J Environ Qual, 2002 Sep-Oct, 31(5), 1502 - 8 Evaluation of leachate recirculation on nitrous oxide production in the Likang Landfill, China; Lee CM et al.; Landfill leachate recirculation is efficient in reducing the leachate quantity handled by a leachate treatment plant . However, after land application of leachate, nitrification and denitrification of the ammoniacal N becomes possible and the greenhouse gas nitrous oxide (N2O) is produced . Lack of information on the effects of leachate recirculation on N2O production led to a field study being conducted in the Likang Landfill (Guangzhou, China) where leachate recirculation had been practiced for 8 yr . Monthly productions and fluxes of N2O from leachate and soil were studied from June to November 2000 . Environmental and chemical factors regulating N2O production were also accessed . An impermeable top liner was not used at this site; municipal solid waste was simply covered by inert soil and compacted by bulldozers . A high N2O emission rate (113 mg m-2 h-1) was detected from a leachate pond purposely formed on topsoil within the landfill boundary after leachate irrigation . A high N2O level (1.09 micrograms L-1) was detected in a gas sample emitted from topsoil 1 m from the leachate pond . Nitrous oxide production from denitrification in leachate-contaminated soil was at least 20 times higher than that from nitrification based on laboratory incubation studies . The N2O levels emitted from leachate ponds were compared with figures reported for different ecosystems and showed that the results of the present study were 68.7 to 88.6 times higher . Leachate recirculation can be a cost-effective operation in reducing the volume of leachate to be treated in landfill . However, to reduce N2O flux, leachate should be applied to underground soil rather than being irrigated and allowed to flow on topsoil. Water Res, 2002 Sep, 36(15), 3803 - 11 Simultaneous assessment of nitrification and denitrification on freshwater epilithic biofilms by acetylene block method; Teissier S et al.; Acetylene (C2H2) inhibits key enzymes involved in nitrification (Ammonium monooxygenase) and denitrification (N2O reductases) . Thus an injection of C2H2 at mid time of a batch type incubation make it possible to assess denitrification by measurement of the N2O accumulation as well as nitrification, calculated from the variations of the ammonium flux . As estimated by the "acetylene block technique", denitrification is known to be only a measure of the denitrification rate supported by nitrate diffusing from the water column (Dw) . This paper presents a first application on river epilithic biofilms which proved that the simultaneous measurement of Dw and nitrification allows the estimation of the order of magnitude of total denitrification (Dt) when nitrification is detected in the tested sample . This approach appears to be an easy tool for determination of nitrification and denitrification in natural samples and as thus presents an alternative to isotopic 15N methods. Bioresour Technol, 2002 Dec, 85(3), 217 - 23 Carbon and nitrogen mineralization in soil amended with phenanthrene, anthracene and irradiated sewage sludge; Barajas-Aceves M et al.; Irradiation of sewage sludge reduces pathogens and can hydrolyze or destroy organic molecules . The effect of irradiation of sewage sludge on C and N dynamics in arable soil and possible interference with toxic organic compounds was investigated in soil microcosms using a clay soil . The soil was treated with phenanthrene and anthracene, with and without irradiated and non-irradiated sewage sludge amendment . All the treated soils were incubated for 182 days at 25 degrees C . The CO2 production and dynamics of inorganic N (NH4+, NO2- and NO3-) were monitored . Addition of sewage sludge (0.023 g g(-1) soil), anthracene or phenanthrene (10.0 microg g(-1) soil dissolved in methanol), and methanol (10 mg g(-1) soil) to soil had a significant effect on CO2 production compared to the control . However, there were no significant differences between soil treated with irradiated and non-irradiated sewage sludge . Irradiated sewage sludge increased the C and N mineralization of anthracene amended soils to a greater extend than in phenanthrene amended soils . Nitrification was inhibited for 28 days in soil treated with either methanol, anthracene and phenanthrene . Application of sewage sludge reduced such toxicity effects after 28 days incubation. Environ Technol, 2002 Sep, 23(9), 971 - 80 Reclamation of treated domestic wastewater using biological membrane assisted carbon filtration (BioMAC); Van Hege K et al.; Membrane processes are increasingly used as an advanced treatment technique for the reclamation of treated domestic wastewater . Despite their inherent advantages, fouling remains an operational problem, while the removal of dissolved organic components such as volatile organic compounds is negligible . In the present work, the addition of a partially non-submerged biological granular activated carbon filtration to a microfiltration lab-scale reactor was investigated . It was observed that the reactor could be operated under stable flux conditions although regular hydraulic backwashing was necessary . Preferential attached growth of nitrifiers on the activated carbon particles allowed for a complete and very stable nitrification, with permeate total ammonium nitrogen and nitrite levels below 0.2 mg l(-1) regardless of influent concentrations . Chemical oxygen demand of the permeate averaged 5.26 mg O2 l(-1) which is below the Environmental Protection Agency guideline for wastewater reuse . Using an electronic nose, elimination of volatile compounds was assessed . The combined process resulted in complete odour removal, with the permeate odour levels equaling the reference samples (tap water), even during periods of increased reactor load (shock load experiment) . A 4.2 log10 CFU and 3.7 log10 CFU removal were observed for total coliforms and E . coli, respectively. Water Sci Technol, 2002, 46(4-5), 59 - 65 Biological detoxification of tar-water; Jansen JC et al.; Gasification is an important option for the swift implementation of biomass combined heat and power processes in the Danish energy supply system . Tar-water produced by the gas-cleaning system of gasifiers may contain substances toxic to nitrifying bacteria . As the gasification plants are small and often located in the catchment area of small wastewater treatment plants, discharge of the tar-water may be critical for wastewater treatment plants operated with nitrogen removal . Tar-water from a full-scale updraft gasifier has been thoroughly examined with respect to inhibition of nitrification and the toxicity for nitrifying bacteria has been evaluated for the dominating constituents in the tar-water . Simple organic substances make up the dominating part of the organic matter but phenol and phenolic compounds are also present in significant concentrations . The identified substances are biologically degradable and it has been demonstrated that most of the organic matter together with the toxicity can be eliminated in an aerobic activated sludge process. Water Sci Technol, 2002, 46(4-5), 249 - 55 Enhancing biological phosphorus removal from municipal wastewater with partial simultaneous precipitation; Valve M et al.; Pilot-scale tests to enhance phosphorus removal with ferrous sulphate in a biological phosphorus and nitrogen removal process (modified UCT) for treating municipal wastewater were performed . The results indicated that Fe(II) competes with the BioP organisms and will inhibit the biological phosphorus removal process completely at doses exceeding 9 g m(-3) of Fe(II) . The goal of an effluent P level of 0.5 mg l(-1) can be attained with 5 g m(-3) of Fe(II) . A consistent effluent concentration of 0.3 mg l(-1) could not be achieved with this method . A centrifugation method to evaluate the dewatering properties of sludge was developed . Comparison of the settling and dewatering properties between activated sludge from the pilot plant and a full-scale simultaneous precipitation process indicated no consistent differences between them . The poor settling properties are due to the long sludge retention time needed by nitrification and not to the biological phosphorus removal process. Water Sci Technol, 2002, 46(4-5), 241 - 7 Investigation of nitrogen removal in a cascaded membrane bioreactor; Kubin K et al.; Two different plants in different scales were compared . The main characteristic of the plants is the division of the nitrification volume into separate chambers . To gain more information about the internal conversion processes, concentration profiles of COD, NO3-N and NH4-N along the pathway of the waste water were measured . Moreover, the effect of different plant configurations and different operation conditions involving the internal circulation streams on the biological conversion processes were studied . Except for some temporary operation problems, the treatment performance of the plants was very stable and on a high level . There was a high correspondence between the plants . Operation without internal recirculation leads to lower effluent concentrations of ammonium . Beside this, operation of several nitrification chambers instead of only one chamber results in lower ammonium effluent concentrations. Water Sci Technol, 2002, 46(4-5), 201 - 7 Comparison of aerobic and anoxic phosphorus uptake in NDBEPR systems (UCT and ENBNRAS); Vermande SM et al.; Two Nitrification-Denitrification Biological Excess Phosphorus Removal (NDBEPR) systems have been operated for 8.5 months in order to compare their Biological Excess Phosphorus Removal (BEPR) performance . One of these systems, i.e . the University of Cape Town (UCT) system, exhibits mainly aerobic P uptake while the External Nitrification Biological Nutrient Removal Activated Sludge (ENBNRAS) system is characterised by high anoxic P uptake . It was observed that when operating with predominantly aerobic P uptake, the UCT system released more P than the ENBNRAS system, even though it had a lower anaerobic mass fraction . However, when the influent TKN/COD was high, i.e . > 0.1, anoxic P uptake also occurred in the UCT system and P release dropped to lower levels than in the ENBNRAS . Accordingly, P uptake of the UCT system was 5 mg P/l influent higher than that of the ENBNRAS system, when it was predominantly aerobic, but 9 mg P/l influent lower when anoxic P uptake occurred . As a result, the UCT system achieved superior P removal when aerobic P uptake was predominant (23% higher), but when high influent TKN/COD promoted anoxic P uptake the P removal of the UCT system was poorer than that of the ENBNRAS system . This study clearly showed that anoxic P uptake is not beneficial to NDBEPR systems. Water Sci Technol, 2002, 46(4-5), 163 - 9 Simultaneous nitrification and denitrification in a single reactor using bio-electrochemical process; Watanabe T et al.; Feasibility of a bio-electrochemical process for simultaneous nitrification and denitrification in a single reactor was experimentally investigated . The reactor consisted of anodic and cathodic electrodes, on which nitrifying and denitrifying biofilms, respectively, were fixed . Effects of the applied electric current and DO concentration in the bulk solution were examined . The TN removal could be achieved through the occurrence of nitrification and denitrification in anodic and cathodic biofilms, respectively . Both nitrification and denitrification rates increased with an increase in the applied electric current . Even at low DO concentration in the bulk solution, nitrification proceeded at a high rate by utilizing oxygen generated on the anode . Denitrification rate remained relatively high at high DO concentration due to supplying hydrogen gas to the inner side of the cathodic biofilm . The higher TN removal rate tended to be obtained at lower DO concentration and higher current density . From these results, it was concluded that the bio-electrochemical process was applicable to simultaneous nitrification and denitrification due to stable formation of aerobic and anoxic regions in the single reactor. Water Sci Technol, 2002, 46(4-5), 157 - 62 Balancing of nitrogen conversion in deammonifying biofilms through batch tests and GC/MS; Gaul T et al.; Growth carriers from a technical deammonifying moving-bed WWTP were used in batch tests to determine possible N-conversion reactions under varying oxygen and substrate conditions . Deammonification, denitrification, and nitrification reactions could be proved using conventional analysis, combined with gas chromatography/mass spectrometry analysis to get additional information about 15N-isotope labelled gaseous end products of the different reactions . In this orientating study N2O could be observed in some cases up to 12% of the total gas production . N2O production came from incomplete denitrification processes under anoxic or oxygen-limiting conditions and in the absence of organic substrate, as if structural components of deammonifying biofilms play a crucial role for the portion of side-reactions, leading to undesirable gaseous end products. Water Sci Technol, 2002, 46(4-5), 149 - 56 Comparison of combined and separated biological aerated filter (BAF) performance for pre-denitrification/nitrification of municipal wastewater; Rother E et al.; The performance of two systems of semi-industrial up-flow biological aerated filters (BAF) with pre-denitrification followed by nitrification was studied and compared under various operating and loading conditions . The first system consisted of two separate reactors for the denitrification and the nitrification step, whereas in the second system the aerobic nitrification zone was packed on top of the anoxic denitrification zone in one reactor . The second system potentially offers substantial savings in investment costs and space requirements for a large scale treatment plant . Regarding the elimination of carbonaceous pollution and denitrification the systems did not show significant differences . However, nitrification in the combined system suffered from the mixing of different biocenosis by daily backwashing and was reduced to 50-70% of the separated system's performance . Factors such as oxygen concentration, raw water composition and loading rates affected both systems' nitrification rates in similar ways . Since it is impossible to optimise the nitrification and denitrification processes separately, the combined system should only be considered for large scale applications if space is very scarce and if a stable raw water composition can be expected . If strict limit values for nitrate have to be met in the effluent, a combination of pre- and post-denitrification is advantageous and advisable. Water Sci Technol, 2002, 46(4-5), 139 - 47 Exploiting online in-situ ammonium, nitrate and phosphate sensors in full-scale wastewater plant operation; Ingildsen P et al.; In-situ nutrient sensors are now a proven technology . Having ion membranes eliminates the need for ultrafiltration, and consequently the sensors can be located at suitable places in any of the reactors . This gives the potential for new control structures for the control of nitrification, denitrification, and phosphorus removal . In the paper some examples of such controllers are demonstrated as used in a full-scale wastewater treatment plant . A successful control implementation scheme at full-scale plants includes three steps: monitoring, experimenting and controlling . The benefit of implementing process control based on nutrient sensors is real: by implementing precipitation dosage control a savings of 41% compared to flow proportional dosage can be reached, while the savings compared to constant dosage is 73% . An increase in nitrate recirculation shows significant improvement in the nitrogen removal ability at very low cost . Reliable nutrient sensors are not the only prerequisite for a successful control system . The design of actuators, such as drives, compressors and valves, is often overlooked . Furthermore, the lower level controllers have to work properly before the more advanced controllers can work adequately . A collection of practical experience regarding such issues is given in this paper. Water Sci Technol, 2002, 46(4-5), 125 - 30 Nitrogen removal in a SBR using the OGAR process control system; Tomlins Z et al.; OGAR is an industrial process control system that utilises on-line redox measurements to control the aeration sequence in an activated sludge process . Compared to conventional process control systems that use dissolved oxygen, OGAR makes use of redox as a control parameter during both aerobic and anoxic conditions . This paper reports on its first application in a sequencing batch reactor . The principal aim of this project is to demonstrate the capability of OGAR to achieve concentrations of total nitrogen in the treated effluent of less than 10 mg/L, which are typically stipulated by Queensland's Environmental Protection Agency (EPA) . In this study the use of the control system resulted in the following SBR performance: consistent effluent total nitrogen less than 5.0 mg/L; ammonia concentration reduced from 31.6 mg/L to 0.32 mg/L, effluent nitrate 2.8 mg/L; DO setpoint 1.5 mg/L had 10% higher effluent total nitrogen compared to DO setpoint 4.0 mg/L and redox end-points for nitrification 400 mV, denitrification 150 mV. Water Sci Technol, 2002, 46(4-5), 1 - 6 Respirometry techniques and activated sludge models; Benes O et al.; This paper aims to explain results of respirometry experiments using Activated Sludge Model No . 1 . In cases of insufficient fit of ASM No . 1, further modifications to the model were carried out and the so-called "Enzymatic model" was developed . The best-fit method was used to determine the effect of the proposed modifications . Increased agreement was found between simulated data and respirometry results, particularly for repeated respirometric tests with acetate as the sole substrate . Additionally, the influence of different biomass pre-conditioning methods was examined . Results from repeated respirometric tests suggest that presence of residual products in an activated sludge sample before respiration testing may decrease the sample's activity and significantly affect results from respirometric tests . An innovative approach to recover original activity is suggested by washing activated sludge samples with tap water or "mineral medium" . As allylthiourea (ATU) was used in most experiments to suppress endogenous nitrification, its influence on kinetic parameters was reviewed . Respirometric tests confirmed that ATU addition has a significant effect on activity and respiration rate of activated sludge samples and could affect results of respirometric analyses. Appl Environ Microbiol, 2002 Oct, 68(10), 4751 - 7 Growth at low ammonium concentrations and starvation response as potential factors involved in niche differentiation among ammonia-oxidizing bacteria; Bollmann A et al.; In nature, ammonia-oxidizing bacteria have to compete with heterotrophic bacteria and plants for limiting amounts of ammonium . Previous laboratory experiments conducted with Nitrosomonas europaea suggested that ammonia-oxidizing bacteria are weak competitors for ammonium . To obtain a better insight into possible methods of niche differentiation among ammonia-oxidizing bacteria, we carried out a growth experiment at low ammonium concentrations with N . europaea and the ammonia oxidizer G5-7, a close relative of Nitrosomonas oligotropha belonging to Nitrosomonas cluster 6a, enriched from a freshwater sediment . Additionally, we compared the starvation behavior of the newly enriched ammonia oxidizer G5-7 to that of N . europaea . The growth experiment at low ammonium concentrations showed that strain G5-7 was able to outcompete N . europaea at growth-limiting substrate concentrations of about 10 micro M ammonium, suggesting better growth abilities of the ammonia oxidizer G5-7 at low ammonium concentrations . However, N . europaea displayed a more favorable starvation response . After 1 to 10 weeks of ammonium deprivation, N . europaea became almost immediately active after the addition of fresh ammonium and converted the added ammonium within 48 to 96 h . In contrast, the regeneration time of the ammonia oxidizer G5-7 increased with increasing starvation time . Taken together, these results provide insight into possible mechanisms of niche differentiation for the ammonia-oxidizing bacteria studied . The Nitrosomonas cluster 6a member, G5-7, is able to grow at ammonium concentrations at which the growth of N . europaea, belonging to Nitrosomonas cluster 7, has already ceased, providing an advantage in habitats with continuously low ammonium concentrations . On the other hand, the ability of N . europaea to become active again after longer periods of starvation for ammonium may allow better exploitation of irregular pulses of ammonium in the environment. Environ Sci Technol, 2002 Sep 1, 36(17), 3706 - 10 Fate and effect of zinc from tire debris in soil; Smolders E et al.; Tire debris contains significant quantities of zinc (Zn), and there is concern about the diffuse Zn contamination of soils from tire wear . An experiment was set up to quantify the fate and effect of Zn from tire debris in soil . Two different soils were mixed with the <100-microm fraction of car and truck tire debris (25 g kg(-1) soil) or zinc sulfate (ZnSO4) as a reference . Soils were transferred to soil columns with free drainage and placed outdoors for 11 months . Leachates of the tire debris amended soils did not contain significantly (P>0.05) more Zn than control soils except for a 3-fold increase in one soil amended with cartire debris . The increase in Zn leaching due to tire debris was only 3% of the corresponding increase in the ZnSO4 treatment at the same total Zn in soil . Tire debris application increased the soil nitrification potential, whereas ZnSO4 application, at corresponding or smaller total Zn concentration, decreased nitrification potential . An increase in soil pH was observed in all soils treated with tire debris and explains the increased nitrification potential . About 10-40% of the Zn from tire debris was isotopically exchangeable in soil sampled after 1 year weathering . It is concluded that a significant fraction of Zn is released from the rubber matrix within 1 year, but the parallel increase in soil pH limits the mobilization of Zn in soil. Plant Physiol, 1993 Jan, 101(1), 141 - 146 Contamination of Ammonium-Based Nutrient Solutions by Nitrifying Organisms and the Conversion of Ammonium to Nitrate; Padgett PE et al.; Conversion of ammonium to nitrate and contamination by nitrifying organisms are often assumed not to be significant in ammonium-based nutrient solutions . To assess this assumption, maize (Zea mays) and pea (Pisum sativum) were grown under greenhouse conditions in aeroponic, hydroponic, and sand-culture systems containing 2 mM ammonium chloride as the sole nitrogen source and evaluated for the activity of contaminating nitrifying organisms . In all three culture systems, root colonization by nitrifying organisms was detected within 5 d, and nitrate was detected in the nutrient solution within 10 d after seedling transfer . In sand culture, solution nitrate concentration reached 0.35 mM by the end of the 17-d experiment . Consistent with the microbial ammonium oxidation sequence, nitrite was detected earlier than nitrate and remained at lower levels throughout the experiment . Nitrate was found in significant quantities in root and shoot tissues from seedlings grown in ammonium-based nutrient solutions in all of the solution culture systems . Maize seedlings grown in an ammonium-based hydroponic system contained nitrate concentrations at 40% of that found in plants grown in nitrate-based solution . Determination of nitrate (or nitrite) levels in the nutrient solution was the weakest indicator of the activity of nitrifying organisms . A bioassay for the presence of nitrifying organisms in combination with tissue analysis for nitrate was a better indicator of microbial conversion of ammonium to nitrate in nutrient solution culture . The results have implications for the use of ammonium-based nutrient solutions to obtain plants suitable for research on induction of nitrate uptake and reduction or for research using solution culture to compare ammonium versus nitrate fertilization. Water Res, 2002 Aug, 36(14), 3489 - 96 Treatment of domestic wastewater using the nutrient film technique (NFT) to produce horticultural roses; Monnet F et al.; Removal of organic matter, nitrogen and phosphorus was investigated in a pilot based on the nutrient film technique system used for horticultural production . Rosebushes producing commercial roses were set on an inclined impermeable surface over which a thin film of domestic wastewater flowed directly through the root matrix . The roses produced with wastewater as nutrient solution were qualitatively and quantitatively similar to those produced traditionally and can be marketable . In the presence of the rosebushes, the lowering of chemical oxygen demand (COD), biological oxygen demand (BOD5) and suspended solids (SS) increased with their influent strengths in a linear fashion correlation . Whatever the pollutant load of the influent, within the range studied, the level of organic pollution required to allow the discharge of the effluent into water courses was reached after 24 h of treatment . At this time, the COD reached 39 +/- 13 mg L(-1), the BOD5 7 +/- 4 mg L(-1) and the SS 8 +/- 6 mg L(-1) . The removal percentages were 89, 95 and 94, respectively, whereas without plants they were 55, 33 and 53, respectively . The rosebushes had a beneficial effect on the removal of phosphorus from 20% to 23% greater in their presence than without . In presence of plants, the nitrate was the principal form of nitrogen from 48 h of treatment whereas without rosebushes, nitrite represent more than 20% of initial nitrogen whatever the treatment duration . The root matrix served not only as a filter for the organic matter, but also provided a microhabitat suitable for nitrifying bacteria and heterotrophic micro-organisms, which responded rapidly to the pollutant load. Water Res, 2001 Nov, 35(16), 3968 - 76 Biological nitrogen removal with enhanced phosphate uptake in a sequencing batch reactor using single sludge system; Lee DS et al.; Simultaneous biological phosphorus and nitrogen removal with enhanced anoxic phosphate uptake was investigated in an anaerobic-aerobic-anoxic-aerobic sequencing batch reactor ((AO)2 SBR) . Significant amounts of phosphorus-accumulation organisms (PAOs) capable of denitrification could be accumulated in a single sludge system coexisting with nitrifiers . The ratio of the anoxic phosphate uptake to the aerobic phosphate uptake capacity was increased from 11% to 64% by introducing an anoxic phase in an anaerobic aerobic SBR . The (AO)2 SBR system showed stable phosphorus and nitrogen removal performance . Average removal efficiencies of TOC, total nitrogen, and phosphorus were 92%, 88%, and 100%, respectively . It was found that nitrite (up to 10 mg NO2(-)-N/l) was not detrimental to the anoxic phosphate uptake and could serve as an electron acceptor like nitrate . In fact, the phosphate uptake rate was even faster in the presence of nitrite as an electron acceptor compared to the presence of nitrate . It was found that on-line sensor values of pH, ORP, and DO were somehow related with the dynamic behaviours of nutrient concentrations (NH4+, NO3-, and PO4(3-)) in the SBR . These on-line sensor values were used as real-time control parameters to adjust the duration of each operational phase in the (AO)2 SBR . The real-time controlled SBR exhibited better performance in the removal of phosphorus and nitrogen than the SBR with fixed-time operation. Water Res, 2001 Nov, 35(16), 3857 - 66 Nitrogen transformations in a wetland receiving lagoon effluent: sequential model and implications for water reuse; Gerke S et al.; Constructed wetlands could be components of low-tech systems to treat and reuse wastewater in arid region . A key function of the wetland would be to provide additional N removal . To improve design criteria, a sequential model of nitrogen transformations (organic N --> ammonium: ammonium --> nitrate: nitrate --> nitrogen gas) was successfully calibrated and verified for a wetland in Kingman, Arizona . A sequential model has the ability to "recognize" species of nitrogen in the influent and predict species of nitrogen in the effluent . Model scenarios show that increasing nitrification rates in the summer and denitrification rates in the winter would improve nitrogen removal efficiencies . Several lines of evidence suggest that wintertime denitrification may be limited by carbon supply . Winter carbon supply could be augmented by routing a portion of the water through channels planted with dryland vegetation. Water Sci Technol, 2002, 46(3), 73 - 80 Fate of pharmaceuticals during indirect potable reuse; Drewes JE et al.; The scope of this study was directed to examine different wastewater treatment technologies (activated sludge, trickling filter, nanofiltration, reverse osmosis) at full-scale facilities in Arizona and California leading to indirect potable reuse and their capability to remove pharmaceuticals . Additionally, the fate of selected pharmaceuticals was studied during soil-aquifer treatment (SAT) at sites where secondary and tertiary treated effluents are used for subsequent groundwater recharge . Facilities employing longer detention times during treatment (nitrifying and denitrifying plants) showed significant lower effluent concentration for analgesic drugs as compared to trickling filter or activated sludge facilities applying shorter detention times . A similar trend was observed for the lipid regulator gemfibrozil, which was significantly removed in denitrified effluents, whereas a trickling filter treated effluent exhibited concentration of 1,235 ng/L . Antiepileptic drugs, such as carbamazepine and primidone, showed no dependency on the wastewater treatment applied . None of the investigated drugs was detected in tertiary treated effluents after nanofiltration or reverse osmosis . After SAT, analgesic/anti-inflammatory drugs were efficiently removed after retention times of less than 6 months and remaining concentrations were near or below the detection limit of the analytical method . A high potential for biodegradation was also observed for anti-inflammatory drugs in groundwater recharge systems . The antiepileptics carbamazepine and primidone represented the most dominant of all investigated drugs in well treated domestic effluents (nitrifying/denitrifying plants) . Removal of carbamazepine and primidone did not seem to occur during travel times of more than 6 years in the subsurface. Water Sci Technol, 2002, 46(1-2), 543 - 50 The effect of C/N ratio on ammonia oxidising bacteria community structure in a laboratory nitrification-denitrification reactor; Ballinger SJ et al.; A laboratory scale reactor operated as a single sludge, denitrification-nitrification bioreactor (DNB), was fed a synthetic wastewater . The effect of the C/N ratio of the influent on the structure of beta-proteobacterial autotrophic ammonia-oxidizing bacterial (AOB) communities was determined by DGGE analysis of 16S rRNA gene fragments amplified using a range of AOB-selective primers . Fluorescence in situ hybridisation (FISH) was used to determine quantitative changes in the AOB communities . When operated at a C/N ratio of 2 the DNB was effective in nitrogen removal and nitrification was measured at approximately 1.0 mg NH4+-N/g dry wt/h . Altering the C/N ratio to 5 resulted in a 50% reduction in nitrification rates . Nitrification was restored to its original level when the C/N ratio was returned to 2 . AOB were detected by DGGE analysis of samples from the DNB under all operating conditions but the changes in C/N ratio and nitrification rates were accompanied by changes in the community structure of the AOB . However, quantitative FISH analysis indicated that beta-proteobacterial AOB were only present in high numbers (ca . 10(8) cells/ml) under the original operating conditions with a C/N ratio of 2 . Beta-proteobacterial AOB could not be detected by FISH when the C/N ratio was 5 . When nitrification activity was restored by returning the C/N ratio to 2, beta-proteobacterial AOB were still not detected and it is likely that either beta-proteobacterial AOB were not responsible for ammonia oxidation or that beta-proteobacterial AOB that did not contain the target sites for the range of 4 AOB selective probes used, were present in the reactor. Water Sci Technol, 2002, 46(1-2), 479 - 86 Two stage activated sludge plants--influence of different operational modes on sludge bulking and nitrification; Wandl G et al.; Conventional two stage activated sludge plants often lack sufficient nutrient removal performance due to substrate limitation for denitrification in the second stage . For the extension of the Vienna Main WWTP a two stage concept has been developed and tested by means of a pilot plant (scale 1:10.000) . The new concept enables the operation of two different modes: In BYPASS-mode a portion of the primary clarifier effluent is fed directly to the second stage; the HYBRID-mode includes the exchange of mixed liquor between the two stages; over the course of the pilot plant investigations it turned out that nutrient removal is strongly increased in comparison to conventional two stage mode, but the two modes of operation lead to different results with regard to the sludge quality and the nitrification performance . BYPASS mode yields a higher SVI in both stages and a lower nitrification performance in comparison to HYBRID mode . This is caused by the negative influence of the primary effluent on the biocoenosis of the second stage . Additionally, the reduced sludge loading of the first stage in this mode results in a higher sludge age which favours the growth of filaments (Microthrix and Nocardia) . In HYBRID-mode the higher load of the first stage results in a lower sludge age, fatty components are metabolized and incorporated in the sludge, thus, the growth of filaments is significantly reduced . Additionally, nitrification inhibiting substances are degraded in the first stage, which results in a higher nitrification performance in the second stage. Water Sci Technol, 2002, 46(1-2), 465 - 70 Go or no go for gel entrapped nitrifiers? A Belgian case study; Geenens D et al.; In the coming years, as stricter environmental requirements are imposed, many European Union wastewater treatment plants (WWTP) need to be expanded and/or upgraded . This requires considerable investments . Optimising the renovation recourses can lead to significant savings . The use of entrapped nitrifying bacteria for upgrading of WWTP towards nutrient removal may be benificial . Long term pilot tests were performed to evaluate a so-called pellet reactor . Differences in performance and microbiological composition of classical activated sludge and the pellet reactor were investigated . FISH analyses showed (i) absence of Nitrobacter cells and (ii) high abundance of Nitrospira in the pilot reactors . Two Belgian WWTP make use of fine bubble aeration and could--theoretically--easily be renovated towards nitrogen removal using encapsulated nitrifiers . Financial aspects are commented on. Water Sci Technol, 2002, 46(1-2), 439 - 42 Real-time monitoring of ammonia-oxidizing activity in a nitrifying biofilm by amoA mRNA analysis; Aoi Y et al.; Ammonia monooxygenase encoding mRNA (amoA mRNA) transcription in the wastewater treatment process was investigated using reverse transcription PCR (RT-PCR) as the model indicating specific function and activity in nitrifying processes . The dynamic response of amoA mRNA transcription and ammonia-oxidizing activity to the change of environmental conditions such as pH and concentration of ammonia was examined to determine the inductive factor and the inhibitor for amoA mRNA expression . Furthermore, we semiquantitatively investigated the response of amoA mRNA transcription to the pH fluctuation in a continuous fed nitrifying reactor . As a result, amoA mRNA oriented analysis enabled real-time assay of ammonia-oxidizing activity within 2 h as a response time . In contrast, rRNA and amoA encoding DNA were constantly detected at almost the same amount throughout the experiment . mRNA transcription was regulated by the many environmental conditions: ammonia seems to be one of the strong inducers for transcription of amoA mRNA, whereas low pH seems to be a strong inhibitor . These factors simultaneously affected the mRNA transcription and enzymatic activity leading to the complex phenomena of ammonia-oxidizing activity and amoA mRNA transcription in the continuous feeding reactors. Water Sci Technol, 2002, 46(1-2), 35 - 8 Oxidation-reduction potential (ORP) regulation of nutrient removal in activated sludge wastewater treatment plants; Li B et al.; Redox potential (ORP) regulation of nutrient removal in aeration tanks was tested for one year in three activated sludge wastewater treatment plants in Cincinnati, OH . The experiment results show a good relationship between ORP values and nutrient removal . Macro-biodegradation and sorption of substrate by activated sludge can significantly increase wastewater ORP, indicating the improvement of redox status of the bulk liquor . DO higher than 1.0 mg/L is necessary for good biodegradation and the improvement of liquid redox status . ORP values at higher temperatures (Twater = 20-26 degrees C) were lower than ORP values at lower temperatures (Twater = 14-19 degrees C), caused by the lower oxygen saturation capacity in wastewater and the more rapid oxygen consumption by microorganism under warmer conditions . Nitrification occurred at higher ORP values (380 mV) than did organic substrate oxidation (250 mV) . This verifies that different metabolic processes dominate in different ORP ranges . The pilot-scale experiment results demonstrate that the wastewater ORP values continued to increase throughout the whole 6-hour cycle when the influent COD was higher than 1,000 mg/L . For influent with low COD (40-120 mg/L), the wastewater ORP values did not increase in the second 3 hours of the cycle, during which time the microbial-biodegradation within the activated sludge floc dominated . High DO concentrations (6-8 mg/L) did not help improve the redox status . In fully-aerated wastewater, oxygen deeply penetrated into the activated sludge flocs, and microorganisms biodegraded the substrates within the flocs . Endogenous metabolism predominated. Water Sci Technol, 2002, 46(1-2), 319 - 22 A comparison of autotrophic ammonia-oxidizing bacteria in full- and laboratory-scale wastewater treatment reactors; Rowan AK et al.; Lab-scale reactors are commonly used to simulate full-scale plants as they permit the effects of defined experimental perturbations to be evaluated . Ideally, lab- and full-scale reactors should possess similar microbial populations . To determine this we compared the diversity of the beta-proteobacterial autotrophic ammonia-oxidising bacteria (AOB) in a full-scale and lab-scale biological aerated filter (BAF) using PCR with AOB selective primers combined with denaturing gradient gel electrophoresis (DGGE) . PCR amplified 16S rRNA gene fragments from the nitrification unit of the lab-and full-scale BAF were subjected to cloning and sequencing to determine the phylogenetic affiliation of the AOB . A high degree of comparability between the lab-and full-scale BAF was observed with respect to AOB populations . However minor differences were apparent . The importance of these minor constituents in the overall performance of the reactor is unknown . Nonetheless the lab-scale reactor in this study did appear to reflect the dominant AOB community within the full-scale equivalent. Water Sci Technol, 2002, 46(1-2), 305 - 12 Evaluation of autotrophic denitrification, heterotrophic nitrification, and PAOs in full scale simultaneous biological nutrient removal sysyems; Littleton HX et al.; Anoxic and aerobic batch reactor assays using a two-by-two factorial design were developed to determine the potential activity of autotrophic denitrification and heterotrophic nitrification in biological nutrient removal (BNR) activated sludge systems, especially those accomplishing simultaneous BNR (SBNR) . Results from the application of these assays to three full scale closed loop bioreactors previously documented to be accomplishing SBNR demonstrated that these activities were minimal in comparison with the conventionally recognized activities of heterotrophic denitrification and autotrophic nitrification . Activity within the mixed liquor consistent with current theories for phosphorus accumulating organisms (PAOs) was also observed . Along with other observations, this suggests the presence of PAOs in the facilities studied. Water Sci Technol, 2002, 46(1-2), 297 - 304 Differences in nitrification potential between fully aerobic and nitrogen removal activated sludge systems; Hatziconstantinou GJ et al.; Experimental observations made on two pilot plants, showed that nitrogen removal activated sludge systems, operating under favourable conditions, seem to develop increased nitrification potential compared to fully aerobic systems under similar conditions . This increased potential, which cannot be detected by simple nitrification performance evaluations, is attributed to higher autotrophic populations sustained--developed in similar systems employing anoxic reactors or phases . A reduced autotrophic decay rate under anoxic conditions as reported by some researchers, seems to play a significant role in such a response, most likely together with a more efficient use of available nitrogen for additional nitrifying microorganisms production, resulting from a reduced nitrogen loss to autotrophic biomass maintenance needs and heterotrophic biomass synthesis requirements. Water Sci Technol, 2002, 46(1-2), 289 - 95 Comparison of bench scale testing methods for nitrifier growth rate measurement; Katehis D et al.; The maximum specific nitrifier growth rate was determined for two wastewater treatment plants (WWTPs) using sequencing batch reactors (SBRs) and high F/M exponential growth batch tests . Higher nitrifier growth rates were obtained from the exponential growth batch tests . Operating SRT and aeration mode (fully aerobic versus anoxic/aerobic) significantly impacted the nitrifier's growth rate in the SBRs with lower SRT and anoxic/aerobic operation resulting in higher specific nitrifier growth rates. Water Sci Technol, 2002, 46(1-2), 281 - 8 Detection and quantification of expression of amoA by competitive reverse transcription-pCR; Ebie Y et al.; Ammonia oxidation by chemolithoautotrophic ammonia-oxidizing bacteria is an important step in the biological nitrogen removal process . The first conversion step, the oxidation of ammonia to hydroxylamine is catalyzed by ammonia monooxygenase (AMO) . To investigate the activity of ammonia oxidation, mRNA (designated as amoA) encoding a subunit of AMO was quantified by competitive reverse transcription (RT)-PCR . As a result, it was possible to detect and quantify amoA expression in cultured Nitrosomonas europaea and even complex microbial communities such as nitrifying bacterial aggregates by competitive RT-PCR . It was estimated that amoA concentration in cultured N . europaea was 2.3 x 10(8) copies x ml(-1) . Additionally, it was calculated that the copy number of amoA in nitrifying bacterial aggregates was 1.0 x 10(12) copies x ml(-1) (5.1 x 10(10) copies x mg(-1)-dry weight) . On the other hand, amoA expression in the natural activated sludge in a household Gappei-Johkaso was undetectable, whereas 16S rRNA of ammonia-oxidizing bacteria was detected by RT-PCR . Then, four days cultivation of this sludge in inorganic artificial wastewater resulted in increasing amoA expression to a quantifiable amount by competitive RT-PCR . In conclusion, the competitive RT-PCR was effective to investigate the expression of amoA as an indicator of ammonia oxidation activity by autotrophic ammonia-oxidizing bacteria. Water Sci Technol, 2002, 46(1-2), 273 - 80 Molecular analysis of ammonia-oxidizing bacterial populations in aerated-anoxic orbal processes; Park HD et al.; Aerated-anoxic processes operate under the principle that small additions of oxygen to an anoxic reactor induce simultaneous nitrification and denitrification . In these systems, ammonia oxidation in the anoxic zone can easily account for 30-50% of the total nitrification in the reactor, even though the dissolve oxygen concentration is usually below detection limit . To investigate whether the nitrification efficiency in aerated-anoxic processes was due to the presence of specialized ammonia-oxidizing bacteria (AOB), an analysis of the AOB population in an aerated-anoxic Orbal process and a conventional nitrogen removal process was carried out using phylogenetic analyses based on the ammonia monooxygenase A (amoA) gene . Terminal restriction fragment length polymorphism (TRFLP) analyses revealed that Nitrosospira-like organisms were one of the major contributors to ammonia oxidation in a full-scale aerated-anoxic Orbal reactor . However, the relative populations of Nitrosospira-like and Nitrosomonas-like AOB were not constant and appeared to have seasonal variability . Cloning and sequence comparison of amoA gene fragments demonstrated that most of the AOB in the aerated-anoxic Orbal process belonged to the Nitrosospira sp . and Nitrosomonas oligotropha lineages . The abundance of Nitrosospira-like organisms in aerated-anoxic reactors is significant, since this group of AOB has not been usually associated with nitrification in wastewater treatment plants. Water Sci Technol, 2002, 46(1-2), 267 - 72 The development and use of real-time PCR for the quantification of nitrifiers in activated sludge; Hall SJ et al.; Chemical analytical data has long been used to monitor the performance of activated sludge plants even though the process relies on the performance of microorganisms . It is now evident that a rapid and reliable quantitative method is required, to be able to monitor the organisms responsible for nutrient transformation and their activities, allowing avenues for more efficient nutrient removal . The development of real-time or quantitative polymerase chain reaction (PCR) also known as TaqMan or 5'-nuclease assay has allowed the rapid, quantitative analysis of DNA templates, eliminating some of the variability traditionally associated with other quantitative techniques . In this study analysis of Nitrospira spp., one of the key organisms in nitrite oxidation in wastewater treatment, was used to validate real-time PCR for the their quantification in activated sludge . A probe and primer set, targeting the 16S rRNA gene of Nitrospira spp . was designed according to the constraints of the TaqMan specifications . Samples used to evaluate the method included DNA from the sludge from full-scale wastewater treatment plants and laboratory scale systems . The reproducibility, quantitative efficiency and specificity were assessed in the evaluation . It was concluded that the method is sensitive and reproducible but has some constraints on the quantitative efficiency . A survey of full-scale systems for Nitrospira spp . was carried out and the results are presented here. Water Sci Technol, 2002, 46(1-2), 257 - 60 Population dynamics in an aerobic submerged fixed bed reactor (ASFBR) process; Lorda-de-los-Rios I et al.; In this study, an aerobic submerged fixed bed reactor's (ASFBR) population dynamics has been studied in order to know its behavior in different conditions of organic load and oxygen concentration . The reactor was fed with synthetic wastewater . Tested variables and applied values were: 1) Variations in organic load (OL): 16-65 g COD/m2/d . 2) Variations in influent's COD concentration: 40-400 g COD/m3 . 3) Variations in specific air flow (SAF): 15-127 m3air/kgCOD . Biofilm samples were taken at the top of the reactor . This study showed important variations in the composition and abundance of the microfauna depending on the experimental conditions . Variations in influent concentration had no significant effect on the abundance of the studied groups . However, differences depending on organic load and aeration conditions were observed . Organic load influenced every group studied but with different results . Sessile cilliates, metazoa and flagellates were abundant in low load, while crawling ones were in high load . Aeration intensity influenced most of the groups except Peranema and Vorticella spp . Despite obtaining good yields, not many protozoa, typical of biofilms under conventional processes, were found . Thus, a great variety of microorganisms, such as many classes of sessile and crawling cilliates, were not found . Important nitrifying activity was obtained at 20 cm depth in a bed . From this point, the heterotrophic and nitrifying populations exist but are inactive. Water Sci Technol, 2002, 46(1-2), 243 - 8 Ciliated protozoa and organic load at low temperatures in an aerated biofilter; Garcia-Santana C et al.; Ciliated protozoa have been widely used as water quality indicators because their main morphological characteristics are relatively simple to identify microscopically . The species and individual numbers in wastewater treatment systems are a consequence of the operational and environmental conditions of the process . The main objective of this research was to relate the effluent quality of a pilot aerated biofilter with the presence and relative abundance of ciliated protozoa when operated under different organic loading rates . The experimental work was done in a pilot aerated biofilter using 12 mm volcanic porous stones as filtering media and it was fed with municipal wastewater adjusting the experiments to 3 organic loading rates (3, 7, and 9 gCOD/m2 x d) . Temperature in the filter varied from 11 to 14 degrees C during the experimental work . COD and BOD removal rates do not change significantly with the different organic loads . Nitrification improves inversely to the organic load and it does not show dependence on the slight temperature changes observed . Eighteen species were identified as typical residents in wastewater systems . Free swimming species prefer higher organic loads . Crawling and attached species did not show significant changes with the organic load . According to the saprobity index of Pantle and Buck, the system, independently of the organic load, presented typical alpha-mesosaprobe level. Water Sci Technol, 2002, 46(1-2), 233 - 41 Structure and function of nitrifying biofilms as determined by molecular techniques and the use of microelectrodes; Okabe S et al.; The phylogenetic diversity of a nitrifying bacterial community of two types of nitrifying biofilms, a domestic wastewater biofilm and an autotrophic nitrifying biofilm grown on rotating disk reactors (RDR), was characterized by 16S ribosomal DNA (rDNA)-cloning analysis . Thereafter, successional development of nitrifying the bacterial community within both biofilms was visualized in situ by fluorescent in situ hybridization (FISH) wih a set of fluorescently labeled 16S rRNA-targeted DNA probes . In situ hybridization revealed that Nitrosomonas ureae was the numerically dominant species of the ammonia-oxidizing population in the domestic wastewater biofilm and that a population shift from N . urea to N . europaea and N . eutropha occurred when the culture medium was switched to the synthetic media from the domestic wastewater . After reaching the steady-state condition, microprofiles of NH4+, NO2-, NO3-, and O2 in the biofilms were measured by use of microsensors, and the spatial distributions of in situ nitrifying activities were determined . The relationship between the spatial organization of nitrifying bacterial populations and the in situ activity of these populations within the biofilms was discussed . Microelectrode measurements revealed that the active ammonia-oxidizing zone was vertically separated from the active nitrite-oxidizing zone . This vertical separation became more evident with increase of the substrate C/N ratio, leading to deterioration of nitrification efficiency . The combined use of these techniques made it possible to relate in situ nitrifying activity directly to the occurrence of nitrifying bacterial populations. Water Sci Technol, 2002, 46(1-2), 215 - 22 Production of gaseous nitrogen compounds in a novel process for ammonium removal; Green M et al.; The production of gaseous nitrogen compounds, particularly the greenhouse gas nitrous oxide, was investigated in a novel process for ammonium removal from wastewater . The process is based on the adsorption of ammonium on zeolite followed by bioregeneration . The zeolite serves the dual purpose of an ion exchanger and a physical carrier for nitrifying bacteria which bio-regenerate the ammonium saturated mineral . An analysis of the nitrifying population composition in the reactor fed with simulated secondary effluent (NH4+ = 50 mg/l) revealed that about half of the bacteria in the biofilm were common ammonium oxidizers Nitrosococcus mobilis and Nitrosomonas, while the other half were nitrite oxidizers . The amount of nitrogen losses, under different conditions, and the identification of the emitted gases (N2 or N2O) were investigated in two sets of experiments: (I) batch experiments using biomass originating from the ion exchange reactor with and without the addition of nitrite, and (II) continuous experiments using the ion exchange reactor with zeolite as the biomass carrier . In the batch experiments, nitrite and oxygen concentrations were determined as the major parameters responsible for the formation of gaseous nitrogen gas during ammonia oxidation by autotrophic bacteria . Continuous experiments showed that the major parameter significantly affecting nitrogen losses was the amount of ammonium adsorbed by the zeolite during the ion exchange phase . The amount of ammonium adsorbed determines the ammonium concentration during the initial period of bioregeneration, which in turn directly influences oxygen demand and the resulting concentrations of oxygen and nitrite . It was concluded that the formation of nitrogen gas compounds in the ion exchange/bioregeneration process can be eliminated by adjusting the operational regime to have a shorter adsorption phase resulting in smaller amounts of ammonium adsorbed per cycle. Water Sci Technol, 2002, 46(1-2), 207 - 14 In situ identification of azo dye inhibition effects on nitrifying biofilms using microelectrodes; Li J et al.; In this study, the inhibitory effects of acid orange 7 (AO7), a common azo dye, on nitrification in biofilms were investigated in situ using microelectrodes . Biofilms were obtained from laboratory rotating drum biofilm reactor after the nitrification process reached a pseudo-steady state . Dissolved oxygen, pH, NH4+, NO3-, and redox potential microelectrodes, with tip diameters ranging from 3-15 microm, were used to monitor the spatial distribution and change of microbial activities within nitrifying biofilms . It was found that at lower concentration (1 mg/L), AO7 had only a slight impact on the NH4+-N concentration profiles . The ammonium consumption rate decreased as higher AO7 concentrations (15 mg/L and 25 mg/L) were exposed to the biofilms . A similar trend was observed for the NO3(-)-N microprofiles . The nitrate production rate decreased as the AO7 concentration in the bulk solution increased . The dissolved oxygen and pH microprofiles also showed oxygen and alkalinity utilization, but at lower rates throughout the biofilms when the nitrification process was inhibited . No significant redox potential differences were observed in the biofilms after AO7 was applied. Water Sci Technol, 2002, 46(1-2), 129 - 38 The significance of denitrifying polyphosphate accumulating organisms in biological nutrient removal activated sludge systems; Hu ZR et al.; In this paper the advantages and disadvantages of denitrifying PAOs (polyphosphate accumulating organisms) in conventional BNRAS (biological nutrient removal activated sludge) and external nitrification BNRAS (ENBNRAS) systems are evaluated, with experimental data exhibiting a range of anoxic P uptake from low (<10%) to very high (>60%) . The results indicate that the specific denitrification rate of the PAOs on internally stored PHB COD is about 1/5th of that of the "ordinary" heterotrophic organisms on SBCOD, and the PAOs contribute little (maximum 20%) to the denitrification in BNRAS systems even when the anoxic P uptake is high (60% of the total P uptake) . Considering the unpredictable nature of anoxic P uptake and the reduction in BEPR it causes compared with aerobic P uptake BEPR, it is concluded that anoxic P uptake does not add a significant advantage to the BNR system. Waste Manag, 2002, 22(6), 611 - 6 Wet oxidation: a pre-treatment procedure for sludge; Genc N et al.; Wet oxidation process is specially effective for wastes with a high organic matter which can not be removed by conventional treatment methods . The digested and raw activated sludges of PAKMAYA yeast factory are treated by wet oxidation process . The liquid-phase organic matter concentration {as total organic carbon (TOC)} was increased by 16.5% in 10 min during the wet oxidation in the presence of Cu as catalyst and H2O2 . Lenghtening the period of the wet oxidation, the TOC-concentration was increased by 66% in 120 min . The biodegradability of the sludge after wet oxidation process was also examined . A very little development in the biodegradability was observed, when wet oxidation was applied as pre-treatment to the digested sludge (5% decrease as TOC, in the presence of Cu catalyst and H2O2) . However, in the case of digestion of the raw sludge after the application of wet oxidation, the biodegradability increased significantly (approximately 75%, as TOC) . Moreover, wet oxidation improved the ability of settling of sludge solids, as well as enhancing the treatment efficiency . Finally, the volume of settled solids was decreased by 80% in the presence of Cu and H2O2 . NH3+-N, NO2(-)-N and NO3(-)-N concentrations in the supernatant decreased with the wet oxidation . pH value of the sludge increased from 6.6 to 7.8-8.0 . Since stable sludge was taken from the digester where the nitrification process was progressing, a decrease in the nitrite concentration, with an increase in nitrate was observed in the digestion continuing after the wet oxidation pre-treatment . However, in the raw activated sludge, there was a nitrite formation only in the non-pretreated sludge. J Environ Sci (China), 2002 Jul, 14(3), 413 - 7 Effects of butachlor on microbial enzyme activities in paddy soil; Min H et al.; This paper reports the influences of the herbicide butachlor (n-butoxymethl-chloro-2', 6'-diethylacetnilide) on microbial respiration, nitrogen fixation and nitrification, and on the activities of dehydrogenase and hydrogen peroxidase in paddy soil . The results showed that after application of butachlor with concentrations of 5.5 micrograms/g dried soil, 11.0 micrograms/g dried soil and 22.0 micrograms/g dried soil, the application of butachlor enhanced the activity of dehydrogenase at increasing concentrations . The soil dehydrogenase showed the highest activity on the 16th day after application of 22.0 micrograms/g dried soil of butachlor . The hydrogen peroxidase could be stimulated by butachlor . The soil respiration was depressed within a period from several days to more than 20 days, depending on concentrations of butachlor applied . Both the nitrogen fixation and nitrification were stimulated in the beginning but reduced greatly afterwards in paddy soil. Environ Technol, 2002 Aug, 23(8), 839 - 47 Biofiltration of ammonia gas with sponge cubes coated with mixtures of activated carbon and zeolite; Kim H et al.; Removal of ammonia gas was investigated using a biofilter system packed with small cubes of polyurethane sponge that were coated with a powder mixture of activated carbon and natural zeolite . Experimental tests and measurements include removal efficiency, pH, metabolic products of ammonia and kinetic analysis . A removal efficiency over 90% can be obtained with ammonia concentrations below 150 ppm and at contact times above 23 sec.The ammonia adsorbing power of the present biocarrier can protect the biofilter system from a high ammonia shock loading in the feed . The maximum removal rate, Vm, obtained from the kinetic analysis is 8.47 g N (kg carrier)(-1) day(-1) and the saturation constant Ks is 50.36 ppm . Nitrite is produced dominantly during the entire experiments . The cell number of nitrifying bacteria is 1.58 x 10( cell (g carrier)(-1) . The present synthetic bio-carrier is considered to be one of the best among bio-carriers that have been used for the biofiltration of ammonia. Arch Microbiol, 2002 Oct, 178(4), 250 - 5 Epub 2002 Jun 27. Molecular biology and biochemistry of ammonia oxidation by Nitrosomonas europaea; Arp DJ et al.; Nitrosomonas europaea uses only NH(3), CO(2) and mineral salts for growth and as such it is an obligate chemo-lithoautotroph . The oxidation of NH(3) is a two-step process catalyzed by ammonia monooxygenase (AMO) and hydroxylamine oxidoreductase (HAO) . AMO catalyzes the oxidation of NH(3) to NH(2)OH and HAO catalyzes the oxidation of NH(2)OH to NO(2)(-) . AMO is a membrane-bound enzyme composed of three subunits . HAO is located in the periplasm and is a homotrimer with each subunit containing eight c-type hemes . The electron flow from HAO is channeled through cytochrome c(554) to cytochrome c(m552), where it is partitioned for further utilization . Among the ammonia-oxidizing bacteria, the genes for AMO, these cytochromes, and HAO are present in up to three highly similar copies . Mutants with mutations in the copies of amoCAB and hao in N . europaea have been isolated . All of the amoCAB and hao gene copies are functional . N . europaea was selected by the United States Department of Energy for a whole-genome sequencing project . In this article, we review recent research on the molecular biology and biochemistry of NH(3) oxidation in nitrifiers. Water Sci Technol, 2002, 45(12), 89 - 96 Optimization of nitrogen removal from piggery waste by nitrite nitrification; Eum Y et al.; The piggery waste characteristics greatly vary with types of manure collections and the amount of water used . If solids are separated well, the waste strength will be greatly reduced resulting in lower TCOD/TKN ratio of 4 (average) . If solids are separated by a mechanical scraper, some solids will remain and the waste strength will be increased with a TCOD/TKN ratio of 7 . This study was conducted to find an optimum operating condition for nitrogen removal with these two ratios . Nitrite nitrification was targeted because it could be a short cut process for savings in oxygen for nitrification and carbon requirements for denitrification . The study results indicated that nitrogen loading rate and pH were the most important factors to be considered for stable nitrite nitrification . The applicable nitrogen loads were estimated to be 0.3 to 2.0 kgTKN/oxic m3/d for high TCOD/TKN ratio without pH control . With higher pH > 8, NO2N/NOxN ratios in oxic stages even with lower nitrogen loads were increased . The SBR with low TCOD/TKN ratio less than 4 required additional alkalinity . For a complete denitrification, the influent TCOD/TKN ratio must exceed 6 with oxic/total reactor volume ratio of 0.5 . Nitrite nitrification and denitrification could save about 35% in tank volume and 50% in carbon requirement, respectively . However, 9.5% oxygen saving could be expected during the operation with low TCOD/TKN ratio . The elevated temperature due to the heat released from COD removal also enhanced microbial activities for nitrification and denitrification as well as ammonia stripping . However, careful attention must be provided for the reactor temperature not to inhibit the nitrification process. Water Sci Technol, 2002, 45(12), 181 - 8 Effect of dissolved oxygen conditions on nitrogen removal in continuously fed intermittent-aeration process with two tanks; Hidaka T et al.; In this study, an intermittent aeration type activated sludge process that is fed continuously is evaluated for nitrogen and organic carbon for facilities in rural areas, which are characterized by small scale, low loading rate and automatic operation . Anoxic and aerobic conditions can be regulated alternatively by intermittent aeration for biological nitrogen removal . It is proved that an intermittent aeration cycle of 90 min, with aeration/anoxic mixing periods of 25-30 min/65-60 min in Tank 1, and 30-45 min/60-45 min in Tank 2, and a DO control set at 0.6-1 mg/L during the aeration period are required for satisfactory treatment performance . Under these conditions, a stable effluent water quality with BOD < or = 5 mg/L, CODMn < or = 8 mg/L, Nitrogen < or = 3 mgN/L, SS < or = 5 mg/L and transparency > or = 80 cm can be achieved . The solids retention time in aerobic condition was 10-25 d, which is sufficient for nitrification. Water Sci Technol, 2002, 45(10), 349 - 56 Autotrophic denitrification for combined hydrogen sulfide removal from biogas and post-denitrification; Kleerebezem R et al.; In this paper we describe an alternative flow-chart for full treatment of wastewaters rich in organic substrates, ammonia (or organic nitrogen), and sulfate, such as those generated in fish cannery industries . Biogas generated during anaerobic pretreatment of these wastewaters is rich in hydrogen sulfide that needs to be removed to enable application of the biogas . Nitrogen elimination is traditionally achieved by subsequent nitrification and denitrification of the effluent of the anaerobic reactor . Alternatively, the hydrogen sulfide in the biogas can be applied as an electron donor in an autotrophic post-denitrification step . In order to study whether sufficient hydrogen sulfide containing biogas for denitrification was produced in the anaerobic reactor, the biogas composition as a function of the anaerobic reactor-pH was estimated based on a typical wastewater composition and chemical equilibrium equations . It is demonstrated that typical sulfate and nitrogen concentrations in fish cannery wastewater are highly appropriate for application of autotrophic post-denitrification . A literature review furthermore suggested that the kinetic parameters for autotrophic denitrification by Thiobacillus denitrificans represent no bottleneck for its application . Initial experimental studies in fixed-film reactors were conducted with sodium sulfide and nitrate as an electron donor-acceptor couple . The results revealed that only moderate volumetric treatment capacities (< 1 g-NO3- N l(-1) day(-1)) could be achieved . Mass balances suggested that incomplete sulfide oxidation to elemental sulfur occurred, limiting biomass retention and the treatment capacity of the reactor . Future research should clarify the questions concerning product formation from sulfide oxidation. Environ Sci Technol, 2002 Aug 1, 36(15), 3439 - 45 Use of polymer mats in series for sequential reactive barrier remediation of ammonium-contaminated groundwater: laboratory column evaluation; Patterson BM et al.; Large-scale column experiments were undertaken to evaluate the potential of in situ polymer mats (installed in series) to be used as permeable reactive barriers for delivery of oxidants and reductants to induce sequential bioremediation of ammonium-contaminated groundwater (approximately 120mg L(-1) NH4+-N), without bioaugmentation . The strategy was for the first group of polymer mats to deliver oxygen to induce bacterial nitrification of the ammonium to nitrite/ nitrate as the groundwater moved past and for the second group of polymer mats to deliver hydrogen or ethanol, to induce bacterial denitrification of the nitrite/nitrate to produce nitrogen gas . Once purging of the first polymer mat commenced, ammonium concentrations decreased downgradient from the polymer mats . Nitrification rates increased and stabilized over the 6-month experiment, with stable nitrification half-lives in the range 0.07-0.25 days . Nitrification most likely occurred in a biologically active zone at the polymer wall/aqueous interface . With hydrogen delivery via the polymer mats, a denitrification half-life (nitrate plus nitrite removal) of 3.5 days was induced . Denitrification rates were significantly enhanced when ethanol was delivered via a polymer mat, with denitrification half-lives in the range of 0.12-0.34 days . Nitrification/ denitrification rates were maintained for groundwater flow rates up to 300 m yr(-1), suggesting oxygen and ethanol delivery rates via the polymer mats were sufficient not to limit nitrification or denitrification . In soil columns, the polymer mat delivery system provided an effective and reliable technique for delivery of oxygen and hydrogen or ethanol for sequential nitrification/denitrification of ammonium-contaminated groundwater . Scale-up of this concept to a field pilot-scale is currently underway. Lett Appl Microbiol, 2002, 35(3), 251 - 5 Detection of Proteobacteria from the rumen by PCR using methanotroph-specific primers; Mitsumori M et al.; AIMS: To detect Proteobacteria, including methanotrophs, from the rumen fluid and the bacteria inhabiting the rumen epithelium . METHODS AND RESULTS: Proteobacteria inhabiting the rumen were detected by PCR using methanotroph-specific primers . The detected Proteobacteria were divided into clusters A, B, and C in addition to one clone, which was distinct from the clusters and closely related to Nitrosomonas sp . The clusters A, B, and C were close to Succinivibrio dextrinosolvens, Enterobacter cloacae, and Actinobacillus minor, respectively . The clones obtained from the rumen fluid each belonged to cluster A or B . The clones obtained from the rumen epithelium belonged to cluster B or C or to Nitrosomonas sp . CONCLUSIONS: It has been assumed that the rumen fluid and the rumen epithelium host different populations of Proteobacteria . Moreover, detection of Nitrosomonas from the rumen epithelium would indicate the possibility that the bacterium oxidizes ammonia and methane on the rumen surface . SIGNIFICANCE AND IMPACT OF THE STUDY: These findings suggest that the rumen fluid and the epithelium support different microbial populations, which would play specific roles in rumen function . Future study should focus on the relationship between these communities and physiological functions in the rumen. Environ Monit Assess, 2002 Jul, 77(2), 163 - 78 Emission of nitrous oxide from rice-wheat systems of Indo-Gangetic plains of India; Pathak H et al.; Nitrous oxide (N2O) accounts for 5% of the total enhanced greenhouse effect and responsible for the destruction of the stratospheric ozone . The rice-wheat cropping system occupying 26 million ha of productive land in Asia could be a major source of N2O as most of the fertilizer N in this region is consumed by this system . Emission of N2O as influenced by application of urea, urea plus farm yard manure (FYM), and urea plus dicyandiamide (DCD), a nitrification inhibitor, was studied in rice-wheat systems of Indo-Gangetic plains of India . Total emission of N2O-N from the rice-wheat systems varied between 654 g ha(-1) in unfertilized plots and 1,570 g ha(-1) in urea fertilized plots . Application of FYM and DCD reduced emission of N2O-N in rice . The magnitude of reduction was higher with DCD . In wheat also N2O-N emission was reduced by DCD . FYM applied in rice had no residual effect on N2O-N emission in wheat . In rice intermittent wetting and drying condition of soil resulted in higher N2O-N emission than that of saturated soil condition . Treatments with 5 irrigations gave higher emissions in wheat than those with 3 irrigations . In rice-wheat system, typical of a farmer's field in Indo-Gangetic plains, where 240 kg N is generally applied through urea, N2O-N emission is 1,570 g ha(-1) (0.38% of applied N) and application of FYM and DCD reduced it to 1,415 and 1,096 g ha(-1), respectively. Microbiology, 2002 Aug, 148(Pt 8), 2331 - 42 Identification of active methylotroph populations in an acidic forest soil by stable-isotope probing; Radajewski S et al.; Stable-isotope probing (SIP) is a culture-independent technique that enables the isolation of DNA from micro-organisms that are actively involved in a specific metabolic process . In this study, SIP was used to characterize the active methylotroph populations in forest soil (pH 3.5) microcosms that were exposed to (13)CH(3)OH or (13)CH(4) . Distinct (13)C-labelled DNA ((13)C-DNA) fractions were resolved from total community DNA by CsCl density-gradient centrifugation . Analysis of 16S rDNA sequences amplified from the (13)C-DNA revealed that bacteria related to the genera Methylocella, Methylocapsa, Methylocystis and Rhodoblastus had assimilated the (13)C-labelled substrates, which suggested that moderately acidophilic methylotroph populations were active in the microcosms . Enrichments targeted towards the active proteobacterial CH(3)OH utilizers were successful, although none of these bacteria were isolated into pure culture . A parallel analysis of genes encoding the key enzymes methanol dehydrogenase and particulate methane monooxygenase reflected the 16S rDNA analysis, but unexpectedly revealed sequences related to the ammonia monooxygenase of ammonia-oxidizing bacteria (AOB) from the beta-subclass of the PROTEOBACTERIA: Analysis of AOB-selective 16S rDNA amplification products identified Nitrosomonas and Nitrosospira sequences in the (13)C-DNA fractions, suggesting certain AOB assimilated a significant proportion of (13)CO(2), possibly through a close physical and/or nutritional association with the active methylotrophs . Other sequences retrieved from the (13)C-DNA were related to the 16S rDNA sequences of members of the Acidobacterium division, the beta-Proteobacteria and the order Cytophagales, which implicated these bacteria in the assimilation of reduced one-carbon compounds or in the assimilation of the by-products of methylotrophic carbon metabolism . Results from the (13)CH(3)OH and (13)CH(4) SIP experiments thus provide a rational basis for further investigations into the ecology of methylotroph populations in situ. J Appl Microbiol, 2002, 93(3), 431 - 7 In situ characterization of nitrifiers in an activated sludge plant: detection of Nitrobacter Spp; Coskuner G et al.; AIMS: The purpose of this work was to investigate microbial ecology of nitrifiers at the genus level in a typical full-scale activated sludge plant . METHODS AND RESULTS: Grab samples of mixed liquor were collected from a plug-flow reactor receiving domestic wastewater . Fluorescent in situ hybridization technique (FISH) was used to characterize both ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in combination with Confocal Scanning Laser Microscope (CSLM) . Fluorescently labelled, 16S rRNA-targeted oligonucleotide probes were used in this study . Both Nitrosomonas and Nitrosospira genera as AOB and Nitrobacter and Nitrospira genera as NOB were sought with genus specific probes Nsm156, Nsv443 and NIT3 and NSR1156, respectively . CONCLUSIONS: It was shown that Nitrosospira genus was dominant in the activated sludge system studied, although Nitrosomonas is usually assumed to be the dominant genus . At the same time, Nitrobacter genus was detected in activated sludge samples . SIGNIFICANCE AND IMPACT OF THE STUDY: Previous studies based on laboratory scale pilot plants employing synthetic wastewater suggested that only Nitrospira are found in wastewater treatment plants . We have shown that Nitrobacter genus might also be present . We think that these kinds of studies may not give a valid indication of the microbial diversity of the real full-scale plants fed with domestic wastewater. Appl Microbiol Biotechnol, 2002 Aug, 59(4-5), 557 - 66 Epub 2002 Jul 03. Oxygen-limited autotrophic nitrification/denitrification by ammonia oxidisers enables upward motion towards more favourable conditions; Philips S et al.; The hypothesis is formulated that in case of oxygen limitation in the sediment, nitrifiers switch from nitrification to oxygen-limited autotrophic nitrification-denitrification (OLAND) in order to survive and maintain activity . During OLAND, ammonium is oxidised using nitrite as e-acceptor to form dinitrogen gas . As an additional advantage they benefit from the gaseous N(2) formed as a means of transport . In this way, the nitrifiers can move out of the sediment and rise through the water column towards more favourable conditions . At the surface, the bacteria could take up oxygen, and recommence nitrification . In order to test this hypothesis, nitrifying sediment with an overlaying water column was simulated in lab-scale columns . Nitrogen transformations and material transport through the water column were followed after addition of different forms of nitrogen under oxygen-limited conditions . (15)N-labelling experiments showed a large contribution of OLAND to the observed nitrogen deficits . Nitrifier enumerations, fluorescent in situ hybridisation and 16S rRNA gene analysis revealed increased populations of ammonia oxidising nitrifiers in the upper water layers . The results presented support the proposed hypothesis of transport using OLAND . Nitrifying activity in the sediment immediately recovered almost completely from prolonged oxygen-limited incubation when oxygen concentrations were increased. Appl Microbiol Biotechnol, 2002 Aug, 59(4-5), 535 - 9 Epub 2002 Jun 01. Biodegradation of monohalogenated alkanes by soil NH(3)-oxidizing bacteria; Duddleston KN et al.; Although cooxidative biodegradation of monohalogenated hydrocarbons has been well studied in the model NH(3)-oxidizing bacterium, Nitrosomonas europaea, virtually no information exists about cooxidation of these compounds by native populations of NH(3)-oxidizing bacteria . To address this subject, nitrifying activity was stimulated to 125-400 nmol NO(3)(-) produced g(-1) soil h(-1) by first incubating a Ca(OH)(2)-amended, silt loam soil (pH 7.0+/-0.2) at field capacity (270 g H(2)O kg(-1) soil) with 10 micro mol NH(4)(+) g(-1) soil for 14 days, followed by another 10 days of incubation in a shaken slurry (2:1 water:soil, v/w) with periodic pH adjustment and maintenance of 10 mM NH(4)(+) . These slurries actively degraded both methyl bromide (MeBr) and ethyl chloride (EtCl) at maximum rates of 20-30 nmol ml(-1) h(-1) that could be sustained for approximately 12 h . Although the MeBr degradation rates were linear for the first 10-12 h of incubation, they could not be sustained regardless of NH(4)(+) level and declined to zero over 20 h of incubation . The transformation capacity of the slurry enrichments (~1 micro mol MeBr ml(-1) soil slurry) was similar to the value measured previously in cell suspensions of N . europaea with similar NH(3)-oxidizing activity . Several MeBr-degrading characteristics of the nitrifying enrichments were found to be similar to those documented in the literature for MeBr-degrading methanotrophs and facultatively methylotrophic bacteria. Environ Technol, 2002 Jul, 23(7), 791 - 8 Use of natural zeolite to enhance nitrification in biofilter; Pak D et al.; To enhance nitrification, natural zeolite and activated carbon were tested as a media in a biofilter to treat wastewater containing relatively high concentrations of TKN . Using those media, the adsorption isotherms for ammonium ion were compared; the K values for natural zeolite and activated carbon were found to be 0.5117 and 0.0006, respectively . In comparison of the performance of the two media, two identical, lab-scale biofilters were then operated for 4 months . The effect of NH3-N loading rates on the performance was investigated . The results showed that higher NH3-N removal efficiency and faster nitrification were achieved in the biofilter with natural zeolite throughout the experimental period . Nitrosomonas and Nitrobacter, two principal nitrifiers, in biofilm grown on two different media were counted and compared . Nitrobacter which is the more fragile of the two principal nitrifiers was outgrown in the biofilm on natural zeolite media . The reason for this may be due to the ammonium ion exchanging capacity of natural zeolite which provided the favorable environment for Nitrobacter. Water Res, 2002 May, 36(10), 2555 - 60 Nitrification in saline wastewater with high ammonia concentration in an activated sludge unit; Campos JL et al.; A nitrifying activated sludge reactor fed with a high salinity medium was operated efficiently at ammonia loading rates between 1 and 4 g NH4+ -N l(-1) d(-1) . The system became completely inefficient at inlet salt concentrations higher than 525 mM due to the mixed inhibition effect of salts and ammonia . The final product was mainly nitrate although dissolved oxygen limitations caused sporadic ammonia and nitrite accumulations . Specific nitrifying activity decreased due to the saline effect . A set of activity tests showed that in the continuous reactor non-adapted biomass is rather more sensitive than biomass to the saline effect . Physical properties of biomass in the reactor (sludge volumetric index and zone settling velocity) were not affected by the saline concentration, a biomass concentration of 20 gVSS l(-1) was achieved. Water Res, 2002 May, 36(10), 2541 - 6 Influence of aeration and sludge retention time on ammonium oxidation to nitrite and nitrate; Pollice A et al.; Partial nitrification to nitrite was reported to be technically feasible and economically favourable, especially when wastewater with high ammonium concentrations or low C/N ratios are treated . Nitritation can be obtained by selectively inhibiting nitrite oxidizing microrganisms through appropriate regulation of the system's pH, temperature, and sludge retention time . In addition to already known methods, the work showed that aeration patterns may play a relevant role too . Nitrification tests were performed in two lab-scale reactors operated under continuous and intermittent aeration, respectively . In both plants, temperature was maintained at 32 degrees C and pH was regulated at 7.2 by providing external buffer capacity when needed . The results showed that partial nitrification to nitrite was steadily obtained under oxygen limitation, independent of the sludge age . Therefore, the aeration pattern is proposed as an alternative parameter to the sludge retention time for controlling ammonium oxidation to nitrite. Water Res, 2002 May, 36(10), 2475 - 82 Completely autotrophic nitrogen removal over nitrite in one single reactor; Sliekers AO et al.; The microbiology and the feasibility of a new, single-stage, reactor for completely autotrophic ammonia removal were investigated . The reactor was started anoxically after inoculation with biomass from a reactor performing anaerobic ammonia oxidation (Anammox) . Subsequently, oxygen was supplied to the reactor and a nitrifying population developed . Oxygen was kept as the limiting factor . The development of a nitrifying population was monitored by Fluorescence In Situ Hybridization and off-line activity measurements . These methods also showed that during steady state, anaerobic ammonium-oxidizing bacteria remained present and active . In the reactor, no aerobic nitrite-oxidizers were detected . The denitrifying potential of the biomass was below the detection limit . Ammonia was mainly converted to N2 (85%) and the remainder (15%) was recovered as NO3- . N2O production was negligible (less than 0.1%) . Addition of an external carbon source was not needed to realize the autotrophic denitrification to N2. Environ Toxicol Chem, 2002 Aug, 21(8), 1644 - 50 Soil microbial toxicity of eight polycyclic aromatic compounds: effects on nitrification, the genetic diversity of bacteria, and the total number of protozoans; Sverdrup LE et al.; Eight polycyclic aromatic compounds (PACs) were tested for their toxic effect on the soil nitrification process, bacterial genetic diversity, and the total number of protozoans (naked amoebae and heterotrophic flagellates) . After four weeks of exposure in a well-characterized agricultural soil, toxic effects were evaluated by comparison to uncontaminated control soils . All PACs affected the nitrification process, and the calculated no-observed-effect concentrations (NOECs) for nitrification were 79 mg/kg for pyrene, 24 mg/kg for fluoranthene, 26 mg/kg for phenanthrene, 72 mg/kg for fluorene, 23 mg/kg for carbazole, 22 mg/kg for dibenzothiophene, 75 mg/kg for dibenzofuran, and 1,100 mg/kg for acridine . For all substances but acridine, nitrification was the most sensitive of the three toxicity indicators evaluated . No effect of the tested substances on bacterial diversity was found, as measured by denaturant gradient gel electrophoresis . In general, only weak effects at very high concentrations were found for the protozoans . However, for acridine, protozoan numbers were reduced at lower concentrations than those that affected the nitrification process, that is, with a 5% reduction at 380 mg/kg . For effects on nitrification, toxicity (NOEC values) expressed as soil pore-water concentrations (log10(micromol/L)) showed a significant inverse relationship with lipophilicity (log octanol-water partition coefficient) of the substances (r2 = 0.69, p = 0.011, n = 8) . This finding could indicate that the toxicity of substances similar to those tested might be predicted by a quantitative structure-activity relationship with lipophilicity as the predictor variable. Huan Jing Ke Xue, 2002 May, 23(3), 29 - 35 {Distribution and role of denitrifying, nitrifying, nitrosation and ammonifying bacteria in east lake}; Liu D et al.; The most probable number (MPN) method was employed to determine the distribution and role of four nitrogen cycle bacteria, including ammonifying bacteria, denitrifying bacteria, nitrosobacteria and nitrobacteria, in East Lake, Wuhan . The results showed that the n(MPN) of nitrosobacteria in water was most in rainy season and least in dry season, while the number in common season between them . The n(MPN) of water nitrobacteria in rainy season was less than in the other two seasons . The n(MPN) of water ammonifying and denitrifying bacteria were most in common season, least in dry season . The n(MPN) of nitrosobacteria in sediment in rainy season was more than that in other seasons . The n(MPN) of sediment nitrobacteria was most in dry season while denitrifying bacteria was more in dry season than in other seasons . The n(MPN) of ammonifying bacteria had no difference among three seasons . Compared with water phase, the n(MPN) of nitrosobacteria in sediment phase was more in rainy and dry season (p < 0.01), while nitrobacteria's number was prevailing in water phase during common and rainy season while denitrifying bacteria's was prevailing only in common season(p < 0.01) . The ammonifying bacteria had no difference in water and sediment . The results demonstrated that the difference in distribution of four nitrogen cycle bacteria in two phase and three season played a significant role in nitrogen removal, which promoted ammoniation, nitrification, nitrosification and denitrification in lake . The study also found that the lg{n(MPN)} of denitrifying and ammonifying bacteria in water and sediment had significant correlation with the catching gas volume(p < 0.001) . Furthermore, different season had different gas volume (p < 0.01), which showed that ammoniation and denitrification could convert organic nitrogen and nitrate into gas nitrogen(NH3, N2O, N2) and also varied greatly with different season. Environ Sci Technol, 2002 Jul 15, 36(14), 3074 - 8 Effect of nickel and cadmium speciation on nitrification inhibition; Hu Z et al.; Heavy metals have been postulated to cause significant nitrification inhibition . Using biomass from a well-controlled continuously operated lab-scale nitrifying bioreactor, the effect of nickel and cadmium on ammonium and nitrite oxidation was quantified . The extent of inhibition was calculated from the kinetics of ammonium oxidation and nitrite oxidation, inferred from maximum specific oxygen uptake rates (SOUR) measured in batch respirometric assays . Nickel and cadmium inhibited ammonium oxidation but not nitrite oxidation up to total analytical concentrations of approximately 1.0 mM . Metal fractions (total and free ion) were correlated with the extent of ammonium oxidation inhibition in the presence of various metal complexing agents (EDTA, NTA, citrate, SO4(2-)) . Inhibition was not a function of the total analytical metal concentration but strongly correlated with free cation concentration, {Ni2+} or {Cd2+} . This relationship could be described by either an empirical noncompetitive inhibition model for {Ni2+} or a linear model in the case of {Cd2+} . Furthermore, the free Ni2+ or Cd2+ concentrations could be modulated by the addition of a strong chelating agent (e.g., EDTA), resulting in reduced deleterious effects . However, at elevated doses, EDTA itself impaired nitrification . In sum, predictions and mandatory strategies of nitrification inhibition by heavy metals should be based on free cation concentrations and not on total metal concentrations. J Air Waste Manag Assoc, 2002 Jul, 52(7), 796 - 804 Regeneration of a compost biofilter degrading high loads of ammonia by addition of gaseous methanol; Demeestere K et al.; The long-term stability of a biofilter loaded with waste gases containing NH3 concentrations larger than 100 ppmv was studied in a laboratory-scale compost reactor . At an empty bed residence time (tau) of 21 sec, elimination capacities of more than 300 g NH3/m3/day were obtained at elimination efficiencies up to 87% . Because of absorption and nitrification, almost 80% of the NH3-N eliminated from the waste gas could be recovered in the compost as NH4(+)-N or NO2-/NO3(-)-N . The high elimination capacities could be maintained as long as the NH4+/ NOX- concentration in the carrier material was less than 4 g NH4+/NOx(-)-N/kg wet compost . Above this critical value, osmotic effects inhibited the nitrifying activity, and the elimination capacity for NH3 decreased . To restore the biofilter performance, a carbon source (methanol) was added to reduce NH4+/NOx- accumulated in the compost . Results indicate that methylotrophic microorganisms did convert NH4+/NOx- into biomass, as long as the NO3- content in the compost was larger than 0.1 g NO3(-)-N/kg compost . Removal efficiencies of CH3OH of more than 90% were obtained at volumetric loads up to 11,000 g CH3OH/ m3/day . It is shown that addition of CH3OH is a suitable technique for regenerating the compost material from osmotic inhibition as a result of high NH3 loading . The biofilter was operated for 4 months with alternating load ing of NH3 and CH3OH. Bioresour Technol, 2002 Aug, 84(1), 39 - 47 Effects of soil amendment on gas depth profiles in soil monoliths using direct mass spectrometric measurement; Sheppard SK et al.; Land use and agricultural practices are known to influence the source and sink concentrations of various gases, including greenhouse gases (NOx CH4 and CO2) . in soils . With everincreasing production of domestic sewage sludge and the prohibition of disposal at sea, pressure on waste disposal increases . Anaerobically digested domestic sewage sludge and/or lime were applied to an upland . Scottish soil and their effects on gas depth profiles monitored as indicators of microbial processes of the soil ecosystem . The concentrations of various gases (Ar, O2 . CO2, CH4, N2, NOx) were measured simultaneously at each depth using membrane inlet mass spectrometry (MIMS) . This technique enables the direct measurement of multiple gas species throughout soil cores with minimal disturbance . Intact soil monoliths were collected from the sample site, following amendment, and maintained in a constant temperature, environmental growth chambers . Statistical analyses (one-way ANOVA and LSD tests) were conducted to identify the depths at which gas concentrations in amended cores were significantly different from those in control (un-amended) cores . Significant effects were observed on the concentration of CO2, CH4, NOx and N2 at certain depths . Average CH4 concentration was consistently higher (>1 microM) in the upper horizon following application of sludge and sludge and lime together . N2 and NOx concentrations were elevated in cores treated with lime by approximately 100 and 32 microM . respectively, in much of the upper horizon . CO2 concentration increased above control mean values, at certain depths, following application of either sludge or lime . Some explanation for the changes in soil gas concentration was provided by reference to the microorganism assemblages and the gases associated with biochemistry of nitrification, denitrification, methane oxidation and methanogenesis. J Microbiol Methods, 2002 Oct, 51(2), 227 - 39 Enumerating ammonia-oxidizing bacteria in environmental samples using competitive PCR; Bjerrum L et al.; Primers targeting part of the ammonia-monooxygenase gene (amoA) have been used to detect and characterize ammonia-oxidizing bacteria (AOB) in different environments . In this study, a quantitative polymerase chain reaction (PCR) technique using a competitive template for the amoA primer pair is described and evaluated . The method is based on addition of an internal standard to the PCR, a competitive template, which is amplified together with the template in the environmental sample . By adding different amounts of competitive template to the sample and observing the relative intensity of environmental amplificate and competitive amplificate, the number of amoA gene copies can be determined . Different tests were made to evaluate the competitive PCR method (cPCR) with respect to equal amplification efficiency of the two templates, degeneracy of the priming site and the importance of flanking regions surrounding the competitive template . Calibration curves made by addition of known amounts of Nitrosomonas europaea to soil samples revealed a detection limit for this technique of less than 1000 cells g(-1) soil and a linear response over a wide range of cell additions . Cloning and sequencing of amoA amplificates have confirmed the specificity of the primers, as we have not detected any false positives among the more than 200 clones investigated . The vertical distribution of ammonia-oxidizers in the upper cm of a waterlogged rice paddy soil was compared to nitrate and oxygen concentration profiles determined with microsensors and to net process rates derived from these profiles. Environ Technol, 2002 Jun, 23(6), 685 - 94 Treatment of antibiotics wastewater utilizing successive hydrolysis, denitrification and nitrification; Ma W et al.; A process consisting of anaerobic hydrolysis, denitrification, and oxidation/nitrification was proposed for simultaneous removal of carbon and nitrogen from terramycin crystallizing mother solution (TCMS), and its performance was investigated by treating diluted TCMS in a lab-scale continuous flow column system . Direct denitrification-nitrification of diluted TCMS produced a significant residual of nitrate and nitrite, which disappeared 44 days after startup of anaerobic hydrolysis column . The electron donors available to denitrification were increased by 6 times after diluted TCMS was treated in the hydrolysis column under an HRT of 2.5 h or longer . The reaction rates of organics decomposition, nitrification, and denitrification were also significantly increased due to reduction of terramycin and decomposition of complicated molecules to small molecules during anaerobic hydrolysis . The specific denitrification rate and nitrification rate increased from 0.033 d(-1) and 0.01 d(-1) to 0.045 d(-1) and 0.021 d(-1) respectively after diluted TCMS (dilution ratio: 1:4) was hydrolyzed in anaerobic hydrolysis column at a hydraulic retention time (HRT) of 4 h. Appl Microbiol Biotechnol, 2002 Jul, 59(2-3), 338 - 43 Epub 2002 May 01. Effects of nitrite and ammonium on methane-dependent denitrification; Waki M et al.; For effective application of methane-dependent denitrification (MDD) in the treatment of wastewater containing NO(2)(-) or NH(4)(+), the effect of these inorganic nitrogen compounds on MDD activity needs to be clarified . The MDD activity of sludge acclimatized with CH(4) and O(2) was determined with mineral media of different nitrogen-compound compositions in the presence of 0.21 atm CH(4) and 0.20 atm O(2) . Incubations with media containing only NO(2)(-) or two of the three inorganic nitrogen compounds (NO(3)(-)+NO(2)(-), NO(2)(-)+NH(4)(+) or NH(4)(+)+NO(3)(-)) resulted in MDD activity equal to or higher than that with media containing only NO(3)(-) . However, there was no MDD activity in media containing NO(2)(-) at 10 degrees C, probably because of serious inhibition of NO(2)(-) on methane oxidation . MDD occurred in media containing only NH(4)(+), although the total nitrogen removal efficiency was very low . These results show that NO(2)(-) and NH(4)(+), in the presence of NO(x)(-), do not inhibit but rather promote MDD . Consequently, NH(4)(+) does not need to be completely oxidized to NO(3)(-) in the nitrification reactor before MDD . However, under psychrophilic conditions, NO(2)(-) seriously inhibited MDD . Therefore, the nitrification reactor must not discharge effluent containing NO(2)(-) under psychrophilic conditions. Appl Microbiol Biotechnol, 2002 Jul, 59(2-3), 332 - 7 Epub 2002 Apr 16. Hydraulic selection pressure-induced nitrifying granulation in sequencing batch reactors; Tay JH et al.; The effect of hydraulic selection pressure on the development of nitrifying granules was investigated in four column-type sequencing batch reactors (SBR) . The nature of SBR is cycle operation, thus SBR cycle time can serve as a main hydraulic selection pressure imposed on the microbial community in the system . No nitrifying granulation was observed in the SBR operated at the longest cycle time of 24 h, due to a very weak hydraulic selection pressure, while the washout of nitrifying sludge was found in the SBR run at the shortest cycle time of 3 h, and led to a failure of nitrifying granulation . Excellent nitrifying granules with a mean diameter of 0.25 mm and specific gravity of 1.014 were developed in a SBR operated at cycle times of 6 h and 12 h, respectively . The results further showed that a short cycle time would stimulate microbial activity, production of cell polysaccharides and also improve the cell hydrophobicity . These hydraulic selection pressure-induced microbial changes favour the formation of nitrifying granules . This work, probably for the first time, shows that nitrifying granules can be developed at a proper hydraulic selection pressure in terms of SBR cycle time . Nitrifying granulation is a novel biotechnology which has a great potential for wastewater nitrification. Water Res, 2002 Apr, 36(8), 2147 - 51 The effect of CO2 concentration on a nitrifying chalk reactor; Green M et al.; The effect of CO2 concentration on nitrification rate was studied in a fluidized bed reactor using chalk (solid calcium carbonate) as the biomass carrier and buffering agent . Using one chalk type and uniform particle size, carbon dioxide was found to limit the nitrification rate in the reactor at concentrations up to 0.3 mmol l(-1) . At this concentration the nitrification rate was about 2.5-2.7g NH4+-Nl reactor(-1) d(-1) . The pH established in the reactor varied between 4.5 and 5.5, remarkably with lower pH obtained remarked at higher nitrification rates . Kinetic parameters for nitrification rate with CO2 as the rate limiting substrate were determined: a Michaelis-Menten constant, Km, of 0.013 mmol l(-1) CO2 and a maximum ammonium oxidation rate of 2.33g NH4+-Nl reactor(-1) d(-1). Environ Technol, 2002 May, 23(5), 497 - 514 Remediation of ammonia-rich minewater in constructed wetlands; Demin OA et al.; A three-year study of ammonia removal from minewater was carried out employing constructed wetland systems (surface flow wetland and subsurface flow wetland cells) at the former Woodey Mine in West Yorkshire, UK . The 1.4 Ha surface flow wetland (constructed in 1995) reduced the ammonia concentration from 3.5 - 45 mg l(-1) to < 2.3 mg l(-1) during the first half of the study and to essentially zero in the last year (2000 - 2001) . About 25% of contained ammonia was converted to nitrate, about 10% was consumed by the plants and up to 30% was converted to nitrogen gas . This maturation effect was attributed to increased depth of sludge from sedimentation of ochre, providing increased surface area for immobilisation of ammonia oxidising bacteria . The surface flow wetland finally removed 2.3 g m(-2) day(-1) ammonia in comparison with 3.8 g m(-2) day(-1) for the subsurface flow (pea gravel) wetland cells, constructed for the present work and dosed with ammonium salts . Removal of ammonia by both systems was consistent with well-established mechanisms of nitrification and denitrification . It was also consistent with ammonia removal in wastewater wetland systems, although the greater aeration in the minewater systems obviated the need for special aeration cycles . The general role of wetland plants in such aerated conditions was attributed to maintaining hydraulic conditions (such as hydraulic efficiency and hydraulic resistance of substratum in subsurface flow systems) in the wetlands and providing a suspended solids filter for minewater. Appl Environ Microbiol, 2002 Jul, 68(7), 3502 - 8 Solid-phase contact assay that uses a lux-marked Nitrosomonas europaea reporter strain to estimate toxicity of bioavailable linear alkylbenzene sulfonate in soil; Brandt KK et al.; Information about in situ toxicity of the bioavailable pools of adsorptive soil pollutants is a prerequisite for proper ecological risk assessment in contaminated soils . Such toxicity data may be obtained by assays allowing for direct exposure of introduced test microorganisms to the toxicants, as they appear in solid solution equilibria in the natural soil . We describe a novel sensitive solid-phase contact assay for in situ toxicity testing of soil pollutants based on a recombinant bioluminescent reporter strain of Nitrosomonas europaea . A slurry of the reporter strain and soil sample was shaken for 1 h, after which bioluminescence was measured either directly (soil slurry protocol) or in the supernatant obtained after centrifugation (soil extract protocol) . The assay was validated for both protocols by using linear alkylbenzene sulfonate (LAS) as a toxic and adsorptive model compound in the soil samples . Interestingly, LAS showed the same toxicity to the reporter strain with either soil incubation (both protocols) or pure culture, suggesting that adsorbed LAS pools contributed to the observed toxicity . The solid-phase contact assay that used the reporter strain of lux-marked N . europaea was slightly more sensitive for the detection of LAS toxicity in soil than activity-based assays targeting indigenous nitrifiers and much more sensitive than assays targeting indigenous heterotrophic microbes . We conclude that the new solid-phase contact assay, which is based on direct interaction of the test microorganisms with bioavailable pools of the toxicants in soil, provides a most sensitive and relevant method for evaluating the in situ toxicity and assessing the risks of soil contaminants. Appl Environ Microbiol, 2002 Jul, 68(7), 3449 - 54 tfdA-like genes in 2,4-dichlorophenoxyacetic acid-degrading bacteria belonging to the Bradyrhizobium-Agromonas-Nitrobacter-Afipia cluster in alpha-Proteobacteria; Itoh K et al.; The 2,4-dichlorophenoxyacetate (2,4-D)/alpha-ketoglutarate dioxygenase gene (tfdA) homolog designated tfdAalpha was cloned and characterized from 2,4-D-degrading bacterial strain RD5-C2 . This Japanese upland soil isolate belongs to the Bradyrhizobium-Agromonas-Nitrobacter-Afipia cluster in the alpha subdivision of the class Proteobacteria on the basis of its 16S ribosomal DNA sequence . Sequence analysis showed 56 to 60% identity of tfdAalpha to representative tfdA genes . A MalE-TfdAalpha fusion protein expressed in Escherichia coli exhibited about 10 times greater activity for phenoxyacetate than 2,4-D in an alpha-ketoglutarate- and Fe(II)-dependent reaction . The deduced amino acid sequence of TfdAalpha revealed a conserved His-X-Asp-X(146)-His-X(14)-Arg motif characteristic of the active site of group II alpha-ketoglutarate-dependent dioxygenases . The tfdAalpha genes were also detected in 2,4-D-degrading alpha-Proteobacteria previously isolated from pristine environments in Hawaii and in Saskatchewan, Canada (Y . Kamagata, R . R . Fulthorpe, K . Tamura, H . Takami, L . J . Forney, and J . M . Tiedje, Appl . Environ . Microbiol . 63:2266-2272, 1997) . These findings indicate that the tfdA genes in beta- and gamma-Proteobacteria and the tfdAalpha genes in alpha-Proteobacteria arose by divergent evolution from a common ancestor. Contemp Top Lab Anim Sci, 1999 May, 38(3), 80 - 83 High Mortality in Zebrafish (Danio rerio); Pullium JK et al.; A group of 100 adult zebrafish were housed in a new system at a stocking density of 20 fish per tank . Four weeks after arrival, 15 fish presented with petechial hemorrhages and ulceration on the surfaces of the skin . Samples of the fish were collected for histopathology, fungal culture, and bacterial culture and sensitivity . Water samples were analyzed for pH, ammonia, nitrite, and submitted for bacterial and fungal culture . Histologically, the epidermis had multiple areas of ulceration and mononuclear cell infiltrate . Gram-positive bacteria were observed beneath the surface of the skin and surrounding the outer aspect of the spinal cord . Both Aeromonas hydrophila and A . sobria were isolated from the affected fish, and a diagnosis of motile aeromonad septicemia (MAS) was made . Water from the tanks had a nitrite level of 1-5 ppm, a toxic concentration that indicated poor water quality . Because the housing system had been seeded with Nitrobacter spp . and Nitrosomonas spp . only 2 weeks prior to the arrival of the fish, a lack of colonizing nitrifying bacteria was deemed to be the cause of the high nitrite level, which, along with over-crowding, stressed the fish and increased their susceptibility to MAS . No further cases of septicemia were observed once the nitrite level and stocking density were reduced. Syst Appl Microbiol, 2002 Apr, 25(1), 84 - 99 The microbial community composition of a nitrifying-denitrifying activated sludge from an industrial sewage treatment plant analyzed by the full-cycle rRNA approach; Juretschko S et al.; The composition of the microbial community present in the nitrifying-denitrifying activated sludge of an industrial wastewater treatment plant connected to a rendering facility was investigated by the full-cycle rRNA approach . After DNA extraction using three different methods, 94 almost full-length 16S rRNA gene clones were retrieved and analyzed phylogenetically . 59% of the clones were affiliated with the Proteobacteria and clustered with the beta- (29 clones), alpha- (24), and delta-class (2 clones), respectively . 15 clones grouped within the green nonsulfur (GNS) bacteria and 11 clones belonged to the Planctomycetes . The Verrucomicrobia, Acidobacteria, Nitrospira, Bacteroidetes, Firmicutes and Actinobacteria were each represented by one to five clones . Interestingly, the highest 'species richness' {measured as number of operational taxonomic units (OTUs)} was found within the alpha-class of Proteobacteria, followed by the Planctomycetes, the beta-class of Proteobacteria, and the GNS-bacteria . The microbial community composition of the activated sludge was determined quantitatively by using 36 group-, subgroup-, and OTU-specific rRNA-targeted oligonucleotide probes for fluorescence in situ hybridization (FISH), confocal laser scanning microscopy and digital image analysis . 89% of all bacteria detectable by FISH with a bacterial probe set could be assigned to specific divisions . Consistent with the 16S rRNA gene library data, members of the beta-class of Proteobacteria dominated the microbial community and represented almost half of the biovolume of all bacteria detectable by FISH . W