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| 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 . Within the beta-class, 98% of the cells could be identified by the application of genus- or OTU-specific probes demonstrating a high in situ abundance of bacteria related to Zoogloea and Azoarcus sensu lato . Taken together, this study provides the first encompassing, high-resolution insight into the in situ composition of the microbial community present in a full-scale, industrial wastewater treatment plant. Chemosphere, 2002 Jun, 47(8), 845 - 50 Suppression of nitrification and N2O emission by karanjin--a nitrification inhibitor prepared from karanja (Pongamia glabra Vent.); Majumdar D; A laboratory incubation study was undertaken to study nitirification and N2O emission in an alluvial, sandy loam soil (typic ustochrept), fertilized with urea and urea combined with different levels of two nitrification inhibitors viz . karanjin and dicyandiamide (DCD) . Karanjin {a furanoflavonoid, obtained from karanja (Pongamia glabra Vent.) seeds} and DCD were incorporated at the rate of 5%, 10%, 15%, 20% and 25% of applied urea-N (100 mg kg(-1) soil), to the soil (100 g) adjusted to field capacity moisture content . Mean N2O flux was appreciably reduced on addition of the inhibitors with urea . Amounts of nitrified N (i.e . (NO3- + NO2-)-N) in total inorganic N (i.e . (NO3 + NO2- + NH4+)-N) in soil were found to be much lower on the addition of karanjin with urea (2-8%) as compared to urea plus DCD (14-66%) during incubation, indicating that karanjin was much more potent nitrification inhibitor than DCD . Nitrification inhibition was appreciable on the application of different levels of karanjin (62-75%) and DCD (9-42%) . Cumulative N2O-N loss was found to be in the range of 0.5-80% of the nitrified N at different stages of incubation . Application of karanjin resulted in higher mitigation of total N2O-N emission (92-96%) when compared with DCD (60-71%). ISA Trans, 2002 Apr, 41(2), 127 - 43 Software sensor for on-line estimation of the microbial activity in activated sludge systems; Sotomayor OA et al.; This paper considers the design of a software sensor (or soft-sensor) for the on-line estimation of the biological activities of a colony of aerobic micro-organisms acting on activated sludge processes, where the carbonaceous waste degradation and nitrification processes are taken into account . These bioactivities are intimately related to the dissolved oxygen concentration . Two factors that affect the dynamics of the dissolved oxygen are the respiration rate or the oxygen uptake rate (OUR) and the oxygen transfer function (K(l)a) . These items are challenging topics for the application of recursive identification due the nonlinear characteristic of the oxygen transfer function, and to the time-varying feature of the respiration rate . In this work, OUR and the oxygen transfer function are estimated through a software sensor, which is based on a modified version of the discrete extended Kalman filter . Numerical simulations are carried out in a predenitrifying activated sludge process benchmark and the obtained results demonstrate the applicability and efficiency of the proposed methodology, which should provide a valuable tool to supervise and control activated sludge processes. Huan Jing Ke Xue, 2002 Mar, 23(2), 50 - 4 {Using a two-stage SBR process for removal of organics and nitrification-denitrification via nitrite}; Zeng W et al.; High efficiency removal of organics and nitrogen by using a two-stage SBR process was introduced in this paper . Most of organics was removed in the first stage SBR reactor(SBR1) under the aerobic condition . Subsequently the second stage SBR reactor(SBR2) firstly operated under the aerabic condition for simultaneous nitrification and removal of a small amount of residual organics . Nitrification was controlled to the nitrite-type nitrification . Then denitrification happened in SBR2 under the anoxic condition . The petrochemical industry wastewater was used as external carbon sources in the denitrification . The experimental results indicated that in a two-stage SBR system, two kinds of biomass with the different function existed in the different reactors, which was beneficial to improve the treatment efficiency . The effluent COD reduced again because SBR2 removed COD which was left in SBR1 effluent . It resisted the disturbance of the high organic loading to nitrification . Consequently, as compared to a single SBR process, a two-stage SBR not only improved the treatment efficiency, but also saved the energy cost. Water Environ Res, 2002 Mar-Apr, 74(2), 187 - 99 The effectiveness of bioaugmentation in nitrifying systems stressed by a washout condition and cold temperature; Abeysinghe DH et al.; Bioaugmentation consists of adding selected strains of microorganisms with known capabilities to a biological process to improve performance . In this study, laboratory-scale completely stirred tank reactors were bioaugmented with nitrifying bacteria while operated under high-stress conditions for the nitrifiers: a 2-day solids retention time (SRT) at 22 degrees C or a 5-day SRT at 4 degrees C . Intensive sampling was carried out to document the effects of the bioaugmentation . To quantitatively interpret the effects of biomass addition on process performance, mathematical modeling was carried out . Experimental and modeling results indicate that the maximum effect of a one-time bioaugmentation depend on the dose and decays as bioaugmented nitrifiers are washed out . Daily maintenance dosing results in long-term good performance, provided that the dose is large enough . For severe stress, almost all of the biomass in the system must be added by bioaugmentation. Water Environ Res, 2002 Mar-Apr, 74(2), 177 - 86 Occurrence and distribution of ammonium in Iowa groundwater; Schilling KE; Excess ammonium in groundwater may lead to nitrification or loss of chlorine residuals in public drinking water supplies . In Iowa, where groundwater supplies nearly 75% of all drinking water used in the state, naturally occurring ammonium is found in all major aquifers, including two unconsolidated units and five bedrock aquifers . An evaluation of ammonium concentrations in 841 municipal water supply wells indicated highest concentrations were found most often in Quaternary wells . More than one-half of all Quaternary wells sampled in Iowa showed ammonium concentrations greater than 2 mg/L, and more than 5% had concentrations greater than 5 mg/L . Nearly 5% of all bedrock wells used in this study showed ammonium concentrations greater than 2 mg/L . Aquifers overlain by carbon-rich Pennsylvanian strata or glacial drift seemed most vulnerable to elevated ammonium . Alluvial aquifers were least vulnerable to elevated ammonium concentrations in Iowa municipal water supplies . Ammonium concentrations tended to be higher in wells that screened groundwater containing more dissolved solids, including sulfate, chloride and iron. Appl Environ Microbiol, 2002 Jun, 68(6), 3067 - 75 Influence of different cultivars on populations of ammonia-oxidizing bacteria in the root environment of rice; Briones AM et al.; Comparisons of the activities and diversities of ammonia-oxidizing bacteria (AOB) in the root environment of different cultivars of rice (Oryza sativa L.) indicated marked differences despite identical environmental conditions during growth . Gross nitrification rates obtained by the 15N dilution technique were significantly higher in a modern variety, IR63087-1-17, than in two traditional varieties . Phylogenetic analysis based on the ammonium monooxygenase gene (amoA) identified strains related to Nitrosospira multiformis and Nitrosomonas europaea as the predominant AOB in our experimental rice system . A method was developed to determine the abundance of AOB on root biofilm samples using fluorescently tagged oligonucleotide probes targeting 16S rRNA . The levels of abundance detected suggested an enrichment of AOB on rice roots . We identified 40 to 69% of AOB on roots of IR63087-1-17 as Nitrosomonas spp., while this subpopulation constituted 7 to 23% of AOB on roots of the other cultivars . These results were generally supported by denaturing gradient gel electrophoresis of the amoA gene and analysis of libraries of cloned amoA . In hydroponic culture, oxygen concentration profiles around secondary roots differed significantly among the tested rice varieties, of which IR63087-1-17 showed maximum leakage of oxygen . The results suggest that varietal differences in the composition and activity of root-associated AOB populations may result from microscale differences in O2 availability. Adv Space Res, 2000, 26(12), 2041 - 6 Inhibition of denitrification by ultraviolet radiation; Mancinelli RL et al.; It has been shown that UV-A (lambda=320-400 nm) and UV-B (lambda=280-320 nm) inhibit photosynthesis, nitrogen fixation and nitrification . The purpose of this study was to determine the effects, if any, on denitrification in a microbial community inhabiting the intertidal . The community studied is the microbial mat consisting primarily of Lyngbya that inhabits the Pacific marine intertidal, Baja California, Mexico . Rates of denitrification were determined using the acetylene blockage technique . Pseudomonas fluorescens (ATCC #17400) was used as a control organism, and treated similarly to the mat samples . Samples were incubated either beneath a PAR transparent, UV opaque screen (OP3), or a mylar screen to block UV-B, or a UV transparent screen (UVT) for 2 to 3 hours . Sets of samples were also treated with nitrapyrin to inhibit nitrification, or DCMU to inhibit photosynthesis and treated similarly . Denitrification rates were greater in the UV protected samples than in the UV exposed samples the mat samples as well as for the Ps fluorescens cultures . Killed controls exhibited no activity . In the DCMU and nitrapyrin treated samples denitrification rates were the same as in the untreated samples . These data indicate that denitrification is directly inhibited by UV radiation . c2001 COSPAR Published by Elsevier Science Ltd . All rights reserved. Microb Ecol, 2002 Apr, 43(3), 367 - 78 Epub 2002 Mar 28. Small-scale distribution of interstitial nitrite in freshwater sediment microcosms: the role of nitrate and oxygen availability, and sediment permeability; Stief P et al.; The spatial distribution of interstitial NO2(-) concentrations was studied in NO3(-)-exposed freshwater sediment microcosms, using pore water extractions as well as ion-selective microsensors . Porewater extractions revealed ecotoxicologically critical NO2(-) concentrations in hypoxic and anoxic sediment layers in which significant NO3(-) consumption took place . In contrast, the use of ion-selective microsensors demonstrated the high capacity of the thin oxic surface layer of the sediments to consume NO2(-) and to produce NO3(-) . Two modes of NO3(-) supply to the sediments were compared: In treatments with NO3(-) supply to the overlying water, a subsurface maximum of NO2(-) concentration was observed, coinciding with the site of maximum NO3(-) consumption . When NO3(-) was perfused up through the sediment cores, however, NO2(-) accumulated throughout the entire sediment column . Such spatially extensive NO2(-) accumulations were only observed in sediments poor in organic matter with a relatively high permeability . By manipulating the O2 content of the overlying water, the release of NO2(-) from the sediments could be influenced: In treatments with air-saturated overlying water, the sediments did not release detectable amounts of NO2(-) into the water phase . When kept hypoxic (25% air saturation) instead, significant NO2(-) accumulations were recorded in the overlying water . These findings suggest that in treatments with air-saturated overlying water, NO2(-) that was produced in deeper sediment layers (denitrifying conditions) was completely consumed at the oxic sediment surface (nitrifying conditions) before it could reach the overlying water. Microb Ecol, 2001 Jul, 42(1), 35 - 45 Spatiotemporal Stability of an Ammonia-Oxidizing Community in a Nitrogen-Saturated Forest Soil; Laverman AM et al.; Elevated levels of nitrogen input into various terrestrial environments in recent decades have led to increases in soil nitrate production and leaching . However, nitrifying potential and nitrifying activity tend to be highly variable over space and time, making broad-scale estimates of nitrate production difficult . This study investigates whether the high spatiotemporal variation in nitrate production might be explained by differences in the structure of ammonia-oxidizing bacterial communities in nitrogen-saturated coniferous forest soils . The diversity of ammonia-oxidizing bacteria of the b-subgroup Proteobacteria was therefore investigated using two different PCR-based approaches . The first targeted the 16S rRNA gene and involved temporal temperature gradient electrophoresis (TTGE) of specifically amplified PCR products, with subsequent band excision and nucleotide sequence determination . The second approach involved the cloning and sequencing of PCR-amplified amoA gene fragments . All recovered 16S rDNA sequences were closely related to the culture strain Nitrosospira sp . AHB1, which was isolated from an acid soil and is affiliated with Nitrosospira cluster 2, a sequence group previously shown to be associated with acid environments . All amoA-like sequences also showed a close affinity with this acid-tolerant Nitrosospira strain, although greater sequence variation could be detected in the amoA analysis . The ammonia-oxidizing bacterial community in the nitrogen-saturated coniferous forest soil was determined to be very stable, showing little variation between different organic layers and throughout the year, despite large differences in the total Bacterial community structure as determined by 16S rDNA DGGE community fingerprinting . These results suggest that environmental heterogeneity affecting ammonia oxidizer numbers and activity, and not ammonia oxidizer community structure, is chiefly responsible for spatial and temporal variation in nitrate production in these acid forest soils. Microb Ecol, 2001 Oct, 42(3), 228 - 237 Species Diversity of Uncultured and Cultured Populations of Soil and Marine Ammonia Oxidizing Bacteria; Smith Z et al.; Although molecular techniques are considered to provide a more comprehensive view of species diversity of natural microbial populations, few studies have compared diversity assessed by molecular and cultivation-based approaches using the same samples . To achieve this, the diversity of natural populations of ammonia oxidising bacteria in arable soil and marine sediments was determined by analysis of 16S rDNA sequences from enrichment cultures, prepared using standard methods for this group, and from 16S rDNA cloned from DNA extracted directly from the same environmental samples . Soil and marine samples yielded 31 and 18 enrichment cultures, respectively, which were compared with 50 and 40 environmental clones . There was no evidence for selection for particular ammonia oxidizer clusters by different procedures employed for enrichment from soil samples, although no culture was obtained in medium at acid pH . In soil enrichment cultures, Nitrosospira cluster 3 sequences were most abundant, whereas clones were distributed more evenly between Nitrosospira clusters 2, 3, and 4 . In marine samples, the majority of enrichment cultures contained Nitrosomonas, whereas Nitrosospira sequences were most abundant among environmental clones . Soil enrichments contained a higher proportion of identical sequences than clones, suggesting laboratory selection for particular strains, but the converse was found in marine samples . In addition, 16% of soil enrichment culture sequences were identical to those in environmental clones, but only 1 of 40 marine enrichments was found among clones, indicating poorer culturability of marine strains represented in the clone library, under the conditions employed . The study demonstrates significant differences in species composition assessed by molecular and culture-based approaches but indicates also that, employing only a limited range of cultivation conditions, 7% of the observed sequence diversity in clones of ammonia oxidizers from these environments could be obtained in laboratory enrichment culture . Further studies and experimental approaches are required to determine which approach provides better representation of the natural community. Appl Biochem Biotechnol, 2002 Spring, 98-100, 753 - 64 Mass production of methane from food wastes with concomitant wastewater treatment; Kim JK et al.; We developed a process for production of methane at a pilot scale . This process consists of three stages . The first stage is a semianaerobic hydrolysis/acidogenic step in which organic wastes are converted to various sugars, amino acids, and volatile fatty acids (VFAs) . Operation temperature and pH were 45 degrees C, and 5.0-5.5, respectively . Hydraulic retention time (HRT) was 2 d . To remove the putrid odor and to enhance the hydrolysis of organic wastes, a mixture of bacteria isolated from landfill soil was inoculated into the reactor . Total chemical oxygen demand (tCOD) and biological oxygen demand (BOD) were 36,000 mg/L and 40,000 mg/L, respectively . The second stage was an anaerobic acidogenic process, which can produce large amount of VFAs including acetate, propionate, butyrate, valerate, and caproate . Operation temperature and pH were 35 degrees C, and 5.0-5.5, respectively . HRT was 2 d . The third stage was a strictly anaerobic methane fermentation step producing methane and carbon dioxide from VFAs . The working volume of upflow anaerobic sludge blanket (UASB) type reactor was 1200 L, and operation temperature and pH were 41 degrees C, and 7.7-7.9, respectively . HRT was 12 d . Seventy two percent of methane at maximum was generated and the yield was 0.45-0.50 m3/kgVS of food wastes . Through the process, 88% of tCOD and 95% of BOD were removed . The wastewater was treated with the biological aerobic and anaerobic filters immobilized with heterotrophic and autotrophic nitrifying and denitrifying bacteria . Ninety percent of total nitrogen (T-N) was removed by this treatment . The residual T-N and total phosphorous (T-P) were removed by the algal periphyton treatment system . The final concentrations of nitrogen and phosphorous in the drain water were 53 and 7 mg/L, respectively. Environ Toxicol Chem, 2002 May, 21(5), 954 - 61 Low metal bioavailability in a contaminated urban site; Ge Y et al.; Bioavailability of Cd, Cu, Ni, Pb, and Zn in a metal-enriched railway yard in Montreal, Quebec, Canada was assessed using metal speciation, plant uptake, and microbial assays . Metal speciation of extracted soil solutions was estimated using the Windmere Humic Aqueous Model . In soil solutions, free Cd, Ni, and Zn ions represented as much as 80%, 72%, and 62%, respectively, of the total dissolved metals . Copper and Pb were strongly bound by dissolved organic matter, and metal-fulvic acid complexes represented as much as 99% of the total dissolved metals . Three field-collected plant species (dandelion, bladder campion, and chicory) varied in their tendency to accumulate metals in either their leaves or roots . Chicory grown in the greenhouse had significantly higher metal bioconcentration factors than wild chicory . Although the site studied is considered to be contaminated, no metal pool, such as free ions or dissolved or total soil metals, consistently predicted metal uptake by potted chicory . Regression analysis revealed that soil total metal concentrations could adequately predict tissue accumulations of Cd, Ni, Pb, and Zn in bladder campion but only Cd and Zn in dandelion . Data from microbial assays also showed that the soil respiration was not affected by the metal contamination, but that nitrification was inhibited for the most contaminated soils . These results indicate that the metal bioavailability in the railway yard is low, but they also suggest that nitrogen cycling may be affected. Biosci Biotechnol Biochem, 2002 Mar, 66(3), 632 - 5 Isolation and characterization of cbbL and cbbS genes encoding form I ribulose-1,5-bisphosphate carboxylase/oxygenase large and small subunits in Nitrosomonas sp . strain ENI-11; Hirota R et al.; The cbbL and cbbS genes encoding form I ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) large and small subunits in the ammonia-oxidizing bacterium Nitrosomonas sp . strain ENI-11 were cloned and sequenced . The deduced gene products, CbbL and CbbS, had 93 and 87% identity with Thiobacillus intermedius CbbL and Nitrobacter winogradskyi CbbS, respectively . Expression of cbbL and cbbS in Escherichia coli led to the detection of RubisCO activity in the presence of 0.1 mM isopropyl-beta-D-thiogalactopyranoside (IPTG) . To our knowledge, this is the first paper to report the genes involved in the carbon fixation reaction in chemolithotrophic ammonia-oxidizing bacteria. Bioresour Technol, 2002 Apr, 82(2), 183 - 9 The evaluation of enhanced nitrification by immobilized biofilm on a clinoptilolite carrier; Park SJ et al.; This study was conducted to evaluate the effect of clinoptilolite on nitrification in activated sludge (AS), and was focused on a relationship between ammonium exchange capacity of this mineral and improvement of nitrification . In batch experiments, the adsorption property of biofilm-attached clinoptilolite did not show substantial difference from that of natural clinoptilolite, indicating that bioregeneration became completely achieved without any regenerant in the AS . The AS with added clinoptilolite (ZR) was compared to the control AS (CR) when the ratio of chemical oxygen demand (COD) to total kjeldahl nitrogen (TKN) of influent, i.e . C/N ratio, was varied from 3.25 to 7.5 at a hydraulic retention time (HRT) of 3 h . Enhanced nitrification was comparatively observed for the ZR as C/N ratio gradually increased . The results indicated that the clinoptilolite provided a relatively low C/N ratio for nitrifiers, due to ammonium adsorption of this mineral, and consequently nitrification was accelerated. Environ Technol, 2002 Mar, 23(3), 303 - 8 Nitrification utilizing CaCO3 as the buffering agent; Green M et al.; Nitrification utilizing chalk (calcium carbonate) as the buffering agent was investigated . Three different fluidized bed reactor configurations were examined in order to study the effect of reactor layout on nitrification and concomitant chalk dissolution . The first system consisted of two interconnected columns with high recycle rate, one containing zeolite as the carrier for the nitrifying biomass and the other chalk as the buffering agent . The second reactor system consisted of a single column containing both zeolite and chalk particles . In the third system, nitrification was carried out in a single column where chalk particles were used both as the carrier for the biomass and as the buffer . Results showed that only the reactor with chalk acting as both the buffering agent and the biomass carrier could be operated without external buffer (NaHCO3) addition . This system operated at high ammonium removal rates of up to 2.5 g N l(-1) reactor d(-1) even though the bulk solution of the reactor had a low pH of 5.5 . The high nitrification efficiency at this low pH was probably mainly a result of a favorable microenvironment surrounding the nitrifying biomass attached to the chalk. J Microbiol Methods, 2002 Jul, 50(2), 189 - 203 Denaturing gradient gel electrophoresis (DGGE) approaches to study the diversity of ammonia-oxidizing bacteria; Nicolaisen MH et al.; Denaturing gradient gel electrophoresis (DGGE) of PCR amplicons of the ammonia monooxygenase gene (amoA) was developed and employed to investigate the diversity of ammonia-oxidizing bacteria (AOB) in four different habitats . The results were compared to DGGE of PCR-amplified partial 16S rDNA sequences made with primers specific for ammonia-oxidizing bacteria . Potential problems, such as primer degeneracy and multiple gene copies of the amoA gene, were investigated to evaluate and minimize their possible impact on the outcome of a DGGE analysis . amoA and 16S rDNA amplicons were cloned, and a number of clones screened by DGGE to determine the abundance of different motility types in the clone library . The abundance of clones was compared to the relative intensity of bands emerging in the band pattern produced by direct amplification of the genes from the environmental sample . Selected clones were sequenced to evaluate the specificity of the respective primers . The 16S rDNA primer pair, reported to be specific for ammonia-oxidizing bacteria (AOB), generated several sequences that were not related to the known Nitrosospira-Nitrosomonas group and, thus, not likely to be ammonia oxidizers . However, no false positives were found among the sequences retrieved with the modified amoA primers . Some phylogenetic information could be deduced from the position of amoA bands in DGGE gels . The Nitrosomonas-like sequences were found within a denaturant range from 30% to 46%, whereas the Nitrosospira-like sequences migrated to 50% to 60% denaturant . The majority of retrieved sequences from all four habitats with high ammonia loads were Nitrosomonas-like and only few Nitrosospira-like sequences were detected. Water Res, 2002 Mar, 36(6), 1439 - 48 Distribution and activity of ammonia oxidizing bacteria in a large full-scale trickling filter; Persson F et al.; The biofilm in a full-scale nitrifying trickling filter (NTF) treating municipal wastewater has been investigated with microbiological methods using fluorescence in situ hybridization (FISH) with 16S rRNA oligonucleotide probes in combination with confocal laser scanning microscopy (CLSM) and mathematical modeling using a dynamic multi-species biofilm reactor model . Ammonia oxidizing bacteria (AOB) were found to belong to the genus Nitrosomonas at different depths in the NTF at every sampling occasion, corresponding to different long-term operational conditions for the NTF . Both the measurements and the corresponding simulated predictions showed the same general trend of a decrease with filter depth of the amount of biofilm, the proportion of AOB to all bacteria and the total amount of AOB . The latter decreased by several times from top to bottom of the NTF . Measurements and simulations of potential ammonium oxidizing activity in the biofilm also showed a decreasing activity with depth in the NTF, which generally was operating at close to complete nitrification . However, no difference was observed when the activity was normalized to the amount of biofilm, despite decreasing proportions of AOB to all bacteria with depth in the NTF . This could be explained by diffusion limitations in the biofilm from the upper parts of the NTF according to the biofilm reactor model . The relatively good agreement between the simulations and the measurements shows that the kind of biofilm reactor model used can qualitatively describe an averaged behavior and averaged composition of the biofilm in the reactor. Chemosphere, 2002 May, 47(5), 535 - 45 A comparison of five rapid direct toxicity assessment methods to determine toxicity of pollutants to activated sludge; Dalzell DJ et al.; Five rapid direct toxicity assessment methods were used in three European partner countries to determine the toxicity of single toxicants, mixed toxicants and real industrial wastes . The final aim was to protect microbial degradation of organic wastes in biological treatment processes and hence enhance the quality of treated effluents to be discharged to the environment . Nitrification inhibition, Respirometry, Adenosine triphosphate luminescence and Enzyme inhibition were tested utilising activated sludge as the testing matrix . The Vibrio fischeri toxicity test was used as a surrogate to compare the various microbial bioassays . The IC50 (toxicant concentration eliciting a 50% inhibitory effect) was determined for a number of pollutants including single toxicants Cd, Cr, Cu, Zn, 3,5-dichlorophenol, toluene and linear alkylbenzenesulphonate (LAS); a standard mixture of metals and LAS; a standard mixture of organics and LAS, and 16 industrial effluents . The V . fischeri bioassay was also chosen in order to assess quality control of toxicant preparation during testing in the different laboratories of the partner countries . Comparisons of sensitivity, cost of implementation, cost per test, relevance, and ease of use were made . The most sensitive bioassays were V . fischeri and Nitrification inhibition, however, this depended in the main on the pollutant and mixtures tested . It is recommended that during assessment of wastewater toxicity a suite of tests be used rather than reliance on one particular test. Water Environ Res, 2002 Jan-Feb, 74(1), 68 - 76 A new process for enriching nitrifiers in activated sludge through separate heterotrophic wasting from biofilm carriers; Parker DS et al.; A new process, the biofilm-activated sludge innovative nitrification (BASIN) process, consisting of a moving-bed biofilm reactor (MBBR) with separate heterotrophic wasting, followed by an activated-sludge process, has been proposed to reduce the volumetric requirements of the activated-sludge process for nitrification . The basic principle is to remove chemical oxygen demand on the biofilm carriers by heterotrophic organisms and then to waste a portion of the heterotrophic biomass before it can be released into the activated-sludge reactor . By this means, the amount of heterotrophic organisms grown in the activated-sludge reactor is reduced, thereby reducing the volume of that tank needed for nitrification . For nitrification applications, the simplest method for stripping biomass was to use an in-tank technique using high shearing rates with aeration . Bench-scale testing showed sludge yields in the BASIN process were one-half of that in a control activated-sludge process and twice that of a process line with intermediate settling between the MBBR and activated-sludge stage . Critical washout solids retention times for nitrifiers were the same for all three lines, so activated-sludge volumes for the BASIN process could be reduced by 50% compared with the control . Originally conceived process concepts for the BASIN process were confirmed by the experimental work. Biodegradation, 2001, 12(5), 359 - 66 Optimal operational factors for nitrite accumulation in batch reactors; Bae W et al.; The environmental factors that affected the accumulation of nitrite in nitrifying reactors were investigated using a mixed culture . A batch reactor with 50 mg-N/l of ammonia was used . The pH, temperature and dissolved oxygen concentration were varied . The concentration of unionized free ammonia also changed with the oxidation of ammonia and the variation of pH and temperature . The accumulation of nitrite was affected sensitively by pH and temperature . A higher nitrite concentration was observed at pH 8-9 or temperature around 30 degrees C . The dissolved oxygen also affected, giving the highest nitrite accumulation at around 1.5 mg/l . These were the favored conditions for nitrite production . The free ammonia concentration influenced the nitrite accumulation also, by inhibiting nitrite oxidation . The inhibition became apparent at a concentration of approximately 4 mg/l or above, but insignificant at below 1 mg/l . Thus, simultaneously high free ammonia concentration and maximum specific ammonia-oxidation rate (above 15 x 10(-3) mg-N/mg-VSS x h) were needed for a significant nitrite accumulation . When the two conditions were met, then the highest accumulation was observed when the ratio of the maximum specific oxidation rate of ammonia to the maximum specific oxidation rate of nitrite (ka/kn) was highest . Under the optimal operating conditions of pH 8, 30 degrees C and 1.5 mg/l of dissolved oxygen, as much as 77% of the removed ammonia accumulated in nitrite. Mar Environ Res, 2002 May, 53(4), 381 - 402 The influence of long emersion on biota, ammonium fluxes and nitrification in intertidal sediments of Marennes-Oléron Bay, France; Laima M et al.; A comparative study between waterlogged and reflooded intertidal sediments was undertaken in March and June 1999 through statistical analysis of selected sediment parameters (biota, salinity, O2, Eh), pool sizes and benthic fluxes of nutrients (NH4+, NO2-, NO3-) and nitrification rates . In March samples, absence of polychaetes and oligochaetes from upper sediment horizons were due to erosional events sweeping away surface sediments . Presence of richer annelid assemblages in June samples indicated more stable hydrodynamic conditions that favoured the development of benthic microalgae biofilms . Dewatering of sediments during a 3-day emersion period promoted a salinity rise on top layers, migration of pore water ions towards the sediment surface, and created sediment fissures that accelerated water exchange on reflooding . Reflooded and waterlogged sediment systems were comparable with respect to the release of NH4+ to overlying water but were different with respect to nitrification rates . Sediment-water NH4+ fluxes were higher (P = 0.011) in March (3.3 mmol m(-2) day(-1) compared to June (1.4 mmol m(-2) day(-1) due to higher macrofauna biomasses and lower benthic microalgae concentrations in March samples . Potential nitrification rates (range from 19 to 60 mmol NO3- (-2) day(-1)) were not statistically different between March and June . A thinner oxic layer in reflooded compared with waterlogged systems reflects a decrease of O2 diffusion into sediment at high salinities which resulted in the fall of the actual nitrification rates (P < 0.05) . Our data suggest that long term dessication of intertidal sediments may depress the nitrification process at the ecosystem level. Water Sci Technol, 2002, 45(6), 199 - 208 Improving the predictions of ASM2d through modelling in practice; Larrea L et al.; The paper presents the adjustments carried out on the structure and in some default values of the kinetic coefficients of the ASM2d model in order to get an improved prediction for the experimental results obtained in pilot scale plants studies with different activated sludge treatment processes for carbon, nitrogen and phosphorous removal . In order to predict the high effluent filtered COD experimentally observed in high rate processes for carbon removal, a new model structure has been proposed, incorporating into the carbon model a soluble fraction of the slowly biodegradable substrate . Studies with the step feed and the alternating processes showed simultaneous nitrification-denitrification in aerated reactors which was predicted with increased values in the oxygen saturation coefficients for heterotrophic and autotrophic biomass . Both processes also showed loss of the denitrification capacity under unfavourable conditions, such us rains and low anoxic fraction, which required a very large decrease in the value of the reduction factor for denitrification so as to improve the predictions for effluent nitrate experimental results . Regarding phosphorus removal, the ASM2d model showed a satisfactory predictive capacity . For improved predictions of phosphorus release in anaerobic conditions, high values of the rate constant for storage of X(PHA) and low values of the anaerobic hydrolysis reduction factor were used . For phosphorus uptake in aerobic and anoxic conditions satisfactory predictions were obtained using the default values. Water Sci Technol, 2002, 45(6), 169 - 76 Model-based evaluation of a new upgrading concept for N-removal; Salem S et al.; Mathematical modelling is considered a time and cost-saving tool for evaluation of new wastewater treatment concepts . Modelling can help to bridge the gap between lab and full-scale application . Bio-augmentation can be used to obtain nitrification in activated sludge systems with a limited aerobic sludge retention time . In the present study the potential for augmenting the endogenous nitrifying population is evaluated . Implementing a nitrification reactor in the sludge return line fed with sludge liquor with a high ammonia concentration leads to augmentation of the native nitrifying population . Since the behaviour of nitrifiers is relatively well known, a choice was made to evaluate this new concept mainly based on mathematical modelling . As an example an existing treatment plant (WWTP Walcheren, The Netherlands) that needed to be upgraded was used . A mathematical model, based on the TUDP model and implemented in AQUASIM was developed and used to evaluate the potential of this bioaugmentation in the return sludge line . A comparison was made between bio-augmentation and extending the existing aeration basins and anoxic tanks . The results of both modified systems were compared to give a quantitative basis for evaluation of benefits gained from such a system . If the plant is upgraded by conventional extension it needs an increase in volume of about 225%; using a bioaugmentation in the return sludge line the total volume of the tanks needs to be expanded by only 75% (including the side stream tanks) . Based on the modelling results a decision was made to implement the bioaugmentation concept at full scale without further pilot scale testing, thereby strongly decreasing the scale-up period for this process. Water Sci Technol, 2002, 45(6), 137 - 44 Effect of solids retention time and wastewater characteristics on biological phosphorus removal; Henze M et al.; The paper deals with the effect of wastewater, plant design and operation in relation to biological nitrogen and phosphorus removal and the possibilities to model the processes . Two Bio-P pilot plants were operated for 2.5 years in parallel receiving identical wastewater . The plants had SRT of 4 and 21 days, the latter had nitrification and denitrification . The plant with 4 days SRT had much more variable biomass characteristics, than the one with the high SRT . The internal storage compounds, PHA, were affected significantly by the concentration of fatty acids or other easily degradable organics in the wastewater, and less by the plant lay-out . The phosphorus removal is mainly dependent on availability in the wastewater of fatty acids but also by the suspended solids in the effluent, which is higher in the plant with nitrification-denitrification, probably due to a higher SVI or denitrification in the settler . The addition of glucose to the influent seems to have an effect on the performance of the plants similar to that of acetic acid . In spite of great load variations over time to the pilot plants and the different operational modes, the study of population dynamics showed less significant variations with time which has importance in relation to modelling . The overall conclusion of the comparison between the two plants is that the biological phosphorus removal efficiency under practical operating conditions is affected by the SRT in the plant and the wastewater composition . Thus great care should be taken when extrapolating results from one type of plant to another . Indirectly the experiments confirm that results from lab-experiments with artificial wastewater are difficult to extrapolate through modelling to real life wastewater and conditions . The 2.5 years time series can be valuable in verification of models for Nitrogen and Enhanced Biological Phosphorus Removal. Microb Ecol, 2002 Jan, 43(1), 154 - 67 Epub 2001 Jan 23. Enrichment of autotrophic anaerobic ammonium-oxidizing consortia from various wastewaters; Toh SK et al.; The option for biological nitrogen removal has recently been broadened with the description of simultaneous nitrification/denitrification, anaerobic ammonium oxidation (ANAMMOX) and the concept of CANON (completely autotrophic nitrogen removal over nitrite) . An autotrophic anaerobic ammonium oxidation (AAAO) consortium was successfully selected and enriched from municipal treatment plant sludges in Sydney, Australia, but not from industrial coke-oven wastewater sludges . Chemolithoautotrophic basic salt (CLABS) medium was used in the selection of AAAO organisms and chloramphenicol was added to the initial stage of selection to eliminate denitrifiers . Two different temperatures, 37 degrees C and 55 degrees C, were used in the selection of mesophilic and thermophilic consortia, respectively . Thermophilic AAAO organisms were not selected at 55 degrees C . Mesophilic AAAO activities, however, were evident in both batch and continuous cultures, whereby ammonium was consumed concurrently with a decrease of nitrite, giving a ratio of 1:1-1:1.3 in ammonium removal rate over nitrite consumption rate . A continuous-mode mesophilic fixed-bed reactor was established to enrich the AAAO consortium . After 1 year, biofilms, pinkish in color, had developed on the support media and side wall of the feed-line tubing . Ammonium and nitrite consumption increased from approximately 15 mg to 60 mg d(-1) L(-1) over a period of 243 days . Later, transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH) techniques revealed that the dominant cell type in the AAAO consortium had a similar morphology and 16S rDNA sequence homology to that of the recently described ANAMMOX organism, "Brocadia anammoxidans". Microb Ecol, 2002 Jan, 43(1), 26 - 33 Epub 2001 Dec 07. Immunological detection of Nitrospira-like bacteria in various soils; Bartosch S et al.; Chemolithotrophic nitrite oxidizers were enriched from five different soils including freshwater marsh, permafrost, garden, agricultural, and desert soils and monitored during the cultivation procedure . Immunoblot analysis was used to identify the nitrite oxidizing organisms with monoclonal antibodies, which recognize the key enzyme of nitrite oxidation in a genus-specific reaction {Bartosch et al . (1999) Appl Environ Microbiol 65:4126-4133} . The morphological characteristics of the enriched nitrite oxidizers were additionally studied using transmission electron microscopy (TEM) and fluorescence microscopy . By means of the antibodies and TEM analysis Nitrospira could be clearly identified in enrichment cultures derived from freshwater marsh and from permafrost soil . Nitrospira cells were enriched simultaneously with cells of the genus Nitrobacter when nitrite concentrations of 0.2 g of NaNO2 L(-1) were used . However, in enrichment cultures containing 2 g of NaNO2 L(-1) Nitrobacter was exclusively detected . During fluorescence microscopic observations of DAPI stained samples microcolonies were found in enrichment cultures from freshwater marsh, permafrost, garden, and agricultural soil . They had a similar morphology to Nitrospira-like microcolonies from activated sludge . In conclusion, Nitrospira seems to be not only a common aquatic but also a usual soil bacterium. Mar Pollut Bull, 2002 Feb, 44(2), 142 - 8 The inhibition of marine nitrification by ocean disposal of carbon dioxide; Huesemann MH et al.; In an attempt to reduce the threat of global warming, it has been proposed that the rise of atmospheric carbon dioxide concentrations be reduced by the ocean disposal of CO2 from the flue gases of fossil fuel-fired power plants . The release of large amounts of CO2 into mid or deep ocean waters will result in large plumes of acidified seawater with pH values ranging from 6 to 8 . In an effort to determine whether these CO2-induced pH changes have any effect on marine nitrification processes, surficial (euphotic zone) and deep (aphotic zone) seawater samples were sparged with CO2 for varying time durations to achieve a specified pH reduction, and the rate of microbial ammonia oxidation was measured spectrophotometrically as a function of pH using an inhibitor technique . For both seawater samples taken from either the euphotic or aphotic zone, the nitrification rates dropped drastically with decreasing pH . Relative to nitrification rates in the original seawater at pH 8, nitrification rates were reduced by ca . 50% at pH 7 and more than 90% at pH 6.5 . Nitrification was essentially completely inhibited at pH 6 . These findings suggest that the disposal of CO2 into mid or deep oceans will most likely result in a drastic reduction of ammonia oxidation rates within the pH plume and the concomitant accumulation of ammonia instead of nitrate . It is unlikely that ammonia will reach the high concentration levels at which marine aquatic organisms are known to be negatively affected . However, if the ammonia-rich seawater from inside the pH plume is upwelled into the euphotic zone, it is likely that changes in phytoplankton abundance and community structure will occur . Finally, the large-scale inhibition of nitrification and the subsequent reduction of nitrite and nitrate concentrations could also result in a decrease of denitrification rates which, in turn, could lead to the buildup of nitrogen and unpredictable eutrophication phenomena . Clearly, more research on the environmental effects of ocean disposal of CO2 is needed to determine whether the potential costs related to marine ecosystem disturbance and disruption can be justified in terms of the perceived benefits that may be achieved by temporarily delaying global warming. Arch Microbiol, 2002 May, 177(5), 371 - 80 Epub 2002 Feb 14. Evaluation of non-cyanobacterial genome sequences for occurrence of genes encoding proteins homologous to cyanophycin synthetase and cloning of an active cyanophycin synthetase from Acinetobacter sp . strain DSM 587; Krehenbrink M et al.; All publicly accessible microbial genome databases were searched for the occurrence of genes encoding proteins homologous to the cyanophycin synthetase (CphA) of Synechocystis sp . strain PCC 6803 in order to reveal the capability of microorganisms not belonging to the cyanobacteria to synthesize cyanophycin . Among 65 genome sequences, genes homologous to cphA were found in Acinetobacter sp . strain ADP1 (encoding a protein homologous to CphA with 40% amino acid identity), Bordetella bronchiseptica strain RB50 (39%), Bordetella pertussis strain Tohama I (39%), Bordetella parapertussis strain 12822 (39%), Clostridium botulinum strain ATCC 3502 (39%), Desulfitobacterium hafniense strain DCB-2 (38%) and Nitrosomonas europaea strain ATCC 25978 (37%) . The gene homologous to cphA from Acinetobacter sp . strain DSM 587 was amplified by PCR, ligated to the vector pBluescript SK(-) downstream of the lac promoter and introduced into Escherichia coli . The recombinant strain of E . coli expressed CphA activity at up to 1.2 U/mg protein and accumulated cyanophycin to up to 7.5% of the cellular dry matter, indicating that CphA of Acinetobacter sp . strain DSM 587 is functionally active . In Acinetobacter sp . strain DSM 587 itself, cyanophycin accumulated to up to 1.4% of the total protein under phosphate-limited conditions, and cyanophycin synthetase activity was detected, which indicated the function of cyanophycin as a storage compound in this strain. Appl Biochem Biotechnol, 2001 Spring, 91-93, 437 - 46 Nitrification and denitrification processes for biologic treatment of industrial effluents; Tavares CR et al.; Nitrification process performance was evaluated using a three-phase fluidized-bed bioreactor . A synthetic effluent was used for this experiment containing 180-230 mg/L of chemical oxygen demand (COD), 25-30 mg/L of N-NH4+, 12 to 13 mg/L of total phosphorous, and micronutrients . The bioreactor used for denitrification behaved as completely mixed . The results indicate that the nitrification process was efficient, reaching efficiencies of about 98% . The best results related to the efficiency of the denitrification process were obtained when the processes were supplemented with the carbon source . The results indicated an efficiency of 86-98% COD removal. Plant Physiol, 2002 Apr, 128(4), 1490 - 500 Evolution of sucrose synthesis; Lunn JE; Cyanobacteria and proteobacteria (purple bacteria) are the only prokaryotes known to synthesize sucrose (Suc) . Suc-P synthase, Suc-phosphatase (SPP), and Suc synthase activities have previously been detected in several cyanobacteria, and genes coding for Suc-P synthase (sps) and Suc synthase (sus) have been cloned from Synechocystis sp . PCC 6803 and Anabaena (Nostoc) spp., respectively . An open reading frame in the Synechocystis genome encodes a predicted 27-kD polypeptide that shows homology to the maize (Zea mays) SPP . Heterologous expression of this putative spp gene in Escherichia coli, reported here, confirmed that this open reading frame encodes a functional SPP enzyme . The Synechocystis SPP is highly specific for Suc-6(F)-P (K(m) = 7.5 microM) and is Mg(2+) dependent (K(a) = 70 microM), with a specific activity of 46 micromol min(-1) mg(-1) protein . Like the maize SPP, the Synechocystis SPP belongs to the haloacid dehalogenase superfamily of phosphatases/hydrolases . Searches of sequenced microbial genomes revealed homologs of the Synechocystis sps gene in several other cyanobacteria (Nostoc punctiforme, Prochlorococcus marinus strains MED4 and MIT9313, and Synechococcus sp . WH8012), and in three proteobacteria (Acidithiobacillus ferrooxidans, Magnetococcus sp . MC1, and Nitrosomonas europaea) . Homologs of the Synechocystis spp gene were found in Magnetococcus sp . MC1 and N . punctiforme, and of the Anabaena sus gene in N . punctiforme and N . europaea . From analysis of these sequences, it is suggested that Suc synthesis originated in the proteobacteria or a common ancestor of the proteobacteria and cyanobacteria. J Bacteriol, 2002 May, 184(9), 2557 - 60 Nitrite reductase of Nitrosomonas europaea is not essential for production of gaseous nitrogen oxides and confers tolerance to nitrite; Beaumont HJ et al.; A gene that encodes a periplasmic copper-type nitrite reductase (NirK) was identified in Nitrosomonas europaea . Disruption of this gene resulted in the disappearance of Nir activity in cell extracts . The nitrite tolerance of NirK-deficient cells was lower than that of wild-type cells . Unexpectedly, NirK-deficient cells still produced nitric oxide (NO) and nitrous oxide (N(2)O), the latter in greater amounts than that of wild-type cells . This demonstrates that NirK is not essential for the production of NO and N(2)O by N . europaea . Inactivation of the putative fnr gene showed that Fnr is not essential for the expression of nirK. Water Sci Technol, 2002, 45(4-5), 93 - 100 In-situ measurement of ammonium and nitrate in the activated sludge process; Rieger L et al.; A new in-situ probe is presented for the continuous measurement of ammonium and nitrate in wastewater . It requires no sample preparation and is installed directly in the process liquid . This new low-cost probe significantly reduces investment and operating costs and requires minimum maintenance . The paper describes the sensor principle and test results from three different probe locations: the primary clarifier effluent, the activated sludge tank and the nitrifying biofilter influent . Reference measurements were carried out by means of conventional analyzers with ultrafiltration, an in-situ UV spectrometer for the nitrate and laboratory analysis of spot and 2h-composite samples . The aim of the study was to investigate the operational reliability and accuracy of the new probe and the expenditure required for its maintenance and calibration . The tests showed that the new probe performed very well overall and required minimum maintenance . Some problems were observed during the biofilter plant test . They are assumed to be related to substantial changes in the wastewater composition. Water Sci Technol, 2002, 45(4-5), 45 - 52 Control of the aeration volume in an activated sludge process for nitrogen removal; Samuelsson P et al.; Biological nitrogen removal in an activated sludge process is obtained by two biological processes; nitrification and denitrification . Nitrifying bacteria need dissolved oxygen and a sufficiently large aeration volume for converting ammonium to nitrate in the wastewater . The objective of this paper is to develop an automatic control strategy for adjusting the aerated volume so that the effluent ammonium level can be kept close to a desired value despite major changes in the influent load . The strategy is based on applying exact linearization of the IAWO Activated Sludge Process Model No 1 . Simulation results show that the suggested controller effectively attenuates process disturbances. Water Sci Technol, 2002, 45(4-5), 413 - 20 Simulation of a nitrification control concept considering influent ammonium load; Krause K et al.; Buchenhofen wastewater treatment plant of Wupperverband (650,000 p.e.) is currently being expanded for targeted nitrogen elimination . In view of the limited space available for extension, an optimized control concept is to be used in order to minimize the number of additional tanks required . This concept was investigated by dynamic simulation based on Activated Sludge Model No . 1 . The investigations included a pure feedback control configuration and a configuration combining feedback und feedforward control, considering the influent ammonium load, for aeration . The results show that combined feedforward/feedback control has significant advantages over pure feedback control . In particular, this configuration allows a reduction in the effluent NH4-N peaks, which is especially important because of the low NH4-N limit of 5 mg NH4-N/L in a grab sample. Water Sci Technol, 2002, 45(4-5), 317 - 24 A hedging point strategy--balancing effluent quality, economy and robustness in the control of wastewater treatment plants; Ingildsen P et al.; An operational space map is an efficient tool to compare a large number of operational strategies to find an optimal choice of setpoints based on a multicriterion . Typically, such a multicriterion includes a weighted sum of cost of operation and effluent quality . Due to the relative high cost of aeration such a definition of optimality result in a relatively high fraction of the effluent total nitrogen in the form of ammonium . Such a strategy may however introduce a risk into operation because a low degree of ammonium removal leads to a low amount of nitrifiers . This in turn leads to a reduced ability to reject event disturbances, such as large variations in the ammonium load, drop in temperature, the presence of toxic/inhibitory compounds in the influent etc . Hedging is a risk minimisation tool, with the aim to "reduce one's risk of loss on a bet or speculation by compensating transactions on the other side" (The Concise Oxford Dictionary (1995)) . In wastewater treatment plant operation hedging can be applied by choosing a higher level of ammonium removal to increase the amount of nitrifiers . This is a sensible way to introduce disturbance rejection ability into the multi criterion . In practice, this is done by deciding upon an internal effluent ammonium criterion . In some countries such as Germany, a separate criterion already applies to the level of ammonium in the effluent . However, in most countries the effluent criterion applies to total nitrogen only . In these cases, an internal effluent ammonium criterion should be selected in order to secure proper disturbance rejection ability. Water Sci Technol, 2002, 45(4-5), 309 - 16 A supervisory control system for optimising nitrogen removal and aeration energy consumption in wastewater treatment plants; Serralta J et al.; A fuzzy logic supervisory control system for optimising nitrogen removal and aeration energy consumption has been developed . This control system allows optimising and controlling the dissolved oxygen (DO) concentration in the aerobic reactors, the blowers discharge pressure and the effluent ammonia and nitrate concentrations . DO is controlled by adjusting control valve opening and blower discharge pressure is controlled by modifying rotational speed of the blowers . Optimum nitrification/denitrification is achieved by modifying the DO set point in the last aerobic reactor and the internal recirculation . This system has been tested by simulation in a Bardenpho process using the Activated Sludge Model No2 . A significant improvement in stability on the activated sludge process is achieved . Moreover, significant energy saving has been achieved with this control strategy. Water Sci Technol, 2002, 45(4-5), 271 - 8 Application of toxicity monitor using nitrifying bacteria biosensor to sewerage systems; Inui T et al.; Toxic substances may be included in wastewater influent and can damage biological processing of wastewater treatment, therefore continuous toxic-monitoring of wastewater influent is needed . This paper describes the potential toxic-monitoring applications of the toxicity monitor using a nitrifying bacteria biosensor to sewerage systems . The results of sensitivity tests show that aspects of wastewater do not affect the sensor sensitivity and confirm that the sensor can be applied to wastewater monitoring as it is . The monitor with a prototype of filtration system installed in a wastewater treatment plant is able to operate continuously for one month at least after the modification of filtration system and the optimization of operation conditions. Water Sci Technol, 2002, 45(4-5), 247 - 54 Dinitrogen oxide detection for process failure early warning systems; Burgess JE et al.; A number of experiments were conducted in order to establish whether the concentration of N2O in the off-gas from an activated sludge pilot plant could be used as a indicator for monitoring the nitrification process and as an early indication of ammonia appearing in the plant effluent . A strong correlation was found between ammonia shock loads and the concentration of N20 in the off-gas from the aeration tank for ammonia shock loads and dissolved oxygen depletion . When subjecting the experimental setup to doses of a nitrification inhibitor (allylthiourea) a similar pattern was seen with a correlation between nitrite build up in the aeration tank and concentration increase of N2O in the off-gas from the aeration tank . The results from this work suggest the concentration and the changes in the concentration of N2O in the exhaust gas from a nitrifying process may be a useful parameter for monitoring nitrifying activated sludge processes. Biochemistry, 2002 Apr 9, 41(14), 4603 - 11 Spectroscopic characterization of the NO adduct of hydroxylamine oxidoreductase; Hendrich MP et al.; Hydroxylamine oxidoreductase (HAO) from the autotrophic nitrifying bacterium Nitrosomonas europaea catalyzes the oxidation of NH2OH to NO2- . The enzyme contains eight hemes per subunit which participate in catalysis and electron transport . NO is found to bind to the enzyme and inhibit electron flow to the acceptor protein, cytochrome c554 . NO is found to oxidize either partially or fully reduced HAO, but NO will not reduce ferric HAO . Since NO can be reduced but not oxidized to product by HAO, NO is not considered to be a long-lived intermediate in the catalytic mechanism . Substrate oxidation occurs in the presence of bound NO or cyanide, suggesting a second interaction site for substrate with HAO and providing a means for recovery of the NO-inhibited form of the enzyme . Upon addition of NO to oxidized HAO, the integer-spin EPR signal from the active site vanishes, an IR band from NO appears at 1920 cm(-1), and a diamagnetic quadrupole iron doublet appears in Mossbauer spectroscopy with delta = 0.06 mm/s and DeltaEq = 2.1 mm/s . The NO stretching frequency and Mossbauer parameters are characteristic of an {FeNO}6 heme complex . New Mossbauer data on ferric myoglobin-NO are also presented for comparison . The results indicate that NO binds to heme P460 and that the loss of the integer-spin EPR signal is due to the conversion of heme P460 to a diamagnetic S = 0 state and concomitant loss of magnetic interaction with neighboring heme 6 . In previous studies where the heme P460-heme 6 interaction was affected by substrate or cyanide binding, a signal attributable to heme 6 was not observable . In contrast, in this work, the NO-induced loss of the signal is accompanied by the appearance of a previously unobserved large g(max) (or HALS) low-spin EPR signal from heme 6. Environ Technol, 2002 Jan, 23(1), 73 - 84 The monitoring of a two step aerobic-anoxic process with separate biomass to enhance performance in the treatment of liquid industrial wastes; Battistoni P et al.; The paper presents the results of a one-year study of the performance of a full scale plant for the treatment of industrial liquid wastes adopting the alternate cycle process . The carbon and nitrogen removal performances were discussed according to the experimental measurements of maximum nitrification and denitrification rates . It was demonstrated that the nitrification process was the limiting step: it worked with a rate in the range 0.002 - 0.02 KgNH4-N kg(-1)VSS d(-) at 20 degrees C . This was because of inhibition phenomena due to the presence of both complex organic compounds and heavy metals which were not removed by the chemical-physical pre-treatment step . The denitrification process was characterized by a maximum rate ranging from 0.015 to 0.056 Kg NO3-N kg(-1)VSS d(-1) at 20 degrees C, according to the available amount of readily biodegradable COD in the treated wastes . The reliability of the aerobic-anoxic process was determined on the basis of the percentage of successful cycles compared with the performed ones . It was shown that the actual cycles ranged from 50 to 100% of the expected ones, while effective cycles were up to 84% in the first step and up to 60% in the second one . These were related to the carbon to nitrogen ratio . Even if at times the nitrogen and carbon removal yields were not satisfactory, the two step aerobic-anoxic process operated in the alternate cycle mode seems a successful solution for the treatment of liquid industrial wastes. Water Res, 2002 Mar, 36(5), 1297 - 305 Calorimetry: a tool for assessing microbial activity under aerobic and anoxic conditions; Aulenta F et al.; For many years, calorimetric measurements have been used for understanding, modelling, controlling, and optimising chemical reactions . Calorimetry could be as well utilised to investigate biological processes, which however, involve very small amount of heat and therefore require very sensitive instruments . For this purpose, a Mettler Toledo RCI (Reaction calorimeter) was modified, changing both hardware and software, increasing its resolution up to 5 10m W/l . Such sensitivity allows the monitoring of aerobic and anoxic processes . This paper points out the excellent agreement between calorimetric and respirometric data, obtained simultaneously under aerobic conditions using activated sludge from a lab-scale scale reactor . Heat production rate can be directly converted in oxygen uptake rate by means of a correlation factor, whose value is approximately the same for all aerobic respiratory metabolisms . Taking into account this factor, calorimetric data were introduced in a chemical oxygen demand based model and processed for the estimation of kinetic parameters of heterotrophic biomass . Aerobic heterotrophic, denitrifying, and autotrophic nitrifying activity were determined by specific calorimetric tests . The effect of potentially toxic or inhibitory substances on the activity of all microbial communities was as well pointed out in these measurements. Water Res, 2002 Mar, 36(5), 1262 - 74 A hydro-chemical study of a mountainous watershed: the Ganga, India; Jain CK; A hydro-chemical study has been carried out on a 37-km stretch of the River Ganga from Deoprayag to Rishikesh (India) during the period from April 1999 to March 2000 . The assessment of sediment and nutrient load has been considered to evaluate the current state of pollution through real time measurements . The values of pH and conductance are well within the limits prescribed for drinking water . The maximum suspended sediment concentrations of 1,405 and 2,002 mg/L were recorded at Deoprayag and Rishikesh, respectively, during the rainy season . A large amount of sediment and nutrient load is transported from the watershed during the rainy season . Concentrations of N(O3-)-N and N(H3-)-N at Deoprayag varied from 0.30 to 0.50 and 0.02 to 0.12 mg/L, respectively, depending on season . Examination of the results showed clearly that N(H3-)-N was generally low as compared to N03-N . Depending on the pH and temperature of soils, NH4+ and NO3- ions are produced in the watershed through ammonification and nitrification of organic matter and mobilized into rivers through run-off . Dissolved N and P from fertilizer application, sewage and non-point source run-off contribute significant quantities of these nutrients in river water . The nitrate and phosphate are transported from the cropland either by being adsorbed on to soil particles that are subsequently eroded, or dissolved in runoff water from agricultural land . The data generated through the study will be useful for development and management planning of the hilly watershed. Water Res, 2002 Mar, 36(5), 1181 - 92 Accuracy analysis of a respirometer for activated sludge dynamic modelling; Marsili-Libelli S et al.; The aim of the paper is to assess the experimental errors arising from the operation of a closed respirometer using autotrophic biomass . A closed, intermittent-flow device has been set-up for the measurement of oxygen uptake rate (OUR) and parameter calibration . After describing the device structure and operation, the factors affecting accuracy have been assessed . Inaccuracies may be caused by two groups of parameters: design parameters, including flow rate, volume, sampling time, numerical algorithm, sample injection and environmental parameters, concerning the physicochemical conditions of the experiment, such as unwanted oxygen transfer, pH, and the influence of sludge condition on "start-up" behaviour . It is shown to what extent each of them affects the final accuracy of the OUR measurement . In the second part of the paper, the respirometric data are used to calibrate a two-step nitrification model and their impact on the accuracy of the estimation of model parameters is assessed . Confidence limits are derived for the identifiable parameter combinations and the practical identifiability assessed with the aid of trajectory sensitivity analysis. Water Sci Technol, 2002, 45(3), 247 - 53 The impact of the controlled emptying of in-sewer storage on wastewater treatment plant performance; Jack AG et al.; The use of in-sewer storage is generally considered to be an effective means of minimising the effects of intermittent discharges into receiving watercourses during combined flows . Despite this, very little information is available about the consequential effects these flows may have on recipient wastewater treatment plant performance . Typical problems may include biomass washout (hydraulic), and reduced biological reactor performance due to dilute loading (biological) . A study is described where detailed analysis was carried out to ascertain the consequential effects of prolonged dilute loading on an activated sludge wastewater treatment plant in Perth, Scotland . Consideration was given to likely storage volumes which may have been utilised in the catchment to resolve local problems . A comprehensive analysis of resulting treatment plant performance was carried out for variations in flow and various wet weather loadings . It is concluded that storage may cause little or no benefit with respect to ammonia total emissions due to reduced treatment of dry weather flows subsequent to the prolonged combined loading period . This was exacerbated by the long regeneration times of nitrifying bacteria . However, an overall benefit with respect to BOD total emissions would always be expected, as appropriately sized storage would retain the first foul flush at the CSOs, thereby compensating the increased emissions from the downstream wastewater treatment plant. Gig Sanit, 2002 Jan-Feb, (1), 22 - 5 {Ecological and hygienic evaluation of microbiological process in the soil contaminated by anion surfactants and heavy metals}; Mudryi IV; Disorders in microbiocenosis and biological activity of different types of soil were studied in a laboratory model experiment and the survival of reference and pathogenic microorganisms exposed to sulfonol and lead was evaluated . The most sensitive tests for such studies are evaluation of the number of nitrifiable bacteria, nitrifying, proteolytical, dehydrogenase, and cellulase activities, and survival of Salmonella and lactose-positive Escherichia coli in soil. Arch Microbiol, 2002 Apr, 177(4), 279 - 89 Epub 2002 Jan 31. The ribulose-1,5-bisphosphate carboxylase/oxygenase gene cluster of Methylococcus capsulatus (Bath); Baxter NJ et al.; The genes encoding the ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from Methylococcus capsulatus (Bath) were localised to an 8.3-kb EcoRI fragment of the genome . Genes encoding the large subunit ( cbbL), small subunit ( cbbS) and putative regulatory gene ( cbbQ) were shown to be located on one cluster . Surprisingly, cbbO, a second putative regulatory gene, was not located in the remaining 1.2-kb downstream (3') of cbbQ . However, probing of the M . capsulatus (Bath) genome with cbbO from Nitrosomonas europaea demonstrated that a cbbO homologue was contained within a separate 3.0-kb EcoRI fragment . Instead of a cbbR ORF being located upstream (5') of cbbL, there was a moxR-like ORF that was transcribed in the opposite direction to cbbL . There were three additional ORFs within the large 8.3-kb EcoRI fragment: a pyrE-like ORF, an rnr-like ORF and an incomplete ORF with no sequence similarity to any known protein . Phylogenetic analysis of cbbL from M . capsulatus (Bath) placed it within clade A of the green-type Form 1 Rubisco . cbbL was expressed in M . capsulatus (Bath) when grown with methane as a sole carbon and energy source under both copper-replete and copper-limited conditions . M . capsulatus (Bath) was capable of autotrophic growth on solid medium but not in liquid medium . Preliminarily investigations suggested that other methanotrophs may also be capable of autotrophic growth . Rubisco genes were also identified, by PCR, in Methylococcus-like strains and Methylocaldum species; however, no Rubisco genes were found in Methylomicrobium album BG8, Methylomonas methanica S1, Methylomonas rubra, Methylosinus trichosporium OB3b or Methylocystis parvus OBBP. Syst Appl Microbiol, 2001 Dec, 24(4), 588 - 96 The CANON system (Completely Autotrophic Nitrogen-removal Over Nitrite) under ammonium limitation: interaction and competition between three groups of bacteria; Third KA et al.; The CANON system (Completely Autotrophic Nitrogen Removal Over Nitrite) can potentially remove ammonium from wastewater in a single, oxygen-limited treatment step . The usefulness of CANON as an industrial process will be determined by the ability of the system to recover from major disturbances in feed composition . The CANON process relies on the stable interaction between only two bacterial populations: Nitrosomonas-like aerobic and Planctomycete-like anaerobic ammonium oxidising bacteria . The effect of extended periods of ammonium limitation was investigated at the laboratory scale in two different reactor types (sequencing batch reactor and chemostat) . The lower limit of effective and stable nitrogen removal to dinitrogen gas in the CANON system was 0.1 kg N m(-3) day(-1) . At this loading rate, 92% of the total nitrogen was removed . After prolonged exposure (> 1 month) to influxes lower than this critical NH4+-influx, a third population of bacteria developed in the system and affected the CANON reaction stoichiometry, resulting in a temporary decrease in nitrogen removal from 92% to 57% . The third group of bacteria were identified by activity tests and qualititative FISH (Fluorescence In Situ Hybridisation) analysis to be nitrite-oxidising Nitrobacter and Nitrospira species . The changes caused by the NH4+-limitation were completely reversible, and the system re-established itself as soon as the ammonium limitation was removed . This study showed that CANON is a robust system for ammonium removal, enduring periods of up to one month of ammonium limitation without irreversible damage. Life Support Biosph Sci, 1998, 5(3), 353 - 6 Water purification system by using the biofilter for long-term experiment equipment with aquatic animals for the space station; Nakamura HK et al.; We have developed a water purification system that enables long-term experiment with aquatic animals for 90 days or more on the space station . We designed the system that combined a biofilter for ammonia removal (nitrification) with another for nitrate removal (denitrification) . The experiment with goldfish was for 90 days with an aquatic animals' examination device . The equipment consists of a fish tank, a filter module, pumps, and an artificial lung for gas exchange . The goldfish were kept in the tank without any water replacement throughout the experiment . When a filter module consists of adsorbents without bacteria, the concentration of the nitrite and ammonia begin to increase so that the goldfish die . On the contrary, neither ammonia nor nitrite accumulated throughout the experiment, and the concentration of T-N also maintained 30 ppm or less when the combined biofilter was used . Moreover, no fish died throughout the period . The water purification system with biofilter enabled us to examine the long-term life support testing . We also report a new denitrification (correction of dentrification) method for the life support system. Appl Environ Microbiol, 2002 Mar, 68(3), 1454 - 7 Nitrite as a stimulus for ammonia-starved Nitrosomonas europaea; Laanbroek HJ et al.; Ammonia-starved cells of Nitrosomonas europaea are able to preserve a high level of ammonia-oxidizing activity in the absence of ammonium . However, when the nitrite-oxidizing cells that form part of the natural nitrifying community do not keep pace with the ammonia-oxidizing cells, nitrite accumulates and may subsequently inhibit ammonia oxidation . The maintenance of a high ammonia-oxidizing capacity during starvation is then nullified . In this study we demonstrated that cells of N . europaea starved for ammonia were not sensitive to nitrite, either when they were starved in the presence of nitrite or when nitrite was supplied simultaneously with fresh ammonium . In the latter case, the initial ammonia-oxidizing activity of starved cells was stimulated at least fivefold. Appl Environ Microbiol, 2002 Mar, 68(3), 1132 - 6 The aquatic budding bacterium Blastobacter denitrificans is a nitrogen-fixing symbiont of Aeschynomene indica; van Berkum P et al.; Blastobacter spp . are freshwater bacteria that form rosette structures by cellular attachment to a common base . Comparative analyses of ribosomal 16S rRNA gene and internally transcribed spacer region sequences indicated that B . denitrificans is a member of the alpha-subdivision of Proteobacteria . Among the alpha-Proteobacteria, B . denitrificans was related to a cluster of genera, including Rhodopseudomonas palustris, Afipia felis, Nitrobacter hamburgensis, and Bradyrhizobium spp . Although the precise phylogenetic relationships among these genera could not be established with a high degree of confidence, the sequences of B . denitrificans and several bradyrhizobial isolates from nodules of Aeschynomene indica were almost identical . Bradyrhizobia are bacteria that form nitrogen-fixing symbioses with legumes, including soybeans (Glycine max) and members of the genus Aeschynomene . From symbiotic infectiveness tests we demonstrated that the type strain for B . denitrificans, IFAM 1005, was capable of forming an effective nitrogen-fixing symbiosis with A . indica . Not only do these results reveal a previously unknown ecological adaptation of a relatively obscure aquatic bacterium, but they also demonstrate how evidence gathered from molecular systematic analyses can sometimes provide clues for predicting ecological behavior. Huan Jing Ke Xue, 2001 Nov, 22(6), 66 - 71 {Characteristics of nitrogen and phosphorus pollution in the middle and small creeks, suburban Shanghai}; Hu X et al.; 1 . The middle and small creeks in suburban Shanghai were under heavy eutropic condition, with high loadings of nitrogen, phosphorus and organic pollutants . KN, TP and CODCr of the surface water of them were several times greater than the critical values of Types V, the worst level of water . 2 . Spatial variations of N and P pollution were observed, as the creeks in different places accepted different types and amounts of pollutants . Affected by domestic sewage, the creeks nearby residential areas were often heavily polluted by NH4+ and P . The creeks in agricultural fields were more easily polluted by NO3- than by NH4+ and phosphorus . The creeks nearby livestock farms often witnessed sudden soaring of NH4+ and P . 3 . N and P loadings of the creeks were also affected by the seasonal evolvement of ecological environment . With the increase of temperature and biomass, NH4+ and NO3- in the surface water were largely consumed and decreased as a result; while organic N and particle P increased as the enhancement of suspending biological particles . NO2- in the surface water increased with temperature as nitrifying bacteria became active . Total P and water soluble P also showed the trend of enhancement with the intensification of biological activities, however, they were also controlled by the condition of pH and DO in the water . 4 . At the height of the summer, the surface and bottom water of the creeks differed in N and P loadings . NH4+, soluble P and total reactive P in the bottom water were higher than those in the surface; while NO3- and NO2- in the surface were higher than those in the bottom . Such water-quality stratification inevitably resulted from the enhancement of phytoplankton in the surface water and intensified release of NH4+ and P from the sediments . In the autumn, as-the temperature decrease, such phenomenon declined gradually. Water Res, 2002 Feb, 36(4), 996 - 1006 A simple biofilm model of bacterial competition for attached surface; Tsuno H et al.; A simple biofilm model of competition in bacterial growth for an attached surface is developed . Competition for the attached surface is expressed with the crowded and detachment effects . The developed model is verified by comparing simulated results with data obtained in the experiments of batch culture of nitrifier and continuous treatment of actual sewage with biofilm reactor . This model can favorably simulate the growth competition between autotrophic and heterotrophic bacteria for the attached surface . Then some parameters for nitrification process are discussed with this model . It is clarified that the effective removal of organic matter before nitrification tank is required for effective nitrification in the biofilm reactor. Water Environ Res, 2001 Nov-Dec, 73(6), 721 - 31 Effect of chlorine demand on the ammonia breakpoint curve: model development, validation with nitrite, and application to municipal wastewater; Chen WL et al.; Chlorine added during wastewater disinfection may be consumed through reactions with chlorine-demanding chemical species . In this study, a mechanistically based kinetic model for chlorine demand in the presence of ammonia was developed and validated with laboratory studies on ammonia-nitrite systems, and then applied to breakpoint curves obtained with wastewater samples . The model is a modification of kinetic models for chlorine-ammonia systems to include hypochlorous acid-demand and monochloramine-demand reactions . The model accurately describes both laboratory-generated breakpoint curves with added nitrite and literature data . In a plant thought to be undergoing partial nitrification, breakpoint curves were consistent with high chlorine demand (i.e., small initial slopes and large doses to achieve the total chlorine maximum and breakpoint) . A simplified kinetic model was also developed . Chlorine demand calculated from the simplified model was similar to chlorine demand from plant data . The simplified model was used to generate operating guidelines to calculate chlorine doses needed to overcome demand from nitrite or other sources. Water Res, 2002 Feb, 36(3), 702 - 12 Aerobic granulation in a sequencing batch airlift reactor; Beun JJ et al.; Aerobic granular sludge was cultivated in an intensely mixed sequencing batch airlift reactor (SBAR) . A COD loading of 2.5 kg Acetate-COD/(m3 d) was applied . Granules developed in the reactor within one week after inoculation with suspended activated sludge from a conventional wastewater treatment plant . Selection of the dense granules from the biomass mixture occurs because of the differences in settling velocities between granules (fast settling biomass), and filaments and flocs (slow settling biomass) . At 'steady state' the granules had an average diameter of 2.5 mm, a biomass density of 60g VSS/I of granules, and a settling rate of > 10 m/h . The biomass consisted of both heterotrophic and nitrifying bacteria . The reactor was operated over a long period during which the granular sludge proved to remain stable . The performance of the intermittently fed SBAR was compared to that of the continuously fed biofilm airlift suspension reactor (BASR) . The most importance difference was that the density of the granules in the SBAR was much higher than the density of the biofilms in the BASR . It is discussed that this could be due to the fact that the SBAR is intermittently fed, while the BASR is continuously fed. Biochemistry, 2002 Feb 12, 41(6), 1703 - 9 Nitrosocyanin, a red cupredoxin-like protein from Nitrosomonas europaea; Arciero DM et al.; Nitrosocyanin (NC), a soluble, red Cu protein isolated from the ammonia-oxidizing autotrophic bacterium Nitrosomonas europaea, is shown to be a homo-oligomer of 12 kDa Cu-containing monomers . Oligonucleotides based on the amino acid sequence of the N-terminus and of the C-terminal tryptic peptide were used to sequence the gene by PCR . The translated protein sequence was significantly homologous with the mononuclear cupredoxins such as plastocyanin, azurin, or rusticyanin, the type 1 copper-binding region of nitrite reductase, and the binuclear CuA binding region of N(2)O reductase or cytochrome oxidase . The gene for NC contains a leader sequence indicating a periplasmic location . Optical bands for the red Cu center at 280, 390, 500, and 720 nm have extinction coefficients of 13.9, 7.0, 2.2, and 0.9 mM(-1), respectively . The reduction potential of NC (85 mV vs SHE) is much lower than those for known cupredoxins . Sequence alignments with homologous blue copper proteins suggested copper ligation by Cys95, His98, His103, and Glu60 . Ligation by these residues (and a water), a trimeric protein structure, and a cupredoxin beta-barrel fold have been established by X-ray crystallography of the protein {Lieberman, R . L., Arciero, D . M., Hooper, A . B., and Rosenzweig, A . C . (2001) Biochemistry 40, 5674-5681} . EPR spectra of the red copper center indicated a Cu(II) species with a g(parallel) of 2.25 and an A(parallel) of 13.8 mT (144 x 10(-4) cm(-1)), typical of Cu in a type 2 copper environment . NC is the first example of a type 2 copper center in a cupredoxin fold . The open coordination site and type 2 copper suggest a possible catalytic rather than electron transfer function. Water Res, 2002 Jan, 36(2), 501 - 9 Simultaneous P and N removal in a sequencing batch biofilm reactor: insights from reactor- and microscale investigations; Giesek A et al.; A sequencing batch biofilm reactor (SBBR) with well established enhanced biological phosphate removal (EBPR) was subjected to higher ammonium concentrations to stimulate and eventually implement simultaneous nitrification . Changes of activity and populations were investigated by a combination of online monitoring, microsensor measurements and fluorescence in situ hybridisation (FISH) of biofilm sections . Nitrification and nitrifying bacteria were always restricted to the periodically oxic biofilm surface . Both, activity and population size increased significantly with higher ammonium concentrations . Nitrification always showed a delay after the onset of aeration, most likely due to competition for oxygen by coexisting P accumulating and other heterotrophic bacteria during the initial aeration phase . This view is also supported by comparing oxygen penetration and oxygen uptake rates under low and high ammonium conditions . Therefore, simultaneous nitrification and phosphorus removal in a P removing SBBR appears to be only possible with a sufficiently long oxic period to ensure oxygen availability for nitrifiers. Water Res, 2002 Jan, 36(2), 469 - 81 Nitrifying and heterotrophic population dynamics in biofilm reactors: effects of hydraulic retention time and the presence of organic carbon; Nogueira R et al.; Two biofilm reactors operated with hydraulic retention times of 0.8 and 5.0 h were used to study the links between population dynamics and reactor operation performance during a shift in process operation from pure nitrification to combined nitrification and organic carbon removal . The ammonium and the organic carbon loads were identical for both reactors . The composition and dynamics of the microbial consortia were quantified by fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes combined with confocal laser scanning microscopy, and digital image analysis . In contrast to past research, after addition of acetate as organic carbon nitrification performance decreased more drastically in the reactor with longer hydraulic retention time . FISH analysis showed that this effect was caused by the unexpected formation of a heterotrophic microorganism layer on top of the nitrifying biofilm that limited nitrifiers oxygen supply . Our results demonstrate that extension of the hydraulic retention time might be insufficient to improve combined nitrification and organic carbon removal in biofilm reactors. Water Res, 2002 Jan, 36(2), 421 - 8 Enumeration of acetate-consuming bacteria by microautoradiography under oxygen and nitrate respiring conditions in activated sludge; Nielsen JL et al.; Microautoradiography was used to enumerate bacteria able to take up radiolabelled acetate in activated sludge using oxygen or nitrate as electron acceptors . In each of three wastewater treatment plants (WWTP) with nitrification and denitrification (N-removal), the number of bacteria consuming acetate under aerobic and anoxic conditions was identical in contrast to the acetate removal rates . The rates were clearly lower under anoxic conditions suggesting that the specific activity of the cells and not the number of active cells was reduced under anoxic conditions . The fraction of bacteria able to consume acetate varied in three WWTPs between 47% and 93% of the total number of bacteria as determined by DAPI . In a WWTP without N-removal only 20% of the bacteria were able to consume acetate under aerobic conditions and very few of these were able to do it under anoxic conditions . The cell specific acetate removal rates in all WWTPs were found to be 3.0-13.2 x 10(-15) mol cell(-1) h(-1) under aerobic conditions and between 1.9 and 9.1 x 10(-15) mol cell(-1) h(-1) under anoxic conditions. Water Res, 2002 Jan, 36(2), 413 - 20 Performance of a bioreactor with submerged membranes for aerobic treatment of municipal waste water; Rosenberger S et al.; Aerobic treatment of municipal waste water in a membrane bioreactor was studied for 535 d . Apart from sampling, sludge was retained completely by a submerged hollow fibre membrane with a pore-size of 0.2 microm . The pilot plant comprised an anoxic zone to enable denitrification . The maximum liquid hold-up of the plant was 3.9 m3 . In this study the reactor performance and the stability of the process and the membrane capacity were investigated . A stable flux of 181 m(-2)h(-1) could be realised with a mean transmembrane pressure difference of 0.3bar with air-bubbling and backflushing the membrane and cleaning it in place every two months for one or two hours . For about 140d, a flux of 271 m(-2)h(-1) was achieved, but cleaning became necessary more often . The hydraulic retention time (HRT) varied between 10.4 and 15.6h . Accordingly the volumetric loading rate was between 1.1 and 1.7kg CODm(-3)d(-1) . No inoculum was used . The mixed liquor suspended solids (MLSS) concentration gradually increased to 18-20g MLSSl(-1) . The feed to microorganism (F/M) ratio varied according to the operation conditions but decreased against a value of 0.07 kg COD kg(-1) MLSSd(-1) . Treatment performance was very stable and on a high level . The COD was reduced by 95% . Nitrification was complete and up to 82% of the total nitrogen could be denitrified. Water Res, 2002 Feb, 36(3), 793 - 8 Hydrogen peroxide (H2O2) as a source of dissolved oxygen in COD-degradation respirometric experiments; Tusseau-Vuillemin MH et al.; Two different re-oxygenation techniques (aeration and hydrogen peroxide addition) were compared in respirometric experiments . As similar results were obtained in both cases, it was concluded that the addition of hydrogen peroxide does not modify the oxygen uptake rate of the biomass, under either endogenous or feeding conditions . It was hypothesized that under those experimental conditions (inhibition of nitrification with ATU), hydrogen peroxide alters neither the biomass metabolism nor the biodegradability of the tested substrates . The oxygen uptake rates obtained with the aeration system were often more scattered due to the adhesion of fine bubbles after the switch off of the aeration . Moreover, the transfer rate of oxygen to the solution is faster in the case of hydrogen peroxide addition. Water Res, 2002 Feb, 36(3), 722 - 32 Determination of the bacterial processes which are sources of nitrous oxide production in marine samples; Bonin P et al.; Partial denitrification and the initial step of nitrification are the main biological processes which produce nitrous oxide . In order to determine the contribution that these processes have in nitrous oxide production, the efficiency of different inhibitors on nitrifying activity has been tested, and the effect on denitrifying activity has been investigated, using culture strains and natural marine samples . A good nitrification inhibitor should not affect denitrification . A low partial pressure of C2H2 provided the best conditions, inhibiting 75%, Nitrosococcus oceanus (culture sample) and 100% (natural sample) of the nitrifying activity and having only a small inhibitory effect (12%) on denitrifying activity . These conditions have been applied on samples from the dilution plume of the Rhjne River, an area characterized as a source of nitrous oxide . Using these inhibitors, it has been shown that in this area, incomplete denitrification is the main process producing nitrous oxide in the surface layers at the mouth of the river and in the bottom nepheloid layer, whereas in the marine surface layer the dominant process is nitrification. Biodegradation, 2001, 12(4), 225 - 34 Effects of olive mill wastewater addition in composting of agroindustrial and urban wastes; Paredes C et al.; In order to study the suitability of olive mill wastewater (OMW) for composting, this liquid waste was added to two different mixtures of agroindustrial and urban wastes and the composting process was compared with two other piles of similar composition, but without OMW . These four piles were studied in a pilot plant using the Rutgers static pile system . The addition of OMW produced a greater proportion of degradable organic matter or a higher degradation rate, higher electrical conductivity values, greater losses of total N and lower nitrification than in piles without OMW . Its addition also restricted the increase of the cation exchange capacity and provoked the appearance of phytotoxicity or a longer persistence of phytotoxicity . However, in general, all the composts showed increases in the cation exchange capacity, the percentage of humic acid-like carbon, the polymerisation ratio of these humic substances (which revealed that the organic matter had been humified during composting) and the germination index, the latter indicating the reduction of phytotoxicity during the process. Syst Appl Microbiol, 2001 Nov, 24(3), 377 - 84 Fatty acid profiles of nitrite-oxidizing bacteria reflect their phylogenetic heterogeneity; Lipski A et al.; The fatty acid profiles of all described species of the nitrite-oxidizing genera Nitrobacter, Nitrococcus, Nitrospina and Nitrospira were analyzed . The four genera had distinct profiles, which can be used for the differentiation and allocation of new isolates to these genera . The genus Nitrobacter is characterized by vaccenic acid as the main compound with up to 92% of the fatty acids and the absence of hydroxy fatty acids . The genus Nitrococcus showed cis-9-hexadecenoic acid, hexadecanoic acid and vaccenic acid as main parts . Small amounts of 3-hydroxy-dodecanoic acid were detected . The genus Nitrospina possessed tetradecanoic acid and cis-9-hcxadecenoic acid as main compounds, also 3-hydroxy-hexadecanoic acid was detected for this genus . The genus Nitrospira showed a pattern with more variations among the two described species . These organisms are characterized by the cis-7 and cis-11-isomers of hexadecenoic acid . For Nitrospira moscoviensis a specific new fatty acid was found, which represented the major constituent in the fatty acid profiles of autotrophically grown cultures . It was identified as 11-methyl-hexadecanoic acid . Since this compound is not known for other bacterial taxa, it represents a potential lipid marker for the detection of Nitrospira moscoviensis relatives in enrichment cultures and environmental samples . A cluster analysis of the fatty acid profiles is in accordance with 16S rRNA sequence-based phylogeny of the nitrite-oxidizing bacteria. Antonie Van Leeuwenhoek, 2001 Sep, 79(3-4), 311 - 8 Gaseous NO2 as a regulator for ammonia oxidation of Nitrosomonas eutropha; Schmidt I et al.; Cells of Nitrosomonas eutropha strain N904 that were denitrifying under anoxic conditions with hydrogen as electron donor and nitrite as electron acceptor were unable to utilize ammonium (ammonia) as an energy source . The recovery of ammonia oxidation activity was dependent on the presence of NO2 . Anaerobic ammonia oxidation activity was observed in a helium atmosphere supplemented with 25 ppm NO2 after 20 h . Ammonia oxidation activity was detected after 2-3 days using an oxic atmosphere with 25 ppm NO2 . In contrast, ammonia consumption started after 8-9 days under oxic conditions without the addition of NO2; in this case, small amounts of NO and NO2 were detected and their concentrations increased with increasing ammonia oxidation activities . Hardly any ammonia oxidation was detected when nitrogen oxides were removed by intensive aeration . It would seem, therefore, that NO2 is the master regulatory signal for ammonia oxidation in Nitrosomonas eutropha . Anaerobic ammonia oxidation activity was inhibited by the addition of NO . This inhibition was partly compensated by either increasing the NO2 concentration or by using 2,3-dimercapto-1-propane-sulfonic acid as a NO binding substrate . DMPS was inhibitory to nitrification under oxic conditions, while increased amounts of NO or NO2 led to increased oxidation activities. Gig Sanit, 2001 Nov-Dec, (6), 64 - 6 {Sanitary standardization of 1-carbamoyl-3(5)-methylpyrazole, N-hydroxymethyl-3(5)-methylpyrazole and 4-amino-1,2,4-triazole in the water of reservoirs}; Buniatian IuA et al.; Since there is a problem in the sanitary protection of water reservoirs, nitrification inhibitors (NI), such as CMP, HMMP, ATG, were tested for their effects on the organoleptic properties and sanitary regimen of model water basins . The threshold concentrations of the inhibitors were found to be 0.49, 230, and 229 mg/l, respectively . The agents were classified as highly stable . They failed to affect on self-clearance . In chronic intoxication, the inactive doses were 0.128 mg/kg for CMP, 0.165 mg/kg for HMMP, and 1.36 mg/kg for ATG (1/1000 of LD50) . The maximum allowable water concentrations were 0.01, 0.01, and 0.1 mg/l, respectively (in the context of complex sanitary standardization) . The limiting hazard index was sanitarily toxicological (Hazard Class 3). Arch Microbiol, 2002 Feb, 177(2), 139 - 49 Epub 2001 Dec 06. Diversity of ammonia monooxygenase operon in autotrophic ammonia-oxidizing bacteria; Norton JM et al.; Autotrophic ammonia-oxidizing bacteria use the essential enzyme ammonia monooxygenase (AMO) to transform ammonia to hydroxylamine . The amo operon consists of at least three genes, amoC, amoA, and amoB; amoA encodes the subunit containing the putative enzyme active site . The use of the amo genes as functional markers for ammonia-oxidizing bacteria in environmental applications requires knowledge of the diversity of the amo operon on several levels: (1) the copy number of the operon in the genome, (2) the arrangement of the three genes in an individual operon, and (3) the primary sequence of the individual genes . We present a database of amo gene sequences for pure cultures of ammonia-oxidizing bacteria representing both the beta- and the gamma-subdivision of Proteobacteria in the following genera: Nitrosospira (6 strains), Nitrosomonas (5 strains) and Nitrosococcus (2 strains) . The amo operon was found in multiple (2-3) nearly identical copies in the beta-subdivision representatives but in single copies in the gamma-subdivision ammonia oxidizers . The analysis of the deduced amino acid sequence revealed strong conservation for all three Amo peptides in both primary and secondary structures . For the amoA gene within the beta-subdivision, nucleotide identity values are approximately 85% within the Nitrosomonas or the Nitrosospira groups, but approximately 75% when comparing between these groups . Conserved regions in amoA and amoC were identified and used as primer sites for PCR amplification of amo genes from pure cultures, enrichments and the soil environment . The intergenic region between amoC and amoA is variable in length and may be used to profile the community of ammonia-oxidizing bacteria in environmental samples . Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00203-001-0369-z. Chemosphere, 2002 Jan, 46(1), 11 - 9 Degradation of acid orange 7 in an aerobic biofilm; Coughlin MF et al.; A stable microbial biofilm community capable of completely mineralizing the azo dye acid orange 7 (AO7) was established in a laboratory scale rotating drum bioreactor (RDBR) using waste liquor from a sewage treatment plant . A broad range of environmental conditions including pH (5.8-8.2), nitrification (0.0-4.0 mM nitrite), and aeration (0.2-6.2 mg O2 l(-1)) were evaluated for their effects on the biodegradation of AO7 . Furthermore the biofilm maintained its biodegradative ability for over a year while the effects of these environmental conditions were evaluated . Reduction of the azo bond followed by degradation of the resulting aromatic amine appears to be the mechanism by which this dye is biodegraded . Complete loss of color, sulfanilic acid, and chemical oxygen demand (COD) indicate that AO7 is mineralized . To our knowledge this is the first reported occurrence of a sulfonated phenylazonaphthol dye being completely mineralized under aerobic conditions . Two bacterial strains (ICX and SAD4i) originally isolated from the RDBR were able to mineralize, in co-culture, up to 90% of added AO7 . During mineralization of AO7, strain ICX reduces the azo bond under aerobic conditions and consumes the resulting cleavage product 1-amino-2-naphthol . Strain SAD4i consumes the other cleavage product, sulfanilic acid . The ability of the RDBR biofilm to aerobically mineralize an azo dye without exogenous carbon and nitrogen sources suggests that this approach could be used to remediate industrial wastewater contaminated with spent dye. Water Sci Technol, 2001, 44(11-12), 237 - 44 Modelling nitrogen transformations in surface flow wastewater treatment wetlands in Sweden; Kallner S et al.; The purpose of this study was to describe and compare the fate of nitrogen (N) in two Swedish wastewater treatment wetlands in the cities of Oxelosund and Hassleholm . Specifically, we wanted to see if a fairly simple model, developed with regard to common data availability, could satisfactorily describe the concentration dynamics at the outlet from the wetlands . A first-order area-based model, with two alternative expressions for temperature dependence, was set up to describe three major processes: ammonification, nitrification and denitrification . The N concentration dynamics at the outlet of the Oxelosund wetland was not satisfactorily described, R2(NH4+-N) = 0.33 and R2(NO3(-)-N) = 0.10, while the modelled concentrations corresponded quite well with measured concentrations in the Hassleholm wetland, R2(NH4+-N) = 0.83 and R2(NO3(-)-N) = 0.58 . The NO3(-)-N concentrations, in both wetlands, could be slightly better described when introducing a temperature coefficient as an additional free parameter . The explained variances reported above were achieved when the model was calibrated individually for the two wetlands, when the resulting (optimised) reaction rate coefficients for each of the three processes were quite different between the two wetlands . To improve model performance, the rate equations may have to be changed to include factors in addition to concentration and temperature, such as dissolved oxygen and hydraulic efficiency . It may also be important to include other processes, such as plant uptake/decay and ammonia volatilisation. Water Sci Technol, 2001, 44(11-12), 19 - 25 State of the art for animal wastewater treatment in constructed wetlands; Hunt PG et al.; Although confined animal production generates enormous per-unit-area quantities of waste, wastewater from dairy and swine operations has been successfully treated in constructed wetlands . However, solids removal prior to wetland treatment is essential for long-term functionality . Plants are an integral part of wetlands; cattails and bulrushes are commonly used in constructed wetlands for nutrient uptake, surface area, and oxygen transport to sediment . Improved oxidation and nitrification may also be obtained by the use of the open water of marsh-pond-marsh designed wetlands . Wetlands normally have sufficient denitrifying population to produce enzymes, carbon to provide microbial energy, and anaerobic conditions to promote denitrification . However, the anaerobic conditions of wetland sediments limit the rate of nitrification . Thus, denitrification of animal wastewaters in wetlands is generally nitrate-limited . Wetlands are also helpful in reducing pathogen microorganisms . On the other hand, phosphorus removal is somewhat limited by the anaerobic conditions of wetlands . Therefore, when very high mass removals of nitrogen and phosphorus are required, pre- or in-wetland procedures that promote oxidation are needed to increase treatment efficiency . Such procedures offer potential for enhanced constructed wetland treatment of animal wastewater. Water Sci Technol, 2001, 44(11-12), 157 - 62 Distribution of ammonium-N in the water-soil interface of a surface-flow constructed wetland for swine wastewater treatment; Szogi AA et al.; Most livestock wastewaters treated in constructed wetlands are typically rich in ammonium N . The objective of this study was to evaluate the soil-water ammonium distribution and the diffusive flux through the soil-water interface . Wetland system 1 (WS1) was planted to rush and bulrushes, and wetland system 2 (WS2) was planted to bur-reed and cattails . Nitrogen was applied at a rate of 2.5 g m(-2) d(-1) . Interstitial soil water was sampled at 9, 24, 50, and 70 m from the inlet . In both wetlands, we found that NH4+ diffusion gradient and N losses were highest in the wetland system with lowest water depth . From other studies, we knew that shallower depths may have promoted a more effective interfacing of nitrifying and denitrifying environments . In turn, this N reduction in the water column may be the reason for steady NH4+-N upward diffusion fluxes . The assumed mechanism for N removal has been nitrification and denitrification but ammonia volatilization could also have occurred . Although diffusion may explain a significant portion of the material transport between the soil-water interface, the large differences in concentrations between outlet and inlet need further explanation. Water Sci Technol, 2001, 44(11-12), 137 - 42 Nitrogen removal in a combined system: vertical vegetated bed over horizontal flow sand bed; Kantawanichkul S et al.; Pig farm wastewater creates various problems in many areas throughout Thailand . Constructed wetland systems are an appropriate, low cost treatment option for tropical countries such as Thailand . In this study, a combined system (a vertical flow bed planted with Cyperus flabelliformis over a horizontal flow sand bed without plants) was used to treat settled pig farm wastewater . This system is suitable for using in farms where land is limited . The average COD and nitrogen loading rate of the vegetated vertical flow bed were 105 g/m2 x d and 11 g/m2 x d respectively . The wastewater was fed intermittently at intervals of 4 hours with a hydraulic loading rate of 3.7 cm/d . The recirculation of the effluent increased total nitrogen (TN) removal efficiency from 71% to 85% . The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal efficiencies were 95% and 98% . Nitrification was significant in vertical flow Cyperus bed, and the concentration of nitrate increased by a factor of 140 . The horizontal flow sand bed enhanced COD removal and nitrate reduction was 60% . Plant uptake of nitrogen was 1.1 g N/m2 x d or dry biomass production was 2.8 kg/m2 over 100 days. Bioresour Technol, 2002 Feb, 81(3), 225 - 31 The effect of kaolin particles on the behavior of nitrifying activated sludge units; Campos JL et al.; The effects of the addition of powered particles of kaolin to nitrifying activated sludge systems were studied . Kaolin was added to a nitrifying activated sludge reactor, during the operational phase, to observe the effects of this clay on reactor performance . The results were compared to those obtained from a similar unit operated without kaolin . The settling properties of the sludges from both units were similar (sludge volume index (SVI) of 14.5 ml/g VSS; zone settling velocity (ZSV) of 7.5 m/h), but the specific nitrifying activities of ammonia and nitrite oxidizing processes were enhanced up to 75% and 50%, respectively, when kaolin was added . The mechanism of action of kaolin was not clear . Additional ammonia, nitrite and nitrate adsorption tests showed that these compounds were not adsorbed by kaolin . This demonstrated that no beneficial effect was caused by adsorption of either substrates or products . Short-term activity tests also showed that the stimulating effects of kaolin on specific activity were not immediate . The effects of kaolin when nitrifying units were operated under unfavorable conditions were also evaluated: In a second set of experiments, a nitrifying unit was operated with low levels of dissolved oxygen (DO), with and without kaolin . The presence of kaolin exerted practically no effect on ammonia oxidation but nitrite oxidation slightly diminished . In a third set of experiments, a nitrifying unit was subjected to pH shocks (9, 10 and 11) over 3 h with pH then restored to 7.8 . A pH shock of 11 caused a decrease of 60% in nitrifying activity for 12 days . When kaolin was added to this unit the efficiency of the system was completely restored in 4 days . Therefore, kaolin might be useful to restore damaged units. Water Sci Technol, 2001, 44(10), 157 - 62 Increasing the fertilizer value of palm oil mill sludge: bioaugmentation in nitrification; Onyia CO et al.; Malaysia is essentially an agricultural country and her major polluting effluents have been from agro-based industries of which palm oil and rubber industries together contribute about 80% of the industrial pollution . Palm oil sludge, commonly referred to, as palm oil mill effluent (POME) is brown slurry composed of 4-5% solids, mainly organic, 0.5-1% residual oil, and about 95% water . The effluent also contains high concentrations of organic nitrogen . The technique for the treatment of POME is basically biological, consisting of pond systems, where the organic nitrogen is converted to ammonia, which is subsequently transformed to nitrate, in a process called nitrification . A 15-month monitoring program of a pond system (combined anaerobic, facultative, and aerobic ponds in series) confirmed studies by other authors and POME operators that nitrification in a pond system demands relatively long hydraulic retention time (HRT), which is not easily achieved, due to high production capacity of most factories . Bioaugmentation of POME with mixed culture of nitrifiers (ammonia and nitrite oxidizers) has been identified as an effective tool not only for enhancing nitrification of POME but also for improving quality of POME as source of liquid nitrogen fertilizer for use in the agricultural sector, especially in oil palm plantations . Nitrate is readily absorbable by most plants, although some plants are able to absorb nitrogen in the form of ammoniun . In this study, up to 60% reduction in HRT (or up to 20% reduction in potential land requirement) was achieved when bioaugmentation of POME was carried out with the aim of achieving full nitrification. J Environ Qual, 2001 Nov-Dec, 30(6), 1990 - 8 Biogeochemistry of a treeline watershed, northwestern Alaska; Stottlemyer R; Since 1950, mean annual temperatures in northwestern Alaska have increased . Change in forest floor and soil temperature or moisture could alter N mineralization rates, production of dissolved organic carbon (DOC) and organic nitrogen (DON), and their export to the aquatic ecosystem . In 1990, we began study of nutrient cycles in the 800-ha Asik watershed, located at treeline in the Noatak National Preserve, northwestern Alaska . This paper summarizes relationships between topographic aspect, soil temperature and moisture, inorganic and organic N pools, C pools, CO2 efflux, growing season net N mineralization rates, and stream water chemistry . Forest floor (O2) C/N ratios, C pools, temperature, and moisture were greater on south aspects . More rapid melt of the soil active layer (zone of annual freeze-thaw) and permafrost accounted for the higher moisture . The O2 C and N content were correlated with moisture, inorganic N pools, CO2 efflux, and inversely with temperature . Inorganic N pools were correlated with temperature and CO2 efflux . Net N mineralization rates were positive in early summer, and correlated with O2 moisture, temperature, and C and N pools . Net nitrification rates were inversely correlated with moisture, total C and N . The CO2 efflux increased with temperature and moisture, and was greater on south aspects . Stream ion concentrations declined and DOC increased with discharge . Stream inorganic nitrogen (DIN) output exceeded input by 70% . Alpine stream water nitrate (NO3-) and DOC concentrations indicated substantial contributions to the watershed DIN and DOC budgets. Cryo Letters, 2001 May-Jun, 22(3), 157 - 62 The open pulled straw vitrification of ovine GV-oocytes: positive effect of rapid cooling or rapid thawing or both? Isachenko V, Alabart JL, Nawroth F, Isachenko E, Vajta G, Folch J. Three protocols for the open pulled straw (OPS) vitrification of ovine GV-oocytes with slow cooling-rapid thawing, rapid cooling-slow thawing, and rapid cooling-rapid thawing were tested . The effect of ultra-rapid cooling in liquid nitrogen slush and superfine open pulled straws (SOPS) was also studied . Our results prove that both rapid cooling and rapid thawing are contributing in improved results achieved with the OPS technology . The use of liquid nitrogen slush is beneficial for ovine GV stage oocyte nitrification. Adv Biochem Eng Biotechnol, 2002, 75, 81 - 118 Microbial sensors on a respiratory basis for wastewater monitoring; Riedel K et al.; In respect of their rapidity, their online capabilities, and their moderate costs, biosensing systems generally offer an attractive alternative to the existing methods of water analysis . Additionally, one particular advantage of microbial biosensors is the ability to measure direct effects on living cells, e.g., their respiratory activity and its alteration caused by environmental pollutants . It is true that microbial sensors, often do not provide the optimum solution for the determination of individual analytes when compared to established physico-chemical analysis methods . However, these biosensing devices are predestined for the summary determination of environmentally relevant compounds and their complex effects, respectively . For this reason, microbial sensors allow an integral evaluation of the degree of environmental pollution including the interaction of various compounds . Moreover, in some cases specific metabolic pathways in microorganisms are used, resulting in the development of microbial sensors for the more selective analysis for those compounds or pollutants, which cannot be measured by simple enzyme reactions, e.g., the determination of aromatic compounds and heavy metals . This chapter gives an overview of microbiological biosensors on respiratory basis for the measurement of the following environmentally relevant compounds: inorganic N-compounds, heavy metals, organic xenobiotics and the estimation of sum parameters or so-called complex parameters such as BOD, ADOC, N-BOD, and the inhibition of nitrification. Appl Microbiol Biotechnol, 2001 Dec, 57(5-6), 799 - 802 Assay for determination of alpha-glucosidase and peptidase activity and location in a nitrifying trickling filter; Mustafa N et al.; Enzymatic alpha-glucosidase and peptidase activity in a nitrifying trickling filter (NTF) at the Rya wastewater treatment plant, Goteborg, Sweden, was investigated to evaluate whether these activities can be used as indicators of heterotrophic activity and polymer degradation . Samples of the biofilm were taken from the NTF and incubated in sterile filtered effluent water from the NTF with the addition of soluble starch, peptone, and ammonium chloride . In order to determine the distribution of enzyme activities, the alpha-glucosidase and peptidase activities were measured in the biofilm samples, in the filtered effluent water from the NTF and in the water phase in which the biofilm was incubated . Activities of both enzymes were found both in the effluent water from the NTF and in the biofilm . The enzyme activities were elevated in the samples when starch and peptone were present . In addition, there was a significant inhibition of ammonium oxidation in samples incubated with starch and peptone . Thus, the presence of starch, peptone and ammonium resulted in increased activity of heterotrophs, which lead to an inhibition of the nitrifiers, probably via competition for available oxygen. Appl Microbiol Biotechnol, 2001 Dec, 57(5-6), 791 - 8 Ammonia removal from prawn aquaculture water using immobilized nitrifying bacteria; Shan H et al.; Intensive prawn aquaculture in tropical regions is associated with high concentrations of total ammoniacal nitrogen (TAN) as a result of high rates of prawn excretion and feed loading . Excessive TAN can adversely effect productivity and result in adverse impacts on coastal waters . Cultures of indigenous nitrifying bacteria were enriched from intensive prawn aquaculture pond water using continuous and batch enrichment techniques . Cultures were capable of TAN removal over a wide range of initial TAN concentrations - up to 200 mg/l . Cultures were immobilized onto porous clay pellets to enhance cell density and applied to culture medium and TAN-augmented pond water under aerobic conditions to determine TAN removal proficiency . Immobilized cultures were able to achieve a high TAN removal proficiency in pond water--even at a low density of 0.1 pellet per liter . A concentration of less than 0.5 mg TAN/l could be maintained under a fed-batch condition of 3.2 mg TAN/l per day, after an initial 2-day lag phase . A simplified and effective culture enrichment process was developed for culture immobilization onto pellets using TAN-augmented pond water . Overall, pellet immobilization of indigenous nitrifying bacteria represents a potentially effective TAN control system for prawn aquaculture in low-cost, but intensive tropical prawn farms. Appl Environ Microbiol, 2002 Jan, 68(1), 245 - 53 Quantification of Nitrosomonas oligotropha-like ammonia-oxidizing bacteria and Nitrospira spp . from full-scale wastewater treatment plants by competitive PCR; Dionisi HM et al.; Utilizing the principle of competitive PCR, we developed two assays to enumerate Nitrosomonas oligotropha-like ammonia-oxidizing bacteria and nitrite-oxidizing bacteria belonging to the genus NITROSPIRA: The specificities of two primer sets, which were designed for two target regions, the amoA gene and Nitrospira 16S ribosomal DNA (rDNA), were verified by DNA sequencing . Both assays were optimized and applied to full-scale, activated sludge wastewater treatment plant (WWTP) samples . If it was assumed that there was an average of 3.6 copies of 16S rDNA per cell in the total population and two copies of the amoA gene per ammonia-oxidizing bacterial cell, the ammonia oxidizers examined represented 0.0033% +/- 0.0022% of the total bacterial population in a municipal WWTP . N . oligotropha-like ammonia-oxidizing bacteria were not detected in an industrial WWTP . If it was assumed that there was one copy of the 16S rDNA gene per nitrite-oxidizing bacterial cell, Nitrospira spp . represented 0.39% +/- 0.28% of the biosludge population in the municipal WWTP and 0.37% +/- 0.23% of the population in the industrial WWTP . The number of Nitrospira sp . cells in the municipal WWTP was more than 62 times greater than the number of N . oligotropha-like cells, based on a competitive PCR analysis . The results of this study extended our knowledge of the comparative compositions of nitrifying bacterial populations in wastewater treatment systems . Importantly, they also demonstrated that we were able to quantify these populations, which ultimately will be required for accurate prediction of process performance and stability for cost-effective design and operation of WWTPs. Appl Environ Microbiol, 2002 Jan, 68(1), 73 - 81 Ammonia- and nitrite-oxidizing bacterial communities in a pilot-scale chloraminated drinking water distribution system; Regan JM et al.; Nitrification in drinking water distribution systems is a common operational problem for many utilities that use chloramines for secondary disinfection . The diversity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in the distribution systems of a pilot-scale chloraminated drinking water treatment system was characterized using terminal restriction fragment length polymorphism (T-RFLP) analysis and 16S rRNA gene (ribosomal DNA {rDNA}) cloning and sequencing . For ammonia oxidizers, 16S rDNA-targeted T-RFLP indicated the presence of Nitrosomonas in each of the distribution systems, with a considerably smaller peak attributable to Nitrosospira-like AOB . Sequences of AOB amplification products aligned within the Nitrosomonas oligotropha cluster and were closely related to N . oligotropha and Nitrosomonas ureae . The nitrite-oxidizing communities were comprised primarily of Nitrospira, although Nitrobacter was detected in some samples . These results suggest a possible selection of AOB related to N . oligotropha and N . ureae in chloraminated systems and demonstrate the presence of NOB, indicating a biological mechanism for nitrite loss that contributes to a reduction in nitrite-associated chloramine decay. Appl Environ Microbiol, 2002 Jan, 68(1), 20 - 30 Grassland management regimens reduce small-scale heterogeneity and species diversity of beta-proteobacterial ammonia pxidizer populations; Webster G et al.; The impact of soil management practices on ammonia oxidizer diversity and spatial heterogeneity was determined in improved (addition of N fertilizer), unimproved (no additions), and semi-improved (intermediate management) grassland pastures at the Sourhope Research Station in Scotland . Ammonia oxidizer diversity within each grassland soil was assessed by PCR amplification of microbial community DNA with both ammonia oxidizer-specific, 16S rRNA gene (rDNA) and functional, amoA, gene primers . PCR products were analysed by denaturing gradient gel electrophoresis, phylogenetic analysis of partial 16S rDNA and amoA sequences, and hybridization with ammonia oxidizer-specific oligonucleotide probes . Ammonia oxidizer populations in unimproved soils were more diverse than those in improved soils and were dominated by organisms representing Nitrosospira clusters 1 and 3 and Nitrosomonas cluster 7 (closely related phylogenetically to Nitrosomonas europaea) . Improved soils were only dominated by Nitrosospira cluster 3 and Nitrosomonas cluster 7 . These differences were also reflected in functional gene (amoA) diversity, with amoA gene sequences of both Nitrosomonas and Nitrosospira species detected . Replicate 0.5-g samples of unimproved soil demonstrated significant spatial heterogeneity in 16S rDNA-defined ammonia oxidizer clusters, which was reflected in heterogeneity in ammonium concentration and pH . Heterogeneity in soil characteristics and ammonia oxidizer diversity were lower in improved soils . The results therefore demonstrate significant effects of soil management on diversity and heterogeneity of ammonia oxidizer populations that are related to similar changes in relevant soil characteristics. Huan Jing Ke Xue, 2001 Sep, 22(5), 41 - 4 {Anaerobic hydrolysis of terramycin crystallizing mother solution}; Ma W et al.; The terramycin crystallizing mother solution contained high organics and high nitrogen . There were many kinds of bioinhibition in it but not enough electronic donor . Anaerobic hydrolysis of terramycin crystallizing mother solution was completed with up anarobic sludge bed in order to improve the biodegradability of wastewater and electronic donor in it . The variations of pH, COD, NH4+, and SO4(2-) were monitored . The COD removal was in a narrow range between 10% and 16.4% even when the HRT of the reactor was changed from 1.5 h to 6 h . pH increased because of formation of NH3 and reduction of SO4(2-) . Most of SO4(2-) was reduced to S2- when the HRT was longer than 2 h . Batch experiments on hydrolyzed wastewater demonstrated that reaction rates of nitrification and denitrification increased by 90.9% and 45.2%, respectively. Huan Jing Ke Xue, 2001 Sep, 22(5), 105 - 7 {Autotrophic ammonium-removal of sludge liquor}; Yang H et al.; The autotrophic ammonium-removal process was realized in floating bed reactors with sludge liquor as substrate . Biofilm of autotrophic bacteria were formed on the surface of carriers in reactors . The main operation conditions of the reactors were as the following: T = 28 degrees C, pH = 8.0 and DO = 0.8-1.0 mg/L . The average surface load of two reactors in series was NH4(+)-N 3-4 g/(m2.d), and the general autotrophic ammonium-removal efficiency was about 70% . The Autotrophic ammonium-removal technology promises considerable savings in regard to the oxygen consumption and external organic carbon addition compared with the conventional nitrification-denitrification technology when it was used to treat ammonium-rich and unfavourable C/N ratio wastewater. Ying Yong Sheng Tai Xue Bao, 2000 Aug, 11(4), 577 - 81 {NO emission from winter wheat fields of rice-wheat rotation ecosystem in southeast China}; Zheng X et al.; Measurements of NO emission from the winter wheat field of rice-wheat rotation ecosystem in southeast China during the whole period of wheat growth show that a higher NO emission was observed in spring than in autumn, and almost no emission in winter could be detected . Temperature was the most important factor determining the seasonal variation pattern of NO emission . Although the N fertilization might enlarge NO emission by a factor of 5-7, it could not modify the seasonal variation pattern . During the period of relatively weak plant activity, the diurnal variation pattern, with the maximum emission at 9:00-14:00, was determined by temperature . When plants luxuriated, however, the competition of NH4+ by plant uptake and by microbial nitrification led to a night-peak variation pattern, in which, the maximum diurnal emission usually occurred during 18:00 and 4:00 of next day, and the minimum at 8:00-16:00. Ying Yong Sheng Tai Xue Bao, 2000 Feb, 11(1), 73 - 7 {Effect of modified ammonium bicarbonate on nitrification-denitrification process and NO and N2O emission}; Huang B et al.; Compared with ammonium bicarbonate(AB), the effect of modified ammonium bicarbonate (MAB) on nitrification and denitrification processes and NO and N2O emissions in a clay soil (C soil) and a loam soil (L soil) was studied in laboratory (25 degrees C and 50% WFPS) . The inhibition effect of DCD from MAB on nitrification was relatively small in C soil, but considerably great in L soil . Compared with AB, MAB extended 7 days and 33 days for retaining NH4+ . During 15 days, the NO emission from C soil and L soil respectively accounted for 0.60% and 1.06% of applied N under AB application (100 micrograms N.g-1), which were as 30 and 12 times as the N2O emission from corresponding soils . After applying MAB, the emission of NO from C soil and L soil decreased by 67% and 95%, and the emission of N2O decreased by 64% and 95%, respectively . After 39 days of aerobic incubation, then anaerobically flooded incubation with nitrate addition (200 micrograms KNO3-N.g-1) for 7 days, the total loss of denitrification in MAB in L soil was 50% less, and N2O emission was 113% more than in AB in same soil. Water Environ Res, 2001 Sep-Oct, 73(5), 543 - 57 Temperature effects in treatment wetlands; Kadlec RH et al.; Several biogeochemical processes that regulate the removal of nutrients in wetlands are affected by temperature, thus influencing the overall treatment efficiency . In this paper, the effects of temperature on carbon, nitrogen, and phosphorus cycling processes in treatment wetlands and their implications to water quality are discussed . Many environmental factors display annual cycles that mediate whole system performance . Water temperature is one of the important cyclic stimuli, but inlet flow rates and concentrations, and several features of the annual biogeochemical cycle, also can contribute to the observed patterns of nutrient and pollutant removal . Atmospheric influences, including rain, evapotranspiration, and water reaeration, also follow seasonal patterns . Processes regulating storages in wetlands are active throughout the year and can act as seasonal reservoirs of nutrients, carbon, and pollutants . Many individual wetland processes, such as microbially mediated reactions, are affected by temperature . Response was much greater to changes at the lower end of the temperature scale (< 15 degrees C) than at the optimal range (20 to 35 degrees C) . Processes regulating organic matter decomposition are affected by temperature . Similarly, all nitrogen cycling reactions (mineralization, nitrification, and denitrification) are affected by temperature . The temperature coefficient (theta) varied from 1.05 to 1.37 for carbon and nitrogen cycling processes during isolated conditions . Phosphorus sorption reactions are least affected by temperature, with theta values of 1.03 to 1.12 . Physical processes involved in the removal of particulate carbon, nitrogen, and phosphorus are not affected much by temperature . In contrast, observed wetland removals may have different temperature dependence . Design models are oversimplified because of limitations of data for calibration . The result of complex system behavior and the simple model is the need to interpret whole ecosystem data to determine temperature coefficients . Temperature seems to have minimal effect on biochemical oxygen demand (0.900 < theta < 1.015) and phosphorus (0.995 < theta < 1.020) removal, and more significant effect on nitrogen removal (0.988 < theta < 1.16) . In colder climates, there may be seasonal slowdown of treatment, which can decrease the overall treatment efficiency of constructed wetlands. Water Environ Res, 2001 Sep-Oct, 73(5), 526 - 33 Characterization of denitrification and nitrification in a step-feed alternating anoxic-oxic sequencing batch reactor; Lin YF et al.; This study was conducted to characterize the denitrification and nitrification in a bench-scale sequencing batch reactor operating with a three-stage, alternating anoxic-oxic sequence and step feed (SAOSBR) for treating synthetic wastewater . The results of long-term operation and dynamic studies showed that the SAOSBR increased the availability of organic matter in wastewater for exogenous denitrification in anoxic periods, and subsequently allowed nitrification to occur under a lower organic loading in oxic periods . Comparatively high kinetic rates of 1.2 to 6.6 mg nitrate/g mixed liquor suspended solids (MLSS) x h for denitrification and 1.0 to 2.8 mg nitrogen/g MLSS x h for nitrification were found in dynamic studies . With sufficient influent organics and alkalinity, complete denitrification and full nitrification could be achieved sequentially in the alternating anoxic and oxic periods, resulting in an average total nitrogen removal efficiency up to approximately 90% . Alkalinity recovery because of exogenous denitrification was experienced, and a minimum influent alkalinity to total Kjeldahl nitrogen (TKN) ratio of 2.4 was required to reach complete TKN removal . The pH value would be a better parameter other than oxidation-reduction potential or dissolved oxgyen to determine the completeness of nitrification and denitrification in the SAOSBR. Environ Toxicol Chem, 2001 Dec, 20(12), 2709 - 16 Toxicity of linear alkylbenzene sulfonates and nonylphenol in sludge-amended soil; Gejlsbjerg B et al.; The application of sewage sludge to agricultural land brings several chemicals to the soil ecosystem . Linear alkylbenzene sulfonates (LAS) and nonylphenol (NP) are frequently found in sludge at relatively high concentrations . The toxic effects of LAS and NP to two soil invertebrates (Folsomia candida and Enchytraeus albidus) and five different microbial processes (aerobic respiration, nitrification, denitrification, anaerobic CH4 production, and anaerobic CO2 production) were investigated in sludge-soil mixtures . Median lethal concentrations (LC50 values) and median effective concentrations (EC50 values) were quite similar and calculated to be in the range of 1,143 to 1,437 and 71 to 437 mg/kg (dry wt) for LAS and NP, respectively . The EC50 values for nitrification and CH4 production were 431 and 277 mg/kg, respectively, for LAS and 343 and 754 mg/kg, respectively, for NP . Aerobic respiration and denitrification were not inhibited at the tested concentrations . The results show that NP was more toxic than LAS to both F . candida and E . albidus, whereas LAS was more toxic than NP to the anaerobic CH4 production . The safety margins between the lowest 10% effective concentration (EC10) and the estimated environmental concentration were a factor of 11 for LAS and 510 for NP when the concentrations of the contaminants corresponded to the current Danish cutoff values of 1,300 mg/kg for LAS and 30 mg/kg for NP. Water Sci Technol, 2001, 44(9), 189 - 96 Simultaneous activated sludge wastewater treatment and odour control; Hardy P et al.; Lab-scale tests were used to determine the amount of H2S that can be treated using a range of different activated sludges . Static vessels were used to study the effects of different H2S concentrations (5, 25, 50 and 75 ppm) . The data indicated that odour control may be carried out using certain types of sludge, but sludge type, e.g . carbonaceous, nitrifying, with or without coagulant, affects removal efficiency . The presence of the biomass resulted in greater H2S removal than the use of wet scrubbing and the adverse effects on mixed liquor were negligible . A pilot plant was used to study the removal efficiencies of activated sludge diffusion using a typical wastewater treatment plant H2S concentration and investigated the effects that the diffusion of H2S had on the process performance . Results indicated that the levels of H2S produced by other unit processes on a wastewater treatment site (approximately 5 ppm) can be treated using activated sludge diffusion without compromising the performance of the wastewater treatment process . The only effects on the activated sludge plant observed were: (1) nitrification was interrupted briefly as H2S diffusion commenced and (2) the species' diversity in the sludge decreased. Int J Syst Evol Microbiol, 2001 Nov, 51(Pt 6), 2021 - 30 Detailed phylogeny of ammonia-oxidizing bacteria determined by rDNA sequences and DNA homology values; Aakra A et al.; A comparison of the phylogeny of 38 isolates of chemolithoautotrophic ammonia-oxidizing bacteria (AOB) based on 16S rRNA gene sequences, 16S-235 rDNA intergenic spacer region (ISR) sequences and species affiliations based on DNA homology values was performed . The organisms studied all belong to the beta-subclass of the Proteobacteria and included representatives of Nitrosomonas, Nitrosococcus and Nitrosospira . The similarity values of the 16S rDNA sequences were high, particularly within the Nitrosospira genus, and based on these sequences it is difficult to determine the phylogenetic position of some AOB . As an alternative and supplement to 16S rRNA gene sequencing, the ISR was sequenced and analysed phylogenetically . Due to considerably lower similarity values, the ISR-based phylogeny gives a better resolution than the phylogeny based on the functional 16S rRNA gene . Since the ISR-based phylogeny of AOB is highly consistent with the 16S rDNA based phylogeny, ISR sequencing appears as a suitable tool for resolving the detailed phylogeny of AOB . The phylogenetic position of two isolates of the former genus 'Nitrosolobus' (now included in the Nitrosospira genus) is not clear . These organisms are close relatives of the former Nitrosospira spp . and 'Nitrosovibrio' spp . (now Nitrosospira), but based on their marginal positions in the phylogenetic trees, DNA-DNA hybridization data and phenotypic characteristics, it is suggested that 'Nitrosolobus' should be a separate genus . DNA homology determination of 11 Nitrosospira isolates revealed two new species of Nitrosospira . The phylogeny of AOB reflected in the trees based on the rDNA sequences is consistent with the species affiliations of AOB by DNA homology values . This observation will probably be important for the interpretation of results from studies of natural diversity of AOB. J Environ Sci Health B, 2001 Nov, 36(6), 775 - 82 Differential effects of the herbicides bensulfuron and cinosulfuron on soil microorganisms; Gigliotti C et al.; Bensulfuron toxicity on soil microbes was evaluated by the methods used in a previous study on cinosulfuron; the effects of the two sulfonylureas were compared . Cinosulfuron and bensulfuron, at the normal field application rate and 100 times higher, had no effect on the total number of bacteria and nitrifiers, or on the respiration activity in the soil, but they did decrease the nitrification activity . In vitro toxicity tests carried out on representative soil microbial strains using bensulfuron at 50 mg l(-1) showed some inhibition of three of the 17 bacterial strains and strong inhibition of almost all the 12 fungal strains; cinosulfuron had had no effect on any of these strains in the previous study . It is concluded that, compared with cinosulfuron, bensulfuron is potentially more toxic on soil heterotrophic microorganisms, but only at very high concentrations that are nearly impossible to reach with the usual agricultural use of the herbicides . However, autotrophic nitrifiers were more sensitive to both sulfonylureas than the other microorganisms. Biotechnol Bioeng, 2002 Feb 5, 77(3), 266 - 77 Sensitivity analysis of a biofilm model describing a one-stage completely autotrophic nitrogen removal (CANON) process; Hao X et al.; A mathematical model for nitrification and anaerobic ammonium oxidation (ANAMMOX) processes in a single biofilm reactor (CANON) was developed . This model describes completely autotrophic conversion of ammonium to dinitrogen gas . Aerobic ammonium and nitrite oxidation were modeled together with ANAMMOX . The sensitivity of kinetic constants and biofilm and process parameters to the process performance was evaluated, and the total effluent concentrations were, in general, found to be insensitive to affinity constants . Increasing the amount of biomass by either increasing biofilm thickness and density or decreasing porosity had no significant influence on the total effluent concentrations, provided that a minimum total biomass was present in the reactor . The ANAMMOX process always occurred in the depth of the biofilm provided that the oxygen concentration was limiting . The optimal dissolved oxygen concentration level at which the maximum nitrogen removal occurred is related to a certain ammonium surface load on the biofilm . An ammonium surface load of 2 g N/m2 . d, associated with a dissolved oxygen concentration level of 1.3 g O2/m3 in the bulk liquid and with a minimum biofilm depth of 1 mm seems a proper design condition for the one-stage ammonium removal process . Under this condition, the ammonium removal efficiency is 94% (82% for the total nitrogen removal efficiency) (30 degrees C) . Better ammonium removal could be achieved with an increase in the dissolved oxygen concentration level, but this would strongly limit the ANAMMOX process and decrease total nitrogen removal . It can be concluded that a one-stage process is probably not optimal if a good nitrogen effluent is required . A two-stage process like the combined SHARON and ANAMMOX process would be advised for complete nitrogen removal . J Bacteriol, 2002 Jan, 184(2), 468 - 78 Phylogeny and functional expression of ribulose 1,5-bisphosphate carboxylase/oxygenase from the autotrophic ammonia-oxidizing bacterium Nitrosospira sp . isolate 40KI; Utaker JB et al.; The autotrophic ammonia-oxidizing bacteria (AOB), which play an important role in the global nitrogen cycle, assimilate CO(2) by using ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) . Here we describe the first detailed study of RubisCO (cbb) genes and proteins from the AOB . The cbbLS genes from Nitrosospira sp . isolate 40KI were cloned and sequenced . Partial sequences of the RubisCO large subunit (CbbL) from 13 other AOB belonging to the beta and gamma subgroups of the class Proteobacteria are also presented . All except one of the beta-subgroup AOB possessed a red-like type I RubisCO with high sequence similarity to the Ralstonia eutropha enzyme . All of these new red-like RubisCOs had a unique six-amino-acid insert in CbbL . Two of the AOB, Nitrosococcus halophilus Nc4 and Nitrosomonas europaea Nm50, had a green-like RubisCO . With one exception, the phylogeny of the AOB CbbL was very similar to that of the 16S rRNA gene . The presence of a green-like RubisCO in N . europaea was surprising, as all of the other beta-subgroup AOB had red-like RubisCOs . The green-like enzyme of N . europaea Nm50 was probably acquired by horizontal gene transfer . Functional expression of Nitrosospira sp . isolate 40KI RubisCO in the chemoautotrophic host R . eutropha was demonstrated . Use of an expression vector harboring the R . eutropha cbb control region allowed regulated expression of Nitrosospira sp . isolate 40KI RubisCO in an R . eutropha cbb deletion strain . The Nitrosospira RubisCO supported autotrophic growth of R . eutropha with a doubling time of 4.6 h . This expression system may allow further functional analysis of AOB cbb genes. Biotechnol Bioeng, 2001 Dec, 76(4), 361 - 75 Analysis of biological wastewater treatment processes using multicomponent gas phase mass balancing; Gapes D et al.; A reactor system using off-gas analysis was developed for analyzing wastewater treatment process reactions . Using a mass spectrometer for the gas analysis provides the ability to simultaneously measure several gas components (such as oxygen, nitrogen, carbon dioxide, and argon) . One of the benefits of the reactor design was the precise control of the dissolved oxygen concentration, uncoupled from the system turbulence, which was controlled via a gas recycle loop . This feature allowed control of the turbulence within the reactor without any need for mechanical stirring . Using oxygen as the test gas, the reactor was shown to perform well in the measurement of oxygen uptake rate of nitrifying activated sludge . The oxygen uptake rate calculations were made using a simple calibration method developed for the reactor system . The reactor was able to provide precise and accurate results for this test case . Furthermore, the system was capable of measuring under dynamic process conditions, as well as when the process rates were constant (steady state) . Curr Microbiol, 2002 Jan, 44(1), 56 - 60 Chemolithoautotrophic nitrifiers in the phyllosphere of a spruce ecosystem receiving high atmospheric nitrogen input; Papen H et al.; Evidence is presented for the first time that chemolithoautotrophic ammonia oxidizers (CAO) and chemolithoautotrophic nitrite oxidizers (CNO) colonize in appreciable cell numbers the phyllosphere of spruce trees in a forest ecosystem exposed for decades to high levels of atmospheric nitrogen (The Hoglwald Forest, Bavaria, Germany) . The results strongly indicate that both, CAO and CNO are predominantly located inside the spruce needles, most likely within the stomatal cavity . These results are further supported by field experiments of NH3 uptake into twigs on intact spruce trees in the presence and absence of 10 Pa acetylene, an inhibitor of the ammonia monooxygenase of CAO . It is clearly demonstrated for the first time that in situ uptake of NH3 from the atmosphere into spruce needles exposed to high levels of atmospheric N is not catalyzed exclusively by the tree, but is the result of combined activities of both, the spruce trees and the chemolithoautotrophic nitrifiers colonizing the needles. Appl Environ Microbiol, 2001 Dec, 67(12), 5810 - 8 Cultivation-independent, semiautomatic determination of absolute bacterial cell numbers in environmental samples by fluorescence in situ hybridization; Daims H et al.; Fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes has found widespread application for analyzing the composition of microbial communities in complex environmental samples . Although bacteria can quickly be detected by FISH, a reliable method to determine absolute numbers of FISH-stained cells in aggregates or biofilms has, to our knowledge, never been published . In this study we developed a semiautomated protocol to measure the concentration of bacteria (in cells per volume) in environmental samples by a combination of FISH, confocal laser scanning microscopy, and digital image analysis . The quantification is based on an internal standard, which is introduced by spiking the samples with known amounts of Escherichia coli cells . This method was initially tested with artificial mixtures of bacterial cultures and subsequently used to determine the concentration of ammonia-oxidizing bacteria in a municipal nitrifying activated sludge . The total number of ammonia oxidizers was found to be 9.8 x 10(7) +/- 1.9 x 10(7) cells ml(-1) . Based on this value, the average in situ activity was calculated to be 2.3 fmol of ammonia converted to nitrite per ammonia oxidizer cell per h . This activity is within the previously determined range of activities measured with ammonia oxidizer pure cultures, demonstrating the utility of this quantification method for enumerating bacteria in samples in which cells are not homogeneously distributed. Appl Environ Microbiol, 2001 Dec, 67(12), 5791 - 800 Identification of bacteria responsible for ammonia oxidation in freshwater aquaria; Burrell PC et al.; Culture enrichments and culture-independent molecular methods were employed to identify and confirm the presence of novel ammonia-oxidizing bacteria (AOB) in nitrifying freshwater aquaria . Reactors were seeded with biomass from freshwater nitrifying systems and enriched for AOB under various conditions of ammonia concentration . Surveys of cloned rRNA genes from the enrichments revealed four major strains of AOB which were phylogenetically related to the Nitrosomonas marina cluster, the Nitrosospira cluster, or the Nitrosomonas europaea-Nitrosococcus mobilis cluster of the beta subdivision of the class Proteobacteria . Ammonia concentration in the reactors determined which AOB strain dominated in an enrichment . Oligonucleotide probes and PCR primer sets specific for the four AOB strains were developed and used to confirm the presence of the AOB strains in the enrichments . Enrichments of the AOB strains were added to newly established aquaria to determine their ability to accelerate the establishment of ammonia oxidation . Enrichments containing the Nitrosomonas marina-like AOB strain were most efficient at accelerating ammonia oxidation in newly established aquaria . Furthermore, if the Nitrosomonas marina-like AOB strain was present in the original enrichment, even one with other AOB, only the Nitrosomonas marina-like AOB strain was present in aquaria after nitrification was established . Nitrosomonas marina-like AOB were 2% or less of the cells detected by fluorescence in situ hybridization analysis in aquaria in which nitrification was well established. Microbiology, 2001 Nov, 147(Pt 11), 2897 - 912 Individual-based modelling of biofilms; Kreft JU et al.; Understanding the emergence of the complex organization of biofilms from the interactions of its parts, individual cells and their environment, is the aim of the individual-based modelling (IbM) approach . This IbM is version 2 of BacSim, a model of Escherichia coli colony growth, which was developed into a two-dimensional multi-substrate, multi-species model of nitrifying biofilms . It was compared with the established biomass-based model (BbM) of Picioreanu and others . Both models assume that biofilm growth is due to the processes of diffusion, reaction and growth (including biomass growth, division and spreading) . In the IbM, each bacterium was a spherical cell in continuous space and had variable growth parameters . Spreading of biomass occurred by shoving of cells to minimize overlap between cells . In the BbM, biomass was distributed in a discrete grid and each species had uniform growth parameters . Spreading of biomass occurred by cellular automata rules . In the IbM, the effect of random variation of growth parameters of individual bacteria was negligible in contrast to the E . coli colony model, because the heterogeneity of substrate concentrations in the biofilm was more important . The growth of a single cell into a clone, and therefore also the growth of the less abundant species, depended on the randomly chosen site of attachment, owing to the heterogeneity of substrate concentrations in the biofilm . The IbM agreed with the BbM regarding the overall growth of the biofilm, due to the same diffusion-reaction processes . However, the biofilm shape was different due to the different biomass spreading mechanisms . The IbM biofilm was more confluent and rounded due to the steady, deterministic and directionally unconstrained spreading of the bacteria . Since the biofilm shape is influenced by the spreading mechanism, it is partially independent of growth, which is driven by diffusion-reaction . Chance in initial attachment events modifies the biofilm shape and the growth of single cells because of the high heterogeneity of substrate concentrations in the biofilm, which again results from the interaction of diffusion-reaction with spreading . This stresses the primary importance of spreading and chance in addition to diffusion-reaction in the emergence of the complexity of the biofilm community. Environ Toxicol Chem, 2001 Nov, 20(11), 2469 - 74 Potential nitrification rate as a tool for screening toxicity in metal-contaminated soils; Smolders E et al.; A potential nitrification rate test (PNR) was used to identify metal toxicity in field-contaminated soils . The test was applied to metal salt-spiked soils, to 27 uncontaminated soils, and to 15 soils that are contaminated by former metal smelting activities . Four agricultural soils (pH 4.5-6.6) were spiked with various rates of CdCl2 (0-200 mg Cd/kg dry wt) or ZnCl2 (0-3,000 mg Cd/kg dry wt) and were equilibrated more than nine months prior to testing . The soil Zn EC50s of the PNR were between 150 and 350 mg Zn/kg dry weight . No continuous decrease of the nitrification with increasing Cd application was observed . The nitrification rate was reduced by between 50 and 80% at the highest Cd application in all soils . The PNRs of 27 uncontaminated soils varied widely (0-21 mg N/kg/d), but most of this variability is explained by soil pH (R2 = 0.77) . The PNRs of the 15 contaminated soils were 0 to 44% of the values predicted for an uncontaminated soil at corresponding pH . Significant toxicity in field-contaminated soils was identified if the PNR was outside the 95% prediction interval of the PNR for an uncontaminated soil at corresponding pH and was found in seven soils . These soils contain 160 to 34,000 mg Zn/kg dry weight and 5 to 104 mg Cd/kg dry weight and had a pH >5.7 . No toxicity could be detected below pH 5.6, where even a zero PNR value is within the 95% prediction interval of uncontaminated soils . It is concluded that the nitrification is sensitive to metal stress but that its power as a soil bioassay is low because of the high variability of the endpoint between uncontaminated soils . The ecological significance of the assay is discussed. Biochemistry, 2001 Nov 13, 40(45), 13483 - 90 Crystal structure of Nitrosomonas europaea cytochrome c peroxidase and the structural basis for ligand switching in bacterial di-heme peroxidases; Shimizu H et al.; The crystal structure of the fully oxidized di-heme peroxidase from Nitrosomonas europaea has been solved to a resolution of 1.80 A and compared to the closely related enzyme from Pseudomonas aeruginosa . Both enzymes catalyze the peroxide-dependent oxidation of a protein electron donor such as cytochrome c . Electrons enter the enzyme through the high-potential heme followed by electron transfer to the low-potential heme, the site of peroxide activation . Both enzymes form homodimers, each of which folds into two distinct heme domains . Each heme is held in place by thioether bonds between the heme vinyl groups and Cys residues . The high-potential heme in both enzymes has Met and His as axial heme ligands . In the Pseudomonas enzyme, the low-potential heme has two His residues as axial heme ligands {Fulop et al . (1995) Structure 3, 1225-1233} . Since the site of reaction with peroxide is the low-potential heme, then one His ligand must first dissociate . In sharp contrast, the low-potential heme in the Nitrosomonas enzyme already is in the "activated" state with only one His ligand and an open distal axial ligation position available for reaction with peroxide . A comparison between the two enzymes illustrates the range of conformational changes required to activate the Pseudomonas enzyme . This change involves a large motion of a loop containing the dissociable His ligand from the heme pocket to the molecular surface where it forms part of the dimer interface . Since the Nitrosomonas enzyme is in the active state, the structure provides some insights on residues involved in peroxide activation . Most importantly, a Glu residue situated near the peroxide binding site could possibly serve as an acid-base catalytic group required for cleavage of the peroxide O--O bond. Appl Environ Microbiol, 2001 Nov, 67(11), 5273 - 84 In situ characterization of Nitrospira-like nitrite-oxidizing bacteria active in wastewater treatment plants; Daims H et al.; Uncultivated Nitrospira-like bacteria in different biofilm and activated-sludge samples were investigated by cultivation-independent molecular approaches . Initially, the phylogenetic affiliation of Nitrospira-like bacteria in a nitrifying biofilm was determined by 16S rRNA gene sequence analysis . Subsequently, a phylogenetic consensus tree of the Nitrospira phylum including all publicly available sequences was constructed . This analysis revealed that the genus Nitrospira consists of at least four distinct sublineages . Based on these data, two 16S rRNA-directed oligonucleotide probes specific for the phylum and genus Nitrospira, respectively, were developed and evaluated for suitability for fluorescence in situ hybridization (FISH) . The probes were used to investigate the in situ architecture of cell aggregates of Nitrospira-like nitrite oxidizers in wastewater treatment plants by FISH, confocal laser scanning microscopy, and computer-aided three-dimensional visualization . Cavities and a network of cell-free channels inside the Nitrospira microcolonies were detected that were water permeable, as demonstrated by fluorescein staining . The uptake of different carbon sources by Nitrospira-like bacteria within their natural habitat under different incubation conditions was studied by combined FISH and microautoradiography . Under aerobic conditions, the Nitrospira-like bacteria in bioreactor samples took up inorganic carbon (as HCO(3)(-) or as CO(2)) and pyruvate but not acetate, butyrate, and propionate, suggesting that these bacteria can grow mixotrophically in the presence of pyruvate . In contrast, no uptake by the Nitrospira-like bacteria of any of the carbon sources tested was observed under anoxic or anaerobic conditions. Appl Environ Microbiol, 2001 Nov, 67(11), 5261 - 6 Direct detection by in situ PCR of the amoA gene in biofilm resulting from a nitrogen removal process; Hoshino T et al.; Ammonia oxidation is a rate-limiting step in the biological removal of nitrogen from wastewater . Analysis of microbial communities possessing the amoA gene, which is a small subunit of the gene encoding ammonia monooxygenase, is important for controlling nitrogen removal . In this study, the amoA gene present in Nitrosomonas europaea cells in a pure culture and biofilms in a nitrifying reactor was amplified by in situ PCR . In this procedure, fixed cells were permeabilized with lysozyme and subjected to seminested PCR with a digoxigenin-labeled primer . Then, the amplicon was detected with an alkaline phosphatase-labeled antidigoxigenin antibody and HNPP (2-hydroxy-3-naphthoic acid-2'-phenylanilide phosphate), which was combined with Fast Red TR, and with an Alexa Fluor 488-labeled antidigoxigenin antibody . The amoA gene in the biofilms was detected with an unavoidable nonspecific signal when the former method was used for detection . On the other hand, the amoA gene in the biofilms was detected without a nonspecific signal, and the cells possessing the amoA gene were clearly observed near the surface of the biofilm when Alexa Fluor 488-labeled antidigoxigenin antibody was used for detection . Although functional gene expression was not detected in this study, detection of cells in a biofilm based on their function was demonstrated. Appl Biochem Biotechnol, 2001 Jul, 95(1), 1 - 10 Effect of two broad-spectrum antibiotics on activity and stability of continuous nitrifying system; Campos JL et al.; The effects of two broad-spectrum antibiotics, chloramphenicol and oxytetracycline hydrochloride, on the microbial activity and biofilm stability of a mixed nitrifying culture were studied . These antibiotics are present in some wastewaters generated in cattle farms or pharmaceutical industries . A 1-L fermentor, in which nitrifiers grew both in suspension and in a biofilm, was used during the experiments . Chloramphenicol (10-250 mg/L) barely had any effect on biofilm stability and nitrification . Ammonia was fully oxidized to nitrate . However, oxytetracycline caused biofilm sloughing at concentrations of 10 mg/L, but nitrification was not inhibited at antibiotic concentrations up to 100 mg/L . When the concentration of oxytetracycline chlorohydrate was increased stepwise from 100 to 250 mg/L, nitrification was inhibited by 50% . The dissolved organic carbon measurements in both the influent and effluent showed that the antibiotics were neither mineralized by the mixed nitrifying culture nor accumulated in the system . Furthermore, the microbial tests did not reveal the presence of active antibiotics in the effluent . This fact indicates that both cloramphenicol and oxytetracycline were degraded by the nitrifying sludge but not mineralized. Appl Microbiol Biotechnol, 2001 Sep, 56(5-6), 820 - 5 Aerobic treatment of a concentrated urea wastewater with simultaneous stripping of ammonia; Rittstieg K et al.; An industrial wastewater containing a total Kjeldahl nitrogen (TKN) of 12.80 g l(-1) was treated in a continuously fed activated sludge reactor . The main contaminant was urea (21.52 g l(-1)), together with minor amounts of the nitrification inhibitor dicyandiamide (0.46 g l(-1)) and free ammonia (0.56 g l(-1)) . The wastewater was diluted 1:1 with water and treated under alkaline conditions (pH 9.4), enabling the simultaneous hydrolysis of urea and stripping of free ammonia in one aerobic reactor . Experiments were conducted to eliminate the remaining ammonia in a separate treatment unit by nitrification/denitrification . An adapted nitrifying bacterial population was isolated which was able to nitrify at a rate of 0.1 g nitrogen l(-1) day(-1) at a dicyandiamide concentration of 0.22 g l(-1) . However, this was found to be too slow for an industrial-scale operation . Therefore, separate stripping with air or steam after pH adjustment to > or =10.5 is proposed . The diluted wastewater was treated with a hydraulic retention time of 6 days, corresponding to a volumetric nitrogen loading rate of 1.1 g nitrogen l(-1) day(-1) with an overall TKN reduction of 78.0%. J Agric Food Chem, 2001 Oct, 49(10), 4726 - 31 Some furfural derivatives as nitrification inhibitors; Datta A et al.; Three series of furfural derivatives, namely N-O-furfural oxime ethers, furfural Schiff bases (furfurylidene anilines), and furfural chalcones, have been synthesized and evaluated for nitrification inhibition activity in laboratory incubation studies in typic Ustocrept soil . Furfural oxime ethers and furfural Schiff bases showed potential activity, but furfural chalcones were only mildly active . N-O-ethyl furfural oxime among the oxime ethers, and furfurylidine-4-chloroaniline among the furfural Schiff bases, performed the best . These two compounds showed more than 50% nitrification inhibition on the 45th day at 5% dose as compared to 73% inhibition by nitrapyrin . Activity of furfural oxime ethers decreased with an increase in carbon atoms in the N-O-alkyl side chain . Introduction of a chlorine atom in the phenyl ring of furfurylidene anilines increased the persistence of their activity . N-O-Ethyl furfural oxime and furfurylidine-4-chloroaniline coated urea performed at par with their application in solution form . Ethyl and N-O-isopropyl oxime, as well as chloro- and nitro- substituted Schiff bases, did not reveal any phytotoxicity (adverse effect on germination) on chickpea seeds (Cicer arietinum) even at the highest dose (40 ppm, soil basis). J Environ Sci Health B, 2001 Sep, 36(5), 581 - 95 Effects of butachlor on microbial populations and enzyme activities in paddy soil; Min H et al.; This paper reports the influences of the herbicide butachlor (n-butoxymethlchloro -2', 6'-diethylacetnilide) on microbial populations, respiration, nitrogen fixation and nitrification, and on the activities of dehydrogenase and hydrogen peroxidase in paddy soil . The results showed that the number of actinomycetes declined significantly after the application of butachlor at different concentrations ranging from 5.5 microg g(-1) to 22.0 microg g(-1) dried soil, while that of bacteria and fungi increased . Fungi were easily affected by butachlor compared to the bacteria . The growth of fungi was retarded by butachlor at higher concentrations . Butachlor however, stimulated the growth of anaerobic hydrolytic fermentative bacteria, sulfate-reducing bacteria (SRB) and denitrifying bacteria . The increased concentration of butachlor applied resulted in the higher number of SRB . Butachlor inhibited the growth of hydrogen-producing acetogenic bacteria . The effect of butachlor varied on methane-producing bacteria (MPB) at different concentrations . Butachlor at the concentration of 1.0 microg g(-1) dried soil or less than this concentration accelerated the growth of MPB, while at 22.0 microg g(-1) dried soil showed an inhibition . 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 microg g(-1) dried soil of butachlor . The hydrogen peroxidase could be stimulated by butachlor . The soil respiration was depressed during the 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 Toxicol, 2001 Oct, 16(5), 439 - 43 Effect of zinc and benzalkonium chloride on Nitrosomonas communis and potential nitrification in soil; Fruhling W et al.; A bacterial contact assay is described which uses a chemoautotrophic microorganism, Nitrosomonas communis (strain Nm2) to evaluate the biological effect of contaminated soils . The effects of two toxicants on the ammonium oxidation activity of the autochthonous microbial population in the soil are compared with inhibition of the same biological response in the new monospecies bioassay . Experiments were performed using soil samples dosed with organic and inorganic contaminants (benzalkonium chloride and zinc) to demonstrate the mode of operation and the sensitivity of the bioassay . The EC50 values of zinc and benzalkonium chloride were calculated to be 171 and 221 mg kg-1 soil, respectively . The toxic response provided by the bioassay can thus predict the effect of soil pollutants on the autochthonous nitrifying bacteria. J Environ Sci (China), 2001 Jul, 13(3), 376 - 9 Effects of cultivation on N2O emission and seasonal quantitative variations of related microbes in a temperate grassland soil; Huang B et al.; Laboratory and in situ experiments were done to investigate the influences of cultivation on temperate semi-arid grassland (for 17 years spring wheat planted once every two years without fertilisation) on soil N2O emission and quantitative variations of related soil microbes . In the laboratory (25 degrees C and soil moisture 18%), cultivation increased soil transformations of fertilizer nitrogen (100 micrograms N/g as NaNO3, urea, or as urea with dicyandiamide 1 microgram N/g) . The N2O emissions from the cultivated and uncultivated soils with or without nitrogen additions were relatively low, and mainly originated from the nitrification . The soil N2O emission due to cultivation decreased somewhat upon no fertilization or NaNO3 addition, but significantly upon urea addition . The role of dicyandiamide as nitrification inhibitor was only considerable in the cultivated soil, and had small influence on decreasing N2O emission in the two soils . The influence of cultivation on soil N2O emission was also reflected by the number variations of microbes related with soil nitrogen transformation in the two soils . Compared to the uncultivated grassland, in situ ammonifiers and denitrifiers in the cultivated grassland quantitatively averagely increased, and aerobic no-symbiotic azotobacters were quantitatively similar, leading to the continued decrease of organic matter content and the decrease of N2O emission from the cultivated grassland soil. J Environ Qual, 2001 Sep-Oct, 30(5), 1699 - 709 Leachate chemistry of field-weathered spent mushroom substrate; Guo M et al.; Passive leaching by rainfall and snowmelt is a popular method to treat piles of spent mushroom substrate (SMS) before its reuse . During this field weathering process, leachate percolates into the underlying soils . A field study was conducted to examine the chemistry of SMS leachate and effects of infiltration . Two SMS piles were deposited (90 and 150 cm in height) over a Typic Hapludult and weathered for 24 mo . Leachate was collected biweekly using passive capillary samplers . The SMS leachate contained high concentrations of dissolved organic carbon (DOC; 0.8-11.0 g L(-1)), dissolved organic nitrogen (DON; 0.1-2 g L(-1)), and inorganic salts . The pH, electrical conductivity, and acid neutralizing capacity were 6.6 to 9.0, 21 to 66 ds m(-1), and 10 to 75 mmolc L(-1), respectively . Inorganic chemistry of the leachate was dominated by K+, Cl-, and SO24- . Leachate DOC was predominantly low molecular weight (<1000 Da) organic acids . During 2 yr of weathering, the 90-cm SMS pile released (per cubic meter of SMS) 3.0 kg of DOC, 1.6 kg of dissolved N, and 26.6 kg of inorganic salts . The 150-cm pile released (per cubic meter of SMS) 2.8 kg of DOC, 0.7 kg of dissolved N, and 13.6 kg of inorganic salts . The 150 cm pile retained more water and exhibited lower net nitrification compared with the 90-cm pile . The top 90 cm of soil retained 20 to 89% of the leachate solutes . Weathering of SMS in piles of 90 cm depth or greater may adversely affect ground water quality. Water Sci Technol, 2001, 44(4), 79 - 82 Denitrification on the top of UASB reactors of rice wastewaters; Lopes LF et al.; Parboiled rice industry is one of main food industries in the south of Brazil . The main parts of the processing are the humidification and gelatinization of the grain . This procedure increases the productivity and nutritive and cooking values of the product . Some of these industries in the region utilize upflow anaerobic sludge blanket (UASB) reactors as a biological treatment for carbon removal . For nitrogen removal, the proposed system aims to eliminate an extra denitrification reactor, making this step in the top of the UASB, an anoxic zone of the reactor . Nitrification was performed in aerated mixed reactor of 3.6 L.A fraction of the NR was recycled in the top of UASB reactor above the sludge blanket . Recycled ratio varied from 0; 1:0.5; 1:1.0; to 1:1.5 . The maximum removal efficiency of NTK was 80% . The results confirm the viability of the proposed system for denitrification. Water Sci Technol, 2001, 44(4), 279 - 86 Nitrification-denitrification of UASB effluents highly loaded with nitrogen in an activated sludge reactor operated with short cycled aeration; Villaverde S et al.; A conventional activated sludge reactor operated with short cycled aeration was used for total nitrogen removal of UASB anaerobic reactor effluent containing nitrogen (up to 1,200 mg NKT/L) and organic matter (up to 2,000 mg COD/L) . Initially the reactor was fed with synthetic water to progressively introduce the UASB effluent . This favored the acclimation of the microorganisms to the real environment . The results obtained throughout this study showed that initially the tested technology is feasible and can report significant cuts on operation and maintenance when compared to conventional activated sludge processes . Total nitrogen removal up to 66% was attained treating the effluent of an UASB process designed for treating the wastewater of a potato starch factory . Total nitrogen removal capacities ranging between 0.1 and 0.58 kg of nitrogen per cubic metre per day are reported . Short-cycled aeration allowed for a more efficient use of the oxygen supply for nitrification and the organic carbon content present in the wastewater for denitrification . This operating protocol has demonstrated serious advantages in terms of operation costs and simplicity when total nitrogen removal is wanted . Most of the existing activated sludge processes, i.e . single continuous flow reactors, can be updated for total nitrogen removal essentially at no cost, the inversion (aeration control system) is rapidly returned as reduction in energy expenditure. Water Sci Technol, 2001, 44(4), 271 - 7 Evaluation of an anaerobic/aerobic system for carbon and nitrogen removal in slaughterhouse wastewater; Nunez LA et al.; In this work the performance of an anaerobic UASB reactor coupled with an activated sludge reactor for carbon and nitrogen removal in slaughterhouse wastewater is investigated . Periods with and without recirculation of aerobic effluent over 165 days are analysed . Working with a recirculation ratio of 2, removal efficiencies up to 90% and 65% are obtained for DQO and total nitrogen (TN), respectively . Higher recirculation ratios caused severe washout of active biomass in both reactors due to the high hydraulic loading rates applied . Denitrification in the UASB reactor was complete, with no nitrite accumulation and mainly to nitrogen gas . Significant decreases in COD removal efficiencies in the UASB reactor were observed at recirculation ratio of 2 . Sudden decreases in total nitrogen efficiencies were related to inhibition process of nitrifying microorganisms, especially at high recirculation ratios. Water Sci Technol, 2001, 44(4), 263 - 70 Removal of organic carbon, nitrogen and phosphorus in sequential batch reactors integrating the aerobic/anaerobic processes; Callado NH et al.; The performance of a bench-scale apparatus composed of two sequential batch reactors (SBR), forming an anaerobic/aerobic treatment system, was evaluated as to its potential use for biological removal of organic matter and nutrients . Both the reactors with 12.5 L of useful volume each were operated for the batch cycles of 12 hours receiving 8.0 L of substrate in each cycle . The first reactor (SBRAn) fed with synthetic substrate simulating domestic sewage was meant to remove the largest fraction of carbonic matter and to promote the substrate ammonification . The second reactor (SBRAe) was operated under alternating aerobic and anoxic conditions to establish conditions for achieving nitrification; denitrification and biological phosphate removal in the same batch cycle . Sodium acetate was used as an external carbon source for phosphate removal . Processes monitoring included the analyses of: COD, NTK-N, NH4(+)-N, NO2(-)-N, NO3(-)-N, PO4(3-)-P, alkalinity, volatile acids, pH, redox potential total, fixed and volatile solids . Under the operating conditions imposed, the system exhibited high performance in removing organic matter (COD), nitrogen and phosphorus, producing effluent with COD, NTK-N and PO4(3-)-P concentrations lower than 50.0 mg/L, 4.0 mg/L and 1.0 mg/L, respectively. Water Sci Technol, 2001, 44(4), 247 - 53 Domestic sewage treatment in a pilot system composed of UASB and SBR reactors; Torres P et al.; The results obtained from the operation of a treatment system composed of an anaerobic (up-flow sludge blanket-UASB) reactor followed by an aerobic (sequencing batch-SBR) reactor treating domestic sewage are presented and discussed . The pilot plant was monitored during 6 months, aiming to obtain performance data on organic matter, nitrogen and phosphate removal under different operating conditions . The UASB reactor was operated at a constant hydraulic detention time (0) of 6 h while the SBR performance was monitored in four different duration cycles (24, 12, 6 and 4 h) corresponding to aeration times (AT) of 22, 10, 4 and 2 h, respectively . COD and TSS overall removal efficiencies (Eo) up to 91% and 84%, respectively, were achieved independently on the aeration time applied to the SBR . In respect to nitrification and phosphate removal, AT was found to be a determining operating parameter . TKN removal of approximately 90% was achieved for AT equal to or higher than 10 h; complete nitrification occurred for AT higher than 4 h; significant phosphate removal (72%) occurred only at the AT of 2 h . It was not possible to achieve simultaneous efficient removal of nitrogen and phosphate, under the operating conditions imposed on the treatment system. Chemosphere, 2001 Oct, 45(1), 109 - 21 The fate of linear alcohol ethoxylates during activated sludge sewage treatment; Battersby NS et al.; Model continuous activated sludge (CAS) plants (Husmann units) were used to study the fate of two commercial, alcohol ethoxylate (AE) surfactants during aerobic sewage treatment . The surfactants were produced by the ethoxylation of an essentially linear C(12-15) alcohol (NEODOL 25) with an average of 7 (C(12-15)EO7) or 3 (C(12-15)EO3) moles of ethylene oxide (EO) . Recent analytical developments made it possible to measure levels of AE that included the free alcohol and EO1 oligomers across the CAS system, from the influent feed, on the activated sludge, through to the effluent . Measured concentrations of AE (as C(12-15)EO(0-20)) in the synthetic sewage feeds to the test CAS plants lay in the range 11-13 mg/l . During stable operation at 20 degrees C, an average of 5 microg/l AE were present in the C(12-15)EO7 CAS plant effluent, giving a removal (bioelimination) of >99.9% . When levels of AE on the sludge, and polyethylene glycols (PEGs--an expected biodegradation intermediate) in the effluent and on the sludge were also taken into account, biodegradation was considered to be responsible for >98.7% of the observed removal . During operation at a winter temperature (10 degrees C), an average of 26 microg/l AE were present in the C(12-15)EO7 CAS plant effluent, giving a removal of 99.8% . Biodegradation was estimated to be responsible for >97.2% of the observed removal . During operation at 20 degrees C, an average of 7 microg/l AE were present in the C(12-15)EO3 CAS plant effluent, giving a removal of >99.9% . No analysis for PEG was performed in this case but the low level of AE on the sludge (0.2 mg/g dry solids) suggested that biodegradation was responsible for most of the observed removal . Neither surfactant had any adverse effect on the sewage treatment efficiencies of the CAS plants in terms of dissolved organic carbon (DOC) removal, nitrification or biomass levels. Huan Jing Ke Xue, 2001 Jul, 22(4), 51 - 5 {The influence of ecological factors on simultaneous nitrification and denitrification in MBR}; Zou L et al.; The influence of dissolved oxygen(DO), C/N and pH on simultaneous nitrification and denitrification in the membrane bioreactor was studied . The experimental results showed that only under condition that each ecological factor was maintained relative steady, simultaneous nitrification and denitrification might proceed smoothly . When DO, C/N and pH of feed water was 1 mg/L, 30 and 7.2, the removal rate of COD, NH4+, and TN were 96%, 95% and 92% respectively. Huan Jing Ke Xue, 2001 Jul, 22(4), 11 - 5 {Effect of grazing on microbiological processes of N2O production in grassland soils}; Du R et al.; A laboratory incubation study on effect of grazing on microbiological processes of N2O production in Aneurolepidium chinese grassland soils by using the acetylene-inhibition method was firstly conducted and the seasonal variations of related bacteria groups and N2O fluxes were analyzed . Results suggested that grazing behavior altered the soil structure which were benefit to microbiological denitrification so that N2O emission from this steppe soil was reduced . It was the heterotrophic nitrification that is the key microbiological process for N2O production in the non-grazing and grazing semi-arid typical grassland soils in Inner Mongolia . The reasons why N2O flux from Inner Mongolia semi-arid typical grassland soils was lower were also explained in this paper. Water Environ Res, 2001 Mar-Apr, 73(2), 142 - 5 Pre-fermentation of a low-strength meat-processing wastewater in an upflow sludge blanket reactor; Ros M et al.; Pre-fermentation of low-strength wastewater from a meat processing facility (at 20 degrees C) was studied . A laboratory-scale upflow sludge blanket (USB) reactor was used for the experiments; 10 different operating conditions were tested with regard to the hydraulic residence time (HRT) . At HRTs from 0.4 to 2.4 hours, the USB reactor produced effluent with acetate chemical oxygen demand from 82 to 100 mg/L . At HRTs shorter than 0.4 hours and upflow velocities greater than 0.5 m/h, biomass washout was observed . At HRTs longer than 2.4 hours, acetate concentration in the effluent and acetate production efficiency decreased . The transformation of organic nitrogen to ammonia-nitrogen occurred simultaneously with acetate production . Minimal accumulation of biomass in the USB reactor was observed . Pre-fermentation of the low-strength industrial wastewater in the USB reactor could be beneficial for biological nitrogen removal . The produced acetate is directly available for denitrification and the transformed ammonia-nitrogen is directly available for nitrification in the subsequent wastewater treatment steps. Environ Technol, 2001 Aug, 22(8), 941 - 50 The source and abatement of nitrous oxide emissions produced from the aerobic treatment of pig slurry to remove surplus nitrogen; Pahl O et al.; The removal of surplus nitrogen from pig slurry can be necessary in order to avoid pollution such as nitrate leaching . However, the treatment itself can create significant pollution; up to 20% of the removed slurry nitrogen has been shown to be released as nitrous oxide (N2O), which contributes to global warming and the breakdown of the ozone in the stratosphere . Avoiding such emission requires conditions that encourage the complete conversion of the nitrogen to the environmentally safe di-nitrogen gas (N2), and a clear understanding of the underlying biochemistry; for example, whether the nitrous oxide is the bi-product of incomplete nitrification (chemical oxidation) or denitrification (chemical reduction) . The stable isotope of nitrogen ( N) was used in this investigation as a label . Results indicated a new route for substantial release of N2O: via nitrification (rather than denitrification), caused by a combination of high aeration levels and the presence of nitrification products . Sequential aeration, which leads to a cycling between nitrification and complete denitrification, was proposed as an abatement in view of this new mechanism . This process achieved 89% removal of ammoniacal nitrogen in laboratory scale treatment, with 94% of the nitrogen removed in the form of N2 . These findings suggest that the possibility of N2O emissions from nitrification be considered in the design of treatment schemes . Increased aeration would be the intuitive response to incomplete nitrification . However, the results of this study suggested that although this response can increase nitrogen removal, this may be as N2O rather than N2. Water Res, 2001 Oct, 35(15), 3625 - 34 Are meiofauna transient or resident in sand filters of marine aquariums? Parent S, Morin A, Gagno D. A paradoxical situation was found in the sand filters of a cold marine mesocosm: meiofaunal masses which were large enough to inhibit the mineralization and nitrification processes coexisted with nitrogen cycling bacteria . To test whether the copepod-dominated meiofauna were resident and actively feeding or transient and carried passively through the sand filters, residence times (RTs) were measured for various meiofaunal groups in a newly started filter and in a long established one . Most meiofauna colonized the newly started filter in less than 6 h, but their RTs were less than 24 h . In contrast, RTs were 147d for halacarids, 291 d for harpacticoid copepods and 1228d for nematodes in the long established filter . Mesocosm periphyton . which occupied a large fraction of the mesocosm surface area and was characterized by high meiofaunal densities, was probably the main source of meiofauna in the sand filters . Pool sediments, consisting of gravel or sand, were second to periphyton and contributed hydrozoans and mesopsammic species to the filters . The small copepod Pseudonychocamptus proximus progressively replaced the large Tisbe furcata in sand filters during the fall of 1995 and was responsible for the large increase in meiofaunal biomass observed after spring 1996 . This replacement was presumably facilitated by the copepod size selection process operated by the filters . Large copepods were retained by the surface layer of sand or brought up by the backwash water and then exit the mesocosm through the drain . High meiofaunal populations did not significantly affect nitrogen cycling bacteria in sand filters probably because meiofauna also fed on other abundant food sources which were carried in by the water flow. Water Environ Res, 2001 May-Jun, 73(3), 368 - 73 Stratification and oxidation-reduction potential change in an aerobic and sulfate-reducing biofilm studied using microelectrodes; Yu T et al.; Recent studies in aerobic-nitrifying biofilms demonstrated the heterogeneity of biofilms used in wastewater treatment and led to modifications of the homogeneous assumptions in the conventional biofilm kinetic models . However, the stratification in aerobic-anaerobic biofilms has not been well investigated because of a lack of effective experimental tools . In this study a suite of microelectrodes, recently developed in the authors' laboratory, was used to examine the stratification of microbial processes and the change of oxidation-reduction potential (ORP) within an aerobic, sulfate-reducing biofilm . The microelectrodes have tip diameters of 3 to 20 microm and a high spatial resolution . They were used to measure the profiles of oxygen, total dissolved sulfide, ORP, and pH as a function of depth in the biofilm . The biofilm reactor was used to treat an azo-dye-containing wastewater with a chemical oxygen demand of 160 mg/L . The reactor bulk-phase dissolved oxygen concentration of the biofilm was 1.7 mg/L . The experimental results demonstrated that the microbial processes in the biofilm were stratified . In this biofilm, aerobic oxidation took place only in a shallow layer of 0.55 mm near the surface and sulfate reduction occurred in the deeper anoxic zone . The ORP changed with the shift of primary microbial process . The ORP was +362 mV at the biofilm surface and -166 mV near the substratum . Near the interface between the aerobic zone and the sulfate reduction zone, a surprisingly sharp decrease of ORP from a positive potential of +194 mV to a negative potential of -77 mV was observed . This occurred within a narrow band of 50 microm in depth . These new experimental findings support the concept of stratification of microbial processes and the associated ORP change in biofilms. Water Environ Res, 2001 May-Jun, 73(3), 329 - 38 Quantification of nitrifying bacterial populations in a full-scale nitrifying trickling filter using fluorescent in situ hybridization; Biesterfeld S et al.; Fluorescent in situ hybridization (FISH) was used to quantify the ammonia-oxidizing populations within intact biofilm samples collected from a full-scale nitrifying trickling filter (NTF) . Ammonia, nitrite, and nitrate concentrations were measured for aqueous samples taken in conjunction with biofilm samples at multiple filter depths . Correlation coefficients for individual sampling events, calculated by simple linear regression of FISH signal area and ammonia removal rates, ranged from 0.558 when using probe NEU23a to 0.982 when using probe Nso190 . The improved correlations with Nso190 suggest that genera other than Nitrosomonas are present in this system . Percent biofilm coverage, as determined by 4',6-diamidino-2-phenylindole counterstaining and dry weight biomass measurements, did not change throughout the NTF . This indicates that biofilm growth is fairly uniform throughout the filter even if nitrifier growth is not. Water Environ Res, 2001 Jan-Feb, 73(1), 95 - 102 pH and oxidation-reduction potential control strategy for optimization of nitrogen removal in an alternating aerobic-anoxic system; Kim H et al.; An alternating aerobic and anoxic (AAA) system is a continuous-flow, activated-sludge process in which the environmental conditions necessary to meet the specific requirements for aerobic nitrification and anoxic denitrification are created . Because of stricter regulations on wastewater effluent and concerns on energy consumption, the process control of the system is now becoming more important . A bench-scale AAA system with different fixed aeration ratios was operated for more than 8 months to evaluate effects of the total cycle time and aeration ratio on the system performance and to develop a feasible control scheme . With supplemental organic addition, the system shows removal efficiencies of 85 to 90% and 78 to 82% for chemical oxygen demand and total nitrogen, respectively . The oxidation-reduction potential (ORP) and pH profiles indicate that the aerobic cycle can be controlled by a control point (ammonia valley) on the pH profile indicating the end of nitrification and the anoxic cycle controlled by another point (nitrate knee) on the ORP profile signifying the end of denitrification . Thus, a dual control strategy with the pH and ORP control points was used for terminating aerobic-anoxic and initiating anoxic-aerobic cycles in an AAA system . The performance of the online control system is excellent, with a significant energy saving (average aeration ratio, fa = 0.23) as compared to the fixed time systems (fa = 0.33 to approximately 0.5). Water Environ Res, 2001 Jan-Feb, 73(1), 45 - 51 Posttreatment of a brewery wastewater using a sequencing batch reactor; Rodrigues AC et al.; This study concerns the application of a sequencing batch reactor (SBR) for the posttreatment of an effluent rejected by an upflow anaerobic sludge blanket (UASB) reactor operating in a brewery . The goal was to achieve the required wastewater quality for discharge to surface water . The primary target was the removal of nitrogen compounds, but chemical oxygen demand and suspended solids were also concerns . Phosphorus concentration and protozoan population were also monitored during SBR operation . Two different strategies were tested: an operation based on an aerobic-anoxic sequence and another based on applying a predenitrification step, that is, an anoxic-aerobic-anoxic sequence . Ammonium (NH4-N) removal was achieved in all assays . Nitrification efficiency reached 97%, and the maximum observed rate was 0.175 kg NH4-N/kg volatile suspended solids.d . A denitrification process was detected during the aerated periods, despite a dissolved oxygen concentration in the bulk liquid of 2.8 to 3.7 mg O2/L . However, denitrification was suppressed when the bulk liquid oxygen concentration was increased to 7 mg O2/L . The carbon-to-nitrogen ratio of the UASB effluent was too low and hindered the postdenitrification phase . This fact was confirmed by complete nitrate removal when an acetate supplement was added . On the other hand, the insertion of a primary anoxic phase in the reaction cycle was the best treatment strategy, leading to nitrogen values within the legal framework . The protozoan population showed significant changes in response to the aerobic-anoxic conditions . However, periodic nonaerated conditions were not detrimental to aerobic protozoa, which recovered as soon as oxygen was again available. Bioresour Technol, 2001 Oct, 80(1), 73 - 82 Effect of repeated addition of nitrite to semi-continuous activated sludge reactors; Philips S et al.; To a semi-continuous lab-scale activated sludge system (SCAS), nitrite was dosed discontinuously, i.e . together with the feed . The nitrite was added at a concentration (50 mg N/l) which had been found earlier not to cause acute inhibition of the general running of the reactors . Repeated nitrite addition, however, exerted an inhibitory effect which was reflected in decreased removal efficiencies and was also expressed in decreases in total respiratory and nitrifying activity of 20% and 40%, respectively . The inhibition by nitrite was reversible as removal efficiencies improved after ceasing nitrite addition . The two consecutive test runs revealed that addition of nitrite gave rise to high amounts of dispersed cells and free-swimming protozoa . Moreover, DGGE patterns confirmed a shift in microbial community structure upon application of nitrite. Appl Microbiol Biotechnol, 2001 Aug, 56(3-4), 504 - 7 Evaluation of nitric oxide production by lactobacilli; Xu J et al.; Six strains of Lactobacillus fermentum and Lactobacillus plantarum were investigated for nitric oxide (NO) production . First, the potential presence of NO synthase was examined . None of the strains of L . fermentum and L . plantarum examined produced NO from L-arginine under aerobic conditions . Interestingly, all L . fermentum strains expressed strong L-arginine deiminase activity . All L . fermentum strains produced NO in MRS broth, but the NO was found to be chemically derived from nitrite, which was produced by L . fermentum from nitrate present in the medium . Indeed all L . fermentum strains express nitrate reductase under anaerobic conditions . Moreover, one strain, L . fermentum LF1, had nitrate reductase activity under aerobic conditions . It was also found that L . fermentum strains JCM1173 and LF1 possessed ammonifying nitrite reductase . The latter strain also had denitrifying nitrite reductase activity at neutral pH under both anaerobic and aerobic conditions . The LF1 strain is thus capable of biochemically converting nitrate to NO . NO and nitrite produced from nitrate by lactobacilli may constitute a potential antimicrobial mechanism . studied in a rat acute liver injury model (Adawi et al . 1997) . The results indicate that Lactobacillus plantarum DSM 9842 may possess NOS (Adawi et al . 1997) . However, NO production from L-arginine has not been investigated in pure cultures of L . plantarum . According to the results of a 15N enrichment experiment, traces of (NO2-+NO3-)-N (total oxidised nitrogen: TON), which seemed to be formed by the resting cells of Lactobacillus fermentum IFO3956, appeared to be derived from L-arginine (Morita et al . 1997) . Therefore, it was suggested that L . fermentum may possess a NOS . However, NO produced from L-arginine was not directly measured and a NOS inhibitor test was not performed by Morita et al . (1997) . It is known that L-arginine deiminase (ADI) in bacteria may convert L-arginine to NH4+ (Cunin et al . 1986), which may be further oxidised to TON via nitrification by bacteria . Therefore, 15N enrichment experiments could not definitely conclude that L . fermentum possess NOS to convert L-arginine directly to NO . In this study, six Lactobacillus strains belonging to L . plantarum and L . fermentum were measured for NO production in MRS broth . The metabolism of nitrate and L-arginine by the Lactobacillus cell suspensions was also studied . The possibility that NO and nitrite production by lactobacilli may be a potential probiotic trait is also discussed. Water Sci Technol, 2001, 44(2-3), 63 - 8 Experience with an up-flow biological aerated filter (BAF) for tertiary treatment: from pilot trials to full scale implementation; Payraudeau M et al.; Biofilters can be added to existing non-nitrifying activated sludge plants for tertiary ammonia removal and effluent polishing . It is a convenient, efficient, and cost effective way of meeting more stringent consents . In order to prove this technology, a biofilter pilot plant was installed in a large activated sludge plant with challenging conditions, since almost half of the load is industrial effluent and the water temperature can be as low as 7 degrees C . Trials were conducted over a two year period, providing the following information: low water temperature does not affect the process; the optimum rise rate at nominal flow is 8.5 m/h for this wastewater; the consent can be achieved for ammonia loads up to 0.94 kgNH4N/M3 media/day; about 50% of the post-secondary TSS and BOD can be removed in the BAF; a large proportion of industrial effluent has not had any noticeable effect on the beads after two years . A full scale plant with a nominal flow of 8257 l/s was then built and commissioned in summer 1998 . Seeding was completed within three weeks of starting the filters . Two months later, a 28 day takeover was started . Results obtained on full scale plant during and after this test confirm the results obtained on the pilot. Water Sci Technol, 2001, 44(2-3), 367 - 72 Nitrogen and sulfate attenuation in simulated landfill bioreactors; Onay TT et al.; The characteristics of leachate from landfills vary according to site-specific conditions . Leachates from old landfills are often rich in ammonia nitrogen, posing potential adverse environmental impacts in the case of uncontrolled discharge . At landfills where leachate recirculation is practiced, leachate ammonia concentrations may accumulate to higher levels than during the single pass leaching . Using leachate recirculation with system modifications, separate aerobic and anoxic zones for nitrification and both autotrophic and heterotrophic denitrification can be provided . Results from simulated landfill bioreactors indicated that both nitrogenous and sulfur compounds can be attenuated through autotrophic denitrification, and leachate nitrate concentrations of 750 mg/L reduced to less than 1 mg/L by denitrification to nitrogen gas promoting this very common process in a landfill environment results in the reduction of both leachate ammonia and sulfate concentrations. Water Sci Technol, 2001, 44(2-3), 359 - 65 Combined ozone-activated sludge treatment of landfill leachate; Geenens D et al.; Biological treatment is widely preferred by many landfill owners to remove the bulk of the pollutants in leachate . Specific problems due to toxicity and nutrient deficiencies are however frequently reported . This study investigates the possibility of pre-treating leachate to decrease its toxicity and increase its biodegradability, using ozonation . Lab-scale and pilot testing has shown that nitrification toxicity was minimised by ozone pre-treatment . A decrease of the COD/BOD-ratio from 16 to 6 was achieved, making the pre-treated leachate co-treatable in municipal sewage treatment . The operational cost for the pre-treatment was estimated at 1.34 Euro/kg COD.
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