2) . Both systems were dosed with primary settled municipal wastewater (BOD 194 mg L(-1); TN 49 mg L(-1)) . System 1 achieved a TN load removal of 58% under a HLR of 22 mm day(-1) (HRT 10.5 days), producing effluent BOD concentrations consistently less than 8 mg L(-1) . There was no significant difference in BOD attenuation rate between the three layers . While there were differences in both the nitrification and denitrification rates between the three layers, the TN concentration was found to decline steadily in all layers up to an HRT of 8.7 days . System 2 reduced TN influent load by 33%, less than half of which was removed by the reed bed . The lack of substantial TN removal within this reed bed was attributed to the low concentrations of BOD and consequent lack of dissolved organic carbon to drive the denitrification process.

Water Sci Technol, 2003, 48(5), 167 - 74
Controlling a combined lagoon/reed bed system using the oxidation-reduction potential (ORP); Kayser K et al.; Lagoon systems achieve good and stable effluent data in regard to organic pollutants, but they charge the receiving waters with relatively high ammonium loads . Therefore an existing lagoon-plant was extended by a vertical flow reed-bed for the special purpose of nitrification . This paper presents the efficiency of the combination plant as well as the possibility to monitor and control the reed-bed operation by the oxidation-reduction potential (ORP) . The results show that the combination plant achieved excellent purification results, the average efficiency degrees were 97% for COD, 77% for N(total) and 94% for the TKN elimination . The ORP in the effluent of the reed bed showed a clear dependence in its characteristic course and its absolute values on the current nitrification performance, the oxygen supply and the hydraulic behaviour of the reed bed . Therefore the ORP is a very good indicator for the state of the reed bed, which ultimately results from the accumulation of a large number of different influencing parameters . As the preservation of aerobic conditions in the reed bed is the crucial prerequisite for a high nitrification performance and for the avoidance of clogging, the ORP thus offers the possibility of immediate operation control.

Water Sci Technol, 2003, 48(5), 135 - 42
Nitrous oxide, dinitrogen and methane emission in a subsurface flow constructed wetland; Mander U et al.; N2O, N2 and CH4 fluxes were measured from a horizontal subsurface flow (HSSF) constructed wetland (CW) for wastewater treatment in Estonia . The closed chamber method was used in the field and the He-O method (intact soil core analyses) in the lab throughout the period from October 2001 to June 2002 . The average flux of N2O-N, N2-N and CH4-C from various microsites ranged from 0.1 to 59, 4.1 to 1,458 and -0.04 to 2,094 mg m(-2) d(-1), respectively . A significantly higher flux of N2O was found in chambers installed above the inlet pipes, while the methane flux was higher in the inlet part of the bed with wetter conditions . The groundwater table significantly correlates with gas emission rates of all the gases studied; N2 emission was enhanced by higher temperature of wastewater . PO4(3-) and NH4+ content significantly enhanced, and NO2- and NO3- content inhibited, both N2O and CH4 fluxes . NH4+ showed a negative correlation with N2 flux . Nitrification and denitrification are the main processes of the N removal in the CW covering 42.9% . The specific global warming potential was highest in the wet bed and lowest in the dry bed with lowered water table (32 and 9 g CO2 pe(-1) d(-1), respectively).

Mikrobiol Z, 2003 Jul-Aug, 65(4), 37 - 42
{The effect of bacterium inoculation on the yield of pure and mixed corn with soya on leached chernozems}; Rybak VK; The use of biopreparations resulted in the increase of green mass within 64-126 c/ha when field experiments were carried out with joint and mixed crops of corn with soya in conditions of the Polyssya leached chernozems . An advantage of 8-23 c/ha was achieved when growing their mixtures . The average crop of green mass for the years of investigations was within 530-894 c/ha . Bacterial fertilizers and soya activate microbiological process of nitrogen cycle, increasing the number of nitrifiers and denitrifiers in the rhizosphere of plants . Thus these factors improve the nitrogen nutrition of cultures in the mixed crops . There is an interaction between plants of corn-soya phytocenosis which has the metabolic-competition character that guarantees better employment of biopreparations and fertilizers, genetic properties of plants and natural resources.

J Bacteriol, 2003 Dec, 185(23), 6809 - 14
Chemolithoorganotrophic growth of Nitrosomonas europaea on fructose; Hommes NG et al.; The nitrifying bacterium Nitrosomonas europaea can obtain all its carbon for growth from CO(2) and all its energy and reductant for growth from the oxidation of NH(3) and is considered an obligate chemolithoautotroph . Previous studies have shown that N . europaea can utilize limited amounts of certain organic compounds, including amino acids, pyruvate, and acetate, although no organic compound has been reported to support the growth of N . europaea . The recently completed genomic sequence of N . europaea revealed a potential permease for fructose . With this in mind, we tested if N . europaea could utilize fructose and other compounds as carbon sources to support growth . Cultures were incubated in the presence of fructose or other organic compounds in sealed bottles purged of CO(2) . In these cultures, addition of either fructose or pyruvate as the sole carbon source resulted in a two- to threefold increase in optical density and protein content in 3 to 4 days . Studies with {(14)C}fructose showed that >90% of the carbon incorporated by the cells during growth was derived from fructose . Cultures containing mannose, glucose, glycerol, mannitol, citrate, or acetate showed little or no growth . N . europaea was not able to grow with fructose as an energy source, although the presence of fructose did provide an energy benefit to the cells . These results show that N . europaea can be grown in CO(2)-free medium by using fructose and pyruvate as carbon sources and may now be considered a facultative chemolithoorganotroph.

Rapid Commun Mass Spectrom, 2003, 17(22), 2550 - 6
Dual isotope and isotopomer ratios of N2O emitted from a temperate grassland soil after fertiliser application; Bol R et al.; The N2O and N2 fluxes emitted from a temperate UK grassland soil after fertiliser application (equivalent to 25 and 75 kg N ha(-1)) were simultaneously measured, using a new automated soil incubation system, which replaces soil atmosphere (N2 dominated) with a He+O2 mixture . Dual isotope and isotopomer ratios of the emitted N2O were also determined . Total N2O and N2 fluxes were significantly lower (P<0.001) in the control (0 kg N) than in the 25 and 75 kg N treatments . The total N2O flux was significantly higher (P<0.001) in the 75 kg N than in the 25 kg N treatment . The general patterns of N2O and N2 fluxes were similar for both fertiliser treatments . The total gaseous N loss in the control treatment was nearly all N2, whereas in the fertiliser treatment more N2O than N2 was emitted from the soil . The ratio N2O/N2 fluxes as measured during the experiment suggested three phases in N2O production, in phase 1 nitrification>denitrification, in phase 2 denitrification>nitrification, and in phase 3 denitrification (and total denitrification)>>nitrification . Dual delta15N and delta18O isotope and isotopomer (delta15Nalpha and delta15Nbeta) value ratios of emitted N2O also pointed towards an increasing dominance of the production of N2O by denitrification and total denitrification . The site preference value from the soil-emitted N2O was lower than the troposphere value . This confirmed that the enhanced troposphere N2O site preference could result from back injection of N2O from the stratosphere . The measurements of N2O/N2 flux ratio and the isotopic content of emitted N2O pointed, independently, to similar temporal trends in N2O production processes after fertiliser application to grassland soil . This confirmed that both measurements are suitable diagnostic tools to study the N2O production process in soils .

Water Res, 2003 Dec, 37(20), 4965 - 73
Characterization of nitrifying granules produced in an aerobic upflow fluidized bed reactor; Tsuneda S et al.; Since nitrification is the rate-determining step in the biological nitrogen removal from wastewater, many research studies have been conducted on the immobilization of nitrifying bacteria . In this research, granulation of nitrifying bacteria in an aerobic upflow fluidized bed (AUFB) reactor in a nitrification process for inorganic wastewater containing 500 g/m(3) of NH(4)(+)-N was investigated . It was observed that spherical, pseudocubic and elliptical granules with a diameter of 346 microm were produced at the bottom of the reactor after 300 days . Denaturing gradient gel electrophoresis analysis revealed that Nitrosomonas-like bacteria were the dominant ammonia-oxidizing species in the granules . Many colonies of Nitrosomonas-like bacteria were found in the outer part of the granules based on the spatial distribution analysis by fluorescence in situ hybridization . By stepwise reduction of the hydraulic retention time, the ammonia removal rate of the AUFB reactor containing these nitrifying granules finally reached 1.5 kg-N/m(3)/day . Results suggested that the use of granules realizes the retention of a large amount of nitrifying bacteria in the reactor, which guarantees a highly efficient nitrification.

Appl Environ Microbiol, 2003 Nov, 69(11), 6875 - 87
The isotope array, a new tool that employs substrate-mediated labeling of rRNA for determination of microbial community structure and function; Adamczyk J et al.; A new microarray method, the isotope array approach, for identifying microorganisms which consume a (14)C-labeled substrate within complex microbial communities was developed . Experiments were performed with a small microarray consisting of oligonucleotide probes targeting the 16S rRNA of ammonia-oxidizing bacteria (AOB) . Total RNA was extracted from a pure culture of Nitrosomonas eutropha grown in the presence of {(14)C}bicarbonate . After fluorescence labeling of the RNA and microarray hybridization, scanning of all probe spots for fluorescence and radioactivity revealed that specific signals were obtained and that the incorporation of (14)C into rRNA could be detected unambiguously . Subsequently, we were able to demonstrate the suitability of the isotope array approach for monitoring community composition and CO(2) fixation activity of AOB in two nitrifying activated-sludge samples which were incubated with {(14)C}bicarbonate for up to 26 h . AOB community structure in the activated-sludge samples, as predicted by the microarray hybridization pattern, was confirmed by quantitative fluorescence in situ hybridization (FISH) and comparative amoA sequence analyses . CO(2) fixation activities of the AOB populations within the complex activated-sludge communities were detectable on the microarray by (14)C incorporation and were confirmed independently by combining FISH and microautoradiography . AOB rRNA from activated sludge incubated with radioactive bicarbonate in the presence of allylthiourea as an inhibitor of AOB activity showed no incorporation of (14)C and thus was not detectable on the radioactivity scans of the microarray . These results suggest that the isotope array can be used in a PCR-independent manner to exploit the high parallelism and discriminatory power of microarrays for the direct identification of microorganisms which consume a specific substrate in the environment.

Water Environ Res, 2003 Sep-Oct, 75(5), 422 - 33
Pilot-scale evaluation of separate-stage nitrification using an attached-growth, moving-bed media process; Zimmerman RA et al.; Submerged attached-growth processes, both fixed and moving bed, are becoming more popular . These processes may or may not be used in combination with suspended-growth treatment . The objective of this project was to evaluate a tertiary attached-growth, moving-bed media nitrification system based on the ammonia-nitrogen removal rates and effluent concentrations that could be achieved . A pilot-scale system for nitrification of secondary municipal wastewater effluent was operated for 142 days . The minimum aeration requirements for media mixing provided sufficient dissolved oxygen . The generation of biological solids from nitrification was insignificant . Design effluent ammonia-nitrogen concentrations (<6 mg/L) were achieved at influent loading rates greater than design (1.18 g ammonia-nitrogen/{m2 x d}) coincident with detention times shorter than design conditions (4 hours) . Empirical relationships for the ammonia-nitrogen removal rate and effluent concentration as a function of influent ammonia-nitrogen loading were developed . Detention time is believed to be an important parameter affecting these relationships.

Environ Toxicol Chem, 2003 Nov, 22(11), 2592 - 8
Comparison of toxicity of zinc for soil microbial processes between laboratory-contamined and polluted field soils; Smolders E et al.; Soil microbial processes are readily disturbed by added zinc (Zn) in laboratory ecotoxicity tests . This study compares Zn toxicity between freshly spiked soils and soils that have been contaminated with Zn in the field . Soils were sampled in three transects (< 80 m) toward galvanized electricity transmission towers (pylons) . The soil total Zn concentrations gradually increased in each transect from background values (25-82 mg Zn/kg) to elevated Zn concentrations near the pylon (226-595 mg Zn/kg) . Soil samples taken at the furthest distance from the Zn source were spiked with ZnCl2 to a range of total Zn concentrations similar to those in the transect . Nitrification, respiration, and N-mineralization rates were significantly reduced by added Zn in laboratory-spiked soils and were 9 to 95% (mean 32%) of the control values at largest doses depending on soil type and the microbial process . In contrast, these processes were either unaffected by soil Zn (p > 0.05) or increased significantly with soil Zn concentrations in the transect soils . These increases could not be explained by soil pH or % soil organic carbon . Leaching soils after spiking significantly lowered the toxic effects of Zn on nitrification or on substrate-induced respiration . The soil solution Zn concentrations of field soils were always smaller than in spiked soils at equivalent total Zn . Highest soil solution Zn concentrations were always lower than the soil-solution EC50s of spiked soils . It is concluded that there is a large discrepancy in microbial responses to elevated Zn between spiked soils (unleached) and field-contaminated soils and there is a need to explain this discrepancy in terms of Zn availability, adaptation processes, and additional soil factors controlling the microbial processes.

Water Res, 2003 Nov, 37(19), 4781 - 91
Membrane bioreactor for the drinking water treatment of polluted surface water supplies; Li XY et al.; A laboratory membrane bioreactor (MBR) using a submerged polyethylene hollow-fibre membrane module with a pore size of 0.4 microm and a total surface area of 0.2 m2 was used for treating a raw water supply slightly polluted by domestic sewage . The feeding influent had a total organic carbon (TOC) level of 3-5 mg/L and an ammonia nitrogen (NH(3)-N) concentration of 3-4 mg/L . The MBR ran continuously for more than 500 days, with a hydraulic retention time (HRT) as short as 1h or less . Sufficient organic degradation and complete nitrification were achieved in the MBR effluent, which normally had a TOC of less than 2 mg/L and a NH(3)-N of lower than 0.2 mg/L . The process was also highly effective for eliminating conventional water impurities, as demonstrated by decreases in turbidity from 4.50+/-1.11 to 0.08+/-0.03 NTU, in total coliforms from 10(5)/mL to less than 5/mL and in UV(254) absorbance from 0.098+/-0.019 to 0.036+/-0.007 cm(-1) . With the MBR treatment, the 3-day trihalomethane formation potential (THMFP) was significantly reduced from 239.5+/-43.8 to 60.4+/-23.1 microg/L . The initial chlorine demand for disinfection decreased from 22.3+/-5.1 to 0.5+/-0 . 1mg/L . The biostability of the effluent improved considerably as the assimilable organic carbon (AOC) decreased from 134.5+/-52.7 to 25.3+/-19.9 microg/L . All of these water quality parameters show the superior quality of the MBR-treated water, which was comparable to or even better than the local tap water . Molecular size distribution analysis and the hydrophobic characterisation of the MBR effluent, in comparison to the filtered liquor from the bioreactor, suggest that the MBR had an enhanced filtration mechanism . A sludge layer on the membrane surface could have functioned as an additional barrier to the passage of typical THM precursors, such as large organic molecules and hydrophobic compounds . These results indicate that the MBR with a short HRT could be developed as an effective biological water treatment process to address the urgent need of many developing countries that are plagued by the serious contamination of surface water resources.

Water Res, 2003 Nov, 37(19), 4587 - 94
Comparison of ammonia volatilisation rates in algae and duckweed-based waste stabilisation ponds treating domestic wastewater; Zimmo OR et al.; Quantification of ammonia volatilisation from wastewater stabilisation ponds is important in order to understand its significance for overall nitrogen removal in these widely applied low-cost treatment systems . Ammonia volatilisation rates were measured in pilot plant facilities consisting of one line of four algae-based ponds in series and a parallel line of four ponds with a floating mat of duckweed (Lemna gibba) . Ammonia volatilisation was assessed during a period of one and a half years . The method applied is accurate, convenient and is proposed for analysis of a wide range of gasses emitted from stabilisation ponds and possibly other aquatic systems . The ammonia volatilisation rates in algae-based ponds (ABPs) were higher than in duckweed-based ponds (DBPs) . This can be explained by the lower values of NH(3) in DBPs due to shading and lower pH values, since the volatilisation rate highly correlated with free ammonia concentration (NH(3)) in pond water . The duckweed cover appeared not to provide a physical barrier for volatilisation of unionised ammonia, because whenever NH(3) concentrations were equal in ABP and DBP also the volatilisation rates were equal . Volatilisation was in the range of 7.2-37.4 mg-Nm(-2)d(-1) and 6.4 -31.5 mg-Nm(-2)d(-1) in the ABPs and DBPs, respectively . Average influent and effluent ammonium nitrogen measurements showed that the ammonia volatilisation during the study period in any system did not exceed 1.5% of total ammonium nitrogen removal . Therefore this study confirmed results from simultaneous experimental work in our laboratory indicating that nitrification/denitrification, rather than ammonia volatilisation, is the most important mechanism for N removal in ABPs and DBPs.

J Environ Sci (China), 2003 Sep, 15(5), 669 - 73
Temperature effect on aerobic denitrification and nitrification; Xie SG et al.; Nitrogen loss without organic removal in biofilter was observed and its possible reason was explained . A lower hydraulic loading could improve aerobic denitrification rate . Aerobic denitrification was seriously affected by low temperature(below 10 degrees C) . However, nitrification rate remained high when the temperature dropped from 15 degrees C to 5 degrees C . It seemed the autotrophic biofilm in BAF could alleviate the adverse effect of low temperature.

J Environ Sci (China), 2003 Sep, 15(5), 607 - 10
Inhibition of nitrification in soil by metal diethyldithiocarbamates; Arora A et al.; Nitrification acts as a key process in determining fertilizer use efficiency by crops as well as nitrogen losses from soils . Metal dithiocarbamates in addition to their pesticidal properties can also inhibit biological oxidation of ammonium(nitrification) in soil . Metal {M = V(III), Cr(III), Mn(II), Fe(III), Ni(II), Cu(II), Zn(II) and Co(II)} diethyldithiocarbamates (DEDTC) were synthesized by the reaction of sodium diethyldithiocarbamate with metal chloride in dichloromethane/water mixture . These metal diethyldithiocarbamates were screened for their ability to inhibit nitrification at different concentrations( 10 microg/g soil, 50 microg/g soil and 100 microg/g soil) . With increasing concentration of the complex, capacity to retard nitrification increased but the extent of increase varied for different metals . At 100 microg/g soil, different complexes showed nitrification inhibition from 22.36% to 46.45% . Among the diethyldithiocarbamates tested, Zn(DEDTC)2 proved to be the most effective nitrification inhibitor at 100 microg/g soil . Manganese, iron and chromium diethyldithiocarbamates also proved to be effective nitrification inhibitors than the others at 100 microg/g soil . The order of percent nitrification inhibition in soil by metal diethyldithiocarbamates was: Zn(II) > Mn(II) > Fe(III) > Cr(III) > V(III) > Co(II) > Ni(II) > Cu(II).

Huan Jing Ke Xue, 2003 Jul, 24(4), 94 - 8
{Cultivation of aerobic granular sludge for simultaneous nitrification and denitrification in SBR system}; Yang Q et al.; The cultivation of aerobic granular sludge used for nitrogen removal in Sequencing Batch Reactor (SBR) fed with a synthetic municipal wastewater was investigated . The results showed that the aerobic granular sludge with the high activity of simultaneous nitrification and denitrification, could form in the reactor by controlling the addition of carbon source, and the removal rates of COD and NH3-N reached 74.0%-92.8% and 82.3%-98.5%, respectively, in the reactor . The granular formed was averagely 0.5-1.0 mm in diameter, and the Mixed Liquid Suspended Solids (MLSS) and the Sludge Volumetric Index (SVI) in the reactor were above 4.5 g/L and above 32.5, respectively . Compared with the normal aerobic activated sludge process, the system with aerobic granular sludge had a higher concentration of effective biomass and a much stronger ability of nitrogen removal.

FEMS Microbiol Rev, 2003 Oct, 27(4), 481 - 92
New concepts of microbial treatment processes for the nitrogen removal in wastewater; Schmidt I et al.; Many countries strive to reduce the emissions of nitrogen compounds (ammonia, nitrate, NOx) to the surface waters and the atmosphere . Since mainstream domestic wastewater treatment systems are usually already overloaded with ammonia, a dedicated nitrogen removal from concentrated secondary or industrial wastewaters is often more cost-effective than the disposal of such wastes to domestic wastewater treatment . The cost-effectiveness of separate treatment has increased dramatically in the past few years, since several processes for the biological removal of ammonia from concentrated waste streams have become available . Here, we review those processes that make use of new concepts in microbiology: partial nitrification, nitrifier denitrification and anaerobic ammonia oxidation (the anammox process) . These processes target the removal of ammonia from gases, and ammonium-bicarbonate from concentrated wastewaters (i.e . sludge liquor and landfill leachate) . The review addresses the microbiology, its consequences for their application, the current status regarding application, and the future developments.

Biotechnol Adv, 2000 May, 18(3), 219 - 32
Production of nitrogen oxide and dinitrogen oxide by autotrophic nitrifiers; Colliver BB et al.; Autotrophic nitrifiers have been shown to produce nitrogen oxide and dinitrogen oxide under oxic conditions . Dinitrogen oxide is produced mainly during nitrite reduction (i.e . aerobic denitrification) whereas nitrogen oxide is produced during both aerobic denitrification and as a result of chemodenitrification . Oxygen is the single most influential environmental factor affecting the production of nitrogen and dinitrogen oxides; a decrease in oxygen can result in a several-fold increase in nitrogen oxide and dinitrogen oxide production . Emission of nitrogen oxide and dinitrogen oxide from wastewater treatment plants and fertilized soils is well documented; however, only recently have the contributions from such environments to the global nitrogen and dinitrogen oxide budget been considered.

J Environ Qual, 2003 Sep-Oct, 32(5), 1895 - 904
Particulates, not plants, dominate nitrogen processing in a septage-treating aerated pond system; Hamersley MR et al.; In pond and wetland systems for wastewater treatment, plants are often thought to enhance the removal of ammonium and nitrogen through the activities of root-associated bacteria . In this study, we examined the role of plant roots in an aerated pond system with floating plants designed to treat high-strength septage wastewater . We performed both laboratory and full-scale experiments to test the effect of different plant root to septage ratios on nitrification and denitrification, and measured the abundances of nitrifying bacteria associated with roots and septage particulates . Root-associated nitrifying bacteria did not play a significant role in ammonium and total nitrogen removal . Investigations of nitrifier populations showed that only 10% were associated with water hyacinth {Eichhornia crassipes (Mart.) Solms} roots (at standard facility plant densities equivalent to 2.2 wet g roots L(-1) septage); instead, nitrifiers were found almost entirely (90%) associated with suspended septage particulates . The role of root-associated nitrifiers in nitrification was examined in laboratory batch experiments where high plant root concentrations (7.4 wet g L(-1), representing a 38% net increase in total nitrifier populations over plant-free controls) yielded a corresponding increase (55%) in the non-substrate-limited nitrification rate (V(max)) . However, within the full-scale septage-treating pond system, nitrification and denitrification rates remained unchanged when plant root concentrations were increased to 7.1 g roots L(-1) (achieved by increasing the surface area available for plants while maintaining the same tank volume) . Under normal facility operating conditions, nitrification was limited by ammonium concentration, not nitrifier availability . Maximizing plant root concentrations was found to be an inefficient mechanism for increasing nitrification in organic particulate-rich wastewaters such as septage.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(11), 2633 - 41
Anaerobic-aerobic sewage treatment using the combination UASB-SBR activated sludge; Guimaraes P et al.; The performance of a pilot scale sewage treatment system composed of an upflow anaerobic sludge blanket (UASB) digester and a sequencing batch activated sludge reactor (SBR) is described . The system constitutes a simple, economic, and compact treatment option and is able to produce consistently a final effluent quality that is equal or better than that of a conventional activated sludge plant . The entire treatment system had a retention time of only 9h and an average operational temperature of 25 degrees C . Due to the efficient anaerobic pre treatment the aerobic sludge production was low and could easily be accommodated for stabilisation in the UASB reactor . The system exhibited excellent operational stability with full nitrification for aerobic sludge ages longer than 9 days . At shorter sludge ages there was excessive wash out of sludge particles and the sludge mass could not be maintained in the SBR reactor . Sludge settleability was good throughout the experimental investigation period of one year . The reduction of the reactor volume and oxygen consumption was more than 50% compared to conventional activated sludge . The anaerobic excess sludge had a high concentration and good stability so that its dewatering and final disposal was a relatively minor problem.

Appl Environ Microbiol, 2003 Oct, 69(10), 5974 - 82
Community composition and functioning of denitrifying bacteria from adjacent meadow and forest soils; Rich JJ et al.; We investigated communities of denitrifying bacteria from adjacent meadow and forest soils . Our objectives were to explore spatial gradients in denitrifier communities from meadow to forest, examine whether community composition was related to ecological properties (such as vegetation type and process rates), and determine phylogenetic relationships among denitrifiers . nosZ, a key gene in the denitrification pathway for nitrous oxide reductase, served as a marker for denitrifying bacteria . Denitrifying enzyme activity (DEA) was measured as a proxy for function . Other variables, such as nitrification potential and soil C/N ratio, were also measured . Soil samples were taken along transects that spanned meadow-forest boundaries at two sites in the H . J . Andrews Experimental Forest in the Western Cascade Mountains of Oregon . Results indicated strong functional and structural community differences between the meadow and forest soils . Levels of DEA were an order of magnitude higher in the meadow soils . Denitrifying community composition was related to process rates and vegetation type as determined on the basis of multivariate analyses of nosZ terminal restriction fragment length polymorphism profiles . Denitrifier communities formed distinct groups according to vegetation type and site . Screening 225 nosZ clones yielded 47 unique denitrifying genotypes; the most dominant genotype occurred 31 times, and half the genotypes occurred once . Several dominant and less-dominant denitrifying genotypes were more characteristic of either meadow or forest soils . The majority of nosZ fragments sequenced from meadow or forest soils were most similar to nosZ from the Rhizobiaceae group in alpha-Proteobacteria species . Denitrifying community composition, as well as environmental factors, may contribute to the variability of denitrification rates in these systems.

Appl Environ Microbiol, 2003 Oct, 69(10), 5950 - 6
Comparing denitrification estimates for a Texas estuary by using acetylene inhibition and membrane inlet mass spectrometry; Bernot MJ et al.; Characterizing denitrification rates in aquatic ecosystems is essential to understanding how systems may respond to increased nutrient loading . Thus, it is important to ensure the precision and accuracy of the methods employed for measuring denitrification rates . The acetylene (C2H2) inhibition method is a simple technique for estimating denitrification . However, potential problems, such as inhibition of nitrification and incomplete inhibition of nitrous oxide reduction, may influence rate estimates . Recently, membrane inlet mass spectrometry (MIMS) has been used to measure denitrification in aquatic systems . Comparable results were obtained with MIMS and C2H2 inhibition methods when chloramphenicol was added to C2H2 inhibition assay mixtures to inhibit new synthesis of denitrifying enzymes . Dissolved-oxygen profiles indicated that surface layers of sediment cores subjected to the MIMS flowthrough incubation remained oxic whereas cores incubated using the C2H2 inhibition methods did not . Analysis of the microbial assemblages before and after incubations indicated significant changes in the sediment surface populations during the long flowthrough incubation for MIMS analysis but not during the shorter incubation used for the C2H2 inhibition method . However, bacterial community changes were also small in MIMS cores at the oxygen transition zone where denitrification occurs . The C2H2 inhibition method with chloramphenicol addition, conducted over short incubation intervals, provides a cost-effective method for estimating denitrification, and rate estimates are comparable to those obtained by the MIMS method.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2317 - 28
Upgrading of a small overloaded activated sludge plant using a MBBR system; Andreottola G et al.; The aim of this research was the application of a biofilm system for the upgrading of a full-scale overloaded activated sludge MWWTP using the MBBR (Moving Bed Biofilm Reactor) technology . The choice of this fixed biomass system appeared appropriate because it offers several advantages including good potential in nitrification process, easiness of management and above all, the possibility to use the existing tank with very few modifications . MBBR system counts only few full-scale plants in Italy at the moment, thus a pilot-scale experimentation was preliminarily carried out . The acquired parameters were used for the fullscale MWWTP upgrading . The upgrading of the activated sludge reactor in the MBBR system has given (1) a relevant increase in the flowrate treated up to 60%; (2) a good efficiency in organic carbon removal and nitrification, equal to 88% and 90% respectively, with HRTs of 5.5-7 h; (3) the overcoming of the hydraulic overload of the secondary settler, applying a lamellar settler . It was observed a good correlation between the results obtained at pilot-scale and those observed in the full-scale plant.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2179 - 89
Novel phased isolation ditch system for enhanced nutrient removal and its optimal operating strategy; Hong KH et al.; Phased isolation ditch system with intrachannel clarifier is a simplified novel oxidation ditch system enhancing simultaneous removal of biological nitrogen and phosphorus in municipal wastewater . The system employs two ditches with intra-clarifier, and eliminates external final clarifier, additional preanaerobic reactor, and recycle of sludge and nitrified effluent . Separation of anoxic, anaerobic, and aerobic phases can be accomplished by alternating flow and intermittent aeration . Its pilot-scale system operated at HRTs of 10-21 h, SRTs of 15-41 days, and a cycle times of 2-8 h showed removals of BOD, TN, and TP in the range of mixed liquor temperature above 10 degrees C as high as 88-97, 70-84, and 65-90%, respectively . As the SRTs became longer, the effluent TN decreased dramatically, whereas the effluent TP increased . Higher nitrogen removal was accomplished at shorter cycle times, while better phosphorus removal was achieved in longer cycle times . Optimal system operating strategies maximizing the performance and satisfying both the best nitrogen and phosphorus removals included HRTs ranged 10-14 h, SRTs ranged 25-30 days, and a cycle time of 4 h at the mixed liquor temperature above 10 degrees C . Thus, complete phase separation in a cycle maximizing phosphorus release and uptake as well as nitrification and denitrification was accomplished by scheduling of alternating flow and intermittent aeration in the simplified process scheme . Especially, temporal phase separation for phosphorus release without additional anaerobic reactor was successfully accomplished during anaerobic period without any nitrate interference and carbon-limiting.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2157 - 67
Nitrification-denitrification of opto-electronic industrial wastewater by anoxic/aerobic process; Chen TK et al.; This research focused on the biological treatment of high-strength organic nitrogen wastewater, and presented the results from the nitrification and denitrification of an actual industrial wastewater using anoxic/aerobic process . The opto-electronic industrial wastewater often contains a significant quantity of organic nitrogen compounds and has a ratio over 95% in organic nitrogen (Org-N) to total nitrogen (T-N) . In this study, a 2-stage anoxic/aerobic process was established and evaluated the efficiency of wastewater treatment . Raw wastewater from an actual TFT-LCD manufacturing plant was obtained as the sample for looking into the feasibility of opto-electronic industrial wastewater treatment . After toxicity identification evaluation (TIE) test of raw wastewater . the inhibition was related to organic nitrogen (TMAH, MEA) and unionized ammonia (free ammonia, NH3) with high pH . Therefore, pH control is important for biological treatment of high-strength organic nitrogen industrial wastewater . Besides . hydraulic retention time (HRT) and mixed liquor recycled rate (MLR) were controlled independently to distinguish between the effects of these two factors . Under suitable HRT ( > 1.7 d) and mixed liquor recycled rate (< 4Q), effluent of NH4-N . NO3-N + NO2-N, and COD can fall below 20 mg/L, 30 mg/L, and 80 mg/L . The anoxic/aerobic process removed 92-98% of the carbon source, and approximately 80% of TKN, 70% of T-N.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2147 - 56
Combined carbonaceous removal and nitrification with biological aerated filters; Belgiorno V et al.; This paper describes the use of a submerged biological aerated filter (BAFs), on a pilot plant scale, in the secondary nitrification of low strength domestic wastewater . The results, obtained throughout three months of tests, confirmed the ability of BAFs to obtain simultaneous carbonaceous removal and nitrification . In fact, alter a start-up period of 5 weeks, a remarkable steady state condition in the removal of suspended solids (TSS), chemical oxygen demand (COD) and nitrification was reached . For a hydraulic loading rate of 1.6 m3 m(-2) h(-1), the mean efficiency of the process in the removal of TSS and COD was 85% and 83% respectively . Mean concentrations in the influent flow of around 114 mg(TSS)/L and 140 mg(COD)/L were reduced to average values of below 17 mg(TSS)/L and 25 mg(COD)/L . Secondary nitrification was achieved with a mean efficiency of 85% for a mean volumetric loads of 0.45 kg(N-Namm) m(-3) d(-1) (25 degrees C) . Through an intensive activity of nitrification, in the steady state condition, mean influent concentrations of around 12 mg(N-Namm)/L were reduced to average values of below 2 mg(N-Namm)/L . The removal loading rate increased linearly with the applied loading rate for volumetric loads of up to 0.7 kg(N-Namm) m(-3) d(-1) . The nitrification was not sensitive to the applied COD loads because of the low level of carbon substrate.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 1997 - 2007
Molecular analysis of microbial communities in nitrification and denitrification reactors treating high ammonia leachate; Calli B et al.; Molecular analysis of microbial populations in two bench-scale nitrification and denitrification reactors fed with high ammonia landfill leachate was conducted in this study by using DGGE, cloning, and FISH techniques in addition to classical efficiency control parameters . Nitrification tank was operated with a computer-controlled alkalinity dosing system to supply the alkalinity intermittently as consumed on the basis of on-line pH monitoring . By keeping the pH at 7.0 with this system, 99% nitrification efficiency and rates of about 0.14-0.18 mgNH4+-N/mgVSSday were obtained . Meanwhile, as ammonia oxidizing bacteria Nitrosomonas and Nitrosococcus mobilis-like cells and as nitrite oxidizing bacteria Nitrobacter-related cells were intensively indicated . Moreover, some aerobic denitrifiers as Thauera species were also identified . After the termination of pH adjustment in the preceding anaerobic reactors, nitrification tank was loaded with more biodegradable COD as a result of reduced COD removal in anaerobic reactors . Microbial diversity was immediately affected from this alteration and heterotrophic carbonaceous bacteria and aerobic denitrifiers have dominated . To provide the former high efficiencies, retention time has increased from 24 to 48 h and a second pump dosing HCl was included to the automatic control system . Subsequent to these precautions, numbers of ammonia (Nso190) and nitrite oxidizing bacteria (NIT3) were comparatively increased . In denitrification system, about 98% denitrification efficiencies were obtained at 2000 mg/L NOx-N concentrations if sodium acetate was supplied as carbon source . Meanwhile, with 20 gVSS/l biomass concentration, denitrification rates of about 1.34 mgNOx-N/mgVSSday were obtained . All sludge samples have represented similar DGGE patterns and Paraccoccus-related species were identified as dominant denitrifying bacteria.

Environ Sci Technol, 2003 Sep 15, 37(18), 4021 - 6
Fate of estrogens in a municipal sewage treatment plant; Andersen H et al.; The fate of the highly potent endocrine disrupters estrone (E1), 17beta-estradiol (E2), and 17alpha-ethinylestradiol (EE2) was investigated in mechanical and biological sewage treatment as well as in sewage-sludge treatment at a municipal German sewage treatment plant (STP) . The main outcome of the study was that a common municipal STP with an activated sludge system for nitrification and denitrification including sludge recirculation can appreciably eliminate natural and synthetic estrogens . As a consequence, the endocrine effects of biota in the receiving waters should be significantly reduced . All estrogen concentrations decreased gradually along the treatment train . In the STP effluent, the steroid estrogen concentrations were always below the quantification limit of 1 ng/L . The elimination efficiency of the natural estrogens (E1 and E2) exceeded 98%, and EE2 was reduced by more than 90% . The natural estrogens were largely degraded biologically in the denitrifying and aerated nitrifying tanks of the activated sludge system, whereas EE2 was only degraded in the nitrifying tank . Only about 5% of the estrogens are sorbed onto digested sewage sludge . It is very likely that conjugates (glucuronides and sulfates) of the estrogens were cleaved into the parent compounds mainly in the first denitrification tank.

Water Sci Technol, 2003, 48(3), 73 - 9
Evaluation of sequencing batch reactor (SBR) and sequencing batch biofilm reactor (SBBR) for biological nutrient removal from simulated wastewater containing glucose as carbon source; Kumar BM et al.; In general, conventional activated sludge (ASP) or enhanced biological phosphorus removing (EBPR) sludge has been used as seed culture for developing EBPR sludge and the time reported for development varies from months to year . In the present study cow-dung has been used as seed culture and EBPR sludge was developed within 36 days . The developed EBPR sludge has been used to evaluate the performance of sequential batch reactor (SBR) and sequential batch biofilm reactors (SBBR) for simultaneous nitrogen and phosphorus removal from synthetic wastewater containing glucose as carbon source . Three reactors were operated, SBR-1 containing only suspended biomass, SBBR-2 and SBBR-3 containing 5% and 10% polyurethane foam (PUF) media respectively along with suspended biomass . In all the reactors phosphorus removal was nearly the same and was more than 80% . In all the three reactors greater than 90% nitrification was achieved . Nitrogen removal in SBR-1 was 48% and in SBBR-2 and SBBR-3 it was more than 62% . On line monitoring of oxidation-reduction potential (ORP), pH and phosphorus during a cycle indicated that ORP and pH can be useful for real time control and optimization of the process.

Water Sci Technol, 2003, 48(3), 31 - 8
Calorimetric assessment of activity in WWTP biomass; Daverio E; A heat flux bench-scale calorimeter (Bio-RC1) has been used to assess the metabolic activity of microbial populations involved in wastewater treatment biological processes under aerobic, anoxic and anaerobic conditions . Under strictly aerobic conditions, a linear correlation was observed between oxygen uptake rate and heat flux for heterotrophic and nitrifying bacterial populations . Using the same calorimetric approach and the same apparatus, toxicity and biodegradability of a pesticides factory wastewater were investigated . The activity of heterotrophic and nitrifying aerobic communities was monitored considering both oxygen consumption and heat dissipation, whereas, under anoxic conditions, calorimetric data were compared to the traditional NUR (nitrate uptake rate) test . Heterotrophic activity was found to be 52% inhibited after toxic wastewater exposure under both aerobic and anoxic conditions and 30% inhibition was observed on autotrophic ammonia oxidation . Additionally, calorimetric measurements have been successfully applied to investigate anaerobic digestion . The thermal response of a mesophilic granular sludge to repetitive glucose pulses has been evaluated and a toxicity test has been performed by exposing the biomass to increasing concentrations of formaldehyde.

Water Sci Technol, 2003, 48(3), 17 - 24
A comparitive study of ammonia-oxidizing bacteria in lab-scale industrial wastewater treatment reactors; Rowan AK et al.; The diversity and community structure of the beta-proteobacterial ammonia oxidising bacteria (AOB) in a range of different lab-scale industrial wastewater treatment reactors were compared . Three of the reactors treat waste from mixed domestic and industrial sources whereas the other reactor treats waste solely of industrial origin . PCR with AOB selective primers was combined with denaturing gradient ge electrophoresis to allow comparative analysis of the dominant AOB populations and the phylogenetic affiliation of the dominant AOB was determined by cloning and sequencing or direct sequencing of bands excised from DGGE gels . Different AOB were found within and between different reactors . All AOB sequences identified were grouped within the genus Nitrosomonas . Within the lab-scale reactors there appeared to be selection for a low diversity of AOB and predominance of a single AOB population . Furthermore, the industrial input in both effluents apparently selected for salt tolerant AOB, most closely related to Nitrosococcus mobilis and Nitrosomonas halophila.

Biotechnol Lett, 2003 Sep, 25(17), 1469 - 71
Ammonia removal from freshwater using nitrifying bacteria enriched from a seawater aquaculture pond; Shan H et al.; Intensively cultured fish stock when fed protein-rich feeds typically excrete high concentrations of total ammoniacal-nitrogen (TAN) into the water column which can have adverse effects on productivity, and upon the environment when aquaculture water is discharged . An immobilized culture of nitrifying bacteria isolated from prawn pond water and known to effectively remove TAN from saline water was tested for its ability to remove TAN from freshwater . The culture was readily adaptable to non-saline conditions and maintained TAN at less than 0.25 mg l(-1), even with a daily addition of 3.2 to 4.2 mg TAN l(-1) per d . The use of the immobilized culture of nitrifying bacteria represents an innovative and economical in situ treatment technology for removal of TAN in both saline and freshwater.

J Biotechnol, 2003 Oct 9, 105(1-2), 71 - 82
Characterization and evaluation of aerobic granules in sequencing batch reactor; Jang A et al.; In order to investigate the aerobic granules cultured under alternating aerobic and anoxic conditions, a sequencing batch reactor (SBR) was operated without the presence of a carrier material . Nitrification and denitrification occurred alternately in the SBR operation, with an increased nitrification efficiency of up to 97% and a high chemical oxygen demand (COD) removal efficiency of up to 95% . It was observed that physical characteristics of granule play an important role in the performance of the SBR process . Light microscopy was used to observe the time dependent development of the granules in the SBR . Based on the microscopic observations, some floc-like sludges remained in the form of a mixture with granules for 30 days of operation . Even though various granule sizes had been formed in the reactor after 50 days, the granule sizes were primarily from 1 +/- 0.35 to 1.3 +/- 0.45 mm, rarely exceeding 2 mm . The granules were analyzed by a combination of microelectrodes and fluorescent in situ hybridization (FISH), which provides more detailed information on what happens inside the granules . Based on their results, ammonia oxidizing bacteria (AOB) existed primarily in the upper and middle layers of the granule . Assuming a first-order reaction for nitrification, most of the nitrification is likely to occur from the surface to 300 microm into the granular thickness.

J Biotechnol, 2003 Oct 9, 105(1-2), 33 - 40
In situ PCR for visualizing distribution of a functional gene "amoA" in a biofilm regardless of activity; Hoshino T et al.; In this study, ammonia-oxidizing bacteria present in biofilms resulting from a nitrifying reactor were detected by both a conventional FISH technique and an original in situ PCR technique . Both techniques showed that ammonia-oxidizing bacteria were found near the surface of the biofilms . However, after the biofilm had been exposed to 2 weeks of ammonia starvation, ammonia-oxidizing bacteria present in the biofilm could not be detected by fluorescence in situ hybridization (FISH) because they did not have sufficient copies of rRNA . In contrast, ammonia-oxidizing bacteria could be detected by in situ PCR with strong signal . It was thus demonstrated that a cell possessing a specific functional gene is detectable by in situ PCR regardless of its activity.

Water Res, 2003 Nov, 37(18), 4343 - 50
COD and nitrogen removal by biofilms growing on gas permeable membranes; Semmens MJ et al.; A bioreactor was constructed and used to treat a synthetic wastewater containing ammonium acetate and trace nutrients for about 190 days . The reactor was aerated by means of bundles of gas-permeable hollow-fiber membranes that were installed in the reactor . The membranes provided a specific surface area of 422 m(2)/m(3) and the external surface of the membranes rapidly became covered in an active biofilm . The membrane bundles were agitated by an internal gas recycle . The gas bubbles in the water encouraged fiber-fiber contact and were intended to control biofilm growth . Chemical oxygen demand (COD) removals in excess of 95% were achieved in a 6h nominal detention time . Nitrification developed rapidly and complete oxidation of the influent ammonium was evident within 20 days . Even though the reactor was equipped with a large membrane surface area, the oxygen was consumed within the biofilm growing on the membrane surface . As a result, the external dissolved oxygen (DO) dropped to zero and the reactor was able to support essentially complete denitrification . After about 3 months of operation the reactor showed excellent removals of both COD and inorganic nitrogen but the performance could not be sustained . Excess biofilm accumulation eventually contributed to a deterioration in process performance . This study demonstrates that while membrane aeration can provide simultaneous BOD and N removal in the same reactor, the membrane modules/bioreactor must be designed to allow for the development of thick biofilms . In addition, options for controlling the biofilm thickness need to be investigated.

Water Sci Technol, 2003, 48(2), 365 - 72
Renewable energy for the aeration of wastewater ponds; Hobus I et al.; The application of a decentralised renewable energy supply for the aeration of wastewater ponds, and the influence of an unsteady oxygen supply on the specific conversion rate and biocoenose was investigated . With the discontinuous aeration the specific conversion rate is increased as compared to facultative ponds . The estimation of the microorganisms consortia was done with in situ hybridisation techniques . A significant shift in the bacteria population with the chosen specific probes for anaerobic, sulphate reducing and nitrifying bacteria could not be detected . Wastewater ponds have sufficient buffer volume to compensate for the fluctuating energy supply . But the efficiency of the energy supply of a photovoltaic plant decreases in shallow lakes (d < 1.5 m) corresponding to a high oxygen production of algae . For the layout of the individual components: photovoltaic and wind power plant, energy management, aeration system and wastewater pond, a simulation model was developed and tested . The application of renewable energy for the aeration of wastewater ponds is a useful alternative for the redevelopment of overloaded ponds as well as the construction of new wastewater ponds, especially in areas with an inadequate central electricity grid and a high availability of wind and solar energy.

Water Sci Technol, 2003, 48(2), 197 - 204
Dynamic mathematical model of high rate algal ponds (HRAP); Jupsin H et al.; This article presents a mathematical model to describe High-Rate Algal Ponds (HRAPs) . The hydrodynamic behavior of the reactor is described as completely mixed tanks in series with recirculation . The hydrodynamic pattern is combined with a subset of River Water Quality Model 1 (RWQM1), including the main processes in liquid phase . Our aim is to develop models for WSPs and aerated lagoons, too, but we focused on HRAPs first for several reasons: Sediments are usually less abundant in HRAP and can be neglected, Stratification is not observed and state variables are constant in a reactor cross section, Due to the system's geometry, the reactor is quite similar to a plugflow type reactor with recirculation, with a simple advection term . The model is based on mass balances and includes the following processes: *Phytoplankton growth with NO3-, NO2- and death, *Aerobic growth of heterotrophs with NO3-, NH4+ and respiration, *Anoxic growth of heterotrophs with NO3-, NO2- and anoxic respiration, *Growth of nitrifiers (two stages) and respiration . The differences with regard to RWQM1 are that we included a limiting term associated with inorganic carbon on the growth rate of algae and nitrifiers, gas transfers are taken into account by the familiar Adeney equation, and a subroutine calculates light intensity at the water surface . This article presents our first simulations.

Water Sci Technol, 2003, 48(2), 129 - 35
Nutrient removal from piggery effluent using vertical flow constructed wetlands in southern Brazil; Sezerino PH et al.; Santa Catarina State, southern Brazil, has the greatest swine breeding activities of Latin America . Generally, the piggery wastewater is treated in pond systems that are able to remove organic material according to local environmental legislation . However, these systems do not remove nitrogen and phosphorus efficiently . This work deals with a post-treatment system, using vertical flow constructed wetlands . The experiment was conducted in a swine production farm which has 45,000 animals . Although the pond system was able to partially remove the content of nutrients, their concentration in the effluent was high for environmental disposal . A four-bed vertical flow constructed wetland pilot plant, using Typha spp., was built . The pilot plant operated for 280 days for beds 2-4 (sand 2) . However, the experiments with beds 1-3 (sand 1) were stopped after 111 days of operation, when a reduction in the wastewater drainage was observed . The beds with sand 2 showed a 33% COD removal, and about 49% of nitrification was observed from 111 days until the end of the operation . PO(4)-P removal was 45% with a loading rate of around 1.36 g m(-2) d(-1).

Water Res, 2003 Jul, 37(13), 3224 - 32
Molecular characterization of the microbial community structure in two activated sludge systems for the advanced treatment of domestic effluents; Eschenhagen M et al.; Although activated sludge systems with enhanced biological phosphorus removal (EBPR) represent state-of-the-art technology for phosphate removal from wastewater it is still unknown which species of bacteria are responsible for the EBPR process . The aim of this study was to compare the bacterial composition of activated sludge from two laboratory plants with different modes of operation, anoxic/oxic- (EBPR, no nitrification) and Phoredox-system (EBPR, nitrification and denitrification) with particular emphasis on microorganisms responsible for EBPR process . In addition to fluorescence in situ hybridization (FISH), we applied further rRNA-based molecular techniques like terminal restriction-fragment length polymorphism analysis and comparative 16S rDNA analysis to yield additional information and to verify the results from FISH analysis, like e.g . for the identification of polyphosphate accumulating organisms (PAO) . Despite the different modes of operation only minor differences in the bacterial composition were detected by FISH analysis based on the probes used in this study . In contrast T-RFLP analysis yielded characteristic community fingerprints for each of the investigated plants and comparative 16S rDNA analysis indicated highly diverse microbial communities in both plants suggesting substantial differences in the microbial structure . The results obtained by FISH analysis with specific probes for PAOs support the presumption that not only one specific organism is responsible for the EBPR . In our case Tetrasphaera spp . dominated the PAO community, but other possible PAOs, like Microlunatus spp . and members of the Rhodocyclus group, were also detected.

Water Res, 2003 Jul, 37(13), 3125 - 35
Dynamic response of nitrifying activated sludge batch culture to increased chloride concentration; Chen GH et al.; Dynamic response of nitrifying activated sludge batch cultures to increased chloride concentration was studied in this paper, which focused upon the changes in the specific nitrification rate (SNR) and nitrifier population when the chloride level was gradually or stepwise increased to 30,000 mg Cl L-1 . The dominant species of ammonia-oxidizers and nitriteoxidizers in the population were examined by Fluorescent in situ hybridization technique with 16S rRNA-targeted oligonucleotide probes . It was found that neither chloride increasing approaches affected the SNR of the batch cultures before the chloride concentration exceeded 10,000 mg Cl L-1, after which the stepwise increase approach reduced the SNR more significantly than the gradual increase approach . From 10,000 to 18,000 mg Cl L-1 a down-and-up pattern of the SNR variation appeared in both approaches, which was associated with the change in the dominant species of ammonia-oxidizers from non-saline-resistant species such as Nitrosomonas europaea-lineage and Nitrosomonas eutropha to saline-resistant species, such as the Nitrosococcus mobilis-lineage . Nitrobacter was the only dominant species when the chloride concentration was below 10,000 mg Cl L-1, where no nitrite-oxidizers survived . Therefore, the 10,000 mg Cl L-1 chloride level is a critical level for the shift of the nitrifier population in the nitrifying activated sludge batch cultures.

Curr Microbiol, 2003 Aug, 47(2), 77 - 83
Visualization of the cbbL gene in healthy and starved chemoautotrophic nitrifying bacteria; Sinigalliano CD et al.; Three in situ methods of visualizing the cbbL gene in intact cells of nitrifying bacteria at different physiological states (dormant and metabolically active) were compared after epifluorescence microscopy and image analysis . FISH alone showed the weakest signal intensity . Direct in situ PCR, incorporating labeled nucleotides, showed the greatest sensitivity but also the greatest background . The combination of unlabeled in situ PCR followed by FISH showed relatively high sensitivity, along with the lowest background and highest specificity . Although functional gene expression was not examined in this study, visualization of the potential for carbon fixation in heterogeneous cultures of nitrifying bacteria was demonstrated.

Bioprocess Biosyst Eng, 2003 Jan, 25(4), 249 - 53 Epub 2002 Nov 26.
Effect of carbon dioxide on nitrification rates; Denecke M et al.; Lab-scale ideal mixed, aerated reactors were employed to test the influence of carbon dioxide (CO(2)) on the growth rate of a nitrifier community . The buffer medium used did not contain any carbon sources . Reactors were inoculated alternatively with sludge from a nitrifying membrane assisted bioreactor, reflecting autotrophic material, or with sludge from a plant having denitrification and nitrification steps, which reflects mixed heterotrophic and autotrophic material . CO(2) was added as a gas with the intake air supply . Nitrification rates were related to the CO(2) in the intake air as well as to the total inorganic carbon in the medium . The batch experiments show a relationship between CO(2) concentration and growth rate . The optimum growth rate occurred at 5 mg CO(2)/L, corresponding to 0.4% (V/V) CO(2) in the inlet air . Different CO(2) optima for autotrophic and mixed sludges were found . In the case of the autotrophic sludge, the observed optimum growth rate was about 0.47/d and the optimum for the mixed sludge was about 0.75/d . Higher CO(2) concentrations lead to a decreasing growth rate . The first part of the kinetic graph can be described by Monod kinetics . Overall, the resulting graph can be described by Haldane kinetics.

Sci Total Environ, 2003 Oct 1, 314-316, 665 - 713
The fluxes and transformations of suspended particles, carbon and nitrogen in the Humber estuarine system (UK) from 1994 to 1996: results from an integrated observation and modelling study; Tappin AD et al.; Results from the first multi-constituent dynamic modelling study of the Humber estuarine system over seasonal time scales are presented . The model, constructed within the ECoS3 simulation software, has been calibrated using data obtained from 27 surveys of the Yorkshire Ouse and Humber estuaries during 1994-1996 . The model is tidally averaged, and is one-dimensional in the vertical and in cross-section . Daily-varying longitudinal concentration profiles of SPM, POC, nitrate, nitrite and ammonium have been simulated, and these have been compared with the observations used for model calibration (model confirmation) . The fits are generally good . The model captures the marked seasonal variability in concentrations of the particulate constituents (SPM, POC), and places the turbidity maximum in approximately the correct region of the estuary . There was a high degree of scatter in the SPM and POC concentrations measured due to tidal resuspension, which was not reproduced by the tidally averaged model . Comparisons between measured and simulated nitrate+nitrite are satisfactory, although for a number of surveys the modelled values are systematically too low in the lower Yorkshire Ouse and upper Humber . These discrepancies are not readily explained, but may be linked to inadequately characterised source terms for this nitrogen . The general trends in the concentrations and distributions of ammonium are reproduced by the model, despite the plethora of external inputs of this constituent, and significant modifications to ammonium transport by in situ nitrification and benthic exchange . The simulated concentrations and distributions have also been tested against independent data encapsulating axial transects in the Trent and Humber estuaries, and temporal variations at fixed sites on the Trent and Yorkshire Ouse estuaries . With some exceptions, the fits between the model results and these data are also good . The model has also been used to construct constituent budgets (external/internal sources and sinks) for each estuary for 1994, 1995 and 1996 . Riverine inputs of SPM, POC, nitrate, nitrite and ammonium decreased over the 3 years, presumably reflecting changing patterns of terrestrial runoff coupled to a reduction in effluent inputs . This trend was also observed in the point discharges of these constituents direct to the estuary . The simulated estuary was a source of sediments to the North Sea during 1994 and 1996, but a sink during 1995 . The difference has been ascribed to the exceptionally dry summer and autumn of 1995, in which up-estuary tidal 'pumping' of SPM was dominant over down-estuary flushing by river water . Fluvial inputs represent an important external source of POC to the model estuary (27-55%), as does the North Sea (26-58%) . These inputs are exceeded by POC loss via bacterial remineralisation, suggesting that the estuarine bed is a net source of POC . Riverine inputs account for 76-77% of the external inputs of nitrate . This constituent behaves quasi-conservatively in the estuary, reflecting the dilution of nitrate-rich river waters with low-nitrate coastal water, although nitrification is a significant input (approx . 21%) . Denitrification is small, and consequently all nitrate added to the estuary is lost to the North Sea . External loads of nitrite are small and ammonium nitrification accounts for approximately 93% of its annual input . Practically all of the nitrite is oxidised to nitrate, and little escapes to the North Sea . The fluvial and direct waste inputs of ammonium to the estuary are of similar size . Most of the ammonium in the model is nitrified (98-100%) and only a few tons are exported to the North Sea . In 1996 the estuary appears to have been a sink for coastal water ammonium . Constituent budgets are compared with independently evaluated fluxes . There is good agreement in a number of cases, but the comparison highlights the main uncertainties in the simulated fluxes . It is concluded that the model as currently formulated provides an excellent basis for heuristic studies of the Humber estuarine system.

Int J Syst Evol Microbiol, 2003 Sep, 53(Pt 5), 1485 - 94
16S rRNA and amoA-based phylogeny of 12 novel betaproteobacterial ammonia-oxidizing isolates: extension of the dataset and proposal of a new lineage within the nitrosomonads; Purkhold U et al.; The phylogenetic relationship of 12 ammonia-oxidizing isolates (eight nitrosospiras and four nitrosomonads), for which no gene sequence information was available previously, was investigated based on their genes encoding 16S rRNA and the active site subunit of ammonia monooxygenase (AmoA) . Almost full-length 16S rRNA gene sequences were determined for the 12 isolates . In addition, 16S rRNA gene sequences of 15 ammonia-oxidizing bacteria (AOB) published previously were completed to allow for a more reliable phylogeny inference of members of this guild . Moreover, sequences of 453 bp fragments of the amoA gene were determined from 15 AOB, including the 12 isolates, and completed for 10 additional AOB . 16S rRNA gene and amoA-based analyses, including all available sequences of AOB pure cultures, were performed to determine the position of the newly retrieved sequences within the established phylogenetic framework . The resulting 16S rRNA gene and amoA tree topologies were similar but not identical and demonstrated a superior resolution of 16S rRNA versus amoA analysis . While 11 of the 12 isolates could be assigned to different phylogenetic groups recognized within the betaproteobacterial AOB, the estuarine isolate Nitrosomonas sp . Nm143 formed a separate lineage together with three other marine isolates whose 16S rRNA sequences have not been published but have been deposited in public databases . In addition, 17 environmentally retrieved 16S rRNA gene sequences not assigned previously and all originating exclusively from marine or estuarine sites clearly belong to this lineage.

Biotechnol Bioeng, 2003 Oct 20, 84(2), 170 - 8
Simultaneous nitrification, denitrification, and phosphorus removal in a lab-scale sequencing batch reactor; Zeng RJ et al.; Simultaneous nitrification and denitrification (SND) via the nitrite pathway and anaerobic-anoxic-enhanced biological phosphorus removal (EBPR) are two processes that can significantly reduce the energy and COD demand for nitrogen and phosphorus removal . The combination of these two processes has the potential of achieving simultaneous nitrogen and phosphorus removal with a minimal requirement for COD . A lab-scale sequencing batch reactor (SBR) was operated in alternating anaerobic-aerobic mode with a low dissolved oxygen (DO) concentration (0.5 mg/L) during the aerobic period, and was demonstrated to accomplish nitrification, denitrification, and phosphorus removal . Under anaerobic conditions, COD was taken up and converted to polyhydroxyalkanoates (PHAs), accompanied by phosphorus release . In the subsequent aerobic stage, PHA was oxidized and phosphorus was taken up to <0.5 mg/L by the end of the cycle . Ammonia was also oxidized during the aerobic period, but without accumulation of nitrite or nitrate in the system, indicating the occurrence of simultaneous nitrification and denitrification . However, off-gas analysis showed that the final denitrification product was mainly nitrous oxide (N(2)O), not N(2) . Further experimental results demonstrated that nitrogen removal was via nitrite, not nitrate . These experiments also showed that denitrifying glycogen-accumulating organisms (DGAOs), rather than denitrifying polyphosphate-accumulating organisms (DPAOs), were responsible for the denitrification activity .

Appl Environ Microbiol, 2003 Sep, 69(9), 5593 - 602
Wide distribution of a novel pmoA-like gene copy among type II methanotrophs, and its expression in Methylocystis strain SC2; Tchawa Yimga M et al.; Experiments were conducted to determine if a novel pmoA-like gene (pmoA2) recently discovered in the methane-oxidizing bacterium Methylocystis strain SC2 (P . F . Dunfield, M . Tchawa Yimga, S . D . Dedysh, U . Berger, W . Liesack, and J . Heyer, FEMS Microbiol . Ecol . 41:17-26, 2002) is present in other methane-oxidizing bacteria (MOB), and if it is expressed . A newly developed primer combination (pmoA206f-pmoA703b) allowed a differential detection of pmoA1 and pmoA2 . By using this primer combination, we identified pmoA2 in a wide range of type II MOB of the Methylosinus-Methylocystis group . However, screening by PCR and by Southern hybridization using a newly developed pmoA2-specific oligonucleotide probe also showed that closely related type II MOB, exhibiting 16S rRNA gene sequence identities of higher than 97%, may or may not harbor pmoA2 . No pmoA2 was detected in five type I MOB tested: Methylococcus capsulatus strain Bath, Methylocaldum strain E10A, Methylobacter luteus, Methylomicrobium album, and Methylomonas strain D1a . In comparative sequence analyses, all pmoA2-like sequences formed a coherent cluster clearly distinct from pmoA1 sequences of type I and type II MOB, and from amoA sequences of the Nitrosomonas-Nitrosospira group . Phylogenetic analysis using the paml model suggested that pmoA2 is subject to strong purifying selection and therefore has an important cellular function . We probed total RNA extracts of Methylocystis strain SC2 for gene expression of pmoA . A strong signal was observed for pmoA1 in Northern hybridization, while the results obtained for pmoA2 were ambiguous . However, reverse transcription-PCR confirmed that pmoA2 was expressed, albeit at lower level than pmoA1 . This provided experimental evidence that the gene product of pmoA2 may be a functionally active enzyme.

Appl Environ Microbiol, 2003 Sep, 69(9), 5170 - 7
Impact of seasonal variations and nutrient inputs on nitrogen cycling and degradation of hexadecane by replicated river biofilms; Chenier MR et al.; Biofilm communities cultivated in rotating annular bioreactors using water from the South Saskatchewan River were assessed for the effects of seasonal variations and nutrient (C, N, and P) additions . Confocal laser microscopy revealed that while control biofilms were consistently dominated by bacterial biomass, the addition of nutrients shifted biofilms of summer and fall water samples to phototrophic-dominated communities . In nutrient-amended biofilms, similar patterns of nitrification, denitrification, and hexadecane mineralization rates were observed for winter and spring biofilms; fall biofilms had the highest rates of nitrification and hexadecane mineralization, and summer biofilms had the highest rates of denitrification . Very low rates of all measured activities were detected in control biofilms (without nutrient addition) regardless of season . Nutrient addition caused large increases in hexadecane mineralization and denitrification rates but only modest increases, if any, in nitrification rates, depending upon the season . Generally, both alkB and nirK were more readily PCR amplified from nutrient-amended biofilms . Both genes were amplified from all samples except for nirK from the fall control biofilm . It appears that bacterial production in the South Saskatchewan River water is limited by the availability of nutrients and that biofilm activities and composition vary with nutrient availability and time of year.

Waste Manag, 2003, 23(7), 675 - 88
Nitrogen management in bioreactor landfills; Price GA et al.; One scenario for long-term nitrogen management in landfills is ex situ nitrification followed by denitrification in the landfill . The objective of this research was to measure the denitrification potential of actively decomposing and well decomposed refuse . A series of 10-l reactors that were actively producing methane were fed 400 mg NO3-N /l every 48 h for periods of 19-59 days . Up to 29 nitrate additions were either completely or largely depleted within 48 h of addition and the denitrification reactions did not adversely affect the leachate pH . Nitrate did inhibit methane production, but the reactors recovered their methane-producing activity with the termination of nitrate addition . In well decomposed refuse, the nitrate consumption rate was reduced but was easily stimulated by the addition of either acetate or an overlayer of fresh refuse . Addition of acetate at five times the amount required to reduce nitrate did not lead to the production of NH4+ by dissimilatory nitrate reduction . The most probable number of denitrifying bacteria decreased by about five orders of magnitude during refuse decomposition in a reactor that did not receive nitrate . However, rapid denitrification commenced immediately with nitrate addition . This study shows that the use of a landfill as a bioreactor for the conversion of nitrate to a harmless byproduct, nitrogen gas, is technically viable.

Oecologia, 2003 Nov, 137(3), 417 - 25 Epub 2003 Sep 04.
Stimulation of soil nitrification and denitrification by grazing in grasslands: do changes in plant species composition matter?
Le Roux X, Bardy M, Loiseau P, Louault F.
Stimulation of nitrification and denitrification by long term (from years to decades) grazing has commonly been reported in different grassland ecosystems . However, grazing generally induces important changes in plant species composition, and whether changes in nitrification and denitrification are primarily due to changes in vegetation composition has never been tested . We compared soil nitrification- and denitrification-enzyme activities (NEA and DEA, respectively) between semi-natural grassland sites experiencing intensive (IG) and light (LG) grazing/mowing regimes for 13 years . Mean NEA and DEA (i.e . observed from random soil sampling) were higher in IG than LG sites . The NEA/DEA ratio was higher in IG than LG sites, indicating a higher stimulation of nitrification . Marked changes in plant species composition were observed in response to the grazing/mowing regime . In particular, the specific phytomass volume of Elymus repens was lower in IG than LG sites, whereas the specific volume of Lolium perenne was higher in IG than LG sites . In contrast, the specific volume of Holcus lanatus, Poa trivialis and Arrhenatherum elatius were not significantly different between treatments . Soils sampled beneath grass tussocks of the last three species exhibited higher DEA, NEA and NEA/DEA ratio in IG than LG sites . For a given grazing regime, plant species did not affect significantly soil DEA, NEA and NEA/DEA ratio . The modification of plant species composition is thus not the primary factor driving changes in nitrification and denitrification in semi-natural grassland ecosystems experiencing long term intensive grazing . Factors such as trampling, N returned in animal excreta, and/or modification of N uptake and C exudation by frequently defoliated plants could be responsible for the enhanced microbial activities.

Environ Sci Technol, 2003 Aug 15, 37(16), 3507 - 12
Indirect emissions of nitrous oxide from regional aquifers in the United Kingdom; Hiscock KM et al.; Diffuse pollution of groundwater by agriculture has caused elevated concentrations of nitrate (NO3-) and nitrous oxide (N2O) in regional aquifers . N2O is an important "greenhouse" gas, yet there are few estimates of indirect emissions of N2O from regional aquifers . In this study, high concentrations of N2O (mean 602 nM) were measured in the unconfined Chalk aquifer of eastern England, in an area of intensive agriculture . In contrast, pristine groundwaters from upland regions of England and Scotland, with predominantly natural vegetation cover, were found to have much lower concentrations of N2O (mean 27 nM) . A positive relationship between N2O and NO3- concentrations and delta18O-NO3 values of between 3.36 and 16.00/1000 suggest that nitrification is the principal source of N2O . A calculated emission factor (EF5-g) of 0.0019 for indirect losses of N2O from Chalk groundwater is an order of magnitude lower than the value of 0.015 currently used in the Intergovernmental Panel on Climate Change (IPCC) methodology for assessing agricultural emissions . A flux of N2O from the major UK aquifers of 0.04 kg N2O-N ha(-1) a(-1) has been calculated using two approaches and suggests that indirect losses of N2O from regional aquifers are much less significant (<1%) than direct emissions from agricultural soils.

J Gen Appl Microbiol, 2003 Jun, 49(3), 155 - 79
Changing concepts in the systematics of bacterial nitrogen-fixing legume symbionts; Sawada H et al.; As of February 2003, bacteria that form nitrogen-fixing symbiotic associations with legumes have been confirmed in 44 species of 12 genera . Phylogenies of these taxa containing legume symbionts based on the comparative analysis of 16S rDNA sequences show that they are not clustered in one lineage but are distributed in the classes Alphaproteobacteria and Betaproteobacteria, and dispersed over the following nine monophyletic groups, being intermingled with other taxa that do not contain legume symbionts (shown in parentheses below): Group 1, which comprises Rhizobium and Allorhizobium species containing legume symbionts (intermingled with Agrobacterium and Blastobacter species, which are nonsymbionts); Group 2, Sinorhizobium and Ensifer species (with unclassified nonsymbionts); Group 3, Mesorhizobium species (with nonsymbiotic Aminobacter and Pseudaminobacter species); Group 4, Bradyrhizobium species and Blastobacter denitrificans (with nonsymbiotic Agromonas, Nitrobacter, Afipia, and Rhodopseudomonas species); Group 5, 'Methylobacterium nodulans" (with nonsymbiotic Methylobacterium species); Group 6, Azorhizobium species (with nonsymbiotic Xanthobacter and Aquabacter species); Group 7, 'Devosia neptuniae" (with nonsymbiotic Devosia species and unclassified nonsymbionts); Group 8, symbiotic Burkholderia strains (with nonsymbiotic Burkholderia species); and Group 9, Ralstonia taiwanensis (with nonsymbiotic Ralstonia species) . For Groups 5, 8, and 9, the present classification, in which 'each monophyletic group comprises one genus wherein legume symbionts and nonsymbionts are intermingled with each other, " is considered to be retained as is because they are clearly separated from other genera at high bootstrap values and have already been sufficiently characterized based on polyphasic taxonomy . As for the remaining six monophyletic groups, on the other hand, there are currently three options for emending their current classification (definitions and circumscriptions) at the generic level: A) the current classification shall be retained as is; B) all the genera within each monophyletic group shall be amalgamated into one single genus in conformity with the results of phylogenetic analysis; or C) each subordinate lineage in each monophyletic group shall be proposed as a genus . It is considered that research and discussions will be continuously conducted for emending the classification of these monophyletic groups based chiefly on Options B and C as preferable candidates.

Water Res, 2003 Oct, 37(17), 4259 - 69
Advanced treatment of sewage by pre-coagulation and biological filtration process; Hidaka T et al.; A pre-coagulation and bio-filtration process for advanced treatment of sewage was developed and experimentally discussed with a pilot plant . The bio-filtration unit consists of a denitrification filter, a nitrification filter with side stream to the denitrification filter, and a polishing filter with anoxic and aerobic parts . Concentrations of SS, T-COD(Cr), T-carbonaceous BOD, T-N and T-P in the effluent were stably kept at less than 3, 20, 5mg/L, 2mg N/L and 0.2mg P/L, respectively, and transparency at higher than 100 cm, under total hydraulic retention time of 3.2h in the bio-filtration parts (filter-bed) . ORP in an anoxic tank before a nitrification tank should be at a low level of less than -120 mV to keep remaining NO(-)(x) - N less than 1mg N/L, but must be maintained at a level higher than -150 mV . The maximum nitrogen-loading rate under a water temperature of 18 degrees C should be less than 0.25 kg N/(m(3)-filter-bed.d) . Concentrations of microorganisms kept in the reactors were as high as 4000-5000 mg COD/L-filter-bed . Denitrification activity of 0.4 or 0.7 kg N/(m(3)-filter-bed.d), and nitrification activity of 0.3 kg N/(m(3)-filter-bed.d) were obtained, respectively, under a water temperature of about 18 degrees C . Backwashing in each tank as well as methanol addition and aeration in the polishing filter were operated successfully by the automatic control systems . These results proved that this process is applicable to advanced treatment of sewage with easy maintenance.

Water Res, 2003 Oct, 37(17), 4236 - 42
Annual cycle of nitrogen removal by a pilot-scale subsurface horizontal flow in a constructed wetland under moderate climate; Kuschk P et al.; The annual course of nitrogen removal in a stable operating subsurface horizontal flow constructed wetland (SSF) in a moderate climate was evaluated using a large pool of data from 4 years of operation . In spring and autumn removal efficiencies were found to depend on the nitrogen load in a linear mode . The efficiencies in winter and summer differed extremely (mean removal rates of 0.15/0.7 g m(-2) d(-1) (11%/53%) in January/August) and were independent of the nitrogen load (0.7-1.7 g m(-2) d(-1)) in principle . Oscillations of the removal rates in spring, forming several maxima, suggest seasonal specific effects caused by the dynamics of the plant-physiology finally determining the nitrification efficiency, i.e . via O(2)-supply . Nitrification is limited by temperature during all seasons and surprisingly in midsummer additionally restricted by other seasonal aspects forming a clear-cut relative nitrification minimum (mean rate of 0.43 g m(-2) d(-1) (32%)) in July . The importance and the effect of the plants' gas exchange and oxygen input into the rhizosphere are discussed . Denitrification was nearly complete in midsummer and was clearly restricted at seasonal temperatures below 15 degrees C.

Water Res, 2003 Oct, 37(17), 4211 - 21
Biological nitrogen removal of high-strength ammonium industrial wastewater with two-sludge system; Carrera J et al.; The biological nitrogen removal (BNR) process is the most common method for removing low quantities of ammonium from wastewater, but this is not the usual treatment for high-strength ammonium wastewater . The capacity to biologically remove the nitrogen content of a real industrial wastewater with a concentration of 5000 g N-NH(4)(+) L(-1) is demonstrated in this work . The experimental system used is based on a two-sludge system, with a nitrifying activated sludge and a denitrifying activated sludge . This system treated real industrial wastewater for 450 days, and during this period, it showed the capacity for oxidizing all the ammonium at average nitrification rates between 0.11 and 0.18 g N-NH(4)(+)g VSS(-1)d(-1) . Two key process parameters were evaluated: the maximum nitrification rate (MNR) and the maximum denitrification rate (MDR) . MNR was determined in continuous operation at three different temperatures: 15 degrees C, 20 degrees C and 25 degrees C, obtaining values of 0.10, 0.21 and 0.37 g N-NH(4)(+) g VSS(-1)d(-1), respectively . Complete denitrification was achieved using two different industrial carbon sources, one containing mainly ethanol and the other one methanol . The MDR reached with ethanol (0.64 g N-NO(x)(-) g VSS(-1)d(-1)) was about 6 times higher than the MDR reached with methanol (0.11g N-NO(x)(-)g VSS(-1)d(-1)).

Water Res, 2003 Oct, 37(17), 4202 - 10
Effects of predation and ORP conditions on the performance of nitrifiers in activated sludge systems; Lee Y et al.; Effects of changing oxidation-reduction potential (ORP) and grazing of protozoa on nitrifiers in activated sludge systems was investigated . This study used sequencing batch reactors which were acclimated under aerobic and alternating anoxic/aerobic conditions, with and without inhibition of protozoa, the predatory microorganisms . The feed used was a synthetic wastewater containing beef and yeast extracts as a carbon source . It was found that the biomass, determined by mixed liquor volatile suspended solids (MLVSS) in the reactors, was significantly affected by predation while ORP (aerobic and alternating anoxic/aerobic conditions) has no impact on the MLVSS regardless of the presence or absence of predation . However, the nitrification rates in the reactors show completely different trends indicating that the ORP of the system has a significant impact on the rates while predation does not . It was found that nitrification rates in alternating reactors were almost double the rates in the aerobic reactors, both with and without predatory inhibition . The decay rate of autotrophic bacteria (b(A)) in aerobic reactors was determined by tracking the decrease of the maximum nitrification rate under both anoxic and aerobic starvation conditions . The b(A) in alternating anoxic/aerobic reactors was also determined under alternating starvation conditions . It was found that, in any case, the alternating anoxic/aerobic autotrophic biomass b(A) was much smaller that the b(A) of aerobic biomass determined under aerobic and anoxic starvation conditions . The alternating anoxic/aerobic b(A) was 62.1% less than the aerobic biomass b(A) under aerobic starvation and 40.2% less for the aerobic biomass starved under anoxic conditions . No statistically significant differences in b(A) were observed between reactors with or without the inhibition of predators.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003 Sep, 38(9), 1927 - 37
Treatability study of a seafood-processing wastewater; Mines RO Jr et al.; The unique characteristics of seafood-processing wastewater require a treatability study be performed . Wastewater from seafood-processing contains high concentrations of nitrogen and suspended solids along with large volumes of wastewater . This treatability study was undertaken using a 10 L per day, bench-scale, modified Ludzack-Ettinger (MLE) process that was designed, constructed, and operated for approximately eight (8) months . Influent and effluent data collected on the system included: chemical oxygen demand (COD), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total nitrogen (TN), pH, total phosphorus (TP), dissolved oxygen (DO), alkalinity, and temperature . All analyses were performed in accordance with Standard Methods . Influent characteristics ranged from 892 to 7470 mg/L COD, 36 to 1037 mg/L TKN, 70 to 3450 mg/L TSS, and 39 to 86 mg/L TP . Mean cell residence time (MCRT) served as the primary control parameter with average MCRTs of 5.3, 6.4, 8.5, and 30.9 days observed during the study . Biokinetic coefficients determined at 25 degrees C during the study included a yield coefficient (Y) of 0.42 mg TSS/mg COD and an endogenous decay coefficient (kd) of 0.22 days(-1) . The average, overall observed specific nitrification rate (SNR) and average observed specific denitrification rate (SDNR) was 0.084 days(-1) and 0.051 days(-1), respectively . UV-Vis spectroscopy was found to have a potential for characterizing the biological treatment process . The MLE is an effective method of biologically treating a seafood-processing wastewater.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003 Sep, 38(9), 1689 - 702
Carbon and nutrient removal in a dual-media fluidized bed reactor; Safferman SI et al.; A dual-media fluidized bed is a unique reactor design containing two distinct media that results in two segregated treatment zones . By the strategic use of these two zones, this design has the potential to remove both BOD and nutrients (nitrogen and phosphorus) in a single compact reactor . Three operational strategies are conceivable . The first is to maintain a microbiological zone close to the influent to achieve BOD and nitrogen removal . The zone above would contain an exchange media to remove phosphorous . In another scenario, the lower zone would be kept aerobic and the higher zone anoxic . This would enhance denitrification . In the third scenario, the first two are combined by having the exchange media serve as the anoxic zone or including an independent third zone (aerobic, anoxic, and exchange) . This scenario could result in the comprehensive treatment of BOD, nitrogen, and phosphorus removal . This proof-of-concept research primarily investigated the first scenario and provided preliminary data for the other two . A low-loaded operating strategy was used to minimize the inherent disadvantages of a fluidized bed reactor, primarily caused by excessive biofilm growth . The reactor was operated for approximately 1 year using sand and activated alumina as the two media . Good separation with minimum mixing at the interface resulted . BOD and phosphorus removal and nitrification were consistently very good during non-transitional periods . Denitrification varied depending on the influent concentration, dissolved oxygen, and oxidation/reduction potential . Preliminary data also indicated that when a low recirculation ratio is used, denitrification could be enhanced . There appears to be a potential difficulty, however, in exchanging phosphorous using activated alumina under low oxidation/reduction potential conditions.

J Environ Sci (China), 2003 May, 15(3), 423 - 32
The integration of methanogenesis with denitrification and anaerobic ammonium oxidation in an expanded granular sludge bed reactor; Zang DJ; The integration of methanogenesis with denitrification and anaerobic ammonium oxidation (ANAMMOX) was studied in an expanded granular sludge bed (EGSB) reactor in this work . Experimental results from the continuous treatment of wastewater with nitrite and ammonium, which lasted for 107 days, demonstrated that wastewater with high nitrite and ammonium could be anaerobically treated in an expanded granular sludge bed reactor . More than 91% to 97% of COD were removed at up to about 3.9 g COD/(L x d) of COD volumetric loading rate . More than 97% to 100% of nitrite was denitrified at up to about 0.8 g NO2(-) -N/(L x d), which is 16 times higher than that in a conventional activated sludge system with nitrification/denitrification (0.05 gN/(L x d)) . No dissimilatory reduction of nitrite to ammonium occurred in the process . However, maximum of about 40% ammonium was found to be lost . Batch tests of 15 days with sludge from the reactor showed that 100% of nitrite was denitrified completely, and about 3% of ammonium was removed when only ammonium (34.3 mg/L) and nitrite (34.3 mg/ L) were added into the sludge suspension medium . Furthermore, about 15% of ammonium amounts were lost with organic COD addition . It suggested that the methanogenesis in the system could enhance ANAMMOX because of intermediate hydrogen produced during methanogenesis.

J Environ Sci (China), 2003 May, 15(3), 363 - 6
Effects of lignin on nitrification in soil; Huang YZ et al.; The effects of two lignins isolated from black liquor from pulping process on nitrification in soils after addition of urea, (NH4)2SO4 and (NH4)2HPO4 were investigated by incubation at 20 or 30 degrees C for 7 or 14 d . The effects of lignin on nitrous oxide emissions from soil were also determined . Results showed that both lignins were more effective for inhibiting nitrification of NH4(+)-N as (NH4)2SO4 or (NH4)2HPO4 as compared to urea-N . The effectiveness of lignin on nitrification was markedly affected by different soil type and temperature . Nitrous oxide emissions from soil declined when lignin was used . Urea plus 20 and 50 g/kg lignin reduced N2O emissions by about 83% and 96% . respectively, while (NH4)2HPO4 plus 20 and 50 g/kg lignin respectively reduced emissions by 83% and 93% . Because of its low cost and nonhazardous characteristics, lignin has potential value as a fertilizer amendment to improve N fertilizer efficiency.

J Environ Qual, 2003 Jul-Aug, 32(4), 1464 - 73
Predicting nitrate leaching under potato crops using transfer functions; Gasser MO et al.; Nitrate leaching is a major issue in many cultivated soils . Models that predict the major processes involved at the field scale could be used to test and improve management practices . This study aims to evaluate a simple transfer function approach to predict nitrate leaching in sandy soils . A convective lognormal transfer (CLT) function is convoluted with functional equations simulating N mineralization, plant N uptake, N fertilizer dissolution, and nitrification at the soil surface to predict solute concentrations under potato (Solanum tuberosum L.) and barley (Hordeum vulgare L.) fields as a function of drainage water . Using this approach, nitrate flux concentrations measured in drainable lysimeters (1-m soil depth) were reasonably predicted from 29 Apr . 1996 to 3 Dec . 1996 . With average application rates of 16.9 g m(-2) of N fertilizer in potato crops, mean nitrate-leaching losses measured under potato were 8.5 g N m(-2) . Tuber N uptake averaged 9.7 g N m(-2) and soil mineral N at start (spring) and end (fall) of N mass balance averaged 1.7 and 4.5 g N m(-2), respectively . Soil N mineralization was estimated by difference (4.3 g N m(-2) on average) and was small compared with N fertilization . Small nitrate flux concentrations at the beginning of the cropping season (May) resulted mainly from initial soil nitrate concentrations . Measured and predicted nitrate flux concentrations significantly increased at mid-season (July-August) following important drainage events coupled with complete dissolution and nitrification of N fertilizers, and declining N uptake by potato plants . Decreases in nitrate concentrations before the end of year (November-December) underlined the predominant effect of N fertilizers applied for the most part at planting acting as a pulse input of solute.

J Environ Qual, 2003 Jul-Aug, 32(4), 1346 - 55
Response of soil microbiological activities to cadmium, lead, and zinc salt amendments; Stuczynski TI et al.; Heavy metal pollution of soil has been recognized as a major factor impeding soil microbial processes . From this perspective, we studied responses of the soil biological activities to metal stress simulated by soil amendment with Zn, Pb, and Cd chlorides . The amounts of heavy metal salts added to five metal-polluted soils and four nonpolluted soils were selected to match the total metal concentrations typically found in polluted soils of the Silesia region of Poland . From the perspective of soil quality, metal mobility in amended soils could not be described by simple functions of pH or organic matter . Reaction of Pb with the soil caused strong immobilization with less than 1% of the Pb amendment recovered by 0.01 M CaCl2 extractions . Immobilization of Cd was also significant, whereas immobilization of the Zn amendment was much weaker than that of Cd or Pb . The Zn amendment had substantial inhibitory effect on soil dehydrogenase, acid and alkaline phosphatase, arylsulfatase, urease, and nitrification potential . Generally, Cd and Pb had limited or stimulatory effect on most of these biological activities, with an exception of Pb strongly inhibiting soil urease . The effect of the metal amendments on biological activities could not be satisfactorily accounted for by metal toxicity because no strong relationship was observed between extractable metal content and the degree of inhibition . The Zn amendment had a significant effect on soil pH, resulting in confounding effects of pH and Zn toxicity on activities . Metal amendment experiments seem to be of limited utility for meaningful assessment of metal contamination effects on soil quality.

J Environ Qual, 2003 Jul-Aug, 32(4), 1204 - 11
Gaseous nitrogen emissions and mineral nitrogen transformations as affected by reclaimed effluent application; Master Y et al.; Irrigation with reclaimed effluent (RE) is essential in arid and semiarid regions . Reclaimed effluent has the potential to stimulate gaseous N losses and affect other soil N processes . No direct measurements of the N2 and N2O emissions from Mediterranean soils have been conducted so far . We used the 15N gas flux method in a field and a laboratory experiment to study the effect of RE irrigation on gaseous N losses and other N transformations in a Grumosol (Chromoxerert) soil . The fluxes of N2, N2O, and NH3 were measured from six Grumosol lysimeters following application of either fresh water or RE . The N fertilizer was applied either as 15NH4 or 15NO3 . Only up to 0.3% from the applied N fertilizer was lost as N2O + NH3 . Reclaimed effluent enhanced the losses of NH3, but did not affect those of N2O . Nitrification and denitrification were equally important to N2O production . Laboratory incubations were performed to both confirm the influence of the irrigation water type and to test the effect of moisture content . Significant quantities of N2 and N2O (up to 3.1% of the applied fertilizer) were emitted from saturated soils . Reclaimed effluent application did not induce higher N2O emissions, yet significantly more (approximately 33%) N2 was emitted from RE-irrigated soils . Denitrification contributed up to 75% of the N2O amounts emitted from saturated soils . Reclaimed effluent application inhibited nitrification in the Grumosol by 15 to 25% and induced NO2 accumulation in soils incubated at a field-capacity moisture content.

J Environ Qual, 2003 Jul-Aug, 32(4), 1194 - 203
Nitrous oxide emission and denitrification in chronically nitrate-loaded riparian buffer zones; Hefting MM et al.; Riparian buffer zones are known to reduce diffuse N pollution of streams by removing and modifying N from agricultural runoff . Denitrification, often identified as the key N removal process, is also considered as a major source of the greenhouse gas nitrous oxide (N2O) . The risks of high N2O emissions during nitrate mitigation and the environmental controls of emissions have been examined in relatively few riparian zones and the interactions between controls and emissions are still poorly understood . Our objectives were to assess the rates of N2O emission from riparian buffer zones that receive large loads of nitrate, and to evaluate various factors that are purported to control N emissions . Denitrification, nitrification, and N2O emissions were measured seasonally in grassland and forested buffer zones along first-order streams in The Netherlands . Lateral nitrate loading rates were high, up to 470 g N m(-2) yr(-1) . Nitrogen process rates were determined using flux chamber measurements and incubation experiments . Nitrous oxide emissions were found to be significantly higher in the forested (20 kg N ha(-1) yr(-1)) compared with the grassland buffer zone (2-4 kg N ha(-1) yr(-1)), whereas denitrification rates were not significantly different . Higher rates of N2O emissions in the forested buffer zone were associated with higher nitrate concentrations in the ground water . We conclude that N transformation by nitrate-loaded buffer zones results in a significant increase of greenhouse gas emission . Considerable N2O fluxes measured in this study indicate that Intergovernmental Panel on Climate Change methodologies for quantifying indirect N2O emissions have to distinguish between agricultural uplands and riparian buffer zones in landscapes receiving large N inputs.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003 Aug, 38(8), 1479 - 88
Biological removal of carbon, nitrogen, and phosphorus in a sequencing batch reactor; Akin BS et al.; In this research the process performance of enhanced biological phosphorus removal was investigated in a sequencing batch reactor (SBR) having a new operational mode . The SBR system used in this study had simultaneous feeding and decanting conditions . The laboratory scale reactor (10 L) was operated for 392 days . The system was operated under 4 different sets each having 2 cycles per day . In each cycle, fill (4 h), anoxic (0.5 h), aerobic (7 h) and settling phases were present . In the fill phase, wastewater was fed from the bottom and the anoxic/anaerobic conditions were established in the settled sludge . During filling, the water left the system by water displacement . The system provided nitrification, denitrification as well as phosphorus and organic removal . High COD (90-98%), PO4-P (77-100%), and NH4-N (90-95%) removals were achieved by this system.

J Hazard Mater, 2003 Jul 18, 101(2), 219 - 29
Influence of hydraulic loading and air flowrate on urban wastewater nitrogen removal with a submerged fixed-film reactor; Galvez JM et al.; Nutrient disposal to sensitive areas, particularly nitrogen and phosphorus from wastewater treatment plants, provokes eutrophication reducing water quality . Fixed film technology is widely used for the removal of organic matter and nitrogen by the biological process of nitrification-denitrification . This paper studies a nitrification and post-denitrification lab-scale plant with a downflow aerobic submerged filter for removal of organic matter and nitrification, followed by an anoxic upflow biofilter for denitrification . Recycled construction material (clay shists) was employed as support material and methanol was used as carbon source . After 2 weeks of acclimation in which nitrification reached steady-state conditions, different hydraulic loadings (0.35-1.59 m(3)/m(2)h) and air flowrates (7.78-43.5 m(3)/m(2)h) were applied for 1 year . The highest hydraulic loading which complied with the EU regulation on nitrogen disposal was 0.71 m(3)/m(2)h (1.6 h) . Hydraulic retention time (HRT), which corresponded to a nitrogen removal of 0.64 kg N/m(3) per day operating at an air flowrate of 25.6 m(3)/m(2)h . Concerning to organic matter removal efficiency, the aerobic reactor accepted a maximum chemical oxygen demand (COD) volumetric loading of 16.0 kg COD/m(3) per day with a 75% COD removal efficiency . For all the tests carried out, suspended solids (SS) concentration in the outlet water was less than 35 mg/l.

Water Sci Technol, 2003, 47(12), 155 - 61
Comparison of the performance of MBBR and SBR systems for the treatment of anaerobic reactor biowaste effluent; Comett-Ambriz I et al.; Anaerobic reactor biowaste effluent was treated with biofilm and activated sludge sequencing batch reactors to compare the performance of both systems . The treatment targets were organic carbon removal and nitrification . The pilot plant was operated in two phases . During the first phase, it was operated like a Moving Bed Biofilm Reactor (MBBR) with the Natrix media, with a specific surface area of 210 m2/m3 . The MBBR was operated under Sequencing Batch Reactor (SBR) modality with three 8-hour cycles per day over 70 days . During the second phase of the experiment, the pilot plant was operated over 79 days as a SBR . In both phases the influent was fed to the reactor at a flow rate corresponding to a Hydraulic Retention Time (HRT) of 4 days . Both systems presented a good carbon removal for this specific wastewater . The Chemical Oxygen Demand (COD) total removal was 53% for MBBR and 55% for SBR . MBBR offered a higher dissolved COD removal (40%) than SBR (30%) . The limited COD removal achieved is in agreement with the high COD to BOD5 ratio (1/3) of the influent wastewater . In both systems a complete nitrification was obtained . The different efficiencies in both systems are related to the different biomass concentrations.

Water Sci Technol, 2003, 47(12), 1 - 7
Upgrading the Sjölunda WWTP according to a novel process concept; Hanner N et al.; The Sjolunda wastewater treatment plant in Malmo, Sweden, was upgraded for extended nutrient removal in 1998-1999 . The design was based on future effluent standards of 10 mg BOD7/l, 0.3 mg total-P/l and 8 mg total-N/l . The upgrading concept took into consideration existing processes and structures, resulting in a cost-effective and compact upgrading . To introduce nitrification, the existing trickling filters for BOD-removal were converted to a nitrifying mode . A sequencing batch reactor for nitrification of supernatant was necessary to control the ammonia load . Denitrification was accomplished in a moving bed biofilm reactor with addition of external carbon source . The future effluent standards could be met by the upgraded plant . The trickling filters were stable despite varying loading conditions . High rates and low effluent ammonia concentrations were achieved . Essential features for stable post denitrification were control strategies for carbon source dosage and avoiding phosphorus limitation.

Water Sci Technol, 2003, 48(1), 191 - 8
High-strength nitrogen removal of opto-electronic industrial wastewater in membrane bioreactor--a pilot study; Chen TK et al.; The membrane bioreactor (MBR) system has become more and more attractive in the field of wastewater treatment . It is particularly attractive in situations where long solids retention times are required, such as nitrifying bacteria, and physical retention critical to achieving more efficiency for biological degradation of pollutant . Although it is a new technology, the MBR process has been applied for industrial wastewater treatment for only the past decade . The opto-electronic industry, developed very fast over the past decade in the world, is high technology manufacturing . The treatment of the opto-electronic industrial wastewater containing a significant quantity of organic nitrogen compounds with a ratio over 95% in organic nitrogen (Org-N) to total nitrogen (T-N) is very difficult to meet the discharge limits . This research is mainly to discuss the treatment capacity of high-strength organic nitrogen wastewater, and to investigate the capabilities of the MBR process . A 5 m3/day capacity of MBR pilot plant consisted of anoxic, aerobic and membrane bioreactor was installed for evaluation . The operation was continued for 150 days . Over the whole experimental period, a satisfactory organic removal performance was achieved . The COD could be removed with an average of over 94.5% . For TOC and BOD5 items, the average removal efficiencies were 96.3 and 97.6%, respectively . The nitrification and denitrification was also successfully achieved . Furthermore, the effluent did not contain any suspended solids . Only a small concentration of ammonia nitrogen was found in the effluent . The stable effluent quality and satisfactory removal performance mentioned above were ensured by the efficient interception performance of the membrane device incorporated within the biological reactor . The MBR system shows promise as a means of treating very high organic nitrogen wastewater without dilution . The effluent of TKN, NOx-N and COD can fall below 20 mg/L, 30 mg/L and 50 mg/L.

Water Sci Technol, 2003, 48(1), 119 - 30
Nitrification and autotrophic denitrification of source-separated urine; Udert KM et al.; In laboratory experiments, source-separated urine was stabilised with nitrification and denitrified via nitritation and anaerobic ammonium oxidation . The highest total ammonia concentration in the influent was 7,300 gN/m3, the maximum pH 9.2 . In a moving bed biofilm reactor (MBBR) with Kaldnes biofilm carriers, we stabilised urine as a 1:1 ammonium nitrate solution . The maximum nitrification rate was 380 gN/m3/d corresponding to 1.7 gN/m2(biofilm)/d . Nitrite ammonium solutions were produced in a continuous flow stirred tank reactor (CSTR) with 4.8 days sludge retention time (SRT) at 30 degrees C and in a sequencing batch reactor (SBR) with more than 30 days SRT . Nitrate build-up was negligible in both reactors . Nitritation rates were 780 gN/m3/d in the CSTR and 280 gN/m3/d in the SBR, respectively . However, shortening the cycles would increase nitritation in the SBR . High concentrations of nitrous acid, salts, and presumably hydroxylamine suppressed nitrite oxidation in the nitritation reactors . In all three nitrification reactors, maximally 50% of the influent total ammonia was oxidised without pH control . None of the common inhibition or limitation approaches could explain why ammonia oxidation always stopped at pH values around 6 . In a batch experiment, we showed that source-separated urine can be denitrified autotrophically by anammox bacteria.

Environ Microbiol, 2003 Sep, 5(9), 798 - 803
In situ distribution and activity of nitrifying bacteria in freshwater sediment; Altmann D et al.; Nitrification was investigated in a model freshwater sediment by the combined use of microsensors and fluorescence in situ hybridization with rRNA-targeted oligonucleotide probes . In situ nitrification activity was restricted mainly to the upper 2 mm of the sediment and coincided with the maximum abundance of nitrifying bacteria, i.e . 1.5 x 107 cells cm-3 for ammonia-oxidizing Beta-proteobacteria (AOB) and 8.6 x 107 cells cm-3 for Nitrospira-like nitrite-oxidizing bacteria (NOB) . Cell numbers of AOB decreased more rapidly with depth than numbers of NOB . For the first time, Nitrospira-like bacteria could be quantified and correlated with in situ nitrite oxidation rates in a sediment . Estimated cell-specific nitrite oxidation rates were 1.2-2.7 fmol NO2- cell-1 h-1.

Huan Jing Ke Xue, 2003 May, 24(3), 158 - 60
{Nitrogen removal in a pilot-scale zeolite reed bed system}; Li X et al.; In this study, the nitrogen removal efficacy of a pilot-scale zeolite reed bed system was tested for the treatment of agricultural wastewater and domestic wastewater etc . At a mean hydraulic loading of 0.6 m/d, the total nitrogen, ammonia, nitrate, nitrite in winter and spring were reduced across the system by 38.9% and 58.2%, 93.11% and 78.84%, 10.01% and 48.99%, 38.81% and 98.45%, respectively . The system performance in spring was much better than in winter . Under the same conditions, the total nitrogen, ammonia, nitrate removal rate of zeolite reed bed were 28%, 67%, 35% higher than that of gravel reed bed . The ammonia adsorption and ion exchange on zeolite and biological nitrogen removal through nitrification and denitrification were the main removal mechanism of nitrogen in the zeolite reed bed.

Huan Jing Ke Xue, 2003 May, 24(3), 50 - 5
{Nitrogen removal from the sewage containing seawater via nitrite pathway}; Yu D et al.; With control of the concentration of free ammonia (FA), shortened nitrification-denitrification was accomplished in SBR to achieve enhanced nitrogen removal from the sewage containing seawater . Several parameters which included salinity, temperature, pH and NH4(+)-N load were studied to evaluate their effects . The results of experiences indicated that shortened nitrification-denitrification can be accomplished in sewage containing seawater with relatively high salinity . With various salinity, the nitrogen removal efficiency had relationship with the NH4(+)-N load, there should be a lower NH4(+)-N load when the salinity was high . The nitrogen removal efficiency reached above 90% when the NH4(+)-N load was not exceed 0.15 kg/(kg.d) . Elevation of the temperature availed to higher nitrogen removal efficiency, this efficiency doubled when the reaction temperature was changed from 20 degrees C to 30 degrees C . Relatively high value of pH, in the range of 7.5 and 8.5 had advantage to achieve effective shortened nitrification-denitrification which caused by the selective inhibition of free ammonia(FA).

J Environ Radioact, 2003, 70(1-2), 85 - 97
Influence of climatic conditions and soil type on 99TcO4- uptake by rye grass; Echevarria G et al.; Climatic changes over the long term will modify significantly the biosphere, with glaciation events probably taking place in the next 100 000 years . This is important to safety assessments of nuclear waste disposal facilities that contain high-level and long-lived waste.The soils will evolve toward new situations, and their properties will be consequently modified (e.g . an increase of soil organic matter may be expected in a cooler climate) . These changes in soil properties would affect the mobility and the soil-to-plant transfer of radionuclides such as (99)Tc . This study aimed at simulating the cooling of climatic conditions for soils representative of a Jurassic limestone plateau, and the effect on transfer parameters of (99)TcO(4)(-) in the soil-plant systems was investigated . The cooler conditions were simulated by increasing elevation, a surrogate for climate change . Soils were sampled in similar geological background and topography at different elevations in the north east of France (Lorraine and Jura) . Soil/solution distribution coefficients (K(d)) of (99)TcO(4)(-) were measured on soil samples in short-term batch experiments with 1:10 soil:solution ratio . Rye grass was grown on the soils spiked with (99)TcO(4)(-) at temperature regimes adapted to each soil . Also, two different temperature regimes (cold and temperate) were applied to one soil to test the effect of plant physiology and evapotranspiration on (99)TcO(4)(-) uptake . K(d) values did not show significant differences among soils in aerobic conditions, and were not significantly different from 0 . During plant culture, reduction of (99)Tc was never totally achieved in soils, including in a peaty OM soil . Concentration ratios (CR) were calculated on a dry weight basis and ranged from 20 to 370 . CR were always higher in high temperature regimes than in cold temperatures . They were also inversely correlated with soil organic matter (OM) content . A decrease of CR values from 5 to 10-fold was observed with increasing soil OM . Results suggested that the water holding capacity, in which (99)Tc is diluted, the nitrification potential of the soils and the evapotranspiration of plants (efficiency of uptake of soluble (99)TcO(4)(-)) were strongly involved in these differences.

Appl Microbiol Biotechnol, 2003 Dec, 63(2), 217 - 21 Epub 2003 Aug 08.
Improved method for determination of ammonia and nitrite oxidation activities in mixed bacterial cultures; Moussa MS et al.; A simple and reliable method to measure the activity of ammonia and nitrite oxidisers in mixed bacterial cultures was developed . The developed method differentiates between the ammonia and nitrite oxidisers by consecutive injection of NO2- and NH4+ . The main advantage of this method is that it avoids the use of metabolic inhibitors for ammonia or nitrite oxidisers, as used by other methods . Moreover, it allows measuring of the short-term effect of an inhibitor on both the ammonia and nitrite oxidisers in one test under controlled environmental conditions (pH, temperature) . The developed method was applied to determine the inhibitory effects of salt (NaCl up to 15 g Cl/l) on an enriched culture of nitrifying bacteria . The results of the method demonstrate its potential to accurately determine the individual activities of nitrite and ammonia oxidisers.

Microbiol Res, 2003, 158(2), 151 - 61
Rhizosphere microflora of plants used for the phytoremediation of bitumen-contaminated soil; Muratova A et al.; The microbial communities and their degradative potential in rhizospheres of alfalfa (Medicago sativa) and reed (Phragmites australis) and in unplanted soil in response to bitumen contamination of soil were studied in pot experiments . According to the results of fluorescence microscopy, over a period of 27 months, bitumen contamination of soil reduced the total number of microorganisms more significantly (by 75%) in unplanted than in rhizosphere soil (by 42% and 7% for reed and alfalfa, respectively) and had various effects on some important physiological groups of microorganisms such as actinomycetes as well as nitrogen-fixing, nitrifying, denitrifying, ammonifying, phosphate-solubilizing, sulphur-oxidizing, cellulolytic and hydrocarbon-degrading microorganisms . The changes in the physiological structure of the microbial community under bitumen contamination were found to hinge on not merely the presence of plants but also their type . It was noted that the rhizosphere microflora of alfalfa was less inhibited by hydrocarbon pollution and had a higher degradative potential than the rhizosphere microflora of reed.

Water Sci Technol, 2003, 47(11), 305 - 12
Optimum aerobic volume control based on continuous in-line oxygen uptake monitoring; Svardal K et al.; Dynamic adaptation of the aerated volume to changing load conditions is essential to maximise the nitrogen removal performance and to minimise energy consumption . A control strategy is presented which provides optimum aerobic volume control (OAV-control concept) based on continuous in-line oxygen uptake monitoring . For ammonium concentrations below 1 mg/l the oxygen uptake rate shows a strong and almost linear dependency on the ammonium concentration . Therefore, the oxygen uptake rate is an ideal indicator for the nitrification performance in activated sludge systems . The OAV-control concept provides dynamic variation of the minimum aerobic volume required for complete nitrification and therefore maximises the denitrification performance . In-line oxygen uptake monitoring is carried out by controlling the oxygen concentration in a continuous aerated zone of the aeration tank and measuring the total air flow to the aeration tank . The total air flow to the aeration tank is directly proportional to the current oxygen uptake rate and can therefore be used as an indicator for the required aerobic volume . The instrumentation requirements for installation of the OAV-control are relatively low, oxygen sensors in the aeration tank and an on-line air flow measurement are needed . This enables individual control of aeration tanks operated in parallel at low investment costs . The OAV-control concept is installed at the WWTP Linz-Asten (1 Mio PE) and shows very good results . Full scale results are presented.

Water Sci Technol, 2003, 47(11), 259 - 65
Improving titrimetric techniques by modelling pH change in activated sludge systems; Pratt S et al.; Existing titrimetric techniques rely on a well defined hydrogen ion production rate . In particular, they are only suitable in circumstances in which constant background pH influencing reactions take place . This is rarely the case due to the presence of the carbonate acid/base system . In this paper, a model, which describes the influence of the nitrification process on pH and accounts for the action of the carbonate system, is presented . The validity of the model is tested by comparison of model predictions for the important state variables with that of experimental data from a batch oxidation of ammonium nitrogen . The two cases studied are the responses of an endogenously respiring nitrifying sludge to: an ammonium chloride pulse and a pulse of both bicarbonate and ammonium chloride . The results are most encouraging as the dynamic HPR response is mirrored by the model simulation . Furthermore, using the model for data interpretation, the initial nitrogen substrate levels are recovered . It is shown that this could not have been achieved in either case using existing titrimetric techniques.

Water Sci Technol, 2003, 47(11), 211 - 8
Efficiency of the Activated Sludge Model no . 3 for German wastewater on six different WWTPs; Wichern M et al.; In 1999, the Activated Sludge Model No . 3 by the IWA Task Group on Mathematical Modelling for the Design and Operation of Biological Wastewater Treatment was presented . The model is used for the simulation of nitrogen removal . The simulations in this paper were done on the basis of a new calibration of the ASM 3 by Koch et al., with the easily degradable COD measured by respiration . For modelling of EBPR the BioP-Module of Rieger et al., was used . Six German wastewater treatment plants were simulated during this research to test the existing set of parameters of the models on various large scale plants . It was shown that changes for nitrification and enhanced biological phosphorus removal in the set of biological parameters were necessary . Sensible parameters and recommended values are presented in this article . Apart from the values of the changed biological parameters, we will in our examination discuss the modelling of the different activated sludge systems and the influent fractioning of the COD . Two plants with simultaneous denitrification in the recirculation ditch (EBPR) are simulated, one with preliminary dentrification, one with intermittent denitrification (EBPR), one with cascade denitrification (EBPR), and one pilot plant according to the Johannesburg-process (EBPR) which was simulated over a period of three months.

Water Sci Technol, 2003, 47(11), 181 - 8
Nitrogen removal in industrial wastewater by nitration and denitration--3 years of experience; Degn Pedersen P et al.; CPKelco ApS, Denmark is the largest pectin plant in the world and the second largest refined carrageenan plant . The products are used for texturising purposes, primarily within the food industry, but also within the pharmaceutical industry . The products are extracted from imported natural raw materials, like dried citrus peel and special seaweed plants . In the production processes a considerable amount of water and energy are used . The excess water from the production processes is led to CPKelco's own WWTP, which is one of the largest industrial WWTPs in Denmark . In order to obtain higher process stability and lower energy consumption in the WWTP, CPKelco decided to change the nitrogen removal process from a conventional nitrification/denitrification process to a nitration/denitration process, which comprises an oxidation of ammonium to nitrite and a controlled reduction of nitrite to N2 . Theoretically this process will decrease the oxygen consumption for oxidation by 25% and the use of carbon source for the reduction will be decreased by 40% compared to the conventional process . This paper presents and discusses the experiences and results from three year's continuous operation of the nitration/denitration process in an activated sludge plant, and the overall performance results are discussed in relation to the previous results . Accordingly the implementation of the nitration/denitration process was done successfully, and today the plant operates with much higher process stability than obtained before, and even the most stringent effluent requirements for nitrogen can be obtained.

Water Sci Technol, 2003, 47(11), 173 - 80
Pre-nitrification by encapsulated nitrifiers--a possibility for self-sufficient energy operation of domestic WWTPs; Sievers M et al.; The overall energy consumption of domestic wastewater treatment plants (WWTPs) increases with treatment efficiency . Approximately 30 to 45 kWh per people equivalent and year is mostly necessary for advanced nitrogen and phosphorus removal, while the aeration contains the main part of approximately 60% . A new process using encapsulated nitrifiers on gel lens beads is introduced to overcome the high energy consumption of aeration . A more selective nitrification process was found at a nitrification rate of between 50 and 60 mg nitrogen per hour and litre reaction volume corresponding to a hydraulic retention time (HRT) of about 30 to 60 minutes while the soluble Chemical Oxygen Demand (COD) removal could be less than 30% depending on operational conditions of the bio-reactor . The latter enables internal use of wastewater's COD for a post denitrification . For the new process the energy consumption as well as total volume of bio-reactor are much less (approximately 30 to 50% for both) than conventional processes due to the low sludge age for COD and nitrate removal and the avoidance of internal wastewater recycle . Therefore, self-sufficient energy operation of domestic WWTPs operating with advanced treatment efficiency could become possible, if energy recovery by anaerobic sludge digestion is included.

Water Sci Technol, 2003, 47(11), 165 - 72
Molecular biological methods (DGGE) as a tool to investigate nitrification inhibition in wastewater treatment; Kreuzinger N et al.; Incomplete nitrification at an activated sludge plant for biological pre-treatment of rendering plant effluents led to a detailed investigation on the origin and solution of this problem . Preliminary studies revealed that an inhibition of ammonia oxidising microorganisms (AOM) by process waters of the rendering plant was responsible for the situation . We were able to show a correlation between the existence of specific AOM and nitrification capacity expressed as oxygen uptake rate for maximal nitrification (OURNmax) . Only Nitrosospira sp . was found in the activated sludge of the rendering plant and another industrial wastewater treatment plant with problems in nitrification, while reference plants without nitrification problems showed Nitrosomonas spp . as the predominant ammonia oxidising bacteria . By accompanying engineering investigations and experiments (cross-feeding experiments, operation of a two-stage laboratory plant) with molecular biological methods (DGGE--Denaturing Gradient Gel Electrophoresis) we were able to elaborate an applicable solution for the rendering plant . Laboratory experiments with a two-stage process layout finally provided complete nitrification overcoming the inhibiting nature of process waters from the rendering plant . DGGE analysis of the second stage activated sludge from the laboratory plant showed a shift in population structure from Nitrosospira sp . towards Nitrosomonas spp . simultaneous to the increase of nitrification capacity . Nitrification capacities comparable to full-scale municipal wastewater treatment plants could be maintained for more than two months . As the design of wastewater treatment plants for nitrification is linked to the growth characteristics of Nitrosomonas spp., established criteria can be applied for the redesign of the full-scale plant.

Water Sci Technol, 2003, 47(11), 157 - 63
Phased upgrading for nitrogen removal--a low cost approach; Solley D et al.; A phased approach has been adopted for upgrading the Luggage Point WWTP for nitrogen removal . Luggage Point WWTP (900,000 EP) is the largest plant operated by Brisbane Water . Management actions recommended by the South East Queensland Wastewater Management Strategy require the effluent total nitrogen levels to be reduced to less than 5 mg/L (50th percentile) by 2005 . Luggage Point WWTP originally featured primary settling and a completely nitrifying activated sludge process . Effluent total nitrogen levels from the plant averaged 27 mg/L . Characteristics of the wastewater are highly variable, with primary settled wastewater having a COD/BOD5 ratio averaging 2.5, a TKN/COD ratio averaging 0.12 and effluent non-ammonia TKN averaging 1.8 mg/L (but up to 5 mg/L) . The upgrade presented a substantial challenge, due to the limited available substrate for denitrification, a significant level of unbiodegradeable nitrogen and the low existing bioreactor HRT . The phased upgrading strategy was adopted to overcome these challenges most effectively and at low cost . The first stage of the upgrade included modifications to the existing plant infrastructure, without constructing new tankage . The existing bioreactors have been retrofitted using a five stage Bardenpho nutrient removal process, incorporating significant flexibility . The first phase upgrade has been commissioned and preliminary results indicate that the effluent total nitrogen has been reduced below the required first phase target of 8 mg/L . This represents a reduction of 3 tonnes of nitrogen per day entering Moreton Bay . The process is also operating with good stability and with excellent sludge settleability . The first phase of the upgrade will be completed for 25M AUS dollars, which represents a low cost of 28 dollars per equivalent person . Further upgrade works are likely to include separate treatment of the digested sludge dewatering centrate and advanced control of the biological process . The upgrade of Luggage Pt WWTP has shown that low effluent nitrogen can be achieved at low cost, through optimum utilisation of existing assets and a phased approach to modifications.

Water Sci Technol, 2003, 47(11), 153 - 6
Nitrification and denitrification using a single biofilter packed with granular sulfur; Kim JS et al.; This study was performed to develop a granular sulfur packed nitrification/denitrification process employing a uniquely designed single biofilter, which treated a relatively low carbon loaded domestic wastewater taken from a primary clarifier at a municipal wastewater treatment facility . The system was tested on varying experimental conditions, e.g . inflow flow, organic load and nitrogen load . Regardless of flow rate being increased, SS and COD was unvaryingly removed up to 90 and 80%, respectively . Moreover, TKN was also decomposed up to 90% . Increase in COD load gradually led to escalating level of non-biodegradable compounds observed in effluent . Nitrification was accomplished as high as 92%, whereas denitrification was achieved up to approximately 87% . For a while, nitrification and denitrification were observed at 0.65 and 0.55 kg/m3 x day, respectively . Eventually, T-N was decomposed as high as 46% . It was concluded that granular sulfur can be used for not only electron donor, but also for a media to properly treat low carbon loaded wastewater and to filter SS efficiently.

Water Sci Technol, 2003, 47(11), 129 - 36
Nitrification in biofilters under variable load and low temperature; Canler JP et al.; The evolution of European legislation has led to the rehabilitation of many wastewater treatment plants, sometimes through the installation of a biological complementary treatment stage . Among these sites, some plants in mountain areas are considering a biofiltration process . The design of such plants, especially for winter, appears to be tricky because of the very low influent temperature, the high performance requested for ammonia removal and the important and short term variations of the influent loads . The monitoring of a site during two consecutive winters has allowed us to study some aspects of the treatment . The major results are: a maximal nitrification capacity of about 0.59 kg of formed N-NO3- x m(-3) of material x d(-1) with an influent temperature around 7 degrees C at the plant inlet; a nitrifying biomass growth rate, expressed as nitrifying capacity increase, of 0.03 kg of N-NO3- x m(-3) of material x d(-2); quick and short terms load variations require a specific operation of the filters prior to the load increase, in order to grow enough active biomass to be able to treat the peak load immediately.

Water Sci Technol, 2003, 47(11), 115 - 22
Design of nutrient removal activated sludge systems; Manga J et al.; A mechanistic mathematical model for nutrient and organic matter removal was used to describe the behavior of a nitrification denitrification enhanced biological phosphorus removal (NDEBPR) system . This model was implemented in a user-friendly software DESASS (design and simulation of activated sludge systems) . A 484-L pilot plant was operated to verify the model results . The pilot plant was operated for three years over three different sludge ages . The validity of the model was confirmed with data from the pilot plant . Also, the utility of DESASS as a valuable tool for designing NDEBPR systems was confirmed.

Water Sci Technol, 2003, 47(11), 93 - 9
Partial nitrification in a high-load activated sludge system by biofilter backwash water recirculation; Melicz Z; The South-Budapest Municipal Wastewater Treatment Plant (SBWWTP) based on the high-load activated sludge process (AS) was upgraded into nutrient removal in 1998-1999 in Hungary . Biofor type nitrifying (NP) and denitrifying (DN) biofilters were implemented for nitrogen removal downstream of the (AS) stage in order to meet the required effluent standards characterized by 50 mgCOD l(-1), 10 mgBOI5 l(-1), 10 mgTN l(-1), 1 mgTP l(-1) and 35 mgTSS l(-1) . Phosphorus removal is obtained by chemical addition . The study presented sums up the performance of the upgraded plant throughout 25 months . Besides the efficient pre-denitrification obtained in the AS basin, significant ammonium oxidation was observed in the aerated zone, upon the introduction of recirculation of nitrate rich water and backwash water . The introduction of biofilter backwash water, containing nitrifying biomass, has generated significant ammonium conversion in the aerated basins, where nitrification was observed previously to a very limited extent . Process parameters of the AS stage were: aerobic sludge age of 1.5-2.0 days, 1.5 hours hydraulic retention time, specific sludge load of 1.1 kgCOD kgMLSS(-1) d(-1) . The nitrification in the AS tank has significantly reduced below 16 degrees C, however, denitrification efficiency was not as highly dependent upon temperature during the investigated period . The paper investigates the nitrogen balance of the plant in two aspects: (i) the effects of seeding on nitrification in the high load AS reactor and (ii) pre-denitrification potential in the anoxic zone of the AS tank of the pre-settled wastewater.

Water Sci Technol, 2003, 47(11), 85 - 92
Nitrification preservation in activated sludge during curative bulking chlorination; Cotteux E et al.; The bulking that occurs in biological wastewater treatment plants using activated sludge is very often controlled by the injection of sodium hypochlorite into the return activated sludge (RAS) stream . In the present study undertaken at two pilot plants fed with synthetic wastewater, the impact of the pass frequency of the sludge at the chlorine dosing point on the nitrifying flora is analysed . The pass frequency is one for the pilot plant 1 and two for the pilot plant 2 . A dose of chlorine of 4.85 +/- 0.05 g/kg/MLVSS per day was applied at both pilots . The preservative effect on nitrifying activity of the lowest concentration of chlorine at the dosing point and therefore of the highest pass frequency was evidenced . Among other tools, a simple method of measurement of the oxygen uptake rate enabled us to monitor the effect of chlorination on nitrification before recording an increase in the ammonia concentration in the bulking.

Water Sci Technol, 2003, 47(11), 77 - 84
Use of pH as fuzzy control parameter for nitrification under different alkalinity in SBR process; Peng YZ et al.; In order to achieve fuzzy control of nitrification in a Sequencing Batch Reactor (SBR) brewery wastewater was used as the substrate . The effect of alkalinity on pH variation during nitrification was systematically studied, at the same time the variations of DO and ORP were investigated . Alkalinity and pH of the wastewater were adjusted by adding sodium bicarbonate at five levels and sodium hydroxide at two levels . Unadjusted wastewater was also studied . According to the results, variation of pH could be divided into rising type and descending type . When bicarbonate alkalinity was deficient or sufficient, the descending type happened . If alkalinity was deficient, the pH decreasing rate got slower when nitrification nearly stopped; if alkalinity was sufficient, at the end of nitrification pH turned from decrease to increase . This was the most common situation and pH could be used to control the end of nitrification . When alkalinity was excessive, the rising type happened, pH was increasing at nearly a constant rate during and after nitrification and could not be used to control the nitrification time, but if the aeration rate was moderate DO could be used to control the nitrification time . This situation seldom happened . Therefore the variation of pH could not only be used to control the nitrification time but also to judge whether the alkalinity was enough or not . On the basis of this, the fuzzy controller of nitrification in SBR was constructed . When discussing the influence of pH on nitrification rate the composition and concentration of alkalinity must be considered or else the results may be incomprehensive . And to some extent the influence of alkalinity on nitrification rate was more important than pH.

Water Sci Technol, 2003, 47(11), 69 - 76
Fuzzy-control for improved nitrogen removal and energy saving in WWT-plants with pre-denitrification; Meyer U et al.; In the last few years, numerous studies were carried out, dealing with the application of fuzzy-logic to improve the control of the activated sludge process . In this paper, fuzzy-logic based control strategies for wastewater treatment plants with pre-denitrification are presented that should lead to better effluent quality and, in parallel, to a reduction of energy consumption . Extensive experimental investigations on a large scale pilot plant as well as simulation studies (ASM1 with SIMBA) were carried out in order to design, evaluate and compare different fuzzy-controllers with each other and with comparable conventional control systems . The fuzzy-controllers were designed as high-level controllers that determine the DO-setpoints in the aerated zones and the ratio between aerated and non-aerated zones . Conventional PI-controllers were used to maintain the DO-concentration at the set-point levels . The ammonia and nitrate concentration in the effluent and the ammonia load in the influent were considered as input variables for the different fuzzy-controllers . Compared to the operation with fixed nitrification/denitrification zones and constant DO concentrations, the required air-flow could be reduced up to 24% by using fuzzy-logic based control strategies . In comparison with a more advanced conventional control strategy (relay controller with two thresholds and the NH4-N concentration in the effluent as single control variable) a reduction of air-flow-rate up to 14% could be achieved . At the same time, NH4-N peaks in the effluent that are normally caused by peak flow conditions could be reduced significantly . The large scale experiments show that the fuzzy-controllers can be easily implemented in modern control and supervision systems and that the control characteristics can be followed and modified during operation . It therefore can be expected that the developed fuzzy-control systems will be accepted by the operating personnel in wastewater treatment plants.

Water Sci Technol, 2003, 47(11), 61 - 8
Induction of denitrification in a pilot-scale trickling filter by adding nitrate at high loading rate; Vanhooren H et al.; Oxygen transferred from the liquid phase into a biofilm can be used for aerobic degradation of organic matter and for nitrification . A second possible pathway for the removal of organic matter is denitrification in anoxic zones deeper in the biofilm . At high organic loading rates with insufficient oxygen supply to the biofilm, denitrification could be induced by providing the biofilm with external nitrate . This possibility was tested in a pilot-scale trickling filter by adding a pulse of nitrate to a highly loaded trickling filter . The experiment showed that denitrification can indeed be induced by adding nitrate at high loading conditions and that this way a considerably increased substrate removal capacity can be obtained . The fact that denitrification occurred was confirmed by the increased production of CO2 from bioconversion processes, without a major change of the O2 consumption . The simplified mixed-culture biofilm model developed by Rauch et al . was extended for the description of off-gas measurements and was able to describe the results of the experiment very well.

Water Sci Technol, 2003, 47(11), 45 - 51
Nitrification of high strength ammonia wastewater and nitrite accumulation characteristics; Kim DJ et al.; Biological nitrogen removal via the nitrite pathway in wastewater treatment is very important in saving the cost of aeration and as an electron donor for denitrification . Wastewater nitrification and nitrite accumulation were carried out in a biofilm airlift reactor with autotrophic nitrifying biofilm . The biofilm reactor showed almost complete nitrification and most of the oxidized ammonium was present as nitrite at the ammonium load of 1.5 to 3.5 kg N/m3 x d . Nitrite accumulation was stably achieved by the selective inhibition of nitrite oxidizers with free ammonia and dissolved oxygen limitation . Stable 100% conversion to nitrite could also be achieved even under the absence of free ammonia inhibition on nitrite oxidizers . Batch ammonium oxidation and nitrite oxidation with nitrite accumulating nitrifying biofilm showed that nitrite oxidation was completely inhibited when free ammonia is higher than 0.2 mg N/L . However, nitrite oxidation activity was recovered as soon as the free ammonia concentration was below the threshold level when dissolved oxygen concentration was not the limiting factor . Fluorescence in situ hybridization analysis of cryosectioned nitrite accumulating nitrifying biofilm showed that the beta-subclass of Proteobacteria, where ammonia oxidizers belong, was distributed outside the biofilm whereas the alpha-subclass of Proteobacteria, where nitrite oxidizers belong, was found mainly in the inner part of the biofilm . It is likely that dissolved oxygen deficiency or limitation in the inner part of the nitrifying biofilm, where nitrite oxidizers exist, is responsible for the complete shut down of the nitrite oxidizers activity under the absence of free ammonia inhibition.

Water Sci Technol, 2003, 47(11), 31 - 6
The ScanDeNi process could turn an existing under-performing activated sludge plant into an asset; Rosen S et al.; With tightening up of effluent discharge standards from wastewater treatment facilities, many plants are facing costly augmentations and in many cases completely new plants will have to be constructed . The ScanDeNi process was developed in Sweden for increased nitrogen removal at the Vasteras Sewage Treatment Plant (STP), 125,000 p.e . near Stockholm, and can be described as a modified contact stabilisation process with pre-denitrification and a selector stage for nitrification . The STP was upgraded at a cost of some 25 Mill . SEK (2.5 Mill . USD) . It has been successfully in operation since 1998, exceeding all expectations . The process is showing the following major advantages . 25-35% less volume for the same Sludge Retention Time (SRT) and secondary sedimentation sludge load, compared to conventional pre-denitrification; or a 25-35% higher load can be applied within the same volume with the same removal efficiencies . The selector mechanism appears to be not limited to the nitrifying bacteria alone . Other microorganisms appear to be responsible for the reduction of surface active matter from the return activated sludge (RAS), as well as in the reject stream from sludge dewatering, resulting in an increase in alpha-values of approximately 50% . Due to the high alpha-values less aeration is required, resulting in significant operating cost savings . 'Automatic' creation of anaerobic conditions, enabling biological phosphorus removal . Whilst rarely a concern in warmer climates, BNR plants in cold climates in winter often lose their capacity to nitrify . The Vasteras STP has consistently maintained excellent effluent quality even with effluent temperatures as low as 7 degrees C, and at an SRT of some 7-9 days, proving the effectiveness of the nitrifier selector . The ScanDeNi process could offer excellent effluent discharge standards (T-N < 10 mg/L, T-P < 0.5 mg/L) in smaller tank volumes and at a significantly lower operating cost, compared to conventional pre-denitrification systems.

Water Sci Technol, 2003, 47(11), 23 - 9
Quantitative estimation of the role of denitrifying phosphate accumulating organisms in nutrient removal; Shoji T et al.; It has been reported that a proportion of polyphosphate-accumulating organisms (PAOs) can denitrify or utilize nitrate as an electron acceptor . The usage of denitrifying-PAO (DN-PAO) can relieve the competition for COD between denitrification and phosphorus removal because they can treat nitrate and phosphate by using the same carbon source . To effectively use DN-PAO for biological nutrient removal (BNR), a new system was proposed in which an anaerobic phase is placed at the influent end, followed by he anoxic and external nitrification phase . In this study, the lab-scale proposed system (A2N system) was operated with a municipal wastewater 1) to confirm stable settlement of DN-PAO in the proposed system, 2) to quantitatively estimate the fraction of different groups of organisms like denitrifiers without polyphosphate accumulating capability, aerobic-PAO and DN-PAO and 3) to estimate the advantages of DN-PAO's presence in the system . Moreover, batch experiments in which anoxic and aerobic phosphate uptake rates (PUR) were measured were also carried out . The activity of DN-PAO was observed throughout the experimental period by the batch experiment . From the results of the calculation of COD utilized by each group of organisms, it was concluded that the proposed system could accumulate much more PAO (as DN-PAO) than conventional BNR systems . Moreover, they were responsible for both EBPR and denitrification.

Water Sci Technol, 2003, 47(11), 17 - 22
Anoxic phosphorus removal by denitrifying heterotrophic bacteria; Lacko N et al.; The unexplained occurrence of anoxic phosphorus (P) accumulation has largely hampered modeling of nitrification denitrification biological excess P removal (NDBEPR) systems . The aim of this study was, therefore, to isolate and identify denitrifying-P accumulating heterotrophic bacteria (DPBs) from a NDBEPR system in order to evaluate anoxic P accumulation and the specific mechanisms involved . Results of the study showed various heterotrophic bacteria to be capable of anoxic P accumulation utilising nitrate (NO3) as electron acceptor . While Pseudomonas spp . predominated, Serratia spp . and Vibrio spp . demonstrated the most efficient anoxic P accumulation with 7.10 and 7.29 mgPO4-P/L removal, respectively, at an initial NO3 concentration of 13.54 mgNO3-N/L and P concentration of 16.34 mgPO4-P/L . Weaker DPBs were also identified which were only capable of accumulating small amounts of P at low initial P and NO3 concentrations due to weak denitrification capacity . Anoxic P release was also observed due to the presence of acetate.

Biotechnol Bioeng, 2003 Sep 20, 83(6), 706 - 20
Simultaneous nitrification and denitrification using stored substrate (PHB) as the electron donor in an SBR; Third KA et al.; The potential for PHB (poly-beta-hydroxybutyrate) to serve as the electron donor for effective simultaneous nitrification and denitrification (SND) was investigated in a 2-L sequencing batch reactor (SBR) using a mixed culture and acetate as the organic substrate . During the feast period (i.e., acetate present), heterotrophic respiration activity was high and nitrification was prevented due to the inability of nitrifying bacteria to compete with heterotrophs for oxygen . Once acetate was depleted the oxidation rate of PHB was up to 6 times slower than that of soluble acetate and nitrification could proceed due to the decreased competition for oxygen . The slow nature of PHB degradation meant that it was an effective substrate for SND, as it was oxidised at a similar rate to ammonium and was therefore available for SND throughout the entire aerobic period . The percentage of nitrogen removed via SND increased at lower DO concentrations during the famine period, with up to 78% SND achieved at a DO concentration of 0.5 mg L(-1) . However, the increased percentage of SND at a low DO concentration was compromised by a 2-times slower rate of nitrogen removal . A moderate DO concentration of 1 mg L(-1) was optimal for both SND efficiency (61%) and rate (4.4 mmol N x Cmol x(-1) x h(-1)) . Electron flux analysis showed that the period of highest SND activity occurred during the first hour of the aerobic famine period, when the specific oxygen uptake rate (SOUR) was highest . It is postulated that a high SOUR due to NH(4) (+) and PHB oxidation decreases oxygen penetration into the floc, creating larger zones for anoxic denitrification . The accumulation of nitrate towards the end of the SND period showed that SND was finally limited by the rate of denitrification . As PHB degradation was found to follow first-order kinetics (df(PHB)/dt = -0.19 x f(PHB)), higher PHB concentrations would be expected to drive SND faster by increasing the availability rate of reducing power and reducing penetration of oxygen into the floc, due to the corresponding increased SOUR . Process control techniques to accumulate higher internal PHB concentrations to improve PHB-driven SND are discussed .

Isotopes Environ Health Stud, 2003 Jun, 39(2), 141 - 58
Nutrient cycling responses to fire frequency in the Kruger National Park (South Africa) as indicated by stable isotope analysis; Aranibar JN et al.; Fires, which are an intrinsic feature of southern African ecosystems, produce biogenic and pyrogenic losses of nitrogen (N) from plants and soils . Because of the long history of fires in these savannas, it was hypothesized that N2 fixation by legumes balances the N losses caused by fires . In this study, the N2 fixation activity of woody legumes was estimated by analyzing foliar delta15N and proportional basal area of N2 fixing species along experimental fire gradients in the Kruger National Park (South Africa) . In addition, soil carbon (C) and N pools, foliar phosphorus (P) and gross N mineralization and nitrification rates were measured, to indicate the effects of fires on nutrient stocks and the possible N cycling processes modified by fires . Although observations of increased soil C/N and mineralization rates in frequently burned plots support previous reports of N losses caused by fires, soil %N did not decrease with increasing fire frequency (except in 1 plot), suggesting that N losses are replenished in burned areas . However, relative abundance and N2 fixation of woody legumes decreased with fire frequency in two of the three fire gradients analyzed, suggesting that woody legume N2 fixation is not the mechanism that balances N losses . The relatively constant %N along fire gradients suggests that these ecosystems have other mechanisms to balance the N lost by fires, which could include inputs by atmospheric deposition and N2 fixation by forbs, grasses and soil cyanobacteria . Soil isotopic signatures have been previously used to infer patterns of fire history . However, the lack of a relationship between soil delta15N and fire frequency found in this study indicates that the effects of fires on ecosystem delta15N are unpredictable . Similar soil delta15N along fire gradients may reflect the contrasting effects of increased N gaseous emissions (which increases delta15N) and N2 fixation other than that associated with woody legumes (which lowers delta15N) on isotopic signatures.

Environ Microbiol, 2003 Aug, 5(8), 691 - 705
Effects of temperature and fertilizer on activity and community structure of soil ammonia oxidizers; Avrahami S et al.; We investigated the effect of temperature on the activity of soil ammonia oxidizers caused by changes in the availability of ammonium and in the microbial community structure . Both short (5 days) and long (6.5, 16 and 20 weeks) incubation of an agricultural soil resulted in a decrease in ammonium concentration that was more pronounced at temperatures between 10 and 25 degrees C than at either 4 degrees C or 30-37 degrees C . Consistently, potential nitrification was higher between 10 and 25 degrees C than at either 4 degrees C or 37 degrees C . However, as long as ammonium was not limiting, release rates of N2O increased monotonously between 4 and 37 degrees C after short-term temperature adaptation, with nitrification accounting for about 35-50% of the N2O production between 4 and 25 degrees C . In order to see whether temperature may also affect the community structure of ammonia oxidizers, we studied moist soil during long incubation at low and high concentrations of commercial fertilizer . The soil was also incubated in buffered (pH 7) slurry amended with urea . Communities of ammonia oxidizers were assayed by denaturant gradient gel electrophoresis (DGGE) of the amoA gene coding for the alpha subunit of ammonia monooxygenase . We found that a polymerase chain reaction (PCR) system using a non-degenerated reverse primer (amoAR1) gave the best results . Community shifts occurred in all soil treatments after 16 weeks of incubation . The community shifts were obviously influenced by the different fertilizer treatments, indicating that ammonium was a selective factor for different ammonia oxidizer populations . Temperature was also a selective factor, in particular as community shifts were also observed in the soil slurries, in which ammonium concentrations and pH were better controlled . Cloning and sequencing of selected DGGE bands indicated that amoA sequences belonging to Nitrosospira cluster 1 were dominant at low temperatures (4-10 degrees C), but were absent after long incubation at low fertilizer treatment . Sequences of Nitrosospira cluster 9 could only be detected at low ammonium concentrations, whereas those of Nitrosospira cluster 3 were found at most ammonium concentrations and temperatures, although individual clones of this cluster exhibited trends with temperature . Obviously, ammonia oxidizers are able to adapt to soil conditions by changes in the community structure if sufficient time (several weeks) is available.

Environ Technol, 2003 Jun, 24(6), 767 - 77
Cold weather nitrogen removal deficiencies of aerated lagoons; Van Dyke S et al.; Aerated lagoons are widely used throughout the state of Iowa, USA by small communities, due to their relatively low costs and maintenance requirements . Although aerated lagoons were not initially designed for ammonia removal many of these facilities have been assigned effluent ammonia limits in recent years Since widespread monitoring began, it has been found that aerated lagoons tend to have problems with high effluent ammonia concentrations during the winter and early spring . This study collected and analyzed data from 10 aerated lagoon facilities in central Iowa to determine the factors governing cold weather nitrogen removal in aerated lagoons . The factors found to affect performance were temperature and detention time . None of the following factors were found to significantly affect performance: dissolved oxygen (DO), pH, CBOD5 loading, total nitrogen loading, aerated cell depth and design standards governing the design . It should be noted that DO and pH were relatively constant and generally favorable for nitrification . Increased mixing energy was correlated with poorer performance, but this correlation may not be correct as the expected benefit of more intense mixing conditions may masked by the overwhelming benefit of long detention times.

Water Res, 2003 Sep, 37(15), 3561 - 8
Organic matter removal in combined anaerobic-aerobic fixed-film bioreactors; Del Pozo R et al.; A combination of two fixed-film bioreactors (FFB) with arranged media, the first anaerobic and the second aerobic, connected in series with recirculation was fed continuously for 133 days with wastewater from a poultry slaughterhouse . Oxidation of the organic carbon compounds and nitrification were carried out in the aerobic FFB and methanogenesis and denitrification were performed in the anaerobic FFB . The average organic loading rate was 0.39 kg COD/m3d and 92% removal efficiencies of organic matter were achieved . COD-removal occurred mainly in the anaerobic FFB, increasing when the recirculation ratio rose from 1 to 6 due to the increase in the anoxic denitrification . The influence of the C/N ratio of the raw wastewater over the proportion in which the COD-removal was carried out by oxidation in the aerobic FFB, methanogenesis or denitrification in the anaerobic FFB was studied . When the volume of the aerobic FFB became smaller than that of the anaerobic one the fraction of organic matter removed in the anaerobic FFB increased, but also the ratio between the respective volumetric rates (rCODan/rCODae) increased . High recirculation and low C/NO-N ratio in the anaerobic FFB feed favoured the denitrification to the detriment of the methanogenic process . Regarding nitrogen removal for nitrogen applied loads around 0.064 kg TKN/m3d the removal efficiency was of 95%, which decreased to 84% for 0.14 kg TKN/m3d . The stability of the nitrification process was the controlling factor of the nitrogen removal . High ammonia concentration caused by high recirculation ratio, specially when the aerobic FFB volume was smaller, caused nitrification inhibition which destabilised the system.

Water Sci Technol, 2003, 47(10), 147 - 53
Application of piggery waste to nightsoil plant towards sustainable development; Eum Y et al.; Organic loads have been significantly reduced in nightsoil plants along with the employment of sewage treatment plants . Nightsoil consisting of 10% septage and showing higher ratios of alkalinity and carbon to nitrogen helped nitrification and denitrification for those combined plants with week piggery waste . However, alkalinity and carbon addition was necessary with the weak nightsoil consisting of 80% septage when the combined influent was less than 21 g/L COD . The piggery waste could be applied at a rate of 0.5 kgTKN/oxic m3/d, but the organic load should be limited to 0.7 kgCOD/m3/d with strong piggery waste during summer in order not to exceed the reactor temperature higher than 35 degrees C.

Chemosphere, 2003 Sep, 52(8), 1287 - 93
Effect of ammonium and oxygen on methane and nitrous oxide fluxes across sediment-water interface in a eutrophic lake; Liikanen A et al.; Eutrophication has decreased the O(2) content and increased the NH(4)(+) availability in freshwaters . These changes may affect carbon and nitrogen transformation processes and the production of CH(4) and N(2)O, which are important greenhouse gases . We studied release of CH(4) and N(2)O from a eutrophic lake sediment under varying O(2) and NH(4)(+) conditions . Intact sediment cores were incubated in a laboratory microcosm with a continuous anoxic or oxic water flows containing 0, 50, 500, 5,000, or 15000 microM NH(4)(+) . With the anoxic flow, the sediment released CH(4), up to 7.9 mmol m(-2)d(-1) . With the oxic flow, the CH(4) emissions were small indicating limited CH(4) production and/or effective CH(4) oxidation . Addition of NH(4)(+) did not affect sediment CH(4) release, evidence that the CH(4) oxidizing bacteria were not disturbed by the extra NH(4)(+) . The release of N(2)O from the sediment was highest, up to 7.6 micromol m(-2)d(-1), with the oxic flow without NH(4)(+) addition . Oxygen was the key factor regulating the production of NO(3)(-), which enabled denitrification and production of N(2)O . However, the highest NH(4)(+) addition increased nitrification and associated O(2) consumption causing a decrease in sediment O(2) content and in accumulation of NO(3)(-) and N(2)O, which were effectively reduced to N(2) in denitrification . In summary, sediment CH(4) and N(2)O dynamics are regulated more by the availability of O(2) than extra NH(4)(+) . Anoxia in eutrophic lakes favouring the CH(4) production, is the major contributor to the atmospheric consequences of water eutrophication.

Water Environ Res, 2003 May-Jun, 75(3), 225 - 31
A comparative pilot-scale study of the performance of conventional activated sludge and membrane bioreactors under limiting operating conditions; Aguilera Soriano G et al.; The behavior of the conventional activated-sludge (CAS) process was compared to that of the membrane bioreactor (MBR) process under limiting operating conditions; that is, at a low solids retention time (SRT) and hydraulic residence time (HRT) . The SRT was varied from 2 to 7 days, and the HRT ranged from 5 to 18 hours . The comparison was carried out in terms of nitrification and denitrification kinetics and in terms of the carbon and nitrogen removal performance of these processes . The study involved two pilot-scale units: a CAS unit with a 9-m3 aeration tank and a 225-L MBR . Both of these units were installed and run under real process conditions at a wastewater treatment plant in Evry, France . In the case of the MBR process, the specific nitrification rates, rN, and the specific denitrification rates, rDN, increased as SRT was reduced from 6.5 days to 2 days . This trend was reversed and the rN and rDN decreased only when the HRT was reduced to 5 hours . A similar behavior was observed in the case of the CAS process, although rN and rDN increased only when the SRT was reduced to as low as 4 days; below this value, the rates dropped considerably . It seems that the presence of the membrane renders the MBR more robust by preventing the washout of nitrifiers at low SRT and HRT . Besides the structure and size distribution of the MBR, flocs are more favorable to intraparticle mass transfer than those of the CAS process and could explain the higher nitrification kinetics observed with the MBR process . In all cases, the carbon and nitrogen removal performance of the MBR process was better than that of the CAS system.

Water Environ Res, 2003 May-Jun, 75(3), 205 - 15
Linking nitrifying biofilm structure and function through fluorescent in situ hybridization and evaluation of nitrification capacity; Biesterfeld S et al.; Fluorescent in situ hybridization (FISH) was used to quantify the ammonia-oxidizing populations within intact biofilm samples collected from a full-scale nitrifying trickling filter (NTF) . Ammonia, nitrite, and nitrate concentrations were measured for aqueous samples taken in conjunction with biofilm samples at multiple filter depths . The ammonia removal capability of collected biofilms was evaluated by transferring the biofilms to laboratory batch reactors . Nitrate plus nitrite generation rates were calculated for the full-scale NTF and for the bench-scale reactors . Correlation coefficients for individual sampling events, calculated by simple linear regression of FISH signal area and nitrate plus nitrite generation rates for the full-scale NTF, ranged from -0.882 to 0.984 . Correlation coefficients obtained for FISH signal area and nitrate plus nitrite generation rates for the bench-scale reactors ranged from 0.853 to 0.994 when using probe Nso190 and from 0.919 to 0.986 when using probe Neu23a . Occasional differences between the number of ammonia-oxidizing bacteria quantified by the probe Nso190 versus the NEU23a probe with depth suggest that genera other than Nitrosomonas are present in the NTF.

Water Environ Res, 2003 May-Jun, 75(3), 196 - 204
Effect of alkalinity type and concentration on nitrifying biofilm activity; Biesterfeld S et al.; The effect of alkalinity on nitrifying biofilm activity was determined by collecting 21-day-old biofilm samples from the top of a full-scale nitrifying trickling filter and evaluating bench-scale nitrate plus nitrite generation rates at (1) various initial carbonate alkalinity concentrations and (2) with four types of available alkalinity: carbonate only, phosphate only, phosphate plus hydroxide, and phosphate plus carbonate . Initial carbonate alkalinity concentrations were varied between 308 and 20 mg/L as calcium carbonate (CaCO3) . Ammonia, nitrite, and nitrate concentrations were measured at time zero, 90 minutes, 180 minutes, and 270 minutes . Generation rates in grams of nitrogen per square meter per day were calculated for each time period and normalized against dry-weight biomass . Generation rates were impaired at initial carbonate alkalinity concentrations of 40 mg/L and lower (as CaCO3) and were unaffected at concentrations of 45 mg/L and greater . For reactor runs with different alkalinity types, ammonia, nitrite, and nitrate concentrations were measured at time zero and at 375 minutes . The type of alkalinity, carbonate versus phosphate, affected nitrification rates . When the carbonate alkalinity was less than 45 mg/L, nitrification rates were impaired regardless of the total alkalinity concentration . This effect seems to be independent of pH for the range of 6.92 to 7.99 evaluated here . This suggests that in addition to neutralizing the acid generated by the nitrification process, a minimum level of carbonate alkalinity is necessary to meet the ammonia-oxidizer's inorganic carbon requirement for cellular synthesis and growth.

J Hazard Mater, 2003 Jun 27, 100(1-3), 271 - 83
The inhibitory effects of heavy metals and organic compounds on the net maximum specific growth rate of the autotrophic biomass in activated sludge; Juliastuti SR et al.; A respirometry technique can be applied as an effective method to determine the net maximum specific growth rate of autotrophic biomass under both normal conditions and when inhibition occurs . The net maximum specific growth rate of uninhibited autotrophic biomass, expressed as (mu(A)-b(A)), is approximately 0.8 per day {Proceeding of the International Congress on CHISA, Prague, 2002, p . 1} . Several heavy metals and organic compounds have inhibitory effects . Copper (Cu(2+)) has stronger inhibitory effects than zinc (Zn(2+)), and inhibits the nitrification process by 50% at 0.08 mg/l {(mu(A)-b(A)) = 0.4 per day}, while the same concentration of Zn(2+) establishes 12% inhibition only {(mu(A)-b(A)) = 0.75 per day} . Inhibition with Cu(2+) starts at concentrations above 0.05 mg/l, while this is above 0.3mg/l for Zn(2+) . The inhibition of the nitrification process is complete at 1.2mg/l for both Cu(2+) and Zn(2+) . Among the selected organic compounds tested n the experiments, the degree of inhibition decreases as follow: chlorobenzene>trichloroethylene (TCE)>phenol>ethylbenzene . Chlorobenzene already inhibits the autotrophic biomass at 0.25 mg/l . The nitrification process is totally inhibited by adding 0.75 mg/l of chlorobenzene . TCE has a less inhibitory effect on the nitrification process and 50% inhibition is noticed at 0.75 mg/l TCE . The nitrification process is totally inhibited at 1mg/l TCE . Phenol inhibits the nitrification for 50% at 3 mg/l . The inhibitory effect of phenol is almost constant in the range 4-10 mg/l and complete inhibition is reached at 50 mg/l . The inhibitory effect of ethylbenzene is 50% at 8 mg/l and the autotrophic biomass is totally inhibited at 50 mg/l.Experimental findings are compared with literature data, which generally and significantly overestimate the inhibition threshold concentrations.

Water Res, 2003 Aug, 37(14), 3445 - 51
Coupled BAS and anoxic USB system to remove urea and formaldehyde from wastewater; Campos JL et al.; Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a biofilm airlift suspension (BAS) reactor and an anoxic upflow sludge blanket (USB) reactor . The anoxic USB reactor was used to carry out denitrification and urea hydrolysis, while the BAS reactor was used to carry out nitrification . In a first step, individual experiments were carried out to investigate the effects of both compounds on the nitrifying and denitrifying biomass . The BAS reactor was fed with a synthetic medium containing 500 mg N-NH4(+)l(-1) and 100mg N-urea l(-1), that were added continuously to this medium . Neither urea hydrolysis nor inhibition of nitrification was observed . Nitrification efficiency decreased when formaldehyde was fed during shocks at concentrations of 40, 80 and 120 mg C-formaldehyde l(-1) . The anoxic USB reactor was fed with a synthetic medium containing nitrate, formaldehyde and urea . Concentrations of formaldehyde in the reactor of 100-120 mg C-formaldehyde l(-1) caused a decrease in the denitrification and urea hydrolysis rates . In a second step, the coupled system was operated at recycling ratios (R) of 3 and 9 . Fed C/N ratios of 0.58, 1.0 and 1.5 g C-formaldehyde g(-1) N-NH4(+) were used for every recycling ratio . The maximum nitrogen removal percentages were achieved at a C/N ratio of 1.0 g C-formaldehyde g(-1) N-NH4(+) for both recycling ratios . A fed C/N ratio of 1.5 g C-formaldehyde g(-1) N-NH4(+) caused a decrease in the efficiency of the system with respect to nitrogen removal, due to the presence of formaldehyde in the BAS reactor, which decreased the nitrification . Formaldehyde was completely removed in the BAS reactor and a heterotrophic layer formed around the nitrifying biofilm.

Water Res, 2003 Aug, 37(14), 3430 - 44
Modelling biological nutrient removal activated sludge systems - a review; Hu ZR et al.; The external nitrification (EN) biological nutrient removal (BNR) activated sludge (ENBNRAS) system shows considerable promise for full-scale implementation . As an aid for this implementation, a mathematical simulation model would be an invaluable tool . To develop such a model, a study was conducted to select the most suitable simulation model to serve as a starting point for further development . For this, the existing available simulation models for BNRAS systems are compared with one another and evaluated against experimental observations in the literature and on ENBNRAS systems . One process immediately apparent to be crucially important is the anoxic growth of phosphorus accumulating organisms (PAOs), with associated PAO denitrification and anoxic P uptake for polyP formation . These linked processes are lacking in the earlier kinetic simulation models for BNRAS systems, which were based on aerobic PAO growth and P uptake only, but have been incorporated into the more recent kinetic models . This provides a substantive body of information on modelling this aspect . Other processes of significance identified to require consideration are anaerobic slowly biodegradable COD (SBCOD) hydrolysis to readily biodegradable COD (RBCOD), and COD loss . Both processes have significant impact on the predicted BEPR performance . Due to the uncertainties associated with the mechanisms and quantification of these two processes, it is concluded that the most extensively validated kinetic simulation model should be selected for development, and that the omissions in this model should be addressed progressively, using the relevant information drawn from the existing models, the literature and observations on ENBNRAS systems.

Ying Yong Sheng Tai Xue Bao, 2003 Feb, 14(2), 223 - 6
{Effect of prescribed burning on grassland nitrogen gross mineralization and nitrification}; Li Y et al.; The seasonal dynamics of nitrogen gross mineralization, nitrification, and mineral nitrogen consumption rates in burned and unburned Leymus chinensis grasslands were studied with 15N pool dilution technique . The results indicated that the gross mineralization and nitrification rates in burned area were higher than those in unburned area in April and May, and lower than those in unburned area in September . NH4(+)-N consumption rates were higher than unburned area in April and May, and lower in September . NO3(-)-N consumption rates were higher than control in April and May, and lower than control in July and September . The NH4(+)-N concentrations were higher in burned area in April, May and July, and no difference in September . NO3(-)-N concentrations were no difference between burned and unburned areas in April and May, and higher in burned areas in July and September.

Biotechnol Bioeng, 2003 Sep 5, 83(5), 604 - 7
Effect of oxygen concentration on nitrification and denitrification in single activated sludge flocs; Satoh H et al.; Simultaneous nitrification and denitrification (SND) was investigated in the single aeration tank of a municipal wastewater treatment plant . Microelectrode measurements and batch experiments were performed to test for the presence of SND . Microelectrodes recorded the presence of O(2) concentration gradients in individual activated sludge flocs . When the O(2) concentration in the bulk liquid was <45 microM, anoxic zones were detected within flocs with a larger diameter (approximately 3000 microm) . The O(2) penetration depth in the floc was found to be dependent on the O(2) concentration in the bulk liquid . Nitrification was restricted to the oxic zones, whereas denitrification occurred mainly in the anoxic zones . The nitrification rate of the activated sludge increased with increasing O(2) concentration in the bulk liquid, up to 40 microM, and remained constant thereafter . SND was observed in the aerated activated sludge when O(2) concentration was in the range of 10 to 35 microM .

Ann Chim, 2003 Apr, 93(4), 353 - 62
Nitrogen, phosphorus and organics removal in two vertical flow experimental wetlands receiving pretreated municipal wastewater; Berzero A et al.; Pollutants removal in two vertical flow experimental wetlands receiving pre-treated municipal wastewater was investigated . Laboratory investigations using microcosms were also carried out in order to identify key processes regulating pollutants removal . Results obtained from experimental wetlands seem to confirm the ability of a single stage installation, where nitrification and denitrification processes are jointly optimised using a gravel medium, always wet but not saturated with water . Results obtained from microcosm investigations show the prominent role of O2 supply, of microbial activity and of bio-available C from vegetal metabolism in the nitrogen removal.

Isotopes Environ Health Stud, 2003 Mar, 39(1), 41 - 52
Tree species of the Central Amazon and soil moisture alter stable isotope composition of nitrogen and oxygen in nitrous oxide evolved from soil; Menyailo OV et al.; The use of stable isotopes of N and O in N2O has been proposed as a way to better constrain the global budget of atmospheric N2O and to better understand the relative contributions of the main microbial processes (nitrification and denitrification) responsible for N2O formation in soil . This study compared the isotopic composition of N2O emitted from soils under different tree species in the Brazilian Amazon . We also compared the effect of tree species with that of soil moisture, as we expected the latter to be the main factor regulating the proportion of nitrifier- and denitrifier-derived N2O and, consequently, isotopic signatures of N2O . Tree species significantly affected delta15N in nitrous oxide . However, there was no evidence that the observed variation in delta15N in N2O was determined by varying proportions of nitrifier- vs . denitrifier-derived N2O . We submit that the large variation in delta15N-N2O is the result of competition between denitrifying and immobilizing microorganisms for NO3(-) . In addition to altering delta15N-N2O, tree species affected net rates of N2O emission from soil in laboratory incubations . These results suggest that tree species contribute to the large isotopic variation in N2O observed in a range tropical forest soils . We found that soil water affects both 15N and 18O in N2O, with wetter soils leading to more depleted N2O in both 15N and 18O . This is likely caused by a shift in biological processes for 15N and possible direct exchange of 18O between H2O and N2O.

J Environ Qual, 2003 May-Jun, 32(3), 1144 - 9
Denitrification potential in urban riparian zones; Groffman PM et al.; Denitrification, the anaerobic microbial conversion of nitrate (NO3-) to nitrogen (N) gases, is an important process contributing to the ability of riparian zones to function as "sinks" for NO3- in watersheds . There has been little analysis of riparian zones in urban watersheds despite concerns about high NO3- concentrations in many urban streams . Vegetation and soils in urban ecosystems are often highly disturbed, and few studies have examined microbial processes like denitrification in these ecosystems . In this study, we measured denitrification potential and a suite of related microbial parameters (microbial biomass carbon {C} and N content, potential net N mineralization and nitrification, soil inorganic N pools) in four rural and four urban riparian zones in the Baltimore, MD metropolitan area . Two of the riparian zones were forested and two had herbaceous vegetation in each land use context . There were few differences between urban and rural and herbaceous and forest riparian zones, but variability was much higher in urban than rural sites . There were strong positive relationships between soil moisture and organic matter content and denitrification potential . Given the importance of surface runoff in urban watersheds, the high denitrification potential of the surface soils that we observed suggests that if surface runoff can be channeled through areas with high denitrification potential (e.g., stormwater detention basins with wetland vegetation), these areas could function as important NO3- sinks in urban watersheds.

ScientificWorldJournal, 2001 Oct 16, 1 Suppl 2, 505 - 13
Factors influencing spatial variability in nitrogen processing in nitrogen-saturated soils; Gilliam FS et al.; Nitrogen (N) saturation is an environmental concern for forests in the eastern U.S . Although several watersheds of the Fernow Experimental Forest (FEF), West Virginia exhibit symptoms of N saturation, many watersheds display a high degree of spatial variability in soil N processing . This study examined the effects of temperature on net N mineralization and nitrification in N-saturated soils from FEF, and how these effects varied between high N-processing vs . low N-processing soils collected from two watersheds, WS3 (fertilized with {NH4}2SO4) and WS4 (untreated control) . Samples of forest floor material (O1 horizon) and mineral soil (to a 5-cm depth) were taken from three subplots within each of four plots that represented the extremes of highest and lowest rates of net N mineralization and nitrification (hereafter, high N and low N, respectively) of untreated WS4 and N-treated WS3: control/low N, control/high N, N-treated/low N, N-treated/high N . Forest floor material was analyzed for carbon (C), lignin, and N . Subsamples of mineral soil were extracted immediately with 1 N KCl and analyzed for NH4+ and NO3- to determine preincubation levels . Extracts were also analyzed for Mg, Ca, Al, and pH . To test the hypothesis that the lack of net nitrification observed in field incubations on the untreated/low N plot was the result of absence of nitrifier populations, we characterized the bacterial community involved in N cycling by amplification of amoA genes . Remaining soil was incubated for 28 d at three temperatures (10, 20, and 30 degrees C), followed by 1 N KCl extraction and analysis for NH4+ and NO3- . Net nitrification was essentially 100% of net N mineralization for all samples combined . Nitrification rates from lab incubations at all temperatures supported earlier observations based on field incubations . At 30 degrees C, rates from N-treated/high N were three times those of N-treated/low N . Highest rates were found for untreated/high N (two times greater than those of N-treated/high N), whereas untreated/low N exhibited no net nitrification . However, soils exhibiting no net nitrification tested positive for presence of nitrifying bacteria, causing us to reject our initial hypothesis . We hypothesize that nitrifier populations in such soil are being inhibited by a combination of low Ca to Al ratios in mineral soil and allelopathic interactions with mycorrhizae of ericaceous species in the herbaceous layer.

ScientificWorldJournal, 2001 Oct 30, 1 Suppl 2, 108 - 13
The influence of mineral fertilizer combined with a nitrification inhibitor on microbial populations and activities in calcareous Uzbekistanian soil under cotton cultivation; Egamberdiyeva D et al.; Application of fertilizers combined with nitrification inhibitors affects soil microbial biomass and activity . The objective of this research was to determine the effects of fertilizer application combined with the nitrification inhibitor potassium oxalate (PO) on soil microbial population and activities in nitrogen-poor soil under cotton cultivation in Uzbekistan . Fertilizer treatments were N as urea, P as ammophos, and K as potassium chloride . The nitrification inhibitor PO was added to urea and ammophos at the rate of 2% . Three treatments--N200 P140 K60 (T1), N200 PO P140 K60 (T2), and N200 P140 PO K60 (T3) mg kg(-1) soil--were applied for this study . The control (C) was without fertilizer and PO . The populations of oligotrophic bacteria, ammonifying bacteria, nitrifying bacteria, denitrifying bacteria, mineral assimilating bacteria, oligonitrophilic bacteria, and bacteria group Azotobacter were determined by the most probable number method . The treatments T2 and T3 increased the number of oligonitrophilic bacteria and utilization mineral forms of nitrogen on the background of reducing number of ammonifying bacteria . T2 and T3 also decreased the number of nitrifying bacteria, denitrifying bacteria, and net nitrification . In conclusion, our experiments showed that PO combined with mineral fertilizer is one of the most promising compounds for inhibiting nitrification rate, which was reflected in the increased availability and efficiency of fertilizer nitrogen to the cotton plants . PO combined with mineral fertilizer has no negative effects on nitrogen-fixing bacteria Azotobacter and oligo-nitrophilic bacteria.

ScientificWorldJournal, 2001 Nov 27, 1 Suppl 2, 844 - 51
Prevention and control of losses of gaseous nitrogen compounds in livestock operations: a review; Jongebreur AA et al.; Nitrogen (N) losses from livestock houses and manure storage facilities contribute greatly to the total loss of N from livestock farms . Volatilisation of ammonia (NH3) is the major process responsible for the loss of N in husbandry systems with slurry (where average dry matter content varies between 3 and 13%) . Concerning this volatilisation of NH3, the process parameters of pH and air temperature are crucial . During a period of approximately 10 years, systematic measurements of NH3 losses originating from a large variety of different livestock houses were made . One of the problems with NH3 emissions is the large variation in the measured data due to the season, the production of the animals, the manure treatment, type of livestock house, and the manure storage . Generally speaking, prevention and control of NH3 emission can be done by control of N content in the manure, moisture content, pH, and temperature . In houses for growing pigs, a combination of simple housing measures can be taken to greatly reduce NH3 emissions . In houses for laying hens, the control of the manure drying process determines the emission of NH3 . Monteny has built an NH3 production model with separate modules for the emission of the manure storage under the dairy house and the floor in the house . Manure spreading is also a major source of NH3 emission and is dependent on slurry composition, environmental conditions, and farm management . The effects of these factors have been employed in a model . Losses via NO, N2O, and N2 are important in husbandry systems with solid manure and straw . The number of experimental data is, however, very limited . As N2O is an intermediate product of complex biochemical processes of nitrification and denitrification, optimal conditions are the key issues in N2O reduction strategies . We may expect that in the near future the emission of greenhouse gases will get the same attention from policy makers as NH3 . Sustainable livestock production has to combine low emissions of gaseous N compounds with acceptable odour emissions, low emissions of greenhouse gases, and acceptable standards of animal welfare . For the entrepreneur, the strategy must be built on the regulations, the special conditions of his farm, and what is reasonably achievable.

ScientificWorldJournal, 2001 Nov 21, 1 Suppl 2, 548 - 55
Nitrate leakage from deciduous forest soils into streams on Kureha Hill, Japan; Honoki H et al.; Nitrate leakage from deciduous forest soils into streams was investigated for two adjacent hills . Many of the streams on Kureha Hill, located in Toyama City, Japan, have extremely high nitrate concentrations . The nitrate concentration of Hyakumakidani, one of the streams on Kureha Hill, averaged 158 microeq l(-1) and reached 470 microeq l(-1) during an episodic event . In contrast, the streams on Imizu Hill, adjacent to Kureha Hill, had low concentrations, below 15 microeq l(-1) . Even during an episode, the nitrate concentrations increased to no more than 75 microeq l(-1).Both areas have similar blown forest soils, C/N ratios in O horizons, and vegetation consisting primarily of deciduous trees . However, soil incubation experiments, which lasted for 4 weeks, revealed that the nitrification rates in the surface soils of Kureha Hill were much higher than in the soils of Imizu Hill.

ScientificWorldJournal, 2001 Nov 10, 1 Suppl 2, 493 - 9
Regeneration of mature Norway spruce stands: early effects of selective cutting and clear cutting on seepage water quality and soil fertility; Weis W et al.; The cutting of trees influences element turnover in the forest ecosystem . The reduction of plant uptake, as well as an increased mineralization and nitrification due to higher soil temperature and soil moisture, can lead to considerable losses of nutrients from the main rooting zone . This may result in a reduced soil fertility and a decrease in drinking water quality due to high nitrate concentrations in the seepage water . In Bavaria (Germany) selective cutting is preferred to clear cutting when initiating the regeneration of Norway spruce stands with European beech . This paper summarizes the early effects of both forest management practices on soil fertility and seepage water quality for three different sites . Shown are the concentrations of nitrogen and base cations in the seepage water as well as the water and ion fluxes during the first year after tree cut . Nutrient inputs decreased on thinned plots and even more at clear-cuts . Nitrate concentrations in the seepage water are hardly affected by moderate thinning; however, on clear-cuts, the nitrate concentration increases significantly, and base cations are lost from the upper mineral soil . This effect is less obvious at sites where a dense ground vegetation, which is able to take up excess nitrogen, exists.

ScientificWorldJournal, 2001 Nov 22, 1 Suppl 2, 480 - 92
Is there synchronicity in nitrogen input and output fluxes at the Noland Divide Watershed, a small N-saturated forested catchment in the Great Smoky Mountains National Park?
Van Miegroet H, Creed IF, Nicholas NS, Tarboton DG, Webster KL, Shubzda J, Robinson B, Smoot J, Johnson DW, Lindberg SE, Lovett G, Nodvin S, Moore S.
High-elevation red spruce {Picea rubens Sarg.}-Fraser fir {Abies fraseri (Pursh.) Poir} forests in the Southern Appalachians currently receive large nitrogen (N) inputs via atmospheric deposition (30 kg N ha(-1) year(-1)) but have limited N retention capacity due to a combination of stand age, heavy fir mortality caused by exotic insect infestations, and numerous gaps caused by windfalls and ice storms . This study examined the magnitude and timing of the N fluxes into, through, and out of a small, first-order catchment in the Great Smoky Mountains National Park . It also examined the role of climatic conditions in causing interannual variations in the N output signal . About half of the atmospheric N input was exported annually in the streamwater, primarily as nitrate (NO3-N) . While most incoming ammonium (NH4-N) was retained in the canopy and the forest floor, the NO3-N fluxes were very dynamic in space as well as in time . There was a clear decoupling between NO3-N input and output fluxes . Atmospheric N input was greatest in the growing season while largest NO3-N losses typically occurred in the dormant season . Also, as water passed through the various catchment compartments, the NO3-N flux declined below the canopy, increased in the upper soil due to internal N mineralization and nitrification, and declined again deeper in the mineral soil due to plant uptake and microbial processing . Temperature control on N production and hydrologic control on NO3-N leaching during the growing season likely caused the observed inter-annual variation in fall peak NO3-N concentrations and N discharge rates in the stream.

ScientificWorldJournal, 2001 Nov 08, 1 Suppl 2, 433 - 9
A case study of nitrogen saturation in western U.S . forests; Fenn ME et al.; Virtually complete nitrification of the available ammonium in soil and nitrification activity in the forest floor are important factors predisposing forests in the San Bernardino Mountains of southern California to nitrogen (N) saturation . As a result, inorganic N in the soil solution is dominated by nitrate . High nitrification rates also generate elevated nitric oxide (NO) emissions from soil . High-base cation saturation of these soils means that soil calcium depletion or effects associated with soil acidification are not an immediate risk for forest health as has been postulated for mesic forests in the eastern U.S . Physiological disturbance (e.g., altered carbon {C} cycling, reduced fine root biomass, premature needle abscission) of ozone-sensitive ponderosa pine trees exposed to high N deposition and high ozone levels appear to be the greater threat to forest sustainability . However, N deposition appears to offset the aboveground growth depression effects of ozone exposure . High nitrification activity reported for many western ecosystems suggests that with chronic N inputs these systems are prone to N saturation and hydrologic and gaseous losses of N . High runoff during the winter wet season in California forests under a Mediterranean climate may further predispose these watersheds to high nitrate leachate losses . After 4 years of N fertilization at a severely N saturated site in the San Bernardino Mountains, bole growth unexpectedly increased . Reduced C allocation below- ground at this site, presumably in response to ozone or N or both pollutants, may enhance the bole growth response to added N.

ScientificWorldJournal, 2001 Dec 12, 1 Suppl 2, 320 - 7
Nitrogen management in a maize-groundnut crop rotation of humid tropics: effect on N2O emission; Khalil MI et al.; Development of appropriate land management techniques to attain sustainability and increase the N use efficiency of crops in the tropics has been gaining momentum . The nitrous oxides (N2Os) affect global climate change and its contribution from N and C management systems is of great significance . Thus, N transformations and N2O emission during maize-groundnut crop rotation managed with various N sources were studied . Accumulation of nitrate (NO3- ) and its disappearance happened immediately after addition of various N sources, showing liming effect . The mineral N retained for 2-4 weeks depending on the type and amount of N application . The chicken manure showed rapid nitrification in the first week after application during the fallow period, leading to a maximum N2O flux of 9889 g N2O-N m(-2) day(-1) . The same plots showed a residual effect by emitting the highest N2O (4053 microg N2O-N m(-2) day(-1)) during maize cultivation supplied with a half-rate of N fertilizer . Application of N fertilizer only or in combination with crop residues exhibited either lowered fluxes or caused a sink during the groundnut and fallow periods due to small availability of substrates and/or low water-filled pore space (<40%) . The annual N2O emission ranged from 1.41 to 3.94 kg N2O-N ha(-1); the highest was estimated from the chicken manure plus crop residues and half-rate of inorganic N-amended plots . Results indicates a greater influence of chicken manure on the N transformations and thereby N2O emission.

Huan Jing Ke Xue, 2003 Mar, 24(2), 1 - 6
{Autotrophic biofilters for oxidation of nitric oxide}; Chen J et al.; Carbon foam, a kind of new engineering material as packing material was adopted in three fi 50.8 mm biofilters with different pore dimension and a domesticated autotrophic nitrite nitrobacteria to investigate the purification of nitrie oxide(NO) in air stream . The biofilm was developed on the surface of carbon foams using nitrite as its only nitric source . The moisture in the filter was maintained by ultrasonic aerosol equipment, which can also minimize the thickness of the liquid film . The liquid phase nitrification test was conducted to determine the variability and the potential of performance among the three carbon foam-based biofilters . The investigation showed that during the NO influent concentration of 200 to 800 g/(L.min), the 24PPC (Pores Per Centimeter) carbon foam-based biofilters had the greatest potential, achieving removal efficiencies of 94% to 98% . The 8PPC and 18PPC carbon foam-based biofilters achieved removals efficiencies of 15% to 21% and of 30% to 40%, respectively . Further research showed the potential for this system to remove NO from an air stream on the base of a steady removal efficiency of 41% to 52% was attained for the 24PPC carbon foam-based biofilter at specified NO influent concentrations of 66.97 to 267.86 mg/m3 and an empty-bed residence time of 3.5 minutes.

Appl Biochem Biotechnol, 2003 Apr-Jun, 109(1-3), 285 - 301
Aerobic and anaerobic microbial degradation of poly-beta-hydroxybutyrate produced by Azotobacter chroococcum; Bonartseva GA et al.; Food industry wastewater served as a carbon source for the synthesis of poly-beta-hydroxybutyrate (PHB) by Azotobacter chroococcum . The content of polymer in bacterial cells grown on the raw materials reached 75% . PHB films were degraded under aerobic, microaerobic, and anaerobic conditions in the presence and absence of nitrate by microbial populations of soil, sludges from anaerobic and nitrifying/denitrifying reactors, and sediment from a sludge deposit site . Changes in molecular mass, crystallinity, and mechanical properties of PHB were studied . Anaerobic degradation was accompanied by acetate formation, which was the main intermediate utilized by denitrifying bacteria or methanogenic archaea . On a decrease in temperature from 20 to 5 degrees C in the presence of nitrate, the rate of PHB degradation was 7.3 times lower . Under anaerobic conditions and in the absence of nitrate, no PHB degradation was observed, even at 11 degrees C . The enrichment cultures of denitrifying bacteria obtained from soil and anaerobic sludge degraded PHB films for a short time (3-7 d) . The dominant species in the enrichment culture from soil were Pseudomonas fluorescens and Pseudomonas stutzeri . The rate of PHB degradation by the enrichment cultures depended on the polymer molecular weight, which reduced with time during biodegradation.

Biotechnol Prog, 2003 May-Jun, 19(3), 789 - 93
Benzene transformation in nitrifying batch cultures; Zepeda A et al.; The effect of benzene on the nitrifying activity of a sludge produced in steady-state nitrification was evaluated in batch cultures . Benzene at 10 mg/L inhibited nitrate formation by 53%, whereas at 5 mg/L there was no inhibition . For initial benzene concentrations of 0, 7, and 10 mg/L, the specific rates of NO(3)(-)-N production were 0.545 +/- 0.101, 0.306 +/- 0.024, and 0.141 +/- 0.010 g NO(3)(-)-N/g microbial protein-N.h, respectively . The specific rates of benzene consumption at 7, 12, and 20 mg/L were 0.034 +/- 0.003, 0.050 +/- 0.006, and 0.027 +/- 0.002 g/g microbial protein-N.h, respectively . Up to a concentration of 10 mg/L, benzene was first oxidized to phenol, which was later totally oxidized to acetate . Benzene at higher concentrations (20 and 30 mg/L) was converted to intermediates other than acetate, phenol, or catechol . These results suggest that this type of nitrifying consortium coupled with a denitrification system may have promising applications for complete removal of nitrogen and benzene from wastewaters.

Appl Environ Microbiol, 2003 Jun, 69(6), 3213 - 22
Community analysis of ammonia and nitrite oxidizers during start-up of nitritation reactors; Egli K et al.; Partial nitrification of ammonium to nitrite under oxic conditions (nitritation) is a critical process for the effective use of alternative nitrogen removal technologies from wastewater . Here we investigated the conditions which promote establishment of a suitable microbial community for performing nitritation when starting from regular sewage sludge . Reactors were operated in duplicate under different conditions (pH, temperature, and dilution rate) and were fed with 50 mM ammonium either as synthetic medium or as sludge digester supernatant . In all cases, stable nitritation could be achieved within 10 to 20 days after inoculation . Quantitative in situ hybridization analysis with group-specific fluorescent rRNA-targeted oligonucleotides (FISH) in the different reactors showed that nitrite-oxidizing bacteria of the genus Nitrospira were only active directly after inoculation with sewage sludge (up to 4 days and detectable up to 10 days) . As demonstrated by quantitative FISH and restriction fragment length polymorphism (RFLP) analyses of the amoA gene (encoding the active-site subunit of the ammonium monooxygenase), the community of ammonia-oxidizing bacteria changed within the first 15 to 20 days from a more diverse set of populations consisting of members of the Nitrosomonas communis and Nitrosomonas oligotropha sublineages and the Nitrosomonas europaea-Nitrosomonas eutropha subgroup in the inoculated sludge to a smaller subset in the reactors . Reactors operated at 30 degrees C and pH 7.5 contained reproducibly homogeneous communities dominated by one amoA RFLP type from the N . europaea-N . eutropha group . Duplicate reactors at pH 7.0 developed into diverse communities and showed transient population changes even within the ammonia oxidizer community . Reactors at pH 7.5 and 25 degrees C formed communities that were indistinguishable by the applied FISH probes but differing in amoA RFLP types . Communities in reactors fed with sludge digester supernatant exhibited a higher diversity and were constantly reinoculated with ammonium oxidizers from the supernatant . Therefore, such systems could be maintained at a higher dilution rate (0.75 day(-1) compared to 0.2 day(-1) for the synthetic wastewater reactors) . Despite similar reactor performance with respect to chemical parameters, the underlying community structures were different, which may have an influence on stability during perturbations.

Appl Environ Microbiol, 2003 Jun, 69(6), 3129 - 36
Ammonia-oxidizing bacteria along meadow-to-forest transects in the Oregon Cascade Mountains; Mintie AT et al.; Although nitrification has been well studied in coniferous forests of Western North America, communities of NH(3)-oxidizing bacteria in these forests have not been characterized . Studies were conducted along meadow-to-forest transects at two sites (Lookout and Carpenter) in the H . J . Andrews Experimental Forest, located in the Cascade Mountains of Oregon . Soil samples taken at 10- or 20-m intervals along the transects showed that several soil properties, including net nitrogen mineralization and nitrification potential rates changed significantly between vegetation zones . Nonetheless, terminal restriction fragment length polymorphism (T-RFLP) analysis of the PCR-amplified NH(3) monooxygenase subunit A gene (amoA) showed the same DNA fragments (TaqI {283 bp}, CfoI {66 bp}, and AluI {392 bp}) to dominate >/=45 of 47 soil samples recovered from both sites . Two fragments (491-bp AluI {AluI491} and CfoI135) were found more frequently in meadow and transition zone soil samples than in forest samples at both sites . At the Lookout site the combination AluI491-CfoI135 was found primarily in meadow samples expressing the highest N mineralization rates . Four unique amoA sequences were identified among 15 isolates recovered into pure culture from various transect locations . Six isolates possessed the most common T-RFLP amoA fingerprint of the soil samples (TaqI283-AluI392-CfoI66), and their amoA sequences shared 99.8% similarity with a cultured species, Nitrosospira sp . strain Ka4 (cluster 4) . The other three amoA sequences were most similar to sequences of Nitrosospira sp . strain Nsp1 and Nitrosospira briensis (cluster 3) . 16S ribosomal DNA sequence analysis confirmed the affiliation of these isolates with Nitrosospira clusters 3 and 4 . Two amoA clone sequences matched T-RFLP fingerprints found in soil, but they were not found among the isolates.

Biotechnol Bioeng, 2003 Aug 5, 83(3), 260 - 73
Experimental investigation of the external nitrification biological nutrient removal activated sludge (ENBNRAS) system; Hu ZR et al.; A systematic lab-scale experimental investigation is reported for the external nitrification (EN) biological nutrient removal (BNR) activated sludge (ENBNRAS) system, which is a combined fixed and suspended medium system . The ENBNRAS system was proposed to intensify the treatment capacity of BNR-activated sludge (BNRAS) systems by addressing two difficulties often encountered in practice: (a) the long sludge age for nitrification requirement; and (b) sludge bulking . In the ENBNRAS system, nitrification is transferred from the aerobic reactor in the suspended medium activated sludge system to a fixed medium nitrification system . Thus, the sludge age of the suspended medium activated sludge system can be reduced from 20 to 25 days to 8 to 10 days, resulting in a decrease in reactor volume per ML wastewater treated of about 30% . Furthermore, the aerobic mass fraction can also be reduced from 50% to 60% to <30% and concommitantly the anoxic mass fraction can be increased from 25% to 35% to >55% (if the anaerobic mass fraction is 15%), and thus complete denitrification in the anoxic reactors becomes possible . Research indicates that both the short sludge age and complete denitrification could ameliorate anoxic aerobic (AA) or low food/microorganism (F/M) ratio filamentous bulking, and hence reduce the surface area of secondary settling tanks or increase the treatment capacity of existing systems . The lab-scale experimental investigations indicate that the ENBNRAS system can obtain: (i) very good chemical oxygen demand (COD) removal, even with an aerobic mass fraction as low as 20%; (ii) high nitrogen removal, even for a wastewater with a high total kjeldahl nitrogen (TKN)/COD ratio, up to 0.14; (iii) adequate settling sludge (diluted sludge volume index {DSVI} <100 mL/g); and (iv) a significant reduction in oxygen demand .

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003 Jun, 38(6), 1007 - 15
Nitrogen removal via nitrite at normal temperature in A/O process; Peng YZ et al.; In order to study the nitrogen removal via nitrite at normal temperature in anoxic/oxic (A/O) process for treating domestic wastewater, the influence of pH, free ammonia (FA), dissolved oxygen (DO), and hydraulic retention time (HRT) were studied . Results indicated that it was possible to remove nitrogen via nitrite in A/O process, if the temperature was between 18 and 25 degrees C and pH was below 7.5 . Even if FA was as low as 0.06 mg NH3-N/L, it would inhibit the nitrobacteria . However, FA could not be the sole factor . Whether denitrification went thoroughly or not could affect the nitrification pathway . If denitrification went well, nitrite accumulation could recover in a short while . Nitritification lagged nitratification, so that short HRT would help nitrite accumulation . On the other hand, extended aeration would reduce nitrite accumulation.

Water Environ Res, 2003 Mar-Apr, 75(2), 151 - 62
High nitrite buildup during nitrification in a rotating disk reactor; Antileo C et al.; Incomplete nitrification with high nitrite accumulation has three practical advantages: lower oxygen consumption, less need for organics for denitrification, and lower sludge production during denitrification . Nitrification leading to high nitrite formation was experimentally studied in a continuous single rotating disk reactor (RDR) and compared to a modeled continuous completely stirred tank reactor (CSTR) . The results of this model show that to accumulate nitrite greater than 50% at oxygen levels higher than 3.5 mg O2/L, pH levels higher than 8.5 and 9.0 are required for a CSTR with and without cell washout, respectively . For a CSTR without cell washout at pH 7 and 1 mg O2/L, it was predicted that a nitrite accumulation less than 5% could be reached . Conversely, for a partially submerged continuous RDR without any additional aeration supply (already at pH 7 and 1.3 mg O2/L), high nitrite accumulation (more than 75%) was achieved and the influence of pH from 7 to 9 was not significant . This difference is believed to be caused by mass transfer . In addition, nitrification was observed to occur under oxygen transport limitation for a totally submerged continuous RDR.

Water Environ Res, 2003 Mar-Apr, 75(2), 138 - 50
Simultaneous biological nutrient removal: evaluation of autotrophic denitrification, heterotrophic nitrification, and biological phosphorus removal in full-scale systems; Littleton HX et al.; Simultaneous biological nutrient removal (SBNR) is the biological removal of nitrogen and phosphorus in excess of that required for biomass synthesis in a biological wastewater treatment system without defined anaerobic or anoxic zones . Evidence is growing that significant SBNR can occur in many systems, including the aerobic zone of systems already configured for biological nutrient removal . Although SBNR systems offer several potential advantages, they cannot be fully realized until the mechanisms responsible for SBNR are better understood . Consequently, a research program was initiated with the basic hypothesis that three mechanisms might be responsible for SBNR: the reactor macroenvironment, the floc microenvironment, and novel microorganisms . Previously, the nutrient removal capabilities of seven full-scale, staged, closed-loop bioreactors known as Orbal oxidation ditches were evaluated . Chemical analysis and microbiological observations suggested that SBNR occurred in these systems . Three of these plants were further examined in this research to evaluate the importance of novel microorganisms, especially for nitrogen removal . A screening tool was developed to determine the relative significance of the activities of microorganisms capable of autotrophic denitrification and heterotrophic nitrification-aerobic denitrification in biological nutrient removal systems . The results indicated that novel microorganisms were not substantial contributors to SBNR in the plants studied . Phosphorus metabolism (anaerobic release, aerobic uptake) was also tested in one of the plants . Activity within the mixed liquor that was consistent with current theories for phosphorus-accumulating organisms (PAOs) was observed . Along with other observations, this suggests the presence of PAOs in the facilities studied.

Water Res, 2003 Jul, 37(12), 3009 - 15
The effect of residual ammonia concentration under aerobic conditions on the growth of Microthrix parvicella in biological nutrient removal plants; Tsai MW et al.; It is demonstrated with two parallel single reactor intermittently aerated nitrification denitrification systems fed municipal wastewater as influent, that Microthrix parvicella bulking can be stimulated and cured by manipulating the ammonia concentration in the aerobic period (by inhibiting the nitrifiers) to high and low values respectively . The proliferation or not of M . parvicella is hypothesized to be due to their requirement for ammonia as a nitrogen source for growth . In terms of this hypothesis, if nitrification is rapid and complete, ammonia is not freely available and will limit M . parvicella growth . If nitrification is not complete for whatever reason, ammonia is available for the growth of the slow growing M . parvicella, enabling their proliferation to cause a bulking sludge . This hypothesis does not overturn or replace the anoxic-aerobic (AA, or low Food/Microorganism, F/M, ratio) filament bulking hypothesis of Casey et al . (Water SA 25(4) (1999) 425) but appears to be additional to it . Future research will focus on determining how elements of both hypotheses superimpose on the conditions in BNR systems, to produce an AA filament bulking sludge or not.

Water Res, 2003 Jul, 37(12), 2893 - 904
A simplified method to assess structurally identifiable parameters in Monod-based activated sludge models; Petersen B et al.; The first step in the estimation of parameters of models applied for data interpretation should always be an investigation of the identifiability of the model parameters . In this study the structural identifiability of the model parameters of Monod-based activated sludge models (ASM) was studied . In an illustrative example it was assumed that respirometric (dissolved oxygen or oxygen uptake rates) and titrimetric (cumulative proton production) measurements were available for the characterisation of nitrification . Two model structures, including the presence and absence of significant growth for description of long- and short-term experiments, respectively, were considered . The structural identifiability was studied via the series expansion methods . It was proven that the autotrophic yield becomes uniquely identifiable when combined respirometric and titrimetric data are assumed for the characterisation of nitrification . The most remarkable result of the study was, however, that the identifiability results could be generalised by applying a set of ASM1 matrix based generalisation rules . It appeared that the identifiable parameter combinations could be predicted directly based on the knowledge of the process model under study (in ASM1-like matrix representation), the measured variables and the biodegradable substrate considered . This generalisation reduces the time-consuming task of deriving the structurally identifiable model parameters significantly and helps the user to obtain these directly without the necessity to go too deeply into the mathematical background of structural identifiability.

Appl Microbiol Biotechnol, 2003 Jun, 61(5-6), 562 - 8 Epub 2003 Mar 08.
Predicting the effects of chlorine on the micro-organisms of filamentous bulking activated sludges; Seka MA et al.; Rapid and definite assessment of the effect that a specific biocide has on a specific case of filamentous bulking sludge is a much-needed tool in activated sludge wastewater treatment . The Live/Dead stain (LIVE/DEAD BacLight) distinguishing "living" and "non-living" cells, a nitrifying activity (NA) test and the oxygen uptake rate (OUR) measurement were examined for their appropriateness to predict the effects of chlorine on filamentous bulking sludges . The study showed the live/dead stain to be relevant for revealing the specific effect of chlorine on the filamentous bacteria of a bulking sludge . However, using live/dead stain alone for the determination of the appropriate chlorine dose against bulking may lead to an underestimation of the damage caused by chlorine to the useful microorganisms in the flocs . Indeed, using the live/dead stain, it was not easy to distinguish dead cells caused by chlorination from those originally present in the flocs The NA test was the most sensitive in detecting damage caused by chlorine to the floc-forming microorganisms . Therefore, for a safer determination of the chlorine dose effective against bulking and protective of the microbial activity of the sludge, the results of this study suggest coupling of the live/dead stain with the NA test and/or the OUR test.

Appl Microbiol Biotechnol, 2003 Jun, 61(5-6), 556 - 61 Epub 2003 Feb 20.
Elemental compositions and characteristics of aerobic granules cultivated at different substrate N/C ratios; Liu Y et al.; The effects of the substrate N/C ratios on the formation, elemental compositions and characteristics of aerobic granules were investigated in four sequencing batch reactors . Results showed that aerobic granules could form at substrate N/C ratios ranging from 5/100 to 30/100 and the substrate N/C ratio had a direct and profound effect on the elemental compositions and characteristics of the aerobic granules . Nitrifying populations in aerobic granules were enriched significantly with the increase in the substrate N/C ratio, while the respective ratio of cell oxygen, nitrogen and calcium to cell carbon were also determined by the substrate N/C ratio . It was found that cell hydrophobicity of aerobic granules was inversely related to the ratio of cell oxygen normalized to cell carbon . Since the cell calcium content in aerobic granules developed at different substrate N/C ratios was even lower than that in the seed sludge, it is reasonable to conclude that the cell calcium would not contribute to aerobic granulation . This study probably for the first time demonstrates that the elemental composition, microbial distribution and characteristics of aerobic granules are related to the substrate N/C ratio applied.

Water Res, 2003 Jun, 37(11), 2723 - 31
Application of calorimetric measurements for biokinetic characterisation of nitrifying population in activated sludge; Daverio E et al.; A preliminary investigation is described on the application of calorimetry as a sensitive technique to evaluate nitrifying activity in activated sludge . Calorimetric profiles (thermograms) related to heat dissipation due to biological nitrification reactions (ammonia or nitrite consumption) have been interpreted . Correlations between calorimetric data and the main process variables, i.e . ammonia and nitrite concentration and oxygen uptake, have been verified, and confirm the potential of calorimetry to investigate, monitor and control even weakly exothermic biological processes like autotrophic nitrification . Heat yields (Y(Q/i)) for ammonia, nitrite, and oxygen, defined as the heat released per unit amount of converted reactant, have been separately evaluated . Moreover, calorimetric experiments on activated sludge from a full-scale nitrogen removal wastewater treatment plant have been carried out and kinetic parameters for both ammonia and nitrite oxidising bacteria have been estimated.

Water Res, 2003 Jun, 37(11), 2678 - 90
Online titrimetric and off-gas analysis for examining nitrification processes in wastewater treatment; Gapes D et al.; The two steps of nitrification, namely the oxidation of ammonia to nitrite and nitrite to nitrate, often need to be considered separately in process studies . For a detailed examination, it is desirable to monitor the two-step sequence using online measurements . In this paper, the use of online titrimetric and off-gas analysis (TOGA) methods for the examination of the process is presented . Using the known reaction stoichiometry, combination of the measured signals (rates of hydrogen ion production, oxygen uptake and carbon dioxide transfer) allows the determination of the three key process rates, namely the ammonia consumption rate, the nitrite accumulation rate and the nitrate production rate.Individual reaction rates determined with the TOGA sensor under a number of operation conditions are presented . The rates calculated directly from the measured signals are compared with those obtained from offline liquid sample analysis . Statistical analysis confirms that the results from the two approaches match well . This result could not have been guaranteed using alternative online methods.As a case study, the influences of pH and dissolved oxygen (DO) on nitrite accumulation are tested using the proposed method . It is shown that nitrite accumulation decreased with increasing DO and pH . Possible reasons for these observations are discussed.

Chemosphere, 2003 Jul, 52(3), 609 - 21
Fluxes of methane, carbon dioxide and nitrous oxide in boreal lakes and potential anthropogenic effects on the aquatic greenhouse gas emissions; Huttunen JT et al.; We have examined how some major catchment disturbances may affect the aquatic greenhouse gas fluxes in the boreal zone, using gas flux data from studies made in 1994-1999 in the pelagic regions of seven lakes and two reservoirs in Finland . The highest pelagic seasonal average methane (CH(4)) emissions were up to 12 mmol x m(-2) x d(-1) from eutrophied lakes with agricultural catchments . Nutrient loading increases autochthonous primary production in lakes, promoting oxygen consumption and anaerobic decomposition in the sediments and this can lead to increased CH(4) release from lakes to the atmosphere . The carbon dioxide (CO(2)) fluxes were higher from reservoirs and lakes whose catchment areas were rich in peatlands or managed forests, and from eutrophied lakes in comparison to oligotrophic and mesotrophic sites . However, all these sites were net sources of CO(2) to the atmosphere . The pelagic CH(4) emissions were generally lower than those from the littoral zone . The fluxes of nitrous oxide (N(2)O) were negligible in the pelagic regions, apparently due to low nitrate inputs and/or low nitrification activity . However, the littoral zone, acting as a buffer for leached nitrogen, did release N(2)O . Anthropogenic disturbances of boreal lakes, such as increasing eutrophication, can change the aquatic greenhouse gas balance, but also the gas exchange in the littoral zone should be included in any assessment of the overall effect . It seems that autochthonous and allochthonous carbon sources, which contribute to the CH(4) and CO(2) production in lakes, also have importance in the greenhouse gas emissions from reservoirs.

Bioresour Technol, 2003 Mar, 87(1), 103 - 11
Nitrification, denitrification and biological phosphorus removal in piggery wastewater using a sequencing batch reactor; Obaja D et al.; Nutrients in piggery wastewater with high organic matter, nitrogen (N) and phosphorus (P) content were biologically removed in a sequencing batch reactor (SBR) with anaerobic, aerobic and anoxic stages . The SBR was operated with 3 cycles/day, temperature 30 degrees C, sludge retention time (SRT) 1 day and hydraulic retention time (HRT) 11 days . With a wastewater containing 1500 mg/l ammonium and 144 mg/l phosphate, a removal efficiency of 99.7% for nitrogen and 97.3% for phosphate was obtained . Experiments set up to evaluate the effect of temperature on the process showed that it should be run at temperatures higher than 16 degrees C to obtain good removals (> 95%) . Batch tests (ammonia utilization rate, nitrogen utilization rate and oxygen utilization rate) proved to be good tools to evaluate heterotrophic and autotrophic biomass activity . The SBR proved to be a very flexible tool, and was particularly suitable for the treatment of piggery wastewater, characterized by high nutrient content and by frequent changes in composition and therefore affecting process conditions.

Curr Microbiol, 2003 Apr, 46(4), 270 - 4
The role of cell hydrophobicity in the formation of aerobic granules; Liu Y et al.; Cell hydrophobicity is an important affinity force in cell self-immobilization and attachment processes . The role of cell hydrophobicity in the formation of aerobic granules has not been clear . Therefore, two series of experiments were conducted to investigate the role of cell hydrophobicity in the formation of aerobic heterotrophic and nitrifying granules in sequencing batch reactors, while the effects of shear strength, hydraulic selection pressure, and organic loading rate on the cell hydrophobicity were also studied . Results showed that the formations of heterotrophic and nitrifying granules were associated very closely with the cell hydrophobicity . The hydrophobicity of granular sludge was nearly twofold higher than that of conventional bioflocs . A high shear force or hydraulic selection pressure imposed on microorganisms resulted in a significant increase in the cell hydrophobicity, while the cell hydrophobicity seemed not to be sensitive to the changes in the organic loading rates in the range studied . In conclusion, the cell hydrophobicity could induce and further strengthen cell-cell interaction, and might be a main triggering force to initiate the granulation of heterotrophic and nitrifying bacteria.

Appl Environ Microbiol, 2003 May, 69(5), 2848 - 56
Optimization of single-base-pair mismatch discrimination in oligonucleotide microarrays; Urakawa H et al.; The discrimination between perfect-match and single-base-pair-mismatched nucleic acid duplexes was investigated by using oligonucleotide DNA microarrays and nonequilibrium dissociation rates (melting profiles) . DNA and RNA versions of two synthetic targets corresponding to the 16S rRNA sequences of Staphylococcus epidermidis (38 nucleotides) and Nitrosomonas eutropha (39 nucleotides) were hybridized to perfect-match probes (18-mer and 19-mer) and to a set of probes having all possible single-base-pair mismatches . The melting profiles of all probe-target duplexes were determined in parallel by using an imposed temperature step gradient . We derived an optimum wash temperature for each probe and target by using a simple formula to calculate a discrimination index for each temperature of the step gradient . This optimum corresponded to the output of an independent analysis using a customized neural network program . These results together provide an experimental and analytical framework for optimizing mismatch discrimination among all probes on a DNA microarray.

Environ Sci Technol, 2003 Apr 15, 37(8), 1690 - 7
Performance of a constructed wetland with a sulfur/limestone denitrification section for wastewater nitrogen removal; Bezbaruah AN et al.; The effectiveness of a nonvegetated lab-scale subsurface flow constructed wetland for wastewater treatment had been evaluated with the feed ammonium concentration of approximately 20-40 mg of NH4(+)-N L(-1) and a hydraulic retention time of approximately 10 d . The present system had a nitrification zone plus a sulfur/limestone (S/L) autotrophic denitrification zone followed by an anaerobic polishing zone and was operated with and without aeration . The wetland had only 80% organics removal and no net nitrogen removal when there was no artificial aeration . However, almost 100% organics removal and approximately 81-90% total inorganic nitrogen (TIN = NH4(+)-N + NO2(-0-N + NO3(-)-N) removal were achieved when the oxic zone of the system was aerated with compressed air . S/L autotrophic denitrification contributed 21-49% of total NO3(-)-N removal across the whole wetland and 50-95% across the S/L column . TIN and NH4(+)-N in the effluent were always < 5.5 and < 0.7 mg L(-1), respectively, when the feed had NH4(+)-N < or = 35 mg L(-1) . Sulfate removal of approximately 53-69% was achieved in the anaerobic polishing zone . The position of the S/L column was changed (1.78, 2.24, and 2.69 m from the inlet), and no remarkable difference in nitrogen removal was observed . However, without the S/L column, TIN removal decreased to approximately 74%, and the effluent NO3(-)-N increased about two times (9.13 mg of N L(-1)) . The present study has demonstrated the possible use of S/L autotrophic denitrification for nitrate removal in a constructed wetland.

Water Res, 2003 May, 37(10), 2331 - 8
Impulse responses of a monoethylamine-fed fluidized bed reactor; Shieh WK et al.; The responses of a steady-state, continuous-flow, completely-mixed fluidized bed reactor (FBR) to a range of monoethylamine (MEA) impulses are analyzed in terms of its combined carbon oxidation and nitrification efficiencies . Immobilized cells are cultivated at a mean cell residence time (MCRT) that exceeds 75 days . Responses due to bacterial activities and physical flows are separately estimated using a methodology based on mass balance calculations . MEA inhibition becomes evident when respective critical impulse loadings are exceeded, i.e., 0.12 mg TOC/mg VS for carbon oxidation and 0.021 mg TOC/mg VS for nitrification (TOC: total organic carbon, VS: volatile solids) . Nitrifying cells are shown to be more susceptible to MEA impulses than their heterotrophic counterparts . However, the presence of nitrification activities under the conditions tested demonstrates the advantages of cell immobilization that offer greater flexibility when challenged with suddenly increased MEA loads over a short period of time . Mass balance calculations on nitrogen species confirms that 0.583 mg NH(4)(+)-N is produced per mg MEA-C removed when the assimilatory nitrogen requirements for cell synthesis are negligible.

Isotopes Environ Health Stud, 2002 Dec, 38(4), 191 - 206
Isotopic assessment of sources and processes affecting sulfate and nitrate in surface water and groundwater of Luxembourg; Rock L et al.; Surface water and deep and shallow groundwater samples were taken from selected parts of the Grand-Duchy of Luxembourg to determine the isotopic composition of nitrate and sulfate, in order to identify sources and/or processes affecting these solutes . Deep groundwater had sulfate concentrations between 20 and 40 mg/L, delta34S(sulfate) values between -3.0 and -20.0 per thousand, and delta18O(sulfate) values between +1.5 and +5.0 per thousand; nitrate was characterized by concentrations varying between < 0.5 and 10 mg/L, delta15N(nitrate) values of approximately -0.5 per thousand, and delta18O(nitrate) values approximately +3.0 per thousand . In the shallow groundwater, sulfate concentrations ranged from 25 to 30 mg/L, delta34S(sulfate) values from -20.0 to +4.5 per thousand, and delta18O(sulfate) values from approximately +0.5 to +4.5 per thousand; nitrate concentrations varied between approximately 10 and 75 mg/L, delta15N(nitrate) values between +2.5 and +10.0 per thousand, and delta18O(nitrate) values between +1.0 and +3.0 per thousand . In surface water, sulfate concentrations ranged from 10 to 210 mg/L, delta34S(sulfate) values varied between -9.3 and +10.9 per thousand, and delta18O(sulfate) values between +3.0 and +10.7 per thousand were observed . Nitrate concentrations ranged from 10 to 40 mg/L, delta15N(nitrate) values from +6.5 to +12.0 per thousand, and delta18O(nitrate) values from -0.4 to +4.0 per thousand . Based on these data, three sulfate sources were identified controlling the riverine sulfate load . These are soil sulfate, dissolution of evaporites, and oxidation of reduced S minerals in the bedrock . Both groundwater types were predominantly influenced by sulfate from the two latter lithogenic S sources . The deep groundwater and a couple shallow groundwater samples had nitrate derived mainly from soil nitrification . All other sampling sites were influenced by nitrate originating from sewage and/or manure . A decrease in nitrate concentration observed along one of the rivers was attributed to denitrification . It appears that sulfate within Luxembourg's aquatic ecosystem is mainly of lithogenic origin, whereas nitrate is often derived from anthropogenic activities.

Ying Yong Sheng Tai Xue Bao, 2003 Jan, 14(1), 101 - 4
{Using chlorella and effective microorganisms to optimize aquatic ecological structure and to regulate water quality}; Han S et al.; To optimize aquatic ecological structure and to regulate water quality, Chlorella vulgaris and effective microorganism were added to Exopalaemon carinicauda pond and fishponds . The results showed that after adding Chlorella vulgaris to the shrimp pond and fishpond, Chlorella vulgaris turned into a dominant species, and its amount was 16.92 and 4.76 times of CK . The zooplankton biomass reached to 4.32 mg.L-1 and 2.84 mg.L-1, increasing by 19.3% and 2.5%, compared with CK, respectively . Rhodospirillaceae, photosynthetic bacteria and yeast saccharomycete in the ponds could obviously change the composition, number, ratio, and biomass of the plankton (phytoplankton and zooplankton), and adjust aquatic chemical environment . The treatment of "Saccharomycete + Nitrifying bacteria" decreased the concentrations of NH4+ obviously, which was only 44% of CK . The BOD and COD in shrimp ponds were only 56.5% and 38.4% of CK . The treatment could increase the dissolved oxygen and primary production in the pond.

Environ Microbiol, 2003 May, 5(5), 355 - 69
Structure and activity of multiple nitrifying bacterial populations co-existing in a biofilm; Gieseke A et al.; A biofilm from a nitrifying pilot-scale sequencing batch reactor was investigated for effects of varying process conditions on its microscale activity and structure . Microsensor measurements of oxygen, substrates and products of nitrification were applied under incubation at different ammonium and oxygen concentrations which reflected various situations during a treatment cycle . A high net N loss was observed under high ammonium (HA) concentrations in contrast to low ones . Additionally, results indicated inhibition of nitrite-oxidizing bacteria (NOB), but not of ammonia-oxidizing bacteria (AOB) by free ammonia under HA conditions . Diversity, spatial distribution, and abundance of nitrifying bacteria as analysed by fluorescence in situ hybridization (FISH) revealed six different nitrifying populations with heterogeneous distributions . Nitrosococcus mobilis formed conspicuous microcolonies locally surrounded by cells of the dominating N . europaea/eutropha-related AOB population . A third less abundant population was affiliated to N . oligotropha . Nitrite-oxidizing bacteria of the genera Nitrobacter and Nitrospira (with at least two distinct populations) showed a large scale heterogeneity in their distribution . Nitrospira spp . were also found in deeper inactive layers where they might persist rather than thrive, and act as seed population when detached . Results of functional and structural analyses are discussed with respect to specific niches of individual populations in this system.

Biodegradation, 2002, 13(6), 373 - 81
Cooxidation of naphthalene and other polycyclic aromatic hydrocarbons by the nitrifying bacterium, Nitrosomonas europaea; Chang SW et al.; The soil nitrifying bacterium Nitrosomonas europaea has shown the ability to transform cometabolically naphthalene as well as other 2- and 3-ringed polycyclic aromatic hydrocarbons (PAHs) to more oxidized products . All of the observed enzymatic reactions were inhibited by acetylene, a selective inhibitor of ammonia monooxygenase (AMO) . A strong inhibitory effect of naphthalene on ammonia oxidation by N . europaea was observed . Naphthalene was readily oxidized by N . europaea and 2-naphthol was detected as a major product (85%) of naphthalene oxidation . The maximum naphthol production rate was 1.65 nmole/mg protein-min in the presence of 240 microM naphthalene and 10 mM NH4+ . Our results demonstrate that the oxidation between ammonia and naphthalene showed a partial competitive inhibition . The relative ratio of naphthalene and ammonia oxidation, depending on naphthalene concentrations, demonstrated that the naphthalene was oxidized 2200-fold slower than ammonia at lower concentration of naphthalene (15 microM) whereas naphthalene was oxidized only 100-fold slower than ammonia oxidation . NH4(+)- and N2H4-dependent O2 uptake measurement demonstrated irreversible inhibitory effects of the naphthalene and subsequent oxidation products on AMO and HAO activity.

Z Naturforsch {C}, 2003 Mar-Apr, 58(3-4), 282 - 7
Susceptibility of ammonia-oxidizing bacteria to nitrification inhibitors; Matsuba D et al.; Activity of nitrification inhibitors to several typical ammonia-oxidizing bacteria isolated recently, i . e . Nitrosococcus, Nitrosolobus, Nitrosomonas, Nitrosospira and Nitrosovibrio species was assayed using 2-amino-4-methyl-trichloromethyl-1,3,5-triazine (MAST), 2-amino-4-tribromomethyl-6-trichloromethyl-1,3,5-triazine (Br-MAST), 2-chloro-6-trichloromethylpyridine (nitrapyrin) and others, and compared to confirm the adequate control of ammonia-oxidizing bacteria by the inhibitors . The order of activity of the inhibitors to 13 species of ammonia-oxidizing bacteria examined was approximately summarized as Br-MAST > or = nitrapyrin > or = MAST > other inhibitors . Two Nitrosomonas strains, N . europaea ATCC25978 and N . sp . B2, were extremely susceptible to Br-MAST, exhibiting a pI50 > or = 6.40 . These values are the position logarithms of the molar half-inhibition concentration . The 16S rRNA gene sequence similarity for the highly susceptible 4 strains of genus Nitrosomonas was 94% to 100% of Nitrosomonas europaea, although those of the less susceptible 3 strains of ammonia-oxidizing bacteria, Nitrosococcus oceanus C-107 ATCC19707, Nitrosolobus sp . PJA1 and Nitrosolobus multiformis ATCC25196, were 77.85, 91.53 and 90.29, respectively . However, no clear correlation has been found yet between pI50-values and percent similarity of 16S rRNA gene sequence among ammonia-oxidizing bacteria.

Eur J Biochem, 2003 May, 270(9), 1935 - 41
Cytochrome P460 of Nitrosomonas europaea . Formation of the heme-lysine cross-link in a heterologous host and mutagenic conversion to a non-cross-linked cytochrome c'; Bergmann DJ et al.; The heme of cytochrome P460 of Nitrosomonas europaea, which is covalently crosslinked to two cysteines of the polypeptide as with all c-type cytochromes, has an additional novel covalent crosslink to lysine 70 of the polypeptide {Arciero, D.M . & Hooper, A.B . (1997) FEBS Lett.410, 457-460} . The protein can catalyze the oxidation of hydroxylamine . The gene for this protein, cyp, was expressed in Pseudomonas aeruginosa strain PAO lacI, resulting in formation of a holo-cytochrome P460 which closely resembled native cytochrome P460 purified from N . europaea in its UV-visible spectroscopic, ligand binding and catalytic properties . Mutant versions of cytochrome P460 of N . europaea in which Lys70 70 was replaced by Arg, Ala, or Tyr, retained ligand-binding ability but lost catalytic ability and differed in optical spectra which, instead, closely resembled those of cytochromes c' . Tryptic fragments containing the c-heme joined only by two thioether linkages were observed by MALDI-TOF for the mutant cytochromes P460 K70R and K70A but not in wild-type cytochrome P460, consistent with the structural modification of the c-heme only in the wild-type cytochrome . The present observations support the hypothesized evolutionary relationship between cytochromes P460 and cytochromes c' in N . europaea and M . capsulatus{Bergmann, D.J., Zahn, J.A., & DiSpirito, A.A . (2000) Arch . Microbiol . 173, 29-34}, confirm the importance of a heme-crosslink to the spectroscopic properties and catalysis and suggest that the crosslink might form auto-catalytically.

Huan Jing Ke Xue, 2003 Jan, 24(1), 84 - 90
{The nitrite accumulation in a biological aerobic filter (BAF) and the influences factors}; Ma J et al.; The nitrite accumulation in a bench-scale biological aerobic filter (BAF) for nitrogen removal was reported in this paper . The influences of operational variables on filter performance and nitrite accumulation were also investigated . The influent loading of NH4+(-)N and TN were 0.26-0.62 kg/(m3.d) and 0.28-0.63 kg/(m3.d) respectively, the hydraulic loading, gas/water ratio and temperature were 1-2 m/h, 3:1 and 20.5 degrees C-26.5 degrees C respectively, the nitrogen removal loading of NH4+(-)N, TN were among 0.15-0.52 kg/(m3.d) and 0.18-0.42 kg/(m3.d) respectively . The nitrite concentrations in the bulk and effluent, the profiles of inorganic nitrogen-compounds, the microbial populations in the reactor and their activity were investigated, suggesting that the nitrite accumulation and shortcut nitrification-denitrification took place in the bioreactor . The mechanism of nitrite accumulation and the influences of operational variables were analyzed . The backwash process was considered as the key influential factor of nitrite accumulation . It was believed that the structure feature and operational pattern were the principal factors that may result in the nitrite accumulation and shortcut nitrification-denitrification occurring in the BAF reactor.

Huan Jing Ke Xue, 2003 Jan, 24(1), 80 - 3
{Study on ability of nitrification in a subsurface constructed wetland system treating sewage}; Liu C et al.; The nitrification ability of different layers in a subsurface constructed wetland treating sewage was measured . The experiment results showed that the ability of nitrification was decreased along the direction of water flow in the subsurface wetland . The constants of ammonia oxidation rate and nitrite oxidation rate in the slag layer on the bottom were 1.99-6.89 mg.(h.kg)-1 and 1.14-5.22 mg.(h.kg)-1 respectively, but in the soil layer on the top were 0.53-0.89 mg.(h.kg)-1 and 0.96-1.39 mg.(h.kg)-1 respectively . So the ability of nitrification in the layer of slag was better than the layer of soil obviously, and it showed that the nitrification was mainly happened in the slag layer.

Environ Technol, 2003 Mar, 24(3), 277 - 87
Impact of backwashing on nitrification in the biological activated carbon filters used in drinking water treatment; Laurent P et al.; Nitrification during biological filtration is currently used in drinking water production to remove ammonia, which is the source of several water quality problems during treatment and distribution . We evaluated here the impact of backwashing on nitrification efficiency in filters used for drinking water treatment . Two different granular activated carbon (one open and one closed carbon superstructure) were tested . Ammonia removal and fixed nitrifying bacterial biomass before and after backwashing were compared in first-stage pilot filters and full-scale second-stage filters . Backwashing has a greater impact on nitrification on first-stage than an second-stage filters . Backwashing improved the ammonia removal in warm (> or = 18 degrees C) water in a first-stage filter containing an open-superstructure granular activated carbon, whereas a closed-superstructure support showed a removal capacity that is less after a regular backwashing than before, or similar to it . In cold water (< or = 4 degrees C), backwashing had a negative impact on nitrification capacity in an open-superstructure medium first-stage filter . In full-scale second-stage filters, backwashing had a slight negative impact on filter performances for both open- and closed-superstructure media at temperatures between 8 degrees C and 12 degrees C . In colder waters (< or = 3 degrees C), nitrification was very poor both before and after backwashing . Sampling of fixed, nitrifying biomass in the pilot filter columns showed that in all cases (low and high expansion backwash; both media tested) and at 20 +/- 3 degrees C the overall biomass levels remained unchanged before and after backwash . In the full-scale second-stage filters, nitrifying bionass was similar before and after backwashing for both types of media tested.

Water Sci Technol, 2003, 47(5), 205 - 9
A novel titrimetric method for monitoring toxicity on nitrifying biofilms; Artiga P et al.; A titrimetric method for monitoring toxicity in suspended biomass was applied in order to measure the activity of nitrifying biofilms and to determine the effect of several toxic compounds on the biofilm . Three typical tannery compounds, quebracho extract, NaCl and Cr+3 were selected to study their toxicity on the biofilms . The results obtained showed an acceptable repeatability of the method for all the toxicants tested with an average standard deviation of less than 10% . Biofilm systems showed higher resistance to the toxicants, when the results obtained using suspended nitrifying biomass, were compared with those found in the literature . The IC50 obtained with quebracho was 8.8 g/L of quebracho extract, while around 65% of maximum activity was attained with 8.7 g/L of NaCl or 120 mg/L Cr+3 . The quebracho extract, NaCl and Cr+3 were 26%, 38% and 18%, respectively, less toxic in the biofilm system than for a suspended biomass culture.

Water Sci Technol, 2003, 47(5), 201 - 4
Respiration rate measurement in a submerged fixed bed reactor; Carrion M et al.; A novel method is presented to measure the overall biofilm respiration rate in a submerged fixed bed reactor . The method, named "double gassing-out" is based on the measurement of the oxygen uptake rate under two different conditions: (i) replacing the air flow rate by nitrogen in the biological reactor, ensuring the conservation of the same hydraulic conditions and (ii) measuring the oxygen displacement rate by nitrogen in an identical reactor design with no microorganisms . The difference between these measurements gives the overall biofilm respiration rate . Results obtained in a nitrifying fixed bed reactor are presented, compared to classical techniques and discussed.

Water Sci Technol, 2003, 47(5), 129 - 32
Comparison of detection specificity of nitrifying bacteria in biofilm using fluorescence in situ hybridization and in situ fluorescent antibody methods; Noda N et al.; The in situ fluorescent antibody and fluorescence in situ hybridization (FISH) methods are very useful in the in situ detection of specific bacteria like nitrifiers in a biofilm . In this study, simultaneous staining using the FISH and in situ fluorescent antibody methods was examined . As a result, no specific fluorescence was observed with either method when FISH was performed followed by the in situ fluorescent antibody method; however, when the in situ fluorescent antibody method was performed first followed by FISH, specific fluorescence was observed in both cases . Moreover, it was suggested that the detection specificities of FISH and the in situ fluorescent antibody method are almost identical.

J Bacteriol, 2003 May, 185(9), 2759 - 73
Complete genome sequence of the ammonia-oxidizing bacterium and obligate chemolithoautotroph Nitrosomonas europaea; Chain P et al.; Nitrosomonas europaea (ATCC 19718) is a gram-negative obligate chemolithoautotroph that can derive all its energy and reductant for growth from the oxidation of ammonia to nitrite . Nitrosomonas europaea participates in the biogeochemical N cycle in the process of nitrification . Its genome consists of a single circular chromosome of 2,812,094 bp . The GC skew analysis indicates that the genome is divided into two unequal replichores . Genes are distributed evenly around the genome, with approximately 47% transcribed from one strand and approximately 53% transcribed from the complementary strand . A total of 2,460 protein-encoding genes emerged from the modeling effort, averaging 1,011 bp in length, with intergenic regions averaging 117 bp . Genes necessary for the catabolism of ammonia, energy and reductant generation, biosynthesis, and CO(2) and NH(3) assimilation were identified . In contrast, genes for catabolism of organic compounds are limited . Genes encoding transporters for inorganic ions were plentiful, whereas genes encoding transporters for organic molecules were scant . Complex repetitive elements constitute ca . 5% of the genome . Among these are 85 predicted insertion sequence elements in eight different families . The strategy of N . europaea to accumulate Fe from the environment involves several classes of Fe receptors with more than 20 genes devoted to these receptors . However, genes for the synthesis of only one siderophore, citrate, were identified in the genome . This genome has provided new insights into the growth and metabolism of ammonia-oxidizing bacteria.

Water Res, 2003 Apr, 37(8), 1805 - 17
Effect of temperature and disinfection strategies on ammonia-oxidizing bacteria in a bench-scale drinking water distribution system; Pintar KD et al.; The establishment of ammonia-oxidizing bacteria (AOB), a group of autotrophic microorganisms responsible for nitrification in chloraminated distribution systems, was studied in a bench-scale distribution system . The potential significance of temperature and disinfectant residual associated with chloramination in full-scale drinking water distribution systems was assessed . Biofilm development was primarily monitored using AOB abundance and nitrite concentrations . The bench-scale system was initially operated under typical North American summer (22 degrees C) and fall (12 degrees C) temperatures, representing optimal and less optimal growth ranges for these microorganisms . Additional experimentation investigated AOB establishment at a suboptimal winter distribution system temperature of 6 degrees C . The effect of chloramine residual on AOB establishment was studied at higher (0.2-0.6mg/L) and lower (0.05-0.1mg/L) ranges, using a 3:1 (w/w) chlorine:ammonia dosing ratio . Conditions were selected to represent those typically found in a North American distribution system, in areas of low flow and longer retention times, respectively . Finally, the effect of a free chlorine residual on an established nitrifying biofilm was briefly examined . Results clearly indicate that AOB development occurs at all examined temperatures, as well as at selected monochloramine residuals . The maintenance of a disinfectant residual was difficult at times, but was more inhibitory to the nitrifying biofilm than the lower temperature . It can be concluded from the data that nitrification may not be adequately inhibited during the winter months, which may result in more advanced stages of nitrification the following season . Free chlorination can be effective in controlling AOB activity in the short term, but may not prevent reestablishment of a nitrifying biofilm upon return to chloramination.

Water Res, 2003 Apr, 37(8), 1794 - 804
Bio-augmentation by nitrification with return sludge; Salem S et al.; Bio-augmentation can be used to obtain nitrification in activated sludge processes that operate at sub-optimal solid retention times . In this study, we evaluated the potential of augmenting the endogenous nitrifying bacteria, by implementing a nitrification reactor in the sludge return line . This reactor can be fed with an internal N-rich flow (e.g . effluent from the sludge treatment) or with an external ammonium source . A mathematical model based on ASM1 was developed and used to evaluate the potential of this technique . The bio-augmentation studied here aimed to enhance the nitrification process of highly loaded activated sludge systems . A calibrated simulation model of a high loaded wastewater treatment plant in The Netherlands was used for this study . A side stream process (the named BABE process) was included in the simulation . This process was fed with the ammonia-rich water generated by sludge digestion and subsequent thickening by centrifugation (the so-called rejectwater) . An external source (artificial) of ammonium was also considered to evaluate the differences between the two origins of ammonium . The results showed that with the augmentation process, high loaded activated sludge systems can achieve nitrification even at low winter temperatures . The best effect is obtained for systems operating at approximately 50% of the minimal SRT without augmentation . The use of an internal ammonia source is more effective than an external source . The results of this study give a quantitative basis for the design of process internal bio-augmentation processes and the effect on the N-removal capacity of the treatment plant.

Inorg Chem, 2003 Jan 27, 42(2), 270 - 2
Selective one-electron reduction of Nitrosomonas europaea hydroxylamine oxidoreductase with nitric oxide; Cabail MZ et al.; Hydroxylamine oxidoreductase (HAO) from the autotrophic bacterium Nitrosomonas europaea catalyzes the 4-e- oxidation of NH2-OH to NO2- . The e- are transferred from NH2OH to an unusual 5-coordinate heme known as P460, which is the active site of HAO, and from there to an array of seven c-type hemes . NO., generated by laser flash photolysis of N,N'-bis(carboxymethyl)-N,N'-dinitroso-1,4-phenylenediamine, is found to act as a 1-e- donor to HAO . Most likely NO . binds P460 to yield a {Fe(NO)}6 moiety, which then hydrolyzes to give the reduced enzyme and NO2- . The {Fe(NO)}6 moiety is also a plausible final intermediate in the oxidation of NH2OH.

Water Res, 2003 May, 37(9), 2206 - 16
Evaluation of the impact of bioaugmentation and biostimulation by in situ hybridization and microelectrode; Satoh H et al.; Three rotating disk biofilm reactors were operated to evaluate whether bioaugmentation and biostimulation can be used to improve the start-up of microbial nitrification . The first reactor was bioaugmented during start-up period with an enrichment culture of nitrifying bacteria, the second reactor received a synthetic medium containing NH(4)(+) and NO(2)(-) to facilitate concomitant proliferation of ammonia- and nitrite-oxidizing bacteria, and the third reactor was used as a control . To evaluate the effectiveness of bioaugmentation and biostimulation approaches, time-dependent developments of nitrifying bacterial community and in situ nitrifying activity in biofilms were monitored by fluorescence in situ hybridization (FISH) technique and microelectrode measurements of NH(4)(+), NO(2)(-), NO(3)(-), and O(2) . In situ hybridization results revealed that addition of the enrichment culture of nitrifying bacteria significantly facilitated development of dense nitrifying bacterial populations in the biofilm shortly after, which led to a rapid start-up and enhancement of in situ nitrification activity . The inoculated bacteria could proliferate and/or survive in the biofilm . In addition, the addition of nitrifying bacteria increased the abundance of nitrifying bacteria in the surface of the biofilm, resulting in the higher nitrification rate . On the other hand, the addition of 2.1mM NO(2)(-) did not stimulate the growth of nitrite-oxidizing bacteria and did inhibit the proliferation of ammonia-oxidizing bacteria instead . Thus, the start-up of NO(2)(-) oxidation was unchanged, and the start-up of NH(4)(+) oxidation was delayed . In all the three biofilm reactors, data sets of time series analyses on population dynamics of nitrifying bacteria determined by FISH, in situ nitrifying activities determined by microelectrode measurements, and the reactor performances revealed an approximate agreement between the appearance of nitrifying bacteria and the initiation of nitrification activity, suggesting that the combination of these techniques was a very powerful monitoring tool to evaluate the effectiveness of bioaugmentation and biostimulation strategies.

Water Res, 2003 May, 37(9), 2140 - 8
Effects of chromium (VI) addition on the activated sludge process; Stasinakis AS et al.; The effect of hexavalent chromium, Cr(VI), addition on various operating parameters of activated sludge process was evaluated . To accomplish this, two parallel lab-scale continuous-flow activated sludge plants were operated . One was used as a control plant, while the other received Cr(VI) concentrations equal to 0.5, 1, 3 and 5 mgl(-1) . Cr(VI) concentrations of 0.5 mgl(-1) caused significant inhibition of the nitrification process (up to 74% decrease in ammonia removal efficiency) . On the contrary, the effect of Cr(VI) on organic substrate removal was minor for concentrations up to 5 mgl(-1), indicating that heterotrophic microorganisms are less sensitive to Cr(VI) than nitrifiers . Activated sludge floc size and structure characterization showed that Cr(VI) concentrations higher than 1 mgl(-1) reduced the filaments abundance, causing the appearance of pin-point flocs and free-dispersed bacteria . Additionally, the variability of protozoa and rotifers was reduced . As a result of disperse growth, effluent quality deteriorated, since significant amounts of suspended solids escaped with the effluent . Termination of Cr(VI) addition led to a partial recovery of the nitrification process (up to 57% recovery) . Similar recovery signs were not observed for activated sludge floc size and structure . Finally, shock loading to the control plant with 5 mgl(-1) Cr(VI) for 2 days resulted in a significant inhibition of the nitrification process and a reduction in filamentous microorganisms abundance.

Chemosphere, 2003 Feb, 50(6), 747 - 53
Mechanisms of nitrite accumulation occurring in soilnitrification; Shen QR et al.; Because low concentration of nitrite could be toxic to biological systems and high amounts of nitrite have been observed in a river of northern China since 1990, nitrite from agricultural soil sources should be investigated . In this paper, effects of levels of ammonium-N (NH4+-N), soil pH and nitrification inhibitors on NO2- accumulation, and duration of nitrite in soils were studied . Application of 11.2 mg of nitrapyrin kg(-1) soil or 11.2 mg of sodium azide kg(-1) soil dramatically suppressed nitrite occurrence . Within all incubation times and at all levels of ammonium-N input, we did not detect any measurable NO2-N accumulation in samples of Yellow-brown earth (pH 5.67), but observed huge accumulation in the 2 alkaline soils, Fluvo-aquic loam (pH 7.89) and Fluvo-aquic sand (pH 8.20) . The concentrations of nitrite in both alkaline soils were related to ammonium-N levels . The effect of pH on nitrite accumulation was demonstrated by using slurries of Fluvo-aquic sand under continuous aeration and buffers of different pH . Data showed that nitrite concentration increased with the elevated pH, yet that ammonia oxidizers from the original soil (pH 8.2) could adapt to the new medium of low pH (pH 5.35) . Dynamic changes of nitrite in soils amended with different rates of nitrite-N were also measured in 6 days . Thereby, we concluded that nitrite was unstable in acid soils, but durable in alkaline soils . The authors suggested that NO2- accumulation in field soils and its subsequent environmental impact should receive more attention.

Bioresour Technol, 2003 Feb, 86(3), 267 - 76
Medicinal and aromatic plant materials as nitrification inhibitors for augmenting yield and nitrogen uptake of Japanese mint (Mentha arvensis L . Var . Piperascens); Kiran U et al.; Pot experiments were conducted to evaluate the relative performance of medicinal and aromatic plant materials and dicyandiamide (DCD) as nitrification inhibitors to regulate transformation of N from urea . Their effect on the efficiencies of use of N by Japanese mint (Mentha arvensis cv . Hy 77) was tested . Urea was coated with these materials viz., Mentha spicata, Artemisia annua or DCD at the rate of 5% (w/w) of fertilizer urea using an appropriate coating technique . Nimin (tetranortriterpenoids, an ethanol extract of neem (Azadirachta indica Juss) coating was done at the rate of 1% w/w of urea . Fertilizer nitrogen was applied at 100 and 200 mg kg(-1) soil . These natural coating materials significantly increased the herb and essential oil yields of the crop at both rates of fertilizer nitrogen compared to urea alone and were found to be as effective as DCD in retarding NO3- formation in soil . Herb yield increased by 6-81% when compared to uncoated urea . The increase in essential oil yield ranged between 3% and 68% due to coating . The effectiveness of the nitrification-inhibitor--coated urea, however, varied with the soils used and the rate of fertilizer nitrogen applied . The results suggest that the natural products could be potential nitrification inhibitors for increasing fertilizer N use efficiency.

Environ Pollut, 2003, 121(3), 363 - 76
The interactions between plant growth, vegetation structure and soil processes in semi-natural acidic and calcareous grasslands receiving long-term inputs of simulated pollutant nitrogen deposition; Carroll JA et al.; Regular applications of ammonium nitrate (35-140 kg N ha(-1) year(-1)) and ammonium sulphate (140 kg N ha(-1) year(-1)) to areas of acidic and calcareous grassland in the Derbyshire Peak District over a period of 6 years, have resulted in significant losses in both overall plant cover, and the abundance of individual species, associated with clear and dose-related increases in shoot nitrogen content . No overall growth response to nitrogen treatment was seen at any stage in the experiment . Phosphorus additions to the calcareous plots did however lead to significant increases in plant cover and total biomass, indicative of phosphorus limitation in this system . Clear and dose-related increases in soil nitrogen mineralization rates were also obtained, consistent with marked effects of the nitrogen additions on soil processes . High nitrification rates were seen on the calcareous plots, and this process was associated with significant acidification of the 140 kg N ha(-1) year(-1) treatments.

Environ Pollut, 2003, 121(3), 333 - 44
Inferred effects of cloud deposition on forest floor nutrient cycling and microbial properties along a short elevation gradient; Lavoie M et al.; Cloud water deposition often increases with elevation, and it is widely accepted that this cloud water increases acid loading to upland forest ecosystems . A study was undertaken in south-eastern Quebec to determine if a 250 m elevation gradient (i.e . 420-665 m), along a uniform sugar-maple stand on the slope of Mount Orford, corresponded to a pH gradient in the forest floor and to predictable changes in soil nutrient availability and microbial properties . Precipitation data from a nearby study, and a photographic survey, provided presumptive evidence that this elevation gradient corresponded to a strong gradient in cloud water deposition . Forest floor temperature did not differ significantly across elevations . Forest floor moisture content was significantly higher, whereas pH and exchangeable Ca and Mg were significantly lower, at the higher elevations . Average seasonal net nitrification rates, determined by long-term laboratory incubations, did not differ significantly across elevations, whereas average seasonal net ammonification rates were significantly higher at higher elevations . Basal respiration rates and microbial biomass did not differ significantly across elevations, but metabolic quotient was significantly higher at higher elevations indicating possible environmental stress on forest floor microbial communities due to cloud water deposition . Anaerobic N mineralisation rates were significantly higher at higher elevations suggesting that N-limited microbial communities frequently exposed to cloud cover can be important short-term sinks for atmospheric N, thereby contributing to increase the active-N fraction of forest floors . We conclude that, where no significant changes in vegetation or temperature occur, elevation gradients can still be used to understand the spatial variability of nutrient cycles and microbial properties.

Environ Toxicol Chem, 2003 Apr, 22(4), 821 - 9
Activity and population dynamics of heterotrophic and ammonia-oxidizing microorganisms in soil surrounding sludge bands spiked with linear alkylbenzene sulfonate: a field study; Brandt KK et al.; Recent research has documented soil microorganisms to be rather sensitive to linear alkylbenzene sulfonates (LAS), which may enter the soil environment in considerable quantities following sewage sludge disposal . We here report field effects of LAS on selected microbial populations present in a sandy soil surrounding well-defined sludge bands spiked with high but realistic LAS levels (7.1 or 31.3 g/kg) . Surprisingly, LAS had no effect on heterotrophic respiration in the sludge compartment per se but stimulated activity and metabolic quotient (microbial activity per unit of biomass) in the surrounding soil . By contrast, autotrophic ammonia oxidation was initially inhibited in the LAS-spiked sludge . This led to dramatic transient increases of NH4+ availability in the sludge and surrounding soil, subsequently stimulating soil ammonia oxidizers . As judged from a Nitrosomonas europaea bioluminescence toxicity assay, however, LAS or other sludge components never accumulated to toxic levels in the soil compartments and the LAS tolerance of the indigenous microbes further remained unchanged following LAS exposure . LAS effects on the investigated microbial populations largely occurred during the first two months and were confined to soil closer than 30 mm from LAS-spiked sludge . Our results strongly suggest that disposal of LAS-contaminated sludge does not pose a major risk to the function of the soil microbial community under field conditions.

Environ Pollut, 2003, 123(3), 355 - 64
Nitrogen biogeochemistry in the Adirondack Mountains of New York: hardwood ecosystems and associated surface waters; Mitchell MJ et al.; Studies on the nitrogen (N) biogeochemistry in Adirondack northern hardwood ecosystems were summarized . Specific focus was placed on results at the Huntington Forest (HFS), Pancake-Hall Creek (PHC), Woods Lake (WL), Ampersand (AMO), Catlin Lake (CLO) and Hennessy Mountain (HM) . Nitrogen deposition generally decreased from west to east in the Adirondacks, and there have been no marked temporal changes in N deposition from 1978 through 1998 . Second-growth western sites (WL, PHC) had higher soil solution NO(3-) concentrations and fluxes than the HFS site in the central Adirondacks . Of the two old-growth sites (AMO and CLO), AMO had substantially higher NO(3-) concentrations due to the relative dominance of sugar maple that produced litter with high N mineralization and nitrification rates . The importance of vegetation in affecting N losses was also shown for N-fixing alders in wetlands . The Adirondack Manipulation and Modeling Project (AMMP) included separate experimental N additions of (NH4)2SO4 at WL, PHC and HFS and HNO3 at WL and HFS . Patterns of N loss varied with site and form of N addition and most of the N input was retained . For 16 lake/watersheds no consistent changes in NO(3-) concentrations were found from 1982 to 1997 . Simulations suggested that marked NO(3-) loss will only be manifested over extended periods . Studies at the Arbutus Watershed provided information on the role of biogeochemical and hydrological factors in affecting the spatial and temporal patterns of NO(3-) concentrations . The heterogeneous topography in the Adirondacks has generated diverse landscape features and patterns of connectivity that are especially important in regulating the temporal and spatial patterns of NO(3-) concentrations in surface waters.

Environ Microbiol, 2003 Apr, 5(4), 278 - 86
Activity and population structure of nitrifying bacteria in an activated-sludge reactor containing polymer beads; Tanaka J et al.; Photo-crosslinked polymer beads were introduced into a laboratory activated-sludge unit containing municipal sewage sludge and the effect on nitrifying capacity was examined . The ammonia load started at a nitrogen-loading rate of 0.02 kg m(-3) day(-1) and was increased stepwise . It was found that the bead-containing unit could almost completely oxidize ammonia (over 95%) up to a nitrogen-loading rate of 0.216 kg m(-3) day(-1), whereas the maximum loading rate of the control unit (without polymer beads) was 0.096 kg m(-3) day(-1) . The nitrifying potential of suspended and bead-associated organisms in the bead-containing unit was measured under different loading conditions . It was found that the bead-associated organisms exhibited high specific activities under high loading conditions and that the contribution of the bead-associated organisms to nitrification was greater than that of the suspended solids under these conditions . The bacterial population dynamics in the suspended solids and bead-associated organisms were analysed by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments and by fluorescence in situ hybridization with group-specific probes . Among the known nitrifying organisms, ammonia-oxidizing beta-proteobacteria and Nitrospira-related organisms were detected by these approaches . A comparison of the activity dynamics and population dynamics, however, suggested a possibility that other organisms may also have been involved in the nitrification process under high loading conditions.

Rapid Commun Mass Spectrom, 2003, 17(7), 738 - 45
Nitrogen isotopomer site preference of N2O produced by Nitrosomonas europaea and Methylococcus capsulatus Bath; Sutka RL et al.; The relative importance of individual microbial pathways in nitrous oxide (N(2)O) production is not well known . The intramolecular distribution of (15)N in N(2)O provides a basis for distinguishing biological pathways . Concentrated cell suspensions of Methylococcus capsulatus Bath and Nitrosomonas europaea were used to investigate the site preference of N(2)O by microbial processes during nitrification . The average site preference of N(2)O formed during hydroxylamine oxidation by M . capsulatus Bath (5.5 +/- 3.5 per thousand) and N . europaea (-2.3 +/- 1.9 per thousand) and nitrite reduction by N . europaea (-8.3 +/- 3.6 per thousand) differed significantly (ANOVA, f((2,35)) = 247.9, p = 0) . These results demonstrate that the mechanisms for hydroxylamine oxidation are distinct in M . capsulatus Bath and N . europaea . The average delta(18)O-N(2)O values of N(2)O formed during hydroxylamine oxidation for M . capsulatus Bath (53.1 +/- 2.9 per thousand) and N . europaea (-23.4 +/- 7.2 per thousand) and nitrite reduction by N . europaea (4.6 +/- 1.4 per thousand) were significantly different (ANOVA, f((2,35)) = 279.98, p = 0) . Although the nitrogen isotope value of the substrate, hydroxylamine, was similar in both cultures, the observed fractionation (delta(15)N) associated with N(2)O production via hydroxylamine oxidation by M . capsulatus Bath and N . europaea (-2.3 and 26.0 per thousand, respectively) provided evidence that differences in isotopic fractionation were associated with these two organisms . The site preferences in this study are the first measured values for isolated microbial processes . The differences in site preference are significant and indicate that isotopomers provide a basis for apportioning biological processes producing N(2)O .

Chemosphere, 2003 Jan, 50(1), 171 - 6
BOD5 measurements of water presenting inhibitory Cu2+ . Implications in using of BOD to evaluate biodegradability of industrial wastewaters; Hufschmid A et al.; In industrial effluents, the presence of an infinite number of possible mixtures of substances and the high variability of chemical conditions ask for an evaluation of biodegradability by a global and simple method . Biological oxygen demand after five days (BOD5) using synthetic wastewater was studied by two different ways: dilution and manometric methods . It can therefore be established that BOD5 obtained by adding manufactured inocula to the synthetic medium (effluent containing known and easily biodegradable substances) is close to the values obtained with inocula taken from the treated effluent of an urban and a rural purification plant . It was found that BOD5 measurement of effluents presenting factors affecting biodegradation, similar of those found in industrial effluents, is very questionable . The BOD is in this case influenced by the synergic and antagonist interactions between numerous and variable parameters like as pH, nature and concentration of inoculum, concentration of nutriments, amount and nature of assimilable substances, presence of toxicants, and presence of nitrification inhibitors, which are typical of real industrial wastewaters.

Chemosphere, 2003 Jan, 50(1), 145 - 53
Biological treatment process of air loaded with an ammonia and hydrogen sulfide mixture; Malhautier L et al.; The physico-chemical characteristics of granulated sludge lead us to develop its use as a packing material in air biofiltration . Then, the aim of this study is to investigate the potential of unit systems packed with this support in terms of ammonia and hydrogen sulfide emissions treatment . Two laboratory scale pilot biofilters were used . A volumetric load of 680 g H2S m(-3) empty bed day(-1) and 85 g NH3 m(-3) empty bed day(-1) was applied for eight weeks to a unit called BGSn (column packed with granulated sludge and mainly supplied with hydrogen sulfide); a volumetric load of 170 g H2S m(-3) empty bed day(-1) and 340 g NH3 m(-3) empty bed day(-1) was applied for eight weeks to the other called BGNs (column packed with granulated sludge and mainly supplied with ammonia) . Ammonia and hydrogen sulfide elimination occur in the biofilters simultaneously . The hydrogen sulphide and ammonia removal efficiencies reached are very high: 100% and 80% for BGSn; 100% and 80% for BGNs respectively . Hydrogen sulfide is oxidized into sulphate and sulfur . The ammonia oxidation products are nitrite and nitrate . The nitrogen error mass balance is high for BGSn (60%) and BGNs (36%) . This result could be explained by the denitrification process which would have occurred in anaerobic zones . High percentages of ammonia or hydrogen sulfide are oxidized on the first half of the column . The oxidation of high amounts of hydrogen sulfide would involve some environmental stress on nitrifying bacterial growth and activity.

Chemosphere, 2003 Jan, 50(1), 121 - 9
Treatment of domestic wastewater by an hydroponic NFT system; Vaillant N et al.; The objectives in this work were to investigate a conceptual layout for an inexpensive and simple system that would treat primary municipal wastewater to discharge standards . A commercial hydroponic system was adapted for this study and the wastewater was used to irrigate Datura innoxia plants . Influent and effluent samples were collected once a month for six months and analysed to determine the various parameters relating to the water quality . The legal discharge levels for total suspended, biochemical oxygen demand and chemical oxygen demand were reached with the plant system after 24 h of wastewater treatment . Total nitrogen and total phosphorus reduction were also obtained . NH4(+)-N was reduced by 93% with nitrification proving to be the predominant removal process . Significant nitrification occurred when the BOD5 level dropped 45 mg/l . Similar results were obtained for six months although the sewage composition varied widely . D . innoxia develops and uses the wastewater as the unique nutritive source.

Int J Phytoremediation, 2002, 4(2), 127 - 41
Removal of N, P, BOD5, and coliform in pilot-scale constructed wetland systems; Jin G et al.; Pilot-scale surface-flow (SF), subsurface-flow (SSF), and floating aquatic plant (FAP) constructed wetland system designs were installed and evaluated to determine the effectiveness of constructed wetlands to treat tertiary effluent wastewater in a Midwestern U.S . climate (central Illinois) . Average ammonia-nitrogen (N) concentrations decreased approximately 50% in the SSF system design, suggesting that this design had the highest nitrification rate . Nitrate-N concentrations decreased by over 60% in the FAP system design, possibly due to dissimilatory reduction or plant uptake . Total phosphorus (P) concentration reductions of 25 to 40% were observed in all three system designs . Five-day biochemical oxygen demand (BOD5) and dissolved oxygen (DO) results suggested that biodegradation was highest in the SSF system design and lowest in the FAP system design . Greater than 90% concentration reductions of total coliform and E . coli recovered were also observed following treatment in all three system designs . The FAP system design appeared to yield the highest concentration reduction efficiency for E . coli, possibly due to increased sunlight and related bacteriocidal ultraviolet light exposure . Ongoing experiments will test regularly for a variety of vegetative, water quality, and biological conditions for longer time periods in order to gain a better understanding of the pilot constructed wetland system design kinetics.

Bioresour Technol, 2003 Jan, 86(2), 139 - 45
Evaluation of Anammox and denitrification during anaerobic digestion of poultry manure; Dong X et al.; Two approaches based on ne w process development and biological nitrogen transformation were investigated in a bench study for removing nitrogen as N2 gas from poultry waste while stabilizing the wastes . The process, known as "Anammox", was explored in batch anaerobic culture using serum bottles . The Anammox process involves the use of nitrite as an electron acceptor in the bacterially mediated oxidation of ammonia to yield N2 . Studies are described wherein nitrite was added to poultry waste and the effects on ammonium levels were monitored . About 13-22% ammonium removal was observed with the inoculation of returned activated sludge, and the total ammonium reduction was not proportional to the reduction of nitrite, thereby suggesting that Anammox was less competitive under the conditions in our studies . The addition of nitrite and nitrate was not inhibitory to the process based on gas generation and COD reduction . The classical nitrogen removal process of nitrification followed with denitrification offers a more reliable basis for nitrogen removal from poultry wastes.

Oecologia, 2003 Mar, 134(4), 569 - 77 Epub 2003 Jan 30.
Delta15N values of tropical savanna and monsoon forest species reflect root specialisations and soil nitrogen status; Schmidt S et al.; A large number of herbaceous and woody plants from tropical woodland, savanna, and monsoon forest were analysed to determine the impact of environmental factors (nutrient and water availability, fire) and biological factors (microbial associations, systematics) on plant delta(15)N values . Foliar delta(15)N values of herbaceous and woody species were not related to growth form or phenology, but a strong relationship existed between mycorrhizal status and plant delta(15)N . In woodland and savanna, woody species with ectomycorrhizal (ECM) associations and putative N(2)-fixing species with ECM/arbuscular (AM) associations had lowest foliar delta(15)N values (1.0-0.6 per thousand ), AM species had mostly intermediate delta(15)N values (average +0.6 per thousand ), while non-mycorrhizal Proteaceae had highest delta(15)N values (+2.9 to +4.1 per thousand ) . Similar differences in foliar delta(15)N were observed between AM (average 0.1 and 0.2 per thousand ) and non-mycorrhizal (average +0.8 and +0.3 per thousand ) herbaceous species in woodland and savanna . Leguminous savanna species had significantly higher leaf N contents (1.8-2.5% N) than non-fixing species (0.9-1.2% N) indicating substantial N acquisition via N(2) fixation . Monsoon forest species had similar leaf N contents (average 2.4% N) and positive delta(15)N values (+0.9 to +2.4 per thousand ) . Soil nitrification and plant NO(3)(-) use was substantially higher in monsoon forest than in woodland or savanna . In the studied communities, higher soil N content and nitrification rates were associated with more positive soil delta(15)N and plant delta(15)N . In support of this notion, Ficus, a high NO(3)(-) using taxa associated with NO(3)(-) rich sites in the savanna, had the highest delta(15)N values of all AM species in the savanna . delta(15)N of xylem sap was examined as a tool for studying plant delta(15)N relations . delta(15)N of xylem sap varied seasonally and between differently aged Acacia and other savanna species . Plants from annually burnt savanna had significantly higher delta(15)N values compared to plants from less frequently burnt savanna, suggesting that foliar (15)N natural abundance could be used as marker for assessing historic fire regimes . Australian woodland and savanna species had low leaf delta(15)N and N content compared to species from equivalent African communities indicating that Australian biota are the more N depauperate . The largest differences in leaf delta(15)N occurred between the dominant ECM Australian and African savanna (miombo) species, which were depleted and enriched in (15)N, respectively . While the depleted delta(15)N of Australian ECM species are similar to those of previous reports on ECM species in natural plant communities, the (15)N-enriched delta(15)N of African ECM species represent an anomaly.

Oecologia, 2003 Mar, 134(4), 547 - 53 Epub 2003 Jan 25.
Responses of soil nitrogen dynamics in a Mojave Desert ecosystem to manipulations in soil carbon and nitrogen availability; Schaeffer SM et al.; We investigated the effects of changes in soil C and N availability on N mineralization, nitrification, denitrification, NH(3) volatilization, and soil respiration in the Mojave Desert . Results indicate a C limitation to microbial N cycling . Soils from underneath the canopies of Larrea tridentata (DC.) Cov., Pleuraphis rigida Thurber, and Lycium spp . exhibited higher rates of CO(2 ) flux, lower rates of NH(3) volatilization, and a decrease in inorganic N (NH(4)(+)-N and NO(3)(-)-N) with C addition . In addition to C limitation, soils from plant interspaces also exhibited a N limitation . Soils from all locations had net immobilization of N over the course of a 15-day laboratory incubation . However, soils from interspaces had lower rates of net nitrification and potential denitrification compared to soils from under plant canopies . The response to changes in C availability appears to be a short-term increase in microbial immobilization of inorganic N . Under controlled conditions, and over a longer time period, the effects of C and N availability appear to give way to larger differences due to spatial location . These findings have implications for ecosystems undergoing changes in soil C and N availability due to such processes as desertification, exotic species invasions, or elevated atmospheric CO(2) concentration.

Endeavour, 2003 Mar, 27(1), 16 - 21
A field of great promise: soil bacteriology in America, 1900-1925; Kupferberg ED; In the first decades of the 20th century, soil bacteriologists promised to revolutionize farming practice, much in the same way that medical bacteriologists, in the previous century, had transformed pathology, public health and sanitary engineering . Following the isolation of the microorganisms responsible for nitrification and nitrogen fixation, American soil scientists anticipated the time when farmers could 'seed' their crops and lands with these beneficial bacteria . Soil bacteriologists, during the early 20th century, never fulfilled the promise of supplying a biological source of unending soil fertility . However, in their search for productive microbes, these same researchers directed attention to the underappreciated dimensions of bacterial metabolism and microbial ecology.

Environ Technol, 2003 Jan, 24(1), 51 - 8
Integrated horizontal-flow anaerobic and radial-flow aerobic reactors for the removal of organic matter and nitrogen from domestic sewage; Vieira LG et al.; This paper presents the conception and discusses the results obtained from the operation of an integrated biological anaerobic/aerobic/anaerobic system composed of horizontal-flow anaerobic and radial-flow aerobic reactors for domestic sewage treatment . The performance of a horizontal-flow anaerobic immobilized biomass reactor, with five stages,followed by a radial-flow aerobic immobilized biomass reactor was evaluated along 22 weeks . After the 14th week, the last stage of the HAIB reactor was used as a denitrifying unit . Polyurethane foam cubic matrices with 1-cm sides were used as support for biomass immobilization in all the units . The influent domestic sewage presented mean chemical oxygen demand of 365 +/- 71 mg . 1(-1) and the temperature was 23 +/- 3degrees C . The integrated system achieved COD removal efficiency of 90% while the maximum ammonium removal efficiency was 97% in the aerobic post-treatment unit . The nitrification process was found to be better represented by first-order reactions in series model . The apparent first-order kinetic coefficient for nitrate formation was about 50 times higher than that estimated for the nitrite formation . The denitrification process was well represented by a Monod-type kinetic model . The maximum specific denitrifying rate and the half-saturation coefficient were 2.9 x 10(-4) mg NO(3)(-)-N mg(-1) VSS h(-1) and 19.4 mg NO(3)(-)-N 1(-1), respectively.

Environ Technol, 2003 Jan, 24(1), 31 - 42
Comparison of suspended growth and hybrid systems for nitrogen removal in ammonium bisulfite pulp mill wastewater; Seok JH et al.; A series of bench-scale nitrification/denitrification tests were carried out with both suspended growth and hybrid bioreactors . The hybrid reactor was filled with plastic (polyethylene) media to evaluate the effects of biofilm.Two types of reactor configurations were tested; 4-compartment and 6-compartment modes.The experiments were initiated with a half-strength pulp and paper wastewater and its strength increased stepwise to the raw wastewater . Solid retention time was fixed at 10 days after a start-up period while hydraulic retention time was extensively varied from 3.5 to 0.5 days . The results from each type of reactor were compared in terms of nitrification/denitrification efficiency and stability . Experimental results demonstrate that the hybrid system showed greater stability in nitrification and higher denitrification efficiency than the suspended growth system . In the hybrid system, attached volatile solids formed 61- 72% of total volatile solids in the reactor and the amount of attached volatile solids insignificantly varied with the organic loading rate (0.37 - 2.76 kg COD M(-3) d(-1)) after initial biomass attachment . Under the conditions tested (0.1 - 2.8 kg COD m(-3) d(-1)), organic loading rate insignificantly influenced the nitrification . Better performance was obtained in denitrification when the anoxic zone was better isolated from the aerobic compartments (6-compartment mode) . Overall, the hybrid system with fixed-film growth had better resistance to upset caused by transients such as changes in influent composition or hydraulic retention time.

Environ Sci Pollut Res Int, 2002, Spec No 2, 37 - 41
Nitrate dynamics in an Alpine forest site (Mühleggerköpfl) . O and N stable isotope analysis in natural water samples; Haberhauer G et al.; Stable isotope analysis of 15N/14N and 18O/16O-nitrate was used to investigate the nitrate dynamics and potential groundwater pollution in an Alpine forest stand in Tyrol/Austria . The dynamics of delta15-N(nitrate) values were followed in a forest ecosystem . The stable isotopic values of the throughfall are comparable with other studies . The completely decoupled dynamics of the delta15-N(nitrate) of the precipitation and the surface water was observed . High variations in delta15N-nitrate values in rainfall indicate that nitrate of different sources is deposited at that site . A significant correlation between the delta15N(nitrate) values of the surface water and soil water was obtained, while no significant correlation between the delta15N(nitrate) values of any precipitation sample with the surface water could be found . This suggests that the main source of nitrate in soil water originates from microbiological activity such as nitrification reactions and less from nitrate input by deposition . The results of delta18O(nitrate) measurements strongly supported the microbiological origin of nitrate in the surface and soil water In an additional lysimeter experiment, 15N-labelled nitrate was applied to study nitrate transport in soil . After 130 days and the collection of 300 L leachate, a total of 52% of the applied nitrate was detected in seepage water.

Environ Sci Pollut Res Int, 2002, Spec No 2, 23 - 30
Gaseous nitrogen losses from a forest site in the North Tyrolean Limestone Alps; Hartel E et al.; Microorganisms are responsible for the mineralisation of organic nitrogen in soils . NH4+ can be further oxidised to NO3- during nitrification and NO3- can be reduced to gaseous nitrogen compounds during denitrification . During both processes, nitrous oxide (N2O), which is known as greenhouse gas, can be lost from the ecosystem . The aim of this study was to quantify N2O emissions and the internal microbial N cycle including net N mineralisation and net nitrification in a montane forest ecosystem in the North Tyrolean Limestone Alps during an 18-month measurement period and to estimate the importance of these fluxes in comparison with other components of the N cycle . Gas samples were taken every 2 weeks using the closed chamber method . Additionally, CO2 emission rates were measured to estimate soil respiration activity . Net mineralisation and net nitrification rates were determined by the buried bag method every month . Ion exchange resin bags were used to determine the N availability in the root zone . Mean N2O emission rate was 0.9 kg N ha(-1) a(-1), which corresponds to 5% of the N deposited in the forest ecosystem . The main influencing factors were air and soil temperature and NO3- accumulated on the ion exchange resin bags . In the course of net ammonification, 14 kg NH4+-N ha(-1) were produced per year . About the same amount of NO3--N was formed during nitrification, indicating a rather complete nitrification going on at the site . NO3- concentrations found on the ion exchange resin bags were about 3 times as high as NO3- produced during net nitrification, indicating substantial NO3- immobilisation . The results of this study indicate significant nitrification activities taking place at the Muhleggerkopfl.

Environ Sci Technol, 2003 Feb 15, 37(4), 728 - 34
Impact of metal sorption and internalization on nitrification inhibition; Hu Z et al.; The goal of this study was to explore the relationship between metal extracellular sorption, intracellular accumulation, and nitrification inhibition . Metal sorption on nitrifying biomass was rapid and could be described by linear partitioning with partition coefficients (Kp) of 20.3 +/- 0.1, 0.4 +/- 0.0, 0.1 +/- 0.0, and 0.2 +/- 0.0 L/g biomass chemical oxygen demand for Cu, Zn, Ni, and Cd, respectively . On the other hand, intracellular Zn, Ni, and Cd concentrations continued to increase with time beyond 12 h after metal addition, whereas intracellular Cu attained equilibrium after 4 h . Metal internalization kinetics could be described by an intraparticle diffusion model, with characteristic diffusion time constants (td) of 9.4, 64.6, 80.5, and 66.1 h for Cu, Zn, Ni, and Cd, respectively . Ultimate internalized percentages of the total cell-associated metal were 1.4 +/- 0.0, 4.3 +/- 0.5,7.6 +/- 1.0, and 2.7 +/- 0.2% for Cu, Zn, Ni, and Cd, respectively . Nitrification inhibition was not a function of the sorbed metal fraction but correlated well with intracellular Zn, Ni, or Cd fractions . An intraparticle diffusion model coupled with a saturation-type biological toxicity model fit the inhibition data for varying initial Cd concentrations and exposure periods . In contrast, no relationship between intracellular or sorbed Cu concentrations and nitrification inhibition was observed . In the presence of 1 mM Cu, less than 13.3 +/- 10.5% cells remained viable as compared to 72.8 +/- 7.5,104.8 +/- 1.7, and 84.7 +/- 7.0% (assumed 100% viable cells in metal-free control) in the presence of 1 mM Zn, Ni, and Cd, respectively . Hence, the observations that inhibition by metals such as Zn, Ni, and Cd is related to their intracellular fraction and the slow kinetics of metal internalization indicate that metal inhibition can easily be underpredicted from short-term batch assays . Furthermore, the inhibitory mechanism of Cu was very different from Zn, Ni, and Cd and may involve rapid loss of membrane integrity.

Water Sci Technol, 2003, 47(2), 149 - 55
Rapid automated detection of nitrification kinetics using respirometry; Langergraber G et al.; There is no doubt that respirometry is a useful measurement principle in the field of wastewater treatment . Although a large variety of methods and case studies have been published, respirometry has become neither a standard tool for control nor for assessment and optimisation of treatment plants . drawback of the conventional method for determining nitrification kinetics is the long experimental time . This disadvantage can be avoided by "turning over" the experiment . Starting with low ammonia concentrations the steep slope of the Monod curve is measured first . The low concentration branch of the Monod curve is also the part where e.g . inhibition can be detected . Therefore the proposed procedure allows us to speed up the measurement of nitrification kinetics and to measure nitrification inhibition on-line.

Water Sci Technol, 2003, 47(2), 141 - 8
An integrated sensor for the monitoring of aerobic and anoxic activated sludge activities in biological nitrogen removal plants; Sin G et al.; An integrated sensor is developed as a tool for monitoring the activated sludge activity on which the performance of the treatment plant depends . The sensor provides information-rich data of high frequency obtained from respirometric-titrimetric and nitrate measurements in one single set-up . The sensor is shown to successfully monitor and provide in-depth insight into nitrification, denitrification and carbon source degradation processes occurring in BNR plants . Based on the experimental results it is hypothesized the ratio of NUR to OUR rather reflects the rate of carbon source uptake (storage) under anoxic and aerobic conditions than growth process.

J Hazard Mater, 2003 Mar 17, 98(1-3), 275 - 93
Hot acid hydrolysis as a potential treatment of thickened sewage sludge; Neyens E et al.; Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing organic and mineral components and being mechanically dewatered to e.g . 20-25% DS in centrifuges . Both the reduction of the amount of sludge produced and improving its dewaterability are hence of paramount importance . Hot acid hydrolysis can meet these objectives . The current paper describes the results of detailed investigations with respect to acid hydrolysis of thickened sludge (5-6% DS content) . A comparison with traditional thermal hydrolysis is also included . As a result of the experimental investigations, it can be concluded that hot acid hydrolysis is efficient in both reducing the residual sludge amounts and improving the dewaterability . Under the proposed optimum conditions it is found that (i) the amount of hydrolysed DS is approximately 70% lower than the initial untreated amount, (ii) the DS-solid content of the dewatered cake is increased from 22.5% (initial untreated) to at least twice this value, (iii) the rate of mechanical dewatering is not significantly affected . The preferential release of ODS into the water phase, and the increased BOD/COD-ratio through hydrolysis, turn this recycle water phase into a possible carbon-source for nitrification/denitrification . Heavy metals and phosphates are also released in the water phase, and can be subsequently precipitated .

Ying Yong Sheng Tai Xue Bao, 2002 Nov, 13(11), 1417 - 20
{Effects of neem seed extracts on nitrogen use efficiency in two different soils}; Zhang X et al.; Incubation test and pot experiments were conducted with haplic luvisols and hydragric anthrosols to study the effects of neem seed extracts (N I, N II) on nitrification and immobilization of ammonium sulfate . N I could significantly inhibit the nitrification of N applied to the two soils . N II was effective in promoting the immobilization of NH4+(-)N . Pot experiments showed that N II could increase the use efficiency of chemical nitrogen significantly in fimic anthrosols.

Appl Environ Microbiol, 2003 Mar, 69(3), 1511 - 20
Bioaugmentation as a tool to protect the structure and function of an activated-sludge microbial community against a 3-chloroaniline shock load; Boon N et al.; Bioaugmentation of bioreactors focuses on the removal of xenobiotics, with little attention typically paid to the recovery of disrupted reactor functions such as ammonium-nitrogen removal . Chloroanilines are widely used in industry as a precursor to a variety of products and are occasionally released into wastewater streams . This work evaluated the effects on activated-sludge reactor functions of a 3-chloroaniline (3-CA) pulse and bioaugmentation by inoculation with the 3-CA-degrading strain Comamonas testosteroni I2 gfp . Changes in functions such as nitrification, carbon removal, and sludge compaction were studied in relation to the sludge community structure, in particular the nitrifying populations . Denaturing gradient gel electrophoresis (DGGE), real-time PCR, and fluorescent in situ hybridization (FISH) were used to characterize and enumerate the ammonia-oxidizing microbial community immediately after a 3-CA shock load . Two days after the 3-CA shock, ammonium accumulated, and the nitrification activity did not recover over a 12-day period in the nonbioaugmented reactors . In contrast, nitrification in the bioaugmented reactor started to recover on day 4 . The DGGE patterns and the FISH and real-time PCR data showed that the ammonia-oxidizing microbial community of the bioaugmented reactor recovered in structure, activity, and abundance, while the number of ribosomes of the ammonia oxidizers in the nonbioaugmented reactor decreased drastically and the community composition changed and did not recover . The settleability of the activated sludge was negatively influenced by the 3-CA addition, with the sludge volume index increasing by a factor of 2.3 . Two days after the 3-CA shock in the nonbioaugmented reactor, chemical oxygen demand (COD) removal efficiency decreased by 36% but recovered fully by day 4 . In contrast, in the bioaugmented reactor, no decrease of the COD removal efficiency was observed . This study demonstrates that bioaugmentation of wastewater reactors to accelerate the degradation of toxic chlorinated organics such as 3-CA protected the nitrifying bacterial community, thereby allowing faster recovery from toxic shocks.

Appl Environ Microbiol, 2003 Mar, 69(3), 1359 - 71
Community structure of ammonia-oxidizing bacteria within anoxic marine sediments; Freitag TE et al.; The potential for oxidation of ammonia in anoxic marine sediments exists through anaerobic oxidation by Nitrosomonas-like organisms, utilizing nitrogen dioxide, coupling of nitrification, manganese reduction, and anaerobic oxidation of ammonium by planctomycetes (the Anammox process) . Here we describe the presence of microbial communities with the potential to carry out these processes in a natural marine sediment system (Loch Duich, Scotland) . Natural microbial communities of Planctomycetales-Verrucomicrobia and beta- and gamma-proteobacterial ammonia-oxidizing bacteria were characterized by analysis of 16S rRNA genes amplified using group-specific primers by PCR- and reverse transcription-PCR amplification of 16S rDNA and RNA, respectively . Amplification products were analyzed by sequencing of clones and by denaturant gradient gel electrophoresis (DGGE) . Amplification of primers specific for Planctomycetales-Verrucomicrobia and beta-proteobacterial ammonia-oxidizing bacteria generated products at all sampling sites and depths, but no product was generated using primers specific for gamma-proteobacterial ammonia-oxidizing bacteria . 16S rDNA DGGE banding patterns indicated complex communities of beta-proteobacterial ammonia-oxidizing bacteria in anoxic marine sediments . Phylogenetic analysis of sequences from clones and those excised from DGGE gels suggests dominance of Nitrosospira cluster 1-like organisms and of strains belonging to a novel cluster represented in dominant bands in 16S rRNA DGGE banding patterns . Their presence indicates a group of organisms closely related to recognized beta-proteobacterial ammonia-oxidizing bacteria that may be selected in anoxic environments and may be capable of anoxic ammonia oxidation . Sequence analysis of planctomycete clone libraries and sequences excised from DGGE gels also demonstrated a diverse microbial community and suggested the presence of new subdivisions, but no sequence related to recognized Anammox organisms was detected.

Huan Jing Ke Xue, 2002 Nov, 23(6), 57 - 61
{Pilot study on subsurface wastewater infiltration system applied in rural sewage treatment}; Zhang J et al.; A pilot plant of subsurface wastewater infiltration system (SWIS) filled with red clay was tested to treat rural sewage with hydraulic loading of 2 cm/d . The experiment results showed that average removal rates of COD, NH4(+)-N, total phosphorus, and total nitrogen were 84.7%, 70.0%, 98.0% and 77.7%, with average effluent concentrations of COD, NH4(+)-N, total phosphorus, and total nitrogen being 11.7 mg/L, 4.0 mg/L, 0.04 mg/L and 4.7 mg/L respectively, which met the standard for water reuse issued by the Ministry of Construction of China . Nitrogen removal mechanism analysis revealed that nitrogen in the influent was mainly eliminated through biological removal via nitrification/denitrification processes . In the pilot system, denitrification was well proceeded but nitrification was not satisfactory . How to improve nitrification performance through change of soil environment was the key to enhance nitrogen removal rate . The measurement results of redox potential in the filled soil showed that reductive property of soil was main hindrance to nitrification process.

J Bacteriol, 2003 Mar, 185(6), 2036 - 41
Excision and integration of cassettes by an integron integrase of Nitrosomonas europaea; Leon G et al.; We found in the environmental strain Nitrosomonas europaea a chromosomal integron-like structure with an integrase gene, intI(Neu) . We have tested the capacity of the IntINeu integrase to excise and integrate several resistance gene cassettes . The results allow us to consider IntINeu a new functional integron integrase.

J Air Waste Manag Assoc, 2003 Feb, 53(2), 217 - 26
Degradation of toluene, xylene, and trimethylbenzene vapors by biofiltration: a comparison; Delhomenie MC et al.; This paper presents a comparative study of the biodegradation of three aromatic volatile compounds in a compost-based biofilter: toluene, xylene, and 1,2,4-trimethylbenzene, used in the course of this work for the first time in the field of biofiltration . Hence, three identical biofiltration units have been operated at the laboratory scale . During the experiments, nitrogen (as urea) was supplied at various concentrations to each reactor, via irrigated nutrient solutions . A comparative analysis of the results showed that the biodegradability scale followed the degree of substitution around the aromatic ring: toluene > xylene > trimethylbenzene, with 95, 80, and 70% maximum conversions, respectively . In addition, and despite the different removal levels achieved in the three bioreactors, it was established that from a reaction viewpoint, the degradation of the three compounds seemed to follow similar metabolic pathways involving methylcatechol isomers . Finally, by varying the nitrogen input concentrations in the three reactors, three degradation regimes have been highlighted: an N-limitation regime and an N-optimum regime, common to the three solvents, and an N-excess regime, favorable to the colonization of the filter beds by nitrifying species, which particularly affected the xylene and trimethylbenzene biodegradation.

J Microbiol Methods, 2003 Apr, 53(1), 87 - 95
Use of polyclonal antibodies to detect and quantify the NOR protein of nitrite oxidizers in complex environments; Maron PA et al.; In the approaches or models which aim to understand and/or predict how the functioning of ecosystems may be affected by perturbations or disturbances, little attention is generally given to microorganisms . Even when they are taken into account as indicators, variables which are poorly informative about the changes in the microbial functioning (microbial biomass or diversity or total number of microorganisms) are often used . To be able to estimate, in complex environments, the quantity of enzymes involved in key ecosystem processes may constitute a useful complementary tool . Here, we describe an immunological method for detecting and quantifying, in complex environments, the nitrite oxidoreductase (NOR), responsible for the oxidation of nitrite to nitrate . The alpha-catalytic subunit of the enzyme was purified from Nitrobacter hamburgensis and used for the production of polyclonal antibodies . These antibodies were used to detect and quantify the NOR by a chemifluorescence technique on Western blots after separation of total proteins from pure cultures and soil samples . They recognized the alpha-NOR of all the Nitrobacter species described to date, but no reaction was observed with members of other nitrite-oxidizing genera . The detection threshold and reproducibility of the proposed method were evaluated . The feasibility of its use to quantify NOR in a soil was tested.

J Environ Sci (China), 2003 Jan, 15(1), 25 - 30
Optimum operation conditions of nitrogen and phosphorus removal by a biofilm-activated-sludge system; Liu JX et al.; In the biofilm and activated sludge combined system, denitrifying bacteria attached on the fibrous carriers in the anoxic tank, while the sludge containing nitrifying and phosphorus removal bacteria was only recirculated between the aerobic and anaerobic tanks . Therefore, the factors affected and restricted nitrification, denitrification and phosphorus removal in a traditional A/A/O process were resolved . This paper describes the optimum operation conditions for nitrogen and phosphorus removal using this system.

Water Res, 2003 Apr, 37(7), 1655 - 61
Use of multidimensional scaling in the selection of wastewater toxicity test battery components; Ren S et al.; In aquatic toxicity testing, no single test species is sensitive to all toxicants . Therefore, test batteries consisting of several individual assays are becoming more common . The organisms in a test battery should be representative of the entire system of interest . The results of the assays should be complementary to other components in the test battery to avoid redundancy . With the aid of multidimensional scaling (MDS), a multivariate statistical method, we examined the toxicity data of five bioassays (the continuous Shk1, Polytox, activated sludge respiration inhibition, Nitrosomonas, and Tetrahymena assays) that could serve as test battery components for the assessment of wastewater toxicity to activated sludge . MDS mapped the five assays into a two-dimensional space and showed that the Nitrosomonas assay should be included in test batteries plus one of the remaining four assays for assessing wastewater toxicity to activated sludge .

Water Res, 2003 Apr, 37(7), 1571 - 82
A critical comparison of respirometric biodegradation tests based on OECD 301 and related test methods; Reuschenbach P et al.; Biodegradation studies of organic compounds in the aquatic environment gain important information for the final fate of chemicals in the environment . A decisive role play tests for ready biodegradability (OECD 301) and in this context, the respirometric test (OECD 301F) . Two different respirometric systems (Oxitop and Sapromat) were compared and in two of ten cases (diethylene glycol and 2-ethylhexylacrylate) differences were observed indicating that the test systems are not always equivalent . For 2-ethylhexylacrylate and cyclohexanone we could not state differences in the extent of biodegradation with a municipal and industrial inoculum whereas for cyclohexanone the degradation rate was faster with a municipal inoculum . Allylthiourea (ATU) proved to be an effective inhibitor of nitrification processes and did not affect the heterotrophic biodegradation activity . Modelling of biodegradation processes could be successfully performed with a first-order and a modified logistic plot .

Water Res, 2003 Mar, 37(6), 1385 - 93
Removal of bis(2-ethylhexyl) phthalate at a sewage treatment plant; Marttinen SK et al.; Bis(2-ethylhexyl) phthalate (DEHP) concentrations were measured at different stages in a full-scale sewage treatment plant (STP) and mass balances were calculated . The DEHP load to treatment process coming from the sewer system and the internal load comprising returned supernatants and filtrate from sludge treatment and excess secondary sludge were at the same level . The DEHP removal efficiency from the water phase at the STP was on average 94% of sewage DEHP, the main removal process being sorption to primary and secondary sludges . On average 29% of DEHP was calculated to be removed in the biological nitrifying-denitrifying activated sludge process, which was much less than expected from laboratory biodegradation studies described in literature . Monoethylhexyl phthalate, the primary biotransformation product of DEHP, was not detected at any treatment stage . Approximately 32% of DEHP in sewage was removed during anaerobic digestion of the sludge, while 32% remained in the digested and dewatered sludge.

Water Res, 2003 Mar, 37(6), 1371 - 7
Nitrification with high nitrite accumulation for the treatment of wastewater with high ammonia concentration; Ruiz G et al.; The objective of this paper was to determine the best conditions for partial nitrification with nitrite accumulation of simulated industrial wastewater with high ammonia concentration, lowering the total oxygen needed in the nitrification step, which may mean great saving in aeration . Dissolved oxygen (DO) concentration and pH were selected as operational parameters to study the possibility of nitrite accumulation not affecting overall ammonia removal . A 2.5L activated sludge reactor was operated in nitrification mode, feeding a synthetic wastewater simulating an industrial wastewater with high ammonia concentration . During the start-up a pH of 7.85 and a DO of 5.5mg/L were used . The reactor was operated until stable operation was achieved at final nitrogen loading rate (NLR) of 3.3kgN- NH(4)(+)/m(3)d with an influent ammonia concentration of 610mg N-NH(4)(+)/L.The influence of pH was studied in continuous operation in the range of 6.15-9.05, changing the reactor pH in steps until ammonia accumulation (complete nitrification inhibition) took place . The influence of DO was studied in the same mode, changing the DO in steps from 5.5 to 0.5mg/L.The pH was not a useful operational parameter in order to accumulate nitrite, because in the range of pH 6.45-8.95 complete nitrification to nitrate occurs . At pH lower than 6.45 and higher than 8.95 complete inhibition of nitrification takes place . Setting DO concentration in the reactor at 0.7mg/L, it was possible to accumulate more than 65% of the loaded ammonia nitrogen as nitrite with a 98% ammonia conversion . Below 0.5mg/L of DO ammonia was accumulated and over a DO of 1.7mg/L complete nitrification to nitrate was achieved.In conclusion, it is possible under the conditions of this study, to treat high ammonia synthetic wastewater achieving an accumulation of at least 65% of the loaded nitrogen as nitrite, operating at a DO around 0.7mg/L . This represents a reduction close to 20% in the oxygen necessary, and therefore a considerable saving in aeration.

FEMS Microbiol Lett, 2003 Jan 28, 218(2), 339 - 44
CANON and Anammox in a gas-lift reactor; Sliekers AO et al.; Anoxic ammonium oxidation (Anammox) and Completely Autotrophic Nitrogen removal Over Nitrite (CANON) are new and promising microbial processes to remove ammonia from wastewaters characterized by a low content of organic materials . These two processes were investigated on their feasibility and performance in a gas-lift reactor . The Anammox as well as the CANON process could be maintained easily in a gas-lift reactor, and very high N-conversion rates were achieved . An N-removal rate of 8.9 kg N (m(3) reactor)(-1) day(-1) was achieved for the Anammox process in a gas-lift reactor . N-removal rates of up to 1.5 kg N (m(3) reactor)(-1) day(-1) were achieved when the CANON process was operated . This removal rate was 20 times higher compared to the removal rates achieved in the laboratory previously . Fluorescence in situ hybridization showed that the biomass consisted of bacteria reacting to NEU, a 16S rRNA targeted probe specific for halotolerant and halophilic Nitrosomonads, and of bacteria reacting to Amx820, specific for planctomycetes capable of Anammox.

J Am Chem Soc, 2003 Feb 19, 125(7), 1738 - 47
Spectroscopic characterization and assignment of reduction potentials in the tetraheme cytochrome C554 from Nitrosomonas europaea; Upadhyay AK et al.; The tetraheme cytochrome c(554) (cyt c(554)) from Nitrosomonas europaea is an essential electron transfer component in the biological oxidation of ammonia . The protein contains one 5-coordinate heme and three bis-His coordinated hemes in a 3D arrangement common to a newly characterized class of multiheme proteins . The ligand binding, electrochemical properties, and heme-heme interactions are investigated with Mossbauer and X- and Q-band (parallel/perpendicular mode) EPR spectroscopy . The results indicate that the 5-coordinate heme will not bind the common heme ligands, CN(-), F(-), CO, and NO in a wide pH range . Thus, cyt c(554) functions only in electron transfer . Analysis of a series of electrochemically poised and chemically reduced samples allows assignment of reduction potentials for heme 1 through 4 of +47, +47, -147, and -276 mV, respectively . The spectroscopic results indicate that the hemes are weakly exchange-coupled (J approximately -0.5 cm(-)(1)) in two separate pairs and in accordance with the structure: hemes 2/4 (high-spin/low-spin), hemes 1/3 (low-spin/low-spin) . There is no evidence of exchange coupling between the pairs . A comparison of the reduction potentials between homologous hemes of cyt c(554) and other members of this new class of multiheme proteins is discussed . Heme 1 has a unique axial N(delta)-His coordination which contributes to a higher potential relative to the homologous hemes of hydroxylamine oxidoreductase (HAO) and the split-Soret cytochrome . Heme 2 is 300 mV more positive than heme 4 of HAO, which is attributed to hydroxide coordination to heme 4 of HAO.

Water Sci Technol, 2003, 47(1), 219 - 27
Tertiary nitrification in a new dual-medium aerated filter; Ishikawa S et al.; In an effort to develop an aerated filter with high nitrification capabilities, we formulated a new filter with 2 layers: the upper layer is filled with a plastic medium, and the lower with anthracite . We tested the filter in a pilot-scale apparatus on secondary-treated sewage, and in a small-scale apparatus on secondary-treated sewage and on artificial sewage . We evaluated the nitrification characteristics under various conditions of water velocity, air velocity, temperature, and pH . We designed a tertiary plant to treat 20,000 m3/day of secondary-treated sewage, using the new filter or a conventional filter . From these comparisons, it appeared that the dual-medium aerated filter had high nitrification capabilities and was an effective device for tertiary sewage treatment.

Water Sci Technol, 2003, 47(1), 139 - 44
Performance and membrane fouling in a pilot scale SBR process coupled with membrane; Shin H et al.; The performance of the pilot-scale submerged membrane coupled with sequencing batch reactor (SM-SBR) for upgrading effluent quality was investigated in this study . The reactor was operated with 3-hour cycle with alternating anoxic and aerobic conditions to treat organics, nitrogen and phosphate . Despite various influent characteristics, COD removal was always higher than 95% . Sufficient nitrification was obtained within a few weeks after start-up and during the stable period, complete nitrification occurred despite short aeration time . Total nitrogen (TN) removal efficiency was reached up to 85% . Membrane flux was critical for TN removal so that the decrease of flux by membrane fouling led to increase of HRT, and it caused the endogenous respiration of microorganisms such as nitrifying bacteria . The stirred cell test revealed the significant role of the soluble fraction in membrane permeability and dissolved solids played a major role in the short-term fouling mechanism . The cake resistance by the soluble COD fraction of supernatant or soluble microbial products (SMP) was investigated as a major part of total resistance.

Water Sci Technol, 2003, 47(1), 97 - 104
Nitrifying microbial community analysis of nitrite accumulating biofilm reactor by fluorescence in situ hybridization; Han DW et al.; Biological nitrogen removal via nitrite pathway in wastewater treatment is very important especially in the cost of aeration and as an electron donor for denitrification . Wastewater nitrification and nitrite accumulations were carried out in a biofllm reactor . The biofilm reactor showed almost complete nitrification and most of the oxidized ammonium was present as nitrite at the ammonium load of 1.2 kg N/m3/d . Nitrite accumulation was achieved by the selective inhibition of nitrite oxidizers by free ammonia and oxygen limitation . Nitrite oxidation activity was recovered as soon as the inhibition factor was removed . Fluorescence in situ hybridization studies of the nitrite accumulating biofilm system have shown that genus Nitrosomonas which is specifically hybridized with probe NSM156 was the dominant nitrifying bacteria while Nitrospira was less abundant than those of normal nitrification systems . Further FISH analysis showed that the combinations of Nitrosomonas and Nitrospira cells were identified as important populations of nitrifying bacteria in an autotrophic nitrifying biofilm system.

Water Sci Technol, 2003, 47(1), 71 - 6
Nitrogen removal using a vertically moving biofilm system; Rodgers M et al.; The aim of this laboratory study was to establish the efficacy of a new experimental biofilm system for the removal of nitrogen from synthetic wastewater . The system consisted of six reactors in series: one anaerobic, one anoxic and four aerobic reactors . In both the anaerobic and anoxic reactors, a plastic cuboid module was repeatedly moved up and down in the wastewater, while being totally submerged at all times . In each of the aerobic reactors, an identical module to that used in the anaerobic and anoxic reactors was intermittently and repeatedly immersed in and lifted out of the wastewater . All the individual reactors had a bulk fluid volume of 28.2 litres and the average temperature of the wastewater was about 10 degrees C . Each module consisted of crossflow corrugated plastic sheets with a surface area of 1.824 m2 . The nitrate recycle flow from the fourth aerobic tank to the anoxic tank was twice the inflow to that tank . In the anoxic reactor, filtered COD was removed at an average rate of 2.22 kg COD/m3 x d and nitrate-nitrogen was denitrified at a rate of 0.42 kg NO3-N/m3 x d . The average nitrification rate in the second aerobic reactor was 0.12 kg NH4-N/m3 x d . The new biofilm system was simple to construct and operate.

Water Sci Technol, 2003, 47(1), 49 - 57
Effect of dissolved oxygen concentration on the biofilm and in situ analysis by fluorescence in situ hybridization (FISH) and microelectrodes; Jang A et al.; A better understanding of microbiology and ecology of nitrifying bacteria in inner biofilms is an important part of improving process performance and control . Microelectrodes and fluorescent in situ hybridization (FISH) in biofilm research have been used to investigate the spatial distributions of various microbial activities in biofilms and have led to new experimental findings as well as modifications of the homogeneous assumptions in the biofilm kinetic models . The objective of this study is to try the combination of two methods, both FISH and microelectrode measurements, and to provide reliable and in situ information on nitrifying bacterial activity in biofilms . The characteristics of biofilm developed on tygon slides were different according to the change of dissolved oxygen (DO) . When the DO increased from 2 to 10 mg DO/L, the rate of the biofilm thickness increased and its dry density changed from 50-70 to 25-90 mg/cm3 . Ammonia oxidizing bacteria were not uniformly distributed in biofilm, and were found at the deeper layer where oxygen is depleted, they were detected primarily in the upper and middle layers of the biofilm.

Bioresour Technol, 2003 Jun, 88(2), 107 - 13
Nitrogen removal from wastewater using a double-biofilm reactor with a continuous-flow method; Hsieh YL et al.; Wastewater microorganisms of nitrification and denitrification were cultivated to compose two biofilm modules, termed the permeable support bioreactor (PSB) and the membrane feeding substrate bioreactor (MFSB) . PSB and MFSB were combined in a single tank to develop a double-biofilm reactor, which was used to treat nitrogen contaminants in wastewater . With a membrane supplement of substrates (O(2) and CH(3)OH), the D.O . and COD levels were at a low value in the bulk solution thus inhibitive effects between nitrification and denitrification were minimized . Simultaneous nitrification/denitrification was conducted in the reactor and the double-biofilm reactor achieved high nitrification and denitrification efficiency, of 96.5% and 82%, respectively.

Biotechnol Bioeng, 2003 Apr 5, 82(1), 28 - 37
Theory of pH-stat titration; Ficara E et al.; Innovative techniques are being studied to assess the activity of bioreactors and to improve the performance and operational stability of biological processes . Among these techniques, the pH-stat titration is applicable to any bioreaction involving pH variations . Up to now, the main application of the pH-stat titration has been for nitrification monitoring . In this article, we present a theoretical model of pH-stat titration, which predicts the response to any reaction involving the production or consumption of protons, hydroxyl ions, or inorganic carbon chemical species (CO(2), HCO(3)(-), CO(3)(=)) . This model is a useful tool to understand pH-stat titrations, to define their applicability and limits, and to select the best experimental conditions for specific applications . Tests have been performed to compare experimental pH-stat titration rates in the presence of carbon dioxide and HCO(3)(-) producing reactions to the values predicted by the model and a very satisfying correspondence was found .

Environ Sci Technol, 2003 Jan 15, 37(2), 343 - 51
Real-time PCR quantification of nitrifying bacteria in a municipal wastewater treatment plant; Harms G et al.; Real-time PCR assays using TaqMan or Molecular Beacon probes were developed and optimized for the quantification of total bacteria, the nitrite-oxidizing bacteria Nitrospira, and Nitrosomonas oligotropha-like ammonia oxidizing bacteria (AOB) in mixed liquor suspended solids (MLSS) from a municipal wastewater treatment plant (WWTP) using a single-sludge nitrification process . The targets for the real-time PCR assays were the 16S rRNA genes (16S rDNA) for bacteria and Nitrospira spp . and the amoA gene for N . oligotropha . A previously reported assay for AOB 16S rDNA was also tested for its application to activated sludge . The Nitrospira 16S rDNA, AOB 16S rDNA, and N . oligotropha-like amoA assays were log-linear over 6 orders of magnitude and the bacterial 16S rDNA real-time PCR assay was log-linear over 4 orders of magnitude with DNA standards . When these real-time PCR assays were applied to DNA extracted from MLSS, dilution of the DNA extracts was necessary to prevent PCR inhibition . The optimal DNA dilution range was broad for the bacterial 16S rDNA (1000-fold) and Nitrospira 16S rDNA assays (2500-fold) but narrow for the AOB 16S rDNA assay (10-fold) and N . oligotropha-like amoA real-time PCR assay (5-fold) . In twelve MLSS samples collected over one year, mean cell per L values were 4.3 +/- 2.0 x 10(11) for bacteria, 3.7 +/- 3.2 x 10(10) for Nitrospira, 1.2 +/- 0.9 x 10(10) for all AOB, and 7.5 +/- 6.0 x 10(9) for N . oligotropha-like AOB . The percent of the nitrifying population was 1.7% N . oligotropha-like AOB based on the N . oligotropha amoA assay, 2.9% total AOB based on the AOB 16S rDNA assay, and 8.6% nitrite-oxidizing bacteria based on the Nitrospira 16S rDNA assay . Ammonia-oxidizing bacteria in the wastewater treatment plant were estimated to oxidize 7.7 +/- 6.8 fmol/hr/cell based on the AOB 16S rDNA assay and 12.4 +/- 7.3 fmol/hr/cell based on the N . oligotropha amoA assay.

Ying Yong Sheng Tai Xue Bao, 2002 Sep, 13(9), 1099 - 103
{Response of N transformation related soil enzyme activities to inhibitor applications}; Chen L et al.; With an aerobic incubation test, this paper studied the response of soil urease, nitrate reductase, nitrite reductase, and hydroxylamine reductase to urease inhibitor hydroquinone (HQ) applied in combination with nitrification inhibitor encapsulated calcium carbide (HQ + ECC) or dicyandiamide (HQ + DCD) . The results showed that HQ + DCD could inhibit urease activity and increase activities of nitrate reductase, nitrite reductase, and hydroxylamine reductase significantly in comparison with CK, HQ and HQ + ECC . Under the condition of our test, there existed a significant relationship between soil urease, nitrate reductase, nitrite reductase, and hydroxylamine reductase activities and soil NH4+ and NO3- contents, NH3 volatilization and N2O emission rate, and regression analysis indicated that there were significantly positive relationships between soil urease, nitrite reductase and hydroxylamine reductase activities.

Water Res, 2003 Mar, 37(5), 1100 - 10
The role of inorganic carbon limitation in biological nitrogen removal of extremely ammonia concentrated wastewater; Wett B et al.; It is clear from the fundamental biochemical processes that nitrification of extremely concentrated ammonia loads requires-among others-(1) sufficient alkalinity to buffer acidification and (2) bicarbonate as the substrate for the autotrophic biomass . However, at low pH values the aeration process causes CO(2) stripping and consequently a decrease of the available inorganic carbon . In order to analyse such complex interactions, we suggest in this paper an enhanced version of the widely acknowledged IWA (formerly IAWQ) activated sludge models . These model enlargements comprise an ion-balance for the calculation of the pH value and of dissociation species, a balance of inorganic carbon and a more detailed description of the relevant N-elimination processes and their inhibitions . The model was successfully employed to optimise a treatment strategy for rejection-water and landfill leachate (500-2000 mg ammonia-Nl(-1), COD/N ratio of 0.25-4) . Detailed data from two full-scale rejection-water treatment plants were used for systems identification, model calibration and validation . The results suggest that inhibition and limitation by nitrous acid (HNO(2)) and unionised ammonia (NH(3)) have often been overestimated . In this investigation the bicarbonate concentration proved to be crucial for the process . The optimisation of the bicarbonate concentration in the reactor could improve the nitrozation rate up to 100mg NH(4)(+)-Nl(-1)h(-1).

Waste Manag Res, 2002 Dec, 20(6), 529 - 35
Molecular characterisation of bacteria in a wetland used to remove ammoniacal-N from landfill leachate; Walsh KA et al.; Bacteria associated with leachate from a constructed, surface-flow wetland effective at removing ammonium-N, were characterised using molecular methods which bypass the need for cultivation . DNA was extracted from the sample and bacterial 16S rDNA sequences amplified and cloned . Ninety-six individual clones were re-amplified and analysed by restriction digestion and targeted sequencing . A collector's curve was used to estimate the total number of bacterial groups (operational taxonomic units, OTUs) in the sample at 47 . Thirty-six clones representing 28 OTUs were sequenced and characterised by aligning them against published sequences . Of these, 10 were confidently identified, whilst for the remaining 18, the closest match was obtained . The sequences in 64% of the OTUs were similar to those of the Proteobacteria but no classical nitrifying bacteria were identified . However, alkaliphilic Methylomicrobium sp . that oxidise ammonium and bacteria from the genus Alcaligenes, at least one species of which is capable of heterotrophic nitrification, were detected.

Ecotoxicol Environ Saf, 2003 Jan, 54(1), 56 - 64
Effects of different plant protection programs on soil microbes; Ahtiainen JH et al.; The aim of this study was to assess the effects of two pesticide regimens (conventional full insurance compared with supervised and reduced pesticide use) and two cultivation techniques (conventional tillage and fertilization compared with no tillage and lower fertilization) on soil microbes in a field study, and to evaluate the results with laboratory tests . The herbicides used were chlorsulfuron, MCPA, and bentazone; the fungicides carboxin-imazalin and propiconazole; and the insecticides dimethoate and pirimicarb . In the field studies, the effects on microbial biota were assessed by measuring biomass (ATP content) and microbial activities related to carbon and nitrogen metabolism (soil respiration, nitrification potential) . Potential harmful effects of commercial formulations of the same pesticides on microbes were studied in the laboratory with two bacterial toxicity tests (Pseudomonas putida growth inhibition and Vibrio fischeri luminescence inhibition tests) and with a soil respiration inhibition test . Bioavailability of the pesticides in the soil was assessed by a solid-phase modification of the luminescent bacteria test . In the field studies the microbial activities and biomass followed the weather conditions during the growing season, and significant effects of pesticide treatments on microbial processes were not observed . In the laboratory studies the toxicity of certain pesticides was clearly detected by bacterial toxicity tests . However, in the soil respiration inhibition assessment with soil similar to that used in the field trial, inhibition was observed only at unrealistically high concentrations . This could be due to the limited bioavailability of the pesticides in soil of high clay and organic carbon content .

Water Environ Res, 2002 Nov-Dec, 74(6), 531 - 40
Modeling of nitrification inhibition with aniline in suspended-growth processes; Khin T et al.; Nitrification inhibition due to aniline was investigated in completely mixed suspended-growth, batch, and continuous processes . Synthetic wastewater was used with aniline as the carbon source . The experiments were conducted at aniline concentrations inhibitory to nitrifier organisms . In the batch tests, degradation took place rapidly (within 4 to 6 hours) for initial aniline concentrations below 100 mg/L, with nitrification picking up as soon as the aniline concentration decreased to less than 3 to 4 mg/L . For initial aniline concentrations of 250 mg/L and higher, complete nitrification did not take place even though the aniline concentration decreased to less than 3 to 4 mg/L . This observation indicated nitrifier inhibition due to aniline . In the continuous experiments, a hydraulic residence time of 8 to 24 hours and a solids retention time of 8 to 24 days were maintained . Complete nitrification took place at bulk aniline concentrations less than 0.5 mg/L, while at higher aniline concentrations, nitrification inhibition took place . The inhibitory effect of aniline on the nitrification process was modeled using uncompetitive inhibition kinetics . Modeling of batch processes yielded the value for the inhibition constant for aniline, Ki, as 3.3 mg/L . Modeling of continuous processes yielded criteria for stable process operation for nitrification under inhibitory conditions, which were also confirmed through experimental results.

J Air Waste Manag Assoc, 2002 Dec, 52(12), 1389 - 98
Long-term operation of a biofilter for simultaneous removal of H2S and NH3; Kim H et al.; Simultaneous removal of NH3 and H2S was investigated using two types of biofilters--one packed with wood chips and the other with granular activated carbon (GAC) . Experimental tests and measurements included analyses of removal efficiency (RE), metabolic products, and results of long-term operation (around 240 days) . The REs for NH3 and H2S were 92 and 99.9%, respectively, before deactivation . After deactivation, the RE for NH3 and H2S were decreased to 30-50% and 75%, respectively . The activity of nitrifying bacteria was inhibited by high concentrations of H2S (over 200 ppm) but recovered gradually after H2S addition was ceased . However, the Thiobacillus thioparus as sulfur oxidizing bacteria did not show inhibition at the NH3 concentration under 150-ppm conditions . The deactivation of the biofilter was caused by metabolic products {elemental sulfur and (NH4)2SO4} accumulating on the packing materials during the extended operation . The removal capacities for NH3 and H2S were 6.0-8.0 and 45-75 mg N, S/L/hr, respectively.

J Agric Food Chem, 2003 Jan 29, 51(3), 673 - 9
Accelerated degradation of methyl iodide by agrochemicals; Zheng W et al.; The fumigant methyl iodide (MeI, iodomethane) is considered a promising alternative to methyl bromide (MeBr) for soil-borne pest control in high-cash-value crops . However, the high vapor pressure of MeI results in emissions of a significant proportion of the applied mass into the ambient air, and this may lead to pollution of the environment . Integrating the application of certain agrochemicals with soil fumigation provides a novel approach to reduce excessive fumigant emissions . This study investigated the potential for several agrochemicals that are commonly used in farming operations, including fertilizers and nitrification inhibitors, to transform MeI in aqueous solution . The pseudo-first-order hydrolysis half-life (t(1/2)) of MeI was approximately 108 d, while the transformation of MeI in aqueous solutions containing selected agrochemicals was more rapid, with t(1/2) < 100 d (t(1/2) < 0.5 d in some solutions containing nitrification inhibitors) . The influence of these agrochemicals on the rate of MeI degradation in soil was also determined . Adsorption to soil apparently reduced the availability of some nitrification inhibitors in the soil aqueous phase and lowered the degradation rate in soil . In contrast, addition of the nitrification inhibitors thiourea and allylthiourea to soil significantly accelerated the degradation of MeI, possibly due to soil surface catalysis . The t(1/2) of MeI was <20 h in thiourea- and allylthiourea-amended soil, considerably less than that in unamended soil (t(1/2) > 300 h).

Huan Jing Ke Xue, 2002 Sep, 23(5), 62 - 6
{Nitrification of high concentration NH4(+)-N in membrane bioreactor}; Li H et al.; Nitrification performance of a membrane bioreactor was investigated under high concentration of NH4(+)-N . The removal rate of NH4(+)-N was over 99% under the condition of influent NH4(+)-N of 2000 mg/L and volumetric loading rate of NH4(+)-N 2.0 kg/(m3.d) . The specific nitrification rate was kept to be 0.36/d in a period of half year.

Adv Space Res, 2002, 30(4), 803 - 8
Aquatic animal research in space station and its issues--focus on support technology on nitrate toxicity; Shimura R et al.; We studied the effects of accumulated nitrate in water on the spawning, hatching and development of medaka using a simple nitrifying filter and a combined filter having both nitrifying and denitrifying capabilities . A nitrate concentration of 100 mg NO3(-)-N/L was clearly of lethal toxicity to fish when they were exposed to nitrate in both adult and the growing phases . A nitrate concentration of 75 mg NO3(-)-N/L reduced the fertilization rate, delayed the hatching time and reduced the hatching rate of the eggs laid by adults and decreased the growth rate of juveniles . In addition, nitrate accumulations as low as 50 mg NO3(-)-N/L remarkably retarded spawning and lowered the number of eggs laid by fish exposed in the juvenile phase . The effects on the reproduction system may be initiated by a low concentration, approximately 30 mg NO3(-)-N/L . c2002 COSPAR . Published by Elsevier Science Ltd . All rights reserved.

Water Sci Technol, 2002, 46(11-12), 331 - 5
Toxicity assessment of 255 chemicals to pure cultured nitrifying bacteria using biosensor; Tanaka Y et al.; The bioassay has been attracting attention as a method of toxicity assessments of micropollutants in the environment . In this study, we report the characteristics (selectivity and sensitivity) of the nitrifying bacteria biosensor for 255 kinds of chemicals as a model of chemical contaminant in the environment and the results of evaluation of mixed samples of several substances . In the nitrifying bacteria respiration inhibition test using the biosensor, 56 chemicals were detected . It was found that this biosensor is especially sensitive to seven chemicals that have a thiocarbonyl functional group (>C=S), such as a thioamide group of thiocarbamate group . These chemicals are considered to specifically inhibit AMO by chelation of copper . The samples consisted of a mixture of seven types of anilines that inhibit respiration in the bacteria, a mixture of five types of chlorophenols, and a mixture of eight types of substances that contain thiocarbonyl groups were examined . All of the mixed samples inhibited the respiration of the nitrifying bacteria more than 10% by the inhibition rate, and observed a synergistic effects of the substances in the samples.

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