Environ Technol, 2004 Jun, 25(6), 699 - 712 Simultaneous carbon and nitrogen removal in anoxic-aerobic circulating fluidized bed biological reactor (CFBBR); Cui Y et al.; Biological nutrient removal (BNR) in municipal wastewater treatment to remove carbonaceous substrates and nutrients, has recently become increasingly popular worldwide due to increasingly stringent regulations . Biological fluidized bed (BFB) technology, which could be potentially used for BNR, can provide some advantages such as high efficiency and a compact structure . This work shows the results of simultaneous elimination of organic carbon and nitrogen using a circulating fluidized bed biological reactor (CFBBR, which has been developed recently for chemical engineering processes . The CFBBR has two fluidized beds, running as anoxic and aerobic processes to accomplish simultaneous nitrification and denitrification, with continuous liquid recirculation through the anoxic bed and the aerobic bed . Soluble COD concentrations in the effluent ranging from 4 to 20 mg l(-1) were obtained at varying COD loading rates; ammonia nitrogen removal efficiencies averaged in excess of 99% at a minimum total hydraulic retention time (HRT) of 2.0 hours over a temperature range of 25 degrees C to 28 degrees C . Effluent nitrate nitrogen concentration of less than 5 mg l(-1) was achieved by increasing effluent recycle rate . No nitrite accumulation was observed either in the anoxic bed or in the aerobic bed . The system was able to treat grit chamber effluent wastewater at a HRT of 2.0 hours while achieving average effluent BOD, COD, NH3-N, TKN, nitrates, total phosphate, TSS and VSS concentrations of 10 mg l(-1), 18 mg l(-1), 1.3 mg l(-1), 1.5 mg l(-1), 7 mg l(-1), 2.0 mg l(-1), 10 mg l(-1) and 8 mg l(-1) respectively . The CFBBR appears to be not only an excellent alternative for conventional activated sludge type BNR technologies but also capable of processing much higher loadings that are suitable for industrial applications. Biochemistry, 2004 Sep 7, 43(35), 11206 - 13 Characterization of a small metal binding protein from Nitrosomonas europaea; Barney BM et al.; A small metal-binding protein (SmbP) with no known similarity to other proteins in current databases was isolated and characterized from the periplasm of Nitrosomonas europaea . The primary structure of this small (9.9 kDa) monomeric protein is characterized by a series of 10 repeats of a seven amino acid motif and an unusually high number of histidine residues . The protein was isolated from N . europaea with Cu(II) bound but was found to be capable of binding multiple equivalents of a variety of divalent and trivalent metals . The protein was overexpressed in Escherichia coli and used for the study of its metal-binding properties by UV/vis, circular dichroism (CD), and electron paramagnetic resonance (EPR) spectroscopy and equilibrium dialysis and isothermal titration calorimetry . The protein was found to bind up to six Cu(II) atoms with dissociation constants of approximately 0.1 microM for the first two metal ions and approximately 10 microM for the next four . Binding of Cu(II) resulted in spectroscopic features illustrating two distinctive geometries, as determined by EPR spectroscopy . The levels of SmbP in the periplasm were found to increase by increasing the levels of copper in the growth media . This protein is proposed to have a role in cellular copper management in the ammonia-oxidizing bacterium N . europaea. Environ Technol, 2004 Aug, 25(8), 957 - 65 Optimizing settling conditions for treatment of liquid hog manure; Trias M et al.; Sedimentation is a widely used separation method for treating agricultural waste . There are several chemical and biological characteristics, which can affect the settling behavior and liquid waste . The optimization of cation balances and potential for nitrification are among these processes . In addition to sedimentation, it can also affect the dewaterability of the samples . Liquid hog manure was used during the laboratory based experiments to investigate the effects of Ca2+ and Mg2+ ions and nitrification inhibition on the overall settling and dewatering characteristics . The results indicated that settling and dewatering characteristics improved during the course of the experiments . However, the improvement in settling and dewatering characteristics was inconsistent and not statistically significant . Cation addition in aerated reactor increased the highest settling velocity (94%).The improvement in dewaterability, as quantified by capillary suction time, was also not consistent . The greatest filterability observed in the supernatant was a capillary suction time of 40 s for a M:D ratio of 2:1 . Initial NH 4 + concentration was more important than the nitrification inhibitor, as the presence of nitrification inhibitor increased the nitrification rate by over 300% because of the high initial NH 4 + concentration and low volatile suspended solid . The results from these experiments provide the basis for further field evaluation of cation optimization. J Environ Qual, 2004 Sep-Oct, 33(5), 1647 - 52 Quantification of the effect of fumigation on short- and long-term nitrogen mineralization and nitrification in different soils; De Neve S et al.; The effect of soil fumigation on N mineralization and nitrification needs to be better quantified to optimize N fertilizer advice and predict NO(-)(3) concentrations in crops and NO(-)(3) leaching risks . Seven soils representing a range in soil texture and organic matter contents were fumigated with Cyanamid DD 95 (a mixture of 1,3-dichloropropane and 1,3-dichloropropene) . After removal of the fumigant, the fumigated soils and unfumigated controls were incubated for 20 wk and N mineralization and nitrification were monitored by destructive sampling . The average short-term N mineralization rates (k(s)) were significantly larger in the fumigated than in the unfumigated soils (P = 0.025), but the differences in k(s) between fumigated and unfumigated soils could not be related to soil properties . The average long-term N mineralization rates (k(l)) were slightly larger in the fumigated soils but the difference with the unfumigated soils was not significant . Again, the differences in k(l) values could not be related to soil properties . Nitrification was inhibited completely for at least 3 wk in all soils, and an effect on nitrification could be observed up to 17 wk in one soil . An S-shaped function was fitted to the nitrification data corrected for N mineralization, and both the rate constant (gamma) and the time at which maximum nitrification was reached (t(max)) were strongly correlated to soil pH . However, since no correlations were found between the effect of fumigation on N mineralization and soil properties, taking into account the effects of fumigation in fertilizer advice and in the prediction of NO(-)(3) leaching risks will need further research. Water Res, 2004 Oct, 38(17), 3760 - 8 Effect of nitrite on phosphate uptake by phosphate accumulating organisms; Saito T et al.; In biological nitrogen removal processes, nitrite can be formed and accumulated through both nitrification and denitrification . Despite the fact that, in practice, biological phosphate removal (BPR) is often combined with biological nitrogen removal, there are only a few publications reporting the effect of nitrite on BPR . In this study, phosphate-accumulating organisms (PAO) were cultivated in an anaerobic-anoxic-aerobic sequencing batch reactor (SBR) . The effect of nitrite on the enrichment of the sludge with PAO, the phosphate uptake rates and the sludge respiration was investigated . The results indicate that (1) presence of nitrite inhibits both aerobic and anoxic (denitrifying) phosphate uptake, (2) aerobic phosphate uptake was more affected than anoxic phosphate uptake, (3) presence of nitrite could be one of the factors enhancing the presence of glycogen accumulating organisms (GAO)--competitors to PAO for substrate in the anaerobic phase, and (4) it is required to monitor and control nitrite accumulation in a full-scale wastewater treatment plants. Environ Technol, 2004 Jul, 25(7), 833 - 40 Growth of water hyacinth in municipal landfill leachate with different pH; El-Gendy AS et al.; Batch experiments were conducted to investigate the effect of municipal landfill leachate pH on the growth of water hyacinth (Eichhornia crassipes) . These experiments were carried out in a green house environment on leachate samples collected from Essex-Windsor Regional Landfill, Windsor, Ontario, Canada . It was found that water hyacinth plants survived in a pH range of 4.0 to 8.0 . Both alkaline pH (above 8.0) and highly acidic pH (below 4.0) had inhibitory effect on the growth of plants . The pH range, for optimum growth of the water hyacinth plants was found to be 5.8 to 6.0 . At optimum growth, water hyacinth had an average mean relative growth rate of 0.043 d-1 . It was found that nitrogen compounds underwent different transformations depending on the pH of leachate . Plant uptake, nitrification and volatilization were among these transformations. Appl Environ Microbiol, 2004 Sep, 70(9), 5528 - 37 Competition between ammonia-oxidizing bacteria and benthic microalgae; Risgaard-Petersen N et al.; The abundance, activity, and diversity of ammonia-oxidizing bacteria (AOB) were studied in prepared microcosms with and without microphytobenthic activity . In the microcosm without alga activity, both AOB abundance, estimated by real-time PCR, and potential nitrification increased during the course of the experiment . AOB present in the oxic zone of these sediments were able to fully exploit their nitrification potential because NH(4)(+) did not limit growth . In contrast, AOB in the alga-colonized sediments reached less than 20% of their potential activity, suggesting starvation of cells . Starvation resulted in a decrease with time in the abundance of AOB as well as in nitrification potential . This decrease was correlated with an increase in alga biomass, suggesting competitive exclusion of AOB by microalgae . Induction of N limitation in the oxic zone of the alga-colonized sediments and O(2) limitation of the majority of AOB in darkness were major mechanisms by which microalgae suppressed the growth and survival of AOB . The competition pressure from the algae seemed to act on the entire population of AOB, as no differences were observed by denaturing gradient gel electrophoresis of amoA fragments during the course of the experiment . Enumeration of bacteria based on 16S rRNA gene copies and d-amino acids suggested that the algae also affected other bacterial groups negatively . Our data indicate that direct competitive interaction takes place between algae and AOB and that benthic algae are superior competitors because they have higher N uptake rates and grow faster than AOB. Water Sci Technol, 2004, 50(2), 255 - 61 Modeling the fate and transport of organic and nitrogen species in soil aquifer treatment process; Kim JW et al.; Soil aquifer treatment (SAT) is a promising technique for wastewater reclamation and reuse . This treatment strategy takes advantage of physicochemical and biological processes in the subsurface . The model employed in this study is based on MODFLOW-SURFACT (HydroGeoLogic, Inc.), a three-dimensional model for variably saturated flow and reactive mass transport . The model accounts for reactions including the nitrification of ammonium, the denitrification of nitrate, and the oxidation of organic carbon . Concentration of dissolved oxygen and biomasses involved in aerobic and anaerobic biological reactions forms the basis for estimates of nonlinear reaction rates formulated using a multiple-Monod expression . Illustrative simulations were conducted in a two-dimensional cross-sectional domain, with unsaturated and saturated zones . They examine the effects that site and operational conditions have on the performance of a SAT system . The parameters and conditions of concern included length of the wet/dry cycle, ground surface condition, and infiltration rate . From the simulations, we found that organic carbon was effectively removed in all cases . The availability of oxygen was a key factor in predicting the production and removal of nitrate . Overall, the model successfully described the fate and transport of the key constituents during the wet/dry operational periods in both unsaturated and saturated subsurface. Water Sci Technol, 2004, 50(2), 195 - 201 Mathematical model for describing reactions of residual chlorine with organic matter in reclaimed wastewater; Funamizu N et al.; Among several applications of urban wastewater reuse, use of reclaimed wastewater to sustain stream flows has become attractive in the urban area . Since these rivers are used for recreational purposes and for restoring aquatic eco-system, the adequate control of residual chlorine is essential . Mathematical model for describing reactions between residual chlorine and organic matter in reclaimed wastewater has been developed . The model considers the effect of molecular weight distribution of organic matter on the reaction rate . Lab-scale experiments were performed to estimate reaction rates constants and to examine their temperature dependency . The experiments showed that 1) the smaller organic matter gave the larger reaction rate; 2) temperature effect on reaction rate was described by the Arrhenius formula; 3) decline of free chlorine had more temperature dependency than combined chlorine . The comparison of computed results with data from lab-scale experiments confirmed the validity of the model . We used the one-dimensional dispersion model with proposed reaction model and examined the seasonal variation of residual chlorine profile along the river sustained by reclaimed wastewater in Sapporo . Simulation showed that seasonal variation of nitrification performance in secondary treatment as well as change in temperature caused seasonal variation in residual chlorine profile along the river. Water Sci Technol, 2004, 50(2), 77 - 82 Utilization of treated swine wastewater for greenhouse tomato production; Cheng J et al.; An integrated system has been developed to recycle waste organics and treated wastewater from a swine farm to make value-added products and to protect the environment from potential contamination . The farm is a farrow-to-wean swine operation with approximately 4,000 sows . A high-strength wastewater (chemical oxygen demand, 18,000 mg/l; total Khejdal nitrogen, 1,600 mg/l; total phosphorus, 360 mg/l) is produced from the swine operation . An ambient-temperature anaerobic digester has been used to treat the swine wastewater and to produce biogas (from an average 475 m3/day in winter to 950 m3/day in summer) . The biogas is combusted in an engine to produce electricity (around 900 kW-hr/day) . The digester effluent that is rich in nutrients (N, P, and minerals) is then utilized for fertigation for greenhouse tomato production . A trickling nitrification biofilter has been developed to convert ammonium in the effluent into nitrate . The nitrified anaerobic effluent is used as both fertilizer and irrigation water for approximately 14,400 tomato plants in greenhouses . Experimental data indicate that the tomato greenhouses have used approximately 12 m3 of the effluent and 3.84 kg nitrogen per day . At the same time, the greenhouses have a daily yield of 520 kg (37 g/plant) of marketable fruit. Water Sci Technol, 2004, 50(2), 47 - 53 Water reuse for irrigation from waste water treatment plants with seasonal varied operation modes; Cornel P et al.; Irrigation periods are usually limited to vegetation periods . The quality requirements for treated wastewater for disposal and for reuse are different . The reuse of water for irrigation allows partly the reuse of the wastewater's nutrients (N and P) . Outside the irrigation period the water must be treated for disposal, thus nutrient removal is often required in order to avoid detrimental effects on the receiving surface water body . Only wastewater treatment plants with different operation modes for different seasons can realise these requirements . The nitrification is the most sensitive biological process in the aerobic wastewater treatment process . At low water temperatures the nitrifying bacteria need several weeks to re-start full nitrification after periods without NH4-removal . Therefore it is necessary to develop options for waste water treatment plants which allow a fast re-start of the nitrification process . Based on theoretical considerations and computer simulations of the activated sludge treatment process, one possibility for implementing a wastewater treatment plant with different seasonal operation modes is evaluated. Water Environ Res, 2004 May-Jun, 76(3), 272 - 9 Behaviors of intercellular materials and nutrients in biological nutrient removal process supplied with domestic wastewater and food waste; Chae SR et al.; A four-stage biological nutrient removal (BNR) process was operated to investigate the effect of anaerobically fermented leachate of food waste (AFLFW) as an external carbon source on nutrient removal from domestic wastewater having a low carbon-to-nitrogen ratio . The BNR system that was supplemented with AFLFW showed a good performance at a sludge retention time (SRT) of 30 days, despite low temperature . With this wastewater, average removal efficiencies of soluble chemical oxygen demand (COD), total nitrogen (T-N), and total phosphorus (T-P) were 88 to 93%, 70 to 74%, and 63 to 68%, respectively . In this study, several kinds of poly-hydroxyalkanoates (PHAs) were observed in cells . These included 24% poly-3-hydroxybutyrate (PHB), 41% poly-3-hydroxyvalerate (PHV), 18% poly-3-hydroxyhexanoate (PHH), 10% poly-3-hydroxyoctanoate (PHO), 5% poly-3-hydroxydecanoate (PHD) . and 2% poly-3-hydroxydodecanoate (PHDD), indicating that microorganisms could store various PHAs through the different metabolic pathways . However, breakdown of the enhanced biological phosphorus removal (EBPR) mechanism was observed when SRT increased from 30 to 50 days for the enhancement of nitrification . To study the effect of SRT on EBPR, a sequencing batch reactor (SBR) system that was supplied with glucose was operated at various SRTs of 5, 10, and 15 days . Nitrification and denitrification efficiencies increased as SRT increased . However, the content of intracellular materials such as PHAs, glycogen . and poly-P in cells decreased . From these results, it was concluded that SRT should be carefully controlled to increase nitrification activity and to maintain biological phosphorus removal activity in the BNR process. Water Environ Res, 2004 May-Jun, 76(3), 238 - 44 Analyzing the uncorrected error of dilution water demand for the dilution biochemical oxygen demand method; Chiang CF et al.; Dilution water demand (DWD) can cause a positive error when the dilution biochemical oxygen demand (BOD) method is used . Dilution water demand may be attributed to oxidation of organic impurities in the dilution water and nitrification of ammonia added as a nutrient . To minimize the error associated with these sources, the standard BOD method requires that DWD be less than 0.2 mg/L in 5 days and does not allow correction for DWD when calculating test results . This study derives a set of theoretical equations to analyze the uncorrected errors with and without seeding . The authors concluded that DWD can be completely corrected if seeded dilution water is used for the sample dilution . When seeding individual bottles, the uncorrected error approaches 8.3 to approximately 8.8% at a 5-day depletion of 2 mg/L for a typical secondary effluent . Tests without seeding show an almost 1% higher uncorrected error than seeded tests . The analysis also suggests that these errors can be effectively reduced to less than 3% when the 5-day depletion approaches 6 mg/L . even for 5-day biochemical oxygen demand concentrations exceeding I x 10(4) mg/L . Further analysis indicates that, if not inhibited, the ammonium added to dilution water as a nutrient may contribute additional error due to nitrification. J Ind Microbiol Biotechnol, 2004 Sep, 31(8), 353 - 61 Epub 2004 Jul 28. Removal of carbonaceous and nitrogenous pollutants from a synthetic wastewater using a membrane-coupled bioreactor; Ghosh S et al.; Two modified Ludzack-Ettinger (MLE)-type membrane-coupled bioreactors (MBRs) were investigated in this study for the purpose of removing both nitrogenous and carbonaceous pollutants from a synthetic wastewater . During the first MBR experiment, removal efficiencies were high (>90%) for chemical oxygen demand (COD) and ammonia, but total nitrogenous pollutant removal efficiency was poor (approximately 25%) . Bacterial community analysis of ammonia oxidizing bacteria (AOB) by a nested PCR-DGGE approach detected two Nitrosomonas-like populations and one Nitrosospira-like population . During the initial portion of the second MBR experiment, COD and ammonia removal efficiencies were similar to the first MBR experiment until the COD of the influent wastewater was increased to provide additional electron donors to support denitrification . Total nitrogen removal efficiencies eventually exceeded 90%, with a hydraulic residence time (HRT) of 24 h and a recirculation ratio of 8 . When the HRT of the MBR experiment was decreased to 12 h, however, ammonia removal efficiency was adversely affected . A subsequent increase in the HRT to 18 h helped improve removal efficiencies for both ammonia (>85%) and total nitrogenous compounds (approximately 70%) . Our research demonstrates that MBRs can be effectively designed to remove both carbonaceous and nitrogenous pollutants . The ability of the microbial community to switch between anoxic (denitrifying) and oxic (nitrifying) conditions, however, represents a critical process constraint for the application of MLE-type MBR systems, such that little benefit is gained compared to conventional designs. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2004, 39(8), 2229 - 39 A two-stage SBR process for removal of organic substrate and nitrogen via nitrite-type nitrification-denitrification; Zeng W et al.; A two-stage SBR process (TSSBR) was applied for the treatment of wastewater with high strength COD and nitrogen . Most of organic substrate was removed in the first stage SBR reactor (SBR1) under the aerobic condition . Subsequently the second stage SBR reactor (SBR2) firstly was operated under the aerobic condition for simultaneous nitrite-type nitrification and removal of a small amount of residual organic substrate . Nitrification was controlled to the nitrite-type nitrification . Then denitrification in which the wastewater was used as external carbon sources occurred in SBR2 under the anoxic condition . The experimental results indicated that two kinds of biomass with the different function were cultured in a TSSBR system, which was beneficial to increase the proportion of Nitrosomonas in the microorganism of SBR2 . It avoided the inhibition of the high organic loading to nitrification and C/N was not the limiting factor affecting the nitrogen removal efficiency . The rate of COD degradation and nitrification was improved, 8 kg COD/kg MLSS/d and 0.25 kg NH4+-N/kg MLSS/d, respectively . The final effluent COD concentration further reduced because the organic substrate that was left in SBR1 effluent was removed in SBR2 . Consequently, when compared to a single SBR process, a two-stage SBR (TSSBR) not only improved the treatment efficiency, but also saved the operational cost. Huan Jing Ke Xue, 2004 Jan, 25(1), 158 - 60 {Study on biological nutrients removal in loop reactor}; Yang HG et al.; The simultaneity nitrification and denitrification (SND) was studied in a loop reactor . In the experiment, the research of biological nutrients removal was carried by changing carbon source and the method of adding carbon source, and the concentration of NOx(-)-N and the dissolved oxygen (DO) level were also inspected . The results indicated that the removal of NH4+-N could be enhanced by adding carbon source with COD 800 mg/L + 800 mg/L . And the concentration of NH4+-N in outlet was lower than 3 mg/L; Lower DO level in the reactor could be made easily by using difficultly reduced carbon source . It was useful to improve the biological nutrients removal . When using ethanol or glycerol as carbon source, the removal efficiency of NH4+-N was better than using glucose. Huan Jing Ke Xue, 2004 May, 25(3), 106 - 9 {Joint inhibition of benzene and monosubstituted benzenes on ammonia-oxidizing activity of sediment}; Dong CH et al.; The joint inhibitions of benzene and three kinds of monosubstituted benzenes (aniline, phenol and nitrobenzene) on ammonia-oxidizing activity of sediment was investigated in order to study the effects of combined pollutants on nitrification process in the nitrogen cycle . The results showed that the joint inhibiton of 11 different kinds of mixtures, including binary or multi-equitoxic mixtures among benzene, aniline, phenol and nitrobenzene, exhibited different effects on ammonia-oxidizing activity of sediment, among which seven were addictive effect, three were synergistic, and only the mixture of benzene and phenol was antagonism . A conclusion could be made that the addition of nitrobenze to a mixture usually exhibited addictive effect . There was a relationship between the half joint inhibition concentrations (IC50, micromol x L(-1)) of benzene and monosubstituted benzenes on ammonia-oxidizing activity of sediment and the mixed electronegativities (MEs): lgIC50 = 2.197 - 0.236ME . With the increase of mixed electronegativities (MEs), the joint inhibitions of mixtures increased. Sci Total Environ, 2004 Sep 1, 330(1-3), 1 - 8 Purification capacity of a highly loaded laboratory scale tidal flow reed bed system with effluent recirculation; Zhao YQ et al.; The purification capacity of a laboratory scale tidal flow reed bed system with final effluent recirculation at a ratio of 1:1 was investigated in this study . In particular, the four-stage reed bed system was heavily loaded with strong agricultural wastewater . Under the hydraulic and organic loading rates of 0.43 m3/m2.d and 1055 gCOD/m2.d, respectively, the average removal efficiencies obtained for COD, BOD5, SS, NH4-N and P were 77%, 78%, 66%, 62% and 38%, respectively . Even with the high loading rates, approximately 30% of NH4-N was converted into NO2-N and NO3-N from the mid-stage of the system where nitrification took place . The results suggest that the multi-stage reed bed system could be employed to treat strong wastewater under high loading, especially for the substantive mass removal of solids, organic matter and ammoniacal-nitrogen . Tidal flow combined with effluent recirculation is a favourable operation strategy to achieve this objective. Water Sci Technol, 2004, 50(1), 83 - 90 Investigation of opportunistic pathogens in municipal drinking water under different supply and treatment regimes; Pryor M et al.; Changing regulations to lower disinfectant byproducts in drinking water is forcing utilities to switch disinfection from chlorine to monochloramine . It is generally unknown whether this will impact positively or negatively on the microbiological quality of drinking water . A utility in Florida, using water with relatively high organic carbon levels from deep wells in several wellfields, made the decision to change its disinfection regime from chlorine to chloramine in order to meet the new regulations . To assess the impacts of such a change on the microbiology of its water supplies, it undertook a number of studies before and after the change . In particular, the presence of the opportunistic pathogens Legionella and Mycobacterium, and also the composition of drinking-water biofilms, were examined . A preliminary synthesis and summary of these results are presented here . Legionella species were widely distributed in source waters and in the distribution system when chlorine was the disinfectant . In some samples they seemed to be among the dominant biofilm bacteria . Following the change to monochloramine, legionellae were not detected in the distribution system during several months of survey; however, they remained detectable at point of use, although with less species diversity . A variety of mycobacteria (21 types) were widely distributed in the distribution system when chlorine was the disinfectant, but these seemed to increase in dominance after chloramination was instituted . At point of use, only four species of mycobacteria were detected . Other changes occurring with chloramination included (a) an altered biofilm composition, (b) increased numbers of total coliforms and heterotrophs and (c) nitrification of water storage tanks . The results suggested that consideration should be given to the microbiological effects of changing disinfection regimes in drinking-water and distribution system biofilms. J Ind Microbiol Biotechnol, 2004 Sep, 31(8), 369 - 78 Epub 2004 Aug 13. Impacts of reduced sulfur components on active and resting ammonia oxidizers; Sears K et al.; While there has been significant research on the nature and extent of the impact of inhibitory reduced sulfur with respect to anaerobic (e.g., methanogenic and sulfidogenic) microbial systems, only limited study has yet been conducted on the comparable effects of soluble sulfides which might occur within aerobic wastewater treatment systems . Admittedly, aerobic reactors would not normally be considered conducive to the presence of reduced sulfur constituents, but there do appear to be a number of processing scenarios under which related impacts could develop, particularly for sensitive reactions like nitrification . Indeed, the following scenarios might well involve elevated levels of reduced sulfur within an aerobic reactor environment: (1) mixed liquor recycle back through sulfide-generating anaerobic zones (e.g., in conjunction with biological nutrient removal processes, etc.), (2) high-level side-stream sulfide recycle via sludge digestion, etc., back to aerobic reactors, and (3) high-level influent sulfide inputs to wastewater treatment facilities via specific industrial, septage, etc., streams . The objective of this study was, therefore, to determine the subsequent metabolic impact of soluble sulfide under aerated and unaerated conditions, focusing in particular on ammonia-oxidizing bacteria due to their critical first-step role with nitrification . The obtained results indicated that, under catabolically active conditions, cultures of ammonia oxidizers were extremely sensitive to the presence of sulfide . At total soluble sulfide concentrations of 0.25 mg l(-1) S, active ammonia oxidation was completely inhibited . However, immediately following the removal of this soluble sulfide presence, ammonia oxidation started to recover; and it continued to improve over the next 24 h . Similar sulfide impact tests conducted with inactive ammonia oxidizers exposed during anaerobic conditions, albeit at higher dosage levels, also revealed that their subsequent aerobic activity would correspondingly be retarded . These results indicated that, after sulfide exposure under unaerated conditions, subsequent aerobic oxidative activity rates rapidly decreased as the soluble sulfide exposure was increased from 0.5 gm l(-1) S to 5 mg l(-1) S and that further reductions in this activity progressively developed as the concentration was increased to 200 mg l(-1) S . The recovery following unaerated exposure to sulfide was significantly higher at pH 7, as compared with pH 8, and although the specific nature of this variation was not established, a hypothetical explanation appeared warranted. Appl Microbiol Biotechnol . 2004 Aug 14; {Epub ahead of print} Biological nitrogen and organic matter removal from tannery wastewater in pilot plant operations in Ethiopia; Leta S et al.; The objective of this study was to set-up a pilot plant and to evaluate its effectiveness for biological nitrogen and organic matter removal from tannery wastewater in Ethiopia . A pilot wastewater treatment plant consisting of a predenitrification-nitrification process was constructed and operated for 6 months . This was fed with a raw tannery wastewater obtained from the Modjo Tannery located 70 km south of the capital, Addis Ababa . Up to 98% total nitrogen and chemical oxygen demand, and 95% ammonium nitrogen removal efficiencies were achieved in the system . The average effluent ammonium nitrogen ranged from 8.4 mg l(-1) to 86.0 mg l(-1), whereas the average effluent for nitrate nitrogen ranged from 2.9 mg l(-1) to 4.4 mg l(-1) . The average values of denitrification and nitrification rates determined by nitrate and ammonium uptake rates (NUR and AUR) were 8.0 mg NO(3)-N {g volatile suspended solids (VSS)}(-1) h(-1) and 5.4 mg NH(4)-N (g VSS)(-1) h(-1), respectively, demonstrating that the treatment processes of the pilot plant were effective . Further studies of the effect of chromium III on AUR showed 50% inhibition at a concentration of 85 mg l(-1), indicating that this metal was not causing process inhibition during performance operations . Thus, the predenitrification-nitrification process was found to be efficient for simultaneous removal of nitrogen and organic substrates from tannery wastewaters. Water Sci Technol, 2004, 49(11-12), 365 - 70 Transition of bacterial spatial organization in a biofilm monitored by FISH and subsequent image analysis; Aoi Y et al.; The dynamic transition of bacterial community structure in a biofilm was monitored by the fluorescence in situ hybridization (FISH) technique and subsequent image analysis . Heterotrophic bacteria that had occupied the outer layer were gradually decreased whereas ammonia-oxidizing bacteria (AOB) gradually increased their growth activity and extended their existence area to the outer layer of the biofilm through the gradual reduction of the C/N ratio . The spatial organization of AOB in the biofilm dynamically changed responding to the environmental conditions such as pH fluctuation and lack of dissolved oxygen (DO) and had great influence on the nitrification activity . The accumulation of nitrite was observed at lower DO concentration, which might be due to the property that nitrite-oxidizing bacteria (NOB) possess of higher Km values for oxygen than AOB. Water Sci Technol, 2004, 49(11-12), 327 - 36 Microbial communities and their interactions in biofilm systems: an overview; Wuertz S et al.; Several important advances have been made in the study of biofilm microbial populations relating to their spatial structure (or architecture), their community structure, and their dependence on physicochemical parameters . With the knowledge that hydrodynamic forces influence biofilm architecture came the realization that metabolic processes may be enhanced if certain spatial structures can be forced . An example is the extent of plasmid-mediated horizontal gene transfer in biofilms . Recent in situ work in defined model systems has shown that the biofilm architecture plays a role for genetic transfer by bacterial conjugation in determining how far the donor cells can penetrate the biofilm . Open channels and pores allow for more efficient donor transport and hence more frequent cell collisions leading to rapid spread of the genes by horizontal gene transfer . Such insight into the physical environment of biofilms can be utilized for bioenhancement of catabolic processes by introduction of mobile genetic elements into an existing microbial community . If the donor organisms themselves persist, bioaugmentation can lead to successful establishment of newly introduced species and may be a more successful strategy than biostimulation (the addition of nutrients or specific carbon sources to stimulate the authochthonous population) as shown for an enrichment culture of nitrifying bacteria added to rotating disk biofilm reactors using fluorescent in situ hybridization (FISH) and microelectrode measurements of NH4+, NO2-, NO3-, and O2 . However, few studies have been carried out on full-scale systems . Bioaugmentation and bioenhancement are most successful if a constant selective pressure can be maintained favoring the promulgation of the added enrichment culture . Overall, knowledge gain about microbial community interactions in biofilms continues to be driven by the availability of methods for the rapid analysis of microbial communities and their activities . Molecular tools can be grouped into those suitable for ex situ and in situ community analysis . Non-spatial community analysis, in the sense of assessing changes in microbial populations as a function of time or environmental conditions, relies on general fingerprinting methods, like DGGE and T-RFLP, performed on nucleic acids extracted from biofilm . These approaches have been most useful when combined with gene amplification, cloning and sequencing to assemble a phylogenetic inventory of microbial species . It is expected that the use of oligonucleotide microarrays will greatly facilitate the analysis of microbial communities and their activities in biofilms . Structure-activity relationships can be explored using incorporation of 13C-labeled substrates into microbial DNA and RNA to identify metabolically active community members . Finally, based on the DNA sequences in a biofilm, FISH probes can be designed to verify the abundance and spatial location of microbial community members . This in turn allows for in situ structure/function analysis when FISH is combined with microsensors, microautoradiography, and confocal laser scanning microscopy with advanced image analysis. Water Sci Technol, 2004, 49(11-12), 263 - 8 Enhancement of biofilm formation onto surface-modified hollow-fiber membranes and its application to a membrane-aerated biofilm reactor; Terada A et al.; Surface-modified hollow-fiber membranes were prepared by radiation-induced grafting of an epoxy-group-containing monomer, glycidylmethacrylate (GMA), onto a polyethylene-based fiber (PE-fiber) . The epoxy ring of GMA was opened by introduction of diethylamine (DEA) . The bacterial adhesivity to this material (DEA-fiber) was tested by immersion into a nitrifying bacterial suspension . The initial adhesion rates and the amount of attached bacteria of the DEA-fiber were 6-10-fold and 3-fold greater than those of the PE fiber, respectively . A membrane-aerated biofilm reactor (MABR) composed of DEA fibers was developed for partial nitrification with nitrite accumulation . Prior to the nitrification test, it was confirmed that the oxygen supply rate (OSR) was proportional to air pressure up to 100 kPa, allowing easy control of oxygen supply . Stable nitrite accumulation was observed in the partial nitrification test at a fixed oxygen supply throughout the operation period, indicating that oxygen was consumed only by ammonia oxidizers . Furthermore, it was demonstrated that oxygen utilization efficiency (OUE) in the ammonia oxidation process was nearly 100% after 300 h incubation. Water Sci Technol, 2004, 49(11-12), 237 - 45 Adsorption and biodegradation of azo dye in biofilm processes; Li J et al.; The removal of a common azo dye, acid orange 7 (AO7), in biofilm systems was investigated in this study . The abiotic and biotic fate of AO7 was examined under a variety of operating conditions: aerobic nitrification, anoxic denitrification and anaerobic digestion . A comparison of the performance between biofilm and activated sludge treatment processes was made . The adsorption of AO7 onto biofilm matrix and activated sludge flocs was found to fit the Langmuir equation . However, there is a significant difference in the adsorption capacities between biofilm and activated sludge . AO7 was recalcitrant in both biofilm and activated sludge systems under aerobic conditions . Under anaerobic conditions, AO7 was readily decolorized . AO7 decolorization was also observed under anoxic conditions . However, the presence of nitrate inhibited AO7 decolorization. Water Sci Technol, 2004, 49(11-12), 207 - 14 Treatment of municipal wastewater in a hybrid process using a new suspended carrier with large surface area; Christensson M et al.; An activated sludge/biofilm hybrid process treating municipal wastewater was studied in pilot plant trials . A new type of suspended carrier, with large effective surface area, was employed in the process with the aim of enhancing nitrification . The pilot plant was operated for 1.5 years in five different configurations including pre-denitrification in all five and enhanced biological phosphorus removal in the final two . The wastewater temperature ranged between 11 degrees C and 20 degrees C, and the nominal dissolved oxygen (DO) level was 5-6 mg/L . The nitrification rate obtained on the new carrier within the hybrid stage was in the range of 0.9-1.2 g NH4-N/m2/d corresponding to a volumetric rate of 19-23 g NH4-N/m3/h (total nitrification including nitrification in the suspended solids) . More than 80% of the total nitrification took place on the carrier (and the remainder in the suspended solids) . The nitrification rate was shown to correlate with DO, decreasing when the DO was decreased . The results supported the idea of using the new carrier as a tool to upgrade plants not having nitrification today or improve nitrification in activated sludge processes not reaching necessary discharge levels . The large surface area present for nitrification makes it possible to obtain high nitrification rates within limited volumes . The possibility to keep the total suspended solid content low (< 3 g/L) and avoiding problems with the filament Microthrix parvicella, are other beneficial properties of the hybrid process. Water Sci Technol, 2004, 49(11-12), 163 - 8 Results from the multi-species benchmark problem (BM3) using one-dimensional models; Rittmann BE et al.; The IWA's Biofilm Modeling Task Group created a multi-species benchmark problem in which heterotrophic bacteria, nitrifying bacteria, and inert biomass coexist in a biofilm . Members of the Task Group submitted solutions from nine different one-dimensional models . The most important distinctions among the models were (1) whether the model required a full numerical solution or was solved with a spreadsheet, and (2) the way the biomass types were distributed in the biofilm . The models that protected the slow-growing species by having them accumulate away from the outer surface always had the largest surface coverage by nitrifiers and inerts, but the heterotroph coverage declined to compensate . Coverage by heterotrophs and removal of substrate COD were most strongly affected by dilution from nitrifiers and inerts near the outer surface . Models that did not allow the nitrifiers and inerts to dilute the heterotrophs significantly in the outer layer predicted more removal of COD than did the other models . The choice of the model to use depends on the user's needs and the relative importance of including protection of slow-growing species and/or dilution of fast-growing species. Water Sci Technol, 2004, 49(11-12), 123 - 30 Effect of solid hold-up on nitrite accumulation in a biofilm reactor--molecular characterization of nitrifying communities; Bernet N et al.; Biological ammonium oxidation was carried out in two inverse turbulent bed reactors fed with synthetic mineral wastewater containing a high ammonium concentration (100 mg N-NH4+/L) . Both reactors were started-up and operated in the same conditions except for the solid carrier concentration: the solid hold-up ratios applied, defined as the ratios of static to expanded bed height, were 0.1 and 0.3 in reactors R10 and R30 respectively . These two solid hold-up ratios generate different particle-to-particle collision frequencies and, therefore, detachment forces . The influence of solid hold-up on biofilm growth and nitrifying performance was studied from a macroscopic (i.e . nitrate and/or nitrite production) and microbiological point of view . After 60 days of operation, both reactors contained the same amount of biomass . However, R10 produced only nitrate while nitrite accumulated in R30 . A comparison of microbial populations in the reactors showed that R10 contained both ammonium and nitrite oxidizing populations such as Nitrosomonas and Nitrospira, whereas in R30, ammonium oxidizing populations were much greater than those of nitrite oxidizers . The major ammonium-oxidizing organism was not the same in both reactors. Water Sci Technol, 2004, 49(11-12), 115 - 22 Quantification of biofilms in a sub-surface flow wetland and their role in nutrient removal; Larsen E et al.; Subsurface flow wetlands contain gravel or sand substrates through which the wastewater flows vertically or horizontally . The aims of this study were, firstly, to quantify biofilm development associated with different size gravel in sections of a subsurface flow wetland with and without plants, and secondly, to conduct laboratory experiments to examine the role of biofilms in nutrient removal . Techniques to quantify biofilm included: bacterial cell counts, EPS and total protein extraction . Based on comparative gravel sample volume, only EPS was greater on the smaller 5 mm gravel particles . There was no significant difference between biofilm growth in sections with and without plants . Two vertical flow laboratory-scale reactors, one containing fresh wetland gravel, the other containing autoclaved gravel, were constructed to determine nutrient transformations . The autoclaved gravel in the "sterile" reactor rapidly became colonised with biofilm . Both reactors were dosed with two types of influent . Initially the influent contained 7.25 mg/L NO3-N and 0.3 mg/L NH4-N; the biofilm reactor removed most of the ammonium and nitrite but nitrate concentrations were only reduced by 20% . In the "sterile" reactor there was negligible removal of ammonium and nitrite indicating little nitrification, however nitrate was reduced by 72%, possibly due to assimilatory nitrate reduction associated with new biofilm development . When the influent contained 3 mg/L NO3-N and 16 mg/L NH4-N almost 100% removal and transformation of NH4-N occurred in both reactors providing an effluent high in NO3-N . Organic P was reduced but inorganic soluble P increased possibly due to mineralisation. Water Sci Technol, 2004, 49(11-12), 107 - 13 Experimental study on nitrification in a submerged aerated biofilter; Farabegoli G et al.; The aim of the present work was to evaluate the performance of a semi-pilot scale BAF in order to obtain a highly polished effluent in terms of removal of organic matter, suspended solids and ammonia and to observe the influence of temperature, pH and nitrite accumulation on the nitrification process . The ammonia removal efficiency during summer and winter and the nitrite accumulation in presence of free ammonia were observed . The biomass density was measured at different filter bed heights and the sludge production from the effluent of the backwashing water was evaluated . The results obtained were used to calibrate a mathematical model for the prediction of the ammonia removal profile in the filter bed and of biomass thickness. Water Sci Technol, 2004, 49(11-12), 99 - 105 High nitrification rate at low pH in a fluidized bed reactor with chalk as the biofilm carrier; Tarre S et al.; A typical steady state bulk pH of about 5 was established in a nitrifying fluidized bed with chalk as the only buffer agent . In spite of the low pH, high rate nitrification was observed with the nitrification kinetic parameters in the chalk reactor similar to those of biological reactors operating at pH>7 . Various methods were used to determine the reasons for high rate nitrification at such low pH including (i) determination of bacterial species, (ii) microsensor measurements in the biofilm, and (iii) comparison of nitrification performance at low pH with a non-chalk fluidized bed reactor . Fluorescence in situ hybridization (FISH) using existing 16S rRNA-targeted oligonucleotide probes showed common nitrifying bacteria in the low pH chalk reactor . The prevalent nitrifying bacteria were identified in the Nitrosomonas oligotropha, Nitrosomonas europeae/eutropha, Nitrosospira and Nitrospira related groups, all well known nitrifiers . Microelectrode measurements showed that the pH in the biofilm was low and similar to that of the bulk pH . Finally, reactor performance using a non-chalk biofilm carrier (sintered glass) with the same bacterial inoculum also showed high rate nitrification below pH 5 . The results suggest that inhibition of nitrification at low pH is highly overestimated. Water Sci Technol, 2004, 49(11-12), 91 - 7 Effect of an industrial waste water on the nitrification in fixed-bed biofilm reactors--use of fluorescence in-situ hybridization (FISH); Horsch P et al.; The influence of an industrial waste water containing partly toxic and poorly biodegradable substances on an autotrophic biocenosis was investigated . Nitrifying bacteria were identified using fluorescently-labeled oligonucleotide probes and epifluorescence microscopy . Industrial waste water was used untreated and after ozonation to simulate the effects of indirect discharge to municipal waste water treatment plants . Results were compared to those obtained with acetate as a non-toxic and easily biodegradable substance and a mixture of acetate and pyruvate . The degradation of ammonium and the formation of nitrite and nitrate were measured and compared with the results obtained by fluorescence in-situ hybridization (FISH) . The untreated waste water, containing higher amounts of refractory substances, disturbed nitrification, which was restored after reaching higher elimination of the organic substances . However, it showed only minor effects on the bacterial composition . These findings were similar to those reached by the addition of acetate and pyruvate . On the other hand, the ozonated waste water, showing higher toxicity than the untreated waste water, caused a stabilization in nitrification, but the composition of the population of ammonium-oxidizing bacteria changed significantly . In all cases, nitrite-oxidizing bacteria were only little affected both in activity and abundance. Water Sci Technol, 2004, 49(11-12), 83 - 90 Model-based evaluation of COD influence on a partial nitrification-Anammox biofilm (CANON) process; Hao XD et al.; A model evaluating COD influence on a partial nitrification-Anammox biofilm process is integrated on the basis of heterotrophic growth as described in ASM3, combined with a previously published model for the CANON process . This integrated model can simulate the activities of heterotrophs and autotrophs involved in a biofilm, and interactions between COD oxidation, denitrification, nitrification and Anammox can be evaluated . Simulations indicate that COD in the influent has no important influence on the trends in the partial nitrification-Anammox biofilm process . Besides full COD removal, a total nitrogen removal efficiency of about 90% can be expected for stable biofilm systems . Furthermore, Anammox is a major contributor to the total nitrogen removal in stable biofilm systems and conventional denitrification only takes a share of <20% in the total nitrogen removal. Water Sci Technol, 2004, 49(11-12), 61 - 8 Effects of hydroxylamine on microbial community structure and function of autotrophic nitrifying biofilms determined by in situ hybridization and the use of microelectrodes; Kindaichi T et al.; Effects of hydroxylamine (NH2OH), an intermediate of NH4+ oxidation, on microbial community structure and function of two autotrophic nitrifying biofilms fed with and without NH2OH were analyzed by a 16S rRNA approach and the use of microelectrodes . In the NH2OH-added biofilm, partial oxidation of NH4+ to NO2- was observed, whereas complete oxidation of NH4+ to NO3- was achieved in the control biofilm . In situ hybridization results revealed that no nitrite-oxidizing bacteria (NOB) hybridized with any specific probes were detected in the NH2OH-added biofilm . Thus, the addition of low concentrations of NH2OH (250 microM) completely inhibited the growth of NOB . Phylogenetic analysis of 16S rDNA indicated that the ammonia-oxidizing bacteria (AOB) detected in both biofilms were closely related to Nitrosomonas europaea, and that the clone sequences from both biofilm libraries have more than 99% similarity to each other . However, in situ hybridization results revealed that the addition of NH2OH changed the form of growth pattern of the dominant Nitrosomonas spp . from dense clusters mode to single scattered cells mode . Microelectrode measurements revealed that the average NH4+ consumption rate calculated in the NH2OH-added biofilm was two times higher than that in the control biofilm . This clearly demonstrated that the oxidation of NH4+ was stimulated by NH2OH addition. Water Sci Technol, 2004, 49(11-12), 47 - 52 Trickling filters for upgrading low technology wastewater plants for nitrogen removal; Pearce P; Previous work through the 1990s in the Thames Water region in the UK has demonstrated the ability of the trickling filter process to produce fully nitrified effluents, reliably throughout the year . The original data used for the nitrification model derivations have been reanalysed, to investigate the degree of nitrogen removal across the process . Removals of total nitrogen ranging from 0% to over 50% were observed across the trickling filter process and calculated total nitrogen removals of 26-63% were obtained when primary treatment was included . The degree of nitrogen removal and biological denitrification (excluding cellular assimilation) was found to be strongly influenced by BOD load, irrigation velocity and media size . Regression models were produced which gave good predictive relationships for the data ranges used . The models produced worked for filters used with and without a recirculation of effluent nitrate which suggests that a significant degree of nitrification occurred in areas of high heterotroph activity (BOD removal) . The simplicity and energy efficiency of the trickling filter process, combined with its capacity for full nitrification and partial denitrification, make the process attractive as a combined process used with pond systems in developing countries where nitrogen removal may be required . Some of these synergies have already been developed with the PETRO process in South Africa. Water Sci Technol, 2004, 49(11-12), 27 - 34 Formation mechanism of nitrifying granules observed in an aerobic upflow fluidized bed (AUFB) reactor; Tsuneda S et al.; The influences of trace metals in the wastewater and shear stress by aeration were particularly examined to clarify the formation mechanism of nitrifying granules in an aerobic upflow fluidized bed (AUFB) reactor . It was found that Fe added as a trace element to the inorganic wastewater accumulated at the central part of the nitrifying granules . Another result obtained was that suitable shear stress by moderate aeration (0.07-0.20 L/min/L-bed) promoted granulation . Furthermore, it was successfully demonstrated that pre-aggregation of seed sludge using hematite promoted core formation, leading to rapid production of nitrifying granules . From these results, a nitrifying granulation mechanism is proposed: 1) as a first step, nitrifying bacteria aggregate along with Fe precipitation, and then the cores of granules are formed; 2) as a second step, the aggregates grow to be spherical or elliptical in form due to multiplication of the nitrifying bacteria and moderate shear stress in the reactor, and then mature nitrifying granules are produced . Fluorescence in situ hybridization (FISH) analysis successfully visualized the change in the spatial distribution of nitrifying bacteria in the granules, which supports the proposed granulation mechanism. Curr Microbiol, 2004 Jul, 49(1), 42 - 6 Respirometric activities of heterotrophic and nitrifying populations in aerobic granules developed at different substrate N/COD ratios; Yang SF et al.; Aerobic granules were successfully developed at substrate N/COD ratios ranging from 5/100 to 30/100 by weight . By measuring respective respirometric activities of heterotrophic, ammonia-oxidizing, and nitrite-oxidizing bacteria, it was found that the relative abundance of nitrifying bacteria over heterotrophs in aerobic granules was closely related to the substrate N/COD ratios . Results further showed that the populations of both ammonia and nitrite oxidizers were significantly enriched with the increase of the substrate N/COD ratio, while a decreasing trend of heterotrophic population was observed in the aerobic granules . These seem to indicate that high substrate N/COD ratio favors the selection of nitrifying bacteria in the aerobic granules, while the relative activity of nitrifying population against heterotrophic population evolved until a balance between two populations was reached in the aerobic granular sludge community . Moreover, cell elemental composition was correlated with the shift in microbial populations, e.g., the enriched nitrifying population in the aerobic granules resulted in a high cell nitrogen content normalized to cell carbon content . This study provides a good insight into microbial interaction in aerobic granules. Commun Agric Appl Biol Sci, 2003, 68(2 Pt A), 159 - 62 Nitrate removal in aquaria systems: use of electrochemically generated hydrogen gas as electron donor for denitrification; Grommen R et al.; Nitrate, the end product of the nitrification process, tends to accumulate in aquaria systems . Removal of nitrate in these systems by means of biological denitrification requires the addition of an external electron donor . In this study, the possibilities for using hydrogen gas in aquaria systems as a harmless alternative to other electron donors such as sulphur or reduced organic carbon was investigated . To circumvent safety issues regarding the storage of large volumes of hydrogen gas, in situ generation of hydrogen gas by means of a separate electrochemical cell was chosen . A plug flow reactor filled with polyester cotton wool as carrier material for denitrifying bacteria received hydrogen gas in the headspace . Removal rates of 15 +/- 6 mg N per day were achieved with a hydraulic residence time of 3.3 hours . During the start-up phase nitrite peaks up to 3 mg N per liter were measured in the effluent of the reactor. Commun Agric Appl Biol Sci, 2003, 68(2 Pt A), 93 - 100 Nitrification of ammonia nitrogen high concentration in membrane assisted bioreactor; Zabczynski S et al.; Use of the membrane-assisted bioreactors (MBR) in wastewater treatment can bring a lot of advantages . Usually COD removal achieves level 90% and nitrification of ammonia nitrogen concentrations typical for municipal wastewater performs without any disturbances, what was confirmed by large number of experiments . However, inhibition of nitrification of the high ammonia nitrogen concentration was noticed . In this study, the performance of ammonia-rich wastewater nitrification in membrane-assisted bioreactor (MBR) was examined . With SRT of 40, 32, 24 and 16 days any nitrification inhibition effect wasn't noticed . Ammonia nitrogen removal was around 98% and full nitrification was observed . At the sludge age equal to 12 d the first stage of nitrification was full, but the second stage of nitrification was incomplete . The variation in number and presence of the higher organisms were noticed at the all examined sludge ages . With SRT of 40, 32, 24 and 16 days the free ciliates were prominent organisms . At the sludge age of 12 days the domination of flagellates was observed The kinetic constants of the high-ammonia wastewater nitrification were calculated The average value of Vmax at the sludge age 12, 16 and 24 days was constant (4.7 mg NH4(+)-N/g MLSS h, 4.8 mg NH4(+)-N/g MLSS h and 4.8 mg NH4(+)-N/g MLSS, respectively), but the value of Km rose, when the sludge age increased (6.8 mg NH4(+)-N/L for 12 days, 11.3 mg NH4(+)-N/L for 16 days, 21.6 mg NH4(+)-N/L for 24 days) . At the sludge age 32 and 40 days the increase of Vmax was observed (7.2 mg NH4(+)-N/g MLSS h and 12.5 mg NH4(+)-N/g MLSS h, respectively) and, also, changes of Km (6.8 mg NH4(+)-N/L and 44 mg NH4(+)-N/L, respectively . Concerning the second stage of nitrification value of Vmax decreased with the increase of the sludge age and the average Km varied from 20.3 to 31.3 mg NO2(-)-N/L. Commun Agric Appl Biol Sci, 2003, 68(2 Pt A), 77 - 84 Practical experiences with start-up and operation of a continuously aerated lab-scale SHARON reactor; Van Hulle SW et al.; Partial nitrification techniques, such as the continuously aerated SHARON process, have been denoted for quite a while as very promising for improved sustainability of wastewater treatment . Combination of such a SHARON process with the Anammox process, where ammonium is oxidised with nitrite to nitrogen gas under anoxic conditions, leads to cost-efficient and sustainable nitrogen removal from concentrated streams . In this study practical experiences during start-up and operation of a lab-scale SHARON reactor are discussed . Special attention is given to the start-up in view of possible toxic effects of high ammonium and nitrite concentrations (up to 4000 mgN/l) on the nitrifier population and because the reactor was inoculated with sludge from a SBR reactor operated under completely different conditions . Because of these considerations, the reactor was first operated as a SBR to prevent biomass wash out and to allow the selection of a strong nitrifying population . A month after the inoculation the reactor was switched to normal chemostat operation . As a result the nitrite oxidisers were washed out and only the ammonium oxidisers persisted in the reactor . In this contribution also some practical considerations, such as mixing, evaporation and wall growth, concerning the operation of a continuously aerated SHARON reactor are discussed . These considerations are not trivial, since the reactor will be used for kinetic characterisation and modelling studies . Finally the performance of the SHARON reactor under different conditions is discussed in view of its coupling with an Anammox unit . Full nitrification was proven to be feasible for nitrogen loads up to 1.5 g/l d, indicating the possibility of the SHARON process to treat highly loaded nitrogen streams. J Ind Microbiol Biotechnol . 2004 Jul 28; {Epub ahead of print} Removal of carbonaceous and nitrogenous pollutants from a synthetic wastewater using a membrane-coupled bioreactor; Ghosh S et al.; Two modified Ludzack-Ettinger (MLE)-type membrane-coupled bioreactors (MBRs) were investigated in this study for the purpose of removing both nitrogenous and carbonaceous pollutants from a synthetic wastewater . During the first MBR experiment, removal efficiencies were high (>90%) for chemical oxygen demand (COD) and ammonia, but total nitrogenous pollutant removal efficiency was poor (~25%) . Bacterial community analysis of ammonia oxidizing bacteria (AOB) by a nested PCR-DGGE approach detected two Nitrosomonas-like populations and one Nitrosospira-like population . During the initial portion of the second MBR experiment, COD and ammonia removal efficiencies were similar to the first MBR experiment until the COD of the influent wastewater was increased to provide additional electron donors to support denitrification . Total nitrogen removal efficiencies eventually exceeded 90%, with a hydraulic residence time (HRT) of 24 h and a recirculation ratio of 8 . When the HRT of the MBR experiment was decreased to 12 h, however, ammonia removal efficiency was adversely affected . A subsequent increase in the HRT to 18 h helped improve removal efficiencies for both ammonia (>85%) and total nitrogenous compounds (~70%) . Our research demonstrates that MBRs can be effectively designed to remove both carbonaceous and nitrogenous pollutants . The ability of the microbial community to switch between anoxic (denitrifying) and oxic (nitrifying) conditions, however, represents a critical process constraint for the application of MLE-type MBR systems, such that little benefit is gained compared to conventional designs. Water Res, 2004 Aug-Sep, 38(14-15), 3275 - 86 Evaluating the effect of dissolved oxygen on ammonia-oxidizing bacterial communities in activated sludge; Park HD et al.; The effect of dissolved oxygen (DO) on the communities of ammonia-oxidizing bacteria (AOB) in activated sludge was evaluated in lab-scale and full-scale reactors using the amoA gene as the basis for phylogenetic comparisons . Under controlled laboratory conditions, two chemostats seeded with activated sludge from the same source were operated with high-DO (8.5 mg/L) and low-DO (0.24 and 0.12 mg/L) concentrations for a period of 300 days . At the end of the operation period, the chemostats had enriched AOB communities that belonged to the Nitrosomonas europaea lineage, but were differentiable based on phylogenetic and kinetic analyses . The low-DO chemostat harbored the growth of two different groups within this lineage, differentiable by the amoA sequence comparison and by terminal fragment signatures . The difference in oxygen affinity between high-DO and low-DO enrichments was demonstrated by evaluating the growth kinetics as a function of oxygen concentration . The low-DO enrichment had a higher growth rate at DO concentrations below 4.7 mg/L, but the growth rate significantly decreased at higher DO concentrations, for which the high-DO enrichment experienced higher growth rates . In addition, the dynamic changes in AOB populations in two parallel trains within one full-scale treatment plant were evaluated in response to a significant reduction of DO in one of the treatment trains . Only the train operated with DO concentrations below 1mg/L favored the establishment of a population of AOB related to the N . europaea lineage. Water Res, 2004 Aug-Sep, 38(14-15), 3179 - 88 Nitrification modelling in biofilms under inhibitory conditions; Gheewala SH et al.; A biofilm model has been developed for simulating nitrification in biofilms under inhibitory conditions . Nitrification inhibition has been modelled using uncompetitive inhibition kinetics . Inhibition kinetic experiments were performed by varying the bulk concentrations of inhibitory compound, aniline . Two sets of results were obtained with a nitrifying biofilm that was unacclimated to aniline and another which was acclimated to aniline . Fitting of the nitrification inhibition biofilm model to the experimental results yielded the nitrification inhibition constant, Ki, for aniline . Both the experiments yielded a value of about 3mg/L for Ki, which was similar to that obtained during nitrification inhibition experiments with suspended growth process carried out in an earlier study . The nitrification inhibition biofilm model is general and can be applied to nitrification inhibition with other toxic compounds. J Environ Sci (China), 2004, 16(3), 380 - 3 Alternating shortcut nitrification-denitrification for nitrogen removal from soybean wastewater by SBR with real-time control; Wang SY et al.; A novel treating technology for nitrogen removal from soybean wastewater was studied . The process for nitrogen removal was achieved by alternating aeration and mixing, combined with real-time control strategies . Results showed that the COD and total nitrogen removal rates are more than 90% and 92% at COD and total nitrogen loads of 1.0 - 1.2 kg COD/(kgMLSS x d) and 0.20 - 0.27 kg TN/(kgMLSS x d), respectively . In addition, it could improve sludge settling property . SVI value is less than 70 g/ml during the whole cycles . The method not only may be adapted to treat soybean wastewater with high nitrogen, but also may be applied to treat other high nitrogen wastewater. Environ Toxicol, 2004 Aug, 19(4), 274 - 9 Application of Toxkit microbiotests for toxicity assessment in soil and compost; Dubova L et al.; The potential of Toxkit microbiotests to detect and analyze pollution in agricultural soil and the quality of compost was studied . The toxicity tests used included seed germination biotests using cress salad (Lepidum sativum L.), tomato (Lycopersicum esculentum L.), and cucumber (Cucumis sativus L.), and the Toxkit microbiotests included those with microalgae (Selenastrum capricornutum), protozoa (Tetrahymena thermophila), crustaceans (Daphnia magna, Thamnocephalus platyurus, and Heterocypris incongruens), and rotifers (Brachionus calyciflorus) . Experiments on compost were undertaken in a modified solid-state fermentation system (SSF) and under field conditions (in a windrow) . To promote the composting process, two strains of Trichoderma (Trichoderma lignorum and Trichoderma viride), as well as a nitrification association that regulated the nitrogen-ammonification and nitrification processes were applied . J Synchrotron Radiat, 1998 May 1, 5(Pt 3), 975 - 6 Epub 1998 May 01. Application of a fine thread beam to the structure analysis of a hemihedrally twinned crystal of hydroxylamine oxidoreductase; Igarashi N et al.; Accurate diffraction intensity data have been collected from a twinned P6(3) crystal of the 24-haem protein hydroxylamine oxidoreductase, from a nitrifying chemoautotrophic bacterium Nitrosomonas europaea, using synchrotron radiation at station BL6A of the Photon Factory . Estimation of the twinning fraction and deconvoluted intensity data, including native and heavy-atom derivative data, gave an improved Patterson function . Four diffraction data sets were collected from one crystal and an estimation of the twinning fraction to confirm the phenomena was undertaken . The successfully detwinned data sets were utilized in the structure analysis of the present enzyme . The mechanism of twinned-crystal formation is also discussed. Biotechnol Adv, 2004 Sep, 22(7), 519 - 32 Novel microbial nitrogen removal processes; Khin T et al.; The present-day wastewater treatment practices can be significantly improved through the introduction of new microbial treatment technologies . Recently, several new processes for nitrogen removal have been developed . These new nitrogen removal technologies provide practicable options for treating nitrogen-laden wastewaters . The new processes are based on partial nitrification of ammonium to nitrite combined with anaerobic ammonium oxidation . These processes include the single reactor system for high ammonia removal over nitrite (SHARON) process, which involves part conversion of ammonium to nitrite; the anaerobic ammonium oxidation (ANAMMOX) process, which involves anaerobic ammonium oxidation; and the completely autographic nitrogen removal over nitrite (CANON) process, which involves nitrogen removal within one reactor under oxygen-limited conditions . These new processes target the removal of nitrogen from wastewaters containing significant quantities of ammonium. Water Sci Technol, 2004, 49(10), 41 - 9 Partial ozonation of activated sludge to reduce excess sludge, improve denitrification and control scumming and bulking; Bohler M et al.; Disposal of sewage sludge is forbidden and agricultural use of stabilized sludge will be banned in 2005 in Switzerland . The sludge has to be dewatered, dried, incinerated and the ashes disposed in landfills . These processes are cost intensive and lead also to the loss of valuable phosphate resources incorporated in the sludge ash . The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended . Partial ozonation of the return sludge of an activated sludge system reduces significantly excess sludge production, improves settling properties of the sludge and reduces bulking and scumming . The solubilized COD will also improve denitrification if the treated sludge is recycled to the anoxic zone . But ozonation will partly inhibit and kill nitrifiers and might therefore lead to a decrease of the effective solid retention time of the nitrifier, which reduces the safety of the nitrification . This paper discusses the effect of ozonation on sludge reduction, the operation stability of nitrification, improvement of denitrification and gives also an energy and cost evaluation. J Environ Qual, 2004 Jul-Aug, 33(4), 1440 - 51 Sources and transformations of nitrogen compounds along the Lower Jordan River; Segal-Rozenhaimer M et al.; The Lower Jordan River is located in the semiarid area of the Jordan Valley, along the border between Israel and Jordan . The implementation of the water sections of the peace treaty between Israel and Jordan and the countries' commitment to improve the ecological sustainability of the river system require a better understanding of the riverine environment . This paper investigates the sources and transformations of nitrogen compounds in the Lower Jordan River by applying a combination of physical, chemical, isotopic, and mathematical techniques . The source waters of the Lower Jordan River contain sewage, which contributes high ammonium loads to the river . Ammonium concentrations decrease from 20 to 0-5 mg N L(-1) along the first 20 km of the Lower Jordan River, while nitrate concentrations increase from nearly zero to 10-15 mg N L(-1), and delta(15)N (NO(3)) values increase from less than 5 per thousand to 15-20 per thousand . Our data analysis indicates that intensive nitrification occurs along the river, between 5 and 12 km from the Sea of Galilee, while further downstream nitrate concentration increases mostly due to an external subsurface water source that enters the river. Bioresour Technol, 2004 Nov, 95(2), 209 - 14 Biofilm morphology and nitrification activities: recovery of nitrifying biofilm particles covered with heterotrophic outgrowth; Lee LY et al.; Biofilm processes are commonly used for nitrification . Operationally, a whitish heterotrophic biofilm layer tends to develop onto nitrifying biofilm when it has been exposed to organic carbon-containing wastewater for a prolonged period . The development of a heterotrophic biofilm layer could lead to deterioration in nitrification activities and biofilm morphology . The recovery characteristics, in terms of biofilm morphology and nitrification activities, of deteriorated biofilm particles (i.e . nitrifying biofilm particles covered with heterotrophic outgrowth) were investigated by transferring the deteriorated biofilm particles (from an Ultra-Compact Biofilm Reactor (UCBR) which was part of a packed bed-UCBR system used for treating organic carbon and ammonia-containing wastewater) to a UCBR fed solely with ammonia wastewater (referred to as 'Recovery-UCBR') . At a hydraulic retention time (HRT) of 8.7 h and a sand-carrier concentration of 4.0% (v/v), density of the outer heterotrophic biofilm layer reduced progressively which led to subsequent detachment of this layer from the nitrifying biofilm particles . As a result, morphology of the nitrifying biofilm improved gradually in the Recovery-UCBR . A stable nitrification rate of up to 1.74 kg NH4+-N/m3 d was obtained in the Recovery-UCBR. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2004 Jul, 39(7), 1881 - 90 Treatment of tannery wastewater with high nitrogen content using anoxic/oxic membrane bio-reactor (MBR); Chung YJ et al.; Bench scale membrane bio-reactors were operated to investigate the treatment efficiency of tannery wastewater with high organic and nitrogen contents and the optimum operating conditions were derived . The optimum ratio of the volume of anoxic denitrification tank to aerobic nitrification tank was 50% when denitification/nitrication MBR process was used to treat tannery wastewater . It was also found that supplementation of phosphorus to maintain COD:T-P ratio of 100:1 was needed to achieve the best performance . Under these conditions, the effluent COD and T-N were 160 and 54 mg/L, respectively which satisfied the effluent limits for the tannery wastewater. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2004 Jul, 39(7), 1781 - 90 Promoting nitrification by using functional gel as immobilizing medium under different temperature stimulation patterns; Yuan LJ et al.; Nitrification with nitrifiers immobilized by temperature stimuli-responsive N-isopropylacrylamide-Chlorophyll (NIPA-CH) gel was investigated under several patterns of temperature stimulation, compared with that at constant temperature . The results show that in response to a cyclic temperature stimulus of 32-36 degrees C or 32-34 degrees C with a period of 4 or 2 h, respectively, the gel swelled and shrank reversibly and promoted biological nitrification . But in the case of a cyclic temperature change of 32-36 degrees C with a stimulation cycle of 2 h, nitrite oxidization declined . The results suggested that adequate stimulus facilitated substrate transfer into gels that promoted nitrification in the reactor, but quite frequent swelling and shrinking of the gel squeezed nitrifier out of the gel resulting in washing nitrifier out and declining nitrification . When gels that undergone cyclic temperature stimuli began to swell at 32 degrees C, oxygen consumption of nitrifiers in the gels was more than that of nitrifiers in the gels at constant temperature of 32 degrees C all the time, but when gels of two reactors shrank at 36 degrees C, their oxygen consumption reduced and there was almost no difference between them regardless of their undergone temperature stimuli once or not . Practical application of nitrifier immobilized by NIPA-CH gel in wastewater treatment was also discussed. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2004 Jul, 39(7), 1757 - 65 Effects of fill time on the fractal dimension and size of floc for SBR treating low C/N ratio wastewater; Moon BH et al.; The aim of this study was to investigate the effects of fill time of influent on the physical characteristics of biological floc for sequencing batch reactor (SBR) treating low C/N ratio wastewater . The fractal dimension and size of floc were measured for characterizing floc . The fractal dimension of floc was analyzed by using Small Angle Laser Light Scattering (SALLS) method . SBR with short fill time showed higher removal efficiencies of COD, BOD, T-N, and T-P than with long fill time . Larger floc size and fractal dimension were generated at SBR with short fill time . Short fill time generated the sludge with better settling and thickening properties . Alternating anaerobic and aerobic condition in the cycle also affected the floc size and fractal dimension . The floc size decreased under anaerobic phase, and floc size increased under aerobic phase . During fill time, the fractal dimension of floc decreased . As the fill stop, the fractal dimension of floc increased . Therefore, the fill time condition more affected the fractal dimension of floc . More efficient nitrification and phosphorus release were observed during a cycle with short fill time operation. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2004 Jul, 39(7), 1667 - 80 Nitrogen removal via nitrite from seawater contained sewage; Peng Y et al.; Under the control of both pH and the concentration of free ammonia (FA), the nitrification-denitrification via nitrite pathway was accomplished in SBR to achieve enhanced biological nitrogen removal from seawater contained wastewater, which is used to flush toilet, under relatively high salinity . Several parameters including salinity, temperature, pH, and NH4+-N loading rate were studied to evaluate their effects . The results indicate that at different salinity the nitrogen removal efficiency is relative to ammonia-nitrogen loading rate . The nitrogen removal efficiency reaches above 90% when the NH4+-N loading does not exceed 0.15 kg NH4+-N/kg MLSS d . With the salinity increasing, the ammonia-nitrogen loading rate should be lowered to obtain high removal efficiency . The evaluation of temperature effect shows that nitrogen removal efficiency is promoted twice when reaction temperature is elevated from 20 to 30 degrees C . Moderately high pH in the range of 7.5-8.5 has advantage to achieve effective nitrification-denitrification via nitrite, the process of which is caused by the selective inhibition of free ammonia (FA). Chemosphere, 2004 Aug, 56(7), 653 - 8 Preliminary ecotoxicological characterization of a new energetic substance, CL-20; Gong P et al.; A new energetic substance hexanitrohexaazaisowurtzitane (or CL-20) was tested for its toxicities to various ecological receptors . CL-20 (epsilon-polymorph) was amended to soil or deionized water to construct concentration gradients . Results of Microtox (15-min contact) and 96-h algae growth inhibition tests indicate that CL-20 showed no adverse effects on the bioluminescence of marine bacteria Vibrio fischeri and the cell density of freshwater green algae Selenastrum capricornutum respectively, up to its water solubility (ca . 3.6 mg l(-1)) . CL-20 and its possible biotransformation products did not inhibit seed germination and early seedling (16-19 d) growth of alfalfa (Medicago sativa) and perennial ryegrass (Lolium perenne) up to 10,000 mg kg(-1) in a Sassafras sandy loam soil (SSL) . Indigenous soil microorganisms in SSL and a garden soil were exposed to CL-20 for one or two weeks before dehydrogenase activity (DHA) or potential nitrification activity (PNA) were assayed . Results indicate that up to 10,000 mg kg(-1) soil of CL-20 had no statistically significant effects on microbial communities measured as DHA or on the ammonium oxidizing bacteria determined as PNA in both soils . Data indicates that CL-20 was not acutely toxic to the species or microbial communities tested and that further studies are required to address the potential long-term environmental impact of CL-20 and its possible degradation products. Indian J Exp Biol, 2004 Mar, 42(3), 314 - 8 Optimum growth requirements of nitrifying consortia developed from treated sewage; Ramachandran K et al.; The optimum growth requirements of two nitrifying consortia developed from treated sewage by enrichment technique were determined by a series of experiments . There was total inhibition of nitrification at above 2.75 g l(-1) NH4(+)- N and 2.5 g l(-1) NO2(-)-N and the ammonia oxidizing consortium preferred a pH at 8.5 and the nitrite oxidizing consortium a pH of 7.5 as the optima for nitrification . Optimum temperatures were between 20 degrees and 30 degrees C for both the groups . As the rate of airflow was increased from 1 to 7 l/min, the build-up of NO2(-)-N increased 10-fold and the consumption of NO2(-)-N increased by a factor of 28.8 implying that the ammonia oxidizing consortium in a bioreactor required three times more aeration than that for nitrite oxidizers for expressing their full nitrifying potential . These data directly contribute for developing a fermentation process for the mass production of nitrifiers as well as for designing bioreactors for nitrifying sewage. Nature, 2004 Jul 1, 430(6995), 98 - 101 Nitrification by plants that also fix nitrogen; Hipkin CR et al.; Nitrification is a key stage in the nitrogen cycle; it enables the transformation of nitrogen into an oxidized, inorganic state . The availability of nitrates produced by this process often limits primary productivity and is an important determinant in plant community ecology and biodiversity . Chemoautotrophic prokaryotes are recognized as the main facilitators of this process, although heterotrophic nitrification by fungi may be significant under certain conditions . However, there has been neither biochemical nor ecological evidence to support nitrification by photoautotrophic plants . Here we show how certain legumes that accumulate the toxin, 3-nitropropionic acid, generate oxidized inorganic nitrogen in their shoots, which is returned to the soil in their litter . In nitrogen-fixing populations this 'new' nitrate and nitrite can be derived from the assimilation of nitrogen gas . Normally, the transformation of elemental nitrogen from the atmosphere into a fixed oxidized form (as nitrate) is represented in the nitrogen cycle as a multiphasic process involving several different organisms . We show how this can occur in a single photoautotrophic organism, representing a previously undescribed feature of this biogeochemical cycle. J Environ Qual, 2004 May-Jun, 33(3), 852 - 60 Nitrite formation and nitrous oxide emissions as affected by reclaimed effluent application; Master Y et al.; The effect of irrigation with reclaimed effluent (RE) (after secondary treatment) on the mechanisms and rates of nitrite formation, N2O emissions, and N mineralization is not well known . Grumosol (Chromoxerert) soil was incubated for 10 to 14 d with fresh water (FW) and RE treated with 15NO3- and 15NH4+ to provide a better insight on N transformations in RE-irrigated soil . Nitrite levels in RE-irrigated soil were one order of magnitude higher than in FW- irrigated soil and ranged between 15 to 30 mg N kg(-1) soil . Higher levels of NO2- were observed at a moisture content of 60% than at 70% and 40% w/w . Nitrite levels were also higher when RE was applied to a relatively dry Grumosol (20% w/w) than at subsequent applications of RE to soil at 40% w/w . Isotopic labeling indicated that the majority of NO2 was formed via nitrification . The amount of N2O emitted from RE-treated Grumosol was double the amount emitted from FW treatments at 60% w/w . Nitrification was responsible for about 42% of the emissions . The N20 emission from the RE-treated bulk soil (passing a 9.5-mm sieve) was more than double the amount formed in large aggregates (4.76-9.5 mm in diameter) . No dinitrogen was detected under the experimental conditions . Results indicate that irrigation with secondary RE stimulates nitrification, which may enhance NO3 leaching losses . This could possibly be a consequence of long-term exposure of the nitrifier population to RE irrigation . Average gross nitrification rate estimates were 11.3 and 15.8 mg N kg(-1) soil d(-1) for FW- and RE-irrigated bulk soils, respectively . Average gross mineralization rate estimates were about 3 mg N kg(-1) soil d(-1) for the two water types. J Environ Qual, 2004 May-Jun, 33(3), 837 - 43 Effect of Cry3Bb transgenic corn and tefluthrin on the soil microbial community: biomass, activity, and diversity; Devare MH et al.; Transgenic Bt corn expressing the Cry3Bb insecticidal protein active against corn rootworm (CRW) (Diabrotica spp.; Coleoptera: Chrysomelidae) was released for commercial use in 2003 and is expected to be widely adopted . Yet, the direct and indirect risks to soil microorganisms of growing this CRW-resistant Bt corn versus applying insecticides to control the rootworm have not been assessed under field conditions . The effects of CRW Bt corn and the insecticide tefluthrin {2,3,5,6-tetrafluoro-4-methylbenzyl (Z)-(1RS)-cis-3-(2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-dimethylcyclopropanecarboxylate} on soil microbial biomass, activity (N mineralization potential, short-term nitrification rate, and soil respiration), and bacterial community structure as determined by terminal restriction fragment length polymorphism (T-RFLP) analysis were assessed over two seasons in a field experiment . Bt corn had no deleterious effects on microbial activity or bacterial community measures compared with the non-transgenic isoline . The T-RFLP analysis indicated that amplifiable bacterial species composition and relative abundance differed substantially between years, but did not differ between rhizosphere and bulk soils . The application of tefluthrin also had no effect on any microbial measure except decreased soil respiration observed in tefluthrin-treated plots compared with Bt and non-transgenic isoline (NoBt) plots in 2002 . Our results indicate that the release of CRW Bt corn poses little threat to the ecology of the soil microbial community based on parameters measured in this study. Environ Sci Technol, 2004 Jun 1, 38(11), 3176 - 83 Multipopulation model of membrane-aerated biofilms; Shanahan JW et al.; Biofilms cultivated on oxygen-filled gas-permeable membranes grow differently than conventional biofilms, as the chemical species required for growth diffuse from different sides of the biofilm . Oxygen is delivered directly to the base of the biofilm by the membrane, while organic substrates and other soluble nutrients are provided to the upper surface of the biofilm via the water in which the membranes are immersed . This counterdiffusion of nutrients results in a growth environment very different from that of conventional biofilms that receive both oxygen and other nutrients from the water . In recent years, membrane-supported biofilms have been shown to simultaneously remove chemical oxygen demand (COD) and inorganic nitrogen from wastewater in laboratory studies . Several investigators have developed computer models of these biofilms, but they have all focused on a single population of aerobic bacteria . While these models are useful in characterizing the behavior of these biofilms in pure cultures, they are not useful in modeling the behavior of the biofilms in mixed cultures such as those found in wastewater treatment . In this study, a multipopulation biofilm model was developed that includes aerobic heterotrophs, nitrifiers, denitrifiers, and acetoclastic methanogens . The model was constructed with Aquasim software and can predict the COD and inorganic nitrogen removal behavior observed previously in experimental studies . In this paper we present examples of predicted biofilm behavior and compare the results of this multiple-population model with the single-population models published previously . In addition, the behavior of the biofilm is discussed in terms of application to wastewater treatment. Environ Sci Technol, 2004 Jun 1, 38(11), 3092 - 7 Adaptation of soil biological nitrification to heavy metals; Rusk JA et al.; The adaptive response of soil biological nitrification to Zn and Pb was assessed using an in situ method we have developed . The method is based on reinoculating a sterilized metal contaminated soil with the same soil that is either uncontaminated or has been incubated with metal . This approach excludes the potentially confounding effects of metal aging reactions in soils . We found added Zn concentrations which gave rise to a decrease in nitrification to 50% that of the uncontaminated soil (i.e . EC50) of 210 mg/kg for communities not previously exposed to Zn and 850 mg/kg for communities exposed to Zn for 17 months, indicating that significant adaptation of the community to Zn had occurred . Similarly, this protocol was able to demonstrate adaptation of soil biological nitrification to Pb, with EC50 values of 1960 and 3150 mg/kg for the unexposed and exposed treatments, respectively . Exposure of unadapted and adapted microbial communities to a combination of Zn and Cd showed that the presence of Cd did not lead to greater toxicity in either community . Adapted communities were not more sensitive to decreases in soil pH than unadapted communities . Prior exposure to Zn was found to confer significantly greater tolerance of the community to Pb . Prior exposure to Pb similarly conferred significantly greater tolerance of the community to Zn . Implications of the adaptive capacity of soil microbes to the development of critical threshold values for heavy metals in soil based on ecotoxicity assessments are discussed. Ecotoxicol Environ Saf, 2004 Jul, 58(3), 300 - 13 Toxicity assessment of contaminated soils from an antitank firing range; Robidoux PY et al.; Explosives are released into the environment at production and processing facilities, as well as through field use . These compounds may be toxic at relatively low concentrations to a number of ecological receptors . A toxicity assessment was carried out on soils from an explosive-contaminated site at a Canadian Forces Area Training Center . Toxicity studies on soil organisms using endpoints such as microbial processes (potential nitrification activity, dehydrogenase activity, substrate-induced respiration, basal respiration), plant seedling and growth (Lactuca sativa and Hordeum vulgare), and earthworm (Eisenia andrei) growth and reproduction were carried out . Results showed that 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) was the principal polynitro-organic compound measured in soils . Soils from the contaminated site decreased microbial processes and earthworm reproduction; whereas plant growth was not significantly reduced . Toxicity to aquatic organisms and genotoxicity were also assessed on soil elutriates using Microtox (Vibrio fischeri), growth inhibition of algae (Selenastrum capricornutum), and SOS Chromotest (Escherichia coli) . Results indicated that soil elutriates were generally not toxic to bacteria (Microtox) and algae . However, genotoxicity was found in a number of soil elutriate samples . Thus, the explosive-contaminated soils from the antitank firing range may represent a hazard for the soil organisms . Nevertheless, the global toxicity might have partially resulted from HMX as well as from other (not identified) contaminants such as heavy metals. J Biotechnol, 2004 Jul 15, 111(2), 111 - 20 Expression of amoA mRNA in wastewater treatment processes examined by competitive RT-PCR; Aoi Y et al.; The expression of ammonia monooxygenase encoding mRNA (amoA mRNA) in a wastewater treatment process was analyzed in an attempt to propose an effective target for the monitoring of nitrifying bacteria in engineered systems or natural environments . The quick response (1-2 h) of amoA mRNA transcription to the recovery of ammonia oxidation activity induced by the sudden exposure to ammonia was observed in a short-time batch-mode incubation whereas the amount of amoA DNA did not markedly change during the incubation under any conditions . In the continuous feeding-operation, amoA mRNA level dynamically changed in response to the change in the surrounding environmental conditions and increase in ammonia oxidation rate . Although, amoA mRNA level did not quickly respond to the decrease in ammonia oxidation activity, it decreases over long time scales . These results suggest that the profiles of amoA mRNA expression can be used as an indicator of the ammonia oxidation activity. J Environ Manage, 2004 Jul, 71(4), 345 - 9 Biological treatment of tannery wastewater in the presence of chromium; Farabegoli G et al.; Experiments were carried out to determine the feasibility of treating tannery wastewater containing chromium, an inhibiting compound, with sequencing batch reactors (SBR) . The maximum chromium concentration tolerated by microorganisms was determined through aerobic and anoxic batch experiments, and the biomass inhibition process was analyzed in a lab scale reactor at increasing chromium concentrations . The results obtained, in batch experiments and in the SBR reactor, have demonstrated that chromium addition had less influence on the denitrification bacteria than on the nitrification bacteria . In addition, it was observed that nitrification and denitrification rates, at the same chromium concentration, were higher in the SBR reactor than in batch experiments with unacclimated biomass . Experimental results confirm that sequencing batch reactors are able to produce a more resistant biomass, which acclimates quickly to inhibiting conditions . A large amount of chromium was found in the sludge from the reactor, while the effluent was devoid of the inhibiting metal. Syst Appl Microbiol, 2004 May, 27(3), 271 - 8 Nitrification and anammox with urea as the energy source; Sliekers AO et al.; Urea is present in many ecosystems and can be used as an energy source by chemolithotrophic aerobic ammonia oxidizing bacteria (AOB) . Thus the utilization of urea in comparison to ammonia, by AOB as well as anaerobic ammonia oxidizing (Anammox) bacteria was investigated, using enrichments cultures, inoculated with activated sludge, and molecular ecological methods . In batch enrichment cultures grown with ammonia a population established in 2 weeks, which was dominated by halophilic and halotolerant AOB as determined by fluorescence in situ hybridization (FISH) experiments, with the 16S rRNA targeting oligonucleotide probe NEU . In other batch enrichment cultures using urea, the AOB population was assessed by PCR amplification, cloning and phylogenetic analysis of amoA and ribosomal 16S rRNA genes . While only one of the 48 16S rRNA gene clones could be identified as AOB (Nitrosomonas oligotropha), the amoA approach revealed two more AOB, Nitrosomonas europaea and Nitrosomonas nitrosa to be present in the enrichment . FISH analysis of the enrichment with probe NEU and newly designed probes for a specific detection of N . oligotropha and N . nitrosa related organisms, respectively, showed that N . oligotropha-like AOB formed about 50% of the total bacterial population . Also N . nitrosa (about 15% of the total population) and N . europaea (about 5% of the total population) were relatively abundant . Additionally, continuous enrichments were performed under oxygen limitation . When ammonia was the energy source, the community in this reactor consisted of Anammox bacteria and AOB hybridizing with probe NEU . As the substrate was changed to urea, AOB related to N . oligotropha became the dominant AOB in this oxygen limited consortium . This resulted in a direct conversion of urea to dinitrogen gas, without the addition of organic carbon. Environ Technol, 2004 Apr, 25(4), 423 - 31 Improving the biological nitrogen removal process in pharmaceutical wastewater treatment plants: a case study; Torrijos M et al.; The Biological Nitrogen Removal (BNR) process of some pharmaceutical wastewater treatment plants has important operational problems . This study shows that, in order to solve these problems, the design of industrial BNR processes should start by analysing three key parameters: the characteristics of the wastewater load, the determination of the maximum TKN removal rate and the detection of toxic or inhibitory compounds in the wastewater . A case study of this analysis in pharmaceutical wastewater is presented here . In this case, the conventional TKN analytical method does not make an accurate characterisation of the wastewater load because it measures a concentration of 100 mg TKN l(-1) whereas the real concentration, determined with a modified TKN analytical method, is 150-500 mg TKN l(-1) . Also, the TKN removal of the treatment system is insufficient in some periods because it falls below legal requirements . This problem might be a consequence of the wrong characterisation of wastewater during the design process . The maximum TKN removal at 27 degrees C (24 mg N g VSS(-1) d(-1) or 197 mg N l(-1) d(-1)) was evaluated in a pilot-scale plant . This value is six times greater than the average NLR applied in the full-scale plant . Finally, some of the components of the wastewater, such as p-phenylenediamine, might have inhibitory or toxic effects on the biological process . P-phenylenediamine causes a large decrease in the nitrification rate . This effect was determined by respirometry . This methodology shows that the effect is mainly inhibitory with a contact time of 30 min and if the contact time is longer, 14 hours, a toxic effect is observed. Environ Technol, 2004 Apr, 25(4), 413 - 22 The effect of volatile fatty acids on the nitrification of a saline effluent; Delgado A et al.; Anaerobically produced volatile fatty acids (VFA) may affect the nitrification yield . The effect of the type of VFA (acetic, propionic and butyric acid) on nitrification of a saline (24 g NaCl l(-1)) medium was studied . Nitritation (40 mg N-NH4+ l(-1)) and nitratation (100 mg N-NO2- l(-1) were assessed in batch cultures fed with different VFA (32 mg TOC l(-1)) . The effect of increasing VFA concentrations on nitrification was studied in batch reactors fed with an initial concentration of 40 mg N-NH4+ l(-1) and C/N ratios of 0, 2, 4, 8 and 16 as well as in a continuous mixed flow reactor operated at 30 degrees C and pH 7.5 and fed with 500 mg N-NH4+ l(-1) and 500, 1000, 2000, and 4000 mg TOC l(-1) . Nitritation and nitratation rates were decreased by organic matter; inhibition increased with the VFA size . A non-competitive inhibition model fitted the experimental data on nitrification rate reduction at increasing acetic add concentrations; inhibition constants were 685 mg acetic acid l(-1) for ammonia oxidation and 74.3 mg acetic acid l(-1) for nitrite oxidation . The continuous reactor's nitrifying ability decreased from 82% to 40% at C/N ratios 1 and 4, respectively . Loss of nitrification, but a 50% ammonia removal was found at a C/N of 8 . It was concluded that the nitrification rate reduction is proportional to the VFA molecular weight and that an increase in VFA concentration diminishes the nitrifying ability due to kinetic limitations. J Bacteriol, 2004 Jul, 186(13), 4417 - 21 Nitrosomonas europaea expresses a nitric oxide reductase during nitrification; Beaumont HJ et al.; In this paper, we report the identification of a norCBQD gene cluster that encodes a functional nitric oxide reductase (Nor) in Nitrosomonas europaea . Disruption of the norB gene resulted in a strongly diminished nitric oxide (NO) consumption by cells and membrane protein fractions, which was restored by the introduction of an intact norCBQD gene cluster in trans . NorB-deficient cells produced amounts of nitrous oxide (N2O) equal to that of wild-type cells . NorCB-dependent activity was present during aerobic growth and was not affected by the inactivation of the putative fnr gene . The findings demonstrate the presence of an alternative site of N2O production in N . europaea. Huan Jing Ke Xue, 2004 Mar, 25(2), 94 - 7 {Inhibition of aromatics on ammonia-oxidizing activity of sediment}; Dong CH et al.; The inhibition of 24 aromatics on ammonia-oxidizing activity of nitrifying bacteria in sediment was measured . The effects of the kind, number and position of substituted groups on ammonia-oxidizing activity of nitrifying bacteria were discussed . The inhibition of mono-substituted benzenes on ammonia-oxidizing activity of nitrifying bacteria were in order of -OH > -NO2 > -NH2 > -Cl > -CH3 > -H . The position of substituted groups of di-substituted benzenes also affected the inhibition, and the inhibitions of dimethylbenzenes(xylene) were in order of meta-> ortho-> para- . The increase in number of substituted group on benzene-ring enhanced the inhibition of aromatics studied in this study on nitrifying bacteria . There was a linear relationship between inhibition (IC50, mumol.L-1) of aromatics on ammonia-oxidizing activity and total electronegativity (sigma E) of aromatics: lgIC50 = 14.72 - 0.91 sigma E. Microbiology, 2004 Jun, 150(Pt 6), 1869 - 79 The transcription of the cbb operon in Nitrosomonas europaea; Wei X et al.; Nitrosomonas europaea is an aerobic ammonia-oxidizing bacterium that participates in the C and N cycles . N . europaea utilizes CO(2) as its predominant carbon source, and is an obligate chemolithotroph, deriving all the reductant required for energy and biosynthesis from the oxidation of ammonia (NH(3)) to nitrite () . This bacterium fixes carbon via the Calvin-Benson-Bassham (CBB) cycle via a type I ribulose bisphosphate carboxylase/oxygenase (RubisCO) . The RubisCO operon is composed of five genes, cbbLSQON . This gene organization is similar to that of the operon for 'green-like' type I RubisCOs in other organisms . The cbbR gene encoding the putative regulatory protein for RubisCO transcription was identified upstream of cbbL . This study showed that transcription of cbb genes was upregulated when the carbon source was limited, while amo, hao and other energy-harvesting-related genes were downregulated . N . europaea responds to carbon limitation by prioritizing resources towards key components for carbon assimilation . Unlike the situation for amo genes, NH(3) was not required for the transcription of the cbb genes . All five cbb genes were only transcribed when an external energy source was provided . In actively growing cells, mRNAs from the five genes in the RubisCO operon were present at different levels, probably due to premature termination of transcription, rapid mRNA processing and mRNA degradation. Bioresour Technol, 2004 Sep, 94(3), 229 - 38 Microbial mats for multiple applications in aquaculture and bioremediation; Bender J et al.; Microbial mats occur in nature as stratified communities of cyanobacteria and bacteria, but they can be cultured on large-scale and manipulated for a variety of functions . They are complex systems, but require few external inputs . The functional uses of mats broadly cover the areas of aquaculture and bioremediation . Preliminary research also points to promising uses in agriculture and energy production . Regarding aquaculture, mats were shown to produce protein, via nitrogen fixation, and were capable of supplying nutrition to tilapia (Oreochromis niloticus) . Current research is examining the role of mats in the nitrification of nutrient-enriched effluents from aquaculture . Most research has addressed bioremediation, within which two majors categories of contaminants were examined: metals and radionuclides, and organic contaminants . Mats sequester or precipitate metals/radionuclides by surface absorption or by conditioning the surrounding chemical environment, thus bioconcentrating the metal/radionuclide in a small volume . Organic contaminants are degraded and may be completely mineralized . For agriculture mats hold promise as a soil amendment and nitrogen fertilizer . The use of mats in biohydrogen production has been verified, but is in a preliminary phase of development . We propose a comprehensive closed system based on microbial mats for aquaculture and waste management. Environ Technol, 2004 Mar, 25(3), 365 - 71 Transportation of reclaimed wastewater through a long pipe: inhibition of sulphide production by nitrite from the secondary treatment; Delgado S et al.; The agricultural reuse of reclaimed wastewater has become a necessity in places with water shortages . Frequently, this involves the operation of long transportation pipelines, like in the South Tenerife reuse system, whose main element is a completely filled 61 km long gravity pipe in cast iron . Sulphide generation, which could contribute to pipe corrosion, is a usual process taking place during transportation if anaerobic conditions prevail . In the Wastewater Treatment Plant of Santa Cruz (Tenerife, Spain) a partial nitrification process was achieved by increasing the mean residence time through the aeration step at low dissolved oxygen concentration . Such conditions, combined with the right temperature and a free ammonia concentration above 1 mg l(-1), inhibited nitratation and favoured nitritation, which led to concentrations of NO2-N above 8 mg l(-1) in the secondary effluent . During the transportation, nitrite inhibited the appearance of anaerobic conditions, and, consequently, no sulphide generation occurred . At the same time, a nitrite reduction process took place with a first order kinetics and a rate coefficient of 0.052 h(-1)' at 25 degrees C . A parallel behaviour between the nitrite depletion and the oxidation-reduction potential evolution along the pipeline was also observed. Environ Technol, 2004 Mar, 25(3), 273 - 82 Quantification of nitrification and denitrification rates in algae and duckweed based wastewater treatment systems; Zimmo OR et al.; Nitrification and denitrification rates at three different depths (0.1, 0.45 and 0.9m from the water surface) in two series of four algae and duckweed based waste stabilisation ponds (ABPs and DBPs) were measured using nitrate reduction techniques in laboratory batch incubations . The effects of temperature and BOD5 loading were investigated . In situ measurements over the ponds' depths were also done for confirmation of laboratory results . Higher dissolved oxygen (DO) concentrations in ABPs, especially during the warm season, favoured higher nitrification in ABPs over DBPs . Organic surface loading also affected the rate of nitrification in the ponds . Nitrification rates did not increase along the treatment line despite the decrease in organic matter content . Adsorption of nitrifiers to available suspended particles and subsequent sedimentation was assumed to be the main reason for the similar nitrification rates in most ponds . In both systems, the presence of DO in the water