Activated sludge

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 experiments.

Water Sci Technol, 2003, 47(11), 267 - 73
Structure-function dynamics and modeling analysis of the micro-environment of activated sludge floc; Li B et al.; Biodegradation by microorganisms and mass transfer resistance in the micro-environment of activated sludge floc can cause changes in substrate and dissolved oxygen concentrations within the floc and can contribute to stratification of microbial processes inside the flocs . In this study, an integrated model of the microenvironment of the activated sludge floc was developed for floc from wastewaters from several sources and of varying strengths for dynamic simulation of the combined biological processes of COD and nitrogen removal . The model simulation results and measured profiles show the heterogeneous and gradient-governed microenvironment of activated sludge floc under different substrate and bulk oxygen concentrations . The substrate concentration increase zones inside the floc were present in all activated sludge floc from the Miller Brewing Co . wastewater treatment facility (high pollutant strength), with an oxygen penetration depth of only 0.15 mm into the outer layer . The anoxic and substrate concentration increase zones also dominated in the activated sludge floc from the Mill Creek Plant influent (medium pollutant strength), with the outer layer (0.20 mm) participating in the metabolism of the pollutants . The radius of the substrate concentration increase zone inside the sludge floc decreased with pollutant removal along the length of the tank . When the pollutant concentration in the bulk wastewater was low (Muddy Creek Plant), the substrate concentration increase zone disappeared; the whole floc was aerobic and in a high redox status . Our experiments and model analyses demonstrate that the microorganisms' structure-functions inside activated sludge floc change with the bulk substrate concentration and dissolved oxygen concentration.

Water Sci Technol, 2003, 47(11), 251 - 7
Modelling the effect of shear history on activated sludge flocculation; Biggs C et al.; The aim of this paper is to investigate the effect of shear history on activated sludge flocculation dynamics and to model the observed relationships using population balances . Activated sludge flocs are exposed to dramatic changes in the shear rate within the treatment process, as they pass through localised high and low mixing intensities within the aeration basin and are cycled through the different unit operations of the treatment process . We will show that shear history is a key factor in determining floc size, and that the floc size varies irreversibly with changes in shear rate . A population balance model of the flocculation process is also introduced and evaluated.

Water Sci Technol, 2003, 47(11), 241 - 50
Elevated precursor 16S rRNA levels suggest the presence of growth inhibitors in wastewater; Stroot PG et al.; Conventional activated sludge systems require bacteria to grow to avoid washout through decay and routine solids wasting . Recently we developed a procedure targeting precursor 16S ribosomal RNA to measure the in situ growth activity of phylogenetically defined microbial populations, and this procedure was used to study the growth of bacteria in activated sludge systems . The current study significantly expands this previous work by quantifying levels of precursor 16S ribosomal RNA within individual cells of pure cultures of bacteria exposed to various culture conditions . Initially, three ranges (Type I, Type II, and Type III) of precursor 16S ribosomal RNA levels were defined by whole cell fluorescence in situ hybridization of a pure culture of Acinetobacter calcoaceticusT prepared in three culture conditions . Low levels of precursor 16S ribosomal RNA (Type I) corresponded to a stationary phase culture prepared overnight in Luria-Bertani medium . Intermediate levels of precursor 16S ribosomal RNA (Type II) corresponded to a culture transferred into fresh Luria-Bertani medium, and high levels of precursor 16S ribosomal RNA (Type III) corresponded to a culture treated with the growth inhibiting antibiotic chloramphenicol . Subsequently, the abundance of individual cells of each Type were measured in four different pure cultures after exposure to 0.45-microm filtered primary effluent collected from four different conventional activated sludge treatment plants in Cincinnati, OH, USA . Individual cells of each Type were observed in the culture of A . calcoaceticusT exposed to each of the four primary effluents . Only Type I cells were observed in cultures of A . johnsoniiT, A . johnsonii strain 210a, and Escherichia coliT exposed to each of the four primary effluents . These results suggest that the growth of A . calcoaceticusT was inhibited by an unidentified component of filtered primary effluent present in each of the four wastewaters; whereas the growth of A . johnsoniiT, A . johnsonii strain 210a, and E . coliT were not inhibited . These results have significance for understanding the growth of phylogenetically defined microbial populations within activated sludge treatment systems . If the pattern of elevated p16S rRNA levels observed in A . calcoaceticusT is prevalent in many microbial populations in activated sludge systems, this may have implications for preventing washout of critical microbial populations that may be experiencing growth inhibition.

Water Sci Technol, 2003, 47(11), 219 - 25
Modification of Activated Sludge Model no . 3 considering direct growth on primary substrate; Karahan-Gul O et al.; This paper provides the structural framework for the proposed modified version of Activated Sludge Model No . 3 (ASM3), where direct heterotrophic growth on readily biodegradable substrate is included as a new process and provision is made so that growth on internal storage compounds is started sequentially, after the depletion of the external primary substrate pool . The results have provided strong indication that there was a need for considering direct growth on primary substrate as a significant biological mechanism.

Water Sci Technol, 2003, 47(11), 137 - 44
Adaptive control of the nitrate level in an activated sludge process; Ekman M et al.; In an activated sludge process for nitrogen removal, nitrate may be reduced to nitrogen gas by facultative heterotrophic bacteria in an anoxic environment . In order to guarantee sufficient supplies of readily biodegradable carbon compounds, an external carbon source often needs to be added . In this paper, an automatic control strategy for controlling the nitrate level using an external carbon source is presented . The external carbon source is added in the first anoxic zone to control the nitrate concentration in the last anoxic zone . Key process parameters are estimated on-line for a simplified Activated Sludge Model No 1 . The estimated parameters are used for updating a linear quadratic controller . The strategy is illustrated in a simulation study with realistic influent data and is shown to perform very well.

Water Sci Technol, 2003, 47(11), 123 - 8
A thermal adaptation of bacteria to cold temperatures in an enhanced biological phosphorus removal system; Erdal UG et al.; Temperature is one of the key parameters that affects the reaction kinetics and performance of enhanced biological phosphorus removal (EBPR) systems . Although studies agree regarding the effect of temperature on kinetic reaction rates, there are contradictory results in the literature regarding the effect of temperature on EBPR system performance . Early investigators (Sell, Ekama et al., Daigger et al.) reported better performance with lower temperatures, but others have reported partial or complete loss of EBPR functions at low temperatures (McClintock et al., Brdjanovic et a., Beatons et al.) . One speculation is that deterioration in the EBPR system performance at cold temperatures can be attributed to rigid-like behavior of the cell membranes . Most cells (not all) on the other hand have the ability to alter their membrane fatty acid composition as temperature changes in order to keep their membrane at nearly the same fluidity despite the temperature changes . This unique ability is known as homeoviscous adaptation . In this study, homeoviscous adaptation by EBPR activated sludge was investigated for a series of temperatures ranging from 20 degrees C to 5 degrees C using a lab scale continuous flow EBPR system fed with acetate and supplemental yeast extract . The fatty acid analysis results suggested that the unsaturated to saturated fatty acid ratio increased from 1.40 to 3.61 as temperature dropped from 20 to 5 degrees C . The increased cis-9-hexadecanoic acid (C 16:1) at 5 degrees C strongly indicated the presence of homeoviscous adaptation in the EBPR bacterial community . Thus the cell membranes of the EBPR community were still in a fluid state, and solute transport and proton motive force were operable even at 5 degrees C . It was concluded that loss of EBPR performance at low temperatures is not related to the physical state of the cellular membranes, but is possibly related to the application of unsuitable operational conditions (low SRT, excessive electron acceptors, low anaerobic detention time, non-acclimated sludge, etc.).

Appl Environ Microbiol, 2003 Aug, 69(8), 4375 - 82
Comparing the dehalogenase gene pool in cultivated alpha-halocarboxylic acid-degrading bacteria with the environmental metagene pool; Marchesi JR et al.; Culture-dependent and culture-independent approaches were used to determine the relationship between the dehalogenase gene pool in bacteria enriched and isolated on 2,2-dichloropropionic acid (22DCPA) and the environmental metagene pool (the collective gene pool of both the culturable and uncultured microbes) from which they were isolated . The dehalogenases in the pure-cultures isolates, which were able to degrade 22DCPA, were similar to previously described group I and II dehalogenases . Significantly, the majority of the dehalogenases isolated from activated sludge by degenerate PCR with primers specific for alpha-halocarboxylic acid dehalogenases were not closely related to the dehalogenases in any isolate . Furthermore, the dehalogenases found in the pure cultures predominated in the enrichments but were a minor component of the community used to inoculate the batch cultures . Phylogenetic analysis of the dehalogenase sequences isolated by degenerate PCR showed that the diversity of the group II deh gene was greater than that of the group I deh gene . Direct plating of the activated sludge onto minimal media supplemented with 22DCPA resulted in biomass and DNA from which dehalogenases were amplified . Analysis of the sequences revealed that they were much more closely related to the sequences found in the community used to start the enrichments . However, no pure cultures were obtained with this isolation method, and thus no pure cultures were available for identification . In this study we examined the link between genes found in pure cultures with the metagene pool from which they were isolated . The results show that there is a large bias introduced by culturing, not just in the bacteria isolated but also the degradative genes that they contain . Moreover, our findings serve as a caveat for studies involving the culturing of pure cultures of bacteria and conclusions which are drawn from analysis of these organisms.

Environ Sci Technol, 2003 Jul 15, 37(14), 3171 - 80
Comparison performances of membrane bioreactor and conventional activated sludge prcesses on sludge reduction induced by Oligochaete; Wei Y et al.; Pilot-scale experiments were carried out to compare sludge reduction induced by Oligochaete in a submerged membrane bioreactor (MBR) and a conventional activated sludge (CAS) reactor for 345 d . Worm growth in the CAS reactor was much better than in the MBR . The average worm density of the aeration tank in the CAS reactor was 71 total worms/mg of volatile suspended solids (VSS), much higher than that in the MBR (10 total worms/mg of VSS) . Worms did not naturally produce in the MBR, and the dominant worm type in the MBR depended on sludge inoculation from the CAS reactor . Only two types of worms were found in the MBR, Aeolosoma hemprichicii and Nais elinguis . Worm presence and disappearance in the MBR alternated . Worms in the CAS reactor occurred nearly throughout the operating period and were continuously maintained at over 30 total worms/mg of VSS in the aeration tank for 172 d . Three types of worm were found in the CAS reactor, A . hemprichicii, Pristina aequiseta, and N . elinguis, but P . aequiseta was present only occasionally . The alternating dominance of worm types in both reactors changed between Aeolosoma and Nais, and the time of Aeolosoma dominance was longer than that of Nais dominance . Worm growth in the MBR contributed to neither sludge reduction nor improvement of sludge settling characteristics because of low density . But worm presence and bloom in the CAS reactor greatly decreased sludge yield and improved sludge settling characteristics at high density . Both the average sludge yield (0.17 kg of suspended solids (SS)/kg of chemical oxygen demand removed (CODremoved)) and sludge volume index (60 mL/g) in the CAS reactor were much lower than those in the MBR (0.40 kg of SS/kg of CODremoved and 133 mL/g) . Nais had more potential for sludge reduction than Aeolosoma . Worm growth had little impact on effluent quality in the MBR but affected effluent quality very much in the CAS reactor.

Bioresour Technol, 2003 Nov, 90(2), 215 - 20
Determination of some rheological parameters for the characterization of activated sludge; Tixier N et al.; The rheological characterization of activated sludge originating from different aeration tanks and from a lab-scale plant was carried out using rotation tests . Two rheological parameters were used: limit viscosity (mu(infinity)) and reduced hysteresis area (rHa) . Mu(infinity) was strongly influenced by the total suspended solids (TSS) content of sludge and an exponential relation was found between TSS and the rheological parameter mu(infinity) . Significant differences in sludge viscosity were found for sludge of different origins, but all of 10 g/l TSS content, indicating ability of viscosity to show different sludge qualities . Marked changes in activated sludge microorganisms communities were shown to have an influence on rheological parameters . During aerobic digestion of sludge, variations in mu(infinity) were noticed, indicating change of sludge quality . An over-growth of filamentous bacteria species was shown to induce a particular rheological behavior which could be characterized by rHa . This parameter was proposed as an index of filamentous bacteria proliferation in activated sludge aeration tanks.

Environ Technol, 2003 Apr, 24(4), 465 - 70
Phenol removal in upgraded facultative waste stabilisation ponds; Avelar FJ et al.; Treatment of wastewater containing phenol using laboratory scale waste stabilisation ponds enriched with activated sludge was studied . After enrichment, the efficiency of these ponds under high phenol loading rates (i.e . up to 408 kg phenol ha(-1) day(-1)) was studied . At phenol loading rates of 6, 52, 312, 636 and 972 COD ha(-1) day(-1), the phenol removal efficiencies were 77, 69, 76, 59 and 52%, respectively . The results suggest that enrichment is an effective potential method to increase the removal capability of facultative ponds, not only or easily biodegradable compounds but also for xenobiotics.

Biotechnol Prog, 2003 Jul-Aug, 19(4), 1156 - 61
Bioaugmentation strategies for remediating mixed chemical effluents; van der Gast CJ et al.; Operationally exhausted metal working fluids are chemically mixed, produced in large quantities (400 000 tonnes year in the U.K.), and potentially environmentally toxic . It is essential to develop more reliable and economical approaches for their disposal . We investigated the effectiveness of a defined bacterial consortium, constructed specifically for treating metal-working fluid (MWF), and contrasted its performance to that of undefined inocula from activated sludge . Construction of the consortium was based on knowledge of the diversity of bacterial communities that naturally colonize MWF and determination of their catabolic abilities and tolerance to the chemical constituents . Chemical analysis of the inoculated MWF bioreactor revealed that, after 100 h at 28 degrees C, the defined inoculum reduced the pollution load by over 80% from an initial chemical oxygen demand of approximately 48 000 mg L(-)(1) . The inocula performance was approximately 50% more effective than that of the undefined microbial community from the activated sludge . Furthermore, the performance of the constructed consortium was more reproducible than that of an undefined community, an essential feature for bioaugmentation treatment of industrial wastes.

Int J Syst Evol Microbiol, 2003 Jul, 53(Pt 4), 1075 - 80
Classification of Ralstonia pickettii-like isolates from the environment and clinical samples as Ralstonia insidiosa sp . nov; Coenye T et al.; Thirteen Ralstonia pickettii-like isolates from the environment (water, soil and activated sludge) and human clinical samples (including respiratory secretions of cystic fibrosis patients) were investigated in a polyphasic taxonomic study that employed 16S rDNA sequence analysis, DNA-DNA hybridization, determination of DNA base composition, whole-cell protein analysis, biochemical characterization and PCR-based assays . All isolates were classified as a novel Ralstonia species, for which the name Ralstonia insidiosa sp . nov . is proposed . The type strain, LMG 21421T (= CCUG 46789T), was isolated from the sputum of a patient with acute lymphoblastic leukaemia . R . insidiosa can be differentiated from other species of the genus Ralstonia and phenotypically similar species (including the Burkholderia cepacia complex and Achromobacter xylosoxidans) by a variety of biochemical tests, whole-cell protein analysis and several PCR-based assays . Some outstanding issues in the taxonomy of the genus Ralstonia are also discussed.

Int J Syst Evol Microbiol, 2003 Jul, 53(Pt 4), 1031 - 6
Parvularcula bermudensis gen . nov., sp . nov., a marine bacterium that forms a deep branch in the alpha-Proteobacteria; Cho JC et al.; Two bacterial strains, HTCC2503T and HTCC2517, were isolated from the Bermuda Atlantic Time Series Station in the western Sargasso Sea, Atlantic Ocean, by new high-throughput culture methods that rely on dilution to extinction in very-low-nutrient media . Characterization of the two strains by polyphasic approaches revealed that they belonged to the same species . These isolates are gram-negative, strictly aerobic, chemoheterotrophic, slightly motile short rods with a single flagellum . The temperature, pH and NaCl concentration ranges for growth were 10-37 degrees C, 6.0-9.0 and 0.75-20% (w/v), respectively . Colonies on marine agar were very small (0.3-0.8 mm in diameter), yellowish-brown and very hard . Carotenoid pigments were synthesized but bacteriochlorophyll a was not . Several kinds of pentose, hexose, sugar alcohol, oligosaccharide and amino acid were utilized as sole carbon sources . Oxidase was produced, but catalase was not . All cellular fatty acids were even-numbered monounsaturated or saturated fatty acids and the major fatty acid was cis-7-octadecenoic acid (73.3%) . The DNA G + C content of strain HTCC2503T was 60.8 mol% . Phylogenetic analyses of 16S rRNA gene sequences clearly indicated that the strains formed a distinct lineage, allied with activated sludge environmental clone H9, in the alpha-Proteobacteria . The clade containing strains HTCC2503T and HTCC2517 and clone H9 could not be phylogenetically associated with any of the six known orders of the alpha-Proteobacteria . From this polyphasic evidence, it is proposed that the novel strains should be classified as Parvularcula bermudensis gen . nov., sp . nov . The type strain is HTCC2503T (= ATCC BAA-594T = KCTC 12087T) and the reference strain is HTCC2517.

Int J Syst Evol Microbiol, 2003 Jul, 53(Pt 4), 953 - 63
Seven novel species of Acinetobacter isolated from activated sludge; Carr EL et al.; Thirteen isolates of Acinetobacter were obtained from activated sludge plants in Victoria, Australia . Earlier 16S-23S rDNA genomic fingerprinting and partial 16S rDNA sequence data had suggested that these isolates might contain previously undescribed species . This view was confirmed here . A polyphasic taxonomic approach involving phenotypic characterization, near-complete 16S rDNA sequence data and DNA-DNA hybridization analyses support the view that seven novel genomic species can be differentiated in this group of isolates . However, when fluorescence in situ hybridization (FISH) studies were performed with a 16S-rRNA-targeted probe specific for the genus Acinetobacter, used to identify Acinetobacter in activated sludge plants, all these strains responded positively . This suggests that these isolates would not have been missed in earlier FISH studies where their role as polyphosphate-accumulating bacteria has been questioned . This report describes these isolates and proposes that they be named Acinetobacter baylyi (type strain B2T = DSM 14961T = CIP 107474T), Acinetobacter bouvetii (type strain 4B02T = DSM 14964T = CIP 107468T), Acinetobacter grimontii (type strain 17A04T = DSM 14968T = CIP 107470T), Acinetobacter tjernbergiae (type strain 7N16T = DSM 14971T = CIP 107465T), Acinetobacter towneri (type strain AB1110T = DSM 14962T = CIP 107472T), Acinetobacter tandoii (type strain 4N13T = DSM 14670T = CIP 107469T) and Acinetobacter gerneri (type strain 9A01T = DSM 14967T = CIP 107464T).

Chemosphere, 2003 Sep, 52(10), 1701 - 10
Relation between extracellular polymers' composition and its ability to complex Cd, Cu and Pb; Guibaud G et al.; Activated sludges originated from wastewater treatment plants (WWTPs) play an important role in heavy metal removal from effluents . Extracellular polymers (ECP) form a major part of the activated sludge and are heavily involved in biosorption of heavy metals . The complexation of three heavy metals (Cd, Cu and Pb) with ECP extracted from six activated sludges, originated from different WWTPs, was investigated at pH 7 . ECP in the study were shown to be mainly composed of proteins, humic acids, uronic acids and polysaccharides along with smaller amounts of lipids and nucleic acids . IR spectra confirmed the presence of the functional groups usually found in the ECP and the content in each fraction was determined using colorimetric methods . The determination of surface charge was carried out on each ECP sample and allowed two pK(a) values characteristic of two distinctive functional groups to be determined . At the pH used in the study, the value of these constants indicates that only one functional group is under protonated form . A polarographic method was used to determine the complexation parameters (number of binding sites and complexation constant) of ECP solutions towards metals . The following orders were established for the number of binding sites: Cu > Pb > or = Cd and for the stability of the ECP-metal complex: Cd > Pb approximately = Cu . A matrix of correlation between the composition of the polymers and the complexation parameters showed that the number of binding sites and the complexation constant were strongly linked to proteins, polysaccharides and humic substances content.

Water Res, 2003 Sep, 37(15), 3652 - 7
Lipase and protease extraction from activated sludge; Gessesse A et al.; In the process of wastewater treatment hydrolysis of polymeric substances is the first and rate-limiting step . A closer study of the enzymes catalysing these reactions is essential for a better understanding of the microbial activity in the wastewater treatment process . Therefore, development of gentle and efficient enzyme extraction methods from environmental samples is very important . In this study we present a method for the extraction of lipases and proteases from activated sludge using the non-ionic detergent Triton X-100, EDTA, and cation exchange resin (CER), alone or in combination for the extraction of lipases and proteases from activated sludge . The sludge was continuously stirred in the presence of either buffer alone or in the presence of detergent and/or chelating agents . In all cases, a marked reduction in floc size was observed upon continuous stirring . However, no lipase activity and negligible protease activity was extracted in the presence of buffer alone, indicating that enzyme extraction was not due to shear force alone . The highest lipase activity was extracted using 0.1% Triton X-100 above which the activity was gradually decreasing . For proteases, the highest activity was obtained in the presence of 0.5% Triton X-100 and no decrease in activity was observed . Differences observed in the extraction efficiency of the two enzymes indicate the need for optimisation of the extraction process for the different enzymes or the extracellular polymeric substances from activated sludge.

Water Res, 2003 Sep, 37(15), 3632 - 45
Impacts of structural characteristics on activated sludge floc stability; Wilen BM et al.; Activated sludge samples from seven full-scale plants were investigated in order to determine the relationship between floc structure and floc stability . Floc stability was determined by shear sensitivity and floc strength . Floc structure was considered in terms of two size scales, the micro- and macrostructure . The microstructure refers to the organization of the floc components, such as the individual microorganisms . The macrostructure refers to the overall floc . The floc macrostructure was characterized by filament index, sludge volume index, size, and fractal dimension . It had a significant impact on floc stability . Large and open flocs with low fractal dimensions containing large number of filaments were more shear sensitive and had lower floc strength compared to small and dense flocs . Fluorescent in situ hybridization analysis indicated that the organization of the bacterial cells might also have an effect on the floc stability.

Water Res, 2003 Sep, 37(15), 3602 - 11
Production of polyhydroxyalkanoates (PHA) by activated sludge treating municipal wastewater: effect of pH, sludge retention time (SRT), and acetate concentration in influent; Chua AS et al.; In this paper, the production of biodegradable plastics polyhydroxyalkanoates (PHA) by activated sludge treating municipal wastewater was investigated . The effect of three operational factors, i.e . the acetate concentration in influent, pH, and sludge retention time (SRT) were studied . Sludge acclimatized with municipal wastewater supplemented with acetate could accumulate PHA up to 30% of sludge dry weight, while sludge acclimatized with only municipal wastewater achieved 20% of sludge dry weight . It was found that activated sludge with an SRT of 3 days possessed better PHA production capability than sludge with an SRT of 10 days . Sludge acclimatized under pH 7 and 8 conditions in sequencing batch reactors (SBRs) exhibited similar PHA production capability . However, in PHA production batch experiments, pH value influenced significantly the PHA accumulation behavior of activated sludge . When pH of batch experiments was controlled at 6 or 7, a very low PHA production was observed . The production of PHA was stimulated when pH was kept at 8 or 9.

Water Res, 2003 Sep, 37(15), 3569 - 78
Biosolids accumulation and biodegradation of domestic wastewater treatment plant sludge by developed liquid state bioconversion process using a batch fermenter; Alam MZ et al.; The biosolids accumulation and biodegradation of domestic wastewater treatment plant (DWTP) sludge by filamentous fungi have been investigated in a batch fermenter . The filamentous fungi Aspergillus niger and Penicillium corylophilum isolated from wastewater and DWTP sludge was used to evaluate the treatment performance . The optimized mixed inoculum (A . niger and P . corylophilum) and developed process conditions (co-substrate and its concentration, temperature, initial pH, inoculum size, and aeration and agitation rate) were incorporated to accelerate the DWTP sludge treatment process . The results showed that microbial treatment of higher strength of DWTP sludge (4% w/w of TSS) was highly influenced by the liquid state bioconversion (LSB) process . In developed bioconversion processes, 93.8 g/kg of biosolids was enriched with fungal biomass protein of 30 g/kg . Enrichment of nutrients such as nitrogen (N), phosphorous (P), potassium (K) in biosolids was recorded in 6.2% (w/w), 3.1% (w/w) and 0.15% (w/w) from its initial values of 4.8% (w/w), 2.0% (w/w) and 0.08% (w/w) respectively after 10 days of fungal treatment . The biodegradation results revealed that 98.8% of TSS, 98.2% of TDS, 97.3% of turbidity, 80.2% of soluble protein, 98.8% of reducing sugar and 92.7% of COD in treated DWTP sludge supernatant were removed after 8 days of microbial treatment . The specific resistance to filtration (SRF) in treated sludge (1.4x10(12) m/kg) was decreased tremendously by the microbial treatment of DWTP sludge after 6 days of fermentation compared to untreated sample (85x10(12) m/kg).

Syst Appl Microbiol, 2003 Jun, 26(2), 211 - 27
Long-term population dynamics and in situ physiology in activated sludge systems with enhanced biological phosphorus removal operated with and without nitrogen removal; Lee N et al.; Quantitative fluorescence in situ hybridization (FISH) and the combination of FISH with microautoradiography (MAR) were used in order to study the long-term population dynamics (2.5 years) and the in situ physiology in two parallel activated sludge pilot systems with enhanced biological phosphorus removal (EBPR) . The two systems received the same influent wastewater, but were differently operated (with and without nitrogen removal, respectively) . Both systems showed a significant P removal that increased when different substrates (phosphorus (P), acetate and glucose, respectively) were added to the influent wastewater . Rhodocyclus-related bacteria were present in both systems in significant numbers (ranging from 4 to 28%) throughout the whole period . This supports the hypothesis that these bacteria occur in significant numbers in different types of well-operating EBPR activated sludge processes . However, we observed a lower correlation (< 0.5) for the amount of Rhodocyclus-related bacteria to the P content in activated sludge than previous studies (> 0.9) . The Actinobacteria were the only additional group of bacteria which showed a similar degree of correlation to the P content in activated sludge as the Rhodocyclus-related bacteria--but only for the system without nitrogen removal . Significant amounts (< or = 12%) of glycogen-accumulating bacteria (GAOs) were detected in the system with nitrogen removal (but not in the other system), but had no, in contrast to previous observations, apparent negative effect on the overall EBPR performance . FISH-MAR indicated that a significant part of the Betaproteobacteria (part of them identified as Rhodocyclus-related bacteria) as well as the Actinobacteria were able to take up 33Pi, {3H}-acetate and {3H}-glucose under anaerobic-aerobic conditions . The contribution of anoxic 33Pi uptake under alternating anaerobic-anoxic conditions was significantly lower . Interestingly, not all Rhodocyclus-related bacteria showed uptake of these three radioactive substrates . This may be due to differences in metabolic state, physiological potential or genotype, not detectable by the present probe set for Rhodocyclus-related bacteria . Comparison of the 33Pi, {3H}-acetate and {3H}-glucose uptake by activated sludge after different fixation and incubation procedures showed that a part of the observed 33Pi uptake may have been caused by a combination of a biological and chemical or biologically induced chemical P adsorption.

Syst Appl Microbiol, 2003 Jun, 26(2), 165 - 71
Effects of culture conditions on the mycolic acid composition of isolates of Rhodococcus spp . from activated sludgefoams; Stratton HM et al.; The influence of two different carbon sources and three incubation temperatures on the mycolic acid compositions of three Rhodococcus isolates from activated sludge was examined using Selective Ion Monitoring (SIM) gas chromatography-mass spectrometry (GC-MS) . Considerable qualitative and quantitative differences were detected in the mycolic acid compositions of the three very closely related isolates grown under the same conditions . Culture age also affected both the chain lengths and proportions of saturated mycolic acids detected in cell extracts, but not in the same manner for each isolate . Mycolic acids generally were of shorter chain lengths in cells grown with Tween 80 compared to glucose grown cells in strain 11R but the opposite situation occurred with strains A7 and D5 . In all three, the proportion of unsaturated mycolic acids decreased with increasing growth temperatures . The taxonomic relevance of these observations and possible explanations for the observed changes in mycolic acid composition under various culture conditions are discussed.

Water Sci Technol, 2003, 47(10), 197 - 204
Hazard identification of pharmaceutical wastewaters using biodegradability studies; Zgajnar Gotvajn A et al.; A reliable wastewater characterization is an integral part of treatment and management strategies for industrial effluents . This is especially true for the pharmaceutical industry, which exhibits significant differences in its line of activity, generating effluents of very specific and complex natures . Any hazard or risk assessment of wastewater and/or determination of its treatability must include an evaluation of its degradability . Usually various non-standardized laboratory or pilot-scale long-term tests are run by measuring summary parameters for several days to determine the biodegradation potential of the effluent . A complex approach, based on stabilization studies, was proposed to determine the hazardous impact of wastewaters in terms of biodegradable and persistent toxicity . The objective of our work was to carry out complex hazard evaluation of pharmaceutical wastewaters . Whole effluent toxicity was determined using two different toxicity tests . First, we measured the inhibition of oxygen consumption by activated sludge . The test indicated toxicity of the wastewater and thus we performed an additional acute toxicity test with luminescent bacteria Vibrio fisheri . The next step was the determination of whole effluent ready biodegradability . It was determined with simultaneous measurement of oxygen consumption (ISO 9804) and carbon dioxide production (ISO 9439) in a closed respirometer, accompanied by DOC/IC measurements . The pharmaceutical wastewater degraded readily (83%, lag phase was 2 days, biodegradation rate was 0.33999 day(-1)) on the basis of O2 measurements . The biodegradation, calculated from the CO2 measurements, was comparable . We also applied mass balances of DOC/IC at the beginning and at the end of biodegradation experiments to confirm the extent and rate of biodegradation . The determination of hazardous impact and treatability of the effluent was concluded with aerobic stabilization studies . Biodegradation of the wastewater during the study was followed by relevant biochemical analysis and DOC/IC mass balance.

Water Sci Technol, 2003, 47(10), 109 - 15
Functional metal-binding proteins by metal-stimulated bacteria for the development of an innovative metal removal technology; Antsuki T et al.; Heavy metal pollution has become an environmental problem throughout the world because heavy metal can be accumulated into the food chain and bring about serious problems, not only for ecosystems but also for human health . In this study, functional metal-binding proteins (FMBPs) were isolated from a metal-stimulated activated sludge culture with the aim of applying them to an innovative metal removal technology . Activated sludge bacteria was cultured in growth media including copper ion, and the stimulation of protein production by copper ion led to the 14% increase in a quantity of extracted crude proteins per 1 g of bacterial cell pellet (wet) . In order to isolate FMBPs, extracted crude proteins were applied to the immobilized metal affinity column in which each of copper, nickel and zinc was used as a ligand . Several FMBPs were succesfully isolated from copper-stimulated bacteria . One of FMBPs (molecular weight of about 40 kDa) exhibited an ability to adsorb all three metals . The multi metal-binding property of this FMBP could be applied to an innovative metal removal technology . Furthermore, isolated FMBPs that could capture only one kind of heavy metal would also be attractive as a metal adsorbent in recovering a specific metal as a resource from wastewater, including several heavy metals.

Water Sci Technol, 2003, 47(10), 33 - 9
Feasibility study to upgrade a textile wastewater treatment plant by a hollow fibre membrane bioreactor for effluent reuse; Malpei F et al.; A pilot plant membrane bioreactor has been tested in parallel with a full-scale activated sludge wastewater treatment plant fed on the wastewater from a textile factory . The possibility to upgrade the final effluent for internal reuse was investigated . The pilot and full-scale plants are located in a textile factory (Boselli & C., Olgiate Comasco, North Italy) which manufactures and finishes polyester fabric . The activated sludge wastewater treatment plant (WWTP) is an extended aeration system . The MBR pilot plant is a ZW-10 bench hollow fibre module (membrane surface area: 0.93 m2) submerged in a 200 L tank . Performance and operation of the membrane bioreactor (MBR) were evaluated in terms of permeate characteristics and variability (COD, colour, total N and P, microbiological counts), of membrane specific flux (l m(-2) h(-1) bar(-1)) and other operational parameters (sludge growth and yield).

Lett Appl Microbiol, 2003, 37(2), 100 - 4
A quantitative method for measuring the mass concentration of the filamentous bacterium Type 021N in activated sludge using fluorescence in situ hybridization; Guan Y et al.; AIMS: This study aimed to develop a quantitative method for measuring mass concentrations of Type 021N, a bacterium causing bulking in activated sludge . METHODS AND RESULTS: Fluorescence in situ hybridization was used to determine the relationship between the concentration ratio of the mass of the bacterium Type 021N to mass of activated sludge, and the proportion of fluorescence area imparted by probe G123T specific for Type 021N to that obtained with probe EUB338 for bacteria . A linear relationship existed between the cube root of the mass concentration ratio and square root of this area proportion . CONCLUSIONS: A standard curve was obtained for quantifying Type 021N in activated sludge . SIGNIFICANCE AND IMPACT OF THE STUDY: This method may allow the determination of growth rate constant of filamentous bacteria in activated sludge, information that will help in understanding their ecology.

FEMS Microbiol Lett, 2003 Jul 15, 224(1), 23 - 8
Intergeneric coaggregations among Oligotropha carboxidovorans and Acinetobacter species present in activated sludge; Malik A et al.; The coaggregation traits of two pairs of sewage sludge bacteria were tested and characterized . Oligotropha carboxidovorans S23 coaggregated with two strains of the genus Acinetobacter viz . Acinetobacter junii S33 (56%) and Acinetobacter johnsonii S35 (99%) . Coaggregates of O . carboxidovorans S23 and A . junii S33 were small (20-40 microm), weak and susceptible to EDTA and a commercial protease (Actinase E) . Actinase/periodate pretreatment of the partners prior to coaggregation revealed that interaction in this case was mediated by protein surface components . Coaggregates of O . carboxidovorans S23 and A . johnsonii S35 were large (above 100 microm), strong and not deflocculated by EDTA or Actinase E . Only periodate pretreatment of A . johnsonii S35 prevented this coaggregation indicating a role for a carbohydrate-containing moiety without the involvement of protein components . The potential mechanisms and strength of bacterial coaggregations seem to be pair dependent.

Environ Sci Pollut Res Int, 2003, 10(3), 177 - 82
Effect of arsenic and mercury speciation on inhibition of respiration rate in activated sludge systems; Stasinakis AS et al.; The inhibition effect of arsenite, As(III), arsenate, As(V), inorganic mercury, Hg(II) and methylmercury, MeHg, on the respiration rate of activated heterotrophic sludge microorganisms was evaluated . As(III) and MeHg were much more toxic to activated sludge than As(V) and Hg(II) respectively . The effect of various experimental parameters on the toxicity, such as sludge age, concentration of suspended solids and exposure time, was investigated . An increase of sludge age or the concentration of suspended solids reduces the observed inhibition . Longer exposure seems to dramatically increase the inhibition of As(III), MeHg and Hg(II) during the first hours of exposure, while the later inhibition increases at a slower rate . On the contrary, in the presence of As(V), 24 hours after exposure, the respiration rate was similar to that of the control biomass.

Appl Microbiol Biotechnol, 2003 Oct, 62(5-6), 586 - 93 Epub 2003 Jul 04.
Effect of dissolved oxygen concentration on sludge settleability; Martins AM et al.; This laboratory study presents a detailed evaluation of the effects of dissolved oxygen concentration and accumulation of storage polymers on sludge settleability in activated sludge systems with an aerobic selector . The oxygen and substrate availability regime were simulated in laboratory sequencing batch reactor systems . The experiments showed that low dissolved oxygen concentration (< or =1.1 mg O2 l(-1)) had a strong negative effect on sludge settleability, leading to the proliferation of filamentous bacteria (Thiothrix spp., Type 021N and Type 1851) . This negative effect was stronger at high chemical oxygen demand loading rate . This indicates that a compartmentalised (plug flow) aerobic contact tank, designed at short hydraulic residence time to guarantee a strong substrate gradient, with low dissolved oxygen concentration, might be worse for sludge settleability than an "overdesigned" completely mixed contact tank . Contrary to the general hypothesis, the maximum specific acetate uptake rate, poly-beta-hydroxybutyrate production rate, and resistance to short starvation periods are similar in both poor- and well-settling sludge . The results of this study support our previous hypothesis on the importance of substrate gradients for the development of filamentous structures in biological flocs, from soluble organic substrate gradients to dissolved oxygen gradients in sludge flocs.

Water Environ Res, 2003 May-Jun, 75(3), 273 - 80
Modeling nonsteady-state conditions and kinetics of mass transport for hydrophobic compounds in activated-sludge treatment; Rittmann BE et al.; A new model that describes the fate of hydrophobic and volatile organic compounds in activated-sludge treatment includes two novel features . First, all of the mass balances are nonsteady state, which allows the model to describe the effects of transients in loading, temperature, or operation . Second, the model describes the mass transfer of hydrophobic compounds with kinetics, not equilibrium . A series of examples demonstrate the new features of the model and how they can be important . When the kinetics of mass transfer are not fast, hydrophobic compounds remain significantly out of equilibrium, even when the system is operating at steady state . When the loading of a hydrophobic compound increases, its aqueous-phase concentration approaches (but does not quite reach) its steady-state concentration much more rapidly than does the density of the adsorbed hydrophobic compound . Finally, the importance of mass-transport kinetics between the aqueous and sorbed phases suggests that research should be focused on this poorly understood mechanism in activated sludge.

Water Environ Res, 2003 May-Jun, 75(3), 254 - 62
Controlling biosolids phosphorus content in enhanced biological phosphorus removal reactors; Chaparro SK et al.; A methodology to reduce the phosphorus content of biosolids produced by enhanced biological phosphorus removal treatment plants was studied . The process consists of mixing phosphate-rich waste activated sludge (WAS) with either primary sludge or the supernatant from a primary-sludge gravity thickener under anaerobic conditions to induce the release of phosphate from WAS . The solubilized phosphate could then be chemically sequestered and removed from the biosolids . Bench-scale phosphate release experiments were conducted with sludge from the Nine Springs Wastewater Treatment Plant (Madison, Wisconsin) at different mixing ratios . A WAS/primary sludge or WAS/supernatant mixing ratio of 1:1 (by volume) resulted in the highest phosphate release in the batch tests . For experiments with less than 50% WAS (by volume), the total phosphate release was directly proportional to the amount of WAS added . When the mixture contained more than 50% WAS, total phosphate release was limited by the volatile fatty acids (VFAs) available . For the Nine Springs plant optimal biosolids phosphorus could be achieved using a primary sludge/WAS mixing ratio of 1.02 kg volatile suspended solids (VSS)/kg VSS or a supernatant VFA/WAS mixing ratio of 0.028 kg VFA/kg VSS . The expected reduction in phosphorus content would be 35 and 32% if primary sludge or supernatant, respectively, were used.

Water Environ Res, 2003 May-Jun, 75(3), 216 - 24
The effect of an initial anaerobic zone on the nutrient requirements of activated sludge; Harper WF Jr et al.; Laboratory-scale sequencing batch reactors (SBRs) operating on an acetate and casamino acids-based synthetic wastewater were used to determine the phosphorus and nitrogen requirements of anaerobic-aerobic (AnA) and completely aerobic (CA) activated sludge . At a 4-day mean cell residence time, AnA activated sludge had an approximately 20% lower phosphorus requirement than CA activated sludge . The difference between the "end-of-aerobic-cycle" polyhydroxyalkanoate (PHA) and carbohydrate contents of the sludges indicated that the AnA activated sludge used more influent carbon than the CA activated sludge for synthesis of non-phosphorus-containing storage products . Nitrogen requirement experiments showed that nitrogen limitations caused significant increases in the PHA and carbohydrate content of both the AnA and CA SBRs, and the limiting nitrogen requirements of AnA activated sludge were similar to those of the CA activated sludge . These findings are part of an evaluation of the AnA process for treating nutrient-deficient wastewaters in plants with stringent effluent nutrient requirements.

Bioresour Technol, 2003 Oct, 90(1), 71 - 4
Heavy metal biosorption by biomass of Ochrobactrum anthropi producing exopolysaccharide in activated sludge; Ozdemir G et al.; The removal of chromium, cadmium and copper, toxic metals of high environmental priority due to their toxicity, from dilute aqueous solutions has been studied in the present work, applying a dead exopolysaccharide producing bacterium, Ochrobactrum anthropi, isolated from activated sludge . Particularly, the effect of pH, metal concentration and the effects of contact time were considered . Optimum adsorption pH values of chromium(VI), cadmium(II) and copper(II) were 2.0, 8.0 and 3.0 respectively . Experimental results also showed the influence of initial metal concentration on the metal uptake for dried biomass . Both the Freundlich and Langmuir adsorption models were suitable for describing the short-term biosorption of chromium(VI), cadmium(II) and copper(II) by O . anthropi.

Water Res, 2003 Aug, 37(14), 3508 - 16
Nickel sorption by acclimatized activated sludge culture; Arican B et al.; The sorption of Ni(2+) by acclimatized activated sludge treating Ni(2+) bearing wastewater was investigated using a once-through completely mixed tank reactor . The culture developed from sewage was acclimatized to 85.2 microM/l Ni(2+) influent concentration by stepwise increases, at a low dilution rate 0.11/h . Acclimation was found to enhance the sorptive capacity of the activated sludge . In fact, at all of the intermediate concentrations, percentage Ni(2+) adsorbed by the biomass and also the sorptive capacity of the activated sludge drastically increased with an increase in the influent Ni(2+) concentration . All influent Ni(2+) concentrations were found to significantly stimulate the observed biomass yield of the culture over that observed in the base line . Experimental findings obtained at two other dilution rates; namely, 0.25/h and 0.45/h revealed that dilution rate is a significant operational parameter affecting the Ni(2+) sorption characteristics of acclimatized activated sludge microorganisms . Considerable complexation of nickel and organic and inorganic ligands in the wastewater appeared to be responsible for a relatively lower Ni(2+) sorption capacity.

Water Res, 2003 Aug, 37(14), 3327 - 34
Test for assessing shear sensitivity of activated sludge flocs: a feasibility study; Seka MA et al.; Sludge deflocculation can cause, like excessive growth of filamentous bacteria, activated sludge wastewater treatment failure . Yet, unlike the latter cause, there exists no widely accepted tool to assess the flocculation level of activated sludge and to predict sludge deflocculation . In this study, a test procedure is proposed to assess the sensitivity of activated sludge flocs to shear . The test consists in subjecting sludge sample to a shear treatment followed by a sludge volume measurement (SV(30)), with reference to a control . The ratio (%) obtained by dividing the SV(30) of the sheared sample by the SV(30) of the control is used to express the shear sensitivity . In a first series of experiments using two types of sludge, the test was shown to be able of ranging sludge samples in a correct order of shear sensitivity . Applying this so-called shear-SV test procedure to a series of sludge samples allowed to distinguish amorphous sludges (SV(30) ratio> or =100%) from normal sludges (SV(30) ratio<100%) . The test was shown to be repeatable and simple . It requires only basic laboratory equipment and implies minimum cost . It can be used as framework for the assessment of activated sludge shear sensitivity in practice.

Water Sci Technol, 2003, 47(9), 117 - 21
Adhesion and releasing of Poliovirus to activated sludge of wastewater purifying plants; Nakajima M et al.; Pathogenic enteric viruses are released from infected persons through domestic wastewater to the environment . From that point of view, the knowledge of the viral behavior in wastewater purifying process is important: it is, however, still poorly understood . In this study, we reported the adhesion of Poliovirus to activated sludge samples taken from wastewater purifying plants by using a model system . More than 10(6) particles adhered to one gram (wet) of activated sludge, and the adhered viral particles maintained infectivity for longer period of time and showed higher thermo-resistant than the free viral particles . The adhered viral particles were released by increase of salt concentration or alkaline pH buffer as infectious particles . The data suggest that pathogenic viruses could be enriched and maintain the infectivity in the activated sludge, and released to environments under certain conditions.

Water Sci Technol, 2003, 47(9), 109 - 16
The behavior of estrogenic substances in the biological treatment process of sewage; Onda K et al.; A study was conducted for about one year on the fate and behavior of estrogens, namely 17beta-estradiol (E2), estrone (E1), and estriol (E3) in an activated sludge process of a pilot scale plant supplied with domestic sewage . A simultaneous analytical method for these three substances using LC-MS/MS was developed and applied to sewage samples . The average removal of E2 was 94.7%, while that of E3 was 96.9% . In contrast, the average removal of E1 was relatively low at 69.2% with a maximum concentration of 55.4 ng/L detected in the treated water . The theoretical values of estrogenic activity calculated from the concentrations of each natural estrogen in treated water were found to correlate with the values of estrogenic activity measured by a yeast estrogen screening assay . The effect of E2 on estrogenic activity in influent was found to be high, while that of E1 in treated water was considerably higher . In batch treatment tests on E2, E2 turned into E1 immediately after being charged . After three hours of aeration, the values of both E1 and E2 were around threshold limits . It was determined from this that E1 and E2 were substances that could be degraded by biological treatment . As the removal of E2 was found to be sufficiently high at times, optimization of operational conditions based on E1 removal should be important for reducing estrogenic activity in treated water.

Water Sci Technol, 2003, 47(9), 45 - 9
Control of Cryptosporidium with wastewater treatment to prevent its proliferation in the water cycle; Suwa M et al.; The outbreak of Cryptosporidiosis in 1996 in Japan is thought to have been enlarged by the proliferation of Cryptosporidium in the water cycle from wastewater to drinking water through the river system . From this experience, the wastewater system must have functions to remove Cryptosporidium oocysts effectively . Efficiencies of wastewater treatment processes to remove oocysts were investigated using pilot plants receiving municipal wastewater . An activated sludge process and a following sand filter showed removal efficiencies of 2 log and 0.5 log, respectively . Poly-aluminium chloride dosage improved the efficiencies by 3 log for the activated sludge process and by 2 log for the sand filter . Chemical precipitation of raw wastewater with poly-aluminium chloride could achieve 1 to 3 log removal according on the coagulant concentration.

FEMS Microbiol Lett, 2003 Jun 27, 223(2), 185 - 91
Use of acetate for enrichment of electrochemically active microorganisms and their 16S rDNA analyses; Lee J et al.; A fuel cell-type electrochemical device has been used to enrich microbes oxidizing acetate with concomitant electricity generation without using an electron mediator from activated sludge . The device generated a stable current of around 5 mA with complete oxidation of 5 mM acetate at the hydraulic retention time of 2.5 h after 4 weeks of enrichment . Over 70% of electrons available from acetate oxidation was recovered as current . Carbon monoxide or hydrogen did not influence acetate oxidation or current generation from the microbial fuel cell (MFC) . Denaturing gradient gel electrophoresis showed that DNA extracted from the acetate-enriched MFC had different 16S rDNA patterns from those of sludge or glucose+glutamate-enriched MFCs . Nearly complete 16S rDNA sequence analyses showed that diverse bacteria were enriched in the MFC fed with acetate . Electron microscopic observations showed biofilm developed on the electrode, but not microbial clumps observed in MFCs fed with complex fuel such as glucose and wastewater from a corn-processing factory.

Appl Microbiol Biotechnol, 2003 Oct, 62(5-6), 594 - 600 Epub 2003 Jun 24.
Bacterial diversity in an industrial wastewater bioreactor; Bramucci M et al.; Industrial wastewater bioreactors are potentially important sources of novel biocatalysts . However, the microbial populations in these bioreactors are not well characterized . The microbial community in an industrial wastewater bioreactor was surveyed by extracting DNA from a sample of activated sludge, followed by PCR amplification and sequencing of cloned 16S rRNA genes . A total of 407 cloned 16S rRNA gene sequences were compared with 88 bacterial isolates cultured from the same sample of sludge using a variety of standard media . Most of the bacteria detected by the PCR-based approach were beta-subdivision Proteobacteria, whereas most of the cultured bacteria were gamma-subdivision Proteobacteria . Only a few types of bacteria were detected by both approaches . These observations indicate that multiple techniques are necessary to characterize the microbial diversity in any complex ecosystem.

Ann Chim, 2003 Apr, 93(4), 337 - 46
Enrichment from activated sludges of aerobic mixed cultures capable to degrade vinyl chloride (VC) as the sole carbon source; Aulenta F et al.; Two microbial cultures able to degrade high concentrations of VC as the sole carbon source have been obtained by enrichment from activated sludge . The cultures began consuming VC (0.02 mmol l(-1)) only after a long initial acclimation period (1-2 months) . After then the concentration of VC was gradually increased (from 0.02 to 0.8 mmol l(-1)) and the cultures were able to maintain VC degrading ability for long time (over 500 days) . VC-degrading biomass in the two cultures was characterized by low specific maximum growth rates (0.19-0.21 d(-1)) compared to heterotrophic organisms typically present in activated sludge processes . Monod half-saturation constant was rather low (0.7-1.6 mg VC l(-1)) indicating that it is possible to effectively remove VC to low residual concentrations . The cultures were highly sensitive to even short periods of VC lack (with quick decrease of VC degradation rates) whereas they were not to sudden load increases (up to 3.4 mmol l(-1)) . After being cultured with only ethene as the sole carbon and energy source, the cultures kept the ability of degrading VC . Possibility of maintaining the mixed cultures on non-toxic ethene, without loosing VC degradation ability, is very promising for bioaugmentation treatments.

Biodegradation, 2003, 14(1), 31 - 40
Improving the biotreatment of hydrocarbons-contaminated soils by addition of activated sludge taken from the wastewater treatment facilities of an oil refinery; Juteau P et al.; Addition of activated sludge taken from the wastewater treatment facilities of an oil refinery to a soil contaminated with oily sludge stimulated hydrocarbon biodegradation in microcosms, bioreactors and biopile . Microcosms containing 50 g of soil to which 0.07% (w/w) of activated sludge was added presented a higher degradation of alkanes (80% vs 24%) and polycyclic aromatic hydrocarbons (PAHs) (77% vs 49%) as compared to the one receiving only water, after 30 days of incubation at room temperature . Addition of ammonium nitrate or sterile sludge filtrate instead of activated sludge resulted in a similar removal of PAHs but not of alkanes suggesting that the nitrogen contained in the activated sludge plays a major role in the degradation of PAHs while microorganisms of the sludge are active against alkanes . Addition of sludge also stimulated hydrocarbon biodegradation in 10-kg bioreactors operated during 60 days and in a 50-m3 biopile operated during 126 days . This biopile treatment allowed the use of the soil for industrial purpose based on provincial regulation ("C" criteria) . In contrast, the soil of the control biopile that received only water still exceeded C criteria for C10-C50 hydrocarbons, total PAHs, chrysene and benzo{a}anthracene . The stimulation effect of sludge was stronger on the 4-rings than on 2-rings PAHs . The soil of the biopile that received sludge was 4-5 times less toxic than the control . These results suggest that this particular type of activated sludge could be used to increase the efficiency of the treatment of hydrocarbon-contaminated soils in a biopile.

Huan Jing Ke Xue, 2003 Mar, 24(2), 97 - 101
{Biodegradable plastic production by activated sludge with different carbon sources}; Lin D et al.; Polyhydroxyalkanoates(PHAs) are polyesters synthesized by numerous bacteria in sludge as intracellular carbon and energy storage compounds under the condition of unbalance growth . Another important aspect of PHAs is thermoplastic polyester with the remarkable characteristics of biodegradability . In this paper, using sodium acetate, sodium propionate and sodium butyrate as the unique carbon source, 5.58%, 3.90% and 4.98% PHAs of dry sludge weight were obtained by assimilated sludge as PHAs synthesis strains in the anaerobic condition, and 12.32%, 9.55% and 11.35% PHAs of dry sludge weight were obtained in the anaerobic condition . It was shown that there were large quantities strains which could accumulate PHAs as granules in the cytoplasm of cells, and the yield of PHAs in the anaerobic process were higher than that in the aerobic process . The best result was that 12.32% PHAs of dry sludge weight was obtained in the best experiment condition, and the yield of the PHAs to substrate was 30.65% . The structures of PHAs were analyzed by 1HNMR spectrum, and the relationship of the structure of PHAs and the carbon source was explained.

Ann N Y Acad Sci, 2003 Mar, 984, 53 - 64
Membrane technologies applied to textile wastewater treatment; Marcucci M et al.; This paper describes the experimental results of a pilot-scale application of membrane technologies to textile wastewater advanced treatment, downstream of a biological activated sludge process, aimed at water reuse in textile technology processes . The chosen approach consisted of sand filtration as a pretreatment, a microfiltration (MF) or ultrafiltration (UF) membrane process, and a final separation treatment performed by means of a nanofiltration (NF) or a reverse osmosis (RO) membrane . An experimental study to compare spiral wound membranes, operating under pressure, to flat membranes, operating under vacuum was conducted . The technical results and a preliminary economic analysis indicate the possibility of technological transfer of the membrane technologies to an industrial scale for textile wastewater reclamation.

Chemosphere, 2003 Aug, 52(6), 1059 - 67
Chromium species behaviour in the activated sludge process; Stasinakis AS et al.; The purpose of this research was to compare trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)) removal by activated sludge and to investigate whether Cr(VI) reduction and/or Cr(III) oxidation occurs in a wastewater treatment system . Chromium removal by sludge harvested from sequencing batch reactors, determined by a series of batch experiments, generally followed a Freundlich isotherm model . Almost 90% of Cr(III) was adsorbed on the suspended solids while the rest was precipitated at pH 7.0 . On the contrary, removal of Cr(VI) was minor and did not exceed 15% in all experiments under the same conditions . Increase of sludge age reduces Cr(III) removal, possibly because of Cr(III) sorption on slime polymers . Moreover, the decrease of suspended solids concentration and the acclimatization of biomass to Cr(VI) reduced the removal efficiency of Cr(III) . Batch experiments showed that Cr(III) cannot be oxidized to Cr(VI) by activated sludge . On the contrary, Cr(VI) reduction is possible and is affected mainly by the initial concentration of organic substrate, which acts as electron donor for Cr(VI) reduction . Initial organic substrate concentration equal to or higher than 1000 mgl(-1) chemical oxygen demand permitted the nearly complete reduction of 5 mgl(-1) Cr(VI) in a 24-h batch experiment . Moreover, higher Cr(VI) reduction rates were obtained with higher Cr(VI) initial concentrations, expressed in mg Cr(VI) g(-1) VSS, while decrease of suspended solids concentration enhanced the specific Cr(VI) reduction rate.

Water Environ Res, 2003 Mar-Apr, 75(2), 126 - 37
Relative efficacy of intrinsic and extant parameters for modeling biodegradation of synthetic organic compounds in activated sludge: steady-state systems; Magbanua BS Jr et al.; The performance of intrinsic and extant kinetic parameters as predictors of synthetic organic compound (SOC) concentration in biotreatment systems operated at steady state was evaluated . Two laboratory-scale, completely mixed activated-sludge systems were sampled on a routine basis, and SOC concentrations were quantified using gas chromatography with flame-ionization detection coupled with solid-phase microextraction for analyte concentration . At the same time, intrinsic and extant respirometric tests were performed periodically, and the kinetic parameter estimates obtained were used to predict effluent SOC concentrations for comparison with the measured values . Out of 28 comparisons that could be made between intrinsic and extant predictions, extant parameters were superior in 27 cases and intrinsic parameters were comparable, at best, to extant parameters in the remaining case . Given their superior performance and relative ease of measurement, extant parameters are preferable for use in design and operational decision-making.

Water Res, 2003 Jul, 37(12), 2944 - 52
The characteristics of the bacterial community structure and population dynamics for phosphorus removal in SBR activated sludge processes; Lin CK et al.; The characteristics of the bacterial community structure and population dynamics for phosphorus removal in activated sludge were investigated using laboratory-scale sequencing batch reactor (SBR) activated sludge processes fed with four different carbon sources . Phosphorus removal activity, quinone profile of the activated sludge and isolated bacterial strains were monitored . An enhanced phosphorus removal activity was accompanied by the increase in ubiquinone-9 (Q-9) . The relationships between phosphorus removal activity and Q-9 contents of the isolated bacterial strains were dependent neither on the organic substrates nor on the species of isolated bacterial strains . The enhanced phosphorus removal capability of activated sludge seemed to be due to the increase in the populations of bacteria with activity of phosphorus removal, i.e . species succession of bacteria in activated sludge ecosystems, rather than the increase in the phosphorus removal capability of phosphorus removal bacteria . Not only Acinetobacter but also Pseudomonas identified from isolated strains were regarded as representative polyphosphates-accumulating organisms and predominant species to the whole of bacterial population in activated sludge for phosphorus removal.

Water Res, 2003 Jul, 37(12), 2813 - 20
Removal of resin acids and sterols from pulp mill effluents by activated sludge treatment; Kostamo A et al.; The wastewater treatment plant of an elemental chlorine free bleaching kraft pulp mill located in eastern Finland was sampled in order to study the fate of wood extractives and the toxicity to luminescence bacteria (Vibrio fischeri) in different parts of the plant . Resin acids and sterols were analyzed from water, particles and sludge samples during three different runs . Waters before biotreatment and primary sludge were found to be toxic; but in the activated sludge treatment toxicity was removed . During wastewater treatment, concentrations of wood extractives were reduced over 97% . In activated sludge treatment, over 94% of the resin acids and over 41% of the sterols were degraded or transformed to other compounds . Furthermore, in general, less than 5% of the resin acids and over 31% of the sterols were removed in biosludge to the sludge thickener . Most of the extractives were discharged attached to particles . Although some disturbing factors increased the load of wood extractives during samplings, these factors did not affect the operational efficiency of the secondary treatment system.

Environ Technol, 2003 Apr, 24(4), 429 - 34
Development of flexible fibre biofilm reactor for treatment of food processing wastewater; Yu Q et al.; Biological treatment methods are usually effective and commonly used in the treatment of organic wastewater . However, there are a number of problems for conventional biological treatment methods in treating wastewater from industries such as food processing . For example, microorganisms in the aeration tank in an activated sludge process cannot survive a continuous series of shock loads and the process could become operationally unstable . The associated problem of sludge bulking often occurs when the organic loading to the treatment process is high . In this paper, a new flexible fibre biofilm reactor was developed for the treatment of wastewater from fruit and vegetable processing plants . Experiments were carried out to evaluate the performance of the treatment process . Acclimatisation characteristics of the treatment process were also evaluated . The removal efficiencies for COD and BOD5 for different influent organic strengths evaluated . Results indicated that over 90% COD removal and 95% BOD5 removal could be achieved . The performance parameters were also compared with a conventional activated sludge process under similar conditions, operated in parallel . It was found that the biofilm reactor exhibited a number of advantages over the conventional reactor . These include (a) high organic loading rate, (b) long sludge retention times and low sludge discharge rate in the settling tank (about 10%), (c) elimination of the sludge recycle stream, and (d) no sludge bulking problem at high organic loading rates . Therefore, the flexible fibre biofilm reactor can provide a more efficient and cost effective treatment for wastewater from food processing industries.

Water Res, 2003 Jun, 37(11), 2784 - 8
Biofilm in the sediment phase of a sanitary gravity sewer; Chen GH et al.; Microbial activity of the sediment phase in a 1.5-km-long concrete sewer section with a cement pipe in a 540-mm diameter was investigated in this paper . SEM examinations and elementary composition analyses of the sediment samples have identified the presence of a biofilm layer at the sediment surface . Bacterial counting results with a DNA-staining technique have revealed that the amount of bacteria in this layer was 2.1 x 10(11)cellg(-1) dry wt, which is close to that of activated sludge . ATP content in the sewer biofilm was found relatively high, demonstrating that the sewer biofilm is active . Throughout the entire 1.5-km sewer section, the biofilm activity was maintained at almost the same level . Lab-scale sediment oxygen uptake flux (SOUF) tests showed that the shear flow velocity above the sediment phase linearly increases the SOUF, which of the potential value was determined to be 32gO(2)m(-2) day(-1) at an estimated shear flow velocity of 0.055ms(-1) at 25 degrees C in the sewer line, provided that the mean flow velocity was 1.5ms(-1), and the mean water depth was 220mm . Such a high SOUF value further endorsed the existence of the active sewer biofilm.

Water Res, 2003 Jun, 37(11), 2764 - 72
Effect of periodic feeding in sequencing batch reactor on substrate uptake and storage rates by a pure culture of Amaricoccus kaplicensis; Aulenta F et al.; A pure culture of Amaricoccus kaplicensis was aerobically cultured at a long culture residence time (Theta(C)>12d), under periodic acetate feeding in a sequencing batch reactor (SBR) . The cycle length and, correspondingly, the volumetric organic load rate (vOLR) were varied in the range 4-24h and 0.76-0.12gCODl(-1)d(-1), respectively . The transient response of the microorganism to the acetate spike was investigated throughout batch tests, as a function of SBR cycle length and vOLR . In all tested conditions, a rapid transient response was observed, mainly due to acetate storage in the form of polyhydroxybutyrate, since growth (production of active biomass) played a minor role . Apart from this general trend, the maximum rates under transient conditions increased as the cycle length increased from 4 to 24h . In the SBR, the longest cycle also caused a decrease in floc size and settleability as well as an increase in the observed yield . The observed effect of SBR operating conditions on the physiological state of cells and their related transient response may have great significance on the performance of full scale activated sludge processes.

Water Res, 2003 Jun, 37(11), 2636 - 44
Bulking in activated sludge plants treating paper mill wastewaters; Thompson G et al.; As part of a larger project to examine the causes of bulking in activated sludge plants treating wastewaters from paper mills, two laboratory-scale activated sludge plants were run in parallel . This was to evaluate the impact of variable environmental and operational parameters on the sludge ecology, and in particular, on the filamentous bacteria in the sludge . A survey of paper mills in the UK showed that there was a significant difference between the activated sludge plants at the paper mills using virgin fibre and those using recycled fibre . An examination of samples from activated sludge plants at the paper mills showed that there did not appear to be any significant correlation between filament abundance and the settlement characteristics as measured by stirred specific volume index (SSVI) . The surface charge carried by the sludge particles was also measured and it was found that this parameter was better related to the SSVI . Similar results were found for samples from the laboratory plants . Seven different sets of operational conditions were applied to the laboratory-scale plants . These were aimed at simulating the conditions noted for the full-scale plants during the mill survey . The effects of low dissolved oxygen and low organic loading rates were examined . The effect of inorganic sulphur compounds and volatile fatty acids was studied . A change in raw material from virgin fibre to recycled fibre (corrugated paper) caused an immediate and continuous deterioration in settlement . Divalent cations, calcium and magnesium, were found to be successful in controlling settlement in the final clarifier.

Water Res, 2003 Jun, 37(11), 2555 - 70
Effect of feeding pattern and storage on the sludge settleability under aerobic conditions; Martins AM et al.; The selection of filamentous bacteria is often assumed to be associated with specific microbial properties such as growth rate, substrate uptake rate, substrate affinity and potential for substrate storage . In this study we aimed to verify some of these factors . Sequencing batch reactor (SBR) systems were used to scale-down aerobic activated sludge systems with an aerobic selector . Adding acetate in different aerobic feeding periods allowed us to simulate a variable relative size of aerobic selector with different bulk liquid substrate concentrations . The experiments showed that as expected, the aerobic fill time ratio (FTR(ox)) and the corresponding feast period, which can be assumed similar to contact time in an aerobic selector, had a strong effect on the sludge settleability . Promoting a strong substrate gradient in the SBR (FTR(ox)<5.4%) resulted in good sludge settleability (SVI<120mLg(-1)) . Whenever acetate was added in a limiting rate (FTR(ox)>6.2%), a condition in which the acetate concentration in the reactor was always very low, the sludge settleability decreased (SVI>150mLg(-1)) . Sludge settleability could be improved by changing the feeding strategy to a pulse feed . The maximum specific acetate uptake rate and poly beta-hydroxybutyrate (PHB) production rate of bad settling sludge, including bulking sludge, was similar to well-settling sludge, which is not in accordance with the general assumptions that well settling sludge have a higher maximal substrate uptake rate and better storage capacities . An alternative hypothesis for the development of filamentous structures in biological flocs has been formulated . It is hypothesized that bulking sludge originates from the presence of substrate gradients in sludge aggregates . Whereas at low bulk liquid substrate concentration filamentous bacteria give easier access to the substrate at the outside of the flocs and thereby proliferate, at high bulk liquid substrate concentration there is no substrate advantage for filamentous organisms and smooth bacterial structures predominate . In this hypothesis there is no need for an intrinsic difference in kinetic parameters between floc and filamentous bacteria . Where presence of filamentous bacteria is related to process conditions, the presence of a specific filament is likely due to presence of a specific limiting substrate.

Bioresour Technol, 2003 Mar, 87(1), 27 - 33
Biosorption of Pb(II) and Cu(II) by activated sludge in batch and continuous-flow stirred reactors; Sag Y et al.; Biosorption of Pb(II) and Cu(II) ions in single component and binary systems was studied using activated sludge in batch and continuous-flow stirred reactors . In biosorption experiments, the activated sludge in three different phases of the growth period was used: growing cells; resting cells; dead or dried cells . Because of the low adsorption capacity of the non-viable activated sludge especially in the case of Pb(II) ions, biosorption of the Cu(II) and Pb(II) ions from the binary mixtures was carried out by using the resting cells . The biosorption data fitted better with the Freundlich adsorption isotherm model . Using a mathematical model based on continuous system mass balance for the liquid phase and batch system mass balance for the solid phase, the forward rate constants for biosorption of Pb(II) and Cu(II) ions were 0.793 and 0.242 1 (mmolmin)(-1), respectively.

Chemosphere, 2003 Jul, 52(1), 221 - 9
A new method to study biodegradation kinetics of organic trace pollutants by activated sludge; Temmink H et al.; A reliable prediction of the behaviour of organic trace compounds in activated sludge plants requires an accurate input of the biodegradation kinetics . Often these kinetics are extrapolated from the results of standardised biodegradation tests . However, these tests generally are not designed to yield kinetic information and do not reflect the conditions in activated sludge plants . To overcome these problems a new test method was developed which is referred to as a 'by-pass' test . The test methodology is explained and examples are given for three compounds: the C(12)-homologue of linear alkylbenzene sulfonate, nitrilotriacetic acid and toluene . More experience with the test is required, particularly with respect to selection of the proper test settings, which are compound related . The test is a suitable tool in a research environment, for example to investigate the effect of plant operational parameters on the biodegradation kinetics.

Chemosphere, 2003 Jul, 52(1), 143 - 9
Evaluation and further development of the activated sludge respiration inhibition test; Gendig C et al.; The activated sludge respiration inhibition test is an important bacterial test system for the determination of bacterial toxicity of chemical compounds . The exposure period recommended by OECD 209 and ISO 8192 protocols is 30 and 180 min . A modified version of the test was developed which allowed a prolonged incubation period of 27 h to enhance the possibilities of the test system . The test system with the prolonged incubation time was evaluated by the recommended reference compound 3.5-dichlorophenol and showed an EC50 of 6.3 mgl(-1) with a coefficient of variation of 12.7% . Furthermore, the use of an open test system was evaluated showing a comparable toxicity but a higher coefficient of variation than the closed test system . A storage of activated sludge for several days accompanied by a daily feed with OECD nutrient solution should be avoided, for it can cause a decreased sensitivity of the inoculum . Different statistical fit procedures were tested indicating that Weibull fit procedures were superior for extended data sets covering a wide range of concentrations whereas Gamma and Probit fits were appropriate for smaller data sets mainly restricted to the linear part of the dose response curve.

Water Res, 2003 May, 37(10), 2458 - 66
Applications and limitations of the colloid titration method for measuring activated sludge surface charges; Mikkelsen LH; Surface charge quantification of polymer solutions and sludge suspensions were investigated by the colloid titration technique and compared to charge densities obtained by pH-titration . The colloid titration technique worked well for polymer samples . The charge quantity of humic acid and activated sludge extracellular polymers (EPS) was estimated to be -1.51 and -0.42 meq/g, respectively . These values are reasonable when compared to pH-titration results . The surface charge of activated sludge particles appears to be below the limit of detection . However, surface charge estimates are obtained, when the reactant doses and sample concentration are increased . It is suggested that such estimates are not correct, but artefacts of the non-stoichiometric precipitation of the polymeric reactants at high doses . It appears that the colloid titration method is limited to conditions of low reactant doses and valid for charge determination of extracted sludge polymers, whereas the method is not valid for charge determination of whole sludge.

Water Res, 2003 May, 37(10), 2388 - 93
Activated sludge exopolymers: separation and identification using size exclusion chromatography and infrared micro-spectroscopy; Gorner T et al.; Extracellular polymeric substances were extracted from activated sludge using a resin exchange method and analyzed . The separation and identification of EPS were carried out by size exclusion chromatography and Fourier transform infrared micro-spectroscopy . Chromatograms of extracted EPS exhibited seven peaks . Proteins varying in molecular weights from 670 to 45 kDa were present in all the peaks . Polysaccharides corresponding to molecular weights of approximately 1 and approximately 0.5 kDa were present in only three peaks . Strong association of polysaccharides and proteins was observed . Infrared results revealed the presence of one type of polysaccharide and two types of proteins (A and B) . Proteins differed mainly in the length of their associated alkyl chains and in the ratio of ester/acidic functionalities.

Water Res, 2003 May, 37(10), 2377 - 87
A knowledge-based approach to the deflocculation problem: integrating on-line, off-line, and heuristic information; Comas J et al.; A knowledge-based approach for the supervision of the deflocculation problem in activated sludge processes was considered and successfully applied to a full-scale plant . To do that, a methodology that integrates on-line, off-line and heuristic information has been proposed . This methodology consists of three steps: (i) . development of a decision tree (which involves knowledge acquisition and representation); (ii) . implementation into a rule-based system; and (iii) . validation . The set of symptoms most useful in diagnosing the deflocculation problem has been identified, the different branches to diagnose pin-point floc and dispersed growth have been built (using generic and specific knowledge), and all this knowledge has been codified into an object-oriented shell . The results obtained in the application of this knowledge-based approach to the Granollers WWTP (which treats about 130000 inhabitants-equivalents) showed that the system was able to identify correctly the problem with reasonable accuracy . Our positive experience building this system suggests that this approach is a practical and valuable element to include in an intelligent supervisory system combining numerical and reasoning techniques.

Water Res, 2003 May, 37(10), 2301 - 10
Biosorption of humic and fulvic acids to live activated sludge biomass; Esparza-Soto M et al.; Biosorption of high molecular weight humic substances (HS) to activated sludge (AS) biomass may be considered as a preliminary step previous to enzymatic hydrolysis breakdown and biological uptake . Two standard HS, Suwannee River humic and fulvic acids, were biosorbed onto live AS biomass collected from full-scale wastewater treatment plants . Biosorption isotherms were corrected for interference from organic matter desorbed from AS biomass . The effect of pH, calcium and ionic strength on biosorption was tested . HS biosorption to live AS biomass obeyed the Freundlich isotherm equation . Biosorption increased with decreasing pH, increasing calcium and ionic strength concentration . Higher biosorption at low pH may be attributed to hydrophobic interactions between HS and AS biomass extracellular polymers (EPS) . Hydrophobic and cationic bridging effects between HS and AS EPS were the mechanisms responsible for biosorption under the presence of divalent cations; however, the former was most significant at low pH, whereas the latter was predominant near neutral pH . The effect of ionic strength on HS biosorption followed the colloidal chemistry theory as the electric double layer became compressed when the ionic strength increased, resulting in closer approach of HS and AS biomass . The humic acid fraction of Suwannee River was removed more efficiently than its fulvic acid fraction because the humic acid was more hydrophobic . These results showed that pH, divalent cation concentration and ionic strength play an important role in the fate and removal of influent wastewater HS in full-scale treatment plants.

Appl Biochem Biotechnol, 2003 Spring, 105 -108, 581 - 91
Biosorption and desorption of copper (II) ions by Bacillus sp; Lo W et al.; Batch biosorption experiments were conducted to investigate the removal of Cu2+ ions from aqueous solutions by a series of bacterial strains isolated from a local activated sludge process . The characteristics of 12 isolates were identified and examined for their ability to bind Cu2+ ions from aqueous solution . Among the isolates, two species exhibited biosorption capacity >40 mg of Cu/g of dry cell . Isotherms for the biosorption of copper on bacterial cells were developed and compared, and the equilibrium data fitted well to the Langmuir and Freundlich isotherm models . The biosorption of copper increased significantly with increasing pH from 2.0 to 6.0 regardless of the species . More than 90% of copper sorbed on the cells of Bacillus sp . could be recovered by washing with 0.1 M HNO3 for 5 min . The performance of two different desorption processes was also tested and compared . The results show that five biosorption and desorption cycles are a better operation process than five successive biosorptions followed by one desorption to remove and recover copper from aqueous solution . The biosorbent could be used for at least five biosorptions and desorption cycles without loss of copper removal capacity . It can be concluded that the activated sludge or sludge-isolated bacteria could be a potential biosorbent for copper removal.

Appl Biochem Biotechnol, 2003 Spring, 105 -108, 567 - 79
Single-stage anaerobic codigestion for mixture wastes of simulated Korean food waste and waste activated sludge; Heo NH et al.; Korean food waste was treated with a single-stage anaerobic codigester (SSAD) using waste activated sludge (WAS) generated from a municipal wastewater treatment plant . The stability and performance of the system was analyzed . The C/N ratio was improved with increasing food waste fraction of feed mixture . The pH, alkalinity, and free ammonia nitrogen concentration were the parameters used to evaluate the digester's stability . The experimentally determined values of the parameters indicated that there were no methane inhibitions in the digester . Digester performance was determined by measuring the total chemical oxygen demand TCOD), volate solids (VS) removal, methane content in biogas, methane production rate (MPR), and specific methane productivity . Methane content in biogas and MPR were significantly dependent on hydraulic retention time (HRT) and ratio of food waste to WAS . The methane content in biogas decreased at shorter HRT or higher organic loading rate (OLR) with increased food waste fraction . Concerning the performance of the codigester, the optimum operating condition of the SSAD was found to be at an HRT of 10 d with a feed mixture ratio of 50% food waste and 50% WAS . A TCOD removal efficiency of 53.6% and a VS removal efficiency of 53.7% were obtained at an OLR of 5.96 kg of TCOD/(m3 d) and 3.14 kg of VS/(m3 d), respectively . A maximum MPR of 1.15 m3 CH4/(m3 d) and an SMP of 0.37 m3 CH4/kg of VSfeed were obtained at an HRT of 10 d with a methane content of 63%.

Biodegradation, 2002, 13(6), 401 - 10
Removal of molecular weight fractions of COD and phenolic compounds in an integrated treatment of olive oil mill effluents; Beccari M et al.; Previous works (Beccari et al . 1999b; Beccari et al . 2001a; Beccari et al . 2001b) on the anaerobic treatment of olive oil mill effluents (OME) have shown: (a) a pre-treatment based on the addition of Ca(OH)2 and bentonite was able to remove lipids (i.e . the most inhibiting substances present in OME) almost quantitatively; (b) the mixture OME-Ca(OH)2-bentonite, fed to a methanogenic reactor without providing an intermediate phase separation, gave way to high biogas production even at very low dilution ratios; (c) the effluent from the methanogenic reactor still contained significant concentrations of residual phenolic compounds (i.e . the most biorecalcitrant substances present in OME) . Consequently, this paper was aimed at evaluating the fate of the phenolic fractions with different molecular weights during the sequence of operations (adsorption on bentonite, methanogenic digestion, activated sludge post-treatment) . The results show that a very high percentage (above 80%) of the phenolic fraction below 500 D is removed by the methanogenic process whereas the phenolic fractions above 1,000 D are significantly adsorbed on bentonite; the 8-day activated sludge post-treatment allows an additional removal of about 40% of total filtered phenolic compounds . The complete sequence of treatments was able to remove more than the 96% of the phenolic fraction below 500 D (i.e . the most toxic fraction towards plant germination) . Preliminary respirometric tests show low level of inhibition exerted by the effluent from the methanogenic reactor on aerobic activated sludges taken from full-scale municipal wastewater plants.

Acta Microbiol Pol, 2002, 51(4), 367 - 78
A comparison of biodegradation of phenol and homologous compounds by Pseudomonas vesicularis and Staphylococcus sciuri strains; Mrozik A et al.; Pseudomonas vesicularis and Staphylococcus sciuri were isolated as dominant strains from phenol-acclimated activated sludge . P . vesicularis was an efficient degrader of phenol, catechol, p-cresol, sodium benzoate and sodium salicylate in a single substrate system . Under similar conditions S . sciuri degraded only phenol and catechol from among aromatic compounds that were tested . Cell-free extracts of P . vesicularis grown on phenol (376 mg l(-1)), sodium benzoate (576 mg l(-1)) and sodium salicylate (640 mg l(-1)) showed catechol 2,3-dioxygenase activity initiating an extradiol (meta) splitting pathway . The degradative intradiol (ortho) pathway as a result of catechol 1,2-dioxygenase synthesis was induced in P . vesicularis cells grown on catechol (440 mg l(-1)) orp-cresol (432 mg l(-1)) . Catechol 1,2-dioxygenase and the ortho-cleavage has been also reported in S . sciuri cells capable of degrading phenol (376 mg l(-1)) or catechol (440 mg l(-1)) . In cell-free extracts of S . sciuri no meta-cleavage enzyme activity was detected . These results demonstrated that gram-positive S . sciuri strain was able to effectively metabolize some phenols as do many bacteria of the genus Pseudomonas but have a different capacity for degrading of these compounds.

Huan Jing Ke Xue, 2003 Jan, 24(1), 75 - 9
{Effects of phenol presence on the biodegradation of 2,4-dichlorophenol in a bioaugmented system}; Quan X et al.; Special culture for 2,4-Dichlorophenol(2,4-DCP) degradation were supplemented to an activated sludge system and the effects of the presence of phenol at various concentration on the removal of 2,4-DCP were studied . In addition, the changes of the removal rate of 2,4-DCP and phenol under the long existence of phenol was investigated in semicontinuous test . Results show than the presence of phenol at the concentration of 10 mg/L, 50 mg/L, 100 mg/L and 300 mg/L inhibit the biodegradation of 2,4-DCP and the inhibition increased with increasing of phenol concentration . 2, 4-DCP biodegradation rate declined with the run of semi-continuous test, while the biodegradation rate of phenol was much faster than the first run.

Int J Hyg Environ Health, 2003 Mar, 206(2), 117 - 22
Parasite contamination (helminth eggs) in sludge treatment plants: definition of a sampling strategy; Gaspard PG et al.; The use of sludge in agriculture must be carried out according to many guidelines, especially regarding a precise knowledge of the pathogenic microorganisms it contains . The control of the produced sludge requires a sampling strategy that is representative of the contamination present in the sludge . Thus, we evaluated the distribution of helminth eggs in sludge to determine how to sample and at what frequency . Two plants were studied, firstly we studied sludge that was undergoing biological treatment (anaerobic digestion, prolonged aeration), secondly we evaluated the dehydration step (centrifugation and filter press) . The helminth egg concentrations were measured over short periods (between 5 minutes and 7 hours) and for periods of over 24 hours (7 to 28 days) . The results showed that there was much homogeneity in periods of less than 7 hours, thus it was advisable to take grab samples . An appropriate sample weight was 30 g dry matter, because this allowed an analysis in triplicate when testing treatment processes according to standards of France, (less than 3 viable eggs/10 g dry matter) . Determination of the egg concentration in the plants during periods of over 24 hours showed that the parasite flow was stable . In some cases, large variations were due to the treatment processes (storage or thickening, mixing of different sludges) . These results have been confirmed with the study of 6 other plants during a one year period . Thus, the recommended sampling frequency can be limited to every 3 to 6 months, by adapting the sampling methods to the characteristics of the plant.

Ecotoxicol Environ Saf, 2003 May, 55(1), 126 - 37
Genotoxic and hepatic biotransformation responses induced by the overflow of pulp mill and secondary-treated effluents on Anguilla anguilla L; Maria VL et al.; Pulp and paper mill effluent compounds pollute the aquatic environment and are responsible for increased biochemical alterations and genotoxicity in aquatic organisms such as fish . Adult eels (Anguilla anguilla L) were exposed during 8, 16, 24, and 72 h to the following conditions: (1) aerated, filtered, and dechlorinated tap water (C); (2) 2.5% (v/v) sewage water previously treated with activated sludge (T); (3) bleached kraft pulp and paper mill effluent collected at the river Vouga, close to an ancient sewage outlet (Portucel), diluted in tap water {25% (E25) and 50% (E50)}; and (4) bleached kraft pulp and paper mill effluent sediment {water-soluble fraction (S)} . Liver biotransformation induced by the above conditions was measured as ethoxyresorufin-O-deethylase (EROD), cytochrome P450 (P450) (Phase I), and glutathione-S-transferase (GST) (Phase II) . Genotoxicity was also determined as blood/liver DNA strand breaks and erythrocytic nuclear abnormalities (ENA) induced on European eel (A . anguilla L) . Liver EROD activity was significantly increased in eels at 8 and 16 h exposure to E25, as well as at 16, 24, and 72 h exposure to E50 . S exposure induced liver EROD activity only at 24h . A significant decrease in liver P450 was observed at 72 h exposure to T, whereas a significant P450 increase at 16 h was followed by a significant decrease at 24h exposure to E25 . Another P450 significant increase was noticed at 72 h exposure to S . Liver GST activity (Phase II) demonstrated a significant increase at 72 h exposure to E50 and to S . A significant decrease in blood DNA integrity was observed at 72 h exposure to T and at 24 and 72 h to S . Blood DNA integrity significantly decreased at 16 and 24 h exposure to E25, as well as at 8, 16, and 24 h exposure to E50 . Liver DNA integrity significantly decreased at 72 h exposure to T and at 16 h exposure to S . Moreover, liver DNA integrity was significantly decreased at 24h exposure to E25 and E50, and 72 h to E50 . A . anguilla L . increased ENA frequency was detected in T at 16, 24, and 72 h, whereas in E25 and S it was observed at 8, 16, and 24 h . Furthermore, E50 ENA frequency increased at 24 h exposure.

Environ Technol, 2003 Mar, 24(3), 339 - 48
Withstanding shock loads in activated sludge treatment by pre-exposure to low H2S concentrations; Burgess JE et al.; An activated sludge pilot plant was used to acclimatise sludge to a low dose of H2S gas . Sludge samples from different types of treatment works were compared with acclimatised and unaclimatised sludges using batch absorption tests . The effects of sludge source and acclimatisation on the ability of the sludge to withstand shock loads of 50 ml l(-1) H2S were evaluated . Sludge that had been acclimatised to 5 ml l(-1) H2S in the air supply removed 70% of a 50 ml l(-1) load in a batch reactor after three sludge ages of acclimatisation . Pre-exposure to low H2S concentrations enabled the bacterial community to maintain a sufficient sulphide-degrading population to retain acclimatisation and degrade subsequent high loads which are toxic to unacclimatised sludge . Acclimatisation to H2S is therefore mainly an effect of selection pressure on the mixed bacterial population, which suggests that the H2S removal capacity of different types of activated sludge will converge after acclimatisation, irrespective of their initial degradative abilities.

FEMS Microbiol Rev, 2003 Apr, 27(1), 99 - 127
The microbiology of biological phosphorus removal in activated sludge systems; Seviour RJ et al.; Activated sludge systems are designed and operated globally to remove phosphorus microbiologically, a process called enhanced biological phosphorus removal (EBPR) . Yet little is still known about the ecology of EBPR processes, the microbes involved, their functions there and the possible reasons why they often perform unreliably . The application of rRNA-based methods to analyze EBPR community structure has changed dramatically our understanding of the microbial populations responsible for EBPR, but many substantial gaps in our knowledge of the population dynamics of EBPR and its underlying mechanisms remain . This review critically examines what we once thought we knew about the microbial ecology of EBPR, what we think we now know, and what still needs to be elucidated before these processes can be operated and controlled more reliably than is currently possible . It looks at the history of EBPR, the currently available biochemical models, the structure of the microbial communities found in EBPR systems, possible identities of the bacteria responsible, and the evidence why these systems might operate suboptimally . The review stresses the need to extend what have been predominantly laboratory-based studies to full-scale operating plants . It aims to encourage microbiologists and process engineers to collaborate more closely and to bring an interdisciplinary approach to bear on this complex ecosystem.

Water Res, 2003 Apr, 37(8), 1921 - 31
Important operational parameters of membrane bioreactor-sludge disintegration (MBR-SD) system for zero excess sludge production; Yoon SH; In order to prevent excess sludge production during wastewater treatment, a membrane bioreactor-sludge disintegration (MBR-SD) system has been introduced, where the disintegrated sludge is recycled to the bioreactor as a feed solution . In this study, a mathematical model was developed by incorporating a sludge disintegration term into the conventional activated sludge model and the relationships among the operational parameters were investigated . A new definition of F/M ratio for the MBR-SD system was suggested to evaluate the actual organic loading rate . The actual F/M ratio was expected to be much higher than the apparent F/M ratio in MBR-SD . The kinetic parameters concerning the biodegradability of organics hardly affect the system performance . Instead, sludge solubilization ratio (alpha) in the SD process and particulate hydrolysis rate constant (k(h)) in biological reaction determine the sludge disintegration number (SDN), which is related with the overall economics of the MBR-SD system . Under reasonable alpha and k(h) values, SDN would range between 3 and 5 which means the amount of sludge required to be disintegrated would be 3-5 times higher for preventing a particular amount of sludge production . Finally, normalized sludge disintegration rate (q/V) which is needed to maintain a certain level of MLSS in the MBR-SD system was calculated as a function of F/V ratio.

Water Res, 2003 Apr, 37(8), 1831 - 51
Linearization of the activated sludge model ASM1 for fast and reliable predictions; Smets IY et al.; In this paper a strategy is proposed to reduce the complexity of the activated sludge model no . 1 (ASM1) which describes the biotransformation processes in a common activated sludge process with N-removal . The key feature of the obtained reduced model is that it combines high predictive value (all state variables keep their biological interpretation) with very low computation time . Therefore, this model is a valuable tool in a risk assessment environment (designed for the evaluation of wastewater treatment plants facing stricter effluent norms) as well as in on-line (MPC) control strategies . The complexity reduction procedure consists of four steps . In the first step representative input/output data sets are generated by simulating the full ASM1 model . In the second step the ASM1 model is rewritten in state space format with linear approximations of the nonlinear (kinetic) terms . In the third step the unknown parameters in the linear terms are identified based on the generated input/output data . To reduce the amount of parameter sets that have to be identified (to cover the full operation range of the plant), a Multi-Model interpolation procedure is introduced as a last step.

Chemosphere, 2003 Jun, 51(9), 825 - 33
The effect of pre-ozonation on the biocompatibility of reactive dye hydrolysates; Arslan-Alaton I; Pre-ozonation of 14 different reactive dyestuff hydrolysates at alkaline pH was investigated to assess possible relationships between ozone transfer efficiency, first order decolourization kinetics, release of initially complexed heavy metals and relative changes in the biodegradability of the partially oxidized dye waste samples . Biocompatibility of the raw (untreated) and ozonated dye hydrolysates was comparatively tracked through specific oxygen uptake rate measurements from which the respirometric inhibition of biological activated sludge imparted by raw and ozonated reactive dye wastewater with respect to synthetic domestic wastewater was determined . It could be demonstrated that preliminary ozonation of reactive azo dyes increases their biological compatibility more significantly than formazan copper complex, copper complex azo and phythalocyanine dyes as a consequence of heavy metal release associated with the cleavage of associated chromophoric groupings right at the initial stages of pre-ozonation.

Water Res, 2003 May, 37(9), 2195 - 205
Microbial communities in activated sludge performing enhanced biological phosphorus removal in a sequencing batch reactor; Jeon CO et al.; Microbial communities of activated sludge in an anaerobic/aerobic sequencing batch reactor (SBR) supplied with acetate as sole carbon source were analyzed to identify the microorganisms responsible for enhanced biological phosphorus removal . Various analytical methods were used such as electron microscopy, quinone, slot hybridization, and 16S rRNA gene sequencing analyses . Electron photomicrographs showed that coccus-shaped microorganisms of about 1 microm diameter dominated the microbial communities of the activated sludge in the SBR, which had been operated for more than 18 months . These microorganisms contained polyphosphate granules and glycogen inclusions, which suggests that they are a type of phosphorus-accumulating organism . Quinones, slot hybridization, and 16S rRNA sequencing analyses showed that the members of the Proteobacteria beta subclass were the most abundant species and were affiliated with the Rhodocyclus-like group . Phylogenetic analysis revealed that the two dominating clones of the beta subclass were closely related to the Rhodocyclus-like group . It was concluded that the coccus-shaped organisms related to the Rhodocyclus-like group within the Proteobacteria beta subclass were the most dominant species believed responsible for biological phosphorus removal in SBR operation with acetate.

Water Res, 2003 May, 37(9), 2162 - 72
Assessment of activated sludge microbial community analysis in full-scale biological wastewater treatment plants using patterns of fatty acid isopropyl esters (FAPEs); Werker AG et al.; This investigation introduces the application of a relatively rapid technique to obtain information about the dynamic nature of microbial communities in activated sludge . The objective has been to consider variability due to measurement errors and protocol changes within the same quantitative framework as the analysis of systematic differences in microbial communities in large-scale aerobic activated sludge secondary wastewater treatment systems . Adjustments to the methodology were considered due to their potential for simplifying and shortening the analysis procedure . All modifications to the protocols used to assay the composition of microbial fatty acids (MFAs) of activated sludge imposed some bias to the chromatographic data . This methodological bias was similar in magnitude to the level of discrimination between activated sludge microbial community structures that were considered as part of the present study . MFA analysis supported the expectations of subtle but systematic community structure differences and shifts in activated sludge based on the current understanding of these wastewater treatment systems . A standardized MFA methodology was shown to be sensitive to minor systematic changes in activated sludge communities due the anticipated underlying factors of selective pressures from the process configuration, history, operational conditions and/or nutrient status . The chemometric approach of fatty acid isopropyl ester analysis of activated sludge can provide a routine tool for meaningful and quantitative information of changes in activated sludge quality in full-scale treatment systems.

Water Res, 2003 May, 37(9), 2127 - 39
The influence of key chemical constituents in activated sludge on surface and flocculating properties; Wilen BM et al.; This paper examines the influence of the chemical constituents of activated sludge and extracted extracellular polymeric substances (EPS) on the surface properties, hydrophobicity, surface charge (SC) and flocculating ability (FA) of activated sludge flocs . Activated sludge samples from 7 different full-scale wastewater treatment plants were examined . Protein and humic substances were found to be the dominant polymeric compounds in the activated sludges and the extracted EPS, and they significantly affected the FA and surface properties, hydrophobicity and SC, of the sludge flocs . The polymeric compounds proteins, humic substances and carbohydrates in the sludge flocs and the extracted EPS contributed to the negative SC, but correlated negatively to the hydrophobicity of sludge flocs . The quantity of protein and carbohydrate within the sludge and the extracted EPS was correlated positively to the FA of the sludge flocs, while increased amounts of humic substances resulted in lower FA . In contrast, increased amounts of total extracted EPS had a negative correlation to FA . The results reveal that the quality and quantity of the polymeric compounds within the sludge flocs is more informative, with respect to understanding the mechanisms involved in flocculation, than if only the extracted EPS are considered . This is an important finding as it indicates that extracting EPS may be insufficient to characterise the EPS . This is due to the low extraction efficiency and difficulties involved in the separation of EPS from other organic compounds . Correlations were observed between the surface properties and FA of the sludge flocs . This confirms that the surface properties of the sludge flocs play an important role in the bioflocculation process but that also other interactions like polymer entanglement are important.

Water Res, 2003 May, 37(9), 2097 - 105
Modeling of chlorine effect on floc forming and filamentous micro-organisms of activated sludges; Caravelli A et al.; Chlorination is the most economical, non-specific method to control the excessive growth of filamentous micro-organisms causing bulking in activated sludge systems in the treatment of food industrial wastewaters; it was one of the first methods used to control filamentous bulking and is still widely employed . Considering that chlorination affects both floc-forming and filamentous micro-organisms and leaves undesirable disinfection by-products, it is necessary to define the adequate doses to control bulking, minimizing the effect on floc-forming bacteria.In the present work the effect of biomass concentration and type of micro-organism on chlorine decay kinetics was evaluated; the inactivation of either a filamentous (Sphaerotilus natans) or a floc-forming (Acinetobacter anitratus) micro-organism due to chlorination was also analyzed.For chlorine decay assays, the samples were treated in a batch system with sodium hypochlorite ranging between 9.8 and 56.6 mg Cl(2) (gVSS)(-1) . Respirometric assays were used to evaluate the effect of chlorine on micro-organisms respiratory activity; in these cases, sodium hypochlorite doses ranged between 2.5 and 18 mgCl(2) (gVSS)(-1).A model that allowed to predict simultaneously chlorine consumption and respiratory activity decay for both micro-organisms as a function of time was proposed . The model includes three coupled differential equations corresponding to respiratory inhibition, readily organic matter oxidation by chlorine and chlorine decay . The rate of chlorine decay depended on both, type and concentration of the micro-organisms in the system . Chlorine consumption rate due to S . natans was 2-4 times faster than A . anitratus . Using the proposed model initial critical chlorine doses (the lowest initial dose that leads to a total inhibition of the respiratory activity) were calculated for both micro-organisms and values of 11.9 mgCl(2) (gVSS)(-1) for S . natans and 4.5 mgCl(2) (gVSS)(-1) for A . anitratus were obtained . These critical doses indicated that in non flocculated pure cultures, floc-former bacteria A . anitratus was more susceptible to chlorine action than S . natans.

Water Res, 2003 May, 37(9), 2043 - 52
Characterization of activated sludge flocs by confocal laser scanning microscopy and image analysis; Schmid M et al.; In this study we present a new approach to determine volumes, heterogeneity factors, and compositions of the bacterial population of activated sludge flocs by 3D confocal imaging . After staining the fresh flocs with fluorescein-isothiocyanate, 75 stacks of images (containing approx . 3000 flocs) were acquired with a confocal laser scanning microscope . The self-developed macro 3D volume and surface determination for the KS 400 software package combined the images of one stack to a 3D image and calculated the real floc volume and surface . We determined heterogeneity factors like the ratio of real floc surface to the surface of a sphere with the respective volume and the fractal dimension (D(f)) . According to their significant influence on floc integrity and quality, we also investigated the chemical composition of flocs and quantified their bacterial population structure by using group-specific rRNA-targeted probes for fluorescence in situ hybridization . By a settling experiment we enriched flocs with poor settling properties and determined the above-mentioned parameters . This approach revealed shifts in floc volume, heterogeneity, and bacterial and chemical composition according to the settling quality of the flocs.

Water Res, 2003 May, 37(9), 2013 - 8
Effect of extended idle conditions on structure and activity of granular activated sludge; Zhu J et al.; In industry and in tourist areas, periods exist during which no or only very little sewage is produced, and the wastewater treatment facilities have to be set into an idle phase over several days and even weeks . When wastewater is generated again and delivered to the treatment plant, the microorganisms in the activated sludge plant may have lost activity, and the activated sludge flocs may have disintegrated . From previous observation, it is assumed that granular activated sludge is more resistant against long-term storage than activated sludge flocs . Experiments using a laboratory-scale sequencing batch reactor (SBR) were conducted to study the impacts of a 7-weeks anaerobic idle time on structural integrity and metabolic activity of granular activated sludge, and the time required to regain the former operational status of the plant . Oxygen consumption rate (OCR) was used as an indicator to evaluate the metabolic activity of the sludge . The results revealed that the size, color and sedimentation characteristics of the granular sludge did hardly change during the storage period . Sludge activity, however, dropped to values as low as 0.17 mg min(-1)L(-1) . After restarting the reactor, the OCR increased within 1 day to a level of 0.57 mg min(-1)L(-1), kept rising at a linear rate in the following days, and reached after 1 week, a value of 5.74 mg min(-1)L(-1) typical for the former activity status . These results imply that granular activated sludge can be stored for a considerably long period of time, and brought into service again relatively quickly . After an idle period of 7 weeks, it took less than a week to regain full capacity of the SBR.

Water Res, 2003 May, 37(9), 1991 - 2000
Impact of the repetition of oxygen deficiencies on the filamentous bacteria proliferation in activated sludge; Gaval G et al.; Cases of low stress can frequently occur in a wastewater treatment plant (WWTP) . As they have no visible impact on the plant operation, they generally go unnoticed . Nevertheless, it would appear that an accumulation of such cases can result in serious operational problems . The impact of the repeated application of oxygen deficiency on the proliferation of the filamentous bacteria Sphaerotilus natans, Haliscomenobacter hydrossis, Eikelboom type 021N and Thiothrix spp has been studied on WWTP pilots . Two different oxygen deficiencies series were tested . Filamentous bacteria evolution in activated sludge was monitored using fluorescent in situ hybridization . For the weak deficiencies, no significant variation in the filamentous bacteria response level was recorded, whereas with more severe deficiencies the filamentous bacteria response increased considerably with the increase in stress number . From the results obtained, it would appear that there is an intensity and frequency threshold beyond which the filamentous bacteria response levels increase when the stress is applied in series . This "oxygen deficiencies repetition" appears to be an important factor in the appearance of bulking.

Water Environ Res, 2003 Jan-Feb, 75(1), 83 - 91
Making classifying selectors work for foam elimination in the activated-sludge process; Parker D et al.; Classifying selectors are used to control the population of foam-causing organisms in activated-sludge plants to prevent the development of nuisance foams . The term, classifying selector, refers to the physical mechanism by which these organisms are selected against; foam-causing organisms are enriched into the solids in the foam and their rapid removal controls their population at low levels in the mixed liquor . Foam-causing organisms are wasted "first" rather than accumulating on the surface of tanks and thereby being wasted "last", which is typical of the process . This concept originated in South Africa, where pilot studies showed that placement of a flotation tank for foam removal prior to secondary clarifiers would eliminate foam-causing organisms . It was later simplified in the United States by using the aeration in aeration tanks or aerated channels coupled with simple baffling and adjustable weirs to make continuous separation of nuisance organisms from the mixed liquor.

Water Environ Res, 2003 Jan-Feb, 75(1), 21 - 9
The use of a genetically engineered Pseudomonas species (Shk1) as a bioluminescent reporter for heavy metal toxicity screening in wastewater treatment plant influent; Ren S et al.; Heavy metals are known to be inhibitory and toxic to the activated-sludge microbial community in biological wastewater treatment plants . Toxicity screening of aqueous mixtures of these heavy metal ions in plant influent could use both chemical and biological methods . As a biological method, luminescent bacterial bioreporters offer the advantages of a simple test procedure and rapid response . Current biologically based methods for screening aqueous streams for toxicity are labor-intensive, inaccurate, or difficult to use in continuous monitoring applications . In the present study, a system was developed that is simple and easily automated . This system is based on the bacterium Shk1, a genetically engineered bioluminescent Pseudomonad whose parent strain was originally isolated from activated sludge . Compared with other bioluminescence-based systems (specifically, the Microtox assay), the system of the present study more accurately reflects the effects of the toxicity of common metal ions on activated-sludge respirometry without being overly sensitive to typical constituents of wastewater . The use of Shk1 as a bioluminescent reporter for heavy metal toxicity testing for the application of wastewater treatment influent toxicity screening is presented in this study.

Bioresour Technol, 2003 Aug, 89(1), 75 - 9
Agar-plated bacteria found in the activated sludge of lab-scale SBR and CFSTR systems; Juang DF et al.; We identified and compared the predominant agar-plated bacteria in the activated sludge of two popular wastewater treatment systems, the sequencing batch reactor (SBR) and the continuous-flow stirred tank reactor (CFSTR) . All tests had the same feed composition except for the buffer intensity . It was found that Corynebacterium sp . seemed to prefer growing under lower buffer condition, and Arthrobacter sp . grew dominantly in the system with higher buffer intensity . Gram-negative bacteria appeared more sensitive to an environment with unstable organic loading, such as in the SBR system . On the contrary, the SBR system was more selective to the Gram-positive genera with a special rod-coccus-cycle characteristic, such as Arthrobacter, Corynebacterium, or Brevibacterium.

J Biotechnol, 2003 Apr 10, 102(1), 83 - 92
Producing hydrogen from wastewater sludge by Clostridium bifermentans; Wang CC et al.; Excess wastewater sludge collected from the recycling stream of an activated sludge process is biomass that contains large quantities of polysaccharides and proteins . However, relevant literature indicates that the bio-conversion of wastewater sludge to hydrogen is limited and therefore not economically feasible . This work examined the anaerobic digestion of wastewater sludge using a clostridium strain isolated from the sludge as inoculum . A much higher hydrogen yield than presented in the literature was obtained . Also, the effects of five pre-treatments-ultrasonication, acidification, sterilization, freezing/thawing and adding methanogenic inhibitor-on the production of hydrogen were examined . Freezing and thawing and sterilization increased the specific hydrogen yield by 1.5-2.5 times to that of untreated sludge, while adding an inhibitor and ultrasonication reduced the hydrogen yield.

Chemosphere, 2003 Jun, 51(8), 765 - 73
Odours from pulp mill effluent treatment ponds: the origin of significant levels of geosmin and 2-methylisoborneol (MIB); Watson SB et al.; Pulp and paper mills are well known for their sharp, sulphurous stack emissions, but the secondary treatment units also can be significant contributors to local odour . This study investigated the source(s) of earthy/musty emissions from a mixed hardwood pulp mill in response to a high local odour . Samples from five sites in the mill over five months were analyzed for earthy/musty volatile organic compounds (VOCs), examined microscopically, and plated for bacteria and moulds . In all cases, activated sludge showed substantial geosmin levels and to a lesser extent 2-methylisoborneol (MIB) at 2000-9000 times their odour threshold concentrations (OTCs) . These VOCs were lower or absent upstream and downstream, suggesting that they were produced within the bioreactor . Geosmin and MIB were highest in late summer and declined over winter, and correlated with different operating parameters . Geosmin was most closely coupled with temperature and MIB with nitrogen uptake . Cyanobacteria were present in all sludge samples, but actinomycetes were not found . Gram-negative bacteria and one fungal species isolated from the bioreactor and secondary outfall tested negative for geosmin or MIB . We conclude: (i) geosmin and MIB contribute significantly to airborne odours from this mill, but are diluted below OTC levels at the river; (ii) these VOCs are generated by biota in the activated sludge; and (iii) cyanobacteria are likely primary source(s) . The growth of cyanobacteria in activated sludge represents a loss of energy to the heterotrophic population; thus earthy/musty odours may represent a diagnostic for less than optimal conditions.

Waste Manag Res, 2003 Feb, 21(1), 19 - 28
Strategic environmental assessment of alternative sewage sludge management scenarios; Poulsen TG et al.; Strategic environmental assessment (SEA) of sewage sludge management in a Danish municipality (Aalborg), with 160,000 inhabitants using alternative methods for aggregation of environmental impacts was performed . The purpose is to demonstrate the use of SEA in relation to sludge management and to improve SEA methodology . Six different scenarios for management of sewage sludge within the Aalborg municipality involving thermal treatment, composting and landfilling of sludge were evaluated . Environmental impact categories considered were global warming, non-renewable resources (nutrients and fossil fuels) and land use . Impact categories human health, ecotoxicity and soil quality were excluded as methodology for their assessment is not yet fully developed . Thermal sludge treatment with energy utilisation was shown to be a promising option for sewage sludge management in Aalborg . Sensitivity of the relative environmental impacts with respect to calculation methodology and input parameter values were evaluated to identify important parameters and calculation methods . The analysis showed that aggregation procedures, sludge biogas potential and sludge production were very important whereas sludge transport was not.

Chemosphere, 2003 Jan, 50(3), 283 - 92
Model description of an alternately operated wastewater treatment plant--evaluation of the applicability of SimpleTreat; Fauser P et al.; Alternately operated wastewater treatment plants (WWTPs) are fundamentally different compared to conventional activated sludge WWTPs with respect to flow patterns and aeration in the biological reactors . Several model applications exist for conventional WWTPs, e.g . SimpleTreat, and in this study the effect of substituting a complex discontinuous operation, involving alternating degradation and flow conditions between two reactors, with one single bioreactor with continuos flow (SimpleTreat) has been investigated by setting up two models representing the respective operation schemes . The discontinuous operation induces fluctuations in the outlet concentrations that are not modelled with the single bioreactor model, however, the fluctuations and the associated uncertainties were found to be insignificant compared to the influence of the input parameter uncertainties on the model results . An empirical relationship between an aggregate pseudo-1st order degradation rate for the single bioreactor model and realistic aerobic and anoxic 1st order degradation rates, respectively, has been established . When using this aggregate degradation rate in the single bioreactor model an outlet concentration can be calculated that deviates no more than 2% from the mean outlet concentration from the alternating operation model . For substances with aerobic half-lives longer than approximately 2 h, which is valid for many chemical substances, the aggregate 1st order degradation rate can be set equal to the aerobic 1st order degradation rate.

Chemosphere, 2003 Jan, 50(1), 63 - 9
Biodegradability of biofilm extracellular polymeric substances; Zhang X et al.; This study discovered that biofilm extracellular polymeric substances (EPS) are biodegradable by their own producers and by other microorganisms when they are starved . The study was performed in a comparative fashion to examine the biodegradability of biofilm EPS by the microorganisms from the original biofilm (its own producers) and from activated sludge (other microorganisms) . Four distinctive phases were observed during EPS biodegradation . In the first phase, instantaneous concentration increases of carbohydrate and protein in the test solutions were observed when EPS was added; in the second phase, easily biodegradable EPS from the added EPS was quickly utilized; in the third phase, microorganisms began to produce soluble EPS, using the minimally biodegradable EPS left from the previously added EPS; in the fourth phase, cells consumed the newly produced EPS and microbial activity gradually stopped . This study suggests that EPS can be used as a substrate, and that the EPS carbohydrate can be utilized faster than the EPS protein . The EPS utilization rates (including carbohydrate and protein) in the activated sludge suspension were greater than those in the biofilm suspension . It may take microorganisms longer to get acclimated to a new nutrient environment if they are in a starved state.

Chemosphere, 2003 Jan, 50(1), 1 - 7
Chemically reduced excess sludge production in the activated sludge process; Liu Y; Excess sludge production from wastewater biological treatment process is highly, and the disposal of excess sludge will be forbidden in a near future, thus increased attention has been turned to look into potential technology for sludge reduction . Recently, some novel sludge reduction techniques have been developed based on chemical oxidation and metabolic uncoupling . This paper attempts to review those chemical-assisted sludge reduction processes, including sludge alkaline-thermal treatment, activated sludge-ozonation process, chlorination-combined activated sludge process, sludge reduction by metabolic uncouplers and high dissolved oxygen activated sludge process . In these combined activated sludge processes, excess sludge production can be reduced up to 100% without significant effect on process efficiency and stability . This paper would be useful when one is looking for appropriate environmentally and economically acceptable solutions for reducing or minimizing excess sludge production from wastewater biological treatment process.

Int J Syst Evol Microbiol, 2003 Jan, 53(Pt 1), 253 - 8
Spore-forming Serratia marcescens subsp . sakuensis subsp . nov., isolated from a domestic wastewater treatment tank; Ajithkumar B et al.; A strain (KREDT) that formed endospores and produced the pigment prodigiosin was isolated from activated sludge . The presence of spores in cells of strain KREDT was evident upon electron microscopy examination, heat treatment and the detection of dipicolinic acid in the cells . Biochemical characteristics, and 16S rDNA sequence and DNA-DNA homology data identified strain KREDT as Serratia marcescens . The major respiratory quinone of strain KREDT was found to be ubiquinone Q-8 . The formation of endospores by Gram-negative bacteria has not been observed previously, and has never been reported in any species of Serratia . Here, it is shown that strain KREDT (JCM 11315T = CIP 107489T) represents a novel subspecies of S . marcescens, for which the name Serratia marcescens subsp . sakuensis is proposed.

Environ Technol, 2003 Jan, 24(1), 109 - 14
Activated sludge acclimatisation kinetics to non-ionic surfactants; Carvalho G et al.; The biodegradation of surfactants is a frequent and complex problem in domestic and industrial wastewater treatment processes . In addition to the resulting metabolites being sometimes refractory, the complete biodegradation of many of the most employed non-ionic surfactants requires long hydraulic retention times and the presence of specialised bacterial consortia . Preliminary acclimatisation tests highlighted the importance of the sludge acclimatisation state to a specific surfactant substrate for biotreatment efficiency . This paper reports on studies aimed at quantifying activated sludge acclimatisation and memory retention levels when subjected to changes in the type of surfactant included in the feed . Several transitions were tested, namely from an alkylphenol ethoxylate to a linear alkyl ethoxylate and the reverse, and between alkyl ethoxylates with different hydrophobic and hydrophilic molecular chain lengths . The kinetic results showed that sludge activation and memory loss were more dynamic for primary biodegradation It was found that the sludge was harder to adapt to alkylphenol ethoxylate than to alkyl ethoxylate . The former also apparently introduced an inhibitory effect, resulting in very slow degradation kinetics when imposed to alkyl ethoxylate acclimatised sludge . When replacing an alkyl ethoxylate with another surfactant of the same family, a longer ethoxylate chain reduced the degradation rates . This effect was further enhanced by simultaneously increasing the hydrophobic chain length of the substrate . The acclimatisation kinetic after the replacement of an alkyl ethoxylate by a longer counterpart was slower than the reverse case, and memory was also more easily lost.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2003 Feb, 38(2), 353 - 60
Kinetic responses of activated sludge microorganisms to individual and joint copper and zinc; Lin YM et al.; The individual and joint effects of copper and zinc on the growth kinetics of activated sludge microorganisms were studied in batch reactors fed with glucose as sole carbon source . The observed specific growth rate, substrate utilization rate and removal efficiency were determined at different concentrations of individual and joint Cu and Zn . Activated sludge microorganisms showed different kinetic responses to Cu and Zn, and the Haldane model seemed applicable for the inhibitory effect of Zn, while a first-order kinetics for Cu . Compared to Zn, Cu exhibited high toxicity to activated sludge microorganisms even at a very low concentration of 1.0 mg/dm3 . However, Zn concentrations less than 40 mg/dm3 would stimulate the growth of activated sludge microorganism, and Zn acted as inhibitory chemical only at concentrations above this value . The combined effect of Cu and Zn could be regarded as neither synergistic nor antagonistic action.

Water Sci Technol, 2003, 47(2), 127 - 34
Microelectrode array sensor for water quality monitoring; Gobet J et al.; A versatile microelectrode array sensor for water quality monitoring has been developed . The array fabrication, based on batch microelectronic processes, results in a highly stable passivation of the silicon chip surface and provides the possibility to use a backside contact . Packaging was optimized for on-line water operation at high pressures . Examples of applications include chlorine monitoring in drinking water, ozone monitoring in deionized water, dissolved oxygen in activated sludge and preliminary measurements of trace arsenic.

Water Sci Technol, 2003, 47(2), 103 - 12
Progress in sensor technology--progress in process control? Part 1: sensor property investigation and classification; Rieger L et al.; To ensure correctly operating control systems, the measurement and control equipment in WWTPs must be mutually consistent . The dynamic simulation of activated sludge systems could offer a suitable tool for designing and optimising control strategies . Ideal or simplified sensor models represent a limiting factor for comparability with field applications . More realistic sensor models are therefore required . Two groups of sensor models are proposed on the basis of field and laboratory tests: one for specific sensors and another for a classification of sensor types to be used with the COST simulation benchmark environment . This should lead to a more realistic test environment and allow control engineers to define the requirements of the measuring equipment as a function of the selected strategy.

Water Sci Technol, 2003, 47(2), 1 - 34
On-line monitoring equipment for wastewater treatment processes: state of the art; Vanrolleghem PA et al.; A (non-exhaustive) survey of new and existing technologies for the monitoring of wastewater treatment plants is presented . Emphasis is given to the way these sensors can provide insight in the ongoing (bio-) processes . Three different uses for sensors can be found: for monitoring (operator support), in automatic control systems and as tools for plant auditing/optimization/modelling by consultants . From this, sensors have been classified in two basic types: (i) reliable, simple and low maintenance sensors for day-to-day monitoring and control and (ii) advanced, higher maintenance sensors that are used in auditing, model calibration and optimisation . The paper is organized according to the typical unit processes of biological wastewater treatment systems: anaerobic digestion, activated sludge, nutrient removal and sedimentation . Attention is drawn to a number of practical problems associated with the use of sophisticated sensors in the harsh (dirty) conditions of wastewater treatment processes . The use of autocalibration and built-in sensor checks, cleaning systems and reliable sample preparation units is illustrated . The paper ends with a discussion of the applicability of the different sensors.

J Hazard Mater, 2003 Mar 17, 98(1-3), 91 - 106
Pilot-scale peroxidation (H2O2) of sewage sludge; Neyens E et al.; Municipal and industrial wastewater treatment plants produce large amounts of sludge . This excess sludge is an inevitable drawback inherent to the waste activated sludge process . Both the reduction of the amount of sludge produced and improving its dewaterability are of paramount importance . Novel pre-treatment processes have been developed in order to improve sludge dewatering, handling and disposal . This paper discusses the oxidation process utilising the catalytic activation of H(2)O(2) by iron salts, referred to as Fenton's reagent . In previous work, the authors described the experimental laboratory results of H(2)O(2)-oxidation of thickened sludge . Based upon the optimum conditions obtained in these laboratory tests, pilot-scale experiments are conducted . Peroxidation under its optimum conditions, i.e . (i) through addition of 25 g H(2)O(2) kg(-1) DS (dry solids content), (ii) in the presence of 1.67 g Fe(2+)-ions kg(-1) DS, (iii) at pH 3, and (iv) at ambient temperature and pressure, significantly reduces the amounts of sludge and improves the product quality: the amount DS per equivalent inhabitant per day (DS/IE.d) was reduced from 60 to 33.1 g DS/IE.d and the percentage DS of the sludge cake was 47%, which is high compared with the 20-25% achieved in a traditional sludge dewatering facility . An economic assessment for a wastewater treatment plant of 300,000 IE confirms the benefits . Considering the fixed and variable costs and the savings obtained when the sludge is incinerated after dewatering, a net saving of approx . 950,000 Euro per year or 140 Euro per ton DS can be expected .

J Hazard Mater, 2003 Mar 17, 98(1-3), 51 - 67
A review of thermal sludge pre-treatment processes to improve dewaterability; Neyens E et al.; As a result of the wide application and utilization of the waste activated sludge process, excess sludge presents a serious disposal problem . Many efforts have been devoted to reduce the excess sludge by treatments such as digestion and dewatering . It has been known for many years that a thermal pre-treatment gives an improvement in the dewaterability of sludges . This paper provides a literature review concerning the optimum treatment conditions to obtain enhanced dewaterability and digestibility of sludge . The main commercial hydrolysis processes (Cambi, Porteous and Zimpro) are discussed . The literature findings concerning the optimum treatment conditions of thermal or thermochemical pre-treatments are reviewed . The second part of this paper deals with the fundamentals of improving sludge dewatering . The influence of extracellular polymer (ECP) on settling and dewatering characteristics is discussed, together with the importance of cations and ECP-hydrophobicity in the flocculation and dewatering process . Finally, the effect on exocellular polymer, dewaterability, settleability and colloidal stability of activated sludge by treatment with sulfuric acid was studied .

Biomacromolecules, 2003 Mar-Apr, 4(2), 211 - 5
Enzymatic synthesis and curing of biodegradable epoxide-containing polyesters from renewable resources; Uyama H et al.; Epoxide-containing polyesters were enzymatically synthesized via two routes using unsaturated fatty acids as starting substrate . Lipase catalysis was used for both polycondensation and epoxidation of the unsaturated fatty acid group . One route was synthesis of aliphatic polyesters containing an unsaturated group in the side chain from divinyl sebacate, glycerol, and the unsaturated fatty acids, followed by an epoxidation of the unsaturated fatty acid moiety in the side chain of the resulting polymer . In another route, epoxidized fatty acids were prepared from the unsaturated fatty acids and hydrogen peroxide in the presence of lipase catalyst, and subsequently the epoxidized fatty acids were polymerized with divinyl sebacate and glycerol . The polymer structure was confirmed by NMR and IR, and for both routes, the high epoxidized ratio was achieved . Curing of the resulting polymers proceeded thermally, yielding transparent polymeric films with high gloss surface . Pencil scratch hardness of the present films improved, compared with that of the cured film obtained from the polyester having an unsaturated fatty acid in the side chain . The obtained film showed good biodegradability, evaluated by BOD measurement in an activated sludge.

Waste Manag, 2003, 23(2), 167 - 71
Microbial degradation of pyridine using Pseudomonas sp . and isolation of plasmid responsible for degradation; Mohan SV et al.; Pseudomonas (PI2) capable of degrading pyridine was isolated from the mixed population of the activated sludge unit which was being used for treating complex effluents, the strain was characterized . Aerobic degradation of pyridine was studied with the isolated strain and the growth parameters were evaluated . Pyridine degradation was further conformed by chromatography (HPLC) analysis . The process parameters like biomass growth and dissolved oxygen consumption were monitored during pyridine degradation . In order to conform with the plasmid capability to degrade pyridine, the requisite plasmid was isolated and transferred to DH 5alpha Escherichia coli . The subsequent biodegradation studies revealed the ability of the transformed plasmid capability to degrade the pyridine.

J Environ Monit, 2003 Feb, 5(1), 141 - 4
Identification and quantification of bisphenol A by gas chromatography and mass spectrometry in a lab-scale dual membrane system; Hu JY et al.; Endocrine disruptor contamination is an emerging issue of concern in the field of water quality engineering . In this study, a lab-scale microfiltration (MF) and reverse osmosis (RO) based water reclamation system was set up to monitor and evaluate the removal of bisphenol A (BPA), which is a known oestrogenic compound . The identification and quantification of BPA were performed by using gas chromatography coupled with mass spectrometry . It was noted that the detection method used in this study was able to achieve an average recovery ranging from 88.2 to 94.1% of BPA with standard deviations of less than 10% in different spiked samples . The detection limit of the analytical protocol was determined at 20 ng L(-1) . Based on the analytical protocol, it was noted that a low level of BPA (1.18-3.04 microg L(-1)) could be detected in feed water (effluent of an activated sludge treatment system) to the dual membrane water reclamation system . The results obtained suggested that BPA could be easily chlorinated by sodium hypochlorite with a dosage of 4 to 5 mg L(-1) and a contact time of 1 to 2 min . In this lab-scale study, a satisfactory removal of BPA was readily obtained by RO and BPA was abated to an undetectable level in the product water . It was noted that the RO rejection characteristic of BPA was not sensitive to the variations in raw feed water characteristics experienced in this study . In addition, it was noted that BPA concentration present in raw feed water did not exert any significant impact on RO performance in terms of BPA rejection . The results of this study demonstrated that membrane technology could be effectively used for BPA removal.

Bioresour Technol, 2003 Jul, 88(3), 229 - 39
Impact of iron salts on activated sludge and interaction with nitrite or nitrate; Philips S et al.; Iron salts are often used in activated sludge treatment plants as coagulants or to improve reactor performance . Previous studies have indicated that iron itself has an impact on the activated sludge process . However, the interaction of iron with nitrite or nitrate present in the sludge has received little attention . In this research, the influence of addition of Fe(II) or Fe(III), alone or together with NO(2)(-) or NO(3)(-) on bench-scale activated sludge reactors was examined . Large differences were established between the distinct treatments, regarding reactor performance, sludge characteristics as well as microbial community . Ferric iron was more detrimental than ferrous iron . In some cases, nitrite was found to enhance inhibitory effects of the added iron, whereas nitrate had more a neutralizing effect . It was found that precipitation of phosphate by the iron was not responsible for the observed inhibition . Decrease in pH upon formation of iron hydroxides and the impairment of the floc structure could partially explain the toxicity of the iron dosages . The formation of toxic nitrogen oxides, such as nitric oxide, can also be of importance . The observed positive effect of nitrate on the floc activity is of interest and warrants further elucidation.

Water Res, 2003 Apr, 37(7), 1608 - 18
Analysis of a municipal wastewater treatment plant using a neural network-based pattern analysis; Hong YS et al.; This paper addresses the problem of how to capture the complex relationships that exist between process variables and to diagnose the dynamic behaviour of a municipal wastewater treatment plant (WTP) . Due to the complex biological reaction mechanisms, the highly time-varying, and multivariable aspects of the real WTP, the diagnosis of the WTP are still difficult in practice . The application of intelligent techniques, which can analyse the multi-dimensional process data using a sophisticated visualisation technique, can be useful for analysing and diagnosing the activated-sludge WTP . In this paper, the Kohonen Self-Organising Feature Maps (KSOFM) neural network is applied to analyse the multi-dimensional process data, and to diagnose the inter-relationship of the process variables in a real activated-sludge WTP . By using component planes, some detailed local relationships between the process variables, e.g., responses of the process variables under different operating conditions, as well as the global information is discovered . The operating condition and the inter-relationship among the process variables in the WTP have been diagnosed and extracted by the information obtained from the clustering analysis of the maps . It is concluded that the KSOFM technique provides an effective analysing and diagnosing tool to understand the system behaviour and to extract knowledge contained in multi-dimensional data of a large-scale WTP .

Water Res, 2003 Mar, 37(6), 1288 - 95
Phthalates, nonylphenols and LAS in an alternately operated wastewater treatment plant--fate modelling based on measured concentrations in wastewater and sludge; Fauser P et al.; The performance of an alternately operated activated sludge wastewater treatment plant (WWTP) has been investigated with respect to six phthalates, nonylphenol (NP) and nonylphenol diethoxylate (NPDE) and linear alkylbenzene sulphonates (LAS) . Samples of raw sewage, primary and secondary sludge and treated water were collected during an 8-day period in May 1999 and analysed for dissolved and sorbed substances . To evaluate the system performance with respect to substance removal through biodegradation and sorption to sludge the measured data were applied in a model describing the different bioreactors as one single reactor, corresponding to the concepts of, e.g . SimpleTreat . The most abundant of the investigated phthalates was di-(2-ethylhexyl)-phthalate (DEHP) with a measured mean inlet flow of 240g/day . Two percent of this amount was found in the treated water, 70% was biodegraded and 28% was found in the sludge . For LAS the mean inlet flow was 20,300g/day, of which less than 1% was found in the treated water, 84% was biodegraded and 15% was found in the sludge . The mean inlet flow of NP and NPDE was 44 and 590g/day, of which 4% and 2% was found in the treated water, 80% was biodegraded for both substances, and 16% and 18% was found in the sludge, respectively . The WWTP removal of the investigated substances was thus high compared to other studies of conventional activated sludge WWTPs . The simple model set-up presents a strong tool for predicting substance removal and system sensitivity related to changes in the inlet conditions, such as concentrations and flow . Furthermore, it allows the inclusion of complex alternately operated WWTPs in risk assessment tools such as e.g . SimpleTreat.

Water Res, 2003 Mar, 37(6), 1199 - 212
Evolutionary self-organising modelling of a municipal wastewater treatment plant; Hong YS et al.; Building predictive models for highly time varying and complex multivariable aspects of the wastewater treatment plant is important both for understanding the dynamics of this complex system, and in the development of optimal control support and management schemes.This paper presents a new approach, which is called genetic programming as a self-organising modelling tool, to model dynamic performance of municipal activated-sludge wastewater treatment plants . Genetic programming evolves several process models automatically based on methods of natural selection ('survival of the fittest'), that could predict the dynamics of MLSS and suspended solids in the effluent.The predictive accuracy of the genetic programming approach was compared with a nonlinear state-space model with neural network and a well-known IAWQ ASM2 . The genetic programming system evolved some models that were an improvement over the neural network and ASM2 and showed that the transparency of the model evolved may allow inferences about underlying processes to be made . This work demonstrates that dynamic nonlinear processes in the wastewater treatment plant may be successfully modelled through the use of evolutionary model induction algorithms in GP technique . Further, our results show that genetic programming can work as a cost-effective intelligent modelling tool, enabling us to create prototype process models quickly and inexpensively instead of an engineer developing the process model.

Mol Genet Genomics, 2003 Feb, 268(5), 570 - 84 Epub 2003 Jan 10.
The 79,370-bp conjugative plasmid pB4 consists of an IncP-1beta backbone loaded with a chromate resistance transposon, the strA-strB streptomycin resistance gene pair, the oxacillinase gene bla(NPS-1), and a tripartite antibiotic efflux system of the resistance-nodulation-division family; Tauch A et al.; Plasmid pB4 is a conjugative antibiotic resistance plasmid, originally isolated from a microbial community growing in activated sludge, by means of an exogenous isolation method with Pseudomonas sp . B13 as recipient . We have determined the complete nucleotide sequence of pB4 . The plasmid is 79,370 bp long and contains at least 81 complete coding regions . A suite of coding regions predicted to be involved in plasmid replication, plasmid maintenance, and conjugative transfer revealed significant similarity to the IncP-1beta backbone of R751 . Four resistance gene regions comprising mobile genetic elements are inserted in the IncP-1beta backbone of pB4 . The modular 'gene load' of pB4 includes (1) the novel transposon Tn 5719 containing genes characteristic of chromate resistance determinants, (2) the transposon Tn 5393c carrying the widespread streptomycin resistance gene pair strA-strB, (3) the beta-lactam antibiotic resistance gene bla(NPS-1) flanked by highly conserved sequences characteristic of integrons, and (4) a tripartite antibiotic resistance determinant comprising an efflux protein of the resistance-nodulation-division (RND) family, a periplasmic membrane fusion protein (MFP), and an outer membrane factor (OMF) . The components of the RND-MFP-OMF efflux system showed the highest similarity to the products of the mexCD-oprJ determinant from the Pseudomonas aeruginosa chromosome . Functional analysis of the cloned resistance region from pB4 in Pseudomonas sp . B13 indicated that the RND-MFP-OMF efflux system conferred high-level resistance to erythromycin and roxithromycin resistance on the host strain . This is the first example of an RND-MFP-OMF-type antibiotic resistance determinant to be found in a plasmid genome . The global genetic organization of pB4 implies that its gene load might be disseminated between bacteria in different habitats by the combined action of the conjugation apparatus and the mobility of its component elements.

Environ Microbiol, 2003 Mar, 5(3), 202 - 11
Quantification of cell-specific substrate uptake by probe-defined bacteria under in situ conditions by microautoradiography and fluorescence in situ hybridization; Nielsen JL et al.; A technique based on quantitative microautoradiography (QMAR) and fluorescence in situ hybridization (FISH) was developed and evaluated in order to determine the quantitative uptake of specific substrates in probe-defined filamentous bacteria directly in a complex system . The technique, QMAR-FISH, has a resolution of a single cell and is based on an improved fixation protocol and the use of an internal standard of bacteria with known specific radioactivity . The method was used to study the in situ ecophysiology of the filamentous bacteria 'Candidatus Meganema perideroedes' and Thiothrix sp . directly in an activated sludge system . The cellular uptake rate of tritium-labelled substrates revealed an average cell-specific uptake rate of 4.1 yen 10-15 mol of acetate cell-1 h-1 and 3.1 yen 10-15 mol of acetate cell-1 h-1 for the two filamentous species respectively . The two filamentous species had very similar activity in all cells along each filament . Surprisingly, the filaments within both probe-defined populations had threefold variation in activity between the different filaments, demonstrating a large variation in activity level within a single population in a complex system . The substrate affinity (Ks) for uptake of acetate of the cells within the two filamentous bacteria was determined by incubation with variable concentrations of labelled acetate . The Ks values of the 'Candidatus Meganema perideroedes' and the Thiothrix filamentous bacteria were determined to be 1.8 micro M and 2.4 micro M acetate respectively.

Acta Microbiol Pol, 2002, 51(3), 285 - 92
Studies on the effect of inoculation of activated sludge with bacteria actively degrading hydrocarbons on the biodegradation of petroleum products; Bieszkiewicz E et al.; Eighteen strains of bacteria were isolated from activated sludge purifying petroleum-refining wastewaters . These strains were plated on solidified mineral medium supplemented with oil fraction in concentration 1000 mg/l . Four of the strains that grew best in the presence of oil were selected for further studies . The strains were identified based on Bonde's scheme and microscopic observations . Three of them belonged to the genus Arthrobacter and one to the genus Micrococcus . Stationary cultures of single strains and their mixtures were set up in mineral medium containing oil (sterile and non-sterile) as sole carbon source in concentration 1000 mg/l . The oils were found to be removed the most efficiently by a mixture of the strains . After 14 days of culture the amount of oil was utilized by from 63 to 95% . In the next stage of the studies the bacteria were used to inoculate activated sludge . Stationary cultures of the activated sludge were set up in mineral medium with oil . The utilisation of petroleum products by non-inoculated activated sludge (control), activated sludge inoculated with a single strain or a mixture of all four strains was examined . In both inoculated activated sludge cultures approximately 80% of the oils were removed, compared to 60% in the control activated sludge . Therefore, inoculated activated sludge showed 20% higher effectiveness of removal of petroleum derivatives.

Acta Microbiol Pol, 2002, 51(3), 205 - 16
Green fluorescent protein as a molecular marker in microbiology; Rosochacki SJ et al.; Molecular markers such as: lacZ (b-galactosidase), xylE (catechol 2,3-dioxygenase), lux (bacterial luciferase), luc (insect luciferase), phoA (alkaline phosphatase), gusA and gurA (beta-glucuronidase), gfp (green fluorescent protein), bla (beta-lactamase) and other antibiotic resistance markers, heavy metals resistance genes are commonly used in environmental microorganisms research (Errampaii et al., 1998; Kohler et al., 1999) . Most of these markers require one or more substrates, complex media and/or expensive equipment for detection . The gfp gene is widely used as a marker because of its very useful properties such as high stability, minimal toxicity, non-invasive detection and the ability to generate the green light without addition of external cofactors and without application of expensive equipment . Various applications of that reporter gene were showed starting from monitoring of microorganism's survival in complex biological systems such as activated sludge to biodegradation of chemical compounds in soil . GFP allowed the detection, determination of spatial location and enumeration of bacterial cells from diverse environmental samples such as biofilm and water . The gfp as a biomarker was very useful in monitoring of gene expression and protein localisation in bacterial cells, too . The techniques with using gfp marker promise to supply a better understanding of environmental processes . It can make possible to use that knowledge in designing more effective and more efficient methods of biodegradation of toxic compounds from different environments.

Water Sci Technol, 2003, 47(1), 263 - 70
Fouling and cleaning of microfiltration membrane in municipal wastewater reclamation; Xing CH et al.; This paper presents an investigation on fouling and cleaning of a tubular microfiltration membrane for municipal wastewater reclamation . A bi-level complex model, namely channel clogging and pore plugging, was introduced to elucidate the fouling mechanism . Based on 135 days of microfiltration of activated sludge, a preventive method for channel clogging was reasonably proposed and proven to be effective . Without channel clogging, the operation period was observed a five-fold increase on average, reaching 3-4 weeks . To remove pore plugging, a multi-step chemical cleaning was employed and further optimized in terms of temperature and alkaline concentration . Generally, the chemical cleaning could restore the membrane permeability to higher than 90%.

Water Sci Technol, 2003, 47(1), 205 - 10
Dissolved air flotation clarification of activated sludge and wastewaters from chemical industry; Jokelat P et al.; Wastewaters from separate chemical factories are treated together in an extended aeration activated sludge plant . The factories produce chemicals for paper industry (e.g . starch), latexes and animal feed . The components of the wastewaters include styrene, tertiary butanol and vinyl acetate . Activated sludge is clarified by sedimentation . During winter time, when the water temperature was 3-12 degrees C, the clarification deteriorated causing carry over of suspended solids containing COD . Enhancement of suspended solids and COD removals was studied in a dissolved air flotation jar test unit . Flotation trials were conducted for activated sludge, sedimentation treated final effluent (tertiary treatment) and separate wastewater fractions . The need for chemicals, flocculation and amount of recycle water were judged according to the achieved removals . Dissolved air flotation was found well suited for the clarification of activated sludge, but not technically and economically feasible for the clarification of the wastewater streams before the activated sludge treatment.

Water Sci Technol, 2003, 47(1), 133 - 8
Non-woven fabric filter separation activated sludge reactor for domestic wastewater reclamation; Seo GT et al.; A non-woven fabric filter was experimentally evaluated for solid-liquid separation in an activated sludge reactor as an alternative membrane . A polypropylene fabric filter (70, 50 and 35 g/m2) was used for the experiment . The pilot system was operated in A/O (Anaerobic/Oxic) type in which the filter module was submerged into the oxic compartment . The filtration module consists of 10 plate type rectangular filter elements with effective filtration area, 2 m2 . Gravity filtration was carried out for solid-liquid separation by changing the water head 0.05-0.5 m without backwashing during the system operation . Initial permeate flux was set at 0.4 m/d . C/N ratio of raw wastewater was controlled at 4.5 in terms of BOD/T-N . The fabric filter system showed a good performance enough for domestic wastewater treatment . Effluent solid concentration was 3.2 mg/L (93.5% removal) . COD removal efficiency was 91.6% producing an effluent concentration around 13 mg/L . 66% of total nitrogen removal could be obtained at the adjusted C/N ratio of influent wastewater . However phosphorus removal was very low at 23% . It was found that the initial flux of 0.4 m/d should be maintained for stable performance of the system.

Water Sci Technol, 2003, 47(1), 65 - 70
Effects of salt concentration on floc characteristics and pollutants removal efficiencies in treatment of seafood wastewater by SBR; Moon BH et al.; Most seafood wastewater has been treated by the activated sludge process . Due to changes in salt concentration, pollutant loadings and raw materials, the process is not operated satisfactorily to meet effluent regulation . Most problems faced at present are solid liquid separation . In this study, effects of salt concentration on floc characteristics and pollutants removal efficiencies were investigated in treatment of seafood wastewater by SBR . For analyzing fractal dimension of flocs, the small angle laser light scattering (SALLS) method was applied using a Diffraction Particle Sizer (Malvern Instruments) . Organic removal efficiencies (in terms of COD(Mn)) decreased with increasing salt concentration, but eventually reached a steady state . Fractal dimension and floc size also showed similar trends with changing salt concentration . The main reasons to reduced pollutant removal efficiencies were deteriorated biological activity and settling properties . The biological activity was affected faster than the floc characteristics by increasing salt concentration . The deteriorated settling properties were explained by decreased size and fractal dimension of floc due to increasing salt concentration . The settling properties of floc such as sludge volume index (SVI) and zone settling velocity (ZSV) were related to size and fractal dimension of floc . The fractal dimension of floc was better related to the settling properties than the size of floc.

Res Microbiol, 2003 Jan-Feb, 154(1), 17 - 23
Degradation of 4-amylphenol and 4-hexylphenol by a new activated sludge isolate of Pseudomonas veronii and proposal for a new subspecies status; Ajithkumar B et al.; Novel Pseudomonas strains INA04, INA05, and INA06, were isolated from activated sludge . Strain INA06 was found to degrade long chain alkylphenols such as 4-n-amylphenol and 4-n-hexylphenol as the sole source of carbon, apart from co-metabolic degradation of 4-n-nonylphenol in the presence of phenol, while INA04 and INA05 could grow on phenol, but could not grow well on alkylphenols . Induction studies on strain INA06 revealed a broad substrate-specific phenol hydroxylase, for the metabolism of phenol and alkylphenols, inducible with phenol or para-substituted alkylphenol . They bore close resemblance to members of Pseudomonas sensu stricto . 16S rDNA sequence homology of INA06 was closest to P . veronii (99.7%) . DNA-DNA hybridization pointed out higher linkage (64% similarity) to the type strain of P . veronii than to other species of Pseudomonas sensu stricto (>60%) . The BOX-PCR profile of all INA strains was similar, but different from that of P . veronii . Since biochemical characteristics were similar to those of P . veronii, and genetic relatedness was at the margin of species differentiation level (70%), we propose these strains to be treated as a new subspecies of P . veronii . The type strain of this new subspecies, named P . veronii subsp . inensis subsp . nov., is strain INA06 . The accession number of strain INA05 is CIP 107595=JCM11829, and that of INA06 is CIP107594(T)=JCM11828(T) . The 16S rDNA sequence accession number (DDBJ/EMBL/GenBank) of strain INA06 is AB056120.

J Hazard Mater, 2003 Feb 28, 97(1-3), 295 - 314
Alkaline thermal sludge hydrolysis; Neyens E et al.; The waste activated sludge (WAS) treatment of wastewater produces excess sludge which needs further treatment prior to disposal or incineration . A reduction in the amount of excess sludge produced, and the increased dewaterability of the sludge are, therefore, subject of renewed attention and research . A lot of research covers the nature of the sludge solids and associated water . An improved dewaterability requires the disruption of the sludge cell structure . Previous investigations are reviewed in the paper . Thermal hydrolysis is recognized as having the best potential to meet the objectives and acid thermal hydrolysis is most frequently used, despite its serious drawbacks (corrosion, required post-neutralization, solubilization of heavy metals and phosphates, etc.) . Alkaline thermal hydrolysis has been studied to a lesser extent, and is the subject of the detailed laboratory-scale research reported in this paper . After assessing the effect of monovalent/divalent cations (respectively, K(+)/Na(+) and Ca(2+)/Mg(2+)) on the sludge dewaterability, only the use of Ca(2+) appears to offer the best solution . The lesser effects of K(+), Na(+) and Mg(2+) confirm previous experimental findings.As a result of the experimental investigations, it can be concluded that alkaline thermal hydrolysis using Ca(OH)(2) is efficient in reducing the residual sludge amounts and in improving the dewaterability . The objectives are fully met at a temperature of 100 degrees C; at a pH approximately 10 and for a 60-min reaction time, where all pathogens are moreover killed . Under these optimum conditions, the rate of mechanical dewatering increases (the capillary suction time (CST) value is decreased from approximately 34s for the initial untreated sample to approximately 22s for the hydrolyzed sludge sample) and the amount of DS to be dewatered is reduced to approximately 60% of the initial untreated amount . The DS-content of the dewatered cake will be increased from 28 (untreated) to 46%.Finally, the mass and energy balances of a wastewater treatment plant with/without advanced sludge treatment (AST) are compared . The data clearly illustrate the benefits of using an alkaline AST-step in the system.

J Hazard Mater, 2003 Feb 28, 97(1-3), 159 - 71
Combined physical, chemical and biological treatments of wastewater containing organics from a semiconductor plant; Lin SH et al.; Wastewater containing organics from a semiconductor plant was experimentally investigated in this study . The wastewater is characterized by strong color, high chemical oxygen demand (COD), a large amount of refractory volatile organic compounds and low biodegradability . Because of these characteristics, treatment of this wastewater by traditional activated sludge method is essentially impossible . In the present work, combined physical, chemical and biological methods were synergistically utilized to tackle the wastewater . The combined treatment consisted of air stripping, modified Fenton oxidation and sequencing batch reactor (SBR) method . Air stripping was employed to remove the majority of volatile organic components (notably isopropyl alcohol) from the wastewater, while the Fenton treatment decomposed the remaining refractory organics leading to simultaneous reductions of wastewater COD and color . After proper dilution with other low-strength, organics-containing wastewater stream, the wastewater effluent was finally treated by the SBR method . Experimental tests were conducted to determine the effectiveness and the optimum operating conditions of each treatment process . Test results clearly demonstrated the advantages of the combined treatments . The treatment train was found capable of lowering the wastewater COD concentration from as high as 80,000 mg/l to below 100mg/l and completely eliminating the wastewater color . The overall water quality of the final effluent exceeded the direct discharge standard and the effluent can even be considered for reuse.

Appl Environ Microbiol, 2003 Feb, 69(2), 938 - 44
Desulfonation and degradation of the disulfodiphenylethercarboxylates from linear alkyldiphenyletherdisulfonate surfactants; Schleheck D et al.; Earlier work showed that the biodegradation of a commercial linear monoalkyldiphenyletherdisulfonate surfactant as a carbon source for microbial growth leads to the quantitative formation of corresponding disulfodiphenylether carboxylates (DSDPECs), which were not degraded . alpha-Proteobacterium strain DS-1 (DSM 13023) catalyzes these reactions . These DSDPECs have now been characterized by high-pressure liquid chromatography coupled via an electrospray interface to a mass spectrometer . DSDPECs were a complex mixture of compounds which indicated catabolism via omega-oxygenation and beta-oxidation . DSDPECs were subject to quantitative desulfonation in bacterial cultures in which they served as sole sulfur sources for bacterial growth . On average, one sulfonate group per DSDPEC species was removed, and the organism responsible for this desulfonation was isolated and identified as Rhodococcus opacus ISO-5 . The products were largely monosulfodiphenylether carboxylate-phenols (MSDPEC-phenols) . MSDPEC-phenols were subject to extensive dissimilation by bacteria from activated sludge.

Environ Sci Technol, 2003 Jan 15, 37(2), 292 - 9
Hydrodynamics of biological aggregates of different sludge ages: an insight into the mass transport mechanisms of bioaggregates; Li XY et al.; Internal permeation and its role in mass transport to biological aggregates are investigated through detailed settling experiments . Three groups of bacterial aggregates (0.8-3.2 mm), which were different in fractal dimension and porosity, were generated in batch activated sludge reactors with biomass residence times (BRTs) of 5, 10, and 20 days . An apparatus of vertically connected double settling columns, which were filled respectively with water and an EDTA solution of a higher density, was used to characterize the settling and permeability features of individual aggregates . The settling velocities observed in water were in good agreement with those predicted by Stokes' law for porous but impermeable aggregates . The BRT10 and BRT20 aggregates, with porosities that were generally less than 0.92, had fluid collection efficiencies ranging from 0 to 0.1, while the BRT5 aggregates with porosities that were generally higher than 0.97 were almost completely impermeable . It is suggested that bioaggregates with either a tightly or a loosely packed structure cannot be as highly permeable as characterized for nonbiological fractal aggregates . While falling from water into the denser EDTA liquid, many BRT10 and BRT20 aggregates stopped and stayed below the interface of the two liquids for a period that was more than an order of magnitude shorter than the prediction based on the assumption of molecular diffusion as the predominant mass transport mechanism to the aggregates . The results indicate that limited intra-aggregate convection, which may not be important to the hydrodynamic properties of bioaggregates, could significantly enhance mass transport to suspended aggregates in biological wastewater treatment reactors.

Indian J Exp Biol, 2002 Jan, 40(1), 101 - 5
Degradation of predigested distillery effluent by isolated bacterial strains; Jain N et al.; Batch studies were conducted on degradation of anaerobically digested distillery wastewater by three bacterial strains, viz . Xanthomonas fragariae, Bacillus megaterium and Bacillus cereus in free and immobilized form, isolated from the activated sludge of a distillery wastewater treatment plant . The removal of COD and colour with all the three strains increased with time up to 48 hr and only marginal increase in COD and colour removal efficiency was observed beyond this period up to 72 hr . After this period removal efficiency remained fairly constant up to 120 hr . The maximum COD and colour removal efficiency varied from 66 to 81% and 65 to 75%, respectively for both free and immobilized cells of all the three strains . The strain Bacillus cereus showed the maximum efficiency of COD (81%) and colour (75%) removal out of the three strains . An interrelationship between the percent COD and colour removal was carried out by correlation and regression analysis and was justified by high values of coefficient of correlation (r = 0.99) for all the cases . The first order removal rate kinetics was also applied and rate constants were evaluated for COD and colour removal efficiencies.

Ann Chim, 2002 Nov-Dec, 92(11-12), 1035 - 44
Laboratory studies on waste water sludge application for acid soil remediation; Calace N et al.; In this work the effects of sludge disposal on pH values, buffer capacity and adsorption capacity of an acid soil were studied . A stabilized waste water sludge and a paper mill sludge were employed; the pH values of both sludges were higher than 8 . The observed differences between soil-urban sludge and soil-paper mill sludge systems can be ascribed to the nature of the compounds present in the sludges and adsorbed on the soil . Both kinds of sludge are able to modify the natural pH of the soil, the buffer capacity and its capacity to retain metal . These modifications increase with increasing soil-sludge contact time and are higher for paper mill sludges . Temperature affects only the modifications due to urban sludge treatment.

Wei Sheng Wu Xue Bao, 1998 Apr, 38(2), 108 - 13
{Studies on reduction of hexavalent chromium by fungi}; Wang B et al.; Several fungal strain, isolated from activated sludge, sewage and soil, were able to grow in the medium containing 300-500 mg/L K2Cr2O7, and strain BS-1 was capable of resistance to K2Cr2O7 up to 900 mg/L . After 4-6 d growing of the strain BS-1 and other 3 strains in the liquid medium added 200 mg/L K2Cr2O7, the Cr(VI) content of the medium disappeared completely . These strain were identified as Penicillium sp . BS-1, BS-3, Aspergillus niger BR-4, Aspergillus flavus BX-1 respectively . The results from the detection of the fungal culture by UV-absorbance spectrum and chemical analysis showed that high-toxic Cr(VI) was reduced to lesstoxic Cr(III) . Reaction conditions and effectors of Cr(VI) reduction by intact cells of Penicillium sp . BS-1 were studied . The optimum temperature was 30 degrees C, the optimum pH was 7.0 . Addition of glucose (0.25%) enhanced Cr(VI) reduction, but high concentrations of Cr(VI) inhibited the reduction of Cr(VI) to Cr(III).

Wei Sheng Wu Xue Bao, 2001 Jun, 41(3), 348 - 52
{Composition and structure of bioflocculant BP25}; Liu Z et al.; A strain of Bacillus megaterium screened from activated sludge could produce exocellular flocculant . The flocculant was purified through ethanol precipitation and Sephadex S-500 column chromatography . The purified flocculant BP25 was assayed by Bradford reaction, agarose gel electrophoresis and Sulfate-phenol method . The results showed that BP25 was a kind of polysaccharide which contains 36.97% O, 6.28% H, 47.00% C, 0% No NMR assay showed BP-25 contains no uronic acid . Gas-chromatography assay combined with thin-layer chromatography of acid hydralate revealed that BP25 contains Glucose and Mannose with the mole ratio of 4:1 . Methylation analysis revealed the polysaccharide contains alpha-1, 6 glycosidicbond and alpha-1, 3 glycosidicbond . The main chains are comprised of Glucose and all the Mannose are in the side chains . Possible repeating unit structure was deduced.

Environ Toxicol, 2003 Feb, 18(1), 45 - 51
Tannery wastewater characterization and toxicity effects on Daphnia spp; Cooman K et al.; Tannery wastewater contains large quantities of organic and inorganic compounds, including toxic substances such as sulfides and chromium salts . The evaluation of wastewater quality in Chile nowadays is based on chemical specific measurements and toxicity tests . The goal of this research was to characterize tannery wastewater and to relate its physical/chemical parameters with its acute toxicity effect on Daphnia pulex . To distinguish the most important toxic compounds, physical/chemical techniques were applied to a grab sample of a final effluent based on the Phase I toxicity identification evaluation (TIE) procedure . In addition, the toxicity of a beamhouse effluent after an activated sludge reactor treatment was investigated on Daphnia magna (introduced species) and D . pulex (native species) . Effluent from different tannery processes (soaking, beamhouse, tanning and final) demonstrated high values of chemical organic demand (COD; 2840-27,600 mg L(-1)), chloride (1813-16,500 mg L(-1)), sulfate (230-35,200 mg L(-1)), and total solids (8600-87,100 mg L(-1)) . All effluents showed extremely toxic effects on D . pulex, with 24-h mean lethal values (LC(50)) ranging from 0.36% to 3.61% . The Phase I TIE profile showed that toxicity was significantly reduced by air stripping, filtration, and a cationic exchange resin, with toxicity reductions ranging between 46% and 76% . The aerobically treated beamhouse effluent showed significantly less toxicity for both species (43%-74%) . The chemical parameters demonstrated that the remaining toxicity of the treated beamhouse effluent was associated with its ammonia (120 mg N-NH(3) L(-1)) and chloride (11,300 mg Cl(-) L(-1)) contents .

Environ Toxicol, 2003 Feb, 18(1), 37 - 44
Alternative inocula as activated sludge surrogate culture for a toxicity test; Paixao SM et al.; The use of activated sludge to assess the potential toxicity and environmental impact of chemicals and wastewaters suffers from several drawbacks related to the heterogeneity, absence of standardization, and health risk associated with this mixed-sewage population . To search for reliable testing inoculum alternatives, the performance of two commercial inocula (BI-CHEM and BIOLEN M112), a garden-soil inoculum and a pure culture of Pseudomonas sp., was compared with an activated sludge inoculum (AS) in the inhibition respiration test ISO 8192-1986 (E) . The respiration rates of microbial inocula were assayed for the reference compound 3,5-dichlorophenol . The acute toxicity values (IC(50)) ranged from 6.7 mg/L (Pseudomonas sp.) to 22.7 mg/L (garden soil), overlapping the expected values for activated sludge microorganisms despite the bacterial diversity . The assayed microbial inocula also showed higher reproducibility than AS and an overall similarity of catabolic profiles obtained with Biolog EcoPlates was observed between AS and some mixed inocula . These results point to the potential ability of such inocula as surrogate cultures in relevant activated sludge-based bioassays . New, well-defined, standardized, and safe tools will then be available for monitoring the ecological impact of hazardous substances and effluents, thus providing environmental protection .

Huan Jing Ke Xue, 2002 Sep, 23(5), 84 - 7
{The kinetics of biological treatment of bleaching liquor from straw pulp process}; Zhang J et al.; The batch test of oxygen uptake rate (OUR) measurement was used to simulate biochemical reaction process in aerobic reactor treating bleaching liquor from straw pulp process . Lawrence-McCarty kinetic model was used to analyze the biochemical reaction process . The kinetic equation of bleaching liquor biological treatment, v = 0.72 S/(60.43 + S), was deduced from results of the OUR experiment and the bench experiment . The specific substrate degradation rate estimated by the kinetic equation was higher than that of practical wastewater treatment plant . The phenomenon was attributed to the decrease of activated sludge activity caused by cellulose suspended solid accumulation in aerobic reactor of practical plant.

Huan Jing Ke Xue, 2002 Sep, 23(5), 76 - 9
{Biodegraded characteristics of MGP-wastewater by domestic and screened organisms}; Ren Y et al.; Among 16 bacteria that were screened out from 5 activated sludge, S-2, Y-3, XH-3 and their mixed strains M-3 were selected to biodegrade MGP (Manufacture gas from petroleum)-wastewater . They can remove 38.4%-44.0% CODCr, 95.4%-97.0% hydroxybenzene and 47.1%-53.7% aromatic compound after 60 h treatment, but the removal rate of NH4(+)-N was only 14.0%-17.6% . About 77 toxic organic compounds were detected by GC/MS analysis, the aromatic compounds which had 3 rings and 4-6 rings can be biodegraded by the bacteria . The removal rate of CODCr, NH4(+)-N and extractable organic compound were improved 13.1%-22.9%, 18.4%-22.7% and 13.1%-18.1% respectively when glucose was added in the wastewater, and when ethanol was existing in the wastewater, the corresponding increase were 12.5%-21.2%, 29.7%-42.2% and 6.7%-7.7% . The total removal rates of aromatic compound were increased 17.7%-21.7%, 15.4%-21.2% . The screened strains can improve the biodegradation rate of MGP-wastewater.

Huan Jing Ke Xue, 2002 Sep, 23(5), 72 - 5
{Treatment of drilling wastewater from oil field by using yeast}; Wang Y et al.; Two strains of yeast, namely Wickerhamiella domercqii and Candida boidinii, were acquired through screening from soil samples contaminated by drilling wastewater . A TOC removal of 40.5% was acquired when the mixture of the two yeast strains was used for drilling wastewater treatment, a little higher than that with activated sludge acclimated with wastewater (35.2%) . Some organic compounds in the fraction of molecular weight above 60,000 were found to be biodegradable.

J Microbiol Methods, 2003 Mar, 52(3), 315 - 23
A novel approach for extraction of PCR-compatible DNA from activated sludge samples collected from different biological effluent treatment plants; Purohit HJ et al.; This paper describes a method that facilitates the extraction of PCR-compatible DNA from different activated sludge samples . The approach involves a novel preprocessing step in DNA extraction, which removes potential PCR inhibitors . The sludge was washed with different ratios of acetone and petroleum ether after pretreatment with 0.01% Tween-20 at 50 degrees C . It was observed that an initial washing step with 50 mM Tris-HCl, pH 9.0, before the detergent-solvent step, improved the quality of the extracted DNA . The extraction protocol resulted in amplifiable amounts of DNA when 10 mg of a sludge sample was used, even in the presence of phenol as a sludge contaminant . The usefulness of the extracted template was demonstrated by carrying out different PCR reactions . The random amplified polymorphic DNA (RAPD) patterns demonstrated the diversity of sludge samples.

Water Sci Technol, 2002, 46(11-12), 203 - 8
A mathematical model for the flotation of waste activated sludge; Fujisaki K et al.; A mathematical model that describes a batch flotation process is presented . The model employed a similar method to the hindered settling of flocculated material . This idea is based on our experimental results that the time growth curves of separated liquor zone showed a similar character to the settling curve of flocculated material, when the vertical axis reversed . In this model, it is also assumed that the gas phase and solid phase have the same movement, that is microbubbles and solid sludge particles joined to form aggregated floc . By comparing the numerical prediction with experimental data, the usefulness of the model is confirmed and some examples of flotation simulation are demonstrated.

Water Sci Technol, 2002, 46(11-12), 189 - 94
Isolation and examination of copper removing bacteria from activated sludge culture; Fukushi K et al.; Experiments were carried out to isolate metal removing bacteria from activated sludge culture and test the metal removal capability of isolated bacteria . Two concentrations of copper solution (CuCl2) used to select the copper-tolerance level of each isolate were 0.05 mM and 2.5 mM . Experimental data showed that isolates could be obtained by using non-selective medium (NSM) in the presence of copper . The isolates were displayed on agar plates with diverse colonial morphological characteristics . A maximum uptake of 81 mg/g dry cell mass was observed at an initial copper concentration of 50 mg/l . The minimum uptake was 9 mg/g dry cell mass . Copper uptake efficiency by isolates from NSM with 0.5 mM CuCl2 was significantly different with those from NSM with 2.5 mM CuCl2.

Water Sci Technol, 2002, 46(11-12), 71 - 6
Performance of coarse pore filtration activated sludge system; Alavi Moghaddam MR et al.; A coarse pore filter can be applied inside the aeration tank to facilitate the separation of sludge from liquid instead of sedimentation . This filter has pores, which are irregular in shape, and the pore size is bigger than those of MF . The objectives of the study were to maintain as much as MLSS in the activated sludge process with coarse pore filter and to investigate the performance under high MLSS condition . Small-scale reactor results so far show good quality of effluent specially after starting the sludge bulking in the system in terms of SS, TOC, DOC and turbidity . The average carbon removal for 62 days operation of this system was about 94% (based on effluent DOC) and 87% (based on effluent TOC) . The average sludge yield in this system is about 0.44 kg MLSS/kg TOC which is about 0.24 kg MLSS/kg BOD . This amount is less than those of conventional activated sludge and trickling filter.

Biotechnol Bioeng, 2003 Mar 5, 81(5), 570 - 7
Effect of nitrite and nitrate on in situ sulfide production in an activated sludge immobilized agar gel film as determined by use of microelectrodes; Okabe S et al.; Microelectrode, fluorescence in situ hybridization (FISH), and denaturing gradient gel electrophoresis (DGGE) analyses were used to investigate the effect of nitrite and nitrate on in situ sulfide production in an activated sludge immobilized agar gel film . Microelectrode measurements of O(2), H(2)S, NO(3)(-), NO(2)(-), and pH revealed that the addition of NO(2)(-) and NO(3)(-) forced sulfate reduction zones deeper in the agar gel and significantly reduced the in situ sulfide production levels . The sulfate reduction zone was consequently separated from O(2) and NO(2)(-) or NO(3)(-) respiration zones with increasing the concentrations of NO(2)(-) and NO(3)(-) . These NO(2)(-) and NO(3)(-) treatments had only a transient effect on sulfide production . The in situ sulfide production quickly recovered to the previous levels when NO(2)(-) and NO(3)(-) were removed . The PCR-DGGE and FISH analyses revealed that 2-day-continuous addition of 500 microM NO(3)(-) did not change the metabolically active sulfate-reducing bacterial (SRB) community . On the basis of these data, it could be concluded that the addition of NO(2)(-) and NO(3)(-) did not kill SRB, but induced the interspecies competition for common carbon source (i.e., acetate) between nitrate-reducing heterotrophic bacteria and SRB and enhanced the oxidation of the produced sulfide, which were main possible causes of the suppression of in situ sulfide production in the agar gel .

Appl Environ Microbiol, 2003 Jan, 69(1), 641 - 3
Evaluation of the redox dye 5-cyano-2,3-tolyl-tetrazolium chloride for activity studies by simultaneous use of microautoradiography and fluorescence in situ hybridization; Nielsen JL et al.; Three microscopic in situ techniques were used simultaneously to investigate viability and activity on a single-cell level in activated sludge . The redox dye 5-cyano-2,3-tolyl-tetrazolium chloride (CTC) was compared with microautoradiography (MAR) and fluorescence in situ hybridization (FISH) to indicate activity of cells in Thiothrix filaments and in single floc-forming bacteria . The signals from MAR and FISH correlated well, whereas only 65% of the active Thiothrix cells and 41% of all single cells were detectable by CTC reduction, which mainly targeted the most active cells.

Appl Environ Microbiol, 2003 Jan, 69(1), 241 - 51
Metabolic pathway for propionate utilization by phosphorus-accumulating organisms in activated sludge: 13C labeling and in vivo nuclear magnetic resonance; Lemos PC et al.; In vivo 13C and 31P nuclear magnetic resonance techniques were used to study propionate metabolism by activated sludge in enhanced biological phosphorus removal systems . The fate of label supplied in {3-13C}propionate was monitored in living cells subjected to anaerobic/aerobic cycles . During the anaerobic phase, propionate was converted to polyhydroxyalkanoates (PHA) with the following monomer composition: hydroxyvalerate, 74.2%; hydroxymethylvalerate, 16.9%; hydroxymethylbutyrate, 8.6%; and hydroxybutyrate, 0.3% . The isotopic enrichment in the different carbon atoms of hydroxyvalerate (HV) produced during the first anaerobic stage was determined: HV5, 59%; HV4, 5.0%; HV3, 1.1%; HV2, 3.5%; and HV1, 2.8% . A large proportion of the supplied label ended up on carbon C-5 of HV, directly derived from the pool of propionyl-coenzyme A (CoA), which is primarily labeled on C-3; useful information on the nature of operating metabolic pathways was provided by the extent of labeling on C-1, C-2, and C-4 . The labeling pattern on C-1 and C-2 was explained by the conversion of propionyl-CoA to acetyl-CoA via succinyl-CoA and the left branch of the tricarboxylic acid cycle, which involves scrambling of label between the inner carbons of succinate . This constitutes solid evidence for the operation of succinate dehydrogenase under anaerobic conditions . The labeling in HV4 is explained by backflux from succinate to propionyl-CoA . The involvement of glycogen in the metabolism of propionate was also demonstrated; moreover, it was shown that the acetyl moiety to the synthesis of PHA was derived preferentially from glycogen . According to the proposed metabolic scheme, the decarboxylation of pyruvate is coupled to the production of hydrogen, and the missing reducing equivalents should be derived from a source other than glycogen metabolism.

Int J Syst Evol Microbiol, 2002 Nov, 52(Pt 6), 2029 - 34
Sphingopyxis witflariensis sp . nov., isolated from activated sludge; Kampfer P et al.; Classification of strain W-50(T), which was isolated from a wastewater treatment plant, was investigated by a polyphasic approach . Cells of strain W-50(T) were Gram-negative, strictly aerobic, oxidase-positive and yellow-pigmented . Ubiquinone Q-10 was the main respiratory lipoquinone system and polar lipid fingerprints were characterized by the presence of a sphingoglycolipid, suggesting that strain W-50(T) belongs to the alpha-4 subclass of the Proteobacteria . Sequencing and comparative analyses of the 16S rRNA gene of strain W-50(T) supported its chemotaxonomic allocation as an alpha-4 proteobacterium . The most closely related established taxa were species of the genus Sphingopyxis, including Sphingopyxis macrogoltabida (97.3% similarity) and Sphingopyxis terrae (96-4% similarity), and Sphingomonas taejonensis (97.3%) . These findings were supported by both the polyamine content, which consisted mainly of spermidine {12.9 micromol (g dry wt)(-1)}, and the presence of 2-OH 14:0, 2-OH 15:0 and 2-OH 16:0 in the cellular fatty acid profile . DNA-DNA hybridization experiments resulted in similarity values of 31.9% between strain W-50(T) and Sphingopyxis macrogoltabida IFO 15033(T), 44.9% between strain W-50(T) and Sphingopyxis terrae IFO 15098(T) and 31.0% between strain W-50(T) and Sphingomonas taejonensis KCTC 2884(T) . Based upon results obtained by detailed physiological/biochemical testing and previously published molecular evidence, strain W-50(T) was clearly distinguishable from all other Sphingopyxis species . For these reasons, the creation of a novel species, Sphingopyxis witflariensis sp . nov., is proposed; strain W-50(T) (= DSM 14551(T) = CIP 107174(T)) is the type strain.

Water Res, 2003 Jan, 37(2), 353 - 61
Influence of hydraulic shock loads and TDS on the performance of large-scale CETPs treating textile effluents in India; Pophali GR et al.; The present study relates to the influence of hydraulic shock loads and total dissolved solids (TDS) on the performance of three large-scale common effluent treatment plants (CETPs) treating textile effluents, which is generated from clusters of small-scale industries in the state of Rajasthan in India . Of the three CETPs, two having capacities 7.0 and 9.0 million liters per day (mld) are located in Pali and one of capacity 6.0 mld in Balotra, District Barmer . Wastewater from about one thousand small-scale industries is treated in these CETPs . The effects of hydraulic shock loads and TDS on effluent data from secondary clarifier for parameters biochemical oxygen demand (BOD) and suspended solids (SS) for CETPs at Pali, and chemical oxygen demand (COD) and SS for the CETP at Balotra were studied . It was observed that the effluent BOD and SS remained within the prescribed limits for CETP Pali at 30% increased flow rate, whereas effluent COD and SS at 30% increased flow rate for CETP Balotra exceeded the prescribed limits and the CETP could sustain 20% increased flow rate . The shock loading analysis revealed that CETP Balotra had reduced capacity to sustain shock loads by 10% as compared to CETP Pali due to the presence of high TDS (15,000-20,000 mg/l) . High TDS interfered with the oxygen transfer necessary for biological metabolism, thereby affected the efficiency of activated sludge process . Hence, activated sludge process treating high TDS effluents are more sensitive to hydraulic shock loads and prone to process upsets.

Water Res, 2003 Jan, 37(2), 281 - 8
Determination of non-ionic surfactants and their biotransformation by-products adsorbed on alive activated sludge; Szymanski A et al.; A procedure has been developed for the determination of non-ionic surfactants (NS) adsorbed on particles of alive and dead activated sludge . The procedure also enables the determination of adsorption of major biodegradation by-products: short-chained ethoxylates, long- and short-chained PEG . The basis of measurement is the determination of NS concentration in a slurry of activated sludge and in a solution phase . The difference between these two concentrations represents the NS adsorbed on activated sludge . Separation of NS and their biotransformation by-products from samples and then on narrower fractions was performed by a sequential liquid-liquid extraction and precipitation with modified Dragendorff reagent . The indirect tensammetric technique (ITT) was applied for the final determination . The developed method was checked using the example of the treatment of the surfactant C12E10 (oxyethylated fatty alcohol) (C12E10) in the continuous flow activated sludge facility . No statistically significant accumulation of C12E10 on the alive activated sludge was detected, probably because of faster C12E10 fission than its adsorption . However, significant adsorption of the short-chained ethoxylates (including free alcohol) on the alive activated sludge was found, as well as statistically significant adsorption of long- and short-chained PEG . The adsorption of surfactant C12E10 and its biodegradation by-products on dead activated sludge was found to be higher than the species adsorption on alive activated sludge.

J Gen Appl Microbiol, 1998 Feb, 44(1), 57 - 63
Cloning and nucleotide sequence of carbazole catabolic genes from Pseudomonas stutzeri strain OM1, isolated from activated sludge; Ouchiyama N et al.; A new carbazole (CAR)-degrading bacterium, called strain OM1, was isolated from activated sludge obtained from sewage disposal plants in Fukuoka Prefecture, and it was identified as Pseudomonas stutzeri . Anthranilic acid (AN), 2'-aminobiphenyl-2,3-diol and its meta-cleavage product, 2-hydroxy-6-oxo-6-(2'-aminophenyl)-hexa-2,4-dienoic acid, were identified as metabolic intermediates of CAR in the ethyl acetate extract of the culture broth . Therefore, the CAR catabolic pathway to AN in strain OM1 was indicated to be identical to those found in the Pseudomonas sp . strains CA06 and CA10 . The strain OM1 degraded catechol (CAT) via a meta-cleavage pathway in contrast to strains CA06 and CA10, which transform catechol into cis, cis-munonic acid . Clones containing a 6.9-kb EcoRI fragment and a 3-kb PstI-SphI fragment were isolated from colonies, forming a clear zone of CAR and a yellow ring-cleavage product from CAT, respectively . Recombinant E . coli carrying the 6.9-kb fragment degraded CAR in the L-broth and produced AN . Cell-free extract from the clone carrying a 3-kb PstI-SphI fragment had high meta-ring-cleavage dioxygenase activity for CAT . The nucleotide sequences of these fragments were determined . The 6.9-kb fragment showed a very high degree of homology with the CAR catabolic genes of strain CA10 . The amino acid and nucleotide sequences of the 3-kb fragment were found to exhibit significant homology with the genes for the CAT-catabolic enzymes of TOL plasmid pWW0, plasmid NAH7, and plasmid pVI150.

Water Sci Technol, 2002, 46(10), 295 - 303
Wastewater sludge as a resource: sludge disposal strategies and corresponding treatment technologies aimed at sustainable handling of wastewater sludge; Odegaard H et al.; The paper discusses different strategies for the disposal of wastewater sludge, particularly the "use on land" strategy and the "productification" strategy . In the "use on land" strategy the new regulations in Europe call for stabilization as well as disinfection of sludge to be used on land . The paper discusses the design and operation experiences with stabilization/disinfection methods in Norway where such treatment has been compulsory since 1995 . In the "productification" strategy it is differentiated between the production of "bio-soils" and production of specific products (energy, nutrients, coagulants etc) and the "marketability" of these products is evaluated . An example of a sludge treatment concept aimed at recycling--the KREPRO process--is presented.

Water Sci Technol, 2002, 46(10), 269 - 75
Effect of extracellular polymers on freeze-thaw conditioning of activated sludge; Ormeci B et al.; In this study, the effects of extracellular polymers on freeze-thaw conditioning of activated sludge are investigated . Various physical and chemical extraction methods including centrifugation, blending, heat, EDTA, EGTA, and NaOH extraction were used to remove extracellular material from sludge matrix . The improvements in freeze-thaw conditioning were evaluated by commonly used measures of sludge dewaterability . The results of this study indicate that removal of extracellular polymers using relatively gentle extraction methods before freeze-thaw conditioning improves the sludge dewaterability after the freeze-thaw . In addition to extracellular polymers, cations also play an important role in determining the freeze-thaw effectiveness on activated sludge . Best dewaterability is achieved when both extracellular polymers and cations are removed from activated sludge before freeze-thaw conditioning.

Water Sci Technol, 2002, 46(10), 231 - 8
Sludge utilisation in agriculture: possibilities and prospects in Greece; Andreadakis AD et al.; The paper presents the prospects for agricultural utilisation of the sludge produced from wastewater treatment plants in Greece and more specifically focuses on a critical review of the legislatory framework, determination of the quantitative and qualitative characteristics of the produced sludges, examination of possible sludge treatment methods and evaluation of the possibilities and prospects of sludge utilisation on the basis of the above considerations . Landfilling is practically the only route to sludge disposal in Greece . However, in view of the anticipated future restrictions for landfilling within the European Union, this method is clearly a short-term solution and alternative options, including agricultural reuse, must be implemented . The results of a recent survey are presented and discussed in relation to this need.

Water Sci Technol, 2002, 46(10), 199 - 208
Biological nutrient removal wastewater treatments and sewage sludge anaerobic mesophilic digestion performances; Bolzonella D et al.; The paper deals with the performances of the mesophilic anaerobic digestion treatment of sewage sludge from a full scale BNR process without primary settling (nominally 300,000 PE) . A relation between the activated sludge observed yields, Y(obs), and the anaerobic digester performance was preliminarily found: for values of Y(obs) of 0.25 kgVSS/kgCOD the anaerobic digester specific gas production showed the best performances (0.22 m3/kgVS(fad)) . This has to be confirmed with wider future studies . It was also shown the level of sludge pre-thickening to be reached for the self-sustaining warming of the digester also in wintertime . According to the energetic balance and to a comparison with an aerobic stabilisation process, it was pointed out as when a co-generation unit for heat and energy production was introduced about 3.4 kWh/PE y of energy were produced in the anaerobic digestion process . On the other hand, 4.3 kWh/PE y were spent if an aerobic stabilisation process was applied . The economic assessment, carried out on the basis of the energy balances, showed that the anaerobic digestion is always economically advantageous if compared to aerobic stabilisation processes, also for small WWTPs . According to the energetic evaluations an environmental balance was assessed, in terms of CO2 emissions . The difference between anaerobic and aerobic processes was about 5.3 kgCO2/PE y in favour of anaerobic processes application.

Water Sci Technol, 2002, 46(10), 97 - 104
Feasibility study of mechanically disintegrated sludge and recycle in the activated-sludge process; Camacho P et al.; The action mechanisms and performances of a combined system associating activated sludge and mechanical treatment (High Pressure Homogenizer) were evaluated for urban wastewater . Discontinuous experiments showed that the energy applied at the first pass was high enough to modify the sludge particulate fraction (high COD release) but without cell lysis . The applied shear forces led to a progressive cell break up (maximal COD release 90% total COD) . Continuous experiments showed less than 20% reduction in sludge production (compared to a control run under the same loading conditions Y(TSS) = 0.35 g TSS x g(-1) COD(removed)) through the application of mechanical treatment (stress frequency = 0.2 d(-1)) . Recycling of mechanical treated sludge to the aeration tank induced a slight increase in effluent TSS, but the biological performance seemed to be maintained . Significant improvements in sludge settling characteristics were observed.

Water Sci Technol, 2002, 46(10), 79 - 87
A comparative study between mechanical, thermal and oxidative disintegration techniques of waste activated sludge; Camacho P et al.; The release performances of an organic and mineral activated sludge matrix were studied for a wide range of disintegration treatments like mechanical, thermal, thermal-chemical and oxidative disintegration techniques . The maximal COD release was 35% of total COD after 24 hours contact time at 95 degrees C . A limiting value of 60% COD release was obtained for 500 and 700 bars after 10 passes . Concerning theoxidative disintegration techniques (O3 and H2O2), a limiting value of around 60-65% of TOC release was observed . Therefore, it was hypothesised that thermal and mechanical treatments allow mainly for breaking apart the micro-organisms while the oxidative treatment destroys the sludge flocs and disrupts the micro-organisms . A release effect of the mineral fraction is observed only oxidative disintegration techniques.

Water Sci Technol, 2002, 46(10), 55 - 61
Use of lysis and recycle to control excess sludge production in activated sludge treatment: bench scale study and effect of chlorinated organic compounds; Nolasco MA et al.; The most widely used treatment system in the pulp and paper industry--the activated sludge--produces high quantities of sludge which need proper disposal . In this paper a modified activated sludge process is presented . A synthetic wastewater, prepared to simulate the effluent of bleached and unbleached pulp and paper plant wastewater, was submitted to treatment in a bench scale aerobic reactor . The excess sludge was lysed in a mechanical mill--Kaddy mill--and totally recycled to the aeration tank . In the first phase the synthetic wastewater, without the chlorinated compounds, was fed to the reactor . In the second phase increasing dosages of the chlorinated compounds were used . Total recycle of excess sludge after disintegration did not produce adverse effects . During the first phase average COD removal efficiency was 65% for the control unit, which operated in a conventional way, and 63% for the treatment unit, which operated with total recycle . During the second phase the COD removal efficiency increased to 77% in the control unit and 75% in the treatment unit . Chlorinated organics removal was 85% in the treatment unit and 86% for the control unit . These differences are not significant.

Water Sci Technol, 2002, 46(10), 1 - 8
Heavy metals extraction from anaerobically digested sludge; Marchloretto MM et al.; This paper reports on the chemical extraction efficiency in the removal of heavy metals from sludge from an activated-sludge system, which receives as influent both industrial and municipal wastewater . Utilizing a series of chemical extractants in a sequential order comprised the first phase of the research, called sequential chemical extraction (SCE) . The work started with the well-known Tessier method followed by Veeken and by Sims and Kline SCE schemes . Afterwards, modified versions of Tessier and Veeken schemes were applied . The second phase, named chemical extraction using pH progressive changes, concerns an alternative to the extraction process . Four acids were tested: nitric, hydrochloric, oxalic and citric and the pH values as well as the time were varied . Some conclusions reveal that although modifying Tessier and Veeken schemes provides more consistent results, SCE is still an imperfect method regarding specificity and selectivity . Besides, it is not advisable to apply one SCE scheme developed for one specific situation to another one, once the accurateness of the method depends on several factors such as sort of material and chemicals, contact time, temperature, etc . The extraction efficiency increases using nitric or hydrochloric acids at low pH values, promoting high extraction efficiency level.

Water Environ Res, 2002 Sep-Oct, 74(5), 437 - 49
Microbial community structures in foaming and nonfoaming full-scale wastewater treatment plants; de los Reyes FL 3rd et al.; A survey of full-scale activated-sludge plants in Illinois revealed that filamentous foaming is a widespread problem in the state, and that the causes and consequences of foaming control strategies are not fully understood . To link microbial community structure to foam occurrence, microbial populations in eight foaming and nine nonfoaming full-scale activated-sludge systems were quantified using oligonucleotide hybridization probes targeting the ribosomal RNA (rRNA) of the mycolata; Gordonia spp.; Gordonia amarae; "Candidatus Microthrix parvicella"; the alpha-, beta-, and gamma-subclasses of the Proteobacteria, and members of the Cytophaga-Flavobacteria . Parallel measurements of microbial population abundance using hybridization of extracted RNA and fluorescence in situ hybridization (FISH) showed that the levels of mycolata, particularly Gordonia spp., were higher in most foaming systems compared with nonfoaming systems . Fluorescence in situ hybridization and microscopy suggested the involvement of "Candidatus Microthrix parvicella" and Skermania piniformis in foam formation in other plants . Finally, high numbers of "Candidatus Microthrix parvicella" were detected by FISH in foam and mixed liquor samples of one plant, whereas the corresponding levels of rRNA were low . This finding implies that inactive "Candidatus Microthrix parvicella" cells (i.e., cells with low rRNA levels) can cause foaming.

Water Environ Res, 2002 Sep-Oct, 74(5), 428 - 36
Microbiology of enhanced biological phosphorus removal in aerated-anoxic Orbal processes; Zilles JL et al.; The traditional process for enhanced biological phosphorus removal (EBPR) in wastewater treatment involves an anaerobic zone followed by an aerobic zone . Although there is no strict anaerobic zone in aerated-anoxic Orbal processes, phosphorus removal in excess of that required for cell growth does occur . The microbial ecology of polyphosphate-accumulating organisms (PAO) in two full-scale Orbal wastewater treatment plants was investigated using flow cytometry to physically separate PAO from non-PAO and fluorescent in situ hybridization (FISH) to identify organisms . Although Candidatus Accumulibacter phosphatis, an uncultured organism associated with EBPR in acetate-fed laboratory-scale reactors, was detected, it did not seem to be the dominant PAO in these processes . Comparative FISH analyses of the activated sludge and the PAO-rich subpopulation did not reveal the presence of a dominant group of PAO in these full-scale plants . Rather, the analysis suggested that the operational characteristics of aerated-anoxic processes might select for a diverse PAO community that is significantly different from that observed in acetate-fed laboratory reactors or in traditional EBPR configurations.

J Gen Appl Microbiol, 2002 Feb, 48(1), 43 - 54
Polyphasic approaches to the identification of predominant polyphosphate-accumulating organisms in a laboratory-scale anaerobic/aerobic activated sludge system; Onda S et al.; By combination of denaturing gradient gel electrophoresis of PCR-amplified 16S rDNA (PCR-DGGE), quinone profiling, and 16S rRNA-targeted fluorescence in situ hybridization (FISH), a polyphosphate-accumulating organism (PAO) responsible for phosphate (P)-removal was identified in activated sludge with high P-removal ability from a laboratory-scale anaerobic/aerobic continuous flow reactor . The DNA fragment from the most dense band on the DGGE gel was closely related to that of 'Candidatus Accumulibacter phosphatis' (beta-Proteobacteria) . Quinone profiling also suggested the predominance of beta-Proteobacteria . FISH with a specific oligonucleotide probe designed for the sequence showed that the targeted bacterium was dominant in the activated sludge, and the accumulation and consumption of polyphosphate were observed by dual staining with 4',6-diamidino-2-phenylindole . The bacterium was concluded to be the responsible PAO in the reactor . However, when the P-removal ability per cell slightly decreased, the dominance of the PAO greatly diminished in the activated sludge . Such sludge might be dominated by other types of PAOs.

J Gen Appl Microbiol, 2002 Feb, 48(1), 35 - 41
Analysis of the differences in microbial community structures between suspended and sessile microorganisms in rivers based on quinone profile; Kunihiro T et al.; In this study, a quinone profiling method was applied to clarify the differences in community structure between suspended and sessile microorganisms in rivers . The compositions of microbial quinone of 6 sites for 4 rivers were analyzed . Ubiquinone (UQ)-8, UQ-10, menaquinone (MK)-7, and plastoquinone (PQ)-9 were observed in all samples of suspended and sessile microorganisms for the sites investigated . The dominant quinone species in suspended microorganisms was ubiquinone, and that in sessile microorganism was photosynthetic quinones (namely PQ-9 and vitamin K1) . This indicated that aerobic bacteria were abundant in the suspended microorganisms, and photosynthetic microorganisms such as micro-algae and cyanobacteria dominated in the sessile microorganisms . The quinone concentration in the river waters tested, which reflects the concentration of suspended microorganisms, ranged from 0.045 to 1.813 nmol/L . The microbial diversities of suspended and sessile microorganisms calculated based on the composition of all quinones were in the range from 3.4 to 7.5, which was lower than those for activated sludge and soils . Moreover, the diversity of heterotrophic bacteria for sessile microorganisms in the rivers was higher than that for the suspended microorganisms.

J Gen Appl Microbiol, 2002 Jun, 48(3), 125 - 33
Isolation and characterization of a Gram-positive polyphosphate-accumulating bacterium; Onda S et al.; A Gram-positive polyphosphate-accumulating bacterium was isolated from phosphate-removal activated sludge using pyruvate-supplemented agar plates . The isolate was oval or coccobacilli (0.4-0.7 x 0.5-1.0 mm) that occurred singly, in pairs or irregular clumps . Polyphosphate granules in the cells were observed by toluidine blue staining . The pure culture of the isolate rapidly took up phosphate (9.2 mg-P/g-dry weight) in the 3-h aerobic incubation without organic substrates, after anaerobic incubation with organic substrates containing casamino acids . When acetate was the sole carbon source in the anaerobic incubation, the isolate did not remove phosphate . These physiological features of the isolate were similar to those of Microlunatus phosphovorus . However, unlike M . phosphovorus the P-removal ability of the isolate was relatively low and was not accelerated by repeating the anaerobic/aerobic incubation cycles . Phylogenetic analysis and comparison of several characteristics showed that the isolate was identified as Tetrasphaera elongata which was recently proposed as a new polyphosphate-accumulating species isolated from activated sludge . As the isolate contained menaquinone (MK)-8(H(4)) as the predominant isoprenoid ubiquinone, it may be significantly responsible for phosphate removal, because MK-8(H(4)) has reportedly been found in fairly high proportions in many phosphate-removing activated sludges.

Water Res, 2003 Jan, 37(1), 155 - 63
Gravitational sedimentation of flocculated waste activated sludge; Chu CP et al.; The sedimentation characteristics of flocculated wastewater sludge have not been satisfactorily explored using the non-destructive techniques, partially owing to the rather low solid content (ca . 1-2%) commonly noted in the biological sediments . This paper investigated, for the first time, the spatial-temporal gravitational settling characteristics of original and polyelectrolyte flocculated waste activated sludge using Computerized Axial Tomography Scanner . The waste activated sludge possessed a distinct settling characteristic from the kaolin slurries . The waste activated sludges settled more slowly and reached a lower solid fraction in the final sediment than the latter . Flocculation markedly enhanced the settleability of both sludges . Although the maximum achievable solid contents for the kaolin slurries were reduced, flocculation had little effects on the activated sludge . The purely plastic rheological model by Buscall and White (J Chem Soc Faraday Trans 1(83) (1987) 873) interpreted the consolidating sediment data, while the purely elastic model by Tiller and Leu (J . Chin . Inst . Chem . Eng . 11 (1980) 61) described the final equilibrated sediment . Flocculation produced lower yield stress during transient settling, thereby resulting in the more easily consolidated sludge than the original sample . Meanwhile, the flocculated activated sludge was stiffer in the final sediment than in the original sample . The data reported herein are valuable to the theories development for clarifier design and operation.

Water Res, 2003 Jan, 37(1), 11 - 20
Effect of low ORP in anoxic sludge zone on excess sludge production in oxic-settling-anoxic activated sludge process; Saby S et al.; This paper studied the effect of oxidation-reduction potential (ORP) in the anoxic sludge zone on the excess sludge production in the oxic-settling-anoxic process (OSA process), a modified activated sludge process . Two pilot-scale activated sludge systems were employed in this study: (1) an OSA process that was modified from a conventional activated sludge process by inserting a sludge holding tank or namely the "anoxic" tank in the sludge return line; and (2) a conventional process used as the reference system . Each was composed of a membrane bioreactor to serve the aeration tank and solid/liquid separator . Both systems were operated with synthetic wastewater for 9 months . During the operation, the OSA system was operated with different ORP levels (+100 to -250 mV) in its anoxic tank . It has been confirmed that the OSA system produced much less excess sludge than the reference system . A lower ORP level than +100 mV in the anoxic tank is in favor of the excess sludge reduction . When the ORP level decreased from +100 to -250 mV the sludge reduction efficiency was increased from 23% to 58% . It has also been found that the OSA system performed better than the reference system with respect to the chemical oxygen demand removal efficiency and sludge settleability . The OSA process may present a potential low-cost solution to the excess sludge problem in an activated sludge process because addition of a sludge holding tank is only needed.

Environ Toxicol Chem, 2002 Dec, 21(12), 2649 - 53
Modeling the toxicity of polar and nonpolar narcotic compounds to luminescent bacterium Shk1; Ren S et al.; Luminescent bacterium Shk1 was created for the purpose of testing and screening the toxicity of activated sludge wastewater treatment plant influent to avoid toxic shock to the wastewater treatment plant microorganisms . The toxicity of a number of organic compounds was tested using an assay employing Shk1 . Because these compounds exhibit toxicity by mechanisms of both polar and nonpolar narcosis, their toxicity cannot be properly modeled together using a quantitative structure-activity relationship model based on the logarithm of the octanol-water partition coefficient (log K(ow)) . A solvation parameter model was developed to describe and predict the nonspecific (i.e., polar and nonpolar narcosis) toxicity of organic compounds to Shk1, which does not depend on the discrimination between polar and nonpolar narcotic compounds . The statistically significant model descriptors were the McGowan's characteristic volume (V(x)) and the hydrogen-bond basicity (sigmabetaH) . The model was similar to the solvation parameter model developed for Vibrio fischeri, but it did not include an excess molar refraction (R) term.

Environ Microbiol, 2002 Nov, 4(11), 753 - 7
Diversity and distribution of a deeply branched novel proteobacterial group found in anaerobic-aerobic activated sludge processes; Kong Y et al.; A novel coccobacilli group found previously in enhanced biological phosphorus removal (EBPR) systems was further revealed to have a high degree of diversity and distribution in various activated sludge systems . Phylogenetic analysis based on 14 existing and 18 newly retrieved 16S rRNA sequences revealed that these sequences formed a novel cohesive cluster with seven subgroups in the gamma-Proteobacteria . Fluorescence in situ hybridization with a set of probes designed specifically targeting the novel group at different hierarchical levels showed that the novel group with a coccoid (2-4 micro m) to occasionally long-rod (up to 20 micro m) shape widely distributed and in some cases predominated in sludge samples taken from nine lab- and full-scale EBPR systems (10-50% of total cells) and four conventional activated sludge systems (1-10%) . Variation of predominance was also observed among those subgroups in systems showing deteriorated or effective EBPR activity.

J Appl Microbiol, 1997 Feb, 82(2), 204 - 10
Cell-surface hydrophobicity and scum formation of Rhodococcus rhodochrous strains with different colonial morphologies; Sunairi M et al.; Rhodococcus rhodochrous has been reported to be one of the micro-organisms responsible for the formation of scum which is thick and viscous biological foam in activated sludge plants . The hydrophobicity of mycolic acids present on the cell surface and the long-branched shape of the hyphae have been thought to contribute to the scum formation . Cell surface hydrophobicity and scum formation of four R . rhodochrous strains with different colony morphologies were determined, and the results showed that the two rough strains had strong cell surface hydrophobicity and produced scum, whereas the weakly hydrophobic smooth strain and the hydrophilic mucoidal strain did not . All four strains displayed long, branched hyphae, and their electrophoretic mobilities were similar, between pH 4 and 9 . These data suggest that changes in the cell surface hydrophobicity of the R . rhodochrous result in changes in the culture characteristics and the formation of scum.

Biodegradation, 2002, 13(2), 91 - 9
Biodegradation of formaldehyde and its derivatives in industrial wastewater with methylotrophic yeast Hansenula polymorpha and with the yeast-bioaugmented activated sludge; Kaszycki P et al.; Methylotrophic yeast Hansenula polymorpha were shown to cooperate with activated sludge from biological wastewater treatment stations, enhancing substantially its potential to biodegrade formaldehyde in industrial wastewater . After integration with yeast cells the modified sludge retained its original structure and activity whereas its resistance to elevated formaldehyde concentrations was significantly improved . The applicability of the yeast in the utilization of formaldehyde derivatives, as exemplified by urotropine and trioxane, was also investigated . The treatment of urotropine-containing wastewater with methylotrophic yeast was found to be effective at acidic conditions (pH below 5.5) . Trioxane was not degraded due to the stability of an ether bond which made themolecule recalcitrant to oxidation via methylotrophic pathway reactions . It is concluded that the yeast species may be applied to treat wastewater containing formaldehyde and some of its derivatives as either monocultures or as an integrated, specialized element of the activated sludge biocenosis.

Antonie Van Leeuwenhoek, 2002 Aug, 81(1-4), 665 - 80
Microbial community composition and function in wastewater treatment plants; Wagner M et al.; Biological wastewater treatment has been applied for more than a century to ameliorate anthropogenic damage to the environment . But only during the last decade the use of molecular tools allowed to accurately determine the composition, and dynamics of activated sludge and biofilm microbial communities . Novel, in many cases yet not cultured bacteria were identified to be responsible for filamentous bulking and foaming as well as phosphorus and nitrogen removal in these systems . Now, methods are developed to infer the in situ physiology of these bacteria . Here we provide an overview of what is currently known about the identity and physiology of some of the microbial key players in activated sludge and biofilm systems.

Antonie Van Leeuwenhoek, 2002 Aug, 81(1-4), 655 - 63
Understanding the diversity in catabolic potential of microorganisms for the development of bioremediation strategies; Watanabe K et al.; Molecular ecological approaches have detected diverse microorganisms that occur in response to pollution and bioremediation; however, most of these organisms have not been isolated, and their physiological traits are poorly understood . One important objective in current bioremediation studies would therefore be an assessment of the physiology and functions of the diverse microbial population at a polluted site . Among the parameters relating to the diversity of the microbial catabolic potential, e.g., substrate specificity, inducer specificity, number of catabolic routes and kinetics of catabolic enzymes, our studies have focused on the kinetic diversity of phenol-degrading bacteria . In one example, a kinetic analysis allowed functionally important phenol-degrading bacteria to be identified in activated sludge; this information could be used to improve the performance of phenol-degrading activated sludge . In an analysis of phenol-degrading bacteria present in trichloroethylene (TCE)-contaminated aquifer soil, the kinetic data could be linked to group-specific monitoring of their phenol-hydroxylase genes . The results have suggested that one group of phenol-degrading bacteria can effectively contribute to TCE bioremediation, while other groups work poorly . Based on this information, we have succeeded in developing a high-performance TCE-degrading bioreactor . We suggest that a careful analysis of the diversity of microbial catabolic potential, particularly of the kinetic traits, may facilitate the development of new bioremediation strategies.

Water Sci Technol, 2002, 46(9), 331 - 8
Performance of an extended aeration-microfiltration (EAM) reactor in treating high strength industrial wastewater; Noor MJ et al.; A laboratory study was conducted on an Extended Aeration-Microfiltration (EAM) reactor in treating a food industry wastewater . The reactor contained horizontally laid hollow fibre microfiltration (MF) units that were fully submerged . The MF units were connected to a peristaltic pump that was used to extract permeate continuously under suction pressure . Continuous aeration from beneath the modules provided the crossflow effect to the MF units . Active activated sludge was used in the start-up where the sludge was mixed together with the feed water at a Food/Microorganisms (F/M) value of about 0.1 . Primary effluent with Chemical Oxygen Demand (COD) values ranged between 1,500 and 3,000 mg/l was used as feed water . The EAM reactor was operated for nearly three months without initiating cleaning of the MF units . A suction pressure of 0.9 bar and Mixed Liquor Suspended Solids (MLSS) of over 5,500 mg/l were reached when nearing the end of the three month operation period . Permeate COD and turbidity reduction of over 97% and 99% respectively, were achieved . Prior to this, the MF module arrangements were studied; where vertically arranged modules were found to perform poorly as compared to the horizontally laid modules, in terms of clean water permeate flux.

Water Sci Technol, 2002, 46(9), 229 - 36
Effect of important operational parameters on performance of coarse pore filtration activated sludge process; Alavi Maghaddam MR et al.; A coarse pore filter can be applied inside the aeration tank instead of sedimentation tank for liquid separation from the sludge . It has pores, which are irregular in shape, and much bigger than micro-filtration membrane pores in size . The objective of the study was to investigate the effect of important operational parameters such as flux, aeration intensity, and solid retention time (SRT) on the performance of the coarse pore filtration activated sludge process . The effect of these parameters was studied in laboratory scale experiments . It was found that the flux had a significant role in the effluent quality of this system . The effluent SS and turbidity were not changed significantly at different aeration intensities . Three SRTs, 10, 30 and longer days (without excess sludge) were used for three reactors to check the effect of this parameter on the system performance . The results of the reactors with SRTs about 10 and 30 days have shown very good effluent quality without any filter clogging for more than 4 months operation . For the reactor with long SRT, the filter clogging was observed after about 80 days of operation, which caused the increase of the operation pressure and deterioration in the effluent quality for a few days.

Water Sci Technol, 2002, 46(9), 219 - 27
Sequencing batch reactor treatment of tannery wastewater for carbon and nitrogen removal; Murat S et al.; The paper evaluates the organic carbon and nitrogen removal performance of the sequencing batch reactor (SBR), technology for tannery wastewater . For this purpose, a pilot-scale SBR was installed on site to treat the plain-sealed tannery effluent . The study involved wastewater characterization, start-up and operation of the reactor for carbon and nitrogen removal and model evaluation of system performance . Its removal efficiency was compared with that of the existing continuous-flow activated sludge system providing full treatment to wastewater from the Istanbul Tannery Organized Industrial District.

Arch Environ Contam Toxicol, 2003 Jan, 44(1), 7 - 16
Reduced antimicrobial potencies of oxytetracycline, tylosin, sulfadiazin, streptomycin, ciprofloxacin, and olaquindox due to environmental processes; Halling-Sorensen B et al.; The stability of oxytetracycline (OTC), tylosin (TYL), sulfadiazin (SDZ), streptomycin (ST), ciprofloxacin (CF) and olaquindox (O) was examined in environmentally relevant matrices, such as soil interstitial water and sewage sludge water . Compounds were assessed in both aerobic (OTC, TYL, SDZ, ST, and CF) and anaerobic experiments (OTC, TYL, and O) using analytical measurements (UV spectrophotometry or HPLC) combined with a growth inhibition pour plate assay using activated sludge bacteria . (OTC was additionally assessed using a soil bacterial assay.) This combination of results enabled the assessment of whether a loss in antibacterial potency was reflected in a similar reduction of substance concentration . If a potency reduction is not reflected in a decreased substance concentration, the results may indicate the formation of less potent degradation products possessing the same chromophoric system (same UV absorbance maximum) as the parent compound . With the exception of ST and CF, the antimicrobial agents generally lost a considerable amount of their antimicrobial potency in aerobic experiments . In the anaerobic experiments having either an experimental duration of 21 or 100 days only OTC retained potency . These results correspond well with the fact that several degradation products were encountered in the study for this compound

Environ Sci Technol, 2002 Nov 1, 36(21), 4698 - 704
Bioaugmenting bioreactors for the continuous removal of 3-chloroaniline by a slow release approach; Boon N et al.; The survival and activity of microbial degradative inoculants in bioreactors is critical to obtain successful biodegradation of non- or slowly degradable pollutants . Achieving this in industrial wastewater reactors is technically challenging . We evaluated a strategy to obtain complete and stable bioaugmentation of activated sludge, which is used to treat a 3-chloroaniline (3-CA) contaminated wastewater in a lab-scale semi-continuous activated sludge system . A 3-CA metabolizing bacterium, Comamonas testosteroni strain I2, was mixed with molten agar and encapsulated in 4 mm diameter open-ended silicone tubes of 3 cm long . The tubes containing the immobilized bacteria represented about 1% of the volume of the mixed liquor . The bioaugmentation activity of a reactor containing the immobilized cells was compared with a reactor with suspended I2gfp cells . From day 25-30 after inoculation, the reactor with only suspended cells failed to completely degrade 3-CA because of a decrease in metabolic activity . In the reactors with immobilized cells, however, 3-CA continued to be removed . A mass balance indicated that ca . 10% of the degradation activity was due to the immobilized cells . Slow release of the growing embedded cells from the agar into the activated sludge medium, resulting in a higher number of active 3-CA-degrading I2 cells, was responsible for ca . 90% of the degradation . Our results demonstrate that this simple immobilization procedure was effective to maintain a 3-CA-degrading population within the activated sludge community.

Biotechnol Bioeng, 2003 Jan 5, 81(1), 92 - 105
Metabolic model for glycogen-accumulating organisms in anaerobic/aerobic activated sludge systems; Zeng RJ et al.; Glycogen-accumulating organisms (GAO) have the potential to directly compete with polyphosphate-accumulating organisms (PAO) in EBPR systems as both are able to take up VFA anaerobically and grow on the intracellular storage products aerobically . Under anaerobic conditions GAO hydrolyse glycogen to gain energy and reducing equivalents to take up VFA and to synthesise polyhydroxyalkanoate (PHA) . In the subsequent aerobic stage, PHA is being oxidised to gain energy for glycogen replenishment (from PHA) and for cell growth . This article describes a complete anaerobic and aerobic model for GAO based on the understanding of their metabolic pathways . The anaerobic model has been developed and reported previously, while the aerobic metabolic model was developed in this study . It is based on the assumption that acetyl-CoA and propionyl-CoA go through the catabolic and anabolic processes independently . Experimental validation shows that the integrated model can predict the anaerobic and aerobic results very well . It was found in this study that at pH 7 the maximum acetate uptake rate of GAO was slower than that reported for PAO in the anaerobic stage . On the other hand, the net biomass production per C-mol acetate added is about 9% higher for GAO than for PAO . This would indicate that PAO and GAO each have certain competitive advantages during different parts of the anaerobic/aerobic process cycle .

Water Res, 2002 Oct, 36(17), 4406 - 14
Estimating the toxicities of organic chemicals to bioluminescent bacteria and activated sludge; Ren S et al.; Toxicity assays based on bioluminescent bacteria have several advantages including a quick response and an easily measured signal . The Shk1 assay is a procedure for wastewater toxicity testing based on the bioluminescent bacterium Shk1 . Using the Shk1 assay, the toxicity of 98 organic chemicals were measured and EC50 values were obtained . Quantitative structure-activity relationship (QSAR) models based on the logarithm of the octanol-water partition coefficient (log(Kow)) were developed for individual groups of organic chemicals with different functional groups . The correlation coefficients for different groups of organic compounds varied between 0.69 and 0.99 . An overall QSAR model without discriminating the functional groups, which can be used for a quick estimate of the toxicities of organic chemicals, was also developed and model predictions were compared to experimental data . The model accuracy was found to be one order of magnitude from the observed values.

Water Res, 2002 Nov, 36(18), 4643 - 7
Off-line particle size analysis of digested sludge; Houghton JI et al.; Particle size analysis was carried out on six samples of digested sludge using laser diffraction . The digested sludge was produced in laboratory-scale reactors under different feed regimes based on a mixture of primary and waste activated sludge (WAS) . Laser diffraction proved capable of providing rapid, reproducible results of the particle size distribution of each sample, and highlighted differences between the different treatments . An increase in the level of WAS in the digester feed sludge led to a shift in the size distribution, with a decrease in the number of smaller sized particles.

Water Res, 2002 Nov, 36(18), 4636 - 42
Aminopolyphosphonate removal during wastewater treatment; Nowack B; Phosphonates are used in large quantities in industry and household products as scale inhibitors and chelating agents . They are not biodegraded during wastewater treatment but are removed by adsorption processes . Field measurements from different wastewater treatment plants affirm that they are removed almost completely during wastewater treatment . Adsorption of nitrilotrismethylenephosphonic acid onto activated sludge, amorphous iron oxide and humic acids (HAs) was studied under controlled conditions . The adsorption onto HAs decreases sharply with increasing pH with negligible adsorption at pH above 6.5 . Adsorption onto amorphous iron oxide follows a Langmuir behavior . The presence of 1 mM Ca doubles the maximum surface capacity at pH 7 . Adsorption onto activated sludge is not very pH sensitive and is explained to a large extent by adsorption onto amorphous iron oxides, but the contribution of organic matter or other mineral phases cannot be ruled out.

Water Environ Res, 2002 Jul-Aug, 74(4), 354 - 61
Physical enrichment of polyphosphate-accumulating organisms in activated sludge; Hung CH et al.; Two methods that physically separate polyphosphate-accumulating organisms (PAO) from other organisms in activated sludge were developed . The first method used 4'6-diamidino-2-phenylindole dihydrochloride (DAPI) to selectively stain PAO . When excited with light at 340 nm, polyphosphate granules in DAPI-stained cells fluoresce yellow while cells without polyphosphate fluoresce blue . This difference in fluorescent response was used to separate PAO from non-PAO using flow cytometry . The second method consisted of a simple gradient centrifugation to physically separate PAO from non-PAO based on their density differences . Both methods produced cell suspensions with an increased PAO concentration . From an average PAO concentration of approximately 14% in a full-scale process, the DAPI-flow cytometry method produced sorted samples with PAO representing more than 70% of the total cells, while the density gradient method produced an approximate 43 to 48% PAO enrichment . The physical enrichment methods described herein should facilitate the identification and study of PAO that are relevant in full-scale enhanced biological phosphorus removal processes.

Water Res, 2002 Sep, 36(16), 4113 - 27
Practical identifiability of ASM2d parameters--systematic selection and tuning of parameter subsets; Brun R et al.; In many applications, some parameters of the Activated Sludge Model No . 2d (ASM2d) need calibration . Since ASM2d usually is overparameterized with respect to the available data, the subset of calibration parameters is not unique . In practice, calibration of ASM2d (and other ASMs) is often addressed by ad hoc selecting and tuning procedures . In this paper, a more systematic approach based on parameter identifiability analysis of parameter subsets is applied . The approach consists of a preliminary prior parameter analysis and a subsequent iterative parameter subset selection and tuning procedure . The former includes the choice of suitable prior parameter values and uncertainties and a pre-selection of parameters which are reasonably estimated from the data available . The latter is based on three diagnostic measures which are simple to calculate and easy to interpret . It is demonstrated as to how these measures can be used to identify the most important model parameters and to analyze their interdependencies . In addition, it is shown how these measures facilitate the analysis of the influence of fixed parameter values on parameter estimates.

Water Res, 2002 Sep, 36(16), 3965 - 70
Bacteria and fungi in aerosols generated by two different types of wastewater treatment plants; Bauer H et al.; Raw wastewater is a potential carrier of pathogenic microorganisms and may pose a health risk when pathogenic microorganisms become aerosolized during aeration . Two different types of wastewater treatment plants were investigated, and the amounts of cultivable bacteria and fungi were measured in the emitted aerosols . Average concentrations of 17,000 CFU m(-3) of mesophilic, 2,100 CFU m(-3) of TSA-SB bacteria (bacteria associated with certain waterborne virulence factors), 1700 CFU m(-3) of mesophilic and 45 CFU m(-3) of thermotolerant fungi, were found in the aerosol emitted by the aeration tank of the activated sludge plant . In the aerosol of the fixed-film reactor 3000 CFU m(-3) mesophilic and 730CFUm(-3) TSA-SB bacteria, and 180 CFUm(-3) mesophilic and 14 CFU m(-3) thermotolerant fungi were measured . The specific emissions per population equivalent between the two types of treatment plants differed by two orders of magnitude . The microbial flux based on the open water surface area of the two treatment plants was similar . The aerosolization ratios of cultivable bacteria (expressed as CFU m(-3) aerosol/m(-3) wastewater) ranged between 8.4 x 10(-11) and 4.9 x 10(-9) . The aerosolization ratio of fungi was one to three orders of magnitude higher and a significant difference between the two types of treatment plants could be observed.

Arch Environ Contam Toxicol, 2002 Nov, 43(4), 425 - 31
Biodegradability assessment of ozonated raw and biotreated pharmaceutical wastewater; Arslan-Alaton I et al.; The activated sludge specific oxygen uptake rate (SOUR) and BOD(5)/COD ratios of biologically pretreated pharmaceutical wastewater were analyzed and compared to assess relative changes in biotreatability during ozonation at a rate of 7.4 g/(L x h) for 4 h . An appreciable COD removal (41%) was achieved by the initial biological treatment process, whereas ozonation was more effective in reducing the UV-sensitive aromatic compounds present in the pretreated effluent . Sequential treatment using activated sludge + ozonation processes resulted in an average COD removal efficiency of 48%, and a proceeding biotreatment stage increased the overall COD removal to 53% . An optimum ozone dose in the range of 1,854-3,708 mg/L corresponding to a specific ozone input rate of 0.23-0.46 mg O(3)/mg COD(o) existed where SOUR (3.7 x 10(-3) mg O(2)/{mg MLSS x min} for ozonation at pH 8) and BOD(5)/COD (0.57) as well as the proceeding biological COD removal yield Y(COD) (average 8 mg COD/mg MLSS) exerted maximum values.

Lett Appl Microbiol, 2002, 35(5), 439 - 45
Aggregation of immobilized activated sludge cells into aerobically grown microbial granules for the aerobic biodegradation of phenol; Jiang HL et al.; AIMS: The aim of this study is to evaluate the utility of aerobically grown microbial granules for the biological treatment of phenol-containing wastewater . METHODS AND RESULTS: A column-type sequential aerobic sludge blanket reactor was inoculated with activated sludge and fed with phenol as the sole carbon source, at a rate of 1.5 g phenol l-1 d-1 . Aerobically grown microbial granules first appeared on day 9 of reactor operation and quickly grew to displace the seed flocs as the dominant form of biomass in the reactor . These granules were compact and regular in appearance, and consisted of bacterial rods and cocci and fungi embedded in an extracellular polymeric matrix . The granules had a mean size of 0.52 mm, a sludge volume index of 40 ml g-1 and a specific oxygen utilization rate of 110 mg oxygen g VSS-1 h-1 (VSS stands for volatile suspended solids) . Specific phenol degradation rates increased with phenol concentration from 0 to 500 mg phenol l-1, peaked at 1.4 g phenol g VSS-1 d-1, and declined with further increases in phenol concentration as substrate inhibition effects became important . CONCLUSIONS: Aerobically grown microbial granules were successfully cultivated in a reactor maintained at a loading rate of 1.5 g phenol l-1 d-1 . The granules exhibited a high tolerance towards phenol . Significant rates of phenol degradation were attained at phenol concentrations as high as 2 g l-1 . SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to demonstrate the ability of aerobically grown microbial granules to degrade phenol . These granules appear to represent an excellent immobilization strategy for microorganisms to biologically remove phenol and other toxic chemicals in high-strength industrial wastewatersPublication Types:

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