Activated sludge

Water Sci Technol, 2002, 45(12), 119 - 26
PHA (polyhydroxyalkanoate) production potential of activated sludge treating wastewater; Takabatake H et al.; The main purposes of wastewater treatment systems are to remove organic pollutants, but it would be very attractive if there were a way to recover the organic pollutants as valuable organic materials . One of the possible ways to recover organic pollutants in wastewater is to convert them into polyhydroxyalkanoates (PHAs), which are biodegradable plastics . In this study, 18 activated sludge samples in 4 wastewater treatment plants (WWTPs) in Tokyo, Japan, were evaluated for their potential to produce PHAs by aerobic batch experiments with excess supply of acetate as the sole carbon source . The activated sludge samples tested had the capability to accumulate PHA up to 18.8% of dry cell weight on average, with the range of 6.0% to 29.5% . The results showed that the maximum PHA content was dependent on the influent more than on the operational conditions of the activated sludge, and that conventional activated sludge produced PHA as much as anaerobic-aerobic activated sludge did . The PHA content achieved in this study is still low, and further improvement is needed to put into practice the recovery process of organic pollutants as biodegradable plastics by activated sludge.

Appl Environ Microbiol, 2002 Sep, 68(9), 4629 - 36
Abundance and phylogenetic affiliation of iron reducers in activated sludge as assessed by fluorescence in situ hybridization and microautoradiography; Nielsen JL et al.; Microautoradiography (MAR) was used to enumerate acetate-consuming bacteria under Fe(III)-reducing conditions in activated sludge . This population is believed to consist of dissimilatory iron-reducing bacteria, because the applied incubation conditions and the use of specific inhibitors excluded consumption of radiolabeled acetate by other physiological groups such as sulfate reducers . By use of this approach, dissimilatory iron reducers were found in a concentration of 1.1 x 10(8) cells per ml, corresponding to approximately 3% of the total cell count as determined by DAPI (4',6'-diamino-2-phenylindoledihydrochloride-dilactate) staining . The MAR enumeration method was compared to the traditional most-probable-number (MPN) method (FeOOH-MPN) and a modified MPN method, which contains Ferrozine directly within the MPN dilutions to determine the production of small amounts of ferrous iron (Ferrozine-MPN) . The Ferrozine-MPN method yielded values 6 to 10 times higher than those obtained by the FeOOH-MPN method . Nevertheless, the MAR approach yielded counts that were 100 to 1,000 times higher than those obtained by the Ferrozine-MPN method . Specific in situ Fe(III) reduction rates per cell (enumerated by the MAR method) were calculated and found to be comparable to the respective rates for pure cultures of dissimilatory iron-reducing bacteria, suggesting that the new MAR method is most reliable . A combination of MAR and fluorescence in situ hybridization was used for phylogenetic characterization of the putative iron-reducing bacteria . All activated-sludge cells able to consume acetate under iron-reducing conditions were targeted by the bacterial oligonucleotide probe EUB338 . Around 20% were identified as gamma Proteobacteria, and 10% were assigned to the delta subclass of Proteobacteria.

Anal Bioanal Chem, 2002 Apr, 373(8), 704 - 9 Epub 2002 Jul 25.
Analysis and toxicity of methomyl and ametryn after biodegradation; Farre M et al.; The controlled biodegradation of ametryn and methomyl has been performed, in accordance with the OECD Zahn-Wellens/EMPA procedure, by use of an enriched mixture of activated sludge collected from three domestic waste-water-treatment plants (WWTP) . During the process concentrations of ametryn and methomyl in the water samples were isolated by solid-phase extraction (SPE); recovery rates were 98.9 and 93.2 for methomyl and ametryn, respectively . Liquid chromatography-mass spectrometry (LC-MS) was used to determine final pesticide concentrations and for metabolite identification.The efficiency of aerobic biodegradation of ametryn and methomyl was evaluated by measuring both the decrease in the concentration of the pesticides and global properties such as the chemical oxygen demand (COD) . The acute toxicity of ametryn and methomyl was evaluated by use of the ToxAlert100 biological test, which is based on inhibition of the bioluminescence of Vibrio fischeri . There was significant correlation between results from primary and ultimate biodegradation and those from determination of toxicity . Pesticide concentrations were always reduced to below the limit of detection in less than 17 days . High COD removal (90-96%) was achieved in 28 and 18 days for methomyl and ametryn, respectively.

Water Res, 2002 Jul, 36(13), 3378 - 86
Biodegradation of oxo-alcohol ethoxylates in the continuous flow activated sludge simulation test; Szymanski A et al.; Biodegradation of two alpha-methyl branched oxo-alcohol ethoxylates (OAE) of different polydispersity: LIAL 125/14 BRD (LIALB) (broad M.W . distribution) and LIAL 125/14 NRD (LIALN) (narrow M.W . distribution), both having an average of 14 oxyethylene subunits (EO) and a C(12-15) alkyl moiety were tested under the continuous flow activated sludge conditions of the classical Husmann plant . Primary biodegradation and concentration of metabolites: free oxo-alcohol fraction (FOA) and poly(ethylene glycols) (PEG), were measured . PEG were divided into two fractions: short-chained PEG (PEGshch) (1-4 EO) and long-chained PEG (PEGlch) (>4 EO) . The indirect tensammetric technique combined with an adequate separation was used for analysis . Central fission was found to be a highly dominating pathway, as is the case with fatty alcohol ethoxylates . OAE are highly primarily biodegraded (above 95%) . High concentrations of FOA and PEG are formed . Once formed the PEGlch are further fragmented into the PEGshch . Free alcohol fraction compounds are biodegraded sooner when alkyl moiety is shorter . OAE polydispersity has an influence on the kinetics of biodegradation; PEG formed from LIALN are biodegraded slower and to a lower degree than those from LIALB.

Water Res, 2002 Jul, 36(13), 3364 - 70
Bacteriophages isolated from activated sludge processes and their polyvalency; Khan MA et al.; In this study, bacteriophages were isolated from activated sludge and their host range was studied . Bacterial isolates were obtained from an activated sludge process treating urban sewage, and bacteriophages were obtained by plaque assay using the bacterial isolates obtained in this study as the host . Out of 15 bacteria isolated, 9 supported plaque formation . The host range test was conducted with a combination of 8 bacteriophage isolates and 9 bacterial isolates . All of the 8 bacteriophages tested were found to form plaques on more than 1 host, and 4 of them formed plaques on both gram-positive and gram-negative bacterial isolates . Three of the 8 bacteriophages failed to form plaques on their original bacterial host . The experimental result indicates that bacteriophages are an active part of the activated sludge microbial ecosystem, having a very close ecological relationship with their host bacteria.

Water Res, 2002 Jul, 36(13), 3341 - 9
Effect of chromium(VI) on bacterial kinetics of heterotrophic biomass of activated sludge; Stasinakis AS et al.; The effect of hexavalent chromium, Cr(VI), on the maximum specific growth rate, mu(m) and biomass yield, Y(H), of heterotrophic biomass was studied in batch tests conducted under high (= 10) and low (= 1.5) substrate-to-biomass ratios (S0/X0) . The effects of sludge age and biomass acclimatization to Cr(VI) on the bacterial kinetics were also studied . The mu(m) values were determined by measuring oxygen uptake rate (OUR) and volatile suspended solids (VSS) increase . Cr(VI) concentrations equal or greater than 10 mg l(-1) inhibited the growth of unacclimatized activated sludge and caused a significant decrease in mu(m) and Y(H) values . The acclimatization of biomass and the selection of a high operating sludge age reduced the inhibitory effect of Cr(VI) . At a sludge age of 20 days, Cr(VI) concentrations of <10 mg l(-1) stimulated bacterial growth as evidenced by an increase in both the mu(m) and Y(H) values . Determining mu(m) values by OUR and VSS methods, revealed that the presence of Cr(VI) in unacclimatized biomass caused an inhibitory effect mostly on substrate oxidation, while in acclimatized biomass, anabolic pathways were inhibited more.

Water Res, 2002 Jul, 36(13), 3245 - 52
A simple empirical model for activated sludge thickening in secondary clarifiers; Giokas DL et al.; A simple empirical model for the thickening function of the activated sludge secondary clarifiers is presented . The proposed approach relies on the integration of previous models and it is based on the phenomenon of dilution of the incoming activated sludge in the feeding well of the settling tanks . The method provides a satisfactory description of sludge stratification within the clarifier . The only requirements are limited to parameters which are readily incorporated into the routine analysis performed in an activated sludge plant, thereby eliminating the need for additional experimental or computational effort . The method was tested in a full-scale activated sludge plant and it was found that it describes fairly well the return sludge concentration, the diluted sludge blanket concentration, the sludge blanket solids concentration and the sludge blanket height of full-scale secondary clarifiers.

Microb Ecol, 2002 Jul, 44(1), 69 - 77 Epub 2002 Apr 04.
Enhanced phosphate uptake and polyphosphate accumulation in Burkholderia cepacia grown under low pH conditions; Mullan A et al.; Of bacterial cells in a sample of activated sludge, 34% contained detectable intracellular polyphosphate inclusions following Neisser staining, when grown on glucose/mineral salts medium at pH 5.5; at pH 7.5 only 7% of cells visibly accumulated polyphosphate . In a sludge isolate of Burkholderia cepacia chosen for further study, maximal removal of phosphate and accumulation of polyphosphate occurred at pH 5.5; levels were up to 220% and 330% higher, respectively, than in cells grown at pH 7.5 . During the early stationary phase of growth at pH 5.5 a maximum level of intracellular polyphosphate that comprised 13.6% of cellular dry weight was reached . Polyphosphate kinase activity was detected in actively growing cells only when cultured at pH 5.5 . The phenomenon of acid-stimulated phosphate uptake and polyphosphate accumulation in this environmental bacterial population parallels observations previously made by us in the yeast Candida humicola and may thus represent a widespread microbial response to low external pH values.

Microbiology, 2002 Aug, 148(Pt 8), 2299 - 307
Functional analysis of microbial communities in aerobic-anaerobic sequencing batch reactors fed with different phosphorus/carbon (P/C) ratios; Kong YH et al.; Fluorescence in situ hybridization (FISH) was used to analyse the community composition of a sequencing batch reactor (SBR) operating with aerobic-anaerobic cycling and fed acetate as its sole carbon source . Phosphorus was removed from the SBR microbiologically . Marked shifts in the community structure occurred as the phosphorus/carbon (P/C) ratio in the feed was changed . When the P/C ratio was shifted from 1:10 to 1:50, FISH analysis showed that the percentage of beta-Proteobacteria fell from ca 77% of the total bacteria to ca 38% . This decrease in the beta-Proteobacteria coincided with a reduction in both the proportions of the beta-proteobacterial Rhodocyclus-related phosphorus-accumulating bacteria and the biomass phosphorus content . FISH/microautoradiography and FISH/poly beta-hydroxyalkanoate (PHA) staining showed that the Rhodocyclus-related bacteria assimilated acetate and synthesized PHAs anaerobically, and that they accumulated phosphorus aerobically . No Acinetobacter spp . could be detected in any of the communities, casting further doubt on their role in phosphorus-removing activated sludge systems . As the feed P/C ratio decreased there was a corresponding increase in the proportion of alpha-Proteobacteria and, to a smaller extent, in the proportion of gamma-Proteobacteria; both the alpha- and gamma-Proteobacteria consisted mostly of tetrad-forming cocci, fitting the description of the so-called 'G-bacteria' morphotype . The change in the proportions of Proteobacteria present paralleled increases in the biomass glycogen content . Both the alpha- and beta-proteobacterial 'G-bacterial' populations assimilated acetate and synthesized PHA anaerobically . The alpha-Proteobacteria are considered responsible for glycogen production in these SBR systems.

Appl Microbiol Biotechnol, 2002 Aug, 59(4-5), 605 - 8 Epub 2002 Jun 26.
Kinetics of soluble microbial product formation in substrate-sufficient batch culture of activated sludge; Liu Y et al.; The kinetics of soluble microbial product (SMP) formation under substrate-sufficient conditions appear to exhibit different patterns from substrate-limited cultures . However, energy spilling-associated SMP formation is not taken into account in the existing kinetic models and classification of SMP . Based on the concepts of growth yield and energy uncoupling, a kinetic model describing energy spilling-associated SMP formation in relation to the ratio of initial substrate concentration to initial biomass concentration ( S(0)/ X(0)) was developed for substrate-sufficient batch culture of activated sludge, and was verified by experimental data . The specific rate of energy spilling-associated SMP formation showed an increasing trend with the S(0)/ X(0) ratio up to its maximum value . The SMP productivity coefficient ( alpha(p/e)) was defined from the model on the basis of energy spilling-associated substrate consumption . Results revealed that less than 5% of energy spilling-associated substrate consumption was converted into SMP.

Water Res, 2002 Jul, 36(12), 3110 - 20
Settling velocities and permeabilities of microbial aggregates; Li XY et al.; The hydrodynamics of microbial aggregates, including settling velocity and permeability features, were investigated through detailed settling experiments . Microbial aggregates ranging from 1.0 to 2.5 mm were generated in a lab-scale sequencing batch reactor (SBR) and also collected from a full-scale activated sludge (AS) treatment process . An apparatus of vertically connected double settling columns, filled with solutions of different densities, was used to measure the settling velocities and thus to characterise the internal permeation of individual microbial aggregates . It was demonstrated that the microbial aggregates were highly porous and fractal . However, their settling velocities observed in deionised water, EDTA and NaCl solutions were only slightly faster than predicted by Stokes' law for identical but impermeable particles . The fluid collection efficiencies calculated from measured settling velocities were less than 0.10 for most microbial aggregates, which was much lower than those previously determined for non-biological aggregates of latex microspheres . It is suggested that microbial aggregates could have a largely reduced permeability, as the pores between the microorganisms in the aggregates may be clogged by the cell's exopolymeric material with the water retained.

Water Res, 2002 Jul, 36(12), 3063 - 73
Equilibrium modelling of individual and simultaneous biosorption of chromium(VI) and nickel(II) onto dried activated sludge; Aksu Z et al.; The biosorption of chromium(VI) and nickel(II) ions, both singly and in combination, by dried activated sludge was investigated in a batch system as a function of initial pH and single- and dual-metal ion concentrations . The working initial pH values for single chromium(VI) and nickel(II) biosorptions were determined as 1.0 and 4.5, respectively . It was observed that the co-ion effect on the equilibrium uptake became more pronounced as the co-ion concentration in solution increased and pH level increased for chromium(VI) and decreased for nickel(II) . Adsorption isotherms were developed for both the single- and dual-metal ion systems at these two pH values and expressed by the mono- and multi-component Langmuir and Freundlich adsorption models and model parameters were estimated by the non-linear regression . It was seen that the mono-component adsorption equilibrium data fitted very well to both the mono-component adsorption models for both the components and the pH values studied while the multi-component Freundlich adsorption model adequately predicted the multi-component adsorption equilibrium data at moderate ranges of initial mixture concentrations for both the studied pH values.

Water Res, 2002 Jul, 36(12), 2949 - 58
A straight interpretation of the solids flux theory for a three-layer sedimentation model; Wett B; One-dimensional settling models based on the conservation law calculate the flux of particles via discrete horizontal layers . Commonly at least 10 of these spatial elements with constant volume are considered in order to achieve a satisfying fit with data . This paper deals with a conceptual approach of a simplified layer model, its theoretical confirmation and its applicability . The model differs three layers with variable volume--clarification-, hindered settling- and compression zone--which are not derived from numerical requirements but from the basic principles of solids flux theory for batch sedimentation . In accordance to the three types of propagation velocities of solids flux theory--hindered settling, signal speed and propagation of concentration discontinuities--three density layers of settling particles of a suspension have been defined . Model development has focused on a reduction of model complexity for on-line control purpose and for coupling with a biokinetic model . Another intention was the model's universal applicability to both batch and continuous settling in order to compare different types of activated sludge strategies . The model has been evaluated against the analytical solution of the flux function and against data from full-scale SBR experiments and from a secondary clarifier under hydraulic overload.

Water Res, 2002 Jul, 36(12), 2931 - 40
The shear sensitivity of activated sludge: an evaluation of the possibility for a standardised floc strength test; Mikkelsen LH et al.; The presence of micron-sized primary particles is critical in many solid/liquid separation processes, and characterisation of stability with respect to the degree of dispersion is therefore relevant . Characterisation of floc strength so far has mainly dealt with the size of flocs and not addressed quantification with respect to primary particles . In the present work floc strength was quantified in terms of the shear sensitivity (kss) as a standardised parameter based on the recent adhesion-erosion model (AE-model) . The shear sensitivity quantifies the degree of dispersion for low total solids contents and intermediate turbulent shear rates . It reflects the affinity of adhesion/erosion of primary particles to and from flocs and thus provides a means of characterising the interaction energy between the sludge colloids.

Environ Technol, 2002 Jul, 23(7), 823 - 38
Evaluating sustainable energy strategies for a water utility; Zakkour PD et al.; Research suggests that political will to deliver improvements in the quality of surface water in the UK and across the EU, alongside measures to place tighter controls on the quality of biosolids applied to agricultural land, will augment the levels of energy used in sewage and sludge treatment . This coincides with increasing concerns over the use of fossil fuel derived energy sources and their potential to enhance the Earth's greenhouse effect and promote global climate change, creating a serious paradox for these responsible for managing the aquatic environment . However, previous research also suggests that novel technologies and practices could potentially mitigate the problem in hand . This paper describes the development of a model for estimating future energy use and CO2 emissions in the wastewater treatment sector, and outlines the results of different projections using incumbent and novel practices . Indications are that using incumbent approaches could augment CO2 emissions by 15-30% in the medium- to long-term, while loss of the agricultural sludge route and deployment of an incineration strategy could mean increases are of the order of 50-70% . Alternatively, the construction of a greater number of sludge treatment facilities, with greater biogas recovery, could reduce this burden to around -8 to +7% over the same period, while the realisation of the full potential an anaerobic pre-treatment process could lead to reductions of up to 16% . Nevertheless, some of the options will come at a higher cost than incumbents, and the potential for making the business case for these investments is explored.

Environ Technol, 2002 Jul, 23(7), 747 - 55
Microbial community structures of activated sludges dominated with polyphosphate-accumulating bacteria and glycogen-accumulating bacteria; Lee TJ et al.; The microbial community structures of anaerobic-aerobic activated sludges, which are dominated with polyphosphate-accumulating bacteria (PABs) and glycogen-accumulating bacteria (GABs), were investigated by quinone profile method and dual staining DAPI (4',6-diamidino-2-phenylindol dihydrochloride) with fluorescent in situ hybridization (FISH) . For both activated sludges, the predominant bacterial groups were the beta subclass of the Proteobacteria that contained mainly Q-8 as analyzed by the quinone profile method and gram-positive bacteria with a high DNA G+C content based on FISH . A 16S rRNA-targeted oligonucleotide probe (MP2) specific for M . phosphovorus, a known polyphosphate-accumulating bacterium, was also applied to PABs and GABs-enriched activated sludge to evaluate their possible role in the enhanced biological phosphorus removal (EBPR) process . Interestingly, the bacteria that hybridized with the probe specific to M . phosphovorus in the sludge dominated with PABs represent about 6.9% of the total microorganisms . In the sludge dominated with GABs, these bacteria were about 1.9% . These results suggest its possible involvement in the EBPR process.

Ultrasonics, 2002 May, 40(1-8), 31 - 5
Ultrasonic cell disruption of stabilised sludge with subsequent anaerobic digestion; Onyeche TI et al.; The world-wide increasing environmental awareness and its subsequent regulations have led to the application of improved technologies in wastewater purification plants . This has resulted in higher wastewater and sludge productions . Sludge is the by-product of such plants and it is not only rich in organic carbon and pathogens but also in heavy metals and other environmental pollutants . In Europe, agricultural application of dried sludge (bio-solids) is confronted with negative reactions from the citizens, governmental organisations, farmers and the food industry . Ultrasonic disruption of sludge is a popular mechanical disruption process in sludge treatment . During ultrasonic treatment, high frequency acoustic signals are used to initiate the cavitation process . The applied ultrasonic field leads to a breakdown of cohesive forces of the liquid molecules resulting in the generation of cavitation bubbles . A shock wave is released by the collapse of the cavitation bubbles and propagates in the surrounding medium forming jet streams that cause the disruption of cells in sludge . Disruption of sludge cells enables the release of light organic substances into the sludge water thereby exposing them for further anaerobic digestion . This paper presents results on the disruption of conventionally stabilised sludge through the application of the ultrasonic field . In order to reduce the specific energy input (i.e . ratio of the consumed energy during ultrasonic disruption to the input sludge mass) and improve biogas production, the total solids content of the stabilised sludge was increased before disruption . The anaerobic digestion of sludge samples was carried out in a set of specially constructed laboratory anaerobic digesters . Results showed that subsequent anaerobic digestion of the ultrasonically disrupted sludge could improve biogas production with reduced sludge quantity that is vital to the economic consideration of the wastewater treatment plants . This process encourages the exploitation of valuable materials and energy from stabilised sewage sludge just before its final disposal . The negative effects of mixing disrupted sludge with its separated sludge water are also shown in this paper . This expresses the microbiological instability of the anaerobic process caused by the mixing process.

Water Environ Res, 2002 May-Jun, 74(3), 306 - 15
Investigating a mechanistic cause for activated-sludge deflocculation in response to shock loads of toxic electrophilic chemicals; Bott CB et al.; It is hypothesized that a physiological bacterial stress response mechanism, called the glutathione-gated potassium efflux system, is a significant contributor to activated-sludge deflocculation caused by shock loads of toxic electrophilic chemicals . The results show significant potassium (K+) efflux from activated sludge flocs to the bulk liquid in response to sublethal (concentrations less than that required to reduce the specific oxygen uptake rate by 50%) shock loads of chloro-2,4-dinitrobenzene, N-ethylmaleimide, 2,4-dinitrotoluene, benzoquinone, and cadmium in a bench-scale sequencing batch reactor system . Electrophile-induced K+ efflux was correlated with significant deflocculation, as measured by an increase in effluent volatile suspended solids . The K+ efflux occurred immediately (within minutes) after toxin addition and preceded the observed increase in effluent turbidity . The transport of other cations, including sodium, calcium, magnesium, iron, and aluminum, either to or from the floc structure, was negligible as compared with K+ efflux, and cell lysis was determined to be minimal at the chemical shock loads applied . The current results are the first to suggest that activated-sludge upset (i.e., deflocculation) may be caused by a specific protective stress response in bacteria.

Water Environ Res, 2002 May-Jun, 74(3), 221 - 5
Zero-valent iron pretreatment for enhancing the biodegradability of Azo dyes; Perey JR et al.; Azo dyes are a group of chemicals that are largely resistant to aerobic biodegradation and persist in wastewater treatment processes . This study proposed that zero-valent iron can be used to reduce the azo bond, cleaving the dye molecule into products that are more amenable to mineralization by bacteria in biological treatment processes such as activated sludge . Batch anaerobic reduction experiments were performed using two azo dyes, orange G and orange II, to determine reaction kinetics and to identify reduction products . Iron-treated dye solutions were subjected to batch biodegradation tests and respirometric analyses to screen for enhanced biodegradability over parent dyes . Results indicate that treatment of orange G and orange II with scrap iron produces aniline and sulfanilic acid as significant products that are degraded by an acclimated culture within 24 hours . Respirometric data illustrated that iron-treated dye solutions exert a significantly higher biochemical oxygen demand than the solutions containing orange G and orange II, demonstrating that recalcitrant azo dyes can be aerobically biodegraded after iron pretreatment.

Int J Syst Evol Microbiol, 2002 Jul, 52(Pt 4), 1141 - 4
Bacillus funiculus sp . nov., novel filamentous isolates from activated sludge; Ajithkumar VP et al.; A novel filamentous Bacillus strain, NAF001T, was reported previously that produces endospores and spore-like resting cells; the latter outgrow by budding . Phylogenetic analysis based on 16S rDNA gene sequences reported in the same paper speculated on the proposal of a novel species for this isolate . This communication describes the DNA-DNA relatedness of strain NAF001T to various members of the genus Bacillus and its whole-cell fatty acid and quinone profiles, in order to authenticate the creation of a novel species, for which the name Bacillus funiculus sp . nov . is proposed . The type strain is NAF001T (= JCM 11201T = CIP 107128T) . Further, features of the binding points between filaments of strain NAF001T that enable it to form extremely long filaments are captured by electron microscopy.

Int J Syst Evol Microbiol, 2002 Jul, 52(Pt 4), 1113 - 26
Emended description of the genus Trichococcus, description of Trichococcus collinsii sp . nov., and reclassification of Lactosphaera pasteurii as Trichococcus pasteurii comb . nov . and of Ruminococcus palustris as Trichococcus palustris comb . nov . in the low-G+C gram-positive bacteria; Liu JR et al.; Analyses of 165 rRNA gene sequences, restriction endonuclease digestion fingerprints of 16S-23S intergenic regions, DNA base compositions, fatty-acid profiles, cell-wall chemistry, cell physiology and fermentation end-product composition, along with other biochemical and phenotypic properties, supported the view that Trichococcus flocculiformis EchtT (DSM 2094T), Lactosphaera pasteurii KoTa2T (DSM 2381T), Ruminococcus palustris Z-7189T (DSM 9172T) and an isolate named 'Carnococcus allantoicus' NDP were all very similar and should be merged into a single genus . Detailed characterization of strains Ben 77, Ben 200 and Ben 201 described previously as 'Nostocoida limicola' I, a filamentous bacterium which causes bulking in activated sludge systems, revealed that these strains also belonged to the same genus as T . flocculiformis EchtT, L . pasteurii KoTa2T, R . palustris Z-7189T and 'C allantoicus' NDP . In fact, their shared properties suggested that these strains all belonged to a single species . However, DNA-DNA hybridization data indicated that T . flocculiformis EchtT, all of the 'N . limicola' I isolates and 'C allantoicus' NDP belonged to the same species, whereas L . pasteurii KoTa2T, R . palustris Z-7189T and two new isolates, 37AN3*T and 45AN2, represented three distinct species within the same genus . The priority of the genus name Trichococcus is established and since its validation predates the description of the genus Lactosphaera this name should take precedence . Under certain culture conditions, all of the strains mentioned above could produce chains of cocci . Furthermore, the morphology of T . flocculiformis EchtT could change to a non-filamentous form on certain media . This study proposes that the above strains be reclassified as members of the genus Trichococcus as four species, namely Trichococcus flocculiformis emend . (type strain EchtT = DSM 2094T), Trichococcus pasteurii comb . nov . (type strain KoTa2T = DSM 2381T = ATCC 35945T), Trichococcus collinsii sp . nov . (type strain 37AN3*T = DSM 14526T = ATCC BAA-296T, and Trichococcus palustris comb . nov . (type strain Z-7189T = DSM 9172T).

Water Res, 2002 Jun, 36(11), 2920 - 5
Color removal from cotton textile industry wastewater in an activated sludge system with various additives; Pala A et al.; The low biodegradability of many dyes and textile chemicals indicates that biological treatment is not always successful in the treatment of cotton textile wastewater, in terms of color removal . In this study, a specific organic flocculant (Marwichem DEC), powdered activated carbon (PAC), bentonite, activated clay and commercial synthetic inorganic clay (Macrosorb) were directly added into the activated sludge laboratory pilot plant model . Before dosage, the optimum sludge retention time and hydraulic retention time were determined as 30 days and 1.6 days, respectively . The Monod kinetic constants were determined as Y = 0.76 kg MLSS/kg COD, Kd = 0.026 l/day, K(S) = 113.3 mg/L, k = 0.42 l/day and mu(max) = 0.32 kg MLSS/kg COD day . Under these conditions the average COD removal was 94% and color removal was 36% . The addition of these materials did not change COD removal significantly . The most effective materials were found to be DEC and PAC for color removal . While the color removal efficiency for 120 mg/L DEC addition was 78%, it was 65% for 100 mg/L, 77% for 200 mg/L and 86% for 400 mg/L PAC addition . The advantage of DEC compared to PAC was the lower sludge production . Statistical analyses using multiple linear regression indicate that there is no relationship between the effluent color with the influent color and total suspended solids (TSS) for DEC and PAC addition . On the other hand, when only bentonite, activated clay and Macrosorb were added, the effluent color was primarily dependent on the influent color and the TSS concentration had little effect . When the data is examined by using Kruskal-Wallis H and Mann-Whitney U tests and it was found that there was a significant difference between the color data groups.

Water Res, 2002 Jun, 36(11), 2878 - 82
Fate of resin acids in pulp mill secondary treatment systems; Makris SP et al.; Profiles of resin and fatty acids (RFAs), COD, and aquatic toxicity were measured across the secondary treatment systems of three pulp mills . The RFAs sorb to suspended solids, principally fiber, and are partially removed through settling . An activated sludge system is more efficient in removing RFAs than an aerated stabilization basin (ASB) because of its higher solids level . Dehydroabietic acid accounts for a significant fraction of the effluent toxicity in the two ASBs studied . The microorganisms in an ASB are unable to respond rapidly to an RFA spill, and effluent toxicity can be elevated for a prolonged period because of hydraulic backmix . The applicability of several laboratory studies to field situations is assessed.

J Microbiol Methods, 2002 Oct, 51(2), 141 - 8
Immunomagnetic separation of scum-forming bacteria using polyclonal antibody that recognizes mycolic acids; Morisada S et al.; Mycolic acid-containing bacteria (mycolata) are thought to be involved in scum formation in aeration basins of activated sludge plants due to their ability to produce biosurfactants and their cell surface hydrophobicity . To isolate these bacteria, immunomagnetic separation (IMS) using an anti-mycolic acid polyclonal antibody was investigated . IMS that targeted Gordonia amarae SC1 exhibited a 100% recovery at 5x10(3) CFU ml(-1) . At cell concentration of 7.8x10(6) CFU ml(-1), the recovery was lowered, but 80% of cells were still captured . Effect of bead concentrations on the recovery of SC1 at 10(6) CFU ml(-1) was examined . The results showed that addition of more than 6-7x10(6) beads for 1x10(6) CFU reached a maximum recovery (83%) . Furthermore, the IMS procedure optimized with SC1 cells was tested with another mycolata . The results suggested that variation of the recovery for each mycolata is dependent on the specificity of the polyclonal antibody and that mycolata which are recognized by the antibody can be recovered by this procedure.

Environ Microbiol, 2002 Jul, 4(7), 383 - 91
In situ studies of the phylogeny and physiology of filamentous bacteria with attached growth; Thomsen TR et al.; Among the filamentous bacteria occasionally causing bulking problems in activated sludge treatment plants, three morphotypes with attached microbial growth are common, Eikelboom Type 0041, Type 1851 and Type 1701 . A better knowledge of the phylogeny and physiology of these filamentous bacteria is necessary in order to develop control strategies for bulking . In this study we have used a combination of fluorescence in situ hybridization (FISH) and microautoradiography (MAR) to investigate the identity and in situ physiology of the Type 0041-morphotype and its attached bacteria in two wastewater treatment plants . Identification and enumeration of Type 0041 using group-specific 16S rRNA-targeted FISH probes revealed that approximately 15% of the filaments hybridized with a gene probe specific for the TM7 group, a recently recognized major lineage in the bacterial domain . All other filaments morphologically identified as Type 0041 only hybridized to the general bacterial EUB338-probe, indicating that they probably do not belong to commonly isolated bacterial phyla such as the Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, for which group-specific probes were used . The phylogenetic heterogeneity of Type 0041 again highlights the inadequacy of a morphology-based classification system . Like the filaments, most of the attached microbial cells were not identified beyond their affiliation to the Bacteria using the group-specific FISH probes . However, several different bacterial phyla were represented in the identified fraction suggesting that the attached microorganisms are phylogenetically diverse . The study of the in situ physiology of Type 0041 using MAR-FISH revealed that both the filaments and the attached bacteria on Type 0041 were versatile in the use of organic substrates and electron acceptors . It was observed that all Type 0041 could consume glucose, but none of the filaments were able to consume acetate under any conditions tested, in contrast to some of the attached bacteria . No significant physiological differences were found between TM7-positive and TM7-negative Type 0041 filaments, and only minor differences were observed between the two treatment plants tested . These are the first data on the physiology of the almost entirely uncharacterized TM7 phylum and show that TM7 filamentous bacteria can uptake carbon substrates under aerobic and anaerobic conditions.

Environ Technol, 2002 Jun, 23(6), 677 - 84
Phosphorus removal and greenhouse gas N2O emission in a lime-induced aerobic sludge granule process; Wu XL et al.; Aerobic sludge granulation was achieved in an activated sludge process continuously fed with lime (Ca2+ 100 mg l(-1) influent) every other day . Eighteen days after lime addition, activated sludge granules with the size of 0.5-2.2 mm were formed, which occupied 10-25% of total sludge volume . Sludge volume index (SVI) was reduced to an average of 50 ml g(-1), which increased average sludge concentration to 3.6-5.0 g VSS l(-1), 1.6-2.1 times of that of control . Greenhouse gas N2O emission was also significantly reduced: N2O concentration from the lime-addition reactor was 5-15 ppmv, 47-61% of that of control, Effluent PO4-P concentration was generally lower than 1 mg l(-1) when average influent PO4-P concentration was 6.07-6.37 mg l(-1) . Total phosphorus (TP) and total nitrogen (TN) removal efficiencies were around 89.6% and 14.5-16.1%, over 3.5 and 1 times higher than those of control, respectively . COD removal rate in the lime-addition reactor was 2.05-2.48 kg COD m(-3) d(-1), higher than 1.34-1.61 kg COD m(-3) d(-1) in the control.

Appl Microbiol Biotechnol, 2002 Jul, 59(2-3), 361 - 7 Epub 2002 Jun 01.
Effects of 2,4-dichlorophenol on activated sludge; Sahinkaya E et al.; The effects of 2,4-dichlorophenol (2,4-DCP) on both acclimated and unacclimated activated sludge were investigated in batch reactors . The IC(50) values on the basis of maximum specific growth rate ( micro(m)), percent chemical oxygen demand (COD) removal efficiency and sludge activity were found to be 72, 60 and 47 mg l(-1), respectively, for unacclimated culture . The percent COD removal efficiencies of unacclimated culture were affected adversely, even at low concentrations, whereas culture acclimated to 75 mg 2,4-DCP l(-1) could tolerate about 200 mg 2,4-DCP l(-1)on the basis of COD removal efficiency . Although yield coefficient values of unacclimated culture increased surprisingly to very high values with the addition of 2,4-DCP, a linear decrease with respect to 2,4-DCP concentrations was observed for acclimated culture . Although no removal was observed with unacclimated culture, almost complete removal of 2,4-DCP up to a concentration of 148.7 mg l(-1) was observed with acclimated culture . It was showed that the culture could use 2,4-DCP as sole organic carbon source, although higher removal efficiencies in the presence of a readily degradable substrate were observed . Culture acclimated to 4-chlorophenol used 2,4-DCP as sole organic carbon source better than those acclimated to 2,4-DCP.

Environ Toxicol Chem, 2002 Jul, 21(7), 1338 - 49
Aquatic toxicity of triclosan; Orvos DR et al.; The aquatic toxicity of triclosan (TCS), a chlorinated biphenyl ether used as an antimicrobial in consumer products, was studied with activated-sludge microorganisms, algae, invertebrates, and fish . Triclosan, a compound used for inhibiting microbial growth, was not toxic to wastewater microorganisms at concentrations less than aqueous solubility . The 48-h Daphnia magna median effective concentration (EC50) was 390 microg/L and the 96-h median lethal concentration values for Pimephales promelas and Lepomis macrochirus were 260 and 370 microg/L, respectively . A no-observed-effect concentration (NOEC) and lowest-observed-effect concentration of 34.1 microg/L and 71.3 microg/L, respectively, were determined with an early life-stage toxicity test with Oncorhynchus mykiss . During a 96-h Scenedesmus study, the 96-h biomass EC50 was 1.4 microg/L and the 96-h NOEC was 0.69 microg/L . Other algae and Lemna also were investigated . Bioconcentration was assessed with Danio rerio . The average TCS accumulation factor over the five-week test period was 4,157 at 3 microg/L and 2,532 at 30 microg/L . Algae were determined to be the most susceptible organisms . Toxicity of a TCS-containing wastewater secondary effluent to P . promelas and Ceriodaphnia was evaluated and no observed differences in toxicity between control and TCS-treated laboratory units were detected . The neutral form of TCS was determined to be associated with toxic effects . Ionization and sorption will mitigate those effects in the aquatic compartment.

Environ Toxicol Chem, 2002 Jul, 21(7), 1323 - 9
Measurement of triclosan in wastewater treatment systems; McAvoy DC et al.; The objective of this study was to investigate the fate and removal of triclosan (TCS; 5-chloro-2-{2,4-dichloro-phenoxy}-phenol), an antimicrobial agent used in a variety of household and personal-care products, in wastewater treatment systems . This objective was accomplished by monitoring the environmental concentrations of TCS, higher chlorinated derivatives of TCS (4,5-dichloro-2-{2,4-dichloro-phenoxy}-phenol {tetra II}; 5,6-dichloro-2-{2,4-dichloro-phenoxy}-phenol {tetra III}; and 4,5,6-trichloro-2-(2,4-dichloro-phenoxy)-phenol {penta}), and a potential biotransformation by-product of TCS (5-chloro-2-{2,4-dicholoro-phenoxy}-anisole {TCS-OMe}) during wastewater treatment . These analytes were isolated from wastewater by using a C18 solid-phase extraction column and from sludge with supercritical fluid CO2 . Once the analytes were isolated, they were derivatized to form trimethylsilylethers before quantitation by gas chromatography-mass spectrometry . Recovery of TCS from laboratory-spiked wastewater samples ranged from 79 to 88% for influent, 36 to 87% for final effluent, and 70 to 109% for primary sludge . Field concentrations of TCS in influent wastewater ranged from 3.8 to 16.6 microg/L and concentrations for final effluent ranged from 0.2 to 2.7 microg/L . Removal of TCS by activated-sludge treatment was approximately 96%, whereas removal by trickling-filter treatment ranged from 58 to 86% . The higher chlorinated tetra-II, tetra-III, and penta closans were below quantitation in all of the final effluent samples, except for one sampling event . Digested sludge concentrations of TCS ranged from 0.5 to 15.6 microg/g (dry wt), where the lowest value was from an aerobic digestion process and the highest value was from an anaerobic digestion process . Analysis of these results suggests that TCS is readily biodegradable under aerobic conditions, but not under anaerobic conditions . The higher chlorinated closans were near or below the limit of quantitation in all of the digested sludge samples . Based on results from this study, the chlorinated analogues and biotransformation by-product of TCS are expected to be very low in receiving waters and sludge-amended soils.

Water Res, 2002 May, 36(9), 2288 - 96
Microbial degradation of quinoline by immobilized cells of Burkholderia pickettii; Jianlong W et al.; A quinoline-biodegrading microorganism was isolated from activated sludge of coke-oven wastewater treatment plant using quinoline as sole carbon and nitrogen source . It is a gram negative, rod-shaped and aerobic strain, which was identified as Burkholderia pickettii . The biodegradation of quinoline was carried out with this isolated strain . Analysis by high performance liquid chromatography and gas chromatography/mass spectrum (GC/MS) revealed that 2-hydroxyquinoline (2-OH-Q) was the first intermediate in the course of quinoline biodegradation . A novel immobilization carrier, that is, polyvinyl alcohol (PVA)-gauze hybrid carrier, was developed . The isolated strain was immobilized by two different immobilizing techniques and used for the quinolinerdegradation . It was found that biodegradation rate of quinoline by the microorganisms immobilized on PVA-gauze hybrid carrier was faster than that by the microorganisms immobilized in PVA gel beads . Kinetics of quinoline biodegradation by cells of Burkholderia pickettii immobilized on PVA-gauze hybrid carrier was investigated . The results demonstrate that quinoline degradation could be described by zero-order reaction rate equation when the initial quinoline concentration was in the range of 50-500 mg l(-1).

Water Res, 2002 Apr, 36(8), 2109 - 23
Improving the nitrogen removal efficiency of an A2/O based WWTP by using an on-line knowledge based expert system; Baeza JA et al.; The results obtained using an expert system to control an activated sludge process involving nutrient removal are reported . The study was conducted at a pilot plant using an Anaerobic/Anoxic/Oxic (A2/O) scheme for which a distributed control system was specially developed . The system allows various expert operational approaches to be developed with a view to minimize nitrogen levels in the outlet while using the minimum amount of energy . The proposed distributed control system is supervised by a Knowledge Based Expert System (KBES) constructed with G2 (a tool for expert system development) and permits the on-line implementation of every operating strategy of the experimental system . A set of experiments involving variable loads and flow-rates was carried out . It revealed that the amount of removed nitrogen could be increased by 11% compared to the usual operating conditions . This increase resulted in a decrease in the amount of total nitrogen and ammonium nitrogen in the outlet by 49% and 64%, respectively . These improvements were achieved with little energy cost because the performance of the treatment plant was optimised using operating rules implemented in real time.

Water Res, 2002 Apr, 36(8), 2077 - 83
Utilization of a metabolic uncoupler, 3,3',4',5-tetrachlorosalicylanilide (TCS) to reduce sludge growth in activated sludge culture; Chen GH et al.; This paper studies the feasibility of using 3,3',4',5-tetrachlorosalicylanilide (TCS) as a metabolic uncoupler to reduce the sludge growth in activated sludge cultures . The results have confirmed that TCS is an effective chemical agent in limiting the sludge growth when its concentration is >0.4 mg/L . It was demonstrated that TCS was able to reduce sludge growth rate by around 40% when the TCS concentration was 0.8mg/L . It was also revealed that substrate removal capability was not affected adversely by the presence of TCS when TCS was continuously dosed in a range of 0.5-1.0 mg/L during the 30-day operation of activated sludge batch cultures . Such a sludge growth reduction is associated with the enhancement of microbial activities and an increase in the percentage of active bacteria over the total microbial population . In the 30-day operation of the cultures, the TCS dosing at a 1-mg/L level did not undermine the treatment performance in terms of the substrate removal efficiency . This work has demonstrated that it might be feasible to apply TCS in activated sludge systems to limit the excess sludge production.

Environ Technol, 2002 May, 23(5), 547 - 51
Measuring and modelling VOC biotransformation rates; Kemp J et al.; A new protocol was used to determine biotransformation rate coefficients for volatile organic compounds in activated sludge systems . The values obtained from the protocol were compared to biotransformation rates obtained from a pilot plant . It was seen that biotransformation rates were easier to obtain from the protocol . Observations also showed that acclimation of the microorganisms to the volatile organic compounds did not change the biotransformation rates . The experimental conditions were then modelled using TOXCHEM+, a mechanistic model to predict volatile organic compound behaviour . The TOXCHEM+ predictions, using system default biotransformation rates, compared favourably with the low biotransformation rates measured by the protocol for bromoform and the chlorinated compounds, while under predicting the biotransformation rates for the non-chlorinated volatile organic compounds.

Environ Technol, 2002 Apr, 23(4), 445 - 51
Semi-continuous anaerobic co-digestion of agro-wastes; Misi SN et al.; Anaerobic digestion is a well established process for treating many types of organic waste, both solid and liquid . As such, the digestion of cattle slurries and of a range of agricultural wastes has been evaluated and has been successful . Previous batch studies have shown that multi-component mixtures of agro-wastes can be digested successfully, although with some mixtures a degree of both synergism and antagonism occurred . A continuously stirred tank reactor (15 l) was used as a mesophilic (35 degrees C) anaerobic reactor to examine the effect of treating mixtures of fruit and vegetable wastes, cattle slurry, poultry waste and waste activated sludge in which the proportions of the latter two components only were varied . The retention time was kept at 20 days and the loading rate maintained in the range 1.51-1.89 kg VS m(-3) d(-1) . Increasing the proportion of poultry waste from 0% to 100% improved the methane yield from 0.164 to 0.244 m CH4 kg(-1) VS added, and caused the VS reduction to decrease slightly . There did not appear to be any synergism or antagonism in the mixtures examined.

Environ Technol, 2002 Apr, 23(4), 363 - 72
Improvement of primary settling performance with activated sludge; Yetis U et al.; In biological treatment plants employing activated sludge processes, it is possible to recirculate some portion of the waste activated sludge that is not sent to the aeration basin, to the inlet of the primary sedimentation tanks . But in the literature there is no detailed information about the conditions, ratios and the characteristics of the waste sludge that can be recirculated back . However, depending on its settling characteristics, the addition of waste activated sludge to raw wastewater may improve primary settling . Settling tests have shown that the effect of waste activated sludge on primary settling is strongly dependent on the mean cell residence time (or sludge age), theta(c), of the waste activated sludge and also on the suspended solids concentration . Different sludge ages of 4, 6, 8, 10, 14, 20 and 26 days, and for each sludge age at least five different initial suspended solids concentrations were studied . A sludge age of 8-10 days achieved the optimum efficiency in terms of the remaining suspended solids concentration as well as percent-suspended solids removal . Also, the settled sludge volumes were measured throughout the experiments; so, the comparison was made between settled sludge volumes, initial suspended solids (SS) concentrations and theta(c).

Sci Total Environ, 2002 May 6, 290(1-3), 59 - 67
Study of the characteristics of CH4 and N2O emission and methods of controlling their emission in the soil-trench wastewater treatment process; Kong HN et al.; In recent years, worldwide concern over global warming has been expressed . It has been reported that domestic wastewater and its treatment processes are sources of CH4 and N2O, designated as greenhouse gases, the reduction of which was noted to be extremely important at the Third Conference of the Framework Convention on Climate Change (Conference Of the Parties; COP3) . Here we report a study of a field that has been unexplored until now: analytical evaluation of the properties of the emission of CH4 and N2O and methods of restricting their emission in soil-trench wastewater treatment processes, the use of which is spreading, mainly in developing nations . The results have provided the following information . A field fact-finding survey has confirmed that soil trenches emit 9.3-13.9 g CH4 m(-3) and 8.2-12.2 gN2O m(-3) in Japan, and 3.0-4.5 g CH4 m(-3) and 3.3-5.0 g N2O m(-3) in China . The emission properties widely vary according to the structure of the treatment system . The conversion ratio for nitrogen in the wastewater influent to N2O by a soil trench is between 2 and a maximum of 8%, and ranges from a few- to several 10-fold as much as that with the activated sludge method, suggesting that this can be a large source of N2O emission . It has also clearly been shown that the aerobic-anaerobic state inside the treatment system is closely related to its CH4 and N2O emission characteristics . By performing ventilation to maintain the oxidation-reduction potential (ORP) near the trench at an aerobic condition of +200 mV or more, the quantities of CH4 and N2O emitted can be reduced by as much as 50% from the levels without this ventilation, and that this can make a large contribution.

Chemosphere, 2002 May, 47(7), 765 - 75
Heavy metal extractable forms in sludge from wastewater treatment plants; Alvarez EA et al.; The analysis of heavy metals is a very important task to assess the potential environmental and health risk associated with the sludge coming from wastewater treatment plants (WWTPs) . However, it is widely accepted that the determination of total elements does not give an accurate estimation of the potential environmental impact . So, it is necessary to apply sequential extraction techniques to obtain a suitable information about their bioavailability or toxicity . In this paper, a sequential extraction scheme according to the BCR's guidelines was applied to sludge samples collected from each sludge treatment step of five municipal activated sludge plants . Al . Cd, Co, Cu, Cr, Fe, Mn, Hg, Mo, Ni, Pb, Ti and Zn were determined in the sludge extracts by inductively coupled plasma atomic emission spectrometry . In relation to current international legislation for the use of sludge for agricultural purposes none of metal concentrations exceeded maximum permitted levels . In most of the metal elements under considerations, results showed a clear rise along the sludge treatment in the proportion of two less-available fractions (oxidizable metal and residual metal).

Appl Microbiol Biotechnol, 2002 Jun, 59(1), 112 - 7 Epub 2002 Mar 28.
Aerobic degradation of 2,4,6-trichlorophenol by a microbial consortium - selection and characterization of microbial consortium; Kharoune L et al.; A microbial consortium that efficiently degrades 2,4,6-TCP (2,4,6-trichlorophenol), as the sole source of carbon and energy under aerobic conditions was selected from municipal activated sludge . Six bacterial strains, designated S(1), S(2), S(3), S(4), S(5) and S(6), were isolated from the selected consortium and five were identified as Sphingomonas paucimobilis (S(2), S(3)), Burkholderia cepacia(S(4)), Chryseomonas luteola (S(5)) and Vibrio metschnikovii (S(6)) . After prolonged cultivation followed by successive transfers, the consortium's degradation ability was improved and reached a specific degradation rate of 34 mg 2,4,6-TCP g(-1) dry weight h(-1) (about 51 mg 2,4,6-TCP g(-1) cell protein h(-1)) . The soluble chemical oxygen demand, chloride and oxygen uptake balance data clearly indicate the complete dechlorination and mineralization of 2,4,6-TCP . The consortium's activity was not inhibited by 2,4,6-TCP concentrations <or=400 mg l(-1) . The highest specific growth rate (micro(max) of 0.01 h(-1)) was achieved at 2,4,6-TCP concentration <or=200 mg l(-1), and the inhibition constant ( K(i)) was 610 mg l(-1) according to the Haldane inhibition kinetic model . An inoculum size up to 120 mg l(-1) cell dry weight is desirable in order to avoid a lag phase and to allow faster degradation of 2,4,6-TCP.

Bioresour Technol, 2002 Jun, 83(2), 131 - 8
Operational factors and nutrient effects on activated sludge treatment of Pinus radiata kraft mill wastewater; Diez MC et al.; The biodegradability of Pinus radiata bleached kraft mill wastewater by an activated sludge treatment during a period of 280 days was evaluated . The effect of varying hydraulic retention time (HRT) in the range of 48 to 4.5 h and nitrogen (N) and phosphorus (P) addition on removal of biological oxygen demand (BOD5), chemical oxygen demand (COD), suspended solids (TSS and VSS), total phenolic compounds, tannin and lignin and reduction of toxicity was investigated . Removal of BOD5 was higher than 90% when HRT varied from 16 to 6 h, but decreased when HRT was less than 6 h . Similar performance was observed for COD removal, which was about 60% when HRT was varied from 16 to 6 h . Removal of total phenolic compounds and tannin and lignin was seriously affected by HRT . N and P addition to maintaining a ratio of 100:5:0.3 provided optimal BOD5, COD and suspended solids removal when HRT varied from 16 to 7 h, and no toxicity (using Daphnia) was detected in the treated effluent . When HRT was less than 6 h, the system showed destabilisation and pH, COD, BOD5 and suspended solids removal decreased.

Int J Syst Evol Microbiol, 2002 May, 52(Pt 3), 883 - 7
Tetrasphaera elongata sp . nov., a polyphosphate-accumulating bacterium isolated from activated sludge; Hanada S et al.; A new meso-diaminopimelic acid-containing, gram-positive bacterium was isolated from an activated sludge reactor showing enhanced biological phosphorus removal activity . The isolate was an asporogenous oval to rod-shaped bacterium, but occasionally formed clumps . The Neisser staining was positive, suggesting intracellular polyphosphate granules . The isolate was an aerobic chemoheterotroph which was capable of utilizing various sugars, sugar alcohols and organic acids . It contained anteiso-C15:0, iso-C15:0, iso-C14:0 and C16:0 as the major cellular fatty acids, and menaquinone-8(H4) as the major quinone . The G+C content of the genomic DNA was 69.6 mol% . Analysis of the 16S rDNA sequence revealed that the isolate is a new member of the family Intrasporangiaceae . The closest relatives were Tetrasphaera species . On the basis of the phenotypic and phylogenetic distinctiveness of the isolate, it was concluded that the organism represents a new species in the genus Tetrasphaera, for which the name Tetrasphaera elongata sp . nov . is proposed . The type strain is strain Lp2T (= JCM 11141T = DSM 14184T).

Ecotoxicol Environ Saf, 2002 May, 52(1), 13 - 20
Studies of masculinization, detoxification, and oxidative stress responses in guppies (Poecilia reticulata) exposed to effluent from a pulp mill; Larsson DG et al.; Potential masculinization, detoxification, and oxidative stress responses were assessed in domesticated female guppies (Poecilia reticulata) exposed for 42 days to diluted effluent from a modern Swedish kraft pulp mill or a model androgen . Methyltestosterone induced male-like coloration and transformation of the anal fin into a gonopodium-like structure . The effluent did not induce any apparent changes of the anal fin morphology; however, the exposed guppies became more colored than control fish, which could be an androgenic response . A better understanding of the physiological mechanisms involved in these responses would be required for a full evaluation . Both primary effluent and effluent which had undergone activated sludge treatment caused a moderate but significant induction of hepatic ethoxyresorufin-O-deethylase (EROD) activity . However, the general toxicity of both effluents was low, as mortality was negligible even at 25% dilutions . There was a continuous production of offspring in all groups (47-62% female fry), except by methyltestosterone-treated females, which did not reproduce . There were no indications that either effluent caused oxidative stress since hepatic glutathione reductase, glutathione S-transferase and DT-diaphorase activities remained unchanged compared with controls.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2002, 37(4), 667 - 78
Influence of supplemental nutrient on aerobic decolorization of acid red 14 in activated sludge; Chen M et al.; Azo dyes are non-biodegradable in the textile effluent under aerobic condition . This study demonstrates that the addition of nutrients leads to degradation of a selected azo dye (AR14), and the major decolorization kinetic pathway of AR14 could be expressed as a pseudo first order kinetic model under the experimental conditions used in this study . An excellent correlation was obtained between the decolorization speed and additional nutrient concentration, as indicated by a coefficient of determination (r2) of 0.9899 . At a higher nutrient concentration, the relatively high color removal rate can be reached up to 92.9% in a short time . The degradation ability of azodye could be changed by supplemental nutrient . The destroy of chromophore was the first step of degradation of azo dye under the aerobic conditions, and the intermediates of the dye had significant toxic to the activated sludge, while AR14 of 150 mg/l had slight inhibitory effect on sludge respiration.

Water Sci Technol, 2002, 45(6), 187 - 98
Optimization of activated sludge designs using genetic algorithms; Doby TA et al.; We describe a framework in which a genetic algorithm (GA) and a static activated sludge (AS) treatment plant design model (WRC AS model) are used to identify low cost activated sludge designs that meet specified effluent limits (e.g . for BOD, N, and P) . Once the user has chosen a particular process (Bardenpho, Biodenipho, UCT or SBR), this approach allows the parameterizations for each AS unit process to be optimized systematically and simultaneously . The approach is demonstrated for a wastewater treatment plant design problem and the GA-based performance is compared to that of a classical nonlinear optimization approach . The use of GAs for multiobjective problems such as AS design is demonstrated and their application for reliability-based design and alternative generation is discussed.

Southeast Asian J Trop Med Public Health, 2001, 32 Suppl 2, 236 - 9
Examination for intestinal parasites and enteric bacteria in the wastewater and treated wastewater from the city of Chiang Mai, Thailand; Wongworapat K et al.; An attempt to use treated wastewater for agriculture in the Chiang Mai area was made, but the re-use process had to be performed under a condition that limited the risks liable to leave pathogens present in the water . The objective of our study was to examine the intestinal parasites and enteric bacteria in the wastewater and treated wastewater from the Chiang Mai University campus as well as the treated wastewater from the Chiang Mai municipality . The raw wastewater (RW), primary treatment effluent water (PE), treated wastewater using the activated sludge system (AS) from the Chiang Mai University campus and treated wastewater using the aerated lagoon (AL) system from the Chiang Mai municipality were examined for intestinal parasites and enteric bacteria by using the centrifugal sedimentation and conventional methods respectively . The ground water (GW) and the irrigation water (IW) were used for comparison . All kinds of water were collected and examined twice a month for 6 months (February to July 2000) . None of human intestinal parasites were found from any wastewater, whereas the RW and PE water contained hookworm larva, Ascaris egg and Taenia egg on some occasions . A small amounts of pathogenic bacteria that can cause severe diarrhea were detected . Salmonella enteritidis gr E was isolated from the AL water in April, while Vibrio cholerae type O139 was detected from the PE water in June . Some pathogenic bacteria that might cause gastroenteritis, such as Aerobacter spp, Citrobacter spp, Pseudomonas spp and Escherichia coli were also found in all kinds of water . Between the two types of treated wastewater, the bacteria found in AS water was less than that in AL water in terms of both amount and type of bacteria . The treated wastewater from the city of Chiang Mai, compared to natural water such as irrigation water, appears to be safe to use for agriculture.

J Microbiol Methods, 2002 Aug, 50(3), 273 - 82
A toxicity testing protocol using a bioluminescent reporter bacterium from activated sludge; Lajoie CA et al.; A protocol for production, storage, and use of Shock 1 (Shk1) bioreporter cells for toxicity monitoring in wastewater treatment facilities was developed . Shk1 is a bioluminescent toxicity bioreporter for activated sludge previously constructed by the incorporation of lux genes into an activated sludge microorganism.A number of factors affecting Shk1 growth and bioluminescence were examined including the growth medium, tetracycline concentration, storage conditions, and test media . Based on the results of these experiments, a toxicity testing protocol was developed that involved growth of cultures in nutrient broth with tetracycline, storage of cultures at 4 degrees C, cell activation by reinoculation into nutrient broth, and toxicity testing by cell injection into the test media . Effective use of this approach required standardized time intervals for cell growth, storage, activation and exposure in the test media.Bioluminescence from Shk1 cells was measured in nutrient broth and influent wastewater and activated sludge mixed liquor from a municipal wastewater treatment plant . Using the Shk1 toxicity testing protocol, Zn EC(50) values for bioluminescence in nutrient broth, influent wastewater, and activated sludge mixed liquor were approximately 42, 7, and 32 mg/l, respectively . Zn concentrations as low as 1 mg/l could be detected in influent wastewater . The detection limit in influent wastewater is below the Zn concentrations typically reported to affect the activated sludge process.

Appl Biochem Biotechnol, 2002 Spring, 98-100, 655 - 62
Production of specific copolymers of polyhydroxyalkanoates from industrial waste; Wong PA et al.; Polyhydroxyalkanoates, biodegradable plastics with the desired physical and chemical properties of conventional synthetic plastics, are extensively investigated . In this study, specific bacterial strains produced specific copolymers from food waste . Copolymers of HB and HV (poly{3-hydroxybutyrate-co-3-hydroxyvalerate}) were obtained using various ratios of butyric acid (C4) and valeric acid (C5) as carbon sources . The C4 to C5 ratio affected the melting points of the copolymers . Melting and glass transition temperatures and many other thermal properties are important parameters relative to in-service polymer applications . Higher ratios of butyrate to valerate gave higher melting points . When a mixed culture of activated sludge was employed to produce copolymers using food wastes as nutrients, the obtained copolymers showed various monomer compositions . Copolymers with a higher portion of HV were obtained using soy waste; copolymers with less HV were obtained using malt wastes . Pure strains, (i.e., Alcaligenes latus DSM 1122, and DSM 1124, Staphylococcus spp., Klebsiella spp.) produced specific copolymers from food waste . Only Klebsiella spp . produced different copolymers; the ratios of HB:HV were 93:7 and 79:21 from malt waste and soy waste, respectively . The other strains produced polymers of 100% HB . Selecting industrial food wastes as carbon sources can further reduce the cost of producing copolymers.

Appl Biochem Biotechnol, 2002 Spring, 98-100, 1061 - 73
Sphaerotilus natans isolated from activated sludge and its production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate); Liu K et al.; Sphaerotilus natans is a sheathed bacterium existing in the activated sludge of wastewater treatment plants . It is one of the filamentous bacteria causing the bulking and foaming difficulties of activated sludge . Isolating the strain and culturing it in an axenic environment could not only provide the metabolic knowledge of the strains that would be useful in the development of wastewater treatment methods, but also could enable us to gain an understanding of the mechanism by which poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (poly{3-HB-co-3-HV}) is produced by this strain . This article reports the screening and isolation of the strain from the activated sludge using the Nile blue staining method together with Fourier transform infrared analysis . We investigated the ability of the selected strain to produce poly(3-HB-co-3-HV) copolymer using glucose and peptone, or by adding valeric acid or sodium propionate as precursor . Proper precursor feeding could dramatically enhance its 3HV content in the copolymer P(3HB-co-3HV) . By controlling the different feeding times in fed-batch fermentation, different desired copolymers were obtained with 15, 40, and 70% 3HV mole fraction of the copolymer . Polymer properties were analyzed by gas chromatography, differential scanning calorimetry, thermo-gravimetry, and nuclear magnetic resonance analysis.

J Appl Toxicol, 2002 May-Jun, 22(3), 173 - 6
Effect of olive mill wastewaters on the oxygen consumption by activated sludge microorganisms: an acute toxicity test method; Paixao SM et al.; The test for inhibition of oxygen consumption by activated sludge (ISO 8192-1986 (E)) was evaluated as a tool for assessing, the acute toxicity of olive mill wastewaters (OMW) . According to the ISO test, information generated by this method may be helpful in estimating the effect of a test material on bacterial communities in the aquatic environment, especially in aerobic biological treatment systems . However, the lack of standardized bioassay methodology for effluents imposed that the test conditions were modified and adapted . The experiments were conducted in the presence or absence of an easily biodegradable carbon source (glucose) with different contact times (20 min and 24 h) . The results obtained showed a remarkable stimulatory effect of this effluent to the activated sludge microorganisms . In fact, the oxygen uptake rate values increase with increasing effluent concentrations and contact times up to 0.98 microl O(2) h(-1) mg(-1) dry weight for a 100% OMW sample, 24 h contact time, with blanks exhibiting an oxygen uptake rate of ca . 1/10 of this value (0.07-0.10) . It seems that the application of the ISO test as an acute toxicity test for effluents should be reconsidered, with convenient adaptation for its utilization as a method of estimating the effect on bacterial communities present in aerobic biological treatment systems .

Environ Microbiol, 2002 Mar, 4(3), 158 - 68
Occurrence and activity of Archaea in aerated activated sludge wastewater treatment plants; Gray ND et al.; The occurrence, distribution and activity of archaeal populations within two aerated, activated sludge wastewater treatment systems, one treating domestic waste and the second treating mixed domestic and industrial wastewater, were investigated by denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified ribosomal RNA gene fragments and process measurements . In the plant receiving mixed industrial and domestic waste the archaeal populations found in the mixed liquor were very similar to those in the influent sewage, though a small number of DGGE bands specific to the mixed liquor were identified . In contrast, the activated sludge treating principally domestic waste harboured distinct archaeal populations associated with the mixed liquor that were not prevalent in the influent sewage . We deduce that the Archaea in the plant treating mixed wastewater were derived principally from the influent, whereas those in the plant treating solely domestic waste were actively growing in the treatment plant . Archaeal 16S rRNA gene sequences related to the Methanosarcinales, Methanomicrobiales and the Methanobacteriales were detected . Methanogenesis was measured in activated sludge samples incubated under oxic and anoxic conditions, demonstrating that the methanogens present in both activated sludge plants were active only in anoxic incubations . The relatively low rates of methanogenesis measured indicated that, although active, the methanogens play a minor role in carbon turnover in activated sludge.

Water Res, 2002 Mar, 36(6), 1649 - 50; discussion 1651-2
Comment on "experimental analysis of centrifugal dewatering process of polyelectrolyte flocculated waste activated sludge"; Dick RI; In summary, after supernatant liquid was exhausted in the author's experiments, menisci formed, and shrinkage, not pore evacuation and drying, was the mechanism causing removal of water thereafter . Results of centrifugal filtration experiments cannot be applied to solid bowl centrifugation because solid compression conditions are quite different in the two types of machines.

Water Res, 2002 Mar, 36(6), 1493 - 502
An ATP luminescence method for direct toxicity assessment of pollutants impacting on the activated sewage sludge process; Dalzell DJ et al.; An ATP luminescence method was used to determine the toxicity of three reference toxicants to two sources of domestic activated sludge, and an activated sludge from a laboratory model plant . Repeatability in the ATP test was demonstrated for Cr (as K2Cr2O7), Zn (as ZnSO4 x 7H2O), and 3,5-dichlorophenol (3,5-DCP) using each source of activated sludge . The three sources of sludge showed sensitivity to Cr and 3,5-DCP, and insensitivity to Zn using the ATP luminescence method . Sludge source did not appear to effect test response . The toxic response to 3,5-DCP in model and domestic activated sludge was shown to be dependent on sludge solid concentration (measured as total suspended solids, gTSS(-1) . It is recommended that a standard solids concentration is used during toxicity evaluation.

Biodegradation, 2001, 12(5), 325 - 35
Bioremediation of diesel-contaminated soils: evaluation of potential in situ techniques by study of bacterial degradation; Gallego JL et al.; The development of a simple laboratory methodology allows the implementation of in situ bioremediation of polluted soils with diesel fuel . In this investigation microbiological and chemical analyses and a suitable bioreactor design, were very useful for suggesting the best ways to improve biodegradation extents in a diesel-enriched soil . Biostimulation with inorganic nitrogen and phosphorus produced the best results in a simple bioreactor, with biodegradation extents higher than 90% after 45 days . Also, the addition of activated sludge from a domestic wastewater plant increased the degradation rate to a great extent . In both cases, microbiological studies showed the presence of Acinetobacter sp . degrading most of the hydrocarbons . Simultaneously, a diesel fuel release (approximately 400,000 l) was studied . Samples taken in polluted soil and water revealed that bacteria from the genus Acinetobacter were predominant . In plate studies, Acinetobacter colonies produced a whitish substance with the characteristics of a biosurfactant . Remarkably, the presence of this product was evident at the field site, both in the riverbanks and in the physical recovery plant . The study of the similarities between laboratory results and the diesel spill site strongly suggested that natural conditions at the field site allowed the implementation of in situ bioremediation after physical removal of LNAPL (light nonaqueous-phase liquids).

J Environ Sci Health B, 2002 Jan, 37(1), 53 - 64
Toxicity and biodegradation of diamines; Kim MN et al.; Phytotoxicity and cytotoxicity of 2,4-diaminotoluene (2,4-D), 4,4'-methylenedianiline (4,4-D), and 1,6-hexanediamine (1,6-D) were investigated by observing the germination of young radish seeds and the viability of HeLa cells, respectively . 2,4-D showed the highest, 4,4-D intermediate, and 1,6-D lowest cytotoxicity . However, the phytotoxicity decreased in the order of 4,4-D > 2,4-D > 1,6-D . Contrary to the results previously reported, in the modified Sturm test the activated sludge degraded 2,4-D and 4,4-D as well as 1,6-D without any pre-acclimation . Ochrobacterium antropi was isolated for degradation of 2,4-D and 4,4-D and Pseudomonas citronellolis for 1,6-D degradation . Thielevia sp . was isolated as 2,4-D degrading fungus and Aspergillus sp . as 4,4-D and 1,6-D degrading fungus . The fungi degraded the diamines faster than the bacteria.

Water Sci Technol, 2002, 45(6), 99 - 106
Use of phosphorus release batch tests for modelling an EBPR pilot plant; Tykesson E et al.; The aim of this study was to evaluate how routinely performed phosphorus release tests could be used when modelling enhanced biological phosphorus removal (EBPR) using activated sludge models such as ASM2d . A pilot plant with an extensive analysis programme was used as basis for the simulations . Without any calibration the prediction of phosphorus removal was poor and the initial release rates from the simulations were not similar to those found from the laboratory tests . A period with low organic loading was chosen as a calibration period . In this period averages of daily influent measurements were used as influent parameters . First, calibration was performed in order to fit effluent COD and MLVSS in the sludge . Next, the phosphorus content in the sludge was decreased to the measured level by decreasing the fermentation rate . Finally, the initial phosphorus release rate was calculated from a simulated batch test and the PHA uptake rate was increased to fit this release rate with the average initial rates from laboratory batch tests performed during the period . The calibrated model was verified with data from the subsequent period where acetate was dosed.

Water Sci Technol, 2002, 45(6), 89 - 97
Wastewater COD characterization: biodegradability of physico-chemical fractions; Ginestet P et al.; Physico-chemical and biological characterization methods were applied to wastewater samples originating from 7 French WWTPs . The settleable fraction (S), unsettleable-coagulable fraction (US-C) and unsettleable-uncoagulable fraction (US-UC) were separated . Special emphasis was put on the determination of hydrolysis kinetics associated with coagulable- and settleable-fractions in order to model their behaviour in activated sludge processes, as both these fractions are influenced by the SRT . The "soluble" fraction (i.e . US-UC) was composed of readily biodegradable COD (2 to 27%), readily hydrolysable COD (37 to 90%) and inerts (2 to 47%) . The "colloidal" fraction (i.e . US-C) was composed of heterotrophic biomass (9 to 24%) and readily hydrolysable COD (6 to 82%), with the rest being inerts or very slowly biodegradable COD (0 to 70%) . The "particulate" fraction (i.e . settleable) was composed of biomass (14 +/- 6%), readily hydrolysable COD (21 +/- 14%), slowly hydrolysable COD (about 45-50%) and 15 to 20% which can be considered as inert matter (X(I)) . "Readily hydrolysable COD" was correctly modeled by a global first-order reaction . First-order constants (KH) were 9 +/- 2 d(-1) for raw-wastewater, 12 +/- 3 d(-1) for primary settled-wastewater and 16 +/- 5 d(-1) for coagulated-wastewater . "Slowly hydrolysable COD" was correctly modeled by a limited surface reaction . Concerning this fraction, the specific hydrolysis rate (kH) ranged from 0.25 to 1.05 d(-1), and the affinity constant (K(X)) ranged from 0.33 to 0.95 gCOD/gCOD based on settleable solids analysis.

Water Sci Technol, 2002, 45(6), 61 - 76
The EAWAG Bio-P module for activated sludge model No . 3; Siegrist H et al.; An additional module for the prediction of enhanced biological phosphorus removal is presented on the basis of a calibrated version of ASM3 . The module uses modified processes from ASM2d but neglects the fermentation of readily degradable substrate . Biomass decay is modeled in the form of endogenous respiration as in ASM3 . The glycogen pool and biologically induced P-precipitation is not taken into account . The module was systematically calibrated with experimental data from various batch experiments, a full-scale WWTP and a pilot plant treating Swiss municipal wastewater . A standard parameter set allowed all data to be simulated.

Water Sci Technol, 2002, 45(6), 51 - 60
Modelling wastewater transformation in sewers based on ASM3; Huisman JL et al.; A deterministic model for wastewater transformations in the sewer that includes activity in the wastewater and in the sewer wall biofilm was developed . It is based on the Activated Sludge Model No . 3 (ASM3) . The mass transfer processes in the biofilm were modelled with the effectiveness approach . This approach allowed for fast calculation, required only a limited number of parameters and gave good results . The ASM3 related parameters were calibrated and validated with laboratory experiments . An equation for the aeration of the wastewater through the water surface was determined with a method based on the inert gas sulphur hexafluoride . The other model parameters such as wall roughness, attachment of particles to the biofilm and biofilm erosion were calibrated and validated with field experiments in a main sewer . The resulting model described the oxygen concentration and wastewater respiration well . It can be easily linked for integrated urban hydrology modelling with the WWTP Activated Sludge Model and the newly proposed River Water Quality Model No . 1.

Water Sci Technol, 2002, 45(6), 41 - 9
Modelling the activated sludge flocculation process combining laser light diffraction particle sizing and population balance modelling (PBM); Nopens I et al.; A technique based on laser light diffraction is shown to be successful in collecting on-line experimental data . Time series of floc size distributions (FSD) under different shear rates (G) and calcium additions were collected . The steady state mass mean diameter decreased with increasing shear rate G and increased when calcium additions exceeded 8 mg/l . A so-called population balance model (PBM) was used to describe the experimental data . This kind of model describes both aggregation and breakage through birth and death terms . A discretised PBM was used since analytical solutions of the integro-partial differential equations are non-existing . Despite the complexity of the model, only 2 parameters need to be estimated; the aggregation rate and the breakage rate . The model seems, however, to lack flexibility . Also, the description of the floc size distribution (FSD) in time is not accurate.

Water Sci Technol, 2002, 45(6), 157 - 68
Effect of different carbon sources on aerobic storage by activated sludge; Beccari M et al.; A study of substrate removal by real activated sludge with several synthetic substrates (acetate, ethanol, glutamic acid) and wastewater (raw and filtered) was carried out . Substrate, stored compounds (polyhydroxyalkanoates, PHA and internal carbohydrates), ammonia and oxygen uptake rate (OUR) were analytically determined . Polyhydroxybutyrate (PHB) was stored when the substrate was acetate or ethanol, while no appreciable formation of storage compound was detected using glutamic acid . A low amount of PHB was also formed in tests with raw and filtered wastewater which was probably mainly due to its acetate content . As far as the sum of storage and growth (indirectly estimated through ammonia consumption) did not match the overall solids formation, other unidentified mechanisms of substrate removal were likely to occur (biosorption, accumulation and/or storage of unidentified compounds) . ASM3 and two derived models were used in the interpretation of experimental data with reference to synthetic substrates . With reference to synthetic substrates ASM3 can well describe the experimental data only assuming a stored product formation much higher than the analytically detected one, whereas the model that assumes a parallel growth and storage on the substrate can well describe the observed stored product profile only assuming a direct contribution of growth much higher than estimated from ammonia consumption . The model that assumes an accumulation/biosorption stage as first step of substrate removal can better describe the whole experimentally observed behaviour . However as well as in ASM3 this implies that some fraction of removed COD is still unidentified . With reference to real wastewater where the different phenomena were mixed up due to the presence of several substrates, the different models gave similar results.

Water Sci Technol, 2002, 45(6), 145 - 56
Error diagnostics and data reconciliation for activated sludge modelling using mass balances; Meijer SC et al.; Research on activated sludge models is mainly directed towards the reliability and estimation of model coefficients . Model calculations however, rely heavily on accurate determination of operational conditions . Accurate measurement of operational conditions and mass flows is difficult, caused by large (full-scale) process flows and the absence of reliable measurements . Therefore operational data should be verified on (gross) errors before being implemented in model studies . Calibrating a model on erroneous mass flows leads to laborious calibration procedures and moreover, unjustified adaptation of the model (kinetic and stoichiometric) parameters . Gross error detection is possible when there are more measurements than strictly required to solve a system of linear conservation relations (mass balances) . A simple method for error detection is evaluating the mass balance residuals . For over determined systems data accuracy can be improved using balancing methods (i.e . minimising balance residuals) . This is referred to as data reconciliation . A reconciled data set contains fewer errors and is exactly in line with the mass balances of the system . In this paper we describe a method for gross error detection and data reconciliation . It is shown how data reconciliation improves the accuracy of the data set and how the use of a balanced data set simplifies the model calibration procedure . This is demonstrated on the basis of a modelling study of a full-scale WWTP.

Water Sci Technol, 2002, 45(6), 13 - 23
Modelling of activated sludge processes with structured biomass; van Loosdrecht MC et al.; Bacterial communities when subjected to feast-famine conditions as occurring in many wastewater treatment systems store substrates as reserve polymers . Including storage polymers in a description of microbial growth processes makes important the choice of kinetic relations . Presently there is no sound description for the diversion of substrate towards biomass growth or substrate storage . Based on observations with pure cultures and mixed cultures growing under dynamic conditions a model is proposed to describe such behaviour . This description is based on the observation that bacteria in order to grow fast have to induce a high level of RNA and proteins in order to allow fast growth . We assume that this protein synthesising system is only induced in the presence of external substrates . Based on this assumption a model structure is proposed and evaluated . It seems that this model can predict the turnover of PHA in the cells correctly, and describes well the overall behaviour mixed culture SBR systems . However especially the growth rate in the famine phase seems to be overestimated . The model defined here is a contribution to a further development of mechanistically based models for activated sludge processes.

Water Sci Technol, 2002, 45(6), 127 - 36
A practical protocol for dynamic modelling of activated sludge systems; Hulsbeek JJ et al.; Use of dynamic simulation models has become standard practice in The Netherlands . Since the introduction around 5 years ago more then 100 full scale wastewater treatment plants have been modelled . Initially very different approaches have been used varying in calibration approach, amount of sampling and time investment . Based on the accumulated practical experiences the Dutch Foundation of Applied Water Research STOWA has stimulated the development of a protocol to aid in the set-up and calibration of models for full scale wastewater treatment plants . Herein the aim was to develop a protocol, which in practice was easy to use, minimising time and costs effort, but give a reliable and useable method . In this paper this protocol is briefly described.

Water Sci Technol, 2002, 45(6), 115 - 26
Oligonucleotide probe hybridization and modeling results suggest that populations consuming readily degradable substrate have high cellular RNA levels; Frigon D et al.; Analyses based on ribosomal RNA (rRNA)-targeted hybridization performed in our laboratory identified two types of bacterial populations: a population with a high RNA level per biomass and a population with a low level of RNA per biomass . To extend these descriptions, the diurnal dynamics of the RNA pool were monitored by rRNA-targeted oligonucleotide probe membrane hybridization . Under the typical diurnal variation in COD loading rate experienced by municipal wastewater treatment plants, the RNA level of the bacterial population with a high level of RNA per biomass varied with changes in the COD loading rate . Under the same conditions, the RNA level of the population with low RNA level per biomass remained constant . A structured biomass model was developed to describe these data . Substrate COD was divided into a readily biodegradable and a slowly biodegradable COD fraction . It was assumed that two specialized populations coexist in municipal activated sludge treatment systems . One population consumes readily degradable COD and the other consumes slowly degradable COD . According to model simulations, the population consuming readily degradable COD has a high level of RNA per biomass under variable substrate concentrations . Comparatively, the population consuming slowly degradable COD has a low level of RNA level per biomass . Furthermore, model simulations reproduced the two diurnal RNA profiles observed in a full-scale municipal activated sludge system . Therefore, we suggest that two populations can be distinguished in municipal activated sludge systems: a population consuming readily degradable substrate and a population consuming slowly degradable substrate.

Water Sci Technol, 2002, 45(6), 107 - 13
Measurement of microorganisms with PHA production capability in activated sludge and its implication in activated sludge model no . 3; Hanada S et al.; In Activated Sludge Model No.3 (ASM3), it is hypothesized that all heterotrophic microorganisms (X(H)) can store substrate . However, in reality, both microorganisms with and without substrate storage capability (X(H/STO) and X(H/S), respectively) could exist . If the ratio of X(H/STO) in activated sludge is influenced by operational and environmental conditions, kSTO (storage rate constant of heterotrophic microorganisms which is defined in ASM3) may not be a universal parameter and can change from case to case . In this study, polyhydroxyalkanoate (PHA) is assumed as the principal storage product, and the ratio of microorganisms with PHA production capability (X(H/PHA)) in various activated sludges was estimated by the dual staining of Nile Blue A (NB) and DAPI . It was shown that the ratio of X(H/PHA) in sludge varied among different municipal and laboratory activated sludges.

Water Sci Technol, 2002, 45(6), 1 - 11
Microscopic versus macroscopic biomass models in activated sludge systems; Gujer W; Today's models of activated sludge systems are based on average composition of biomass (macroscopic models) . With the introduction of cell internal storage compounds (structured biomass) in ASM2 and ASM3 cell composition influences the kinetic behavior of activated sludge . Since the kinetics of most processes is not linear, adding up the behavior of individual cells (microscopic models) does not result in the same model prediction as obtained when predictions are made with average cell composition . Based on first simple computations with microscopic models which consider up to 100,000 individual bacteria, differences in model prediction are identified . It becomes clear that kinetic parameters for lumped, macroscopic models are system specific: whereas biomass from SBR systems yields kinetic parameters suited for application in microscopic models--biomass from continuous flow systems can only be used for the calibration of macroscopic models . Application of SBR models to continuous flow systems requires the use of microscopic models.

Can J Microbiol, 2002 Mar, 48(3), 245 - 55
Detecting structural and functional differences in activated sludge bacterial communities originating from laboratory treatment of elementally and totally chlorine-free bleaching effluents; Mounteer AH et al.; The ability to differentiate functional and structural diversity of bacterial communities present in activated sludges adapted to elementally (ECF) and totally (TCF) chlorine-free bleaching effluents was evaluated . Community function was evaluated through substrate utilization patterns in BiologGN microplates, and taxonomic structure was evaluated by fluorescent in situ hybridization using probes targeting the Eubacteria; the alpha, beta, and gamma subclasses of the Proteobacteria; and gram-positive bacteria with high GC content . Over 6-week sampling periods, ECF-and TCF-adapted sludge bacterial communities presented reproducible substrate utilization patterns that through principal components (PCs) analysis, separated the ECF samples from the TCF samples . Application of the fluorescent in situ hybridization technique was complicated by the intense autofluorescence of the bleaching effluent sludge samples that interfered with detection of specific hybridization signals . The most notable difference in community structure detected using the chosen set of probes was the relatively greater proportion of cells of the alpha subclass in TCF sludge (27%) than in ECF sludge (6%) . Nonspecific hybridization with beta and gamma probes was relatively high, but both sludges appeared to have similar proportions of cells of the beta (20-22%) and gamma (11-12%) subclasses . The two sludges presented relatively few gram-positive cells with high GC content (<0.2% of eubacterial counts) . Differences in both metabolic potential and taxonomic structure of the microbial communities in the ECF- and TCF-activated sludges were detected . The kinetics of the development of these differences in treatment plants and their relationships with treatment efficiency and production process conditions should now be evaluated.

J Ind Microbiol Biotechnol, 2002 May, 28(5), 264 - 7
Cell surface hydrophobicity and mycolic acid composition of Rhodococcus strains isolated from activated sludge foam; Stratton HM et al.; The bacteria causing foaming in activated sludge plants are considered to be hydrophobic, and their hydrophobicity is assumed to be a crucial factor in their foam-forming ability . This study showed no consistent relationship between cell surface hydrophobicity (CSH), as determined by microbial adherence to hydrocarbons, of three Rhodococcus spp . isolated from activated sludge foam and their ability to produce a stable foam . There also appeared to be no correlation between the mycolic acid composition of these strains, in terms of chain length or degree of unsaturation, and either CSH or foaming ability . Zeolite and bentonite successfully prevented foaming by a Rhodococcus sp . in pure culture, which suggests that cell surface charge may also play a role in foam stabilisation.

J Appl Microbiol, 2002, 92(5), 837 - 43
Diversity of chromium-resistant and -reducing bacteria in a chromium-contaminated activated sludge; Francisco R et al.; AIMS: This study attempts to establish a relationship between the Cr(VI) resistance of the culturable microbial community and the Cr(VI) resistance and Cr(VI)-reducing ability of representative strains of each population, in order to assess whether these are exclusive characteristics of one microbial group or abilities shared among many groups . METHODS AND RESULTS: A group of 48 Cr(VI)-resistant isolates, with different colony types, was isolated from chromium-contaminated activated sludge . Sodium dodecyl sulphate-polyacrylamide gel electrophoresis protein patterns and fatty acid methyl ester analysis identified six populations, representing 54% of the isolated bacteria, as belonging to the genera Acinetobacter and Ochrobactrum . The remaining populations included strains identified as species of the beta-Proteobacteria and high G + C Gram-positive bacteria . The Cr(VI) resistance and reduction ability of the strains were tested . All but two isolates grew in the presence of 1 mmol l(-1) Cr(VI) . During enrichment, all isolates were able to survive to 2 mmol l(-1) Cr(VI) and complete Cr(VI) reduction was achieved . Representative strains of each population were able to partially reduce (5.4-39.1%) the Cr(VI) present in the growth medium . CONCLUSIONS: Most of the identified isolates have never been reported to be Cr(VI)-resistant and/or Cr(VI)-reducing strains . The mechanisms of Cr(VI) resistance and reduction may differ from group to group; therefore, it is evident that both Cr(VI) resistance and reduction are shared abilities and not an exclusive characteristic of a single group, possibly reflecting horizontal genetic transfer resulting from selective pressure in this contaminated environment . SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first study of a microbial community under chronic chromate stress and, as the success of microbial-based metal remediation technologies requires a better understanding of the microbial community and the population response to metal stress, it may contribute to the implementation of a strategy of bioremediation of chromate-contaminated environments.

J Appl Microbiol, 2002, 92(5), 828 - 36
Microbial quality of wastewater: detection of hepatitis A virus by reverse transcriptase-polymerase chain reaction; Morace G et al.; AIMS: The persistent circulation of hepatitis A virus (HAV) in the Mediterranean area suggests the need for monitoring its presence in the environment . A reverse transcriptase-polymerase chain reaction (RT-PCR) was used to detect the presence of HAV in several consecutive raw sewage and final effluent samples, collected over an 8-month period from an activated sludge treatment plant in southern Italy . METHODS AND RESULTS: Two distinct purification protocols, either based on antigen-capture with monoclonal antibody (AC) or RNA extraction, were compared . The possible influence of the antibody used in the AC phase was evaluated in preliminary experiments on HAV-spiked samples, using two different monoclonal antibodies . Hepatitis A virus RNA was detected in all but one sewage environmental sample examined . The contemporary presence of enteroviruses, reoviruses and phages was observed, while HAV growth in cell culture was hampered . CONCLUSIONS: The RT-PCR technique was confirmed to be a valuable tool for the rapid monitoring of HAV in sewage samples . In addition, this study demonstrated that application of different sample purification methods can result in different levels of sensitivity of the assay and that, in the antigen-capture method, the choice of antibody can have a crucial role . SIGNIFICANCE AND IMPACT OF THE STUDY: This work underlines the need for technical uniformity in environmental studies from different laboratories for a correct and useful comparison of the results.

Appl Biochem Biotechnol, 2001 Spring, 91-93, 515 - 24
Production of polyhydroxybutyrate by Bacillus species isolated from municipal activated sludge; Law KH et al.; Plastic wastes are considered to be severe environmental contaminants causing waste disposal problems . Widespread use of biodegradable plastics is one of the solutions, but it is limited by high production cost . Biologic wastewater treatment generates large quantities of biomass as activated sludge . Only a few reports focus on the potential of utilizing resident Bacillus species from activated sludge in polyhydroxbutyrate (PHB) production as well as the production of PHB from food wastes . They have attractive properties such as short generation time, absence of endotoxins, and secretion of both amylases and proteinases that can well utilize food wastes for nutrients, which can further reduce the cost of production of polyhydroxyalkanoates (PHAs) . Two PHA-producing strains, HF-1 and HF-2, were isolated from activated sludge . HF-1 outperformed HF-2 in terms of growth and PHB production in hydrolyzed soy and malt wastes . The isolated bacteria was characterized by DNA sequence alignment . Cell extracts of HF-1 were also compared to Bacillus megaterium cell extracts on sodium dodecyl sulfate polyacrylamide gel electrophoresis . The biopolymers accumulated were analyzed by gas chromatography, nuclear magnetic resonance, and Fourier transform infrared methods.

Appl Biochem Biotechnol, 2001 Spring, 91-93, 447 - 57
Removal and recovery of copper (II) ions by bacterial biosorption; Wong MF et al.; Studies were conducted to investigate the removal and recovery of copper (II) ions from aqueous solutions by Micrococcus sp., which was isolated from a local activated sludge process . The equilibrium of copper biosorption followed the Langmuir isotherm model very well with a maximum biosorption capacity (q(max)) of 36.5 mg of Cu2+/g of dry cell at pH 5.0 and 52.1 mg of Cu2+/g of dry cell at pH 6.0 . Cells harvested at exponential growth phase and stationary phase showed similar biosorption characteristics for copper . Copper uptake by cells was negligible at pH 2.0 and then increased rapidly with increasing pH until 6.0 . In multimetal systems, Micrococcus sp . exhibited a preferential biosorption order: Cu approximate to Pb > Ni approximate to Zn . There is virtually no interference with copper uptake by Micrococcus sp . from solutions bearing high concentrations of Cl-, SO4(2-), and NO3- (0-500 mg/L) . Sulfuric acid (0.05 M) was the most efficient desorption medium, recovering >90% of the initial copper sorbed . The copper capacity of Micrococcus sp . remained unchanged after five successive sorption and desorption cycles . Immobilization of Micrococcus sp . in 2% calcium alginate and 10% polyacrylamide gel beads increased copper uptake by 61% . Biomass of Micrococcus sp . may be applicable to the development of potentially cost-effective biosorbent for removing and recovering copper from effluents.

Appl Biochem Biotechnol, 2001 Spring, 91-93, 171 - 84
Biosorption of heavy metals by bacteria isolated from activated sludge; Leung WC et al.; Twelve aerobic bacteria from activated sludge were isolated and identified . These included both Gram-positive (e.g., Bacillus) and Gram-negative (e.g., Pseudomonas) bacteria . The biosorption capacity of these strains for three different heavy metals (copper, nickel, and lead) was determined at pH 5.0 and initial metal concentration of 100 mg/L . Among these 12 isolates, Pseudomonas pseudoalcaligenes was selected for further investigation owing to its high metal biosorption capacity . The lead and copper biosorption of this strain followed the Langmuir isotherm model quite well with maximum biosorption capacity (q(max)) reaching 271.7mg of Pb2+/g of dry cell and 46.8 mg of Cu2+/g of dry cell at pH 5.0 . Study of the effect of pH on lead and copper removal indicated that the metal biosorption increased with increasing pH from 2.0 to 7.0 . A mutual inhibitory effect was observed in the lead-copper system because the presence of either ion affected the sorption capacity of the other . Unequal inhibitions were observed in all the nickel binary systems . The increasing order of affinity of the three metals toward P . pseudoalcaligenes was Ni < Cu < Pb . The metal biosorptive potential of these isolates, especially P . pseudoalcaligenes, may have possible applications in the removal and recovery of metals from industrial effluents.

FEMS Microbiol Lett, 2002 Feb 5, 207(2), 179 - 83
Phylogeny of the filamentous bacterium Eikelboom Type 1851, and design and application of a 16S rRNA targeted oligonucleotide probe for its fluorescence in situ identification in activated sludge; Beer M et al.; Micromanipulation was used to obtain an isolate (BEN 52) of Eikelboom Type 1851 from a bulking activated sludge plant . Its 16S rDNA sequence reveals its closest relative is 'Roseiflexus castenholzii', a member of the phylum 'Chloroflexi', class 'Chloroflexi', previously called the green non-sulfur bacteria . The 16S rRNA targeted oligonucleotide probe designed for fluorescence in situ hybridisation against this sequence successfully identified filamentous bacteria with the morphological features of Type 1851 in activated sludge samples from plants in several countries and different operational configurations.

Appl Microbiol Biotechnol, 2002 Apr, 58(5), 679 - 82 Epub 2002 Feb 14.
Degradation of aniline by newly isolated, extremely aniline-tolerant Delftia sp . AN3; Liu Z et al.; A bacterial strain, AN3, which was able to use aniline or acetanilide as sole carbon, nitrogen and energy sources was isolated from activated sludge and identified as Delftiasp . AN3 . This strain was capable of growing on concentrations of aniline up to 53.8 mM (5000 mg/l) . Substituted anilines such as N-methylaniline, N, N-dimethylaniline, 2-methylaniline, 4-methylaniline, 2-chloroaniline, 3-chloroaniline, o-aminoaniline, m-aminoaniline, p-aminoaniline, and sulfanilic acid did not support the growth of strain AN3 . The optimal temperature and pH for growth and degradation of aniline were 30 degrees C and 7.0, respectively . The activities of aniline dioxygenase, catechol 2,3-dioxygenase and other enzymes involved in aniline degradation were determined, and results indicated that all of them were inducible . The K (m) and V (max) of aniline dioxygenase were 0.29 mM and 0.043 mmol/mg protein/min, respectively . The K (m) and V (max) of catechol 2, 3-dioxygenase for catechol were 0.016 mM and 0.015 mmol/mg protein/min, respectively . Based on the results obtained, a pathway for the degradation of aniline by Delftiasp . AN3 was proposed . The importance of the strain to the operation of municipal wastewater treatment plants is discussed.

Environ Technol, 2002 Feb, 23(2), 149 - 62
Impact of hydrogen peroxide oxygen transfer tests on the performance of the biological nutrient removal process; Mahendraker V et al.; Knowledge of in-process oxygen transfer is essential to the optimum design and operation of aeration systems in activated sludge processes . In this study, non-steady state H2O2 oxygen transfer tests were performed in a laboratory scale, University of Cape Town configuration biological nutrient removal process (BNR) to measure the in-process oxygen transfer rates . Given the small quantity (about 1 ml @30% concentration) of H2O2 used in the aerobic reactor with a mixed liquor volume of 161 (total system working volume of 33.65 l), no effect on the process performance itself was expected . However, the process performance data obtained indicated results to the contrary . Use of H2O2 in measuring process oxygen transfer rates may not be suitable for BNR processes, as all the major process performance indicators (carbon, nitrogen and phosphorus removal by the system and carbon uptake and phosphorus release in the anaerobic zone) were negatively affected . Evidence in thiswork leads to the conclusion that external addition of H2O2 leads to excessive production of the hydroxyl radical . Since microorganisms do not have enzyme systems capable of acting upon this additional reactive radical, it resulted in loss of process performance . It is also possible that H2O2 could have upset the normal aerobic respiration process by introducing oxidative stress conditions on the catalase, peroxidase and superoxide dismutase enzymes that deal with other oxygen radicals generated as part of the overall process of reducing oxygen to water . Any test that interferes with the system in which the test is being performed is suspect . Therefore, in light of these results, the H2O2 method to test in-process oxygen transfer should be re-evaluated.

Anal Bioanal Chem, 2002 Feb, 372(4), 569 - 75 Epub 2001 Dec 21.
Metabolites from the biodegradation of pharmaceutical residues of ibuprofen in biofilm reactors and batch experiments; Zwiener C et al.; The three metabolites hydroxyibuprofen (OH-Ibu), carboxyibuprofen (CA-Ibu), and carboxyhydratropic acid (CA-HA), also known from human metabolism of ibuprofen, could be identified in biodegradation experiments . Identification was based on EI mass spectra and comparison with literature data . Detection was performed by selective MS-MS measurements by GC-ion-trap MS and online methylation . Ibuprofen (Ibu), OH-Ibu, and CA-Ibu could be detected with a signal-to-noise ratio of 10:1 at a concentration of 2 nmol L(-1), CA-HA at 0.5 nmol L(-1) . Degradation experiments in both biofilm reactors (BFR) and batch experiments with activated sludge (BAS) reveal OH-Ibu as the major metabolite under oxic conditions, and CA-HA under anoxic conditions . CA-Ibu was found under oxic and anoxic conditions almost only in the BAS . The metabolites together do not account for more than 10% of the initial concentration of Ibu.

Water Sci Technol, 2002, 45(4-5), 69 - 76
On-line determination of nitrite in wastewater treatment by use of a biosensor; Nielsen M et al.; A newly developed biosensor for nitrite having a 90% response time of about 1 min was used to monitor nitrite concentration in activated sludge exposed to oxic/anoxic cycles . The NO2- biosensor contains bacteria that reduce NO2-, but not NO3-, to N2O that is subsequently monitored by a built-in electrochemical sensor . Nitrite plus nitrate (NOx-) was simultaneously monitored by a NOx- biosensor . The maximum operational lifetime of the NO2- biosensor was 6 weeks, but much longer lifetimes can be expected as malfunctioning by the 3 sensors used for longer periods was due to either mechanical damage or ineffective internal sterilization during the construction . Insufficiently sterilized sensors became sensitive also to NO3- after some time due to development of NO3(-)-reducing bacterial populations within the sensor . The fraction of NO2- as compared to NO3- in the activated sludge was very dependent on prehistory, actual loading, and aeration . During balanced operation with NH4+ being exhausted during the later parts of the aerobic cycle, NO2- increased in concentration up to about 50 microM during the early part of the aeration cycle until NH4+ became limiting . At that time the NO2- concentration decreased to low levels . Under some operating conditions a peak of NO2- also appeared in the beginning of the anoxic period . NO2- and NO3- were depleted simultaneously during the anoxic period.

Water Sci Technol, 2002, 45(4-5), 445 - 52
Feasibility of automatic chemicals dosage control--a full-scale evaluation; Devisscher M et al.; This contribution discusses the feasibility of automatic control for chemicals dosing in activated sludge systems . The evaluation is made on the basis of a full-scale implementation at the Lommel WWTP (Belgium) of an on-line controlled dosage system for iron chloride and external carbon source . The control laws are very simple and allow intuitive adaptation by the plant operators . The control system results in a significant reduction of the chemicals dosage, better effluent results and a lower sludge production . The implementation is furthermore cost-efficient.

Water Sci Technol, 2002, 45(4-5), 345 - 53
Optimal operation for timely adaptation of activated sludge plants to changes in the surfactant composition of wastewater; Carvalho G et al.; The composition of a textile industry wastewater is highly variable, as the industrial process has to follow fashion and season trends . Surfactants represent one of the largest COD fractions in a typical textile wastewater . Therefore, it was the aim of this paper to model the acclimatisation behaviour of an activated sludge system when subjected to composition variations in the surfactant containing feed . The model was based on data obtained in SBR experiments in which a linear alkyl ethoxylate as sole carbon source in the feed was replaced by another with a longer ethoxylate chain . A previously developed model (Fractionated Degradation Model) was applied to each of the 21 SBR cycles carried out in this study . The resulting best-fit parameters were investigated and sub-models were further developed, to create an acclimatisation model, able to predict the sludge acclimatisation level . Using the information given by this model, it was possible to propose an optimal operation scheme to pre-acclimatise the sludge before a surfactant replacement is made in the textile process . A cost analysis was carried out to compare different scenarios, with and without the application of this operation scheme . It was concluded that the proposed pre-acclimatisation process may be cost effective as compared to other scenarios if a cheap surfactant-containing product was employed.

Water Sci Technol, 2002, 45(4-5), 335 - 43
Respirometry-based on-line model parameter estimation at a full-scale WWTP; Spanjers H et al.; This paper describes part of a project to develop a systematic approach to knowledge extraction from on-line respirometric measurements in support of wastewater treatment plant control and operation . The paper deals with the following issues: (1) test of the implementation of an automatic set-up consisting of a continuous laboratory respirometer integrated in a mobile trailer with sampling and dosing equipment, and data-acquisition and communication system; (2) assessment of activated sludge/sewage characteristics from sludge respirograms by model parameter estimation; (3) comparison of the parameter estimates with regular plant data and information obtained from supplementary wastewater respirograms . The paper describes the equipment and some of its measuring results from a period of one week at a large-scale wastewater treatment plant . The measurements were evaluated in terms of the common activated sludge modelling practice . The automatic set-up allowed reliable measurements during at least one week . The data were used to calibrate two different version of the model, and independent parameter estimates were obtained.

Water Sci Technol, 2002, 45(4-5), 325 - 34
Model structure identification for wastewater treatment simulation based on computational fluid dynamics; Alex J et al.; The objective of this presented project is to use the results of an CFD simulation to automatically, systematically and reliably generate an appropriate model structure for simulation of the biological processes using CSTR activated sludge compartments . Models and dynamic simulation have become important tools for research but also increasingly for the design and optimisation of wastewater treatment plants . Besides the biological models several cases are reported about the application of computational fluid dynamics ICFD) to wastewater treatment plants . One aim of the presented method to derive model structures from CFD results is to exclude the influence of empirical structure selection to the result of dynamic simulations studies of WWTPs . The second application of the approach developed is the analysis of badly performing treatment plants where the suspicion arises that bad flow behaviour such as short cut flows is part of the problem . The method suggested requires as the first step the calculation of fluid dynamics of the biological treatment step at different loading situations by use of 3-dimensional CFD simulation . The result of this information is used to generate a suitable model structure for conventional dynamic simulation of the treatment plant by use of a number of CSTR modules with a pattern of exchange flows between the tanks automatically . The method is explained in detail and the application to the WWTP Wuppertal Buchenhofen is presented.

Water Sci Technol, 2002, 45(4-5), 217 - 26
Disturbance detection and isolation in the activated sludge process; Yoo CK et al.; This paper proposes a new fault detection and isolation (FDI) method . This method monitors the distribution of process data and detects changes in this distribution, which reflect changes in the corresponding operating condition . A modified dissimilarity index and a FDI technique are defined to quantitatively evaluate the difference between data sets . This technique considers the importance of each transformed variable in the multivariate system . The FDI technique is applied to a benchmark simulation and to data from a real wastewater treatment plant . Simulation results show that it immediately detects disturbances and automatically distinguishes between serious and minor anomalies for various types of fault . The method not only detects the disturbances, but also isolates the scale of the disturbance, facilitating the interpretation of the disturbance source . The proposed monitoring technique is found to be appropriate for analyzing the biological wastewater treatment process, which is characterized by a variety of fault and disturbance sources and non-stationary characteristics.

Water Sci Technol, 2002, 45(4-5), 159 - 66
Implementation of storage tanks on the COST 624 benchmark; Pons MN et al.; To test the improvement that can be expected in terms of effluent quality of an wastewater treatment plant by activated sludge, an equalisation tank and a storm tank, designed to damp the influent variations under different weather conditions, have been implemented in front of a benchmark plant used to evaluate control strategies . The equalisation tank improves significantly the effluent quality in any weather condition but at a high operation cost due to extra pumping, while the storm tank without by-pass improves the effluent quality in rainy periods with a small increase in cost operation over the no tank case.

Water Sci Technol, 2002, 45(4-5), 135 - 42
Control of an activated sludge process with nitrogen removal--a benchmark study; Carlsson B et al.; In this paper, a simulation benchmark of a predenitrifying activated sludge process is used to evaluate a number of control strategies . A main procedure has been to use feedforward terms that are based on simplified physical models . Important mass balance relations may then be incorporated in the control law . The nitrate level in the last anoxic zone is controlled by the dosage of an external carbon source and the nitrate level in the last aerobic zone is controlled by the internal recirculation flow rate . The ammonia level is controlled by a DO set-point controller . In order to be able to have as high a sludge level as possible without sludge escape, the sludge blanket height in the settler is controlled by the excess sludge flow rate . Compared to the default set up of the benchmark, the controllers could reduce the effluent nitrate significantly whereas the effluent ammonia was only marginally decreased . The main problem is that the aeration capacity defined in the benchmark is too low.

Water Sci Technol, 2002, 45(4-5), 101 - 7
Soft sensors for control of nitrogen and phosphorus removal from wastewaters by neural networks; Luccarini L et al.; In this paper, we describe the results of research aimed to evaluate the possibility of using a neural network (NN) model for predicting biological nitrogen and phosphorus removal processes in activated sludge, utilising oxidation reduction potential (ORP) and pH as NN inputs . Based on N and P concentrations predictions obtained via the NN, a strategy for controlling sequencing batch reactors (SBRs) phases duration, optimising pollutants removal and saving energy, is proposed . The NN model allowed us to reproduce the concentration trends (change in slope, or process end), with satisfactory accuracy . The NN results were generally in good agreement with the experimental data . These results demonstrated that NN models can be used as "soft on-line sensors" for controlling biological processes in SBRs . By monitoring ORP and pH, it is possible to recognise the N and P concentrations during different SBRs phases and, consequently, to identify the end of the biological nutrient removal processes . This information can then be used to design control systems.

Int J Syst Evol Microbiol, 2002 Mar, 52(Pt 2), 629 - 37
Emended descriptions of the genus Micrococcus, Micrococcus luteus (Cohn 1872) and Micrococcus lylae (Kloos et al . 1974); Wieser M et al.; Nine yellow-pigmented, spherical bacterial strains isolated from a medieval wall painting (strain D7), from indoor air (strains 3, 6, 7, 13C2, 38, 83 and 118) and from an activated-sludge plant (strain Ballarat) were classified by a polyphasic approach . Analyses of the 16S rRNA gene sequences of three representatives (strains D7, 118 and Ballarat) indicated that they all belong to the genus Micrococcus . The three isolates shared the highest sequence similarities with Micrococcus luteus DSM 20030T (97.9-98%), Micrococcus antarcticus AS 1.2372T (97.9-98.3%) and Micrococcus lylae DSM 20315T (97.5-97.9%) . DNA-DNA reassociation studies clearly demonstrated that all nine isolates belong to the species M . luteus . However, neither their chemotaxonomic features nor their physiological and biochemical properties were consistent with those of M . luteus DSM 20030T . In contrast to M . luteus DSM 20030T, all isolates investigated possessed MK-8(H2) as the major respiratory quinone, and strain Ballarat had an A4alpha peptidoglycan type . On the basis of analyses of their Fourier transform-infrared spectroscopy spectra, isolates D7, 3, 6, 7, 13C2, 38, 83 and 118 could be grouped into a single cluster separate from M . luteus DSM 20030T, strain Ballarat and M . lylae DSM 20315T . In addition, all these isolates could be distinguished from M . luteus DSM 20030T by their ability to assimilate D-maltose, D-trehalose, DL-3-hydroxybutyrate, DL-lactate, pyruvate and L-histidine and to hydrolyse casein . Strains D7, 3, 6, 7, 13C2, 38, 83 and 118 differed from both M . luteus DSM 20030T and strain Ballarat by their ability to assimilate acetate, L-phenylalanine, L-serine and phenylacetate . Furthermore, REP-PCR fingerprinting yielded one common band for these strains, whereas this band was not observed for M . luteus DSM 20030T, strain Ballarat or M . lylae DSM 20315T . On the basis of these data, the species M . luteus can be divided into three biovars that are distinguished by several chemotaxonomic and biochemical traits: biovar I, represented by M . luteus DSM 20030T; biovar II, represented by strains D7 (= DSM 14234 = CCM 4959), 3, 6, 7, 13C2, 38, 83 and 118; and biovar III, represented by strain Ballarat (= DSM 14235 = CCM 4960) . On the basis of the results generated in this study, emended descriptions of the genus Micrococcus and the species M . luteus and M . lylae are given.

Biotechnol Bioeng, 2002 May 5, 78(3), 333 - 8
A simple method to release polyphosphate from activated sludge for phosphorus reuse and recycling; Kuroda A et al.; In enhanced biological phosphorus removal processes, activated sludge microorganisms accumulate large quantities of polyphosphate (polyP) . It was discovered that nearly all of the polyP could be released from activated sludge simply by heating it at 70 degrees C for about 1 h . The chain length of released polyP ranged from 100 to 200 phosphate (P(i)) residues . The addition of CaCl(2) precipitated approximately 75% of the total phosphorus without pH adjustment . The formed precipitate contained more P and less Ca than typical natural phosphorite deposits . Hence, in combination with enhanced biological phosphorus removal, the present method has potential for the development of a simple process for recovering phosphorus in a reusable form from wastewater .

Environ Technol, 2002 Jan, 23(1), 67 - 72
Full-scale evaluation of a multi-component additive for efficient control of activated sludge filamentous bulking; Seka MA et al.; A multi-component additive formulated for a more efficient control of activated sludge filamentous bulking was evaluated at a full-scale treatment plant experiencing severe filamentous bulking . It was found that, besides offering an immediate improvement of sludge settling, the multi-component additive was able to eliminate the filamentous bacteria causing the bulking . Hence, contrary to ordinary additives, this novel additive yielded immediate as well as long-term improvements in sludge sedimentation upon a few additions . Preliminary lab-scale toxicity tests showed that the treatment of the sludge by the additive should not impart any toxicity to the resulting effluent.

Environ Sci Technol, 2002 Mar 1, 36(5), 1102 - 6
Removal of sulfur-organic polar micropollutants in a membrane bioreactor treating industrial wastewater; Reemtsma T et al.; While membrane bioreactors (MBR) have proven their large potential to remove bulk organic matter from municipal as well as industrial wastewater, their suitability to remove poorly degradable polar wastewater contaminants is yet unknown . However, this is an important aspect for the achievable effluent quality and in terms of wastewater reuse . We have analyzed two classes of polar sulfur-organic compounds, naphthalene sulfonates and benzothiazoles, by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS) over a period of 3 weeks in the influent and effluent of a full-scale MBR with external ultrafiltration that treats tannery wastewater . While naphthalene monosulfonates were completely removed, total naphthalene disulfonate removal was limited to about 40%, and total benzothiazoles concentration decreased for 87% . Quantitative as well as qualitative data did not indicate an adaptation to or a more complete removal of these polar aromatic compounds by the MBR as compared to literature data on conventional activated sludge treatment . While quality improvements in receiving waters for bulk organic matter are documented and the same can be anticipated for apolar particle-associated contaminants, these data provide no indication that MBR will improve the removal of polar poorly biodegradable organic pollutants.

Water Res, 2002 Mar, 36(5), 1167 - 80
Poly-beta-hydroxybutyrate metabolism in dynamically fed mixed microbial cultures; Beun JJ et al.; The kinetics of production and degradation of poly-beta-hydroxybutyrate (PHB) by a mixed activated sludge culture growing on acetate was studied in a sequencing batch reactor (SBR) . Occasionally a very high amount of acetate was added to the steady state system in order to obtain high PHB concentrations in the cells (fPHB) . This made it possible to follow PHB production and degradation over a wide range of fPHB-data (between 0 and 0.8 Cmol/Cmol) . The results were compared with data available in literature and with equations derived by metabolic modeling . This led to some remarkable observations . For the feast period, the ratio q(feast)PHB/-q(feast)Ac (specific PHB production rate over specific acetate uptake rate) was used to indicate which fraction of the substrate is stored . Experimentally and theoretically it was shown that this ratio has a constant value for dynamically fed systems operated at a sludge retention time (SRT) > 2d . This value is 0.6 Cmol/Cmol under aerobic conditions and 0.4-0.5 Cmol/Cmol under anoxic conditions, irrespective of the specific growth rate of the biomass and the specific acetate uptake rate in the feast period . Degradation of internal stored PHB could be described with a first order degradation rate with respect to the PHB content of the cells . Degradation of PHB appeared to be independent of the type of electron acceptor present in the system and independent of the SRT of the system . The kinetic descriptions can be used to predict PHB production and consumption in general in dynamic fed wastewater treatment systems, and they provide some trends for modeling purposes.

Water Res, 2002 Mar, 36(5), 1135 - 42
P-nitrophenol degradation by activated sludge attached on nonwovens; Bhatti ZI et al.; p-Nitrophenol (PNP) is a toxic compound that enters the environment during manufacturing and processing of a variety of industrial products . This study demonstrates the use of inexpensive and durable nonwovens as a biomass retainer for the biological degradation of p-nitrophenol . An essential aspect of p-nitrophenol degradation was the cultivation of p-nitrophenol degrading biomass prior to its attachment on the nonwovens . Results of continuous flow experiments demonstrated that using the nonwovens could attain consistent high-rate p-nitrophenol degradation . 500 mg-PNP/L was completely degraded at a hydraulic retention time of 11 h . Specific and volumetric p-nitrophenol loading rates were determined to be 165 mg-PNP/g-MLSS/d and 1.6 g-PNP/L/d, respectively . Nitrite released from p-nitrophenol breakdown was not completely nitrified to nitrate . Characteristics of p-nitrophenol degrading sludge were also investigated.

Water Sci Technol, 2002, 45(3), 219 - 28
Pollution based real time control of wastewater systems; Risholt LP et al.; Wastewater systems are traditionally built as static systems to handle a design load . The real load varies, though, and hardly ever equals the design load . This implies that wastewater systems hardly ever operate in an optimum way, especially during wet weather . Real time control (RTC) of regulators can improve the operation by better fit of the system to the actual state and load . RTC based on pollutant concentrations together with hydraulic conditions (pollution based real time control, PBRTC) is investigated in this paper to assess the potential pollutant load reduction on receiving waters at wet weather without expansion of transport or storage capacity . Both CSOs and WWTP effluents contribute to the pollutant discharges to receiving waters and both are considered . Three cases are studied to assess the potential benefit of PBRTC . Giving priority to the most polluted wastewater for treatment and storage in branched interceptor systems can reduce CSO discharge loads by more than 20% . Biological WWTPs and especially activated sludge plants are more complex and less stable than chemical precipitation plants during and after high pollutant and hydraulic load . Biological plants can hence profit more from PBRTC than chemical precipitation plants . Receiving waters that are sensitive to acute effects caused by intermittent discharges can benefit more from PBRTC than receiving waters with problems connected to long-term accumulation of pollution.

Water Sci Technol, 2002, 45(3), 101 - 8
Online-simulation of the WWTP to minimise the total emission of WWTP and sewer system; Seggelke K et al.; In this paper, the application of a WWTP-Online-Simulation with the objective to reduce the total emission into the receiving waters is explained . Apart from an introduction and a short description of the possible reduction potentials, first results of the current research project (financed by the German ministry BMBF) are presented . Results of the pilot plant with different experiments of increased stormwater inflow than usual and different control strategies showed the possibility to treat stormwater up to the quadruple dry-weather flow while still meeting the effluent values . However, this is not always guaranteed, and thus a monitoring system with integrated control strategies which is adapted to the load case "stormwater" with prognosis load cases becomes necessary . In the presented example, the simulation (Activated Sludge Model 2d) achieved an excellent match with the measured effluent values of the aeration tank (NH4-N, NO3-N) over a period of several months . The most important prerequisites for good (online-) simulation results are the exact knowledge of the plant and the plausibility and alternative concepts for the measured values in case of sensor failure.

Environ Sci Technol, 2002 Feb 1, 36(3), 387 - 93
Collision frequencies of microbial aggregates with small particles by differential sedimentation; Li XY et al.; Collision and coagulation rates between microbial aggregates and small particles were measured for individual aggregates (1.0-2.5 mm) that settled through a suspension of fluorescent yellow-green (YG) particles (2.83 microm) placed in a settling column . The microbial aggregates, with an average fractal dimension of 2.26, were generated in a lab-scale sequencing batch reactor (SBR) and also collected from a full-scale activated sludge (AS) treatment system . As calculated from comparisons between the settling velocities observed and those predicted by Stokes' law for impermeable particles, the average fluid collection efficiencies were 0.08 for the SBR aggregates and 0.14 for the AS flocs, which were much lower than those previously reported for nonbiological aggregates of latex microspheres . The collision frequency functions between microbial aggregates and small YG particles were 2 orders of magnitude lower than predicted by the rectilinear model but 1 order of magnitude greater than predicted by a curvilinear model . The overall scavenging efficiencies of suspended particles by the falling microbial aggregates compared well with those observed for the nonbiological aggregates, while the particle removal efficiencies from the flow internal to the microbial aggregates were 1 order of magnitude higher than those of the nonbiological aggregates . It is argued that the permeability of microbial aggregates could be reduced by exopolymeric material clogging the pores within the aggregates . The internal permeation through a bioaggregate thus may not be significant enough to be included in the calculation of its settling velocity; however, the intra-aggregate flow cannot be simply neglected where coagulation is concerned . Streamlines still can penetrate the interior of microbial aggregates, allowing greater collision frequencies with other particles than predicted by the curvilinear model . The narrow and convoluted internal flow passages resulting from the collection of extracellular polymeric substances may also contribute to the higher interior particle removal efficiencies of microbial aggregates than those of more permeable, nonbiological aggregates.

Biotechnol Bioeng, 2002 Apr 20, 78(2), 119 - 30
Successional development of sulfate-reducing bacterial populations and their activities in an activated sludge immobilized agar gel film; Okabe S et al.; A combination of fluorescence in situ hybridization (FISH), microprofiles, and denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rDNA fragments followed by hybridization analysis with specific probes was applied to investigate successional development of sulfate-reducing bacteria (SRB) community structure and in situ sulfide production activity within an activated sludge immobilized agar gel film . In this model biofilm system, since biases arising from biofilm heterogeneity can be ignored, the population dynamics of SRB in the agar gel is directly related to physiological capability and in situ activity of SRB . Microelectrode measurements showed that an anoxic zone was already developed at the beginning (0 day), a first sulfide production of 0.054 mumol H2S m(-2) x s(-1) was detected during the first week, and the rate increased gradually to 0.221 mumol H2S m(-2) x s(-1) in the fifth week . The most active sulfide production zone moved upward to the chemocline and intensified with time to form a narrow zone with high volumetric sulfide production rates . This result coincided with the shift of the spatial distributions of SRB populations determined by FISH . In situ hybridization with probe SRB385 for mainly general SRB of the delta Proteobacteria plus some gram-positive bacteria and probe 660 for Desulfobulbus indicated that the most abundant populations of SRB were primarily restricted to near the oxic/anoxic interface (chemocline) . A close observation of the development of the vertical distributions of SRB populations revealed that the cell numbers of Desulfobulbus tripled (from 0.5 x 10(8) to 1.5 x 10(8) cells cm(-3)) near the oxic/anoxic interface . Similar growth (from 1.0 x10(8) to 4.5 x 10(8) cells cm(-3)) of Desulfovibrio-like SRB that hybridized with probe SRB385 was observed . PCR-DGGE followed by hybridization analysis revealed that one Desulfobulbus strain was detected from the beginning, and another strain appeared after 1 week, coinciding with the first detected sulfide production . In addition, three strains hybridizing with probe 687 (possibly Desulfovibrio) were also dominant SRB in the agar gel .

Int J Syst Evol Microbiol, 2002 Jan, 52(Pt 1), 223 - 8
Quadricoccus australiensis gen . nov., sp . nov., a beta-proteobacterium from activated sludge biomass; Maszenan AM et al.; A gram-negative coccus, designated strain Ben 117T, was obtained in axenic culture by micromanipulation from an Australian activated sludge biomass sample, which had been subjected to chlorination in order to alleviate problems associated with foaming and bulking . This isolate was a strict aerobe and grew in axenic culture, also appearing in biomass samples as cocci or clusters of cocci in tetrads, thus resembling the morphotype 'G-bacteria' seen commonly in activated sludge samples . Strain Ben 117T was non-motile, aerobic, oxidase-negative and catalase-positive and grew between 15 and 30 degrees C, with an optimum of 25-30 degrees C . The pH range for growth was between 6.0 and 8.5, with an optimum of 7.5-8.5 . The isolate stained positively for intracellular polyphosphate and poly-beta-hydroxybutyrate and its G+C content was 67 mol% . 16S rDNA sequence analysis suggests that strain Ben 117T is phylogenetically different from members of the genera Amaricoccus, gram-negative 'G-bacteria' isolated previously in this laboratory . Ben 117T is a member of the Rhodocyclus group in the beta-Proteobacteria and equidistantly placed (similarity value of 95%) between Ferribacterium limneticum and Dechloromonas agitata (mean similarity value of 92% with the genus Rhodocyclus) . Based on phenotypic and phylogenetic evidence, it is proposed that strain Ben 117T be designated a novel species in a new genus, Quadricoccus australiensis gen . nov., sp . nov.; the type strain is Ben 117T (= NCIMB 13738T = CIP 107055T).

Huan Jing Ke Xue, 2001 Nov, 22(6), 72 - 5
{Biosorption of heavy metals by bacteria isolated from activated sludge}; Wang Y et al.; In this paper, biosorption efficiency of heavy metals by bacteria isolated from activated sludge was tested . It was shown that Pseudomonas pseudoalcaligenes and Micrococcus luteus GC subgroup B had high biosorption capacities for Cu(II) and Pb(II) ions . The adsorption of the two ions on Pseudomonas pseudoalcaligenes and Micrococcus luteus GC subgroup B exhibited Langmuir adsorption behavior with regression coefficient of 0.99 . The pH value was the most important effect factor on biosorption of metal ions . The biosorption kinetic curves of Cu(II) and Pb(II) ions by cells showed two processes: rapid sorption on cell surface and slowly longer-term transformation into cells . Cu(II) ion can be desorbed effectively from cells of Micrococcus luteus GC subgroup B.

Huan Jing Ke Xue, 2001 Nov, 22(6), 61 - 5
{Non-filamentous activated sludge bulking caused by the deficiency of nitrogen}; Gao C et al.; The effect of nitrogen deficiency on activated sludge bulking was studied specially in some experiments carried on a sequencing batch reactor fed with beer wastewater in this paper . The experimental results showed that the sludge settled properly at a influent BOD/N value of 100/4 . When the value of BOD/N was 100/3 and 100/2 respectively, non-filamentous activated sludge bulking caused by an excessive growth of viscous Zoogloea with high moisture content occurred . When the value of influent BOD/N was 100/0.94, more serious non-filamentous bulking occurred . Furthermore, the effect of nitrogen deficiency on the nitrogen sources and phosphorus sources utilization rate and the COD removal rate was studied in the experiments.

Water Res, 2002 Feb, 36(4), 919 - 24
Evaluation of wastewater toxicity: comparative study between Microtox and activated sludge oxygen uptake inhibition; Gutierrez M et al.; Microtox is a frequent toxicity tool for the screening of wastewaters discharged into wastewater treatment plants . There is currently an increasing controversy between this test and others using activated sludge . A Microtox and electrolytic respirometry comparative study for toxicity determination has been performed . Seven organic and five inorganic toxic compounds have been assessed for comparing both methods . Microtox proved to have a higher sensitivity to toxicants but was less representative of effects on activated sludge compared to respirometry . For instance, assays accomplished with LAS, a biodegradable reference surfactant, showed a toxic effect by Microtox but good biodegradability and no toxicity in respirometry . This could be explained by the different nature of the biological material used, as Microtox utilises the seawater Vibrio fischeri, whereas respirometry uses the bacterial consortium in activated sludge . For the evaluation of the potential toxicity of a compound on a WWTP, the preferred biological material be used should be activated sludge itself . Results obtained with any other biological material would be just an approach to reality.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2002, 37(2), 163 - 73
Use of coagulant and zeolite to enhance the biological treatment efficiency of high ammonia leachate; Ahn DH et al.; Most landfill leachates in Korea, herein defined as the contaminated liquid resulting from the percolation of water through a landfill, are high in ammonium nitrogen, which inhibits biological treatment processes and deteriorates rivers . A laboratory experiment investigated the effect of pre-removal of ammonium nitrogen using zeolite on the efficiency of organic treatment of the following activated-sludge process . Ferric chloride was initially used as a coagulant for solids removal . A clinoptilolite and mordenite rich rock from the Guryongpo area, the Yeongil Basalt, in Korea, reduced the ammonia nitrogen concentrations of leachate from 1300-1500 to 110-130 mg/l in a 24h batch operation . Three activated sludge reactors were operated to compare treatment efficiency under different influent conditions . In reactor 1, leachate having high concentration of chemical oxygen demands (COD) and suspended solids (SS) was directly fed to the reactor without pretreatment . The supernatant, after the coagulation process that remove some suspended solids and COD, was fed to reactor 2 . As the use of coagulation process alone is not effective to remove ammonium nitrogen, supernatant treated by both coagulation focusing on the removal of COD and the zeolite concentrating on the removal of ammonium nitrogen was fed to reactor 3 . As the result of experiment, greater efficiency in lowering the chemical oxygen demand (83%, influent COD; 1800-3000 mg/l, effluent COD; 300-500 mg/l) was achieved in reactor 3 . Meanwhile, 63% (influent COD; 4000-5000 mg/l, effluent COD; 1470-1840 mg/l) and 66% (influent COD; 2400-3300 mg/l, effluent COD; 820-1100 mg/l) removal efficiency of COD were achieved in reactors 1 and 2, respectively . Thus, ammonia pre-removal by zeolite remarkably improved the lowering of chemical oxygen demand and the solids separation in the activated sludge process.

Water Sci Technol, 2002, 45(1), 117 - 25
Low cost reclamation using the Advanced Integrated Wastewater Pond Systems Technology and reverse osmosis; Downing JB et al.; The sustainability of wastewater reclamation and reuse schemes is often limited by the increase in salt concentration that occurs with each water use . In this pilot study, we show that the cost of reclaiming wastewater and removing salt can be dramatically decreased by integrating recent advances in wastewater pond design, solids separation equipment, and membrane technology . Effluent from an AIWPS Facility was clarified in a Krofta Supracell Dissolved Air Flotation (DAF) unit and a Slow Sand Filter (SSF) prior to final treatment in an Expertise S.r.l . reverse osmosis (RO) unit . The ponds of the AIWPS Facility removed an average of 82% of soluble BOD and 80% of soluble nitrogen . Following clarification, filtration, and RO treatment, the pollutant removals were > 99% for soluble BOD, > 99% for soluble nitrogen, and 98% for TDS . Based on membrane fouling rate data, the cleaning interval for the RO membranes in a full-scale AIWPS-RO Facility would be over 100 days . This interval is on par with that typically seen in full-scale reclamation facilities treating secondary activated sludge effluent with microfiltration prior to reverse osmosis . A 4-MLD AIWPS-RO Facility is expected to produce permeate water at substantially lower cost and lower energy consumption (US $698 and 443 kWh per million liters treated) than a system of equal capacity using conventional activated sludge secondary treatment followed by microfiltration and reverse osmosis (US $1274 and 911 kWh per million litres treated) . This cost and energy differential is attributable to the lower capital and operating expenses of the AIWPS Technology in comparison with activated sludge.

Appl Microbiol Biotechnol, 2002 Jan, 58(1), 106 - 11
Selective enrichment and characterization of a phosphorus-removing bacterial consortium from activated sludge; Hollender J et al.; Under alternating aerobic/anaerobic conditions and without additional carbon sources, a bacterial consortium consisting initially of 18 bacterial strains was obtained in a sequence batch reactor . The phosphorus removal capability could only be maintained using sterile filtrate of activated sludge as medium . The addition of calcium and magnesium salts, as well as vitamins and trace elements, to autoclaved sterile filtrate of activated sludge was not sufficient to achieve stable phosphorus removal . A further enrichment by subcultivation on solid, agar, freezing, and shortening of the aerobic and anaerobic phases led to a defined bacterial consortium consisting of four strains . On the basis of physiological and chemotaxonomic characterization, and partial 16S rRNA sequencing, one of the organisms was identified as Delftia acidovorans . A further isolate belonged to the Bacillus cereus group, and the third isolate was identified as Microbacterium sp. . The remaining strain seems to represent a new genus within the Flavobacteriaceae . Under continuous chemostat conditions, this consortium was able to remove up to 9.6 mg P/l phosphate in the aerobic phase and released up to 8.5 mg/l in the anaerobic phase . Up to 25 mg P-polyphosphate/g dry mass was stored under aerobic conditions.

Water Res, 2002 Jan, 36(2), 460 - 8
Assessment of activated sludge viability with flow cytometry; Ziglio G et al.; The aim of the study was to evaluate the applicability of fluorescent dyes and multiparameter flow cytometry for the rapid and direct viability/activity assessment of activated sludge samples taken from wastewater treatment plants . Viability and activity of the biomass were estimated respectively through cellular membrane integrity, staining with SYBR Green I and Propidium Iodide, and through fluorogenic dyes capable of detecting enzymatic activity, as FDA and BCECF-AM . A procedure has been developed to disaggregate sludge flocs before dyes staining and cytometric analysis . The developed procedure allows a high recovery of bacteria with good accuracy and repeatability, and minimize the damage of the cells suspension obtained from the disaggregation of the flocs . These measurements were applied to estimate the two main parameters required to define the biological activated sludge process: the endogenous decay rate and the specific growth rate in exponential phase with high F/M ratio . Oxygen utilization rate measurements (OUR) were conducted to conventionally monitor the activity of the biomass . The preliminary data are encouraging and support the possibility to investigate bacteria dynamics on wastewater treatment plants.

Water Res, 2002 Jan, 36(2), 445 - 59
Role of filamentous microorganisms in activated sludge foaming: relationship of mycolata levels to foaming initiation and stability; de L 3rd et al.; The relationship between the levels of mycolic acid-containing actinomycetes (mycolata), Gordonia spp . and Gordonia amarae, and foam initiation and stability was characterized using: (1) batch tests involving addition of G . amarace cells to activated sludge, (2) analysis of a full-scale activated sludge plant that experienced seasonal foaming, and (3) a study of lab-scale activated sludge reactors augmented with G . amarae . Using batch tests, threshold Gordonia levels for foam formation and foam stability were determined to be approximately 2 x 10(8) microm ml(-1) and 1 x 10(9) microm ml(-1), respectively . In the full-scale plant, the levels of Gordonia spp . and G . amarae increased during the course of foaming, and the foam formation threshold of 2 x 10 microm ml(-1) corresponded to the onset of foaming . This value was also verified in lab-scale reactor washout experiments, where decreasing mycolata levels were observed during the course of foam dissipation . The foam stability threshold of 1 x 10(9) micorm ml(-1) was verified in lab-scale reactor studies . The increase in the levels of Gordonia spp . and G . amarae in the full-scale plant corresponded to an increase in temperature, suggesting that the growth of Gordonia spp . was favored during warmer periods.

Water Res, 2002 Jan, 36(2), 439 - 44
Active biomass in activated sludge mixed liquor; Cronje GL et al.; The engineering and technology of the activated sludge system are reasonably well established, with systems implemented worldwide for the biological removal of C, N and/or P . Parallel to this development, significant advances have been made in the microbiological and biochemical areas of activated sludge . These advances have been driven by the development of new analytical techniques that allow microorganisms to be studied in situ in the activated sludge environment . However, there has been little cross-linking and overlap between the engineering and technology and microbiology and biochemistry paradigms . In particular, the information from the microbiology and biochemistry has not been integrated into the engineering and technology paradigm, to enable improved system design and optimization . One area that can form a starting point to build bridges between the two paradigm sets, is measurement of active biomass . The current design and simulation models invariably include active biomass for each organism group as fundamental parameters which define quantitatively the kinetic rates of the relevant biological processes . However, these parameters remain purely hypothetical because to date they have not been quantitatively measured; their acceptance is based on the consistency of model predicted results over a wide range of application . This paper describes developments in quantitative measurement of the heterotrophic and autotrophic active biomass concentrations within the engineering and technology paradigm, and the formulation of a multinational project which will attempt to link these measurements and the defined engineering environment to the new microbiological and biochemical analytical techniques . It is hoped that this project will facilitate integration of the two paradigms sets.

Water Res, 2002 Jan, 36(2), 394 - 402
Microbiological aspects of a bioreactor with submerged membranes for aerobic treatment of municipal wastewater; Witzig R et al.; An aerobic membrane bioreactor treating municipal wastewater at complete biomass retention was studied in respect of microbiological parameters over a period of 380 days . The results were compared to those obtained from a conventional activated sludge wastewater treatment plant (WWTP) treating the same wastewater . Microscopically, significant changes in the structure of the flocs and of the ratio between free suspended and aggregated cells could be observed . The presence of filamentous bacteria varied from almost not present to very high numbers . With the exception of short periods after changes in operating conditions, protozoa and metazoa were rarely present in the sludge community . The rate of oxygen consumption and the cell detectability by fluorescence in situ hybridizatio (FISH) with rRNA-targeted oligonucleotide probes were used to assess the physiological state of the bacterial cells Oxygen consumption rates of sludge samples obtained from both the conventional and membrane filtration plant wer determined without and after addition of different energy and carbon sources . In contrast to the conventional activate sludge, a pronounced increase in respiration activity upon the addition of organic substrates could be observed in th membrane filtration sludge . In situ probing with the Bacteria-specific probe EUB338 visualized 40-50% of all DAPI stainable bacteria in the membrane bioreactor, compared to 80% cells detectable by FISH in the conventional activate sludge . These results suggest that bacteria present in the highly concentrated biomass of the membrane reactor use the energy supplied for their maintenance metabolism and were not in a physiological state characteristic for growth This assumption could explain the zero net biomass production observed in the reactor.

Water Res, 2002 Feb, 36(3), 676 - 84
Evolution of size distribution and transfer of mineral particles between flocs in activated sludges: an insight into floc exchange dynamics; Chaignon V et al.; The aggregation behavior of activated sludge flocs was investigated by monitoring the size distribution of flocs and transfer of mineral particles between flocs, under various conditions of agitation and dilution . The results showed that (i) the shape of the floc size distribution can be fitted with a gamma function, (ii) a steady-state mean floc size is reached for a given stirring rate, (iii) this stable floc size is shifted towards floc growth as sludge concentration is increased, (iv) under cycled-shear conditions, microbial aggregates break up and re-form in an almost reversible manner, (v) blending of raw sludge and sludge spiked with Aquatal mineral particles results in particle exchange between flocs and (vi) the detailed study of exchange kinetics indicates that some flocs do not participate to the aggregation dynamics . These experimental results suggest that the activated sludge floc size is governed by a flocculation/deflocculation balance, implying an exchange of floc constituents between microbial aggregates.

Water Res, 2002 Feb, 36(3), 656 - 66
Feasibility of using a chlorination step to reduce excess sludge in activated sludge process; Saby S et al.; The ultimate disposal of excess sludge generated from activated sludge processes has been one of the most challenging problems for wastewater treatment utilities . Previous work has shown that excess sludge can be minimized successfully by using sludge ozonation to dissolve it into substrates to be oxidized in the aeration tank . However, this approach is a costly option . Therefore, as an alternative solution, we propose to use chlorination to replace ozonation in excess sludge minimization in the light of operational cost . To investigate the feasibility of this low cost approach, this paper mainly focuses on the effect of chlorination on sludge reduction rate, formation of trihalomethanes, sludge settleability, and effluent quality . Two identical activated sludge membrane bioreactors were continuously operated with synthetic wastewater under the same operation conditions for several months . During this period, one pilot unit was used as the reference system without chlorination of excess sludge, while another served as a testing unit, where excess sludge was taken out for conducting chlorination at a dose of 133mg/g MLSS every day and the chlorinated liquor was then returned to the aeration tank . The sludge production rate and the water quality of both the units were analyzed daily . It was observed that the sludge production could readily be reduced by 65% once the chlorination treatment was involved . However, the chlorination treatment also resulted in poor sludge settleability as well as significant increase of soluble chemical oxygen demand in the effluent, which creates potential difficulties in the operation of a conventional treatment plant with gravity clarifiers . However, it has been demonstrated that by integrating the immersed membrane into the activated sludge process these difficulties can be overcome effectively.

Water Res, 2002 Feb, 36(3), 539 - 50
Network strength and dewaterability of flocculated activated sludge; Yen PS et al.; Works in literature proposed the use of the rheological properties of wastewater sludges as an index for conditioner assessment and control . We demonstrated in this work, on the contrary, that one could not justify the consistency of the commonly used rheological characteristics of the sewage sludge samples taken from the same site but at different dates . A physically relevant index was proposed instead for describing the total network strength, which was hypothesized to correlate the dewatering efficiency of flocculated sludge . Based on this index, the network of a sludge was demonstrated to be largely destroyed after shearing, while the relaxation in an unbound environment or mild pouring over action could partially reinstall the structure . Moreover, a uniform shear rate field could produce network of greater strength when compared with that conditioned in a stirred tank.

Water Res, 2002 Feb, 36(3), 527 - 38
Examination of three theories for mechanisms of cation-induced bioflocculation; Sobeck DC et al.; Research from different studies has been used to support three different theories pertaining to the role of cations in bioflocculation . These theories are the alginate theory . Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory, and divalent cation bridging (DCB) theory . The objectives of this research were to examine the role of cations in bioflocculation to determine which theory, if any, best describes cation induced bioflocculation . Experiments were performed using laboratory scale activated sludge systems with bactopeptone as a feed . The feed was supplemented with either calcium, magnesium, or sodium at increasing concentrations . Floc properties were analyzed in each reactor during steady state periods . The addition of calcium or magnesium to the feed individually resulted in improvements in SVI, CST, SRF, cake solids and floc strength and each of these divalent cations produced similar results . The addition of sodium to the feed resulted in a deterioration in floc properties relative to a control reactor . Analysis of these results suggest that the DCB theory best explains the role of cations . The discrepancies between different studies were examined and are thought to be a result of different experimental procedures in different studies and in particular the use of short-term batch tests versus continuous flow reactor studies . In addition, the implications of DCB theory suggests that activated sludge systems should attempt to lower the ratio of monovalent to divalent cations to improve floc properties and treatment performance.

Appl Environ Microbiol, 2002 Feb, 68(2), 942 - 6
Genetic and immunochemical characterization of thiocyanate-degrading bacteria in lake water; Yamasaki M et al.; Natural aquatic and soil samples were screened for the presence of thiocyanate-degrading bacteria . Using thiocyanate supplementation, we established an enrichment culture containing such bacteria from lake water . The dominant bacteria had the scnC-LS5 gene encoding thiocyanate hydrolase, which was closely related to the enzyme found previously in Thiobacillus thioparus THI115 isolated from activated sludge.

Syst Appl Microbiol, 2001 Nov, 24(3), 430 - 42
Pyrolysis mass spectrometry (PyMS) and 16S-23S rDNA spacer region fingerprinting suggests the presence of novel acinetobacters in activated sludge; Carr E et al.; Screening of large numbers of Acinetobacter spp . from activated sludge systems with Pyrolysis Mass Spectrometry (PyMS) showed that many did not cluster tightly with the currently described genomic species which have been obtained mainly from clinical sources . Selected isolates were then genotypically fingerprinted using their 16S-23S rDNA spacer region, and again the data revealed considerable differences in the genomic fingerprints of many of these activated sludge isolates to the predominantly clinical genomic species . In fact, few could be identified from them . The possibility that the current speciation within this genus is not adequate to encompass all these environmental isolates is addressed in relation to the methods used to study the population dynamics of Acinetobacter in activated sludge.

Chemosphere, 2002 Jan, 46(1), 137 - 42
Heavy metal removal by activated sludge: influence of Nocardia amarae; Kim DW et al.; The goal of this research was to examine the metal binding capacity of Nocardia amarae cells and to assess the influence of Nocardia cells on the overall metal binding capacity of activated sludge . Metal sorption capacities of the pure Nocardia cells and activated sludge biomass containing various levels of added Nocardia pure cultures were determined by a series of batch experiments . Batch sorption isotherms for nickel (Ni), copper (Cu), and cadmium (Cd) showed that the pure culture of N . amarae exhibited significantly higher metal sorption capacity than the activated sludge biomass obtained from Wilmington Wastewater Treatment Plant (Wilmington, DE) . Surface area of biomass estimated by a dye technique showed that pure N . amarae cells growing at stationary phase have substantially more specific surface area than that of activated sludge from Wilmington Treatment Plant . A two-fold difference in specific surface area indicated that the higher metal sorption capacity of Nocardia cells may be due to the higher specific surface area . The metal sorption capacity of activated sludge increased proportionally with the amount of Nocardia cells present in the mixed liquor . This increase was attributed to the greater specific surface area of the mixed liquor samples containing greater amounts of Nocardia cells.

Environ Technol, 2001 Nov, 22(11), 1253 - 62
Refixation of phosphates released during bio-P sludge handling as struvite or aluminium phosphate; Jardin N et al.; Phosphate release and phosphate fixation during sludge treatment of waste activated sludge was investigated with a pilot plant for enhanced biological phosphorus removal, complemented by laboratory investigations of sludge samples from different large enhanced biological phosphorus removal plants . The major part of the eliminated phosphorus in the pilot plant was due to the storage of polyphosphate in the waste activated sludge and was accompanied by an uptake of magnesium and potassium . Stabilising waste activated sludge from the enhanced biological phosphorus removal pilot plant results in a hydrolysis of polyphosphate . As a result of polyphosphate hydrolysis in stabilising systems, phosphate, magnesium and potassium are released, but only potassium remains in solution whereas magnesium and a part of the released phosphate was precipitated as struvite . Another large fraction of the released phosphate was fixed by participation of aluminium.

Water Sci Technol, 2001, 44(11-12), 393 - 8
Reed beds: constructed wetlands for municipal wastewater treatment plant sludge dewatering; Begg JS et al.; Reed beds are an alternative technology wastewater treatment system that mimic the biogeochemical processes inherent in natural wetlands . The purpose of this project was to determine the effectiveness of a reed bed sludge treatment system (RBSTS) in southern New England after a six-year period of operation by examining the concentrations of selected metals in the reed bed sludge biomass and by determining the fate of solids and selected nutrients . Parameters assessed in both the reed bed influent and effluent: total suspended solids, biochemical oxygen demand, nitrate-nitrogen and total phosphorus . In addition, the following metals were studied in the reed bed influent, effluent and Phragmites plant tissue and the sludge core biomass: boron, cadmium, chromium, copper, iron, lead, manganese, molybdenum, nickel, and zinc . The removal efficiencies for sludge dewatering, total suspended solids and biochemical oxygen demand were all over 90% . Nitrate and total phosphorus removal rates were 90% and 80% respectively . Overall metals removal efficient was 87% . Copper was the only metal in the sludge biomass that exceeded the standards set by the Massachusetts Department of Environmental Protection for land disposal of sludge . The highest metal concentrations, for the most part, tended to be in the lower tier of the sludge profile . The exception was boron, which was more concentrated in the middle tier of the sludge profile . The data and results presented in this paper support the notion that reed bed sludge treatment systems and the use of reed beds provide an efficient and cost effective alternative for municipal sludge treatment.

Water Sci Technol, 2001, 44(11-12), 339 - 43
Constructed wetlands for wastewater treatment in central Italy; Conte G et al.; The performance of 4 constructed wetlands designed by IRIDRA Srl and operating in Tuscany (central Italy) has been monitored during the last three years . The 4 treatment systems have different sizes and characteristics: one single stage secondary treatment (150 p.e.); two secondary treatment plants with effluent reuse: one small (60 p.e) and the other big (350 p.e.); a tertiary treatment of effluents from an activated sludge plant with high hydraulic load fluctuation (5-500 p.e.) . Due to geographical and economic constraints the four systems have high hydraulic and organic loading rates, neverthless the systems show very good removal performance of COD (62-95%), especially the ones with higher inflow COD concentrations (87-95%) . Interesting results concerning also removal percentage of MBAS (42-88%) and ammonium (42-85%) were obtained, even though NH4+ concentration in the outflows of some of the plants, doesn't always comply with Italian quality standards.

Water Sci Technol, 2001, 44(10), 71 - 8
Fractionation and characterization of sludge bacterial extracellular polymers by FT-IR, 13C-NMR, 1H-NMR; Zhou LX et al.; Sludge bacterial extracellular (BEP) polymers exhibit a strong affinity with metals in addition to their role in the bioflocculation of activated sludge . It is of utmost importance in elucidating the chemical characterization of sludge BEP prior to a better understanding of its environmental behavior . Sludge BEP extracted from activated sludge was characterized by FT-IR, 1H-NMR, and 13C-NMR and fractionated into 6 fractions (hydrophilic acid, base, and neutral; and hydrophobic acid, base, and neutral) . The results indicated that sludge BEP contained more polysaccharides but fewer amino acids or proteinaceous materials compared to dissolved organic matter (DOM) derived from sludge . No aromatic substance was found in sludge BEP as indicated by NMR . Sludge BEP was dominated by hydrophilic fractions, accounting for 65% of total DOC of sludge BEP and hydrophilic neutral constituted about 58% of the hydrophilic fraction . The chemical fraction and characterization indicated that sludge BEP might exhibit a higher capability in enhancing the transport of the associated contaminants through porous media than that of sludge DOM.

Water Sci Technol, 2001, 44(10), 53 - 8
Heavy metal removal from wastewater and leachate co-treatment sludge by sulfur oxidizing bacteria; Aralp LC et al.; Heavy metal concentration in sludge is one of the major obstacles for the application of sludge on land . There are various methods for the removal of heavy metals in sludge . Using sulfur oxidizing bacteria for microbiological removal of heavy metals from sludges is an outstanding option because of high metal solubilization rates and the low cost . In this study, bioleaching by indigenous sulfur oxidizing bacteria was applied to sludges generated from the co-treatment of municipal wastewater and leachate for the removal of selected heavy metals . Sulfur oxidizing bacteria were acclimated to activated sludge . The effect of the high organic content of leachate on the bioleaching process was investigated in four sets of sludges having different concentrations of leachate . Sludges in Sets A, B, C and D were obtained from co-treatment of wastewater and 3%, 5%, 7% and 10% (v/v) leachate respectively . The highest Cr, Ni and Fe solubilization was obtained from Set A . Sulfur oxidizing bacteria were totally inhibited in Set D that received the highest volume of leachate.

Water Sci Technol, 2001, 44(10), 327 - 32
Influence of pH on the dewatering of activated sludge by Fenton's reagent; Lu MC et al.; The specific filtration resistance, moisture, and SVI were used to evaluate the influence of pH on the filtration and dewatering efficiencies when applying Fenton's reagent to treat the excess sludge . The excess sludge used in this study was obtained from the wastewater treatment plant of An-Ping Industrial Park in Tainan, Taiwan . Results show that initial pH has no significant effect on the filtration efficiency of sludge by using the Fenton (Fe2+/H2O2) system as the treatment process . However, the reduction of specific resistance by Fenton-like (Fe3+/H2O2) process decreased suddenly to a level similar to that obtained from the control experiment at initial pH > 4.5 . For the moisture of cake sludge, both Fenton and Fenton-like systems have the same tendency; the moisture of cake sludge increased slightly with increasing the initial pH . The SVI values for Fenton process decreased with increasing the initial pH, but the opposite result was obtained from the Fenton-like and control system; higher pH was not favorable for the sludge settling.

Water Sci Technol, 2001, 44(10), 237 - 43
Bioflocculation production from lower-molecular fatty acids as a novel strategy for utilization of sludge digestion liquor; Fujita M et al.; We propose the bioproduction of a bioflocculant from lower-molecular fatty acids as an innovative strategy for utilizing waste sludge digestion liquor . Fundamental studies on the production, characterization and application of a novel bioflocculant were performed . Citrobactersp . TKF04 was screened out of 1,564 natural isolates as a bacterial strain capable of a bioflocculant from acetic and propionic acids . TKF04 produced the bioflocculant during the logarithmic growth in the batch cultivation, and it could be recovered from the culture supernatant by ethanol precipitation . The fed-batch cultivation with feeding of acetic acid: ammonium 10;1 (mole) to maintain pH 8.5 led to the hyper-production of the bioflocculant . The bioflocculant was found to be effective for flocculating a kaolin suspension, when added at a final concentration of 1-10 mg/l, over a wide range of pHs (2-8) and temperatures (3-95 degrees C), while the addition of cations was not required . It could flocculate a variety of inorganic and organic suspended particles including kaolin, diatomite, bentonite, activated carbon, soil and activated sludge . These indicated that the bioflocculant possesses flocculating activity comparable or superior to that of synthetic flocculants . The bioflocculation was identified as a chitosan-like biopolymer.

Water Sci Technol, 2001, 44(10), 221 - 9
Effect of carbon to nitrogen ratio on the composition of microbial extracellular polymers in activated sludge; Durmaz B et al.; Effect of carbon to nitrogen ratio (C/N) on the sludge extracellular polymer composition is studied in synthetically fed semi-continuous reactors with 8 days of sludge age . Results show that C/N ratio influences the relative distribution of polymer carbohydrate and protein . At low C/N ratio of 5, polymer extracts have high protein and low carbohydrate content . As the C/N ratio is increased to 17.5 and then to 40, carbohydrate concentration increases sharply and protein concentration decreases.

Water Sci Technol, 2001, 44(10), 203 - 8
New approaches to minimize excess sludge in activated sludge systems; Chen GH et al.; This paper presents three new approaches to reduce excess sludge production in activated sludge systems: 1) modification of conventional activated sludge process with insertion of a sludge holding tank in the sludge return line; 2) chlorination of excess sludge so as to minimize excess sludge production; and 3) utilization of a metabolic uncoupler, 3, 3', 4', 5-Tetrachlorosalicylanilide (TCS) to maximize futile activity of sludge microorganisms thereby leading to a reduction of sludge growth . Pilot study was carried out to evaluate this modified activated sludge process (OSA) . It has been confirmed that the OSA process is effective in reducing excess sludge; particularly when the ORP level in the sludge holding tank was kept at -250 mV, more than 50% of the excess sludge was reduced . This process can maintain the effluent quality and even perform with a better sludge settleability than a conventional system . Experimental work on the second approach showed that chlorination treatment of excess sludge at a chlorine dose of 0.066 g Cl2/g MLSS reduced the excess sludge by 60%, while concentration of THMS was found below 200 ppb in the treated sludge . However, such sludge chlorination treatment sacrificed sludge settleability . Thus, it is not feasible to introduce the chlorination step to a conventional system . The third approach confirmed that addition of TCS could reduce sludge growth effectively if the TCS concentration is greater than 0.4 ppm . A 0.8-ppm concentration of TCS actually reduced excess sludge by 45% . It was also experimentally demonstrated that presence of TCS increases the portion of active sludge microorganisms over the entire microbial population.

Water Sci Technol, 2001, 44(10), 137 - 42
Extracellular polymers of ozonized waste activated sludge; Liu JC et al.; Effect of ozonation on characteristics of waste activated sludge was investigated in the current study . Concentrations of cell-bound extracellular polymers (washed ECPs) did not change much upon ozonation, whereas the sum of cell-bound and soluble extracellular polymers (unwashed ECPs) increased with increasing ozone dose . Washed ECPs in original sludge as divided by molecular weight distribution was 39% < 1,000 Da (low MW), 30% from 1,000 to 10,000 Da (medium MW), and 31% > 10,000 Da (high MW) . It was observed that the low-MW fraction decreased, and the high-MW fraction increased in ozonized sludge . The unwashed ECPs were characterized as 44% in low MW, 30% in medium MW, and 26% in high MW . Both low-MW and medium-MW fractions of unwashed ECPs decreased while high-MW fraction increased in ozonized sludge . The dewaterability of ozonized sludge, assessed by capillary suction time (CST) and specific resistance to filtration (SRF), deteriorated with ozone dose . The optimal dose of cationic polyelectrolyte increased with increasing ozone dose . The production rate and the accumulated amount of methane gas of ozonized sludge were also higher.

Water Sci Technol, 2001, 44(10), 121 - 8
Prospects and problems of sludge pre-treatment processes; Muller JA; Pre-treatment processes have been developed in order to improve subsequent sludge treatment and disposal . Disintegration of sludge solids in the aqueous phase changes the sludge structure and solubilizes organic matter . This paper provides an overview of the applications of wet disintegration in wastewater and sludge treatment . Applied disintegration techniques such as mechanical, thermal, chemical and biological methods are briefly described . The methods are compared regarding energy consumption, operational reliability and stage of development for application on wastewater treatment plants . Mechanical and thermal methods appear to be most suitable at this stage . The effects of pre-treatment on subsequent sludge treatment processes and the wastewater treatment are described . The performance of various methods is assessed . For the improvement of stabilization, mechanical and ozone treatment as well as thermal treatment perform best . Dewatering can be enhanced by thermal and freeze/thaw treatment . All methods show positive effects in the reduction of the number of pathogens . Pre-treatment leads to secondary effects like the generation of recalcitrant compounds and odor, which is mainly a problem of thermal and ozone treatment . The evaluation of capital and operational costs is difficult, because of the lack of full-scale experience . Especially thermal, freeze/thaw and biological treatments can be realized at low costs if the conditions are appropriate . Nevertheless, the economic efficiency has to be investigated critically for each individual application.

Water Res, 2001 Dec, 35(17), 4208 - 16
Characterization and distribution of esterase activity in activated sludge; Boczar BA et al.; The location and activity of esterase enzymes in activated sludge from three municipal wastewater treatment plants were characterized using model substrates and denaturing and non-denaturing polyacrylamide gel electrophoresis (PAGE) of particulate, freeze-thaw (primarily periplasmic enzymes and those associated with outer cell surfaces) and extracellular fractions of activated sludge bacteria . Particulate and freeze-thaw fractions had a similar spectrum of substrate specificity and contained significant levels of protein and esterase activity against model substrates, C2-C18 monoesters of p-nitrophenol and C2-C8 diesters of fluorescein . Esterase activity was highest with substrates that had short alkyl chains (C4) and decreased as the chain lengths increased beyond C8 . Extracellular fractions contained very low levels of protein (<0.1 mg/l) and showed no esterase activity against any of the model substrates tested . Multiple bands were observed upon analysis of particulate and freeze-thaw fractions by non-denaturing PAGE in combination with activity staining using various alpha-naphthol ester substrates (C2-C8) . Our results indicate that esterase enzymes in activated sludge are fairly diverse from a structural standpoint but exhibit a high level of functional redundancy, with different enzymes catalyzing the same reactions in different sludges . Extracellular esterase activity was totally absent for the substrates we tested and the esterase activity that we observed was closely linked to a particulate floc or cellular material.

Appl Environ Microbiol, 2002 Jan, 68(1), 365 - 71
Identification of a gene essential for sheathed structure formation in Sphaerotilus natans, a filamentous sheathed bacterium; Suzuki T et al.; Sphaerotilus natans, a filamentous bacterium that causes bulking in activated sludge processes, can assume two distinct morphologies, depending on the substrate concentration for growth; in substrate-rich media it grows as single rod-shaped cells, whereas in substrate-limited media it grows as filaments . To identify genes responsible for sheath formation, we carried out transposon Tn5 mutagenesis . Of the approximately 20,000 mutants obtained, 7 did not form sheathed structures . Sequencing of the Tn5-flanking regions showed that five of the seven Tn5 insertions converged at the same open reading frame, designated sthA . The deduced amino acids encoded by sthA were found to be homologous to glycosyltransferase, which is known to be involved in linking sugars to lipid carriers during bacterial exopolysaccharide biosynthesis . Disruption of the gene of the wild-type strain by inserting a kanamycin resistance gene cassette also resulted in sheathless growth under either type of nutrient condition . These findings indicate that sthA is a crucial component responsible for sheath formation.

Environ Sci Technol, 2001 Dec 1, 35(23), 4655 - 9
Concerted chemical and microbial degradation of sulfophthalimides formed from sulfophthalocyanine dyes by white-rot fungi; Reemtsma T et al.; 3- and 4-sulfophthalimide (SPI) have recently been shown to be the major product formed by white-rot fungi upon decolorization of sulfophthalocyanine (SPC) textile dyes . To make use of this metabolic potential in textile wastewater treatment, the fungal breakdown products should be degradable by activated sludge . Here,the aerobic degradation of SPI was studied in die-away tests, and biodegradation intermediates and degradation products were analyzed by liquid chromatography-electrospray ionization-mass spectrometry . The degradation of SPI is initiated by a chemical hydrolysis to sulfophthalamic acid (SPAA) with half-lives of 8 and 40 h at pH 6.5 for 4- and 3-SPI, respectively . Then, 4-SPAA can be mineralized by aerobic mixed cultures, while 3-SPAA remained stable throughout the experiment (35 d) . Analogously, the potential intermediate in 4-SPAA degradation, the 4-sulfophthalic acid, but not its 3-isomer, can be completely mineralized aerobically by mixed cultures . In all chemical and microbialtransformations of these aromatic sulfonates the 4-sulfo-isomer is more reactive than the 3-isomer . The triade of fission of the SPC-system by white-rot fungi to SPI, chemical hydrolysis of SPI to SPAA, and microbial degradation of SPAA offers a pathway to mineralize the major part of the SPC system of textile dyes, whether in a respective effluent treatment system or in the aquatic environment . More general, these results illustrate on a molecular level how white-rot fungi and bacteria may cooperate in mineralizing structurally complex colored substances.

Water Res, 2002 Jan, 36(1), 41 - 8
Association of coliform bacteria with wastewater particles: impact of operational parameters of the activated sludge process; Loge FJ et al.; The fraction of particles with associated coliform bacteria (PAC) in the activated sludge process was evaluated using a 16S rRNA oligonucleotide probe specific to the family Enterobacteriaceae . The PAC was found to decline exponentially with increasing mean cell residence times (MCRTs) . The factors influencing the formation of PAC, identified with simplified mass balance relationships . are the concentration of particles, the concentration of dispersed (non-particle associated) coliform bacteria, and the MCRT . The concentration of dispersed coliform bacteria was found to decline with increasing MCRTs . The rate of decline was greater than the typical half-life attributed to endogenous decay, suggesting that other factors (e.g., predation by protozoa) influence the concentration of dispersed coliform bacteria, and subsequently the formation of PAC . Given that the association of targeted organisms with particles adversely impacts the performance of a disinfection system, studies targeted at the fate of organisms other than coliform bacteria in the activated sludge process are of paramount importance in assessing the health risks of post-disinfected effluents.

Water Environ Res, 2001 Sep-Oct, 73(5), 517 - 25
Use of biodegradable dissolved organic carbon to assess treatment process performance in relation to solids retention time; Babcock RW Jr et al.; A biodegradable dissolved organic carbon (BDOC) method has been developed and used to analyze secondary- and advanced-treated wastewater effluents and to investigate correlations between residual organic content and the solids retention time (SRT) . Conventional biochemical oxygen demand (BOD) bottles and a 28-day incubation period were used . Secondary wastewater effluents from Hawaii were found to contain between 9.0 and 14.0 mg/L of dissolved organic carbon (DOC), of which 23 to 35% was biodegradable in the 28-day BDOC test (from a survey of nine treatment plants) . Bench-scale, continuous-flow activated-sludge biological reactors treating synthetic wastewater were operated at SRTs between 2 and 15 days, and effluent BDOCs were determined . A good BDOC prediction equation was developed that incorporates the initial DOC, the DOC remaining after 5 days, and the SRT of the system from which the sample originated . This equation can be used to determine the BDOC value using data that can be obtained during a conventional 5-day BOD test . The determined equation was found to be appropriate for some of the full-scale wastewater effluent survey data.

Water Res, 2001 Dec, 35(18), 4317 - 22
Acid-stimulated phosphate uptake by activated sludge microorganisms under aerobic laboratory conditions; McGrath JW et al.; Activated sludge inocula taken from five different wastewater treatment plants were grown aerobically under laboratory conditions on mineral salts medium containing either glucose or skimmed milk powder as carbon source . Cultures showed increases of between 50% and 143% in levels of phosphate uptake from the medium when the growth pH was 5.5 rather than 7.5 . Of 100 individual sludge microbial isolates studied, 34 demonstrated such acid-stimulated luxury phosphate uptake; the optimum pH for the process was shown to lie between 5.0 and 6.5 . Enhanced phosphate removal by these isolates was accompanied by increases of between 2 and 10.5-fold in their polyphosphate content; this was visualised as intracellular inclusions . Acid-stimulated luxury phosphate uptake by environmental microorganisms is a previously-unrecognised phenomenon that may have application in novel technologies for nutrient removal from wastewaters.

Water Res, 2001 Dec, 35(18), 4299 - 306
Effect of dissolved organic material and cations on freeze-thaw conditioning of activated and alum sludges; Ormeci B et al.; Freeze-thaw conditioning effectively dewaters alum and activated sludges, but it works better on alum sludge than it does on activated sludge . The main difference between alum sludge and activated sludge is that activated sludge has high concentrations of both dissolved organic material and ions . Dissolved organic material and ions may possibly alter the freezing process and decrease the effectiveness of freeze-thaw conditioning on activated sludge . The objective of this study is to investigate the effect of dissolved organic material and cations on freeze-thaw conditioning of sludges, and to improve the effectiveness of freeze-thaw conditioning on activated sludge . The results of this study show that although protein, carbohydrate and cation concentrations in activated sludge supernatant are initially high, they dramatically increase after freeze-thaw conditioning . The increase is likely to come from the release of extracellular and intracellular material to sludge supernatant . The observed increase in the DNA concentration in activated sludge supernatant after freeze-thaw conditioning indicates that freeze-thaw causes cell disruption . Alum sludge supernatant, on the other hand, initially contains low concentrations of proteins, carbohydrates and cations which do not noticeably change after freeze-thaw conditioning . When ECPs (extracellular polymers) and cations are extracted from activated sludge before freeze-thaw conditioning . the sludge settles and dewaters better after the freeze-thaw . The resulting aggregates are smaller and denser resembling the "coffee ground" aggregates of alum sludge.

Water Res, 2001 Dec, 35(18), 4277 - 84
Optimization of activated sludge reactor configuration: kinetic considerations; Scuras SE et al.; To evaluate and design staged activated sludge systems it is necessary to determine the biomass requirement for a given configuration . This depends on both kinetics and treatment requirements . We present a procedure to determine the optimum reactor configuration for a range of influent and effluent substrate concentrations, half saturation coefficients, and number of tanks in series for both inhibitory and non-inhibitory substrates . Dimensionless plots of the results show the minimum biomass requirement of the series relative to that for a single CSTR and the optimal relative sizes of the tanks . The plots may be used directly for staged system design and lead to the following conclusions: three tanks in series is generally best, high influent substrate concentrations and stringent discharge requirements increase the benefit of staging, and optimal tank sizing is significantly better than using equal sized tanks.

Biomacromolecules, 2001 Summer, 2(2), 568 - 74
Physical characteristics of poly(vinyl alcohol) and calcium alginate hydrogels for the immobilization of activated sludge; Doria-Serrano MC et al.; Hydrogels based on poly(vinyl alcohol), PVA, and calcium alginate were prepared by a freezing and thawing cycle process and characterized, in terms of the role of the polymer mixture percentage and the number of treatment cycles, on their weight swelling ratio, WSR, gel fraction, and activated sludge entrapment and immobilization . The results show that the morphology of these hydrogels is highly dependent on the PVA-Ca alginate ratio of 5 wt % total polymer content in the initial aqueous solution and that the number of entrapped microorganisms which survive the freezing-thawing procedure is independent of this ratio . For 80/20 PVA-Ca alginate hydrogels, results also show that for up to three freezing and thawing cycles, the WSR, which is in average 24, is not severely affected by the number of the cycles . For the hydrogels with three cycles, the calculated gel fraction for the composite hydrogel is 0.99 . Immobilized microorganisms from sedimented activated sludge, constituted by bacteria and fungi, die in high numbers during the freezing and thawing treatment . However, with a proper time of incubation with glucose as carbon source, the population of bacteria is recovered and mainly proliferate inside the hydrogel, attached on top of the fibril network formed by the polymers, while fungi are recovered predominantly on the surface of the spheres.

FEMS Microbiol Lett, 2001 Nov 13, 204(2), 299 - 304
Biodegradation of p-toluenesulphonamide by a Pseudomonas sp; van Haperen AM et al.; A bacterium capable of utilising p-toluenesulphonamide was isolated from activated sludge . The isolated strain designated PTSA was identified as a Pseudomonas sp . using chemotaxonomic and genetic studies . Pseudomonas PTSA grew on p-toluenesulphonamide in a chemostat with approximately 90% release of sulphate and 80% release of ammonium . The isolate was also able to grow on 4-carboxybenzenesulphonamide and 3,4-dihydroxybenzoate but did not grow on p-toluenesulphonate . The transient appearance of 4-hydroxymethylbenzenesulphonamide and 4-carboxybenzenesulphonamide during p-toluenesulphonamide degradation proves oxidation of the methyl group is the initial attack in the biodegradation pathway . Both metabolites of p-toluenesulphonamide degradation were identified by high-performance liquid chromatography-mass spectrometry . 4-Carboxybenzenesulphonamide is probably converted into 3,4-dihydroxybenzoate and amidosulphurous acid . The latter is a chemically unstable compound in aqueous solutions and immediately converted into sulphite and ammonium . Both sulphite and ammonium were formed during degradation of 4-carboxybenzenesulphonamide.

Water Sci Technol, 2001, 44(8), 123 - 32
Anaerobes, aerobes and phototrophs . A winning team for wastewater management; Gijzen HJ; Current mainstream technologies for wastewater treatment, such as activated sludge and tertiary nutrient removal, are too costly to provide a satisfactory solution for the increasing wastewater problems in developing regions . Besides, these technologies do not allow for re-use of valuable energy and nutrients contained in the wastewater . In light of these limitations, it is important to reconsider the technology and strategic approaches in wastewater management . This paper introduces the "Cleaner Production" concept to sewage management, which combines two approaches: pollution prevention and re-use . Pollution prevention includes a shift towards low water use sanitation technology . The more concentrated wastewater, becomes more attractive for re-use oriented treatment schemes . A combination of anaerobic pre-treatment followed by macrophyte-covered stabilisation ponds is proposed for the effective recovery of energy and nutrients from sewage . By selecting optimal applications of the plant biomass and pond effluent, nutrients will end up as fish and crop protein . This contrasts favourably to tertiary nitrogen removal in activated sludge systems, which recycles ammonia through molecular nitrogen at the expense of energy and high costs . Macrophyte ponds are proposed as a key step in waste recycling, because these form the central unit of a recycling engine, driven by photosynthesis . The process is energy efficient, cost effective and applicable under a wide variety of rural and urban conditions.

Environ Sci Technol, 2001 Nov 1, 35(21), 4205 - 13
Polychlorinated naphthalenes in U.K . soils: time trends, markers of source, and equilibrium status; Meijer SN et al.; Polychlorinated naphthalenes (PCNs) have been analyzed in archived soil from the U.K . to investigate historical trends . Samples were obtained from the Broadbalk experiment plots (1944-1986) and Luddington experiment station (1968-1990) . Luddington samples also include a set of soils that received a one-time sludge treatment in 1968, and duplicate samples of this archived sludge were also analyzed . Peak residues of sumPCN (sum of all PCN congeners quantified) were approximately 9000 pg g(-1) dry weight in 1956, declining to approximately 300 pg g(-1) in contemporary soils . The one-time sludge application resulted in elevated soil residues that were 1.5-6 times higher than the control plot over the time series . This increase is consistent with the known application rate and the amount of sumPCN in the applied sludge (approximately 250,000 pg g(-1) dry wt) . Half-lives forthe Luddington control soil and the sludge-amended soil for the period 1972-1990 were 5.3 and 9.9 years, respectively . Investigation of time trends revealed differences between homologue groups with the higher molecular weight congeners peaking earlier in the time series (pre-1950) and the lower molecular weight congeners peaking later, ca . 1970 . Time trends of individual congeners were investigated in terms of their relative mass percent contribution to the sum of their homologue group . Significant (p < 0.05) increasing trends were observed for several congeners associated with combustion sources (CN-29, -51, -52/60, -54, and -66/67) suggesting that combustion related sources are more important now than they were in the past . However, no decreasing trend was observed for congeners that were thought to be susceptible to degradation by photolysis suggesting that this may not be a key elimination pathway of PCNs in the environment . A simple calculation of the fugacity status of PCNs in air and soil showed that the tri-CNs are exhibiting net outgassing, while the penta-CNs are still being deposited to soil . Interestingly, the penta-CNs associated with combustion show the largest gradient for air-to-soil transfer, supporting the notion that combustion sources are important contributors to contemporary air burdens of these congeners.

Water Sci Technol, 2001, 44(6), 63 - 6
The role of blending in polymer conditioning of waste activated sludge; Erdincler A et al.; This paper presents the results of an investigation on the role of blending in sludge polymer conditioning by evaluating the polymer consumption, and measuring the capillary suction time of waste activated sludge samples blended for different time periods . All of the sludge samples, including non-blended control samples, were conditioned by a cationic high molecular weight polymer in desired concentrations . The protein concentrations of the sludge samples increased as a biological confirmation of cell disruption or desorption of some part of biological polymers present in sludge . Blending decreased the critical polymer dosages required to condition the waste activated sludge samples depending on the blending time applied to the samples.

Waste Manag, 2001, 21(8), 717 - 24
Sequential (anaerobic/aerobic) biological treatment of Dalaman SEKA pulp and paper industry effluent; Tezel U et al.; In the pulp and paper industry, lignin and other color compounds are removed by chemical agents in bleaching process . Use of chlorine-based agents results in production of degradation products which include various chloro-organic derivatives . Since these new compounds are highly chlorinated, they cause a problem in the treatment of pulp and paper industry wastewaters . Chemical precipitation, lagooning, activated sludge, and anaerobic treatment are the processes used for treating pulp and paper effluents . Furthermore, a combination of these processes is also applicable . In this study, the effluent of Dalaman SEKA Pulp and Paper Industry was examined for its toxic effects on anaerobic microorganisms by anaerobic toxicity assay . Additionally, this wastewater was applied to a sequential biotreatment process consisting of an upflow anaerobic sludge blanket as the anaerobic stage and a once-through completely mixed stirred tank as the aerobic stage . Results indicated that: (1) Dalaman SEKA Pulp and Paper Industry wastewater exerted no inhibitory effects on the anaerobic cultures under the studied conditions, and (2) application of a sequential biological (anaerobic/aerobic) system to treat the Dalaman SEKA Pulp and Paper Industry wastewater resulted in approximately 91% COD and 58% AOX removals at a HRT of 5 and 6.54 h for anaerobic and aerobic, respectively.

Waste Manag, 2001, 21(8), 695 - 702
A comparative adsorption/biosorption study of mono-chlorinated phenols onto various sorbents; Aksu Z et al.; The potential use of dried activated sludge and fly ash as a substitute for granular activated carbon for removing mono-chlorinated phenols (o-chlorophenol and p-chlorophenol) was examined . The pollutant binding capacity of the adsorbent/biosorbent was shown to be a function of substituted group, initial pH and initial mono-chlorinated phenol concentration . The working sorption pH value was determined as 1.0 and the equilibrium uptake increased with increasing initial mono-chlorinated phenol concentration up to 500 mg dm(-3) for all the mono-chlorinated phenol-sorbent systems . The suitability of the Freundlich, Langmuir and Redlich-Peterson adsorption models to the equilibrium data were investigated for each mono-chlorinated phenol-sorbent system . The results showed that the equilibrium data for all the mono-chlorinated phenol-sorbent systems fitted the Redlich-Peterson model best within the concentration range studied.

Ambio, 2001 Aug, 30(4-5), 282 - 6
The pollution and protection of the inner Oslofjord: redefining the goals of wastewater treatment policy in the 20th century; Arnesen V; The main source of pollution in the inner Oslofjord in the 20th century has been municipal sewage discharges from the city of Oslo . At the beginning of the 20th century, pollution was limited to the coastal waters and the harbor area of Oslo, in the vicinity of sewer outlets . High bacteria content caused a health hazard that city authorities attempted to reduce by constructing a sewerage system, including intercepting sewers and wastewater-treatment plants . Due to population growth, the impact area of increasing wastewater loading expanded . The entire inner Oslofjord was found to be affected in the 1930s . Scientific studies linked municipal sewage discharges to an increase in the algal production . In the 1940s, the bottom layers were found to be anoxic . The Oslo sewerage authorities were aware of the fjord's pollution, but regarded organic matter as the major problem and the activated sludge method as the best solution . The role of nutrients was not commonly acknowledged until in the late 1960s . Phosphorus removal was taken into use in the 1970s, and nitrogen removal was introduced in the late 1990s . Removal of nutrients has resulted in the slow recovery of the fjord.

Water Sci Technol, 2001, 44(5), 161 - 9
Subcritical wet oxidation of municipal sewage sludge: comparison of batch and continuous experiments; Lendormi T et al.; Wet oxidation in subcritical conditions is a new alternative to usual routes for sewage sludge treatment and it complies with environmental standards . The paper presents tests carried out on a batch reactor and on a continuous pilot unit, treating municipal sewage sludge . A method is proposed that shows that the oxidation efficiency in a continuous reactor can only be easily predicted from the residence time distribution and batch tests results . Nevertheless, a partial settling of the solid residue in the continuous bubble column reactor is evident, and it increases the solid residence time and then decreases its organic content with respect to a similar batch test . In addition, these results highlight the considerable influence of temperature in the oxidation reactor and of the type of sewage sludge which is treated . At temperatures around 240 degrees C, foaming can seriously impair the operation of the continuous reactor, because of the presence of non-degraded fatty compounds and surfactants . Moreover, the COD reduction is limited to 70% . On the contrary, at 300 degrees C, COD removal efficiency greater than 80% is achieved without any catalyst additive and, in addition, only highly biodegradable compounds remain in the oxidised liquor.

Biodegradation, 2001, 12(1), 31 - 7
How adaptation and mass transfer control the biodegradation of linear alkylbenzene sulfonate by activated sludge; Rittmann BE et al.; We use a nonsteady-state model to evaluate the effects of community adaptation and sorption kinetics on the fate of linear alkylbenzene sulfonate (LAS) in batch experiments conducted with activated sludge that was continuously fed different concentrations of LAS . We observed a sharp decrease in the biodegradation rate between 30 and 60 minutes and the presence of an LAS residual at the end of the batch experiments . The modeling analysis indicates that these phenomena were caused by relatively slow inter-phase mass transport of LAS . The modeling analyses also showed that the amount of LAS-degrading biomass increased when the continuous activated sludge was fed a higher LAS concentration . Although community adaptation to LAS involved accumulation of more LAS degraders, the increase was not proportional to the feed concentration of LAS, which supports the concept that LAS degraders also utilized portions of the general biochemical oxygen demand (BOD) fed to the continuous activated sludge systems.

Biodegradation, 2001, 12(1), 23 - 9
Aerobic biotransformation of 4-fluorocinnamic acid to 4-fluorobenzoic acid; dos Santos LM et al.; The biotransformation of 4-fluorocinnamic acid (FCA) using non-acclimated industrial activated sludge was investigated . FCA is a common intermediate in organic synthesis, and it is often present in aqueous waste streams . Hence, the biotransformation reactions this compound undergoes when exposed to activated sludge micro-organisms should be understood before waste streams are sent to biological wastewater treatment plants (WWTPs) . FCA biotransformation was monitored using a wide range of analytical techniques . These techniques were used to monitor not only FCA disappearance, but also the formation of degradation products, in order to propose the metabolic pathway . FCA was biotransformed to 4-fluorobenzoic acid via the formation of 4-fluoroacetophenone . The removal of FCA up to 200 mg L(-1) followed first order kinetics . The half-lives for removal of FCA from the test solutions supplied with 200 mg L(-1), 100 mg L(-1), and 50 mg L(-1) were 53, 18, and 5 hours respectively.

Environ Microbiol, 2001 Sep, 3(9), 551 - 60
Design and application of oligonucleotide probes for fluorescent in situ identification of the filamentous bacterial morphotype Nostocoida limicola in activated sludge; Liu JR et al.; 16S rRNA targeted probes, designed using sequence data from pure cultures of the three morphotypes of the filamentous bulking bacteria Nostocoida limicola I, II and III and their successful application to the in situ identification of these bacteria in activated sludge biomass samples are described here . Two probes were required to detect all the sequenced N . limicola II isolates . Results from fluorescent in situ hybridization suggest that the morphotypes N . limicola I and II contain at least two phylogenetically unrelated bacteria . The N . limicola II filaments that did not respond to the probes designed in this study fluoresced instead with the probes previously designed for the alpha-Proteobacteria . The data also suggest that both N . limicola I and III can exist in activated sludge as single, paired or clumped cells and thus in a form not recognizable microscopically as this morphotype . Some N . limicola II filaments which responded to the probes designed here were much thinner than the filaments conventionally 'identified' as this morphotype and better fitted the descriptions often used in the literature for N . limicola I.

Appl Environ Microbiol, 2001 Nov, 67(11), 4963 - 74
Accumulation of polyhydroxyalkanoic acid containing large amounts of unsaturated monomers in Pseudomonas fluorescens BM07 utilizing saccharides and its inhibition by 2-bromooctanoic acid; Lee HJ et al.; A psychrotrophic bacterium, Pseudomonas fluorescens BM07, which is able to accumulate polyhydroxyalkanoic acid (PHA) containing large amounts of 3-hydroxy-cis-5-dodecenoate unit up to 35 mol% in the cell from unrelated substrates such as fructose, succinate, etc., was isolated from an activated sludge in a municipal wastewater treatment plant . When it was grown on heptanoic acid (C(7)) to hexadecanoic acid (C(16)) as the sole carbon source, the monomer compositional characteristics of the synthesized PHA were similar to those observed in other fluorescent pseudomonads belonging to rRNA homology group I . However, growth on stearic acid (C(18)) led to no PHA accumulation, but instead free stearic acid was stored in the cell . The existence of the linkage between fatty acid de novo synthesis and PHA synthesis was confirmed by using inhibitors such as acrylic acid and two other compounds, 2-bromooctanoic acid and 4-pentenoic acid, which are known to inhibit beta-oxidation enzymes in animal cells . Acrylic acid completely inhibited PHA synthesis at a concentration of 4 mM in 40 mM octanoate-grown cells, but no inhibition of PHA synthesis occurred in 70 mM fructose-grown cells in the presence of 1 to 5 mM acrylic acid . 2-Bromooctanoic acid and 4-pentenoic acid were found to much inhibit PHA synthesis much more strongly in fructose-grown cells than in octanoate-grown cells over concentrations ranging from 1 to 5 mM . However, 2-bromooctanoic acid and 4-pentenoic acid did not inhibit cell growth at all in the fructose media . Especially, with the cells grown on fructose, 2-bromooctanoic acid exhibited a steep rise in the percent PHA synthesis inhibition over a small range of concentrations below 100 microM, a finding indicative of a very specific inhibition, whereas 4-pentenoic acid showed a broad, featureless concentration dependence, suggesting a rather nonspecific inhibition . The apparent inhibition constant K(i) (the concentration for 50% inhibition of PHA synthesis) for 2-bromooctanoic acid was determined to be 60 microM, assuming a single-site binding of the inhibitor at a specific inhibition site . Thus, it seems likely that a coenzyme A thioester derivative of 2-bromooctanoic acid specifically inhibits an enzyme linking the two pathways, fatty acid de novo synthesis and PHA synthesis . We suggest that 2-bromooctanoic acid can substitute for the far more expensive (2,000 times) and cell-growth-inhibiting PHA synthesis inhibitor, cerulenin.

J Biotechnol, 2001 Dec 28, 92(2), 95 - 101
Treatment of urban wastewater in a membrane bioreactor at high organic loading rates; Holler S et al.; Membrane bioreactors can replace the activated sludge process and the final clarification step in municipal wastewater treatment . The combination of bioreactor and crossflow microfiltration allows for a high chemical oxygen demand (COD) reduction of synthetic wastewater . From biomass, grown at high production rates in the aerobic bioreactor, energy rich biogas can be obtained in a subsequent anaerobic bioreactor . In this paper, experimental data from a laboratory scale membrane bioreactor are presented . The degradation of synthetic wastewater at short hydraulic retention times down to 1.5 h has been studied . The organic loading rate (OLR) has been varied in the range of 6-13 kg m(-3) per day . At steady state a high quality filtrate could be obtained at different operating conditions . At biomass concentrations of 10-22 g l(-1), COD reduction was above 95%.

Nippon Hoigaku Zasshi, 2001 Jul, 55(2), 247 - 54
{Legal and technical issues of formalin disposition in association with autopsy}; Nakajima M et al.; The Ministry of Public Welfare notified on the disposition of formalin, which was used in the histological examination in association with forensic or pathological autopsy . However, those who concerned on the issue had not known exactly how they dispose formalin . The news on the illegal disposition of formalin from our department drew attention to the legal disposition of formalin . These situations led us to investigate the legal and technical aspects of formalin disposition . We examined the legally-described methods such as oxidation, incineration and activated sludge processes and other methods such as formose, supercritical water oxidation, and wet oxidation processes . From legal point of view, we must process poisonous formaldehyde into non-poisonous products under the control of The Poisonous and Peleterious? Substances Control Law . Additionally, the products are under the control of The Sewage Water Law and Water Pollution Control Law, particularly in terms of Biological Oxygen Demand (BOD) . After careful investigation, we tentatively conclude that incineration method is the best at present, though the supercritical oxidation and wet oxidation processes may be better in order to cope with the worldwide movement toward the control of environmental hormones and warm climate.

J Environ Sci (China), 2001 Apr, 13(2), 157 - 63
Membrane bioreactor process of organic wastewater from brassylic acid manufacturing plant; Wu ZC et al.; The wastewater treatment from brassylic acid manufacturing plant using membrane bioreactor (MBR) was studied . The membrane bioreactor consisted of batch-operation biological aeration tank and ultrafiltration evaluation tank . The content of test included the affection of variation operation conditions on ultrafiltration separation, the general characteristics of MBR process, and the difference comparing with the conventional biological treatment . The results are as follows: (1) among the test membrane material, polyether sulphone (PES) membrane is more suitable for the wastewater treatment; (2) when the cutoff molecular weight is among 10,000-50,000, the higher the cutoff molecular weight, the bigger the water flux is in the test; (3) under the operation pressure, water flux increases accompanying with the increasing of operation pressure; (4) the paper filtered COD concentration has more affection on the water flux than the suspended solid concentration; (5) as the volume loading of MBR increases, the accumulation of high molecule organic substance and colloid increases, the membrane permeate COD concentration and paper filtered COD concentration increase too, meanwhile the water flux reduces; (6) when the sludge retention time of activated sludge of MBR increases, the accumulation of high molecule organic substance and colloid reduces, the membrane permeate COD concentration and paper filtered COD concentration reduce too, and the water flux increases; (7) comparing with the conventional biological process, the microbial activity is higher, but the microbial species is less.

J Environ Sci (China), 2001 Jan, 13(1), 46 - 50
Simultaneous nitrogen and phosphorus removal under low dissolved oxygen conditions; Xia SQ et al.; A full-scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal . When the influent concentrations of CODcr, TN and TP varied in a range of 352.9 mg/L-1338.2 mg/L, 34.4 mg/L-96.3 mg/L, and 2.21 mg/L-24.0 mg/L, the average removal efficiencies were 94.9%, 86.7% and 93.0%, respectively . During the test period of two months, effluent means of CODcr, BOD5, NH3-N, TN and TP were below 50 mg/L, 25 mg/L, 10 mg/L and 1.0 mg/L, respectively . The low dissolved oxygen activated sludge process has a simple flow sheet, fewer facilities and high N and P removal efficiency . It is very convenient to retrofit the conventional activated sludge process with the above process.

J Microbiol Methods, 2001 Oct, 47(1), 17 - 24
Analytical precision and repeatability of respiratory quinones for quantitative study of microbial community structure in environmental samples; Hu HY et al.; Microbial community structure is one of the important factors controlling the pollutant-degrading capacity of ecosystems . The analysis of microbial quinones has gained increased recognition as a simple and useful approach for studying microbial structure in environmental samples . The analytical precision of quinone characterization using high performance liquid chromatograph (HPLC) with a UV-detector was studied in this study . Activated sludge was used as a typical mixed culture . The coefficient of variation of quinone content was lower than 6%, and that of microbial diversity calculated from the composition of quinones was as low as 3% . Statistical analyses on the analytical precision of quinones demonstrated that the critical value of dissimilarity between two quinone profiles of activated sludge, which is used to make a judgement whether the two quinone profiles are different or not, is 0.1 for the analytical method used in this study . The values of minimum biomass required for quinone analysis to have a reliable analytical result of microbial quinones were 2 mg-dry-cell for activated sludge.

Water Environ Res, 2001 Mar-Apr, 73(2), 237 - 42
A test for predicting propensity of activated sludge to acute filamentous bulking; Seka MA et al.; Filamentous bulking is a solid-liquid separation problem well known to activated-sludge plant operators . The use of curative additives is a rather delicate solution and the tools developed to anticipate it seem limited . To complement existing sludge sedimentation monitoring tools, a new test to assess the propensity of activated sludge for filamentous bulking was developed . It consists of challenging the sludges by feeding them under conditions favoring filamentous bacteria for 24 hours . The effects of such an acute treatment on sludge settleability is subsequently assessed through a simple sludge volume (SV30) measurement with reference to a control . The sludge can then be evaluated as prone to bulking (unstable sludge) or not (stable sludge) . Such a test can be used to predict the occurrence of filamentous bulking in activated-sludge treatment plants . This so-called acute bulking test requires simple equipment and can be done by any wastewater treatment plant operator.

Water Environ Res, 2001 Mar-Apr, 73(2), 146 - 53
Design of a sequencing batch reactor sequence with an input load partition in a simulation-based experimental environment; Hvala N et al.; A study is presented that considers optimization of a sequencing batch reactor (SBR) operational sequence . Optimization is performed with the aid of a laboratory pilot plant and a process model . The model was included in the study to facilitate a search for optimal operating conditions because performing experiments solely on the pilot plant would be rather extensive, expensive, and time-consuming . The model used in the study is the well-known Activated Sludge Model No.1 with minor modifications . The optimization addresses a split-feed operating mode with input load partitioned into two parts and with two successions of aerobic-anoxic phases . In the study, the duration of batch phases and the time of the second input addition are optimized so that the desired effluent nitrogen concentration is achieved and the need for external carbon addition in the anoxic phase is reduced or eliminated . When an optimal SBR sequence computed by the model was verified on the pilot plant, better performance of the actual process was also achieved, although some phenomena were observed that were not predicted by the model . Results of the study indicate that the available wastewater treatment plant models, although a simplification of reality, can be usefully applied for process optimization.

Water Res, 2001 Oct, 35(15), 3599 - 604
Determination of short-chained poly(ethylene glycols) and ethylene glycol in environmental samples; Szymanski A et al.; A method for the determination of ethylene glycol (EG), di(ethylene glycol) (E2) and tri(ethylene glycol) (E3) in environmental samples (raw and treated sewage, river water) has been developed . These substances are important by-products in the biotransformation of non-ionic surfactants (NS) . The method is based on sequential liquid-liquid extraction with ethyl acetate and chloroform (resulting in the separation of poly(ethylene glycols) (PEG) and EG from the water matrix), precipitation of long-chained PEG (PEGlch) with Dragendorff reagent, extraction of short-chained PEG (PEGsh) (EG, E2 and E3) from a filtrate with chloroform and the final determination using alternating current voltammetry . The precision of the method is 7.3%, the recovery 95% and a detection limit of 1.5 microg in the sample, i.e . 10 microg l(-1) was achieved . As evidenced by F and t tests, the developed method is equivalent to the indirect PEGsh determination by the difference approach where concentration of PEGsh is determined by the difference of the total PEG and PEGlch . The PEGsh fraction was found to be present in considerable concentrations in raw and treated sewage, river water, as well as being a major biotransformation by-product in the continuous flow activated sludge testing of fatty alcohol ethoxylates.

Water Res, 2001 Oct, 35(15), 3595 - 8
The role of extracellular exopolymers in the removal of phosphorus from activated sludge; Cloete TE et al.; Biological phosphorus removal in activated sludge systems is thought to be a result of the action of polyphosphate accumulating organisms (PAO) . However, not all phosphorus removed can be accounted for by PAO . A method for the qualitative in situ characterization of PAO cell clusters and closely associated extracellular exopolymers (EPS) is described . X-ray microanalysis was performed on samples from two activated sludge plants situated in Pretoria, South Africa . Analysis was done by means of scanning electron microscopy combined with energy dispersive spectrometry (EDS) . Cell clusters with associated EPS, on average, contained between 57% and 59% phosphorus, while EPS alone contained, on average, between 27% and 30% phosphorus . Results suggest that phosphorus removal in activated sludge might be due not only to PAO, but also by EPS acting as a phosphorus reservoir.

Water Environ Res, 2001 May-Jun, 73(3), 295 - 300
Enhanced biological phosphorus removal in an anaerobic-aerobic sequencing batch reactor: characteristics of carbon metabolism; Jeon CO et al.; Carbon metabolism of activated sludge performing enhanced biological phosphorus removal (EBPR) was investigated in a sequencing batch reactor (SBR), where glucose and acetate were supplied as carbon sources . There have been reports that EBPR often failed because of outgrowth of G-bacteria, which are able to use glycogen (or glucose) alone instead of glycogen and polyphosphate as an internal energy storage pool for the anaerobic uptake and storage of acetate . However, in this experiment, complete EBPR was achieved without proliferation of G-bacteria despite the supply of glucose in addition to the acetate . Additional one-cycle SBR operation was carried out to investigate the detailed metabolism of glucose and acetate . Acetate-using, phosphorus-accumulating organisms (PAOs) could use glucose as a source for the anaerobic polyhydroxyalkanoate (PHA) synthesis from acetate . However, glucose and acetate were metabolized separately through independent metabolic pathways by respective microorganisms: acetate-using PAOs, lactate-producing organisms (LPOs), and lactate-using PAOs . Glucose was rapidly converted to lactic acid by LPOs before acetate-using PAOs used the glucose as an energy source for the anaerobic PHA synthesis from acetate and the lactateusing PAOs anaerobically synthesized PHA from lactate at the expense of polyphosphate . The EBPR was accomplished by acetate-using PAOs and lactate-using PAOs independently when glucose acetate were supplied together.

Water Environ Res, 2001 Jan-Feb, 73(1), 30 - 6
Influence of cations on activated-sludge effluent quality; Murthy SN et al.; Laboratory experiments and field tests were conducted to determine the effect of inorganic cations on effluent from activated-sludge systems . Laboratory experiments showed that monovalent cations tend to increase the concentration of solution biological polymers (biopolymers), whereas divalent cations tend to retain the biopolymers in the floc . Biopolymers in solution affect effluent chemical oxygen demand (COD) . Coagulation tests were performed on the effluent with ferric chloride . Ferric hydroxide can coagulate protein through possible adsorptive interactions and may be responsible for some biopolymer retention in the flocs . In the field study, it was found that sodium ions in the influent wastewater caused an increase in proteins and polysaccharides in solution, thereby increasing the effluent COD concentration of the treated municipal wastewater . The attachment or release of these microbially derived organic biopolymers and recalcitrant influent substrate may depend on the monovalent-to-divalent cation ratio and the concentration of iron . Modeling of effluent organics in the activated-sludge process can be enhanced through incorporation of concepts that take into account the partitioning (between floc and solution) of microbial biopolymers and influent recalcitrant substrate.

J Appl Microbiol, 2001 Sep, 91(3), 563 - 9
Towards a quantitative risk assessment for BSE in sewage sludge; Gale P et al.; AIMS: The aim is to determine the risk of transmission of BSE to humans and cattle through the application of sewage sludge to agricultural land . METHODS AND RESULTS: A quantitative risk assessment based on the Source-Pathway-Receptor approach is developed . Central to the model is the estimation of the arithmetic mean concentration of BSE agent in sewage sludge . The main sources of uncertainty in the risk assessment are the degree to which sewage sludge treatment destroys BSE agent, whether there is a threshold dose for initiation of BSE infection in cattle, and most importantly, the amount of brain and spinal cord material which enters the sewer from the abattoir . Assuming 1% of brain and spinal cord is lost to the sewer from abattoirs, the model predicts a risk of BSE transmission of 7.1 x 10(-5) cow(-1) year(-1) for cattle grazing on land to which sewage sludge has been applied . CONCLUSION: The risks to humans through consumption of vegetable crops are acceptably low . Although the risks to cattle are higher, because of higher exposure to soil and greater susceptibility, the model demonstrates that sewage sludge alone cannot sustain the BSE epidemic in the UK cattle herd . Furthermore, the model suggests that recycling of BSE agent through sewage sludge will not sustain endemic levels of BSE in the UK cattle herd . SIGNIFICANCE AND IMPACT OF THE STUDY: The conclusions are consistent with the findings from epidemiological studies which so far have not detected horizontal transmission of BSE (which would include transmission from contaminated pastures) . The model demonstrates the importance of containment of brain and spinal cord within the abattoir.

Bioresour Technol, 2001 Oct, 80(1), 19 - 28
Batch co-digestion of multi-component agro-wastes; Misi SN et al.; In certain parts of the developing world conventional energy supplies such as electricity, gas, coal and petroleum by-products are either unavailable, too capital intensive to install, are unjustifiable due to low population densities in some semi-arid regions, or are simply unaffordable to the target population . In Zimbabwe, it has been assessed that only biomass energy can conveniently provide both lighting and space heating . Therefore, means of generating biogas from agricultural and other organic wastes, and to encourage their use is a policy which has been adopted by Zimbabwe's Department of Energy . In this study cattle slurry was mixed with a range of solid wastes and allowed to digest in 11 batch digesters . The mixtures which were used were selected on the basis of centroid design with the objective of determining whether there was either synergism or antagonism . Two trials were carried out, one based on cattle slurry, chicken manure (CM) and molasses (Mol), the other based on sheep and goat manure, chicken manure and surplus activated sludge . The criteria for judging the success of a co-digestion were volatile solids (VS) reduction, total methane production and methane yield . In the first trial, the analysis based on the methane yield showed that there was no antagonism and that the mixture of 30% cattle slurry/30% CM/40% Mol gave a synergistic effect . The analysis based on the VS destruction, however, did show that there was some very slight antagonism . In the second trial, the analysis based on the methane yield showed that there was both antagonism and synergism and that the synergism produced an extra 6.7% methane . The analysis based on the VS destruction also showed that there was both antagonism and synergism but that the effects were small.

Water Sci Technol, 2001, 44(2-3), 69 - 76
Operating space diagrams: a tool for designers of wastewater treatment plants; Hopkins LN et al.; Recent years have seen the introduction of new and varied designs of activated sludge plants . With increasing needs for higher efficiencies and lower costs, the possibility of a plant that operates more effectively has created the need for tools that can be used to evaluate and compare designs at the design stage . One such tool is the operating space diagram . It is the aim of this paper to present this tool and demonstrate its application and relevance to design using a simple case study . In the case study, use of the operating space diagram suggested changes in design that would improve the flexibility of the process . It also was useful for designing suitable control strategies.

Water Sci Technol, 2001, 44(2-3), 453 - 9
Isolation of copper-binding proteins from activated sludge culture; Fukushi K et al.; Six copper-binding microbial proteins were isolated from activated sludge cultures grown on media containing copper at various concentrations . Molecular weights among isolated proteins were ranged from 1.3k to 1 74k dalton . Isolated proteins were compared for their copper binding capabilities . Proteins isolated from cultures grown in the presence of copper in the growth media exhibited higher copper binding capabilities than those isolated from the culture grown in the absence of copper . The highest metal uptake of 61.23 (mol copper/mol protein) was observed by a protein isolated from a culture grown with copper at a concentration of 0.25 mM . This isolated protein (CBP2) had a molecular weight of 24k dalton . Other protein exhibited copper binding capability of 4.8-32.5 (mol copper/mol protein).

Water Sci Technol, 2001, 44(2-3), 445 - 52
Evaluation of an ozonation system for reduced waste sludge generation; Egemen E et al.; The ultimate disposal of biosolids has been and continues to be one of the most expensive problems faced by wastewater utilities . Previous work has shown that the waste sludge generation in an activated sludge plant can be reduced by promoting cryptic growth conditions (i.e., biomass growth on intracellular products) . For this purpose, excess biosolids from a continuous flow activated sludge system were solubilized using ozone as the cell lysing agent, and then returned to the aeration tank . The results of these preliminary studies indicate that the proposed process configuration has the potential to reduce the waste sludge production by 40% to 60% . In the present research, the details of the ozonation process is further investigated to determine the maximum solubilization efficiency . For this purpose, a number of variables such as the solids concentration in the excess sludge, ozonation time, and ozonation dosage rate are studied.

Water Sci Technol, 2001, 44(2-3), 417 - 25
Effects of solids concentration on activated sludge deflocculation, conditioning and dewatering; Mikkelsen LH et al.; Optimum conditioning of activated sludge in terms of minimum CST was shown to correspond to the complete removal of turbidity, and the increase in turbidity with shear due to e.g . pumping is therefore expected to affect conditioning . The optimum polymer dosage was directly related to the turbidity of activated sludge after two minutes shear, and was considerably lower than the dosage required for charge neutralisation . The turbidity produced by shear increased more than is proportional with solids concentration and was directly related to the apparent viscosity . It is suggested that increasing solids concentration causes increased surface erosion when network structures are broken, and this causes increases in turbidity and required polymer dosage per solids mass . For Aby activated sludge, optimum polymer dosage per solids mass increased by 52% when the solids concentration was increased from 8.2 to 13.7 g SS/l . Modelling of the effect of solids concentration predicts even higher increases in required polymer dosage for higher solids concentrations . This means that reduced thickening prior to pumping and conditioning may be desirable when the hydraulic capacity of the dewatering device is sufficient . Similar trends were observed for an anaerobically digested sludge . For this sludge, reduction of turbidity with FeCl3 reduced the polymer demand.

Water Sci Technol, 2001, 44(2-3), 373 - 9
Municipal wastewater sludge dewaterability and the presence of microbial extracellular polymer; Houghton JI et al.; Dewatering of sewage sludge is an essential and costly part of the wastewater treatment process . The presence of microbial extracellular polymer (ECP) is important for sludge flocculation, but ECP has also been shown to have a detrimental effect on the dewaterability of certain sludge types . This paper investigates the relationship between sludge dewaterability and the level of ECP present in a range of sludges obtained from 8 full-scale municipal treatment works in the UK . Sludge dewaterability was determined using the capillary suction time (CST) test, and a thermal extraction process followed by solvent precipitation was used for ECP extraction . The results indicate that for each type of sludge examined there appears to be an optimum level of ECP (raw sludge 20 mg ECP/g SS; activated sludge 35 mg ECP/g SS; digested sludge 10 mg ECP/g SS) at which the sludge should exhibit maximum dewaterability . The establishment of a trend between sludge dewaterability and the quantity of ECP present opens up the possibility of manipulating the level of microbial polymer present to aid sludge dewatering, and hence reduce plant operating costs.

Water Sci Technol, 2001, 44(2-3), 227 - 34
Modelling to solve odour problems; Childs PS et al.; The use of dispersion modelling is a powerful tool to establish levels of treatment required to remove odour complaints . Odour is an extremely sensitive issue and is key to the public perception of wastewater environmental protection . This paper describes a case study of the successful resolution of long-standing odour problems at the East Worthing Wastewater Treatment Works (WTW), on the South Coast of England, utilising modelling and appropriate treatment technologies . A number of odour surveys have been conducted on the site to identify the major sources on the works, which were found to be the sludge press house and the primary settlement tanks, situated only 10 metres from the nearest properties . As a result attempts to resolve the odour problem have been made including the covering of identified sources, treating extract using activated carbon filters and installing perfume sprays . During the site development all sources were contained and ventilated to a 60,000 m3/hr Jones & Attwood ODORGARD unit . Its requirement was to ensure that no receptor was exposed to a concentration in excess of 4 ouEm3 (Odour units), in accordance with the odour planning condition . Dispersal modelling was performed to determine the maximum permissible outlet concentration . The results of the modelling exercise established that emissions from the odour control plant should not exceed 675 ouEm3 to ensure that the receptor standard was attained . An optimisation programme was conducted to ensure that the unit was providing the optimum level of treatment prior to taking the olfactometry samples . Following the plant's optimisation the results of the olfactometry analysis confirmed that the discharge levels were below the required 670 ouEm3 . Since completion of the sludge treatment centre scheme there have been no registered odour complaints directed at the East Worthing WTW, and the local air quality has been greatly improved for the residents surrounding the works.

Water Sci Technol, 2001, 44(2-3), 203 - 10
Applying fine bubble aeration to small aeration tanks; Duchene P et al.; Because the aeration system in an activated sludge plant typically represents a large part of the total energy requirements, designers and operators need accurate oxygen transfer information to make the aeration system as energy efficient as possible . This paper presents clean water tests performed at 38 wastewater treatment plants . The Specific Aeration Efficiency results (SAE, kgO2/kWh) are reported for: (1) large open channels (volume higher than 1000 m3), (2) small open channels, (3) total floor coverage cylindrical tanks, and (4) cylindrical tanks with a grid arrangement . Some practical guidelines can be drawn, some of them being: (1) high SAE can be achieved at small aeration tanks (< 1000 m3), applying cylindrical tanks with a total floor coverage arrangement of diffusers, volumetric blowers, and moderate air flow rates per diffuser area; (2) the high investment cost of this configuration can be justified with respect to a grid layout characterized by spiral liquid circulation which affects the oxygen transfer; (3) small open channels can meet sufficient SAE values but fail to meet in this range of tank volumes those of total floor coverage cylindrical tanks.

Water Sci Technol, 2001, 44(2-3), 197 - 202
Mass balance for on-line alphakLa estimation in activated sludge oxidation ditch; Chatellier P et al.; The capacity of an aeration system to transfer oxygen to a given activated sludge oxidation ditch is characterised by the alphakLa parameter . This parameter is difficult to measure under normal plant working conditions . Usually this measurement involves off-gas techniques or static mass balance . Therefore an on-line technique has been developed and tested in order to evaluate alphakLa . This technique deduces alphakLa from a data analysis of low cost sensor measurement: two flow meters and one oxygen probe . It involves a dynamic mass balance applied to aeration cycles selected according to given criteria . This technique has been applied to a wastewater treatment plant during four years . Significant variations of the alphakLa values have been detected while the number of blowers changes . This technique has been applied to another plant during two months.

Water Sci Technol, 2001, 44(2-3), 155 - 62
Monitoring and troubleshooting of non-filamentous settling and dewatering problems in an industrial activated sludge treatment plant; Kjellerup BV et al.; A large industrial activated sludge wastewater treatment plant had temporary problems with settling and dewatering of the sludge . Microscopical investigations revealed that the poor settling properties were not due to presence of filamentous bacteria, but poor floc properties . In order to characterise the changes in floc properties that led to settling and dewatering problems and to find reasons for this taking place, a comprehensive monitoring program was conducted during more than one year . The monitoring program included various measurements of floc settleability, floc strength and sludge dewaterability . The monitoring program revealed that a deterioration of the floc strength and the settling properties in the process tanks was closely connected to downstream dewatering problems and poor effluent quality . Particularly severe problems were observed a few weeks after the production at the factory had started after summer closedown . Possible reasons for the changes in floc properties in the process tanks were found by a) analysing change in wastewater composition by evaluating the different production lines in the industrial plant, b) evaluating the operation of the plant, and c) performing short-term laboratory experiments testing factors that could potentially affect floc properties (absence of oxygen, presence of sulphide, detergents, etc) . Among several measured parameters, the use of floc strength measurements in particular proved useful to monitor the activated sludge floc properties at this industrial plant . The described strategy can be useful in general to find and solve many solid/liquid separation problems in activated sludge wastewater treatment plants.

Water Res, 2001 Oct, 35(14), 3502 - 7
High-speed sludge freezing; Chen LC et al.; The investigation examined the feasibility of applying a "high-speed freezing technique, using liquid nitrogen freezing, to condition activated sludges and alum sludges . Experimental results indicate that the freezing speed is much faster than that adopted in most previous works on sludge freezing . Although the filterability and settleability of the alum sludge is improved by 3-min liquid nitrogen freezing, no similar improvement is observed for activated sludge . Moreover, curing affects neither sludge after liquid nitrogen freezing, but affects the slow-freezing activated sludge.

Water Res, 2001 Oct, 35(14), 3325 - 36
Quantifying filamentous microorganisms in activated sludge before, during, and after an incident of foaming by oligonucleotide probe hybridizations and antibody staining; Oerther DB et al.; Quantitative oligonucleotide probe hybridizations, immunostaining, and a simple foaming potential test were used to follow an incident of seasonal filamentous foaming at the Urbana-Champaign Sanitary District, Northeast Wastewater Treatment Plant . A positive correlation was observed between an increase in foaming potential and the appearance of foam on the surfaces of aeration basins and secondary clarifiers . In addition, during the occurrence of foaming, the mass and activity of Gordonia spp . increased as measured by fluorescence in situ hybridization, antibody staining, and quantitative membrane hybridization of RNA extracts . An increase in Gordonia spp . rRNA levels from 0.25 to 1.4% of total rRNA was observed using quantitative membrane hybridizations, whereas during the same period, the fraction of mixed liquor volatile suspended solids attributed to Gordonia spp . increased from 4% to more than 32% of the total mixed liquor volatile suspended solids . These results indicate that both the activity and biomass level of Gordonia spp . in activated sludge increased relative to the activity aid the biomass level of the complete microbial community during a seasonal occurrence of filamentous foaming . Thus, Gordonia spp . may represent a numerically dominant but metabolically limited fraction of the total biomass, and the role of Gordonia spp . in filamentous foaming may be linked more tightly to the physical presence of filamentous microorganisms than to the metabolic activity of the cells.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2001, 36(7), 1361 - 71
Enhancement of dewaterability of thickened waste activated sludge by freezing and thawing treatment; Wang Q et al.; The effect of freezing speed on dewaterability of waste activated sludge thickened by flotation was investigated . The average dewatering rate of the sludge after freezing/thawing treatment was remarkably increased, and was found to be larger in the order: slow-frozen (-10 degrees C, -20 degrees C) > fast-frozen (-80 degrees C) > unfrozen sludge . This order was consistent with those of the sludge settling, elution of intracellular water and the numbers of the viable bacteria in the sludges after freezing/thawing . The expression characteristics and the final moisture contents of unfrozen and frozen sludge were evaluated from expession experiments at constant pressure . The wet-basis moisture content of final cake of frozen sludge was about 10% lower than those of unfrozen sludge, and even the cake obtained under additional 2 kgf/cm2 pressure may burn without auxiliary fuel . In addition, the mechanism responsible for the sludge dewatering was also examined.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2001, 36(7), 1349 - 60
Evaluation of a protease assay based on a natural protein for heavy metals inhibition of activated sludge; Garcia-Gonzalez J et al.; An enzymatic assay employing 2,4,6-trinitrobenzenesulfonic acid to follow the hydrolysis reaction of peptide bonds of a natural protein by activated sludge was evaluated for assessing the inhibition caused by heavy metals on biological treatment processes . The individual and joint effects up to 20 mg/l of Cu(II) and Zn(II) on activated sludge of different ages (6, 10 and 14 days) between a pH range from 6 to 7 was investigated by means of a 2(4) factorial experimental design . From statistical results, it has been concluded that not only the four main effects of these variables have an important influence on protease activity of activated sludge but also some interactions among them . Experimental data showed that Zn(II) was less inhibitory towards proteases than Cu(II) and that their joint effects acted neither synergistically or antagonistically . Sludge age was the variable that more strongly affected the protease activity of activated sludge.

Life Support Biosph Sci, 1998, 5(1), 53 - 61
Nutrient recovery and biodegradation of inedible tomato plant residues by activated sludge cultures and Phanerochaete chrysosporium; Christodoulatos C et al.; The biodegradation of inedible biomass and the recovery of nutrients from hydroponically grown tomato plant material were investigated under various growth conditions of activated sludge and the fungus Phanerochaete chrysosporium . The experiments were carried out in shaker flasks at three incubation temperatures (25 degrees C, 40 degrees C, and 60 degrees C for the activated sludge and 25 degrees C, 40 degrees C, and 50 degrees C for the fungi) with heat-pretreated samples at 150 degrees C for 30 min, and without pretreatment of the inedible residues . Under the experimental conditions tested, both cultures exhibited similar performance in terms of solids reduction and nutrient recovery . Solids reduction as high as 70% was obtained in both systems . Most of the solids degradation occurred the first 16 days of incubation . Cellulose degradation reached about 90% but no significant reduction in the solids lignin content was observed . Recovery of nitrogen (as NO2-N and NO3-N) and other micronutrients was sufficiently high and was accompanied by an average 70% reduction in COD, indicating that the final effluent is suitable for hydroponic plant growth . Incubation temperature had a minimal effect on solids degradation but appeared to influence the leachability of certain nutrients.

Adv Space Res, 1994 Nov, 14(11), 105 - 12
Lunar base CELSS design and analysis; Sirko RJ et al.; This paper describes the conceptual development of a hybrid biological-physical/chemical (P/C) life support system model for a lunar outpost . It presents steps that lead to loop closure and determines mass flow characteristics for an inedible biomass enzyme reactor and an activated sludge bioreactor . Computer modeling techniques were used to determine that the cellulose reactor has the design capabilities to provide significant increases in the plant harvest index . Activated sludge was found to fit design demands for a small, continuous-flow, steady-state system . Systems analysis and component sizing for these two bioreactors and information regarding supporting bioregenerative and physical/chemical components are presented.

Syst Appl Microbiol, 2001 Jul, 24(2), 238 - 44
DNA polynucleotide probes generated from representatives of the genus Acinetobacter and their application in fluorescence in situ hybridization of environmental samples; Zimmermann J et al.; The application of rRNA directed polynucleotide probes carrying multiple labels facilitates the detection of target cells by fluorescence in situ hybridizations and allows specific enrichment by cell fishing . So far, exclusively RNA transcript probes have been used . To reduce the effort in the preparation of the polynucleotides and to enhance their stability, DNA probes matching a part of the highly variable domain III on the 23S rRNA were constructed by amplification of the target region using PCR . Fluorescent labeling was achieved by incorporation of Cy3-labeled desoxyribonucleotides in the amplification . DNA polynucleotide probes were constructed for the seven validly described Acinetobacter species . Amplified domain III rDNA of A . baumannii and A . calcoaceticus could be readily applied as species specific probe . In addition, rDNA fragments could be used to recognize two groups of species, one comprising A . haemolyticus, A . junii and A . radioresistens and the other one A . lwoffii and A . johnsonii . Acinetobacter baumannii cells, some of them occurring in filaments, could be detected by in situ hybridization in native samples of activated sludge.

Chemosphere, 2001 Aug, 44(5), 1273 - 80
Estimation of biodegradation parameters of phenolic compounds on activated sludge by respirometry; Orupold K et al.; The bio-oxidation of phenol, catechol, resorcinol, m-cresol and 5-methylresorcinol on activated sludge was investigated by oxygen uptake measurements . In addition, the degradation of acetate with the same microbial population was studied . The substrate-dependent oxygen uptake data were analysed on the basis of the Michaelis-Menten kinetics . The extant kinetic parameters, the maximum rates of oxygen consumption and half-saturation constants for the processes with different substrates were determined . The simple respirometric approach also made it possible to determine the short-term oxygen demands of the substrates which formed 23-38% of the theoretical oxygen demand of the studied compounds.

Chemosphere, 2001 Sep, 44(6), 1447 - 54
Evaluation of TCDD biodegradability under different redox conditions; Kao CM et al.; Polychlorinated dibenzo-p-dioxins have been generated as unwanted by-products in many industrial processes . Although their widespread distribution in different environmental compartments has been recognized, little is known about their fate in the ultimate environment sinks . The highly stable dioxin isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been called the most toxic compound known to man . In this laboratory microcosm study, TCDD bioavailability was evaluated under five reduction/oxidation (redox) conditions including aerobic biodegradation, aerobic cometabolism, methanogenesis, iron reduction, and reductive dechlorination . Activated sludge and aquifer sediments from a TCDD and a pentachlorophenol (PCP) contaminated site were used as the inocula . Acetate, sludge cake, and cane molasses were used as the primary substrates (carbon sources) in cometabolism and reductive dechlorination microcosms . After a 90-day incubation period, microcosms constructed under reductive dechlorination conditions were the only treatment showing promising remediation results . The highest TCDD degradation rate {up to 86% of TCDD removal (with an initial concentration of 96 microg/kg of soil)} was observed in the microcosms with anaerobic activated sludge as the microbial inocula and sludge cakes as the primary substrates . Except for reductive dechlorination microcosms, no significant TCDD removal was observed in the microcosms prepared under other conditions . Thus, application of an effective primary substrate to enhance the reductive dechlorination process is a feasible method for TCDD bioremediation . Bioremediation expense can be significantly reduced by the supplement of some less expensive alternative substrates (e.g., sludge cakes, cane molasses) . Results would be useful in designing a scale-up in situ or on-site bioremediation system such as bioslurry reactor for field application.

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