Water Res, 2003 Dec, 37(20), 4873 - 84 Stability of the bacterial community in a pulp mill effluent treatment system during normal operation and a system shutdown; Smith NR et al.; Currently, very little is known about the normal dynamics of microbial populations in wastewater treatment systems and the relationship between population dynamics and functional stability of treatment systems . We monitored the bacterial community in an oxygen activated sludge system at a pulp and paper mill during a 55-day period that included normal operation as well as an 11-day shutdown of the system and the subsequent start-up . Ribosomal intergenic spacer (RIS) length polymorphism fingerprints were very similar (57-88% similar) throughout the study period . Analysis of clone libraries of RIS-rRNA gene amplicons indicated that Proteobacteria affiliated with the genera Paracraurococcus and Acidovorax as well as a Green Nonsulfur Bacterium affiliated with the genus Roseiflexus were consistently among predominant members of the community . By comparison, wastewater treatment systems from different pulp mills yielded dissimilar fingerprints (9-17% similar), and their clone libraries had distinct predominant phylotypes . Our analysis strongly suggests that the composition of the bacterial community in the former treatment system was stable during normal operation as well as the shutdown and start-up . This stability coincided with functional stability, including consistent and nearly complete removal of biological oxygen demand. Appl Environ Microbiol, 2003 Nov, 69(11), 6597 - 604 Power analysis for real-time PCR quantification of genes in activated sludge and analysis of the variability introduced by DNA extraction; Dionisi HM et al.; The aims of this study were to determine the power of discrimination of the real-time PCR assay for monitoring fluctuations in microbial populations within activated sludge and to identify sample processing points where methodological changes are needed to minimize the variability in target quantification . DNA was extracted using a commercially available kit from mixed liquor samples taken from the aeration tank of four bench-scale activated-sludge reactors operating at 2-, 5-, 10-, and 20-day solid retention times, with mixed-liquor volatile suspended solid (MLVSS) values ranging from 260 to 2,610 mg/liter . Real-time PCR assays for bacterial and Nitrospira 16S rRNA genes were chosen because they represent, respectively, a highly abundant and a less-abundant bacterial target subject to clustering within the activated sludge matrix . The mean coefficient of variation in DNA yields (measured as microgram of DNA per milligram of MLVSS) in triplicate extractions of 12 different samples was 12.2% . Based on power analyses, the variability associated with DNA extraction had a small impact on the overall variability of the real-time PCR assay . Instead, a larger variability was associated with the PCR assay . The less-abundant target (Nitrospira 16S rRNA gene) had more variability than the highly abundant target (bacterial 16S rRNA gene), and samples from the lower-biomass reactors had more variability than samples from the higher-biomass reactors . Power analysis of real-time PCR assays indicated that three to five samples were necessary to detect a twofold increase in bacterial 16S rRNA genes, whereas three to five samples were required to detect a fivefold increase in Nitrospira 16S rRNA genes. Environ Technol, 2003 Sep, 24(9), 1147 - 56 Use of a similarity index based on microbial fatty acid (MFA) analysis to monitor biological wastewater treatment systems; Son KS et al.; Estimating the stability of microbial community structures may be useful in advanced biological wastewater treatment system design and operation . In this research, a monitoring method using fatty acid profiles was evaluated for detecting changes in microbial community structures . For the evaluation, the operating parameters such as pH, organic loading, and chlorine addition were varied in two identical laboratory scale conventional activated sludge systems . A similarity index based on microbial fatty acid analysis was used to express the stability of microbial community structures in the systems . Experiments using a model microbial community showed that microbial compositions changed daily even under constant operating conditions and that the rate of change increased under dynamic operating conditions . Substrate changes brought about a relatively large change in a microbial community structure, eventually resulting in a very different microbial community . After only 7 days following a substrate change in a lab-scale bioreactor, the biomass exhibited only 45% similarity to the original structure . The analysis of microbial fatty acids conveys additional information, in that it could be used for the calculation of biomass concentrations in a wastewater treatment system if microbial fatty acid analyses are executed on a routine basis as a monitoring tool for biological wastewater treatment systems . The total fatty acid concentrations were about 0.61% of the biomass concentration as mixed liquor volatile suspended solid concentrations in this research. Bioresour Technol, 2004 Jan, 91(2), 201 - 6 Thermal-alkaline solubilization of waste activated sludge as a pre-treatment stage for anaerobic digestion; Vlyssides AG et al.; This work studied the hydrolysis kinetics and the solubilization of waste activated sludge under a medium range temperature (50-90 degrees C) and pH in the alkaline region (8-11), as a pretreatment stage for anaerobic digestion . The hydrolysis rate for the solubilization of volatile suspended solids (VSS) followed a first-order rate . A linear polynomial hydrolysis model was derived from the experimental results leading to a satisfactory correlation between the hydrolysis rate coefficient, pH, and temperature . At pH 11 and a temperature of 90 degrees C the concentration of the VSS was 6.82%, the VSS reduction reached 45% within ten hours and at the same time the soluble COD was 70.000 mg/l and the total efficiency for methane production 0.28 l of CH4 per g of VSS loading. Biosci Biotechnol Biochem, 2003 Oct, 67(10), 2286 - 7 Isolation and characterization of a stilbene-degrading strain of Pseudomonas fluorescens, and production of antioxidant compounds by stilbene metabolism; Leahy JG et al.; In this study, we consider the use of hydrocarbon-degrading bacteria that degrade trans-stilbene as a novel approach for synthesizing potentially bioactive hydroxylated stilbenes . A trans-stilbene-degrading bacterium, MN2, was isolated from activated sludge through enrichment culture, and identified as Pseudomonas fluorescens using conventional techniques . Degradation of trans-stilbene by this strain yielded two metabolites that had significant antioxidant activity. J Hazard Mater, 2003 Oct 31, 103(3), 263 - 77 Effects of adsorbents and copper(II) on activated sludge microorganisms and sequencing batch reactor treatment process; Ong SA et al.; Wastewater treatment systems employing simultaneous adsorption and biodegradation processes have proven to be effective in treating toxic pollutants present in industrial wastewater . The objective of this study is to evaluate the effect of Cu(II) and the efficacy of the powdered activated carbon (PAC) and activated rice husk (ARH) in reducing the toxic effect of Cu(II) on the activated sludge microorganisms . The ARH was prepared by treatment with concentrated nitric acid for 15 h at 60-65 degrees C . The sequencing batch reactor (SBR) systems were operated with FILL, REACT, SETTLE, DRAW and IDLE modes in the ratio of 0.5:3.5:1:0.75:0.25 for a cycle time of 6 h . The Cu(II) and COD removal efficiency were 90 and 85%, respectively, in the SBR system containing 10 mg/l Cu(II) with the addition of 143 mg/l PAC or 1.0 g PAC per cycle . In the case of 715 mg/l ARH or 5.0 g ARH per cycle addition, the Cu(II) and COD removal efficiency were 85 and 92%, respectively . ARH can be used as an alternate adsorbent to PAC in the simultaneous adsorption and biodegradation wastewater treatment process for the removal of Cu(II) . The specific oxygen uptake rate (SOUR) and kinetic studies show that the addition of PAC and ARH reduce the toxic effect of Cu(II) on the activated sludge microorganisms. J Colloid Interface Sci, 2003 Nov 1, 267(1), 136 - 43 Porosity and interior structure of flocculated activated sludge floc; Chung HY et al.; This work estimated the porosities of activated sludge flocs, cationic polyelectrolyte flocculated, based on free-settling tests, buoyant weight measurements, and confocal laser scanning microscope (CLSM) tests . The extent of advective flow was estimated based on bubble-tracking test . The former two measurements suggested a close-to-unity porosity, that is, an extremely void floc interior . Meanwhile, the latter two tests recommended a dense floc interior with a porosity less than 64% . A discrepancy exists between the porosities estimated by various tests . A floc model was proposed based on the understanding that a vast amount of bound water in the floc was regarded as void in buoyant weight measurement, but was impermeable for advective flow . The distribution rather than the mean value of the porosity controls the advective flow . There existed no simple correlation between the porosities measured by different tests. Huan Jing Ke Xue, 2003 Jul, 24(4), 99 - 104 {Studies on aerobic granular sludge cultivated under selective pressure}; Wang Q et al.; As inoculum sludge from a conventional COD removal activated sludge wastewater treatment plant was used, aerobic granular sludge was cultured in sequencing batch reactor (SBR) fed with glucose as carbon substrate . The SBR was operated with decreasing sedimentation time and increasing COD loading rate resulting in the selective pressure to enhance the formation of granular sludge . According to morphology change of sludge, the generation of granule could be divided into three stage . Granules started to appear after 67 days operation . After increasing COD loading rate to 4.8 kg/(m3.d), and superficial gas velocity to 0.0175 m/s, granules were the dominant sludge forms with diameter about 6-9 mm, the minimal settling velocity of 32.7 m/h, and the MLSS of 7800 mg/L . Aerobic granular sludge demonstrates high activity and ability to withstand high COD loading rate . The properties of aerobic granular sludges and the effect of different operational conditions on the formation of these aerobic granules were also analyzed preliminarily. Chemosphere, 2003 Dec, 53(10), 1201 - 10 Occurrence and fate of heavy metals in the wastewater treatment process; Karvelas M et al.; The occurrence and the fate of heavy metals (Cd, Pb, Mn, Cu, Zn, Fe and Ni) during the wastewater treatment process were investigated in the wastewater treatment plant (WTP) of the city of Thessaloniki, northern Greece, operating in the activated sludge mode . For this purpose, wastewater and sludge samples were collected from six different points of the plant, namely, the influent (raw wastewater, RW), the effluent of the primary sedimentation tank (primary sedimentation effluent, PSE), the effluent of the secondary sedimentation tank (secondary sedimentation effluent, SSE), sludge from the primary sedimentation tank (primary sludge, PS), activated sludge from the recirculation stream (activated sludge, AS), and the digested/dewatered sludge (final sludge, FS).The distribution of metals between the aqueous and the solid phase of wastewater was investigated . Good exponential correlation was found between the metal partition coefficient, logK(p), and the suspended solids concentration . The mass balance of heavy metals in the primary, secondary and the whole treatment process showed good closures for all metal species . The relative distribution of individual heavy metals in the treated effluent and the sludge streams indicated that Mn and Cu are primarily (>70%) accumulated in the sludge, while 47-63% of Cd, Cr, Pb, Fe, Ni and Zn remain in the treated effluent. Biotechnol Adv, 1986, 4(1), 13 - 26 Biotechnology for phosphorus removal during wastewater treatment; Yeoman S et al.; Advanced biological wastewater treatment for the removal of phosphorus in excess of the normal metabolic requirements of activated sludge type processes has been developed as an alternative to chemical addition . Current laboratory and pilot plant investigations have confirmed that a preliminary anaerobic zone and plug-flow type configuration are necessary for good enhanced biological phosphorus removal . Nitrate in the anaerobic stage inhibits the process whereas acetate enhances phosphorus uptake . The bacteria probably responsible are of the Acinetobacter genus and the presence of stored polyphosphate within these bacteria has been demonstrated . It has also been shown that pure cultures of Acinetobacter do not necessarily take up soluble substrate as phosphate is released during the anaerobic phase, in contrast to the current proposed mechanism, and that in certain cases natural chemical precipitation could make a significant contribution towards overall phosphorus removal . Several studies of pilot and full-scale plants have been reported. Biotechnol Adv, 1999 Apr, 17(1), 49 - 70 Role of micronutrients in activated sludge-based biotreatment of industrial effluents; Burgess JE et al.; Industrial processes often produce wastewaters that resist biological treatment owing to the unfamiliarity of some components to biological systems . Availability of nutrients determines the community structure of the activated sludge and hence the efficiency of the degradation process . Micronutrients influence the bacteria involved in waste degradation and also the species diversity within the sludge . The requirements for and toxicity of different micronutrients vary according to the nature of the waste and the ecology of the sludge . Adding micronutrients to biological treatment processes is one possible approach to upgrading an existing facility in order to deal with increasing volumes and strengths of industrial wastewaters and the tightening discharge legislation. Biotechnol Adv, 2001 Feb 1, 19(1), 35 - 63 Developments in odour control and waste gas treatment biotechnology: a review; Burgess JE et al.; Waste and wastewater treatment processes produce odours, which can cause a nuisance to adjacent populations and contribute significantly to atmospheric pollution . Sulphurous compounds are responsible for acid rain and mist; many organic compounds of industrial origin contribute to airborne public health concerns, as well as environmental problems . Waste gases from industry have traditionally been treated using physicochemical processes, such as scrubbing, adsorption, condensation, and oxidation, however, biological treatment of waste gases has gained support as an effective and economical option in the past few decades . One emergent technique for biological waste gas treatment is the use of existing activated sludge plants as bioscrubbers, thus treating the foul air generated by other process units of the wastewater treatment system on site, with no requirement for additional units or for interruption of wastewater treatment . Limited data are available regarding the performance of activated sludge diffusion of odorous air in spite of numerous positive reports from full-scale applications in North America . This review argues that the information available is insufficient for precise process design and optimization, and simultaneous activated sludge treatment of wastewater and airborne odours could be adopted worldwide. Biotechnol Adv, 2001 Apr 1, 19(2), 97 - 107 Strategy for minimization of excess sludge production from the activated sludge process; Liu Y et al.; Increased attention has been given to minimization of sludge production from activated sludge process since environmental regulations are being more and more stringent in relation to excess sludge disposal . In a biological process, the more organic carbon utilized in carbon dioxide production, the fewer sludge produced, and vice versa . This paper, therefore, reviews strategies developed for minimization of excess sludge production, such as oxic-settling-anaerobic process, high dissolved oxygen process, uncoupler-containing activated sludge process, ozonation-combined activated sludge process, control of sludge retention time and biodegradation of sludge in membrane-assisted reactor . In these modified activated sludge processes, excess sludge production can be reduced by 20-100% without significant effect on process efficiency and stability . It is expected that this paper would be helpful for researchers and engineers to develop novel and efficient operation strategy to minimize sludge production from biological systems. Appl Environ Microbiol, 2003 Oct, 69(10), 6056 - 63 Coaggregation among nonflocculating bacteria isolated from activated sludge; Malik A et al.; Thirty-two strains of nonflocculating bacteria isolated from sewage-activated sludge were tested by a spectrophotometric assay for their ability to coaggregate with one other in two-membered systems . Among these strains, eight showed significant (74 to 99%) coaggregation with Acinetobacter johnsonii S35 while only four strains coaggregated, to a lesser extent (43 to 65%), with Acinetobacter junii S33 . The extent and pattern of coaggregation as well as the aggregate size showed good correlation with cellular characteristics of the coaggregating partners . These strains were identified by sequencing of full-length 16S rRNA genes . A . johnsonii S35 could coaggregate with strains of several genera, such as Oligotropha carboxidovorans, Microbacterium esteraromaticum, and Xanthomonas spp . The role of Acinetobacter isolates as bridging organisms in multigeneric coaggregates is indicated . This investigation revealed the role of much-neglected nonflocculating bacteria in floc formation in activated sludge. Water Sci Technol, 2003, 48(4), 61 - 8 Anaerobic digestion of waste activated sludge combined with ozone post-treatment and recycling; Battimelli A et al.; The aim of the study was to determine the performances of a combined ozone/anaerobic digestion system for waste activated sludge reduction . The objective was the estimation of the process efficiency and stability when keeping constant influent flow while increasing recycled chemically treated flow . The ozonation step consisted in a partial oxidation (0.16 g O3/g SS) of the anaerobic mesophilic digested sludge . Chemical treatment of digested sludge resulted in a threefold COD solubilization and a decrease of SS of 22% . Some of the advantages of digested sludge ozonation were: deodorization, better settlement and a reduction in viscosity . However there were drawbacks: foaming during ozonation and, at high ozone doses, poorer filterability . The anaerobic digestion was carried out over 6 months with an increasing recycling of ozonated flow . Suspended solids removal rate and COD removal rate were compared with initial operating conditions for the biological reactor and the whole combined process . The optimum recycling rate was 25% with increases of SS removal and COD removal of 54% and 66% respectively when considering the combined process; corresponding to a decrease of the hydraulic retention time from 24 days to 19 days. Syst Appl Microbiol, 2003 Sep, 26(3), 367 - 75 Tsukamurella spumae sp . nov., a novel actinomycete associated with foaming in activated sludge plants; Nam SW et al.; A polyphasic taxonomic study was undertaken to establish the taxonomic position of six representative strains isolated from activated sewage sludge foam . The organisms were found to have chemical and morphological properties consistent with their assignment to the genus Tsukamurella . DNA:DNA relatedness studies showed that five out of the six isolates formed a distinct genomic species, the remaining strain was most closely associated with this taxon . The five isolates had a unique phenotypic profile that served to distinguish them from representatives of the validly described species of Tsukamurella . The combination of the genotypic and phenotypic data indicated that the five strains should be classified as a new species in the genus Tsukamurella . The name proposed for this taxon is Tsukamurella spumae, the type strain is N1171T (= DSM 44.113T = NCIMB 13947T) . It was also shown that some of the reference strains were misclassified as Tsukamurella paurometabola. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2453 - 63 The effects of diquat dibromide on biological wastewater treatment plants; Randall CW et al.; The objective of the study was to investigate the fate and effects of diquat dibromide which is the active ingredient in formulations used to control the growth of roots into sewers when applied as Razorooter and mixed with raw sewage, settled sewage, and activated sludge, and when introduced into activated sludge wastewater treatment systems . Both fully aerobic and biological nutrient removal (BNR) activated sludge systems were used for experimental purpose, and both continuous flow and batch reactors were used . The sorption of diquat by both raw sewage particles and activated sludge suspended solids was determined . Diquat dibromide concentrations ranged from 0.93 to 12.6 mg/L in the influent flow . Both the fully aerobic and two full biological nutrient removal systems were fed municipal sewage spiked with diquat dibromide, and operated at a mixed liquor temperature of 10 degrees C and an MCRT of 10 days . One of the BNR systems was a control system . The results showed that only about 20% of the diquat in raw sewage flow was removed by adsorptions to the sewage solids, but 80% or more of the diquat was removed in activated sludge systems . When the influent diquat dibromide concentration was approximately 1mg/L, over 99% of the diquat dibromide was removed by the activated sludge process . Some of the removal was believed to be by biodegradation . The diquat dibromide used in this study had no observable detrimental effects on any of the biological processes of the continuous flow fully aerobic and BNR activated systems. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2401 - 12 Sludge dewatering and disposal practices for small activated sludge wastewater treatment plants; Hatziconstantinou GJ et al.; Sludge dewatering is a decisive step in the reduction of waste sludge volume, thus considerably affecting total sludge treatment and disposal costs . The construction of sludge dewatering facilities in small WwTPs though, is generally not cost effective . In this paper some experimental evidence is presented, that waste sludge dewatering in small WwTPs of the activated sludge extended aeration type, can be effectively achieved by a centrifuge type of equipment withdrawing sludge directly from the aeration tank; an economic evaluation of the possibility to employ a transportable type of similar equipment mounted on a truck, to serve a number of small WwTPs located in remote or isolated areas is also presented and discussed. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2287 - 300 Performance-based characterization of a contact stabilization process for slaughterhouse wastewater; Al-Mutairi NZ et al.; This paper evaluates the effluent treatment plant of a slaughterhouse in Hawalli City, Kuwait processing 1100 heads of livestock a day . Results indicated that the proposed process effectively reduces pollution potential of slaughterhouse wastewater . Influent Chemical Oxygen Demand (COD) ranged from 3335 to 7580 mg L(-1), of which approximately 30% were in the form of suspended solids (SS) . Removal efficiency was 77% for soluble COD and 82% for insoluble COD, at a volumetric load of 1.8 kg COD m(-3) d(-1) . Values obtained for the biokinetic coefficients, floc uptake (FU), substrate removal efficiency (SRE), specific reaction rate (RR), maximum reaction rate (Rm) and Yield (Y) of the contact tank were higher than the range of values reported for other continuously fed activated sludge systems . In contrast to the contact tank, the aeration basin biokinetic coefficients were within the range of values reported . Contact process testing demonstrated that controlling solid recirculation to maintain a contact loading of about 120-150 mg COD g(-1) VSS in the contact tank generally resulted in high SRE . RR, Rm, and also in good settleability as indicated by SVIs being consistently below 150 mL g(-1) . In the other hand, higher contact loadings of more than 150 mg COD g(-1) VSS . resulted in a significant deterioration in SRE, RR, Rm, and SVIs. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2113 - 23 Biodegradation of 3-chlorophenol in a sequencing batch reactor; Chiavola A et al.; The present paper shows the results obtained through a study on the biodegradation of 3-chlorophenol (3-CP) in a Sequencing Batch Reactor (SBR) . To such a purpose a lab-scale SBR was fed a synthetic wastewater containing 3-CP and nutrients (nitrogen and phosphorus) diluted in tap water . The operating strategy, in terms of both the duration of either the cycle or the react phase, was changed throughout the experimental activity in order to find out the optimal one allowing to ensure constant and high removal efficiency despite the increasing 3-chlorophenol concentration in the feed . Biomass collected from a full-scale continuous flow activated sludge facility treating domestic wastewater was used as seed, after being acclimated to 3-CP by means of several batch tests . The results showed that a periodically operated activated sludge system can be successfully used for the biodegradation of chlorophenol compounds, after the needed members of the microbiological consortium are selected and enriched. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2089 - 99 Textile dyeing wastewater treatment in a sequencing batch reactor system; Vives MT et al.; This study was undertaken to examine the feasibility of treating biologically textile wastewater for organic carbon removal . The study was conducted over a lab scale SBR equipped with an in-house developed data acquisition and control software . From monitored operation of SBR and dissolved oxygen values, together with a simple compressed air ON/OFF control scheme, on-line Oxygen Uptake Rate (OUR) profiles during aerobic reaction periods were obtained . Due to the high variability of wastewater characteristics, periodical analyses of textile wastewater were conducted and thus characterized for pH, conductivity, total and volatile solids, COD, ammonia, and TKN . After an initial period of activated sludge adaptation to textile wastewater, the SBR was operated at step-feed strategy to reduce the effluent biodegradable matter presents in the wastewater by SBR water change ratio modification and feeding strategy. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003, 38(10), 2009 - 18 Image analysis as a monitoring tool for activated sludge properties in lab-scale installations; Jenne R et al.; An important step in the battle against filamentous bulking is the development of a monitoring system for activated sludge properties . Therefore, a fully automatic image analysis method for recognizing and characterizing flocs and filaments in activated sludge images has been developed . This procedure has been subsequently used to monitor activated sludge properties in a lab-scale installation . The results of a 100-days experiment indicate that the image information correlates well with the evolution of standard settling properties, in this case the Sludge Volume Index . It is shown that, at the onset of severe filamentous bulking, there is an increase in total filament length on the one hand, and a significant change in floc shape on the other hand. Water Sci Technol, 2003, 48(3), 143 - 50 The role of pH in the organic material solubilization of domestic sludge in anaerobic digestion; Gomec CY et al.; The effect of pH on anaerobic solubilization of domestic primary sludge and activated sludge was investigated and compared . Anaerobic solubilization was carried out in continuously stirred anaerobic reactors at mesophilic temperature (35 degrees C) and pH was fixed at 6.5 (pH-controlled) . Many researches reported the serious effects of pH on the solubilization of organic materials . Thus, the aim of pH control in the reactors consisting of domestic primary and activated sludges, was the evaluation of retardation in hydrolysis/acidogenesis at low pH values . Since primary and activated sludges have different biodegradation characteristics, results were compared . Results indicated that the destruction of Total Suspended Solids (TSS) and Volatile Suspended Solids (VSS) were better in the pH-controlled reactors . In both sludges, acetic acid was the main Volatile Fatty Acid (VFA) produced . In the pH-controlled reactors, VSS reduction was found to be 72% in about 20 days in the anaerobic digestion of activated sludge whereas for the same interval VSS reduction could only be achieved by 32% in primary sludge at 35 degrees C . When primary sludge was used as substrate, the pH-uncontrolled and the pH-controlled reactors remove VSS with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD) . However, production of VFAs and SCOD was ceased after 5 days in the pH-controlled reactor whereas VFAs and SCOD production continued after 5 days in the pH-uncontrolled reactor, which indicated that hydrolysis and fermentation did not complete and continued longer . On the other hand; in either the pH-uncontrolled or the pH-controlled reactor of activated sludge, VSS was not removed with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD) . It was apparent that solubilization was occurring, however this solubilization was not observed as VFA production . When total methane production and total COD (COD(tot)) removal were estimated using VSS removal in both types of sludges, results indicated that pH control enhanced biogas productions as well as COD(tot) removals. Water Sci Technol, 2003, 48(3), 121 - 6 Microbial quantification in activated sludge: the hits and misses; Hall SJ et al.; Since the implementation of the activated sludge process for treating wastewater, there has been a reliance on chemical and physical parameters to monitor the system . However, in biological nutrient removal (BNR) processes, the microorganisms responsible for some of the transformations should be used to monitor the processes with the overall goal to achieve better treatment performance . The development of in situ identification and rapid quantification techniques for key microorganisms involved in BNR are required to achieve this goal . This study explored the quantification of Nitrospira, a key organism in the oxidation of nitrite to nitrate in BNR . Two molecular genetic microbial quantification techniques were evaluated: real-time polymerase chain reaction (PCR) and fluorescence in situ hybridisation (FISH) followed by digital image analysis . A correlation between the Nitrospira quantitative data and the nitrate production rate, determined in batch tests, was attempted . The disadvantages and advantages of both methods will be discussed. Biotechnol Lett, 2003 Aug, 25(16), 1351 - 6 Extraction of activated sludge bacteria exopolymers by ultrasonication; Matias VR et al.; Ultrasonication for the extraction of activated sludge exopolymers was evaluated by total cell count, exopolymer extraction and transmission electron microscopy (TEM) . A high deflocculation was achieved after 30 s of sonication in PBS (phosphate-buffered saline) . TEM showed that cell lysis was minimal only when sludges were sonicated for 30 s . For sludges sonicated for 30, 90 and 420 s and stained with Ruthenium Red, exopolymers were not extracted on a large scale without considerable cell lysis . Sludges sonicated for 30 s in EDTA gave a larger fraction of damaged cells and also showed copious amounts of attached exopolymers. Water Res, 2003 Nov, 37(18), 4453 - 67 Minimization of excess sludge production for biological wastewater treatment; Wei Y et al.; Excess sludge treatment and disposal currently represents a rising challenge for wastewater treatment plants (WWTPs) due to economic, environmental and regulation factors . There is therefore considerable impetus to explore and develop strategies and technologies for reducing excess sludge production in biological wastewater treatment processes . This paper reviews current strategies for reducing sludge production based on these mechanisms: lysis-cryptic growth, uncoupling metabolism, maintenance metabolism, and predation on bacteria . The strategies for sludge reduction should be evaluated and chosen for practical application using costs analysis and assessment of environmental impact . High costs still limit technologies of sludge ozonation-cryptic growth and membrane bioreactor from spreading application in full-scale WWTPs . Bioacclimation and harmful to environment are major bottlenecks for chemical uncoupler in practical application . Sludge reduction induced by oligochaetes may present a cost-effective way for WWTPs if unstable worm growth is solved . Employing any strategy for reducing sludge production may have an impact on microbial community in biological wastewater treatment processes . This impact may influence the sludge characteristics and the quality of effluent. Water Res, 2003 Nov, 37(18), 4331 - 6 Hybrid reactor for priority pollutant nitrobenzene removal; Majumder PS et al.; The performance of a hybrid reactor, comprising of trickling filter and activated sludge process, in treating nitrobenzene wastewater was investigated . Acetate induced cells of mixed consortia was acclimatized with gradual increase of nitrobenzene concentration up to 90 mg/l in 100 days using sodium acetate as co-substrate and considering COD and nitrobenzene concentration as paramount parameters for assessing the growth of biofilm and acclimation . A removal of 60-95.80% COD and 80-90.23% nitrobenzene was observed during acclimation . During hydraulic retention time (HRT) studies, the optimum HRT was found to be 29.55 h at which a maximum of 95.83% COD and 97.93% nitrobenzene removal was observed . Other studies included optimization of C:N ratio, substrate:co-substrate ratio, effect of shock loading and estimation of volatilization losses . The optimum C:N ratio was found to be 100:20 at which maximum 97.93% removal of nitrobenzene was observed . At optimum HRT (29.55 h) and optimum C:N ratio (100:20) optimum substrate:co-substrate ratio was found to be 1:33 . From the shock load studies it can be concluded that the system can withstand shock load up to two times of usual nitrobenzene concentration . A loss of 9.44% nitrobenzene was observed due to volatilization and mass balance gave an efficiency of 87.49% biological removal of nitrobenzene. Water Res, 2003 Jul, 37(13), 3145 - 54 Environmental fate of Triclosan in the River Aire Basin, UK; Sabaliunas D et al.; The concentrations and removal rate of Triclosan, an antibacterial ingredient in consumer products, were measured at advanced trickling filter (TF) and activated sludge (AS) wastewater treatment plants (WWTPs) in the River Aire basin in the UK in September 2000 . Additionally, the in-stream removal of Triclosan was measured directly in Mag Brook, the stream receiving the treated effluent from the TF plant, using a fluorescent dye tracer to determine the water plug travel times . The in-stream removal of the dissolved and un-ionized (i.e . bioavailable) fraction of the compound was measured using semipermeable membrane devices (SPMDs) deployed at various distances downstream from the WWTP discharge point . The estimated removal rates were used in the GREAT-ER (Geography-Referenced Regional Exposure Assessment Tool for European Rivers) model to predict the site-specific distribution of Triclosan concentrations in the Aire basin as well as to calculate regional concentrations . High WWTP (approximately 95%) and in-stream (0.21-0.33 h-1) removal rates of Triclosan in Mag Brook confirm that this chemical is rapidly eliminated from the aquatic environment. Water Res, 2003 Jul, 37(13), 3087 - 97 Modelling multiple mineral precipitation in anaerobic digester liquor; van Rensburg P et al.; Mineral precipitation problems have been experienced with the conveyance and treatment of anaerobically digested primary and waste activated sludge blends . This paper describes an experimental investigation into mineral precipitation in anaerobic digester liquor (ADL) from the Cape Flats (CF) Wastewater Treatment Plant (WWTP) (Cape Town, South Africa), and application of the three-phase (aqueous/solid/gas) physical and chemical processes kinetic model developed by Musvoto et al . (Water Res . 34 (2000) 1857; Water Res . 34 (2000) 1868; Water SA 26(4) (2000) 417) to the experimental data . From the experimental investigation and theoretical modelling, it is concluded inter alia that: (i) there is a close correlation between experimental measured and theoretically predicted data, (ii) the dominating mineral that precipitates is struvite, with small amounts of amorphous calcium phosphate and negligible newberyite, calcite and magnesite, (iii) the precipitation of struvite is governed by the increase in pH when CO2 is lost from the ADL, (iv) the ADL is initially undersaturated with respect to struvite, but becomes supersaturated at pH > 7.3-7.7, (v) the rate and mass of struvite precipitation are controlled by the rate of pH increase and the initial Mg concentration and (vi) the three-phase kinetic model is able to simulate accurately the time dependent precipitation data for multiple minerals competing for the same species and allows determination of specific precipitation rates for a number of minerals simultaneously in an integrated manner from a single batch test . Some operational strategies to minimise struvite precipitation are proposed. Environ Technol, 2003 Aug, 24(8), 979 - 87 Activated sludge as inoculum for ready biodegradability testing: effect of source; Vazquez-Rodriguez G et al.; Results of ready biodegradability tests (RBT) are barely reproducible owing to a well-known lack of definition in inoculum source and quality . In this study, the degree of variability expected when only activated sludges are used as inoculum source was investigated . For this, the characteristics of activated sludges collected in municipal wastewater treatment plants operating at various massic loading rates (MLR; 0.1, 0.5 and 0.9 kgBOD5 kgVSS(-1) d(-1)) were compared . In order to provide suitable cellular densities for RBT, inocula were obtained after settling of activated sludges and analyzed in terms of active and cultivable cell densities, dehydrogenasic activity, BOD5 and a general profile of hydrolytic enzymes . In our analysis, biomass obtained from the High-MLR treatment plant constituted the inoculum having the highest biodegradation potential both with respect to microbial densities and to enzyme activities . This biomass also yielded the fastest biodegradation kinetics in dodecyl benzene sulfonate RBT . An attempt of biomass homogenization of inocula on the basis of cultivable cell density and dehydrogenasic activity gave negative results with this chemical compound . Since, in practice, restriction of activated sludge sources may be difficult, our results emphasize the importance of further studies aimed at homogenization of inoculum quality and quantity. Environ Technol, 2003 Aug, 24(8), 971 - 8 Effect of pH and ionic environment changes on interparticle interactions affecting activated sludge flocs: a rheological approach; Tixier N et al.; The rheological behaviour of activated sludge was investigated through the determination of sludge suspension equilibrium viscosity (micro(eq)) while varying the pH, sodium chloride and calcium chloride concentrations over a wide range . Micro(eq) was used to investigate the influence of environmental changes on the rheological behaviour of activated sludges, on the basis that it is representative of interparticle interactions affecting sludge flocs . Micro(eq) was shown to increase with increasing pH and to decrease with cation addition . The surface charge presented by sludge flocs was shown to be a factor that greatly affects micro(eq), as demonstrated by the linear correlation with zeta-potential (zeta-potential) . A decrease in electrostatic charge was supposed to decrease repulsive effect between particles that facilitate flow and to promote a compaction of flocs that lower viscosity . Cation addition was shown to generate a viscosity decrease, in the same proportion, independent of the valency of the cation . The decrease in the particles double layer thickness coupled to the decrease in surface charge were supposed to induce a decrease in interparticle interactions which leads to lower viscosity values. Bioprocess Biosyst Eng, 2002 Apr, 25(1), 29 - 33 Epub 2002 Mar 02. Use of a microbial sensor: a new approach to the measurement of inhibitory effects on the microbial activity of activated sludge; Aivasidis A et al.; This paper presents a new method for the measurement of inhibitory effects in wastewater treatment plants on the basis of a continuous measurement of the microbial respiration product (CO(2)) . The microbial sensor developed for this purpose consists of a small conical fluidized bed reactor connected to a cylindrical chamber that comprises part of the sample recirculation system . Activated sludge microbes are immobilized on spherical (diameter=1-2 mm) reticulated sinter glass carriers . Pure oxygen is supplied via the cylindrical chamber in order to sustain a highly dense population of microbial mass . The mean hydraulic retention time in the microbial sensor ranges between 30 and 40 min, while temperature is maintained at 30 degrees C, and pH 6.4 . Carbon dioxide in the off-gas, which reflects the microbial activity, is continuously analyzed by means of an infrared analyzer . Inhibition of microbial activity (toxicity) can be determined as the mean percent reduction in carbon dioxide concentration . Several substances were tested and proved toxic to the microbes . With this microbial sensor, early detection of toxic substances becomes feasible, preventing them from entering an activated sludge unit operation. Bioprocess Biosyst Eng, 2002 Jun, 25(2), 79 - 83 Epub 2002 Apr 25. Use of a microbial sensor: inhibition effect of azo-reactive dyes on activated sludge; Georgiou D et al.; This paper summarizes the methodology utilized for measuring the toxic and inhibitory effects of azo-reactive dyes on the activity of activated sludge . The microbial sensor employed in this study consisted of a small-fluidized bed reactor in which the microbial mass was immobilized on spherical (diameter =1-2 mm) reticulated sinter glass carriers . To sustain a highly dense population of aerobic microbes, pure oxygen was supplied via a cylindrical chamber, which comprised part of the sample re-circulation system . The mean hydraulic retention time in the microbial sensor ranged between 30 and 40 min, while temperature was maintained at 30 degrees C and pH at 6.4 . Inhibition of microbial activity (toxicity) was determined as the mean percent reduction in carbon dioxide production from microorganisms' respiration . Several azo-reactive dyes demonstrated toxicity when applied at a high concentration (2 g/l), however, a portion of the microbes showed tolerance to the dyes . Moreover, textile wastewater demonstrated very efficient biodegradation. Adv Space Res, 2003, 31(7), 1657 - 65 Mathematical modeling relevant to closed artificial ecosystems; DeAngelis DL; The mathematical modeling of ecosystems has contributed much to the understanding of the dynamics of such systems . Ecosystems can include not only the natural variety, but also artificial systems designed and controlled by humans . These can range from agricultural systems and activated sludge plants, down to mesocosms, microcosms, and aquaria, which may have practical or research applications . Some purposes may require the design of systems that are completely closed, as far as material cycling is concerned . In all cases, mathematical modeling can help not only to understand the dynamics of the system, but also to design methods of control to keep the system operating in desired ranges . This paper reviews mathematical modeling relevant to the simulation and control of closed or semi-closed artificial ecosystems designed for biological production and recycling in applications in space . Published by Elsevier Science Ltd on behalf of COSPAR. Bioprocess Biosyst Eng, 2003 Jul, 25(6), 387 - 93 Epub 2003 Apr 29. Monitoring filamentous bulking in activated sludge systems fed by synthetic or municipal wastewater; da Motta M et al.; The stability with respect to filamentous bulking of two activated sludge fully-aerobic systems, one with a completely mixed tank and one with a channel reactor, fed either by a synthetic wastewater or by a primary-settled municipal wastewater, of variable composition and flow rate, has been investigated . The morphological characteristics of the biomass in terms of floc size and roughness and of filamentous bacteria abundance have been monitored by image analysis . Severe bulking was only observed in the well-mixed tank fed at a constant flow rate by synthetic substrate of constant concentration, when the channel reactor fed in a similar manner was fully stable . Variations of biomass characteristics as well as of settling properties were observed on both systems fed with the real wastewater, but these events were related to the characteristics of the wastewater, as similar changes were observed on the full-scale plant fed with the same substrate . In any case, automated image analysis was an efficient way to monitor in detail the fate of the activated sludge at pilot and full scale. Int J Syst Evol Microbiol, 2003 Sep, 53(Pt 5), 1479 - 83 Delftia tsuruhatensis sp . nov., a terephthalate-assimilating bacterium isolated from activated sludge; Shigematsu T et al.; A terephthalate-assimilating bacterium was isolated from activated sludge collected from a domestic wastewater treatment plant in Japan by enrichment with terephthalate as sole carbon source . The isolate, designated strain T7(T), was a Gram-negative, short rod-shaped micro-organism . A phylogenetic study based on 16S rRNA gene sequences indicated that strain T7(T) should be placed in the genus DELFTIA: A DNA-DNA hybridization value of 69 % was determined between strain T7(T) and Delftia acidovorans ATCC 15668(T) . Major cellular fatty acids of strain T7(T) were C(16 : 0), C(16 : 1) and C(18 : 1) . Substantial amounts of cyclopropanoic acid (C(17 : 0)), 3-OH C(10 : 0), C(12 : 0), C(15 : 0) and C(14 : 0) were also detected . The total DNA G+C content of strain T7(T) was 66.2 mol% . Strain T7(T) could utilize the following compounds as carbon sources: acetamide, beta-alanine, citrate, D-fructose, glycerol, isobutyrate, isophthalate, D(-)-mannitol, maleate, malonate, phenylacetate, propionate, protocatechuate, terephthalate, D-tryptophan and L-tryptophan . Comparisons of phenotypic and genotypic characteristics with other known species belonging to the genus Delftia suggest that strain T7(T) represents a novel species, for which the name Delftia tsuruhatensis sp . nov . is proposed; strain T7(T) is the type strain (=IFO 16741(T)=ATCC BAA-554(T)). Chemosphere, 2003 Nov, 53(7), 757 - 64 Anaerobic digestion of polyelectrolyte flocculated waste activated sludge; Chu CP et al.; This work examined how adding one of three polyelectrolyte flocculants (T3052: cationic, T2000: non-ionic, and T1052: anionic) affected the anaerobic digestion of wastewater sludge . Methane production, floc characteristics (morphology and zeta-potential) and process parameters (soluble chemical oxygen demands (SCODs) and reductive potentials) were monitored along the digestion tests . The digestion rates of T2000- and T1052-conditioned sludge resembled that for original sludge . The T3052-flocculated sludge generated methane at a higher rate during the first 6 days of digestion than did the original one . In the following stage, the digestion rate of sludge flocculated with T3052 at dosage exceeding 15 g/kg dried solids declined . For example, at 40 days of digestion the methane production amounts for original, 15 g/kg DS flocculated, and 40 g/kg flocculated sludge were of 136, 105, and 85 g/kg DS, respectively . The role of flocculants could change in different stages of digestion.The dosed polymers had no apparent toxicity to the inoculum used . The changes in SCOD, adenosintriphosphate concentrations, oxidative and reductive potential, and zeta-potentials did not correlate with the noted hindered digestion for T3052-conditioned sludge . Microphotographic observation revealed that the flocs of T3052-conditioned sludge were not only of a large size, but also were resistant to structural deterioration during digestion . Therefore, mass transfer resistance was proposed to account for the hindered digestion efficiency observed for T3052-conditioned sludge. J Environ Sci (China), 2003 Jul, 15(4), 510 - 3 Application of organic polymeric flocculants in centrifugal dewatering of oil refinery sludge; Jin YZ et al.; In order to evaluate the applicability of the organic polymeric flocculants (OPF) in the treatment of oil refinery sludge, experiments were conducted to show that OPF have better performance of flocculation than inorganic flocculants . Both the anionic and cationic OPF have satisfactory flocculation efficiency in oil sludge treatment, but the latter are more cost-efficient . Among the over 20 types of flocculants tested, 2 OPF (CPAM-2 and HPAM-2) were selected as the treatment agents, based on their good treatment performances, oil-resistance and economic feasibility . It was demonstrated in the industrial-scale centrifugal dewatering experiments that the application of either CPAM-2 or HPAM-2 could achieve high treatment efficiency of the oil sludge dewatering and reduce the COD of centrifugal liquid to less than 1000 mg/L. J Appl Microbiol, 2003, 95(4), 781 - 6 Reduction in excess sludge production by addition of chemical uncouplers in activated sludge batch cultures; Ye FX et al.; AIMS: To investigate the possibility of reducing excess sludge production in activated sludge processes by the addition of chemical uncouplers to greatly dissociate anabolism from catabolism . METHODS AND RESULTS: Ortho-chlorophenol (oCP), 2,4-dichlorophenol (DCP), 3,3',4',5-tetrachlorosalicylanilide (TCS), para-dinitrophenol (pNP) and 2,4-dinitrophenol (DNP) were chosen for short-term tests for their ability to reduce sludge yield by shaking bottle test . The most effective chemicals, DNP and pNP, together with TCS were tested for various uncoupler concentrations and biomass concentrations . TCS was tested in a lab-scale completely mixed activated sludge batch culture . The model (demonstrated by Liu) was verified with experimental data in completely mixed activated sludge batch test, but was inconsistent with the results from the shaking bottle batch test . The observed growth yield (Yobs) decreased with increasing of the ratio of initial uncoupler concentration to initial biomass concentration (Cu/X0) . CONCLUSIONS: We suggest that the uncouplers oCP, DCP, TCS, pNP and DNP can cause a significant decrease in sludge production, the metabolism of which can explain the decline in sludge yield . SIGNIFICANCE AND IMPACT OF THE STUDY: The real strength of chemical uncoupler imposing on biomass should be Cu/X0, not initial uncoupler concentration (Cu) alone . Chemical uncouplers can be used to develop the activated sludge processes for minimizing excess sludge production. Environ Sci Technol, 2003 Aug 1, 37(15), 3243 - 9 Environmental exposure assessment of fluoroquinolone antibacterial agents from sewage to soil; Golet EM et al.; The behavior of fluoroquinolone antibacterial agents (FQs) during mechanical-biological wastewater treatment was studied by mass flow analysis . In addition, the fate of FQs in agricultural soils after sludge application was investigated . Concentrations of FQs in filtered wastewater (raw sewage, primary, secondary, and tertiary effluents) were determined using solid-phase extraction with mixed phase cation exchange disk cartridges and reversed-phase liquid chromatography with fluorescence detection . FQs in suspended solids, sewage sludge (raw, excess, and anaerobically digested sludge), and sludge-treated soils were determined as described for the aqueous samples but preceded by accelerated solvent extraction . Wastewater treatment resulted in a reduction of the FQ mass flow of 88-92%, mainly due to sorption on sewage sludge . A sludge-wastewater partition coefficient (log Kd approximately 4) was calculated in the activated sludge reactors with a hydraulic residence time of about 8 h . No significant removal of FQs occurred under methanogenic conditions of the sludge digesters . These results suggest sewage sludge as the main reservoir of FQ residues and outline the importance of sludge management strategies to determine whether most of the human-excreted FQs enter the environment . Field experiments of sludge-application to agricultural land confirmed the long-term persistence of trace amounts of FQs in sludge-treated soils and indicated a limited mobility of FQs into the subsoil. Biomacromolecules, 2003 Sep-Oct, 4(5), 1250 - 4 Michael reaction of chitosan with various acryl reagents in water; Sashiwa H et al.; A Michael reaction of chitosan was conducted in water containing acetic acid with various acryl reagents . The degree of substitution could be controlled by temperature, reaction time, and the amount of acryl reagents . Although the modified chitosan derivatives with acrylic acid esters showed water-solubility, that with poly(ethylene glycol) acrylate, however, turned to water-insoluble material by lyophilization . Good biodegradation was observed in modified chitosan derivatives by standard activated sludge. Biomacromolecules, 2003 Sep-Oct, 4(5), 1244 - 9 Synthesis of a chitosan-dendrimer hybrid and its biodegradation; Sashiwa H et al.; Chitosan-dendrimer hybrids having various functional groups such as carboxyl, ester, and poly(ethylene glycol) groups were prepared successfully using dendrimer acetal by reductive N-alkylation . The synthetic procedure could be accomplished by one-step reaction without organic solvent . The degree of substitution of dendrimer was 0.13-0.18 evaluated by (1)H NMR . A perfectly or partially water-soluble chitosan-dendrimer hybrid could be obtained . By standard activated sludge, good biodegradation was observed in these hybrids. Water Res, 2003 Oct, 37(17), 4081 - 90 Purification of cork processing wastewaters by ozone, by activated sludge, and by their two sequential applications; Benitez FJ et al.; Wastewaters generated in the cork processing industry were treated in continuous reactors by means of single treatments separately-a chemical ozonation and an activated sludge system-and then by both sequential processes-ozonation followed by aerobic degradation, and aerobic degradation followed by ozonation . The removals obtained in the ozonation alone were 12-54%, 65-81%, and 55-89% for the COD, total phenolics, and absorbance at 254 nm, respectively, while the consumed ozone yield ranged from 40% to 61%, and the biodegradability (BOD(5)/COD) varied from an initial 0.60 to final values between 0.68 and 0.93 . The optimum hydraulic retention time and ozone partial pressure were 3 h and 3 kPa, respectively . The stoichiometric ratio was 0.56 g of organic substrate degraded per g of ozone consumed, while the rate constants obtained for the ozone disappearance and for the organic matter degradation were 4490 L g COD(-1) h(-1) and 1970 L g O(3)(-1)h(-1) respectively . The presence of hydrogen peroxide or UV radiation in addition to ozone increased the values of organic matter removal as well as the stoichiometric ratio and the rate constants . The aerobic treatment by the activated sludge system yielded COD removals between 13% and 37% for hydraulic retention times between 24 and 96 h, and the Contois model gave values of q(max)=0.14 g COD g VSS(-1)h(-1) and K(1)=22.6 g COD g VSS(-1) for the main kinetic parameters . The sequential processes increased the substrate removal efficiencies in comparison with the individual processes . These enhancements were greater in the aerobic degradation-ozonation sequence than in the ozonation-aerobic degradation sequence. J Air Waste Manag Assoc, 2003 Aug, 53(8), 976 - 82 Case studies on biological treatment of tannery effluents in India; Tare V et al.; This paper presents a comparative assessment of the cost and quality of treatment of tannery wastewater in India by two common effluent treatment plants (CETPs) constructed for two tannery clusters, at Jajmau (Kanpur) and at Unnao in the state of Uttar Pradesh, India . The Jajmau plant is upflow anaerobic sludge blanket (UASB) process-based, while the Unnao plant is activated sludge process (ASP)-based . Investigations indicated that the ASP-based plant was superior in all respects . Total annualized costs, including capital and operation and maintenance costs, for the UASB and ASP plants were Rs . 4.24 million/million liters per day (MLD) and Rs . 3.36 million/MLD, respectively . Land requirements for the two CETPs were 1.4 hectares/MLD and 0.95 hectares/ MLD, respectively . Moreover, the treated UASB effluent had higher biochemical and chemical oxygen demand (BOD/ COD) and considerable amounts of other undesirable constituents, like chromium (Cr) and sulfide, as compared with the ASP effluent, which had lower BOD/COD and negligible concentration of sulfide and Cr . Sludge production from the UASB-based plant was also higher at 1.4 t/day/MLD, in comparison to the sludge production of 0.8 t/day/MLD for the ASP-based plant . Also, the entire sludge produced in the UASB-based plant was Cr-contaminated and, hence, hazardous, while only a small fraction of the sludge produced in the ASP-based plant was similarly contaminated . The results of this study are at variance with the conventional wisdom of the superiority of anaerobic processes for tannery wastewater treatment in tropical developing countries like India. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003 Sep, 38(9), 1825 - 35 Assessment of the biodegradability of dialkyldimethylammonium salts in flow through systems; van Ginkel CG et al.; A bacterium capable of utilizing the alkyl chains of didecyldimethylammonium salt was isolated from activated sludge . In addition, the isolate also utilized didodecyldimethylammonium salt, ditetradecyldimethylammonium salt and alkyltrimethylammonium salts (C10 to C18) as sole source of carbon and energy . The broad substrate with respect to the alkyl chain length was also demonstrated with oxidation rates of various quaternary ammonium salts by didecyldimethylammonium chloride-grown cells . The oxidation rate decreased with increasing alkyl chain lengths . The main factor impeding the biodegradation of dialkyldimethylammonium salts with long alkyl chains is probably the low bioavailability of water-insoluble chemicals . The biodegradability of dialkyldimethylammonium salts was therefore determined in flow-through columns at concentrations below their aqueous solubility . Dialkyldimethylammonium salts adsorbed on silica gel particles packed in flow-through columns were immediately metabolized by the isolate when dissolved . Microorganisms present in river water pumped through a sterile column degraded dissolved dicocodimethylammonium salts within a week. J Environ Sci (China), 2003 May, 15(3), 328 - 33 Uptake of copper ion by activated sludge and its bacterial community variation analyzed by 16S rDNA; Xie B et al.; The effect and uptake of copper ion on SBR (sequence batch reactor) biological treatment system was studied . Special nutrient and powder activated carbon (PAC) additive were tested as uptake stimulation technique . Results showed that copper ion had higher effect on unacclimated activated sludge system than on acclimated one . The special nutrient adding could enhance the uptake of copper significantly, while PAC adding could improve the sludge settling and decrease the turbidity of effluent . The variation of bacterial community analyzed by 16S rDNA method showed the acclimation of copper could increase copper resistance species, and excess accumulation could cause some species diminish . It was confirmed that acclimation could improve the resistance and uptake ability of microorganism to heavy metal. J Environ Sci (China), 2003 May, 15(3), 323 - 7 Colour and organic removal of biologically treated coffee curing wastewater by electrochemical oxidation method; Bejankiwar RS et al.; The treatment of biologically treated wastewater of coffee-curing industry by the electrochemical oxidation using steel anode was investigated . Bench-scale experiments were conducted for activated sludge process on raw wastewater and the treated effluents were further treated by electrochemical oxidation method for its colour and organic content removal . The efficiency of the process was determined in terms of removal percentage of COD, BOD and colour during the course of reaction . Several operating parameters like time, pH and current density were examined to ascertain their effects on the treatment efficiency . Steel anode was found to be effective for the COD and colour removal with anode efficiency of 0.118 kgCOD x h(-1) x A(-1) x m(-2) and energy consumption 20.61 kWh x kg(-1) of COD at pH 9 . The decrease in pH from 9 to 3 found to increase the anode efficiency from 0.118 kgCOD x h(-1) x A(-1) x m(-2) to 0.144 kWh x kg(-1) of COD while decrease the energy consumption from 20.61 kWh x kg(-1) of COD to 12.86 kWh x kg(-1) of COD . The pH of 5 was considered an ideal from the present treatment process as it avoids the addition of chemicals for neutralization of treated effluents and also economical with respect to energy consumption . An empirical relation developed for relationship between applied current density and COD removal efficiency showed strong predictive capability with coefficient of determination of 96.5%. J Environ Sci (China), 2003 May, 15(3), 296 - 301 Biodegradability of terephthalic acid in terylene artificial silk printing and dyeing wastewater; Guan BH et al.; As the characteristic pollutant, terephthalic acid (TA) was in charge of 40%-78% of the total COD of terylene artificial silk printing and dyeing wastewater (TPW-water) . The studies on biodegradability of TA were conducted in a serial of activated sludge reactors with TPW-water . TA appeared to be readily biodegradable with removal efficiency over 96.5% under aerobic conditions, hardly biodegradable with removal efficiency below 10% under anoxic conditions and slowly biodegradable with a turnover between 31.4% and 56.0% under anaerobic conditions . TA also accounted for the majority of BOD in TPW-water . The process combined by anoxic, anaerobic and aerobic activated sludge reactor was suitable for TA degradation and TPW-water treatment, Further, the aerobic process was essentially much more effective than the anaerobic or anoxic one to degrade TA in TPW-water. Water Environ Res, 2003 Jul-Aug, 75(4), 342 - 54 A laboratory batch reactor test for assessing nonspeciated volatile organic compound biodegradation in activated sludge; Cano ML et al.; The relative rates of biodegradation and stripping and volatilization of nonspeciated volatile organic compounds (VOCs) in wastewater treated with aerobic activated-sludge processes can be quantified using a newly developed procedure . This method was adapted from the original aerated draft tube reactor test that was developed to measure biodegradation rate constants for specific volatile pollutants of interest . The original batch test has been modified to include solid-phase microextraction (SPME) fibers for sampling in the gas phase . The experimental procedure using SPME fibers does not require specific identification and quantitation of individual pollutants and can be used to evaluate wastewater with multiple VOCs . To illustrate use of this procedure, laboratory experiments were conducted using biomass and wastewater or effluent from three activated-sludge treatment systems . Each experiment consisted of two trials: a stripping-only trial without biomass and a stripping plus biodegradation trial using biomass from the activated-sludge unit of interest . Data from the two trials were used to quantify the rates of biodegradation by difference . The activated-sludge systems tested were a laboratory diffused-air reactor treating refinery wastewater, a full-scale surface aerated reactor treating a petrochemical wastewater, and a full-scale diffused-air reactor treating a variety of industrial effluents . The biodegradation rate constant data from each laboratory batch experiment were used in model calculations to quantify the fraction emitted (fe) and the fraction biodegraded (fbio) for each system . The fe values ranged from a maximum of 0.01 to a maximum of 0.32, whereas fbio values ranged from a minimum of 0.40 to a minimum 0.95 . Two of these systems had been previously tested using a more complicated experimental approach, and the current results were in good agreement with previous results . These results indicate that biodegradation rate constant data from this laboratory method can be successfully used to predict the fate of VOCs in field-scale treatment units, and thus could potentially be used for demonstration of compliance with wastewater VOC emission regulations. Water Environ Res, 2003 Jul-Aug, 75(4), 300 - 7 Effect of powdered activated carbon on the performance of an aerobic membrane bioreactor: comparison between cross-flow and submerged membrane systems; Kim JS et al.; The effects of powdered activated carbon (PAC) on the performance of an aerobic membrane bioreactor were investigated under two different filtration modes: cross-flow and submerged filtration . Under a cross-flow microfiltration mode, floc breakage resulting from sludge recirculation caused a rapid decrease in the microbial floc size and the release of colloidal and soluble components including extracellular polymeric substances (EPS) . The released components caused rapid loss of membrane permeability by the formation of a dense cake layer on the surface of the membrane . Biological activated carbon (BAC) sludge formed by the addition of PAC released lower amounts of fine colloids and EPS . Although the pattern of floc breakage of the BAC sludge by pumping shear was similar to that of conventional activated sludge, PAC in the BAC microbial floc adsorbed or entrapped some microfloc components into the floc and reduced permeability loss by approximately 35% compared with conventional activated sludge . Under a submerged microfiltration mode, the effect of PAC addition was more pronounced . For the BAC sludge, the increase in transmembrane pressure was more sluggish and, thus, the operating interval could be extended up to 3 times that for the submerged membrane bioreactor with normal activated sludge. Water Environ Res, 2003 Jul-Aug, 75(4), 292 - 9 Detection of Cryptosporidium parvum in secondary effluents using a most probable number-polymerase chain reaction assay; Tsuchihashi R et al.; Polymerase chain reaction (PCR) was used to detect Cryptosporidium parvum oocysts in secondary effluent samples collected from activated-sludge facilities . Serial dilutions of the purified nucleic acid extracts from the samples were made and PCR was conducted to estimate the C . parvum oocyst concentration via a Poisson distribution-based most probable number (MPN) . The degree of oocysts associated with wastewater particles was also evaluated . The sensitivity of the MPN-PCR assay was 20 oocysts/PCR unit . The detection limit of the concentration, extraction, and purification protocols in phosphate buffer saline spiked with a known concentration of oocysts ranged from 1.1 to 4.6 oocysts/L; the detection limit for the wastewater samples ranged from 11 to 4200 oocysts/L depending on the extent of inhibition in each sample . The recovery efficiency of the oocysts ranged from 48 to 59% in most samples . Oocysts were found in two out of seven samples with concentrations of 203 and 308 oocysts/L, as estimated by the MPN-PCR method . The oocysts were found only in the filtrate of the grab samples; particle-associated oocysts were not detected . Association of spiked C . parvum oocysts with particles in secondary effluent drawn from wastewater plants with varying operating conditions indicated a weak correlation between the degree of association and the mean cell residence time of the system. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003 Aug, 38(8), 1549 - 56 Use of sewage sludge compost as the restoration agent on the degraded soil of Tatarstan; Selivanovskaya SY et al.; One of the characteristics of soils in Tatarstan is their low organic matter content . The decrease in soil organic matter is paralleled by declines in soil fertility . One method to reverse this degradation in soil quality is the addition of organic matter . The use of sewage sludge on soils intended for growing of plant seedlings provides an alternative for sewage sludge disposal . Therefore, the evaluation of the feasibility of using compost from the municipal sewage sludge produced in Kazan for the soil restoration and growth of Pinus silvestris seedlings was carried out . The grey forest soil (Haplic Greyzem) was amended with compost at application rate 30, 60 and 90 Mg ha(-1) on a dry matter basis . Organic matter content increased with the increase in sludge amendment . The concentrations of individual heavy metal were below the current limits established for Russia and European countries . Sludge amendments enhanced the germination and the number of the seedlings and the increase were more obvious for the soil with highest sludge treatment . The application of composted sludge to soil was followed by the increase in microbial biomass and basal respiration. J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003 Aug, 38(8), 1529 - 48 Treatability of 2,4 dinitrotoluene in anaerobic/aerobic sequential processes; Sponza DT et al.; Lab-scale anaerobic upflow anaerobic sludge blanket (UASB) completely stirred tank (CSTR) activated sludge reactor system was used to investigate the treatability of 2,4 dinitrotoluene (DNT) using molasses as primary substrate in continuous fed mode . The treatment efficiencies in anaerobic and aerobic reactors were determined by monitoring the chemical oxygen demand (COD), DNT removals, total and methane gas productions . The effect of increasing DNT concentrations on bicarbonate alkalinity, volatile fatty acid accumulation and methane gas percentage were investigated in UASB reactor . Based on the anaerobic toxicity (ATA) test results, although 12 mg L(-1) of DNT is toxic to unacclimatized partially granulated sludge; over 85 and 90% COD and DNT removal efficiencies were obtained at loadings rates of 250 mg DNT L(-1) day(-1) in anaerobic reactor at a HRT of 0.5 day . Total volatile fatty acid (TVFA) accumulation is associated with methane productions as low as 40% of total gas, at loading rate as high as 500 and 1000 mg DNT L(-1) day(-1) through anaerobic DNT biodegradation . The treatment efficiencies in the aerobic reactor were determined by monitoring the COD and DNT removals . The intermetabolite products released through anaerobic and aerobic phases were detected . The TVFA, total aromatic amines, ammonia, total nitrogen and toluene concentrations were monitored . The aerobic step was used for the ultimate mineralization of the remaining COD, DNT, toluene and aromatic amines from the anaerobic treatment . The specific methanogenic activity (SMA) of DNT degrading granules were 2.2 and 0.43g CH4-COD g(-1) VSS day(-1) at DNT loading rates of 12 and 500 mg L(-1) day(-1), respectively . The anaerobic breakdown products of DNT were effectively oxidized in the CSTR reactor since the COD and DNT were ultimately mineralized under aerobic conditions . It can be suggested that DNT, the breakdown products and the COD were ultimately mineralized in combined UASB/CSTR reactor . More than 95% COD and DNT removal efficiencies were obtained in combined UASB,CSTR system at an initial DNT concentration of 125 mg/L(-1) and a loading rate of 250 mg DNT L(-1) day(-1). J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003 Aug, 38(8), 1499 - 515 Conventional morphological and functional evaluation of the microbial populations in a sequencing batch reactor performing EBPR; Dulekgurgen E et al.; To help confirm and interpret the Enhanced Biological Phosphorus Removal (EBPR) performance of the microbial populations in a laboratory-scale activated sludge (AS) system, conventional microscopic examinations were carried out . A lab-scale sequencing batch reactor (SBR), named ARC, was fed with acetate, as the sole carbon source, and operated for EBPR . Daily monitoring and cyclic behavior evaluation studies indicated that the system always worked for EBPR in the long run, with efficiencies depending on the influent characteristics and operational stability . Poly-P and PHB-staining experiments revealed that the enriched biomass of the reactor was quite diverse in terms of morphology, hosting populations of traditional rod-shaped PAOs, tetrad/sarcina-like cells (referred here as TFOs, rather than GAOs), diplococci-shaped cells, and staphylococci-like clustered populations, in addition to few filaments . Although the microscopic observations were qualitative, rather than quantitative, they seemed likely to correlate well to the biochemical performance of the reactor. J Hazard Mater, 2003 Jul 18, 101(2), 203 - 18 Kinetics of the ozonation and aerobic biodegradation of wine vinasses in discontinuous and continuous processes; Benitez JF et al.; The oxidation of the organic substrate present in wastewaters generated in wine distilleries ("wine vinasses") is studied by both an ozonation process and by an aerobic activated sludge system . The ozonation process is conducted in a subsequent first discontinuous and a second continuous periods . Values are reported of the organic matter removal, measured as chemical oxygen demand (COD) (5-25.2%) and as total aromatic compounds content (16.8-51.4%) . The influences of the inlet ozone partial pressure, the hydraulic retention time in the reactor and the presence of UV radiation and H2O2 in addition to ozone are established . Approximate kinetic studies are conducted for both periods which lead to the evaluation of the apparent rate constants for the substrate decomposition 216l/(mol O3 h) and 232l/(g COD h), respectively . In the aerobic degradation by the activated sludge system, the evolution of the organic substrate and biomass are followed during both the discontinuous and continuous stages of the whole process, and COD removals from 31 to 85% are obtained for a hydraulic retention time between 24 and 72 h . For the first stage, a kinetic study is performed by using the Contois model, which applied to the experimental data provides the specific kinetic parameters: q(max)=0.190 g COD/(g volatile suspended solids (VSS)h) and K(1)=6.48g COD/g VSS . For the continuous period, the kinetic study carried out provides the specific rate constant for the substrate decomposition, q=0.027 g COD/(g VSS h). J Hazard Mater, 2003 Jul 18, 101(2), 147 - 55 An OUR-based approach to determine the toxic effects of 2,4-dichlorophenoxyacetic acid in activated sludge; Meric S et al.; This study uses the oxygen uptake rate (OUR) measurement to measure toxicity effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on activated sludges fed with the wastewater from a small domestic wastewater treatment plant and peptone-based synthetic wastewater . Two 2l lab-scale batch reactors were run in parallel with the same F/M ratios (0.4 mg COD per mg VSS per day) to assess the inhibition effects of 2,4-D concentrations between 25 and 75 mg l(-1) considering at least a 100% dilution rate, as compared with a pesticide industry effluent containing 20,000-40,000 mg l(-1) COD, reaches a central treatment plant . It was noted that the OUR was decreased to 15 and 30%, respectively, when adding 75 mg l(-1) of 2,4-D to the domestic and synthetic reactors . Meanwhile, the addition of 25 plus 50 mg l(-1) of 2,4-D in sequence to the domestic wastewater reactor did not significantly affect the OUR profile . The OUR-based inhibition definition has been used in this research since the OUR methods have been frequently used and cited in the literature to study toxicity effects . However, the origin of the sludge used in the testing is also important . Synthetic wastewater may simulate the toxicity studies but with a higher response than actual systems, since the microorganisms are considerably becoming substrate-selective. Water Sci Technol, 2003, 47(12), 285 - 92 Treatment of slaughterhouse wastewater using an activated sludge/contact aeration process; Chen CK et al.; This study combines a two-phase biological treatment system of activated sludge/contact aeration process by adding biological contact filters into the rear sector of the activated sludge aeration tank of the slaughterhouse wastewater treatment plant . This system keeps the advantages of complete mixing of substrates and microorganisms and flexible operation of the activated sludge process, and increased biological phase, less sludge, process stability and good settleability of sludge of the contact aeration process . This system could avoid the defects of sludge bulking, increased sludge production and difficult operation of the activated sludge process, and system clogging and rigid operation of the contact aeration process . Because suspended microorganisms are flowing into the contact aeration system, which then degrade or suspend within the biological contact filters after being adsorbed by the fixed biological film, on which partial bio-solids will act as seeding microorganisms . Suspended microorganisms and the dropped biological film will settled in the secondary settling tank, then reflux into the activated sludge aeration tank . The partial dropped biological film will decompose in the activated sludge aeration tank to achieve the function of decreasing sludge . Large specific gravity and good settling ability of biofilm sludge will provide better effluent quality . It has been proven through a practical experiment at a slaughterhouse wastewater treatment plant in Taiwan, that the activated sludge process effluent COD value of 150-200 mg/L and SS value of 80-100 mg/L were decreased to around 40 mg/L and 22 mg/L, respectively, after changing its system to the two-phase biological treatment system of activated sludge/contact aeration process. Water Sci Technol, 2003, 47(12), 261 - 7 High-performance closed loop anaerobic digestion using pre/post sludge ozonation; Goel R et al.; To maximize the sludge degradation efficiencies during anaerobic digestion, pre-ozonation of raw activated sludge and/or post-ozonation of anaerobically digested sludge were used in combination with a reactor operated without solid withdrawal (closed loop operation scheme) . Out of the two studied configurations, the configuration with the post-ozonation of digested sludge was found to be superior with respect to degradation efficiencies, lower accumulation of total volatile solid (TVS) and lower required ozone dose . The TVS concentration in the reactor with post ozonation was found to be around 26 +/- 2 g/l at an average TVS loading of 0.6 kgTVS/m3 x d . The maximum TVS removal efficiencies were observed to be around 85% with average specific gas recoveries of 0.36 l CH4/gTVS fed . The ozone dose of 3% on the recycle sludge was found to be sufficient as it was observed that the higher ozone doses of 6% neither improved the TVS reduction efficiency nor reduced the TVS concentration in the reactor . The ozone requirements were estimated at around 0.054 gO3/gTVS removed or 0.045 gO3/gTVS fed . The soluble COD concentrations from the reactor ranged from 500-875 mg/l with negligibly small amount of VFA . The average COD in the centrate of the digested sludge was around 3000 mg/l suggesting the presence of colloidal COD in the reactors. Water Sci Technol, 2003, 47(12), 255 - 60 Effect of floc size and structure on biosolids capillary suction time; Guan J et al.; Both size and structure of wastewater solids (biosolids) have been hypothesised to have an impact on the dewaterability of these solids yet very little data exists to validate this hypothesis or to elucidate the relative effects of size and structure . We have recently undertaken studies in which the size and structure of activated sludge flocs were altered in a controlled manner and the dewaterability of resultant flocs examined using the well established capillary suction time (CST) test . A small angle light scattering method was applied for the determination of activated sludge floc size and structure . The results obtained in this work show that floc structure is a major determinant of capillary suction time . In some instances, flocs have almost double the median (D(4,3)) size but possess similar fractal dimensions and similar CST values. Water Sci Technol, 2003, 47(12), 207 - 14 Anaerobic digestion of excess activated sludge with ozone pretreatment; Goel R et al.; Source minimization of excess sludge production by economical means can be considered an attractive option to deal with the problem of sludge disposal under strict disposal standards . In this paper long-term operational results for a process that combines the oxidative ozone pretreatment with anaerobic sludge digestion are described . The ozone pretreatment solubilized around 19% and 37% of the solids at 0.015 and 0.05 gO3/gTS ozone dose . The solubilization ratios during ozonation did not show any significant difference for the sludge concentrations ranging from 1.8-2.6% . The TVS concentrations after ozone treatment were observed to be about 3% lower than the feed sludge concentrations suggesting only partial mineralization during ozonation . The ozone pretreatment resulted in improved solid reduction efficiencies during anaerobic digestion leading to higher methane recovery . The TVS removal efficiencies during anaerobic digestion were observed to increase by a maximum of 35-90% depending on the applied ozone dose during ozone pretreatment . The improvement in TVS degradation efficiency at different applied ozone doses correlated well with the extent of solubilization during ozonation . Long-term data also suggested that biomass acclimation to ozonated sludge was necessary before higher degradation efficiencies could be achieved. Water Sci Technol, 2003, 47(12), 177 - 81 Modification of ASM No.1 for a submerged membrane bioreactor system: including the effects of soluble microbial products on membrane fouling; Cho J et al.; In this study, a mathematical model for the submerged membrane bioreactor (SMBR) was developed by combining the activated sludge model (ASM) with a membrane resistance-in-series model . Some modifications were introduced to make ASM to be suitable for describing the characteristics of SMBR . A set of the 1st-order differential equations was established for 13 dependent variables relevant to particles and soluble matters . Performing model simulations for various conditions, the time when a membrane would be fouled could be predicted as well as the effluent quality . From simulation results, F/M ratio and SRT can be considered as major factors of the soluble microbial products (SMP) concentration in a reactor and it is clear that SMP can play an important role in membrane fouling and water quality simultaneously . The model would be very helpful in optimizing operation conditions as well as in designing an optimal SMBR system. Water Sci Technol, 2003, 47(12), 125 - 32 Benchmarks for the energy demand of nutrient removal plants; Nowak O; The energy demand of municipal wastewater treatment plants for nutrient removal equipped with primary clarifiers, activated sludge system, anaerobic sludge digestion, and CHP is evaluated theoretically, on the basis of COD balances . Operational experience from energy-efficient Austrian treatment plants confirms that the demand on external electrical energy can be kept as low as 5 to 10 kWh/(pe.a) depending on the N:COD ratio in the raw wastewater . A low N:COD ratio helps to keep not only the effluent nitrogen load low, but also the energy demand . Measures to minimise the energy demand at treatment plants and to reduce the nitrogen load are discussed. Water Sci Technol, 2003, 47(12), 95 - 103 Relationship between flocculation of activated sludge and composition of extracellular polymeric substances; Wilen BM et al.; Activated sludge flocs are a flocculated mass of microorganisms, extracellular polymeric substances (EPS) and adsorbed organic and inorganic material . The structure of the floc is very heterogeneous and flocs with very different properties and morphologies may occur, depending on the conditions in the activated sludge treatment plant and wastewater composition . Present thinking suggest that cations, such as calcium, create cationic bridges with EPS excreted by the bacteria and thereby hold the various floc constituents together . However, due to the complex and heterogeneous nature of activated sludge, the mechanisms have neither been thoroughly investigated nor successfully quantified . A better understanding and description of the biological flocculation process is necessary in order to establish more efficient operational strategies . The main aim of this study was to get a comprehensive and unique insight into the floc properties of activated sludge and to assess the relative impact of chemical and physical parameters . A variety of sludges from full scale treatment plants with different settling properties were characterised . The interrelationships between floc parameters such as composition of EPS, surface properties and floc structure, and their effect on the flocculation and separation properties were assessed . The results indicate that the EPS, both in terms of quantity and quality, are very important for the floc properties of the activated sludge . However, presence of filaments may alter the physical properties of the flocs considerably . The EPS showed positive correlations to sludge volume index (SVI) if only sludges with low or moderate numbers of filaments were included . The surface properties were more affected by the composition of the EPS than by the number of filaments . The EPS showed positive correlation to negative surface charge and a negative correlation to relative hydrophobicity and flocculation ability . The negative correlation between flocculation ability and amount of EPS was surprising . The shear sensitivity, measured as degree of erosion of flocs when subjected to shear, was more affected by floc size and number of filaments than amount of EPS. Water Sci Technol, 2003, 47(12), 73 - 80 Performance and microbial dynamics in the coarse pore filtration activated sludge process at different SRTs (solids retention times); Alavi Moghaddam MR et al.; In this research, three SRTs (about 10, 30 and 75 days (without wasting the sludge except for sampling)) were applied to three reactors equipped with non-woven and coarse pore filter modules . The flux was adjusted to about 1 m/d during operation . The main objective of the study was to compare the performance and microbial population dynamics under different SRTs in this process . The results of reactors with SRTs of about 10 and 30 days have shown very good effluent quality without any clogging problem for more than 4 months of operation . For the reactor with long SRT (75 days), the filter clogging was observed after about 80 days of operation and caused an increase in the operation pressure and deterioration effluent quality on some days . Excessive abundance of filamentous bacteria was observed in the reactor with SRT of about 10 days, which had the best effluent quality . According to the FISH results, type 021N was predominant in the reactor with long SRT, which had the clogging problem . On the other hand, other reactors (with SRTs of about 10 and 30 days) did not contain much type 021N, but some other filamentous bacteria dominated . Maximum EPS concentration (as mg/L) was observed in the reactor with long SRT . Also the abundance of two types of metazoa (Pristina sp . and tardigrades) was observed in the reactor with long SRT, which had the clogging problem and poor effluent quality. Water Sci Technol, 2003, 47(12), 43 - 8 Greenhouse gas production in wastewater treatment: process selection is the major factor; Keller J et al.; Many practical design and operating decisions on wastewater treatment plants can have significant impacts on the overall environmental performance, in particular the greenhouse gas (GHG) emissions . The main factor in this regard is the use of aerobic or anaerobic treatment technology . This paper compares the GHG production of a number of case studies with aerobic or anaerobic main and sludge treatment of domestic wastewater and also looks at the energy balances and economics . This comparison demonstrates that major advantages can be gained by using primarily anaerobic processes as it is possible to largely eliminate any net energy input to the process, and therefore the production of GHG from fossil fuels . This is achieved by converting the energy of the incoming wastewater pollutants to methane which is then used to generate electricity . This is sufficient to power the aerobic processes as well as the mixing etc . of the anaerobic stages . In terms of GHG production, the total output (in CO2 equivalents) can be reduced from 2.4 kg CO2/kg COD(removed) for fully aerobic treatment to 1.0 kg CO2/kg COD(removed) for primarily anaerobic processes . All of the CO2 produced in the anaerobic processes comes from the wastewater pollutants and is therefore greenhouse gas neutral, whereas up to 1.4 kg CO2/kg COD(removed) originates from power generation for the fully aerobic process . This means that considerably more CO2 is produced in power generation than in the actual treatment process, and all of this is typically from fossil fuels, whereas the energy from the wastewater pollutants comes primarily from renewable energy sources, namely agricultural products . Even a change from anaerobic to aerobic sludge treatment processes (for the same aerobic main process) has a massive impact on the CO2 production from fossil fuels . An additional 0.8 kg CO2/kg COD(removed) is produced by changing to aerobic sludge digestion, which equates for a typical 100,000 EP plant to an additional production of over 10 t CO2 per day . Preliminary cost estimates confirm that the largely anaerobic process option is a fully competitive alternative to the mainly aerobic processes used, while achieving the same effluent quality. Water Sci Technol, 2003, 47(12), 19 - 26 Feedforward-feedback control of an activated sludge process: a simulation study; Vrecko D et al.; In this paper a simulated plant based on a wastewater treatment benchmark is used to evaluate a number of controllers . Feedforward-feedback controllers for dissolved oxygen set-point and external carbon flow, and feedforward controller for internal recycle flow are evaluated separately and altogether . In the feedforward parts of the controllers, static physical models are incorporated in the control laws . The feedback parts of the controllers are used to compensate for model approximations . A simulation study shows that feedforward-feedback control of the activated sludge plant is more successful than standard PI control in meeting the effluent standards and reducing operational costs. Water Sci Technol, 2003, 47(12), 9 - 18 Linking floc structure and settling properties to activated sludge population dynamics in an SBR; Govoreanu R et al.; Over a period of 227 days properties of activated sludge grown in an sequencing batch reactor (SBR) operated under stable conditions were analyzed . Settling properties (sludge volume index (SVI)) of the activated sludge were compared with on-line measurements of floc size and size distribution obtained by using a laser light scattering technique (Malvern Mastersizer/S, Malvern, UK), and with measurements of microbial community dynamics analyzed by denaturing gradient gel electrophoresis (DGGE) patterns of 16S rRNA genes . In addition, microscopical observations were used to confirm the results . Three distinct stages in the SBR evolution were observed . In the first stage the structural floc properties showed predominant presence of floc-forming bacteria in the activated sludge . A good correlation between floc size, properties and microbial community evolution was observed . The second stage showed a good balance between floc-forming and filamentous bacteria, with good settling properties and a highly dynamic community in the SBR . In the third stage, an increase in the filamentous bacteria, which became predominant in the system was observed . Again, a good correlation between settling properties and floc size distribution was obtained and a new dominant species was observed in the DGGE patterns, which can be assumed to be a filamentous organism. Water Sci Technol, 2003, 48(1), 155 - 62 Effect of lime stabilisation of enhanced biological phosphorus removal sludges on the phosphorus availability to plants; Seyhan D et al.; This study investigates the phosphorus (P) availability in lime stabilised biological phosphorus removal sludges . Lime-stabilised sludge amendments (LS), non-stabilised sludge amendments (S) and amendments with a chemical fertiliser (TSP) were compared through plant uptake of P and Olsen-extractable P for this purpose . In the first part of the study, pot experiments were performed, where a dewatered biological phosphorus removal sludge was applied to pots at increasing rates of P . A P-deficient, alkaline soil was used in the experiments and Lollium perenne was the testing plant . In the second part (incubation tests), the waste activated sludge from an Enhanced Biological Phosphorus Removal (EBPR) process was mixed with the same soil at a pre-determined P-based rate . The pot experiments showed that, the efficiency of the fertilising materials, based on the minimum P applied to reach the maximum yield, was in the following order: S approximately equal to LS > TSP . However, the P concentration in the plant tissue was in the order of TSP > S >LS for all P application rates . In the incubation tests, the EBPR sludge raised the soil P-level from the low range to the medium range . The P-availability in TSP decreased rapidly with time whereas that in S and LS remained almost constant. Water Sci Technol, 2003, 48(1), 19 - 25 Recycling of wastewater-derived phosphorus in Swedish agriculture--a proposal; Kvarnstrom E et al.; In 2001 the Swedish Government commissioned the Swedish Environmental Protection Agency (Swedish EPA) (i) to examine the need for stricter human health and environmental regulations governing the agricultural use of sewage sludge and (ii) to propose national targets for the agricultural recycling of phosphorus (P) originating from wastewater . The Swedish EPA may propose: (i) stricter regulations on sludge treatment to limit the risk of spreading pathogens in the environment and transmission of infectious diseases; (ii) recycling of 20-30% of wastewater-P to agriculture by 2015 and recycling of 35-50% of wastewater-P to agriculture by 2025. J Chromatogr A, 2003 Jul 25, 1007(1-2), 31 - 7 Identification of ubiquinones and menaquinones in activated sludge by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry; Gao MC et al.; A sensitive analytical method has been developed for identification of ubiquinones (UQ-n(Hx)) and menaquinones (MK-n(Hx)) in activated sludge by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry in negative mode (LC-NI-APCI-MS) . Extraction and clean-up of samples were carried out on Sep-Pak Plus Silica solid-phase extraction cartridges . Complete separation of quinones was achieved with an ODS analytical column and using isopropyl ether-methanol (17:83, v/v) as the mobile phase . The compositions of ubiquinones and menaquinones were determined directly using combined information on retention time, the molecular ion mass and fragment ion masses . The lowest instrument quantitative detection limits (LODinst) for UQ-6, UQ-10, and Vitamin K1 were estimated to be 0.4, 4 and 0.12 ng (S/N = 10) using LC-NI-APCI-MS in SIM mode, and the lowest method detection limits (LODmeth) achieved by spiking experiment were estimated to be 0.2, 2 and 0.06 microg/g for UQ-6, UQ-10 and Vitamin K1, respectively . On the other hand, the LODinst for UQ-6, UQ-10, and Vitamin K1 were estimated to be 10, 100 and 2 ng (S/N = 10) using LC-NI-APCI-MS in full-scan mode, and the LODmeth were estimated to be 7, 60 and 1.2 microg/g for UQ-6, UQ-10, and Vitamin K1, respectively . Both LC-NI-APCI-MS and LC-UV/DAD were applied in the analysis of an activated sludge extract . UQ-n (n = 6-10), MK-n (n = 6-10), MK-n(H2) (n = 7-10), MK-n(H4) (n = 8-9) and MK-8(H6) were detected by LC-NI-APCI-MS, while UQ-6, UQ-7, MK-7(H), MK-9 and MK-10(H2) were not found by LC-UV/DAD . These results suggest that LC-NI-APCI-MS is more sensitive than LC-UV/DAD for the analysis of quinones in environmental samples such as sediment, activated sludge and bio-film in biological processes and other aquatic environments. Environ Technol, 2003 Jul, 24(7), 855 - 65 A survey of filamentous organisms at the Deer Island treatment plant; Lee S et al.; The Deer Island Treatment Plant (DITP) treating both domestic and industrial wastewater, has a peak flow capacity of up to 1270 million gallons per day (MGD) (3342 m3 min(-1) . The DITP contains a Pilot Plant, which consists of two identical pure oxygen activated sludge treatment trains, each with a maximum capacity of 1 MGD (2.63 m3 min(-1)) to simulate the maximum flow of the full size facility . This study documents the community of filamentous organisms living in the activatedsludge under various operational conditions in the Pilot Plant . Sixteen types of filamentous organisms were identified . The major filamentous organisms present in the Pilot Plant were Type 1701, Type 0041, Sphaerotilus natans, Microthrix parvicella, and Nocardia sp . Nocardia sp . was quite dominant in the early stages of the experimental period during high ambient temperatures (summer), indicating that temperature is one determining factor in the distribution of Nocardia sp . Thiothrix sp . was very sensitive to the dissolved oxygen (DO) level, with low DO values favoring the growth of the organisms . Microbiological observations made during the start-up and stable operation of the full-scale secondary treatment plant (maximum capacity 780 MGD) are also reported . No dominant filamentous species existed during the start-up period . Type 0803 and Type 1701, indicators of low oxygen level for the applied food to microorganism ratio, confirmed the low DO conditions of activated sludge tanks. Huan Jing Ke Xue, 2003 May, 24(3), 132 - 5 {Study on biohydrogen production by anaerobic biological fermentation of organic wasters}; Fan Y et al.; Biological hydrogen production is a process of applying anaerobic biological fermentation method to produce hydrogen from organic wastes . Hydrogen production potential of different microbiological source and organic wastes, as well as the composition of fermentation product in liquid phase, were studied in the batch culture experiments . Magnifying experiment of biohydrogen production was carried out in 30 L improvement UASB reactor using anaerobic fermentation of artificial wastewater containing starch by activated sludge process . The experiment confirm that hydrogen and carbon dioxide percentage of biogas were 40%-51% and 49%-60% under the condition of hydrogen production process (pH was 4.5-5.5 sludge VSS was 10 g/L; starch-COD was 5000 mg/L), and no methane was observed . Hydrogen purity was more than 97% by an absorption of sodium hydrate solution, continuous hydrogen production was more than 120 days. Huan Jing Ke Xue, 2003 May, 24(3), 70 - 3 {Observation and comparison on microstructure of immobilized Aerobacillus fusiformis under wastewater treatment}; Zhang Y et al.; Aiming at printing ink wastewater, a strain of bacterium was isolated from activated sludge, and identified as Aerobacillus fusiformis . The Aerobacillus fusiformis was respectively immobilized in calcium alginate gel, polyvinyl alcohol (PVA) and microporous ceramics and their microstructure were observed by scanning electron microscope (SEM) . It was found that calcium alginate gel might dissolve in the wastewater, and the activity was restricted as cells wrapped in PVA, so the COD removal ratio was low . The method of immobilized cells using microporous ceramics is simple and COD removal efficiency can be achieved . In addition, the immobilized bacterium could not be separated easily from the ceramics in the wastewater. Huan Jing Ke Xue, 2003 May, 24(3), 65 - 9 {Treatment of carbonization effluent by the ultrasonic radiation and activated sludge process}; Ning P et al.; The paper deals with the degradation of organic pollutants by the ultrasonic irradiation-activated sludge process . The treatment of the real coking wastewater of Kunming coke making-gas plant was studied with the water quality model . Using the ultrasonic irradiation-activated sludge process the organic pollutants in the real coking wastewater can be degraded effectively . The influence factors of the ultrasonic degradation effect such as initial concentration, aerated gas and ultrasonic density were investigated and mechanism was explored . The result shows that the ultrasonic degradation effect was high with the decrease of initial concentration of the CODCr, the presence of aerated gas and the increase of ultrasonic density . At the initial CODCr concentration of 807 mg/L, when air acted as aerated gas and only air itself (no ultrasound) was exerted on the wastewater, the degradation rate of the CODCr will be 4.5% . However, when the ultrasound of the intensity of 119.4 kW/m2 was exerted on the wastewater, the degradation rate of the CODCr will be 65% . Compared with the activated sludge process alone, the combination of the ultrasonic irradiation and activated sludge process can increase the degradation rate of the CODCr from 45% to 81% . The oxygen consumption rate of the carbonization effluent obviously decreased in the presence of the activated sludge . This shows the carbonization effluent is not biotoxic behind the ultrasonic irradiation. Wei Sheng Yan Jiu, 2003 May, 32(3), 187 - 9 {Study on biodegraded characteristics of endocrine disruptor di-n-butyl phthalate}; Wang L et al.; The biodegraded Characteristics of di-n-butyl Phthalate (DBP), endocrine disruptor were studied . The activated sludge was acclimated using DBP as the only carbon in the culture medium . DBP concentration was increased progressively from 0.05 g/L to 0.5 g/L . The degradation tests were carried out on the constant temperature table using the acclimated sludge at different PH, temperature, DBP concentration and hydraulic residence time . The results showed that DBP could be rapidly degraded-nearly 90% in 48 hours . The appropriate condition for DBP degradation was pH 6.0-8.0, temperature 25 degrees C-35 degrees C, DBP concentration no more than 300 mg/L, and hydraulic residence time 12 h-24 h . The form of biodegradation of DBP can be described as the first-order reaction model. Water Res, 2003 Sep, 37(16), 3855 - 66 Possible cause of excess sludge reduction in an oxic-settling-anaerobic activated sludge process (OSA process); Chen GH et al.; Modification of a conventional activated sludge process by inserting a sludge holding tank in a sludge return line forms an oxic-settling-anaerobic (OSA) process that may provide a cost-effective way to reduce excess sludge production in activated sludge processes . In this paper we systematically evaluate the following possible scenarios that may explain the reduction of excess sludge in the OSA process: (i) . energy uncoupling, (ii) . domination of slow growers, (iii) . soluble microbial products (SMPs) effect and (iv) . sludge decay in the sludge holding tank under a low oxidation-reduction potential (ORP) condition . Results show that only the final scenario may reasonably explain this reduction . It has also been found that the sludge decay process in the sludge holding tank may involve the reduction of the cell mass. Water Res, 2003 Sep, 37(16), 3821 - 36 Comparison and evaluation of empirical zone settling velocity parameters based on sludge volume index using a unified settling characteristics database; Giokas DL et al.; Over the past few decades classic and contemporary research on the process of secondary clarification in activated sludge plants has illuminated several aspects of the solids-flux theory which actually require a closer examination . Inter alia the most challenging and controversial part in the field has been the development of reliable models for the settling properties of the activated sludge in the settler . Numerous studies have been performed aiming at the evolvement of reliable mathematical formulas that would satisfactorily describe this behaviour, but no universally accepted solution seems to exist to date . That is mostly because different experimental conditions, sludge types and instrumentation have been employed, thus complicating the process of reaching a conclusive result . In order to bring theoretical and practical developments of secondary settling tank design and simulation closer together, a number of related tasks are addressed in this study by the use of an integrated and unified settling characteristics database . Several drawbacks and advantages of the methodologies published hitherto are examined on a universal basis and under the same assumptions in order to reveal artifacts that complicate the procedure of settling velocity estimation . It is suggested that universally accepted solutions may be feasible especially for design purposes . For simulation analysis real-time data of settling velocity should be tested rather than values derived from laboratory experiments which are shown to produce different results depending on the applied approach . In conclusion, an integrated database is proposed as a means for a more robust and universally accepted design procedure. J Colloid Interface Sci, 2003 Jul 15, 263(2), 498 - 505 Hydrodynamic drag force exerted on activated sludge floc at intermediate Reynolds number; Chung HY et al.; We hung the activated sludge flocs on an elastic nylon stick and then subjected it to a uniform water flow and measured its displacement . The hydrodynamic drag force exerted on the floc was subsequently estimated, both for cationic flocculated flocs and for flocculated and then frozen/thawed flocs . A confocal laser scanning microscope (CLSM) was employed to probe the interior structure of flocs . Polyelectrolyte flocculation leads to a compact global structure, and hence high drag force exerted on the floc by water . The corresponding C(D)Omega value at Re=12-27 for flocs ranges from 1.58 to 3.61 . Fast freezing would little affect the hydrodynamic drag force . Slow freezing, in contrast, considerably consolidated the floc structure and hence presented impermeable sphere-like behavior of the slowly frozen/thawed flocs. Water Sci Technol, 2003, 47(11), 297 - 303 Oxygen transfer into activated sludge with high MLSS concentrations; Krampe J et al.; In this report, tests on the impact of the sludge properties on the oxygen transfer at low and high solids contents are presented . Additional to the oxygen transfer tests, the activated sludge was intensively analysed to examine the changes of the alpha-factor in relation to the sludge properties (rheology, EPS, CST, etc.) . The alpha-factor did strongly decrease in all sludge types at increasing MLSS or increasing viscosity, respectively . In the second test stage, the impact of the aeration system was examined in detail . For these tests, the same sludge from a membrane bioreactor was used throughout . Apart from the impact of the power density in the reactor and the specific air throughput, the main focus was on the economic efficiency of the examined systems in cases of high MLSS . It became apparent that up to solids contents of 18 g/l the fine-bubble aeration is the most economically efficient method. Water Sci Technol, 2003, 47(11), 289 - 95 Non-filamentous sludge bulking caused by a deficiency of nitrogen in industrial wastewater treatment; Peng Y et al.; Deficiency in the nutrient supply such as nitrogen usually results in activated sludge bulking and this phenomenon often takes place in the industrial wastewater treatment plants with activated sludge process . The effects of nitrogen deficiency on activated sludge bulking were studied specially in some experiments carried out in a sequencing batch reactor fed with brewing process wastewater in this paper . The experimental results showed that the sludge settled properly at an influent BOD/N value of 100/4 . When the value of BOD/N was 100/3, filaments had an excessive growth at one time during the reaction process . Afterwards, the number of filamentous bacteria began to reduce and simultaneously an excessive growth of viscous Zoogloea with high percentage of moisture was observed and non-filamentous activated sludge bulking occurred . When the influent BOD/N value was 100/2, the excessive growth of filamentous microorganisms could not be observed at all times and the sludge characterization was similar to the case in which BOD/N value was 100/3 . When the value of influent BOD/N was 100/0.94, more serious non-filamentous bulking occurred . Furthermore, the effects of nitrogen deficiency on the nitrogen sources and phosphorus sources utilization rate and the COD removal rate were investigated in the experi