Water Sci Technol, 2001, 44(2-3), 181 - 8 Septage dewatering in vertical-flow constructed wetlands located in the tropics; Koottatep T et al.; Constructed wetlands (CWs) have been proven to be an effective low-cost treatment system, which utilizes the interactions of emergent plants and microorganisms in the removal of pollutants . CWs for wastewater treatment are ndrmally designed and operated in horizontal-flow patterns, namely, free-water surface or subsurface flow, while a vertical-flow operation is normally used to treat sludge or septage having high solid contents . In this study, three pilot-scale CW beds, each with a surface area of 25 m2, having 65 cm sand-gravel substrata, supported by ventilated-drainage system and planting with narrow-leave cattails (Typha augustifolia), were fed with septage collected from Bangkok city, Thailand . To operate in a vertical-flow mode, the septage was uniformly distributed on the surface of the CW units . During the first year of operation, the CWs were operated at the solid loading rates (SLR) and application frequencies of, respectively, 80-500 kg total solid (TS)/m2 x yr and 1-2 times weekly . It was found that the SLR of 250 kg TS/m2 x yr resulted in the highest TS, total chemical oxygen demand (TCOD) and total Kjeldahl nitrogen (TKN) removal of 80, 96 and 92%, respectively . The TS contents of the dewatered septage on the CW beds were increased from 1-2% to 30-60% within an operation cycle . Because of the vertical-flow mode of operation and with the effectiveness of the ventilation pipes, there were high degrees of nitrification occurring in the CW beds . The nitrate (NO3) contents in the CW percolate were 180-250 mg/L, while the raw septage had NO3 contents less than 10 mg/L . Due to rapid flow-through of the percolates, there was little liquid retained in the CW beds, causing the cattail plants to wilt, especially during the dry season . To reduce the wilting effects, the operating strategies in the second year were modified by ponding the percolate in the CW beds for periods of 2 and 6 days prior to discharge . This operating strategy was found beneficial not only for mitigating plant wilting, but also for increasing N removal through enhanced denitrification activities in the CW beds . During these 2 year operations, the dewatered septage was not removed from the CW beds and no adverse effects on the septage dewatering efficiency were observed. Water Sci Technol, 2001, 44(2-3), 171 - 9 Biological nitrogen removal from industrial wastewater discharged from metal recovery processes; Hirata A et al.; The wastewater generated from the processes of recovering precious metals from industrial wastes contains high concentrations of acids and alkalis such as nitric acid and aqueous ammonia, and of salts such as sodium chloride and sodium sulfate . Biological nitrogen removal from this wastewater was attempted by using a circulating bioreactor system equipped with an anaerobic packed bed and an aerobic three-phase fluidized bed . As a result of acclimating microorganisms with change of the hydraulic residence time, this system effectively removed nitrogen from diluted wastewater (T-N: from 2,000 to 4,000 g/m3), such that the total nitrogen concentration in the effluent met the sewage discharge control criteria in Japan (240 g/m3) . The removal ratio of total nitrogen was 90% to 98% and that of ammonia was 80% to 92% . In addition, the characteristic equations for biological treatment were applied to this system on the assumption that both reactions of denitrification in the anaerobic reactor and nitrification in the aerobic reactor can be approximated to a first-order reaction . This simplified approach successfully led to a new analytical method for simulating the optimum volume ratio of anaerobic reactor to aerobic reactor for minimizing the total hydraulic residence time. Water Sci Technol, 2001, 44(2-3), 163 - 70 Process using DO and ORP signals for biological nitrification and denitrification: validation of a food-processing industry wastewater treatment plant on boosting with pure oxygen; Mauret M et al.; The simultaneous removal of carbonaceous and nitrogenous pollution by the activated sludge process is becoming common in industrial and municipal wastewater treatment plants . An oxygenation monitoring process has been developed, which is based on the dynamic analysis of ORP and DO signals and allows the detection of specific characteristic points at the end of the biological nitrification and denitrification . The aim of this study is to validate this process in a food-processing industry WWTP (slaughterhouse) having large variations of carbonaceous and nitrogenous loads . In order to treat during the peak period, pure oxygen is used . The first part of the study provides a precise diagnosis of the WWTP operation by the analysis of the ORP and DO signals . It is particularly easy to estimate the level of nitrogen treatment actually achieved and the oxygen requirements, and to detect the over- or under-oxygenated phases . Thanks to the monitoring process, the aerobic period of each cycle is reduced to the optimal duration, providing a reduction of 30% on the energy consumption compared to a traditional schedule . We have demonstrated that the use of pure oxygen associated with the existing air system is particularly relevant for the peak period . The revamping of an existing plant to simultaneously treat the carbon and the ammonia in the same basin is now technically feasible. Annu Rev Microbiol, 2001, 55, 485 - 529 Ammonia-oxidizing bacteria: a model for molecular microbial ecology; Kowalchuk GA et al.; The eutrophication of many ecosystems in recent decades has led to an increased interest in the ecology of nitrogen transformation . Chemolitho-autotrophic ammonia-oxidizing bacteria are responsible for the rate-limiting step of nitrification in a wide variety of environments, making them important in the global cycling of nitrogen . These organisms are unique in their ability to use the conversion of ammonia to nitrite as their sole energy source . Because of the importance of this functional group of bacteria, understanding of their ecology and physiology has become a subject of intense research over recent years . The monophyletic nature of these bacteria in terrestrial environments has facilitated molecular biological approaches in studying their ecology, and progress in this field has been rapid . The ammonia-oxidizing bacteria of the beta-subclass Proteobacteria have become somewhat of a model system within molecular microbial ecology, and this chapter reviews recent progress in our knowledge of their distribution, diversity, and ecology. Biol Sci Space, 1999 Dec, 13(4), 351 - 60 Application of nitrifying and denitrifying processes to waste management of aquatic life support in space Shimura R, Kumagai H, Kozu H, Motoki S, Ijiri K, Nagaoka S. Since a biological filter with nitrifying bacteria was firstly applied to aquatic animal experiments in IML-2 mission, the reactor system has been further studied to combine both nitrifying and denitrifying reactions under aerobic environment allowing an efficient removal of inorganic nitrogen from animal wastes . The isolated denitrifying bacteria had an activity under aerobic condition with rice straw providing a metabolic carbon source for the reaction . The advantage of the aerobic biological filter having both nitrifying and denitrifying activities may allow to reduce the size of the life support system and also for its manageability . The paper reports characteristics of the biological filter systems used for the IML-2 mission and the improved combined filter system having both nitrifying and denitrifying activities, and discuss its application to space experiments. Biol Sci Space, 1999 Dec, 13(4), 348 - 50 R&D of long-term life support system by using electrochemically activated biofilm reactor of aquatic animals for space examinations; Ichikawa K et al.; We have developed the long-term life support system that enables the experiment of aquatic animals breeding for 90 days or more for the future experiments in orbit . In order to enable long-term breeding of wide aquatic animals, it is necessary to remove nitrate produced by biological nitrification . Then, we examined a denitrification method to use an electrochemical reaction of biofilm-electrode reactor . In this research, we have not kept the aquatic animals actually but imitated breeding of five goldfish . The ammonia of about 250 ppm was added in breeding water through 90 days . As a result, neither ammonia nor nitrite accumulated 0.1 ppm and nitrate could be suppressed to about 10 ppm. Biol Sci Space, 1999 Dec, 13(4), 341 - 7 Closed water recirculating system for fish rearing equipped with bioreactor capable of simultaneous nitrification and denitrification; Uemoto H et al.; Five crucian carp, Carassius auratus langsdorfiicarps had been reared in a closed water recirculating system . The system was equipped with the compact bioreactor using the plate gels capable of both nitrification and denitrification in a single unit . Ammonia and nitrite concentrations in the rearing water had been maintained below 0.05 mg-N/L, and nitrate concentration also controlled between 2 and 8 mg-N/L with the bioreactor . As concerns nitrogen budget in the closed system, 95.0% of nitrogen income from feed was lost as nitrogen gas from the closed system . All fish was alive for 91 days without any unusual behavior . Thus, the bioreactor performed both nitrification and denitrification abilities enough to rear the five fish for 91 days . The bioreactor using the plate gels would be effective to simplify the closed system both physically and operationally, since it can remove the ammonia excreted from fish as nitrogen gas by a single step. Biol Sci Space, 1999 Dec, 13(4), 333 - 40 Population dynamics of nitrifying bacteria in an aquatic ecosystem; Kubo Y et al.; In a space environment such as Space Shuttle or Space Station, animal experiments with aquatic species in a closed system pose a crucial problem in maintaining their water quality for a long term . In nature, ammonia as an animal wastes is converted by nitrifying bacteria to nitrite or nitrate compounds, which usually become nitrogen sources for plants . Thus an application of the biological reactor with such bacteria attached on some filters has been suggested and experimentally studied for efficient waste managements of ammonia . Although some successful results were reported (Kozu et al . 1995, Nagaoka et al . 1998, Nakamura et al . 1997, 1998) in the space applications, purely empirical approaches have so far been taken to develop a biological filter having a stable nitrifying activity . In this study, we constructed a mathematical model to deal with the dynamics of the ammonia nitrifying processes in a biological reactor . The model describes population dynamics of the ammonia-oxidizing bacteria and the nitrite-oxidizing bacteria cultivated on the same filter . We estimated parameters involved in the model using the experimental data . The result shows that these estimated parameters could be applied to general cases and that the two bacteria are in a symbiotic relationship; they can better perform when both coexist, as has been empirically recognized . Based on the model analysis, we discuss how to prepare a high performance biological filter. Biol Sci Space, 1999 Dec, 13(4), 327 - 32 Water quality management for low temperature marine fishes in space; Nagaoka S et al.; Vestibular Function Experiment Unit (VFEU), one of the Spacelab facility flown in Neurolab mission (STS-90) in April, 1998, was to support neurophysiological research using a marine fish, Opsanus tau (oyster toadfish) . The functions of the VFEU were primarily a quality management of environmental water during the mission at 14 degrees C and for acquiring physiological signals from implanted micro-electrodes in the otolith nerves as well as the spatial acceleration of the fish . A key element of the life support system was a balanced biological filter containing two types of nitrifying bacteria, Nitrosomonas for ammonia oxidization and Nitrobacter for nitrite oxidization . Although the 16 days mission was successful, two toadfishes died in late phase of the mission . Ammonium concentration in those two life support systems elevated to remarkably high level at the end of the mission whereas the other two indicated very low . This report summarizes the results of the water quality management of the VFEU during the Neurolab mission based on analysis of water samples taken during the flight and those taken prior and just after the flight. Biol Sci Space, 1999 Dec, 13(4), 321 - 6 VFEU water quality control in STS-95 mission; Uchida S et al.; In STS-95 Space Shuttle mission, an aquatic animal research facility, Vestibular Function Experiment Unit (VFEU), was flown to perform neurobiological experiment with marine fish, oyster toadfish . For this purpose, we have developed a sea water purification system using highly active nitrifying bacteria at low temperature . With this system, the water quality in the VFEU was maintained in sufficient condition to keep the toadfish in healthy state for 9 days of the mission . This report summarizes the efficiency of the filter system based on the results from pre-flight bacterial preparation, water analysis of samples taken during flight, and the post-flight analysis of the bacterial filter. Adv Space Res, 1997, 20(10), 2017 - 22 Hydroponic potato production on nutrients derived from anaerobically-processed potato plant residues; Mackowiak CL et al.; Bioregenerative methods are being developed for recycling plant minerals from harvested inedible biomass as part of NASA's Advanced Life Support (ALS) research . Anaerobic processing produces secondary metabolites, a food source for yeast production, while providing a source of water soluble nutrients for plant growth . Since NH4-N is the nitrogen product, processing the effluent through a nitrification reactor was used to convert this to NO3-N, a more acceptable form for plants . Potato (Solanum tuberosum L.) cv . Norland plants were used to test the effects of anaerobically-produced effluent after processing through a yeast reactor or nitrification reactor . These treatments were compared to a mixed-N treatment (75:25, NO3:NH4) or a NO3-N control, both containing only reagent-grade salts . Plant growth and tuber yields were greatest in the NO3-N control and yeast reactor effluent treatments, which is noteworthy, considering the yeast reactor treatment had high organic loading in the nutrient solution and concomitant microbial activity. Adv Space Res, 1997, 20(10), 2009 - 15 Evaluation of an anaerobic digestion system for processing CELSS crop residues for resource recovery; Strayer RF et al.; Three bioreactors, connected in series, were used to process CELSS potato residues for recovery of resources . The first stage was an anaerobic digestor (8 L working volume; cow rumen contents inoculum; fed-batch; 8 day retention time; feed rate 25 gdw day-1) that converted 33% of feed (dry weight loss) to CO2 and "volatile fatty acids" (vfa, 83:8:8 mmolar ratio acetic:propionic:butyric) . High nitrate-N in the potato residue feed was absent in the anaerobic effluent, with a high portion converted to NH4(+)-N and the remainder unaccounted and probably lost to denitrification and NH4+ volatilization . Liquid anaerobic effluent was fed to an aerobic, yeast biomass production vessel (2 L volume; Candida ingens inoculum; batch {pellicle} growth; 2 day retention time) where the VFAs and some NH4(+)-N were converted into yeast biomass . Yeast yields accounted for up to 8% of potato residue fed into the anaerobic bioreactor . The third bioreactor (0.5 L liquid working volume; commercial nitrifier inoculum; packed-bed biofilm; continuous yeast effluent feed; recirculating; constant volume; 23 day hydraulic retention time) was used to convert successfully the remaining NH4(+)-N into nitrate-N (preferred form of N for CELSS crop production) and to remove the remaining degradable soluble organic carbon . Effluents from the last two stages were used for partial replenishment of minerals for hydroponic potato production. Syst Appl Microbiol, 1984, 5, 315 - 26 The phylogeny of purple bacteria: the alpha subdivision; Woese CR et al.; The technique of oligonucleotide cataloging shows the purple photosynthetic eubacteria to comprise three major subdivisions, temporarily called alpha, beta, and gamma--previously designated groups I-III by Gibson et al . (1979) . Each subdivision contains a number of non-photosynthetic genera in addition to the photosynthetic ones . The alpha subdivision, the subject of the present report, contains most but not all of the species that fall into the classically defined genera Rhodospirillum, Rhodopseudomonas and Rhodomicrobium . Intermingled with these are a variety of non-photosynthetic species from genera such as Agrobacterium, Rhizobium, Azospirillum, Nitrobacter, Erythrobacter, Phenylobacterium, Aquaspirillum, and Paracoccus . The phylogenetic substructure of the alpha subdivision is presented and the evolutionary significance of the admixture of biochemical phenotypes is discussed. Limnol Oceanogr, 1996 Nov, 41(7), 1544 - 51 Extreme supersaturation of nitrous oxide in a poorly ventilated Antarctic lake; Priscu JC et al.; Lake Bonney, a permanently ice-covered Antarctic lake, has a middepth maximum N2O concentration of 41.6 micromoles N (>580,000% saturation with respect to the global average mixing ratio of N2O) in its east lobe, representing the highest level yet reported for a natural aquatic system . Atmospheric N2O over the lake was 45% above the global average, indicating that this lake is an atmospheric source of N2O . Apparent N2O production (ANP) was correlated with apparent oxygen utilization (AOU), and denitrification was not detectable, implying that nitrification is the primary source for this gas . The slope of a regression of ANP on AOU revealed that potential N2O production per unit of potential O2 consumed in the east lobe of Lake Bonney is at least two orders of magnitude greater than reported for the ocean . The maximum yield ratio for N2O {ANP/(NO2(-) + NO3-)} in Lake Bonney is 26% (i.e . 1 atom of N appears in N2O for every 3.9 atoms appearing in oxidized N), which exceeds previous reports for pelagic systems, being similar to values from reduced sediments . Areal N2O flux from the lake to the atmosphere is >200 times the areal flux reported for oceanic systems; most of this gas apparently enters the atmosphere through a small moat that occupies approximately 3% of the surface of the lake and exists for approximately 10 weeks in summer. Atmos Environ, 1984, 18(9), 1797 - 804 Tropospheric sources of NOx: lightning and biology; Levine JS et al.; Laboratory experiments to quantify the global production of NOx (NO + NO2) in the troposphere due to atmospheric lightning and biogenic activity in soil are presented . These laboratory experiments, as well as other studies, suggest that the global production of NOx by lightning probably ranges between 2 and 20 MT(N)y-1 of NO and is strongly dependent on the total energy deposited by lightning, a quantity not well-known . In our laboratory experiments, nitrifying micro-organisms is soil were found to be a significant source of both NO and nitrous oxide (N2O) . The measured production ratio of NO to N2O averaged 2-3 for oxygen partial pressures of 0.5-10% . Extrapolating these laboratory measurements to the global scale, which is somewhat risky, suggests that nitrifying micro-organisms in soil may account for as much as 10 MT(N) y-1 of NO . Additional experiments with denitrifying micro-organisms gave an NO to N2O production ratio ranging from 2 to 4 for an oxygen partial pressure of 0.5% and a ratio of less than unity for oxygen partial pressures ranging from 1 to 20% . The production of NO and N2O, normalized with respect to micro-organism number indicates that the production of both NO and N2O by denitrifying micro-organisms is at least an order of magnitude less than production by nitrifying micro-organisms for the micro-organisms studied. Life Support Biosph Sci, 1997, 4(1-2), 31 - 41 A simple mass balance model of nitrogen flow in a bioregenerative life support system; Loader CA et al.; A mathematical model of the nitrogen cycle in a bioregenerative life support system (BLSS) was developed to help conceptualize and quantify nitrogen flux and storage in BLSS processes and subsystems . The mathematical model was initially designed as a simple mass balance, donor-controlled system that quantified the amount of nitrogen in moles per person . Dynamic equations were then applied to describe certain relationships more accurately . Comparison of nitrogen fluxes suggests that even at very low atmospheric leakage rates, loss of nitrogen gas would account for the largest nitrogen movement in the "closed" system . This observation decreases the relative importance of denitrification and nitrification in closed system nitrogen balances . Sensitivity analysis was used to determine the relative stability of various model subsystems, and demonstrated the importance of plant nitrogen uptake on overall system dynamics of nitrogen. Life Support Biosph Sci, 1996, 3(1-2), 25 - 9 Nitrification and ammonification in aquatic systems; Ward BB; Nitrification is an essential step in the nitrogen cycle of natural systems because it links organic matter degradation to fixed nitrogen loss . Ammonium released by ammonification is oxidized to nitrate by nitrification, and can then be reduced to dinitrogen gas by denitrification, resulting in net loss of fixed nitrogen from the system . Whether organic matter degradation results in net ammonium release depends largely on the quality of the organic substrate and interactions among members of the microbial community involved in nitrogen and organic matter cycling . In sediments, nitrogen cycle processes depend on the supply of organic matter and oxygen from overlying water . The nature of the net flux (which direction and which form of nitrogen) is a function of closely coupled reactions (ammonification-nitrification-denitrification) in the nitrogen cycle. Life Support Biosph Sci, 1996, 3(1-2), 17 - 24 The nature of nitrogen: an overview; Mancinelli RL; Most of the nitrogen available to the biosphere exists as N2 in the atmosphere, and is not useful to most organisms until it is "fixed" either biologically or abiotically (by lightning or aurorae, or industrially) . Once it is fixed into NH3, usually it is either assimilated and transformed into organic N or nitrified into NO3- . Organic N can be transformed back into NH3 by ammonification . Nitrate can be converted into N2O by nitrification and denitrification, and to N2 by denitrification . Such N2O and N2 production results in nitrogen loss from ecosystems and a nitrogen gain to the atmospheric nitrogen reservoir . The different steps of the nitrogen cycle require different environmental conditions . These differences result in a spatial distribution pattern of the different nitrogen transformation reactions . Biological nitrogen fixation occurs universally in soils, sediments, fresh water, and marine systems that are both aerobic and anaerobic . Nitrification occurs primarily in aerobic habitats, whereas denitrification predominates in anaerobic habitats such as sediments and water-logged soils . In closed systems, such as plant growth chambers for CELSS, denitrification and nitrification result in a loss of fixed nitrogen available to plants. Orig Life Evol Biosph, 1988, 18, 311 - 25 The evolution of nitrogen cycling; Mancinelli RL et al.; Based upon arguments concerning properties of the environment and the energetics of nitrogen transformation reactions, new hypotheses regarding their evolution are presented . These hypotheses are supported by new calculations and observations germane to understanding the evolution of the nitrogen cycle . From calculations of shock production by meteor impact, we suggest that impact produced fixed nitrogen could have resulted in the entire reservoir of Earth's N2 being converted into fixed nitrogen at the end of accretion . We have significantly improved upon previous calculations of the abiotic fixation rate on the early earth and find a rate of fixation by lightning of approximately 1-3 x 10(16) molecules NO/J, which is 2 to 3 times greater than previous estimates . This strengthens the suggestion, corroborated by the predominance of a single nitrogenase enzyme, that biological nitrogen fixation may have been a late evolutionary development, after the development of an aerobic atmosphere . In addition, we show for the first time that HNO, predicted to be the main product of atmospheric photochemical reactions involving NO on the primitive Earth by photochemical models, would eventually become NO2- and NO3- after reaching the Earth's surface . Based upon microbe-environment interactions on an ecological as well as a biochemical scale we suggest that denitrification arose prior to aerobic respiration and that nitrification arose after the advent of an aerobic atmosphere . We hypothesize the following evolutionary sequence for the biological transformation of nitrogen compounds: Ammonification --> Denitrification --> Nitrification --> Nitrogen fixation. Adv Space Res, 1987, 7(4), 81 - 4 The applicability of catalytic wet-oxidation to CELSS; Takahashi Y et al.; The wet-oxidation catalysis of Au, Pd, Pt, Rh or Ru on a ceramic honeycomb carrier was traced in detail by 16 to 20 repetitive batch tests each . As a result, Pt or Pd on a honeycomb carrier was shown to catalyze complete nitrogen gasification as N2 . Though the catalysts which realize both complete nitrogen gasification and complete oxidation could not be found, the Ru+Rh catalyst was found to be most promising . Ru honeycomb catalyzed both nitrification and nitrogen gasification. Biotechnol Bioeng, 2001 Oct 5, 75(1), 82 - 92 N-removal in a granular sludge sequencing batch airlift reactor; Beun JJ et al.; The removal of N-compounds in the sequencing batch airlift reactor (SBAR) containing granular sludge was studied under conditions of decreased dissolved oxygen (DO) . A simulation model was developed to describe and evaluate the effects of several process conditions in the SBAR on N-removal performance . The model described the experimental data reasonable well . It has been shown that nitrification, denitrification, and removal of chemical oxygen demand (COD) can occur simultaneously in a granular sludge SBR . It has also been shown that the exact location of the autotrophic biomass influences the net N-removal . The distribution of the autotrophic biomass is influenced by the DO in the reactor . The optimal DO value is expected to be around 40% air saturation . It was shown that storage and subsequent degradation of poly-beta-hydroxybutyrate (PHB) benefit the denitrification . In particular, PHB is stored in bacteria situated in deeper layers of the granules below where the autotrophic activity occurs, serves as a C-source for denitrification . Appl Environ Microbiol, 2001 Sep, 67(9), 3908 - 22 Seasonal and spatial variability in Lake Michigan sediment small-subunit rRNA concentrations; MacGregor BJ et al.; We have used molecular biological methods to study the distribution of microbial small-subunit rRNAs (SSU rRNAs), in relation to chemical profiles, in offshore Lake Michigan sediments . The sampling site is at a depth of 100 m, with temperatures of 2 to 4 degrees C year-round . RNA extracted from sediment was probed with radiolabeled oligonucleotides targeting bacterial, archaeal, and eukaryotic SSU rRNAs, as well as with a universal probe . The coverage of these probes in relation to the present sequence database is discussed . Because ribosome production is growth rate regulated, rRNA concentrations are an indicator of the microbial populations active in situ . Over a 1-year period, changes in sedimentary SSU rRNA concentrations followed seasonal changes in surface water temperature and SSU rRNA concentration . Sedimentary depth profiles of oxygen, reduced manganese and iron, and sulfate changed relatively little from season to season, but the nitrate concentration was approximately fivefold higher in April and June 1997 than at the other times sampling was done . We propose that sediment microbial SSU rRNA concentrations at our sampling site are influenced by seasonal inputs from the water column, particularly the settling of the spring diatom bloom, and that the timing of this input may be modulated by grazers, such that ammonia becomes available to sediment microbes sooner than fresh organic carbon . Nitrate production from ammonia by autotrophic nitrifying bacteria, combined with low activity of heterotrophic denitrifying bacteria in the absence of readily degradable organic carbon, could account for the cooccurrence of high nitrate and low SSU rRNA concentrations. Arch Environ Contam Toxicol, 2001 May, 40(4), 451 - 60 Inhibition of aerobic growth and nitrification of bacteria in sewage sludge by antibacterial agents; Halling-Sorensen B; Toxicity of antibacterial agents on environmentally relevant bacteria was investigated using activated sludge . The growth and nitrifying inhibiting effects for activated sludge of benzyl penicillin (penicillin G) (BP), tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC), olaquindox (O), streptomycin (ST), tiamulin (TI), tylosin (TYL) sulfadiazine (SDZ), metronidazole (MET), and oxolinic acid (OXA) was investigated . Studies were performed in accordance to the ISO 15522 (1999) and ISO 9509 (1989) test guidelines, respectively . The toxicity (EC50 value, mg/L) found with the ISO 15522 was in decreasing EC50 values; O (95.7), BP (84.6), TYL (54.7), TI (14.3), TC (2.2), OTC (1.2), ST (0.47), CTC (0.40), and OXA (0.1) . No observed effect concentrations (NOECs) (mg/L) of 100 and 60, respectively was found for MET and SDZ . Triplicate tests assessing the effects of the antibacterial agents on the nitrification rate gave indications only as the level of increased or decreased rate . More accurate data for the inhibition of Nitrosomonas europaea was found with a suspended culture of the nitrifying bacteria . The toxicity (EC50 value, mg/L) found was in decreasing EC50 values; TI (23.3), SDZ (17.0), TC (4.0), OTC (1.7), OXA (1.0), CTC (0.64), O (0.03), ST (0.02) . For MET and TYL, NOECs (mg/L) of 100 and 50 were found, respectively . The antibacterial agents were also assessed using a pour plate method with both (separately tested) activated sludge bacteria and N . europeae showing to be 5 to 10 times more potent to most agents except SDZ, TI, and MET. J Contam Hydrol, 2001 Aug, 50(3-4), 175 - 208 Impact of urbanization on hydrochemical evolution of groundwater and on unsaturated-zone gas composition in the coastal city of Tel Aviv, Israel; Zilberbrand M et al.; The coastal city of Tel Aviv was founded at the beginning of the 20th century . The number of its inhabitants and its water consumption increased rapidly . This study analyses a 15-year record (1934-1948) of pre-industrial development of groundwater chemistry in the urban area . Archive data on concentrations of major ions, dissolved gases (CO2 and O2), organic matter, and pH were available for each half-year during the period of 1934-1948 . The major factors causing changes in the chemistry of groundwater flowing in three sandy sub-aquifers have been seawater encroachment due to overpumping, and infiltration of effluents from pit-latrine collectors . Influence of these factors decreases with depth . Landward-penetrating seawater passed through clayey coastal sediments, interbedded among sands and calcareous sandstones, and spread into the Kurkar Group aquifer . This has led to exchange of sodium (dominant in seawater) with calcium adsorbed on clay particles, enriching groundwater with calcium . Intensity of cation exchange decreases inland and with depth . Infiltration of pit-latrine effluents has introduced large amounts of ammonium into the unsaturated zone . Its rapid oxidation in unsaturated sediments has caused massive nitrate production, accompanied by pore-water acidification . This process induces dissolution of vadose carbonate, resulting in enrichment of groundwater recharge in calcium . Anthropogenically induced dissolution of calcite in the unsaturated zone has been the major factor for the increase of Ca2+ concentration in groundwater, accounting for about 80% of this increase . In the interface zone, an additional 20% of calcium has been supplied by cation exchange . Owing to pH increase caused by denitrification in the aquifer, Ca(2+)-rich waters supersaturated with calcite could be formed, especially in the capillary fringe of the uppermost sub-aquifer, which could induce calcite precipitation and ultimately lead to the cementation of sandy aquifers . Urban development has caused drastic changes in the gas content in the unsaturated zone and in groundwater . Carbon dioxide was intensively generated by nitrification-denitrification processes, by hydration of urea, to a lesser degree by oxidation of organic matter, and probably by anoxic biodegradation of organics . Between 1934 and 1948, concentrations of CO2 in unsaturated sediment air rose from 3.2% to 7.6% . In the unsaturated zone, oxygen consumption for oxidation of ammonium and organic matter lowered O2 concentrations in sediment air to unusually low values of 3.9-12.9% . Nitrification in the urban unsaturated zone could thus serve as a pump, sucking in atmospheric oxygen at a rate of about 0.3-0.5 g m-2 day-1 . The extreme concentrations of CO2 and O2 in unsaturated sediments have been preserved due to production and consumption of gas under conditions of diminishing areas open to the atmosphere, uncovered by buildings and by roads. Antonie Van Leeuwenhoek, 2001 Jun, 79(2), 179 - 88 A comparison of ammonia-oxidiser populations in eutrophic and oligotrophic basins of a large freshwater lake; Whitby CB et al.; A combination of PCR amplification and oligonucleotide probing was used to investigate the populations of ammonia-oxidisers of the beta-Proteobacteria in the eutrophic and oligotrophic basins of Lake Windermere, a large temperate lake in the English Lake District . Numbers of ammonia-oxidisers (MPN) in the Windermere lakewater were low (< 100 cells ml(-1)) throughout the year with the exception of peaks in August, which coincided with stratification, and November in the South Basin where overturn may have introduced ammonia-oxidising bacteria into the water column . Sediment samples contained larger populations of ammonia oxidisers, usually ca . 10(4) per g . dry weight, which remained relatively constant throughout the seasonal cycle in both Basins . DNA was recovered from lakewater and sediment samples and Nitrosospira and N . europaea-eutropha lineage 16S rRNA genes amplified in a nested PCR reaction, with confirmation of identity by oligonucleotide hybridisation . Nitrosospira 16S rDNA was readily detected in all samples and therefore found to be ubiquitous . In contrast, nitrosomonad DNA of the N . europaea-eutropha lineage could only be detected in the oligotrophic North Basin . Enrichment cultures of lakewater samples only exhibited nitrification at low (0.67 mM) and medium (5 mM) ammonium concentrations, whilst sediment enrichments nitrified at all concentrations tested including high (12.5 mM) ammonium medium . These data suggest that ammonia-oxidiser populations may be physiologically distinguished between lakewater and sediment, and that species distribution in a single lake is non-uniform. Environ Monit Assess, 2001 Jul, 70(1-2), 223 - 31 Activity monitoring for nitrifying bacteria by fluorescence in situ hybridization and respirometry; Kim IS et al.; The activities of two families of nitrifying bacteria were measured by applied respirometer and fluorescence in situ hybridization (FISH) for the purpose of monitoring nitrogen removal . Oxygen uptake rates (OUR) for Nitrosomonas and Nitrobacter were separately measured with the dosing of selective inhibitors during respirometric monitoring . The FISH method was applied to analyze microorganism communities . In 5 mg NH4+-N/L solution, the total nitrogen oxygen demand (NOD) was found to be 6,672 mg DO/L-day with ammonia and nitrite oxidation rate of 4,512 and 2,160 mg DO/L-day, respectively . The oxygen consumption by endogenous oxidation was 288 mg DO/L-day and the biological oxygen demand 936 mg DO/L-day . Respirometric measurements were well matched by the FISH result, which described the presence and quantity of each nitrifying bacteria as nitrification proceeded . It was found that when coupled with OUR data, FISH could provide valuable information about the nitrogen removal process in many practical wastewater treatment systems. Chemosphere, 2001 Aug, 44(5), 1213 - 21 Relationship between release of nitric oxide and CO2 and their dependence on oxidation reduction potential in wastewater treatment; Fuerhacker M et al.; Nitric oxide (NO) is an intermediate of denitrification process and can be produced by denitrifiers, nitrifiers and other bacteria . In our experiments we measured the dynamic flow of NO depending on oxidation reduction potential (ORP) . Different ORP-ranges were related to various carbon loading stages in the wastewater treatment pilot plant . Nitrification and denitrification were achieved by a sequence of aeration and non-aeration periods . Our measurements show that different carbon loading conditions (low feed, balanced and overloaded conditions) did not change the range of the mixing ratio of NO emissions when the aeration conditions like air-flow and temperature were kept constant . Minimum and maximum NO mixing ratios were 34.7 and 91.8 ppbv; 52.3 and 91.3 ppbv; 57.6 and 109 ppbv for low feed, balanced and overloaded conditions, respectively . The curve of the NO graph relied on nitrification/denitrification dynamics . The dependence of NO release on different ORP and CO2-release during the various conditions are shown . Longer aeration times resulted in an increased release of gaseous NO . The net-release of NO g(-1) nitrogen removed was between 0.014% and 0.028% . The NO fluxes to the air were observed between 8.3 and 14.9 mg m(-2) d(-1) NO . The major release occurred during high aeration periods whereas the concentration of dissolved {NOaq} in the wastewater was less than 0.05% of the gaseous release due to very low solubility of the NO. Arch Microbiol, 2001 Sep, 176(3), 170 - 7 Isolation and properties of obligately chemolithoautotrophic and extremely alkali-tolerant ammonia-oxidizing bacteria from Mongolian soda lakes; Sorokin D et al.; Five mixed samples prepared from the surface sediments of 20 north-east Mongolian soda lakes with total salt contents from 5 to 360 g/l and pH values from 9.7 to 10.5 were used to enrich for alkaliphilic ammonia-oxidizing bacteria . Successful enrichments at pH 10 were achieved on carbonate mineral medium containing 0.6 M total Na(+) and < or =4 mM NH(4)Cl . Five isolates (ANs1-ANs5) of ammonia-oxidizing bacteria capable of growth at pH 10 were obtained from the colonies developed on bilayered gradient plates . The cells were motile and coccoid, with well-developed intracytoplasmic membranes (ICPM) and carboxysomes . At pH 10.0, ammonia was toxic for growth at concentrations higher than 5 mM NH(4)Cl . The bacteria were able to grow within the salinity range of 0.1-1.0 M of total Na+ (optimum 0.3 M) . In media containing 0.3-0.6 M total Na(+), optimal growth in batch cultures occurred in the presence of a bicarbonate/carbonate buffer system within the pH range 8.5-9.5, with the highest pH limit at pH 10.5 . At pH lower than 8.0, growth was slower, most probably due to decreasing free ammonia . The pH profile of the respiratory activity was broader, with limits at 6.5-7.0 and 11.0 and an optimum at 9.5-10.0 . In pH-controlled, NH(3)-limited continuous culture, isolate ANs5 grew up to pH 11.3, which is the highest pH limit known for ammonia-oxidizing bacteria so far . This showed the existence of extremely alkali-tolerant ammonia-oxidizing bacteria in the soda lakes . Comparative 16S rDNA sequence analysis of the five isolates demonstrated that they possess identical 16S rDNA genes and that they are closely related to Nitrosomonas halophila (sequence similarity 99.3%), a member of the beta-subclass of the Proteobacteria . This affiliation was confirmed by comparative sequence analysis of the amoA gene, encoding the active-site subunit of the ammonia-monoxygenase, of one of the isolates . DNA-DNA hybridization data further supported that the soda lake isolates are very similar to each other and represent an alkali-tolerant subpopulation of N . halophila whose species description is herewith amended. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2001, 36(6), 1027 - 40 Factors affecting nitrite build-up in nitrifying biofilm reactor; Liu Y et al.; Nitrite build-up in a nitrifying biofilm reactor for direct denitrification from the nitrite stage was investigated . At least three factors were found to influence the nitrite build-up: (i) the relative specific growth rates of Nitrosomonas to Nitrobacter, microNs/microNb in the biofilm; (ii) the relative initial ratio between Nitrosomonas and Nitrobacter on the support surface, (Mao)Ns/(Mao)Nb; (iii) the level of free ammonia, particularly at greater than 0.1 mg N/l that can be inhibitory to Nitrobacter . Results showed that without free ammonia inhibition, the first two factors determined the degree of nitrite build-up . The effect of (Mao)Ns and (Mao)Nb on nitrification kinetics were more significant than the specific growth rates of Nitrosomonas and Nitrobacter . By regulating effects of these three factors, extremely high concentrations of nitrite build-up could occur in a biofilm reactor . This offers a potential for achieving direct denitrification through a nitrate shunt. Appl Microbiol Biotechnol, 2001 Jul, 56(1-2), 40 - 57 Application of rRNA-targeted oligonucleotide probes in biotechnology; Lipski A et al.; Ribosomal RNA-targeted oligonucleotide probes have become valuable tools for the detection of microorganisms involved in important biotechnological processes . Microorganisms which are of major importance for processes such as wastewater treatment, microbial leaching or methane production can be detected and quantified in situ within a complex microbial community . For certain processes, such as nitrification or biological phosphate removal, new microorganisms have become the focus of interest and have led to an improved understanding of these bioremediation techniques . Hybridization techniques have become fast and reliable alternatives to conventional cultivation techniques in the food industry as a control method for starter cultures for fermentation processes or product control . Recent analytical tools such as flow cytometry and digital image processing have improved the efficiency of these techniques . This review is intended to present a summary of methodological aspects of rRNA-based hybridization techniques and their application in biotechnology. Water Sci Technol, 2001, 44(1), 95 - 104 Development of a real-time control strategy with artificial neural network for automatic control of a continuous-flow sequencing batch reactor; Cho BC et al.; The purpose of this study is to develop a reliable and effective real-time control strategy by integrating artificial neural network (ANN) process models to perform automatic operation of a dynamic continuous-flow SBR system . The ANN process models, including ORP/pH simulation models and water quality ({NH4(+)-N} and {NOx(-)-N}) prediction models, can assist in real-time searching the ORP and pH control points and evaluating the operation performances of aerobic nitrification and anoxic denitrification operation phases . Since the major biological nitrogen removal mechanisms were controlled at nitrification (NH4(+)-N-->NO2(-)-N) and denitritification (NO2(-)-N-->N2) stages, as well as the phosphorus uptake and release could be completely controlled during aerobic and anoxic operation phases, the system operation performances under this ANN real-time control system revealed that both the aeration time and overall hydraulic retention time could be shortened to about 1.9-2.5 and 4.8-6.2 hrs/cycle respectively . The removal efficiencies of COD, ammonia nitrogen, total nitrogen, and phosphate were 98%, 98%, 97%, and 84% respectively, which were more effective and efficient than under conventional fixed-time control approach. Water Sci Technol, 2001, 44(1), 77 - 85 Acetate injection into anaerobic settled sludge for biological P-removal in an intermittently aerated reactor; Ahn KH et al.; Injecting acetate into the sludge layer during the settling and decanting periods was adopted to enhance phosphorus release inside the sludge layer during those periods and phosphorus uptake during the subsequent aeration period in a KIST Intermittently Decanted Extended Aeration (KIDEA) process . The relationship among nitrification, denitrification and phosphorus removal was investigated in detail and analyzed with a qualitative floc model . Dependencies of nitrification on the maximum DO level during the aerobic phase and phosphorus release on residual nitrate concentration during the settling phase were significant . High degree of nitrification resulted that phosphorus release inside the sludge layer was significantly interfered with nitrate due to the limitation of available acetate and the carbon sources from influent . Such limitation was related to the primary utilization of organic substance for denitrification in the outer layer of the floc and the retarded mass transfer into the inner layer of the floc . Nevertheless, effects of acetate injection on both denitrification and phosphorus release during the settling phase were significant . Denitrification rate after acetate injection was two times as high as that before acetate injection, and phosphorus release reached about 14 mg PO4(3-)-P/g MLVSS/hr during the decanting phase after the termination of denitrification inside the sludge layer . Extremely low level of maximum DO (around 0.5 mg/L) during the aerobic phase may inhibited nitrification, considerably, and thus nearly no nitrate was present . However, the absence of nitrate increased when the phosphorus release rate was reached up to 33 mg PO4(3-)-P/g MLVSS/hr during the settling and decanting phase, and nearly all phosphorus was taken up during subsequent aerobic phase . Since the sludge layer could function as a blocking layer, phosphorus concentrations in the supernatant was not influenced by the released phosphorus inside the sludge layer during the settling and decanting period . Phosphorus removal was directly (for uptake) and indirectly (for release) dependent on the median and maximum DO concentration during the aerobic phase, and those optimal values may exist within the range from 0.2 to 0.6 mg/L and 0.4 to 1.2 mg/L, respectively. Water Sci Technol, 2001, 44(1), 181 - 6 Nutrient removal from low strength domestic wastewater in sequencing batch biofilm reactor; Altinbas U; Nutrient removal was investigated in a packed bed column, which was operated by changing of aerated and non-aerated periods . Good removal efficiencies for nitrogen and phosphorus were obtained at long aeration period . Highest nitrification efficiency was observed in run3 because the aeration period was enough to allow nitrification . NO3 concentration was not significantly changed during the cycle, because of simultaneous denitrification during aerobic stage . Nitrogen and phosphorus removal efficiencies reached to 71 and 74% in run3 respectively . Effluent concentrations of TKN, Tot.P, NH4 and NO3 were found as 3.8, 3, 1 and 2.5 mg/l respectively. Water Sci Technol, 2001, 44(1), 167 - 72 Modification and expansion of a pure oxygen WWTP for biological nutrient removal (BNR); Randall CW et al.; A pure oxygen activated sludge system was converted to a VIP configuration BNR (biological nutrient removal) system wherein three of the five pure oxygen sections were retained, and performance was compared to that of a side-by-side air aeration MUCT (modified UCT) system . Because the pure oxygen BNR system could not obtain good nitrification, its treatment capacity had to be downgraded from 113,550 m3/d to a flow of only 60,000 m3/d . At the lesser flow, it was determined that adequate nitrification and improved denitrification could be accomplished in the pure oxygen system by continuously seeding it with 100% of the WAS from the MUCT system . Fortunately, while the capacity of the pure oxygen system had to be downgraded, it was determined that the capacity of the MUCT system was substantially greater than its design flow, and the combined system is capable of treating the entire design flow . However, this requires increasing the operating sludge age of the MUCT system . The pure oxygen BNR system performed better phosphorus removal than the MUCT system, both before and after seeding with the MUCT WAS . Apparently this was because the MUCT system was operated at a substantially higher sludge age than the pure oxygen system . However, both systems have consistently discharged effluent phosphorus concentrations of less than 2.0 mg/L TP, which is the Chesapeake Bay standard . Even with improved nitrification and denitrification in the pure oxygen BNR system, neither it nor the MUCT system have proven to be capable of meeting the Virginia Chesapeake Bay goal of 10 mg/L total nitrogen in the effluent. Water Sci Technol, 2001, 44(1), 153 - 60 The SHARON-Anammox process for treatment of ammonium rich wastewater; van Dongen U et al.; The treatment of ammonium rich wastewater, like sludge digester effluent, can be significantly improved when new biotechnological processes are introduced . In this paper, the combination of a partial nitrification process (SHARON) and anoxic ammonium oxidation (Anammox) process for the treatment of ammonia rich influents is evaluated . Herein the combined process has been studied with sludge recycle liquor from the WWTP Rotterdam-Dokhaven . The SHARON process was operated stably for more than 2 years in a 10ICSTR under continuous aeration with a HRT of 1 day . The ammonia in the sludge liquor was converted by 53% to nitrite only . During the test period no formation of nitrate was observed . The effluent of the SHARON process was ideally suited as influent for the Anammox reactor . The Anammox process was operated as a granular sludge SBR-process . More than 80% of the ammonia was converted into dinitrogen gas at a load of 1.2 kgN/m3 per day . Planctomycete-like bacteria dominated the mixed community of the Anammox reactor, and only a small percentage of the population consisted of aerobic ammonium-oxidizing bacteria . This showed that the ammonium-oxidizers in the effluent of the SHARON process did not accumulate in the SBR . The test period showed that the combined SHARON-Anammox system can work stably over long periods and the process is ready for full-scale implementation. Water Sci Technol, 2001, 44(1), 145 - 52 Overview: full scale experience of the SHARON process for treatment of rejection water of digested sludge dewatering; van Kempen R et al.; A SHARON system has been constructed at the Utrecht WWTP and at the Rotterdam Dokhaven WWTP . In the SHARON process rejection water from dewatering of digested sludge is treated for N-removal . It concerns a high active process operating without sludge retention . Due to differences in growth rate nitrite oxidisers can be washed out of the system while ammonia oxidisers are maintained, resulting in N-removal over nitrite . The SHARON process was selected in competition with several other techniques . The feed of a SHARON system is concentrated, with ammonia concentrations ranging from 0.5 to 1.5 g N/l . The results show that conversion rates of 90% are well possible with N-removal mainly via the nitrite route . The process was shown to be stable . Due to the high ammonium influent concentrations pH control is of great importance, preventing process inhibitions . The acidifying effect of nitrification can be compensated completely by CO2 stripping during aeration and by denitrification . Heat production by biological conversions is significant, due to the high inlet concentrations, and contributes to the optimal operating temperature of 30-40 degrees C. Water Sci Technol, 2001, 44(1), 113 - 20 Influence of primary sedimentation on pre-denitrification system performances; Esposito G et al.; The effects of suppressing primary sedimentation on nitrogen removal efficiency of a pre-denitrification system have been evaluated for a large municipal wastewater treatment plant . Simulations have been carried out using the STOAT model . For both the process schemes with and without primary sedimentation, nitrification efficiencies are calculated for increasing influent loads of COD, total N and suspended solids . The sensitivity analysis shows that for the usual carbon to nitrogen ratios in the raw influent both the process schemes allow the requested removal efficiencies, whereas for significantly high C/N ratios the scheme with primary sedimentation is preferable. Water Sci Technol, 2001, 44(1), 105 - 12 Innovative low cost procedure for nutrient removal as an integrated element of a decentralised water management concept for rural areas; Burde M et al.; The absence of large rivers with rather high niveau of self purifying effect in parts of east Germany leads to a discharging of the effluent of wastewater treatment plants into the groundwater in many cases . One useful consequence is the idea of realisation of decentralised measures and concepts in urban water resources management concerning municipal wastewater as well as rainfall, precipitation . At the same time, only the upper soil zone--a few decimetres--is water--saturated and thus discharge effective, even when extreme rainfall takes place . Underneath, however, there generally exists an unsaturated soil zone, which is up to now a rather unexplored retardation element of the hydrologic- and substrate-cycle . Nutrient removal in small wastewater treatment plants that are emptying into ground waters is often beneficial . The presented studies optimised an inexpensive method of subsequent enhanced wastewater treatment . The developed reactor is similar to a concentrated subsoil passage . The fixed bed reactor is divided in two sections to achieve aerobic and anoxic conditions for nitrification/denitrification processes . To enhance phosphorus removal, ferrous particles are put into the aerobic zone . Two series of column tests were carried out and a technical pilot plant was built to verify the efficiency of the process . The results show that this method can be implemented successfully. Microbiology, 2001 Aug, 147(Pt 8), 2247 - 53 Ammonia oxidation by Nitrosomonas eutropha with NO(2) as oxidant is not inhibited by acetylene; Schmidt I et al.; The effect of acetylene ((14)C(2)H(2)) on aerobic and anaerobic ammonia oxidation by Nitrosomonas eutropha was investigated . Ammonia monooxygenase (AMO) was inhibited and a 27 kDa polypeptide (AmoA) was labelled during aerobic ammonia oxidation . In contrast, anaerobic, NO(2)-dependent ammonia oxidation (NO(2)/N(2)O(4) as oxidant) was not affected by acetylene . Further studies gave evidence that the inhibition as well as the labelling reaction were O(2)-dependent . Cells pretreated with acetylene under oxic conditions were unable to oxidize ammonia with O(2) as oxidant . After these cell suspensions were supplemented with gaseous NO(2), ammonia oxidation activity of about 140 micromol NH(4)(+) (g protein)(-1) h(-1) was detectable under both oxic and anoxic conditions . A significantly reduced acetylene inhibition of the ammonia oxidation activity was observed for cells incubated in the presence of NO . This suggests that NO and acetylene compete for the same binding site on AMO . On the basis of these results a new hypothetical model of ammonia oxidation by N . eutropha was developed. J Hazard Mater, 2001 Aug 17, 85(3), 213 - 27 Performance evaluation of single-sludge reactor system treating high-strength nitrogen wastewater; Jih CG et al.; In the single-sludge reactor system treating high-strength nitrogen wastewater (similar to anaerobically pretreated piggery wastewater), the NH4(+)-N removal efficiencies (98-82%) are higher than total nitrogen removal efficiencies (71-43%) . The mixed liquor recycle ratio only imposes a slight effect on total nitrogen removal efficiency . The alkalinity change data could be used for monitoring and control of the reactor system . To evaluate the performance of the single-sludge reactor system, a simplified nitrification-denitrification model (with nitrification capacity, denitrification capacity, and denitrification potential concepts) and a graphically analytical technique are proposed . It turns out that ammonia nitrification and total nitrogen removal efficiencies are strongly dependent on the process load and reactor configuration, and an optimal operating condition requires a proper match between nitrification and denitrification. Water Res, 2001 Sep, 35(13), 3089 - 96 Simultaneous removal of phenol and ammonia by an activated sludge process with cross-flow filtration; Yamagishi T et al.; Attempts were made for removing ammonia from synthetic wastewater under the presence of phenol, which is inhibitory to nitrification, by using a single-stage activated sludge process with cross-flow filtration . Activated sludge biomass which had been acclimated with phenol for over 15 years was used for the inoculum, and synthetic wastewater was continuously supplied to the process retaining biomass at 8000 mg VSS l(-1) . Phenol was completely removed, and ammonia was simultaneously nitrified to nitrate; nitrification rate reached 200 mg N l(-1) d(-1) when phenol was removed at a rate up to 300 mg l(-1) d(-1) . It was observed that 0-13% of the ammonia was removed via denitrification . Intermittent aeration enhanced the denitrification rate to 160 mg N l(-1) d(-1) by utilizing phenol . and approximately 24% of the denitrified nitrogen was recovered as nitrous oxide . Methanol, which is the most commonly used electron donor in conventional nitrogen removal processes, did not enhance the denitrification rate of the phenol-acclimated activated sludge used in this study, however phenol did . The results suggest that this process potentially works as a space- and energy-saving nitrogen removal process by utilizing substances inhibitory to nitrifiers as electron donors for denitrification. Environ Technol, 2001 Jun, 22(6), 705 - 12 The effects of the flow pattern on organic oxidation and nitrification in aerated submerged biofilters; Chiou RJ et al.; Previous research has shown that a submerged biofilter is effective in removing organic matter and total organic nitrogen . Upflow and downflow biofilters were set up to investigate the different oxidative efficiencies on organic matter and ammonia nitrogen of different biofilter positions and to compare the biological activities of the upflow and downflow patterns . A comparison of the operational characteristics of the two types of biofilters is discussed . The main COD removal zone is 0-20 cm in the upflow biofilter, but in the downflow biofilter it occurs in the submerged zone . The nitrification process is dependent on the HRT and the residual COD . In the downflow biofilter, the efficiency of the nitrification increases with the HRT . The growth of nitrifying bacteria has a tendency to take place in higher zones in the downflow biofilter, especially for a longer HRT . Batch tests measured the biological activity of heterotrophs and nitrifying autotrophs with decomposition rates . In the upflow biofilter, the nitrification rates increased while the COD oxidative rates decreased with the height of the biofilter, so the effect of the HRT on the activity of the nitrifying autotrophs is significant . However, in the down biofilter, the activity of the nitrifying autotrophs was similar at different heights in the same HRT runs with the maximum nitrifying autotrophs activity being at an HRT of 6 hours. Appl Environ Microbiol, 2001 Aug, 67(8), 3426 - 33 Influence of effluent irrigation on community composition and function of ammonia-oxidizing bacteria in soil; Oved T et al.; The effect of effluent irrigation on community composition and function of ammonia-oxidizing bacteria (AOB) in soil was evaluated, using techniques of molecular biology and analytical soil chemistry . Analyses were conducted on soil sampled from lysimeters and from a grapefruit orchard which had been irrigated with wastewater effluent or fertilizer-amended water (FAW) . Specifically, comparisons of AOB community composition were conducted using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified fragments of the gene encoding the alpha-subunit of the ammonia monooxygenase gene (amoA) recovered from soil samples and subsequent sequencing of relevant bands . A significant and consistent shift in the population composition of AOB was detected in soil irrigated with effluent . This shift was absent in soils irrigated with FAW, despite the fact that the ammonium concentration in the FAW was similar . At the end of the irrigation period, Nitrosospira-like populations were dominant in soils irrigated with FAW, while Nitrosomonas-like populations were dominant in effluent-irrigated soils . Furthermore, DGGE analysis of the amoA gene proved to be a powerful tool in evaluating the soil AOB community population and population shifts therein. Appl Environ Microbiol, 2001 Aug, 67(8), 3371 - 8 Effect of genetically modified Pseudomonas putida WCS358r on the fungal rhizosphere microflora of field-grown wheat; Glandorf DC et al.; We released genetically modified Pseudomonas putida WCS358r into the rhizospheres of wheat plants . The two genetically modified derivatives, genetically modified microorganism (GMM) 2 and GMM 8, carried the phz biosynthetic gene locus of strain P . fluorescens 2-79 and constitutively produced the antifungal compound phenazine-1-carboxylic acid (PCA) . In the springs of 1997 and 1998 we sowed wheat seeds treated with either GMM 2, GMM 8, or WCS358r (approximately 10(7) CFU per seed), and measured the numbers, composition, and activities of the rhizosphere microbial populations . During both growing seasons, all three bacterial strains decreased from 10(7) CFU per g of rhizosphere sample to below the limit of detection (10(2) CFU per g) 1 month after harvest of the wheat plants . The phz genes were stably maintained, and PCA was detected in rhizosphere extracts of GMM-treated plants . In 1997, but not in 1998, fungal numbers in the rhizosphere, quantified on 2% malt extract agar (total filamentous fungi) and on Komada's medium (mainly Fusarium spp.), were transiently suppressed in GMM 8-treated plants . We also analyzed the effects of the GMMs on the rhizosphere fungi by using amplified ribosomal DNA restriction analysis . Introduction of any of the three bacterial strains transiently changed the composition of the rhizosphere fungal microflora . However, in both 1997 and 1998, GMM-induced effects were distinct from those of WCS358r and lasted for 40 days in 1997 and for 89 days after sowing in 1998, whereas effects induced by WCS358r were detectable for 12 (1997) or 40 (1998) days . None of the strains affected the metabolic activity of the soil microbial population (substrate-induced respiration), soil nitrification potential, cellulose decomposition, plant height, or plant yield . The results indicate that application of GMMs engineered to have improved antifungal activity can exert nontarget effects on the natural fungal microflora. Water Res, 2001 Aug, 35(12), 2923 - 34 Impact of temperature on nitrification in biological activated carbon (BAC) filters used for drinking water treatment; Andersson A et al.; The impact of temperature on nitrification in biological granular activated carbon (GAC) filters was evaluated in order to improve the understanding of the nitrification process in drinking water treatment . The study was conducted in a northern climate where very cold water temperatures (below 2 degrees C) prevail for extended periods and rapid shifts of temperature are frequent in the spring and fall . Ammonia removals were monitored and the fixed nitrifying biomass was measured using a method of potential nitrifying activity . The impact of temperature was evaluated on two different filter media: an opened superstructure wood-based activated carbon and a closed superstructure activated carbon-based on bituminous coal . The study was conducted at two levels: pilot scale (first-stage filters) and full-scale (second-stage filters) and the results indicate a strong temperature impact on nitrification activity . Ammonia removal capacities ranged from 40 to 90% in pilot filters, at temperatures above 10 degrees C, while more than 90% ammonia was removed in the full-scale filters for the same temperature range . At moderate temperatures (4-10 degrees C), the first stage pilot filters removed 10-40% of incoming ammonia for both media (opened and closed superstructure) . In the full-scale filters, a difference between the two media in nitrification performances was observed at moderate temperatures: the ammonia removal rate in the opened superstructure support (more than 90%) was higher than in the closed superstructure support (45%) . At low temperatures (below 4 degrees C) both media performed poorly . Ammonia removal capacities were below 30% in both pilot- and full-scale filters. Rapid Commun Mass Spectrom, 2001, 15(15), 1291 - 6 Use of a novel nitrification inhibitor to reduce nitrous oxide emission from (15)N-labelled dairy slurry injected into soil; Dittert K et al.; Recent recommendations for environmentally sound use of liquid animal manure often include injection of slurry into soil . Two of the most important undesired side effects, ammonia (NH(3)) volatilisation and odour emissions, are usually significantly reduced by slurry injection . On the other hand, because of the higher amount of nitrogen (N) remaining in soil, the risk of nitrate (NO(3)(-)) leaching and nitrous oxide (N(2)O) emissions is increased . Thus, the reduction of local effects caused by NH(3) deposition, e.g . N enrichment and soil acidification, may be at the cost of large-scale effects such as ozone depletion and global warming as a result of emitted N(2)O . In this context, nitrification inhibitors can contribute significantly to a reduction in NO(3)(-) leaching and N(2)O production . A field experiment was carried out at IGER, North Wyke, which aimed to evaluate the effect of the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP/ENTEC) . For this experiment, (15)N enriched dairy slurry was used and the isotopic label in soil N as well as in N(2)O were studied . After slurry injection into the grassland soil in August 2000, the major emissions of N(2)O occurred during the first ten days . As expected, high N(2)O emission rates and (15)N content of the emissions were concentrated on the slurry injection slots, showing a steep decrease towards the untreated centre-point between slurry injection slots . The nitrification inhibitor DMPP proved to be very efficient in reducing N(2)O emissions . At a rate of 2 kg DMPP ha(-1), the total amount of N(2)O emitted was reduced by 32%, when compared with slurry injection without DMPP . The isotopic label of the emitted N(2)O showed that during the 22-day experimental period, emissions from the slurry N pool were strongly reduced by DMPP from 0.93 kg N(2)O-N ha(-1) (-DMPP) to 0.50 kg N(2)O-N ha(-1) (+DMPP), while only a minor effect on emissions from the soil N pool was observed (0.69 to 0.60 kg N(2)O-N ha(-1); -DMPP, +DMPP, respectively) . J Am Chem Soc, 2001 Apr 4, 123(13), 2997 - 3005 Correlations of structure and electronic properties from EPR spectroscopy of hydroxylamine oxidoreductase; Hendrich MP et al.; Hydroxylamine oxidoreductase (HAO) from the autotrophic nitrifying bacterium Nitrosomonas europaea catalyzes the oxidation of NH(2)OH to HNO(2) . The enzyme contains eight hemes per subunit which participate in catalytic function and electron transport . The structure of the enzyme shows a unique spatial arrangement of the eight hemes, subsets of which are now observed in four other proteins . The spatial arrangement displays three types of diheme pairing motifs . At least four of the eight hemes are electronically coupled in two distinguishable pairs and one of these pairs is at the active site of the enzyme . Here, the use of quantitative simulation of the EPR signals allows determination of exchange couplings, and assignments of signals and reduction potentials to hemes of the crystal structure . The absence of any obvious heme-to-heme bonding pathway in the crystal structure suggests that the observed exchange interactions are derived from direct electronic overlap of porphyrin orbitals . This provides evidence for heme pairs which function as biological two-electron redox centers in electron-transfer processes. Water Res, 2001 Aug, 35(11), 2774 - 8 Application of the 15N technique to determine the contributions of nitrification and denitrification to the flux of nitrous oxide from aerated pig slurry; Beline F et al.; In order to elucidate and quantify nitrogen transformations occurring during aerobic treatment of pig slurry, two laboratory experiments were carried out with contrasting levels of aeration, high level (experiment 1) and low level (experiment 2) of aeration . During these experiments, after reaching steady-state conditions, a single pulse of NO3(-)-15N tracer was added directly to the reactor . When nitrification conditions were prevailing (experiment 1), no transformation of added NO3(-)-15N occurred (98.7% 15N-recovery as nitrates in the liquid slurry) . Moreover, the unlabelled nitrous oxide (N2O) measured (7.4% of the total nitrogen content of the raw slurry) strongly demonstrated that the source of N2O emitted was nitrification . During simultaneous nitrification and denitrification conditions (experiment 2), the added NO3(-)-15N was found in gaseous nitrogen forms (N2O-15N: 27%; N2-15N: 18%) and in the liquid (TN-15N: 54%) . From this result, it was evident that N2O was mainly emitted by denitrification process . Using the decrease of the isotopic excess of the NO3(-)-15N we calculated that 92% of NO2(-)-N was directly denitrified (as gaseous forms) without any previous oxidation to nitrate. Water Res, 2001 Aug, 35(11), 2731 - 9 In situ analysis of Nitrosomonas spp . in wastewater treatment wetland biofilms; Silyn-Roberts G et al.; The presence of the ammonia-oxidising group Nitrosomonas in developing biofilms from a subsurface flow dairy effluent treatment wetland was investigated using in situ hybridisation and a crude semi-quantitative PCR . Fluorescently labelled oligonucleotide probes, specific for the Nitrosomonas europaea and Nitrosomonas eutropha species, showed that nitrifying bacteria were present from the onset of biofilm development but that over a five month period the proportions remained low (averaging less than 1% of the total bacterial population) . The greatest presence of these nitrifiers was found in the second trench of the subsurface flow wetland . Nitrosomonas were also found to be susceptible to environmental change; adverse environmental conditions, such as low temperatures, coincided with negligible Nitrosomonas presence throughout the wetland . However, during one period of elevated ammonium concentrations Nitrosomonas presence rapidly increased as high as 7% of the total bacterial population . Investigations of relative occurrence of effluent bacterial population of Nitrosomonas europaea and the biofilm populations showed that Nitrosomonas presence in the effluent coincided with significant presence in adjacent biofilms . This suggests seeding between both sessile and planktonic populations of this species . Nitrosomonas occurred as single cells in biofilms throughout the study and were never observed as dense clusters. Colloids Surf B Biointerfaces, 2001 Oct, 22(2), 149 - 157 Soft particle analysis of bacterial cells and its interpretation of cell adhesion behaviors in terms of DLVO theory; Hayashi H et al.; The electrokinetic properties of two nitrifying strains, Nitrosomonas europaea and Nitrobacter winogradskyi, and three heterotrophic bacteria, Escherichia coli, Pseudomonas putida and Pseudomonas aeruginosa, were examined by electrophoretic mobility measurement and analyzed using the soft particle electrophoresis theory that is suitable for biological particles . The bacterial adhesion characteristics onto glass bead substratum were also evaluated by packed bed method . The mobility of the bacterial cells employed converged to a non-zero value as the ionic concentration increased, suggesting that the bacterial cells exhibited typical soft particle characteristics . Moreover, cell surface potentials based on the soft particle theory were lower than those estimated by the conventional Smoluchowski formula, i.e . zeta potential . Cell collision efficiencies onto glass beads (alpha(0)) were largely dependent on interfacial interaction, although almost electrically neutral P . aeruginosa did not follow that trend . From a comparison of alpha(0) with DLVO interaction energy maximum (V(max)), it was assumed that heterocoagulation between cell and substratum at primary minimum potential took place under V(max) of 24-34 kT based on soft particle analysis . On the other hand, V(max) predictions using the Smoluchowski theory gave 81-223 kT, which indicated the possibility of overestimating electrostatic repulsive forces by the conventional Smoluchowski theory . Thus, the application of this new electrophoresis theory to several kinds of bacterial cells has led to the revision of the interpretation of bacterial mobility data and provided a more detailed understanding of the bacterial adhesion phenomenon. Water Sci Technol, 2001, 43(11), 59 - 66 Potential and limitations of alum or zeolite addition to improve the performance of a submerged membrane bioreactor; Lee JC et al.; In this study, alum and natural zeolite were added to a submerged membrane bioreactor (MBR) not only to reduce membrane fouling but also to increase the removal of nitrogen and phosphorus . Alum addition reduced significantly the rising rate of suction pressure and also resulted in stable and better COD removal . Although phosphorus removal was more than 90% by chemical precipitation, nitrification inhibition was observed . With the addition of natural zeolite, membrane permeability was greatly enhanced by the formation of rigid floc that had lower specific resistance than that of the control activated sludge floc . In particular, the nitrification efficiency was over 95% even at N-shock loading due to the ion-exchange capacity of zeolite . The mechanisms for improved membrane permeability through alum or zeolite addition were discussed in detail. Water Sci Technol, 2001, 43(11), 43 - 50 Effect of solids retention time on the performance and biological characteristics of a membrane bioreactor; Cicek N et al.; The purpose of this study was to compare the performance of a pilot-scale membrane bioreactor (MBR) in the treatment of municipal strength wastewater at solid retention times (SRTs) ranging from 30 days to two days . Cumulative nitrogen and phosphorus mass balances resulted in closures exceeding 90% at each steady state period . Biomass production rate and biomass viability generally increased with decreasing SRT, whereas overall enzymatic activity did not change significantly at most SRTs, but was highest at the two day SRT . Nitrification decreased at two day SRT but did not fail completely . At higher SRTs, nitrification was not noticeably affected by the sludge age . Phospholipid fatty acid (PLFA) analysis showed substantially diverse biomass in the sludge at different SRTs . Different ratios of gram positive bacteria, eukaryotic organisms, and yeast cells were observed in the mixed liquor at varying SRTs . On the other hand, BIOLOG analysis indicated that the overall capacity of the biomass to degrade different carbon substrates did not change significantly at different SRTs . The concentration of metals in the MBR mixed liquor declined steadily with decreasing SRT . The MBR effluent contained negligible amounts of Fe, Zn, Mn, and Co at each condition, indicating the retention of these metals regardless of the SRT. Water Sci Technol, 2001, 43(11), 309 - 14 Control measures for wastewater treatment plants during storm flow; Niemann K et al.; In the context of the development of treatment plant control techniques, three measures for maintaining a high efficiency of treatment plants during rainfall events were tested . The three measures are increasing the nitrification volume by operating a facultative aeration, bypassing the primary sedimentation and adding flocculants before secondary sedimentation . Ammonia concentrations and ammonia loads were used in combination with rainfall forecasts as the criteria for putting the measures into operation . A simulation based on the Activated Sludge Model No . 1 and a pilot scale plant were used for testing the measures . The results show that all three measures may be suitable to cope with peak loads of treatment plants during rainfall events. Water Sci Technol, 2001, 43(11), 197 - 204 Experimental considerations on monitoring ORP, pH, conductivity and dissolved oxygen in nitrogen and phosphorus biological removal processes; Spagni A et al.; An experimental study on monitoring Oxidation Reduction Potential (ORP), pH, Conductivity and Dissolved Oxygen (DO) in an Enhanced Biological Nutrient Removal process has been carried out . In the anaerobic phase, while ORP and conductivity were not reliable in monitoring simultaneously denitrification and P-release, pH showed the best performances . A significant relationship between P-released and pH variation was found . During the aerobic phase both ORP and pH were able to monitor successfully the nitrification, even though pH was much more reliable . pH can be also used for monitoring and control enhanced P-uptake . It has been concluded that, for a reliable and effective control of biological N and P removal processes a more sophisticated control system seems to be necessary. Water Sci Technol, 2001, 43(11), 153 - 60 Kinetic start-up performance of two large treatment plants for nutrient removal; Haarbo A et al.; In 1987 an action plan was passed in the Danish Parliament demanding a considerable reduction of the discharge of nutrients to the aquatic environment in Denmark . Consequently, the two largest wastewater treatment plants in the Copenhagen area had to be upgraded to include nutrient removal . For more than 8 years an extensive effort has been made to determine an optimum solution for this upgrading from a technical and financial point of view . The work included six years of comprehensive pilot plant investigations with the aim of thoroughly studying and interpreting the kinetics of the processes involved . The investigations revealed valuable information particularly concerning limitations of the nitrification process . Consequently, the investigations contributed to an expectation of no unforeseen problems during the implementation of the upgraded plants . This paper presents the results of the start-up of the two full-scale plants with the main emphasis laid on the kinetic performance in relation to the information achieved from the pilot tests . The results showed that the start-up of the full scale plants proceeded with great accuracy as expected from the investigations . Accordingly, the implementation of the plants was carried out successfully, ending an era of more than 10 years in total. Water Sci Technol, 2001, 43(11), 127 - 34 Full-scale application of the SHARON process for treatment of rejection water of digested sludge dewatering; Mulder JW et al.; At the Rotterdam Dokhaven WWTP the first full-scale application of the SHARON process has been constructed . In the SHARON process, rejection water from dewatering of digested sludge is treated for N-removal . It concerns a highly active process operating without sludge retention . The single tank reactor is intermittently aerated . Due to differences in growth rate nitrite oxidisers are washed out of the system while ammonia oxidisers can be maintained, resulting in N-removal over nitrite . The SHARON process has been selected after comparison with several other techniques . The feed of the SHARON tank is concentrated, with ammonia concentrations over 1 g N/l . The first results show that conversion rates of 90% are quite possible with N-removal mainly via the nitrite route . The process was shown to be stable . Due to the high inlet concentrations pH control is of great importance, preventing process inhibitions . The acidifying effect of nitrification can be compensated completely by CO2 stripping during aeration and by denitrification . Heat production by biological conversions appeared to be significant, due to the high inlet concentrations, and contributes to the optimal operating temperature of 30-40 degrees C. Water Sci Technol, 2001, 43(10), 133 - 8 How partial nitrification could improve reclaimed wastewater transport in long pipes; Delgado S et al.; Reclaimed wastewater transport is studied in a concrete-lined cast iron pipe, where a nitrification-denitrification process occurs . The pipe is part of the Reuse System of Reclaimed Wastewater of South Tenerife (Spain), 0.6 m in diameter and 61 km long . In order to improve wastewater quality, at 10 km from the inlet there is injection of fresh water saturated in dissolved oxygen (DO), after which a fast nitrification process usually appears (less than two hours of space time) . The amount of oxidized nitrogen compounds produced varies between 0.8 and 4.4 mg/l NOx(-)-N . When DO has disappeared, a denitrification process begins . The removal of nitrite is complete at the end of the pipe, whereas the nitrate does not disappear completely, leaving a concentration of about 0.4-0.5 mg/l . For a COD/NOx(-)-N ratio higher than 5, a first order nitrification rate in NOx(-)-N has resulted, with the constant k20 = 0.079 h-1, for a NOx(-)-N concentration range of 0.8-4.4 mg/l . Finally the following temperature dependency for the first order denitrification rate constant has been found: k = k20 x 1 x 15T-20 . Although nitrogen could be used as nutrient in the agricultural reuse, its removal from reclaimed wastewater could be useful in order to diminish the chlorine needs for reclaimed wastewater disinfection. Water Sci Technol, 2001, 43(10), 125 - 32 Ammonia removal in a deep reclaimed wastewater reservoir before agricultural reuse; Delgado S et al.; An experimental study has been carried out to determine the ammonia removal in a deep reclaimed wastewater reservoir of 50,000 m3 . The reservoir is part of the Reuse System of Reclaimed Wastewater of South Tenerife (Spain) . The study has been conducted under batch mode operation, in three different periods (winter, spring-summer and winter-spring), with an average storage time of 85 days . Vertical profiles of temperature, dissolved oxygen and pH were determined together with NH3-N, NO2-N and NO3-N concentrations at different points and different depths in the reservoir . Maximum removal efficiency was obtained during the winter periods, in absence of stratification and with good mixing conditions throughout the water column . During these periods, nitrification took place in some extension, favoring the ammonia removal . Average NH3-N concentrations in the reservoir were calculated and apparent first-order rate constants were determined for different stratification conditions . Although ammonia nitrogen could be used as nutrient in the agricultural reuse, its removal from reclaimed wastewater could be useful in order to diminish the chlorine needs for disinfection. Appl Environ Microbiol, 2001 Jul, 67(7), 2952 - 7 Autotrophic ammonia oxidation at low pH through urea hydrolysis; Burton SA et al.; Ammonia oxidation in laboratory liquid batch cultures of autotrophic ammonia oxidizers rarely occurs at pH values less than 7, due to ionization of ammonia and the requirement for ammonium transport rather than diffusion of ammonia . Nevertheless, there is strong evidence for autotrophic nitrification in acid soils, which may be carried out by ammonia oxidizers capable of using urea as a source of ammonia . To determine the mechanism of urea-linked ammonia oxidation, a ureolytic autotrophic ammonia oxidizer, Nitrosospira sp . strain NPAV, was grown in liquid batch culture at a range of pH values with either ammonium or urea as the sole nitrogen source . Growth and nitrite production from ammonium did not occur at pH values below 7 . Growth on urea occurred at pH values in the range 4 to 7.5 but ceased when urea hydrolysis was complete, even though ammonia, released during urea hydrolysis, remained in the medium . The results support a mechanism whereby urea enters the cells by diffusion and intracellular urea hydrolysis and ammonia oxidation occur independently of extracellular pH in the range 4 to 7.5 . A proportion of the ammonia produced during this process diffuses from the cell and is not subsequently available for growth if the extracellular pH is less than 7 . Ureolysis therefore provides a mechanism for nitrification in acid soils, but a proportion of the ammonium produced is likely to be released from the cell and may be used by other soil organisms. Water Sci Technol, 2001, 43(9), 133 - 44 The use of artificial oxygenation to reduce nutrient availability in the Canning River, Western Australia; Greenop B et al.; Artificial oxygenation has been used for two summer periods to improve the water quality of the Canning River in Perth, Western Australia . The project is part of the Swan Canning Cleanup Program, which aims to reduce the frequency and severity of nuisance and toxic algal blooms in the Swan-Canning estuary . The trials have proved that oxygenation has increased the dissolved oxygen concentrations in the water column, particularly in the bottom waters where dissolved oxygen concentrations are frequently below a critical level of three milligrams per litre . Oxygenation has had a positive impact on nutrient concentrations in the water column and nitrogen cycling processes . Reductions in nutrient concentrations were highlighted by drops in ammonium and total phosphorus concentrations of 97% and 64% following the recommencement of oxygenation after a plant shutdown . Results of a microbiological study combined with the data analysis indicate that the number of nitrifying microbes have increased due to oxygenation . However, comparisons between oxygenated and control areas were inconclusive about the ability of the oxygenation plant to reduce total nitrogen and phosphorus levels . This could be explained by factors such as spatial variability, water flow during the trials and measurement limitations in the monitoring program . Future work will concentrate on assessing the impact of the oxygenation plant on nutrient concentrations. J Environ Sci Health B, 2001 Mar, 36(2), 161 - 75 Response of the bacteria and fungi of two soils to the sulfonylurea herbicide cinosulfuron; Allievi L et al.; Changes in aerobic bacteria and autotrophic nitrifier numbers, and in respiration and nitrification in two soils treated with cinosulfuron at 42 (field rate) and 4200 microg/kg were studied after 1 and 4 weeks of incubation under laboratory conditions . Only nitrification at 1 week was slightly inhibited by the cinosulfuron treatment, even at the field rate . In vitro toxicity tests carried out in agar media on representative aerobic bacteria, fungi and Azotobacter strains isolated from the two soils, as well as on nine collection soil bacteria, showed that only a very high cinosulfuron concentration (100 mg/l) can have negative effects on the growth of a limited number of soil heterotrophic microorganisms, under conditions similar to those of soil environment . The absence of three branched-chain amino acids increased bacterial sensitivity, thus showing the importance of the chemical conditions and suggesting acetolactate synthase enzyme blockage as the toxicity mechanism . It is concluded that cinosulfuron has a negative effect on only a few aspects of the microbial community in soil ecosystems, even at concentrations higher that those currently in use. Lett Appl Microbiol, 2001 Jun, 32(6), 398 - 401 (13)C incorporation into DNA as a means of identifying the active components of ammonia-oxidizer populations; Whitby CB et al.; AIMS: To identify active CO2-assimilating species of ammonia-oxidizing bacteria in fresh water sediment . METHODS AND RESULTS: Enrichment cultures were incubated in the presence of 13C labelled CO2, and 13C-DNA successfully resolved from 12C-DNA by caesium chloride density gradient ultracentrifugation of DNA extracts . Ammonia-oxidizer DNA recovered from these gradients was amplified and characterised by Temporal Temperature Gradient Gel Electrophoresis (TTGE), with confirmatory sequence analysis to identify the metabolically active components of the population . CONCLUSION: The 12C-DNA fraction was dominated by nitrosospiras, in contrast to the 13C-DNA fraction which was largely nitrosomonad DNA, in support of the hypothesis that nitrosomonads out-compete nitrosospiras in laboratory culture . Significance and Impact of the Study: The use of stable isotype incorporation into ammonia-oxidizer DNA could therefore circumvent the problems associated with RNA detection to identify metabolically active species in situ. Lett Appl Microbiol, 2001 Jun, 32(6), 388 - 93 In situ reverse transcription to detect the cbbL gene and visualize RuBisCO in chemoautotrophic nitrifying bacteria; Sinigalliano CD et al.; AIMS: In situ methodologies targeting the cbbL gene were used to visualize cells of nitrifying bacteria . Both procaryotic in situ PCR (IS-PCR) and in situ reverse transcription (ISRT) protocols were employed to determine gene presence and expression, respectively . METHODS AND RESULTS: Aged-oligotropic seawater samples were inoculated with microbial assemblages containing a mixture of actively growing nitrifying bacteria, starved nitrifying bacteria, and heterotrophic bacteria without cbbL . After the molecular manipulations, we found that while all the nitrifiers (healthy or starved) with the cbbL gene were detected by IS-PCR, only the actively growing autotrophic nitrifiers with detectable levels of carbon fixation and nitrification activity were detected by ISRT analysis . CONCLUSION: These results show how IS-PCR and ISRT supplement each other, and their potential for the analysis of heterogeneous populations where an assortment of healthy and starved/dormant cells are expected. Water Res, 2001 Jul, 35(10), 2403 - 10 Simultaneous organic and nitrogen removal from municipal landfill leachate using an anaerobic-aerobic system; Im JH et al.; An anaerobic-aerobic system including simultaneous methanogenesis and denitrification was introduced to treat organic and nitrogen compounds in immature leachate from a landfill site . Denitrification and methanogenesis were successfully carried out in the anaerobic reactor while the organic removal and nitrification of NH4+,-N were carried out in the aerobic reactor when rich organic substrate was supplied with appropriate hydraulic retention time . The maximum organic removal rate was 15.2 kg COD/m3 d in the anaerobic reactor while the maximum NH4+-N removal rate and maximum nitrification rate were 0.84kg NH4+-N/m3/d and 0.50kg NO3--N/m3/d, respectively, in the aerobic reactor . The pH range for proper nitrification was 6-8.8 in the aerobic reactor . The organic compounds inhibited nitrification so that the organic removal in the anaerobic reactor could enhance the nitrification rate in the following aerobic reactor . The gas production rate was 0.33 m3/kg COD and the biogas compositions of CH4, CO2, and N2 were kept relatively constant, 66-75, 22-32, and 2-3%, respectively. Antonie Van Leeuwenhoek, 2001 Jan, 79(1), 39 - 47 Effects of gaseous NO2 on cells of Nitrosomonas eutropha previously incapable of using ammonia as an energy source; Schmidt I et al.; Cells of Nitrosomonas eutropha grown under anoxic conditions with hydrogen as electron donor and nitrite as electron acceptor were initially unable to oxidize ammonia (ammonium) and hydroxylamine when transferred to oxic conditions . Recovery of ammonia and hydroxylamine oxidation activity was dependent on the presence of NO2 . Under oxic conditions, without addition of NO2, ammonia consumption started after 8 - 9 days, and small amounts of NO and NO2 were detectable in the gas atmosphere . Removing these nitrogen oxides by intensive aeration, ammonia oxidation activity decreased and broke off after 15 days . Addition of gaseous NO2 (25 ppm1) led to a fast recovery of ammonia oxidation (3 days) . Simultaneously, the arrangement of intracytoplasmic membranes (ICM) changed from circular to flattened vesicles, the protein pattern revealed an increase in the concentration of a 27 and a 30 kDa polypeptide, and the cytochrome c content increased significantly. Microb Ecol, 2001 Apr, 41(3), 272 - 280 Influence of Initial C/N Ratio on Chemical and Microbial Composition during Long Term Composting of Straw; Eiland F et al.; Shredded straw of Miscanthus was composted in 800-L boxes with different amounts of pig slurry added as nitrogen source . The impact of the different initial C/N ratios (11, 35, 47, 50, and 54) on the composting process and the end product was evaluated by examining chemical and microbiological parameters during 12 months of composting . Low initial C/N ratios caused a fast degradation of fibers during the first three months of composting (hemicellulose: 50-80%, cellulose: 40-60%), while high initial C/N ratios resulted in 10-20% degradation of both hemicellulose and cellulose . These differences were reflected in the microbial biomass and respiration, which initially were higher in low C/N treatments than in high C/N treatments . After 12 months of composting, this situation was reversed . Composts with high initial C/N ratios had high microbial biomass (15-20 mg ATP g-1 OM) and respiration rates (200 mg CO2 h-1 g-1 OM) compared to treatments with low initial C/N ratios (less than 10 mg ATP g-1 OM and 25 mg CO2 h-1 g-1 OM) . This could be explained by the microorganisms being nitrogen limited in the high C/N ratio treatments . In the low C/N ratio treatments, without nitrogen limitation, the high activity in the beginning decreased with time because of exhaustion of easily available carbon . Different nitrogen availability was also seen in the nitrification patterns, since nitrate was only measured in significant amounts in the treatments with initial C/N ratios of 11 and 35 . The microbial community structure (measured as phospholipid fatty acid, PLFA, profile) was also affected by the initial C/N ratios, with lower fungal/bacterial ratios in the low compared to the high C/N treatments after 12 months of composting . However, in the low C/N treatments higher levels of PLFAs indicative of thermophilic gram-positive bacteria were found compared to the high C/N treatments . This was caused by the initial heating phase being longer in the low than in the high C/N treatments . The different fungal/bacterial ratios could also be explained by the initial heating phase, since a significant correlation between this ratio and heat generated during the initial composting phase was found. Water Sci Technol, 2001, 43(7), 65 - 72 Evaluation of pH inhibition effect on activated sludge by the pseudo toxic concentration (CPT) concept model; Ko JH et al.; It is generally accepted that the inhibition effect of pH on activated sludge follows the non-competitive inhibition kinetics . But the non-competitive inhibition kinetic equation cannot be directly applied to pH inhibition, due to the difficulty in quantification of pH as a term of inhibitor concentration . So, many empirical equations were developed especially for acidic condition to describe pH inhibition effect . In this research, the pseudo toxic concentration (CPT) concept model to quantify pH inhibition effect on activated sludge was proposed and compared with other existed models . Prediction of performance, presented by Prediction Accuracy and Prediction Accuracy Index, showed that the CPT concept model can explain the reduction of the maximum specific growth rate (mu max) more accurately than any other models do at a wide range of pH . The CPT concept model was applicable not only to activated sludge but also to specific microorganism groups, such as nitrifier, less acidophilic species and nitrifying biofilm. Water Sci Technol, 2001, 43(7), 347 - 55 Practical identifiability of model parameters by combined respirometric-titrimetric measurements; Petersen B et al.; An earlier study on theoretical identifiability of parameters for a two-step nitrification model showed that a unique estimation of the yield YA1 is possible with combined respirometric-titrimetric data, contrary to the case where only one type of measurement is available . Here, the practical identifiability of model parameters was investigated via evaluation of the output sensitivity functions and the corresponding Fisher Information Matrix (FIM) . It appeared that the FIM was not sufficiently powerful to predict the practical identifiability of this case with combined measurements as parameters could indeed be identified despite the fact that the FIM became singular . The accuracy of parameter estimates based on respirometric and titrimetric data and combination thereof was also investigated . Estimation on titrimetric data (Hp) was very accurate and a fast convergence of the objective function towards a minimum was obtained . The latter also holds for estimation on oxygen uptake rate data (rO), however with a lower accuracy . Parameter estimation based on oxygen concentration data (SO) was more complex but resulted in a higher accuracy . Thus, when the highest accuracy is needed it is recommended to estimate parameters initially on Hp and/or rO data, and to subsequently use these parameters as initial values for final, and more accurate estimation on SO data. Huan Jing Ke Xue, 2001 Jan, 22(1), 57 - 61 {Effect of LAS on physico-chemical properties and microorganism activity in soil environment}; Pan G et al.; Using a well drained paddy soil and the derived soil under vegetables in the Taihu Lake region, China, experiments of soil capillary rise, colloid dispersion and adsorption of toxic organics and heavy metals by soil under various degrees of LAS addition were conducted . Also incubation experiments of microorganism activity in soil with added LAS in different concentrations were carried out in laboratory . LAS addition resulted in lower capillary rise of soil solution, higher dispersion of soil colloids and lower capacity of soil for organic pollutants but no significant influence on adsorption of heavy metal cations . The nitrification and amonification in soil were very sensitive to LAS stress while denitrification turned to be stimulated . LAS addition gave stronger growth of soil bacteria while decreased growth of fungus . Meanwhile, soil respiration was stimulated in the first week of incubation and compressed afterwards by LAS at concentration over 5 mg/kg . It seemed that some species of microorganisms were tolerant of LAS in the studied soils. Water Sci Technol, 2000, 41(3), 247 - 54 Microbially mediated attenuation potential of landfill bioreactor systems; Pohland FG et al.; The origin and fate of landfill leachate and gas constituents generated during the sequential phases of solid waste transformation and stabilization are emphasized within the perspective of the in situ processes of microbially mediated attenuation . The fundamental biochemical and physicochemical reaction mechanisms are presented in terms of their spatial and temporal dimensions and their significance for transformation of both nonhazardous and hazardous waste constituents . Supporting information from laboratory, pilot-scale and full-scale applications is used as a basis for interpretive analysis and for providing operational guidance and promoting future developments . The diversity, domains, and functional interdependence of the acidogenic, methanogenic, sulfate and nitrate reducing, nitrifying and denitrifying, and methanotrophic consortia are addressed in order to reveal opportunities for landfill process modifications and associated operational optimization . Controlled attenuation, linked with operational and regulatory realities, are used to suggest innovative landfill configurations involving prospective compartmentalization and integrated waste loading, dedicated treatment zones for in situ transformation of waste and leachate constituents with associated gas capture, control and utilization . Monitoring requirements are emphasized to provide guidance and feedback for operational control and environmental compliance . Finally, technology needs for establishing a more unified approach to the development and management of bioreactor landfills are presented. Water Sci Technol, 2001, 43(6), 197 - 204 Enhancement of nitrifying biofilm formation using selected EPS produced by heterotrophic bacteria; Tsuneda S et al.; The possibility of enhancing nitrifying biofilm formation rate with the aid of selected EPS produced by heterotrophic bacteria was investigated . When EPS production characteristics were examined for four kinds of heterotrophs isolated from a domestic wastewater treatment reactor, two strains obtained from biofilms (B1, B2) exhibited a higher polysaccharide production rate than those from suspended flocs (A1, A2) . Among EPS components, the concentration of uronic acids gave a good correlation with flocculation ability, which suggests that acidic polysaccharides play a major role in bioaggregate formation . Addition of 1 g/L D-glucuronic acid as an EPS substitute enhanced the homocoagulation rate of autotrophic Nitrosomonas europaea and altered its zeta potential from n30.4 mV to +4.3 mV, which indicates a possibility that particular EPS components produced by heterotrophs are utilized as neutralising reagents for nitrifying biofilm formation . Moreover, when heterotrophic isolates with Nitrobacter winogradskyi were cultured in batch with fabric supports, biofilm formed on the substratum . These experimental results suggest the application of selected EPS for enhancing nitrifying biofilm formation. Water Sci Technol, 2001, 43(6), 185 - 92 Extracellular polymeric substances in relation to nutrient removal from a sequencing batch biofilm reactor; Choi E et al.; Experimental investigations were performed to determine the possibility of simultaneous biological nitrogen and phosphorus removal during various biofilm processes in conjunction with biofilm characterisation, especially extracellular polymeric substance (EPS) . Since biologial nitrogen removal requires an alternating exposure of anaerobic-anoxic-oxic conditions in the bulk liquid that surrounds the biofilm growth media, a sequencing batch reactor (SBR)-type operation was used . Various materials including expanded clay, polystyrene, polyurethane, and acrylic materials were used as the biofilm growth support medium . Simultaneous nitrogen and phosphorus removal was possible with SBR, but it was postulated that nutrient removal efficiencies varied with film thickness . Thinner biofilm promoted nitrification and phosphorus removal, but thicker biofilm enhanced denitrification and reduced phosphorus removal . EPS contents were similar regardless of support media types or biofilm configuration, but EPS contents gradually increased as the film growth continued after backwashing . EPS contents were increased with increased nitrogen removal, but it was difficult to define its relation with phosphorus removal . In addition, suspended solids removal was correlated well with the EPS content in the biofilms. Water Sci Technol, 2001, 43(6), 135 - 41 Effect of EPS on biofilm structure and function as revealed by an individual-based model of biofilm growth; Kreft JU et al.; We have simulated a nitrifying biofilm with one ammonia and one nitrite oxidising species in order to elucidate the effect of various extracellular polymeric substance (EPS) production scenarios on biofilm structure and function . The individual-based model (IbM) BacSim simulates diffusion of all substrates on a two-dimensional lattice . Each bacterium is individually simulated as a sphere of given size in a continuous, three-dimensional space . EPS production kinetics was described by a growth rate dependent and an independent term (Leudeking-Piret equation) . The structure of the biofilm was dramatically influenced by EPS production or capsule formation . EPS production decreased growth of producers and stimulated growth of non-producers because of the energy cost involved . For the same reason, EPS accumulation can fall as its rate of production increases . The patchiness and roughness of the biofilm decreased and the porosity increased due to EPS production . EPS density was maximal in the middle of the vertical profile . Introduction of binding forces between like cells increased clustering. Water Sci Technol, 2001, 43(3), 9 - 18 Nitrification in sequencing biofilm batch reactors: lessons from molecular approaches; Daims H et al.; The nitrifying microbial diversity and population structure of a sequencing biofilm batch reactor receiving sewage with high ammonia and salt concentrations (SBBR 1) was analyzed by the full-cycle rRNA approach . The diversity of ammonia-oxidizers in this reactor was additionally investigated using comparative sequence analysis of a gene fragment of the ammonia monooxygenase (amoA), which represents a key enzyme of all ammonia-oxidizers . Despite the "extreme" conditions in the reactor, a surprisingly high diversity of ammonia- and nitrite-oxidizers was observed to occur within the biofilm . In addition, molecular evidence for the existence of novel ammonia-oxidizers is presented . Quantification of ammonia- and nitrite-oxidizers in the biofilm by Fluorescent In situ Hybridization (FISH) and digital image analysis revealed that ammonia-oxidizers occurred in higher cell numbers and occupied a considerably larger share of the total biovolume than nitrite-oxidizing bacteria . In addition, ammonia oxidation rates per cell were calculated for different WWTPs following the quantification of ammonia-oxidizers by competitive PCR of an amoA gene fragment . The morphology of nitrite-oxidizing, unculturable Nitrospira-like bacteria was studied using FISH, confocal laser scanning microscopy (CLSM) and three-dimensional visualization . Thereby, a complex network of microchannels and cavities was detected within microcolonies of Nitrospira-like bacteria . Microautoradiography combined with FISH was applied to investigate the ability of these organisms to use CO2 as carbon source and to take up other organic substrates under varying conditions . Implications of the obtained results for fundamental understanding of the microbial ecology of nitrifiers as well as for future improvement of nutrient removal in wastewater treatment plants (WWTPs) are discussed. Water Sci Technol, 2001, 43(3), 85 - 91 Feedforward aeration control of a Biocos wastewater treatment plant; Wett B et al.; The Biocos strategy as a cyclical time controlled activated sludge system shows a great variability in operation and control . One topic such a type of treatment plant has to deal with is the optimum relation between aerobic and anoxic conditions . The aeration control has to adapt the length of the nitrification phases to the current constraints in order to save operational costs and maximise nitrogen elimination . Since wastewater treatment plants up to a certain size are usually not equipped with on-line nitrogen probes, influent flow and temperature can be taken as control parameters for the aeration system . The defined relation between influent flow and ammonia load is based on measurements and the relation between ammonia load and required aeration time is model based. Water Sci Technol, 2001, 43(3), 69 - 76 Implementation, study and calibration of a modified ASM2d for the simulation of SBR processes; Marsili Libelli S et al.; An enhanced process model for SBRs has been developed . Though the basic mechanism largely draws on the Activated Sludge Model n . 2d, its new features are the splitting of the nitrification stage in a two-step process, according to the well known Nitrosomonas-Nitrobacter oxidation sequence, and an improved XPAO dynamics, involved in the anaerobic/aerobic phosphorus removal process . The model was implemented through the DLL technique allowing complied C++ modules to be linked to an ordinary Simulink block diagram . The static sensitivity study revealed that if the parameter vector is partitioned into subsets of biologically related parameters and calibrated separately, the calibration procedure does not present particularly difficult aspects . Trajectory sensitivity showed also to which extent data collection could be optimised in order to improve calibration accuracy . The study of the shape of the error functional generated by parameters couples allows a much more effective calibration strategy. Water Sci Technol, 2001, 43(3), 61