Activated sludge

Indian J Exp Biol, 2001 May, 39(5), 490 - 2
Isolation, screening and identification of bacterial strains for degradation of predigested distillery wastewater; Jain N et al.; Three bacterial isolates from the activated sludge of a distillery wastewater treatment plant identified as Xanthomonas fragariae, Bacillus megaterium and Bacillus cereus were found to remove COD and colour from anaerobically digested distillery wastewater in the range of 55 to 68% and 38 to 58% respectively.

Huan Jing Ke Xue, 2001 May, 22(3), 20 - 4
{A comparison between a submerged membrane bioreactor and a conventional activated sludge process}; Rui L et al.; A comparison between a submerged membrane bioreactor (MBR) and a conventional activated sludge process (CAS) was carried out under similar operational conditions . MBR demonstrated a more stable and excellent effluent quality than CAS . Its effluent COD concentration was 55.5 mg/L on average, much lower than that of CAS (79.7 mg/L) . Soluble microbial products accumulated in the MBR during the first 120 days in operation due to membrane interception of macromolecules, but these accumulated substances were degraded at last with microbial acclimation . No similar phenomenon was observed in the CAS system . Compositions of the CAS effluent, MBR supernatant and membrane permeate were found quite different . In the CAS effluent and MBR supernatant, both macromolecules with MW > 60,000 and small molecules with MW < 3,000 were dominant and macromolecules had a much larger occupation in the MBR supernatant . In the membrane permeate, however, small molecules with MW < 3,000 were the major component . The relatively small floc size in the MBR was proved favorable to improve oxygen transfer rate.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2001, 36(6), 987 - 98
Biosorption of heavy metals from landfill leachate onto activated sludge; Cecen F et al.; The removal of various heavy metals was studied when activated sludge was exposed to heavy metals in landfill leachate . Batch uptake tests were conducted for this purpose . Adsorption was the main mechanism of removal when biomass was contacted with heavy metals . Activated sludge had a high biosorption capacity and equilibrium was reached in a short time with respect to copper, iron, manganese, zinc and chromium . Adsorption isotherms were generated for those heavy metals and the Freundlich constants were calculated . Among the metals studied, manganese became very concentrated on activated sludge with time.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2001, 36(6), 883 - 95
Biodegradation potential of photocatalyzed surfactant washwater; Maillacheruvu K et al.; Enhanced release of hydrophobic compounds from a soil matrix can be achieved by use of soil-washing or soil-flushing using various surfactants . However, the surfactants used in achieving the desorption of organic contaminants may also cause a problem in subsequent removal/disposal of these contaminants . UV radiation in the presence of TiO2 as a pre-treatment step to achieve initial (or partial) breakdown of naphthalene and Sodium Dodecyl Sulfate (SDS) using batch experiments indicated that 56% to 88% naphthalene degradation occurred within 30 minutes to one hour . Preliminary results on the estimate of the batch aerobic biodegradation potential of photocatalyzed washwater containing naphthalene and SDS suggested that SDS was the major carbon and energy source for an activated sludge enrichment culture and an enrichment culture obtained from microorganisms at a contaminated site . Continuous-flow stirred tank reactors (CSTRs) with with a solids retention time (SRT) of 4 days were not effective, but an SRT of 8 days was successful in biodegrading the naphthalene and surfactant . These results indicated that photocatalytic treatment as a pre-treatment step followed by a biodegradation step may offer potential in cleaning up surfactant washwaters containing organic contaminants.

J Biotechnol, 2001 Aug 23, 89(2-3), 175 - 84
Biodegradation, decolourisation and detoxification of textile wastewater enhanced by advanced oxidation processes; Ledakowicz S et al.; Recently, an increasing application of so called advanced oxidation processes (AOPs) to industrial wastewater has been observed . In particular, an integrated approach of biological and chemical treatment of wastewater is advantageous conceptually . The subject of our study was synthetic wastewater, simulating effluents from knitting industry . The wastewater contained components that are very often used in Polish textile industry: an anionic detergent Awiwaz KG conc., a softening agent Tetrapol CLB and an anthraquinone dyestuff-Acid Blue 40, CI 2125 . The toxicity of the detergents and the dye was determined in terms of effective concentration EC50 using mixed cultures of activated sludge as well as pure culture of luminescent bacteria Vibrio fischerii NRRLB-11177 . The dye did not undergo biodegradation without AOPs pretreatment, therefore a degree of its removal (decolourisation) by the AOPs has been determined and its bio-sorption properties on the flocks of activated sludge have been studied . The dye adsorption onto flocks of activated sludge was described by Henry's isotherm . Our investigations focussed on the influence of various oxidants like O3, H2O2 and UV light on biodegradation of single components aqueous solution as well as of the whole textile wastewater . The results of kinetic measurements of the biodegradation (by means of acclimated activated sludge) was described by Monod type of kinetic equation . The experimental evidence of the positive effect of chemical oxidation pretreatment on the biodegradation of recalcitrant compounds was quantified by estimation of the kinetic parameters of the Monod equation . Due to the AOPs pretreatment a decrease of the Monod constant and an increase of maximal specific growth rate was observed . The activity of degradative enzymes of activated sludge was assayed by the methods of 2-{4-iodophenyl}-3-{4-nitrophenyl}-5-phenyltetrazolium chloride test.

Water Sci Technol, 2001, 44(1), 87 - 94
Data-based modelling and proportional-integral-plus (pip) control of nitrate in an activated sludge benchmark; Ghavipanjeh F et al.; This paper presents the result of an investigation into the Proportional Integral Plus (PIP) control of nitrate in the second zone of an activated sludge benchmark . A data-based reduced order model is used as the control model and identified using the Simplified Refined Instrumental Variable (SRIV) identification and estimation algorithm . The PIP control design is based on the Non Minimum State Space (NMSS) form and State Variable Feedback (SVF) methodology . The PIP controller is tested against dynamic load disturbances and compared with the response of a well tuned PI controller.

Water Sci Technol, 2001, 44(1), 137 - 44
Comparison of different operational modes of a two-stage activated sludge pilot plant for the extension of the Vienna STP; Muller-Rechberger H et al.; A pilot plant has been operated over a period of two years in order to investigate the performance and the operating characteristics of the plant concept developed for the extension of the main Vienna STP and to develop a simulation model which will be applied for operation support of the full stage plant . The pilot plant is a two stage activated sludge plant, each stage comprising of four aeration tanks and a clarifier tank . The pilot plant layout allows three different operational modes, each of which has been operated for several periods . The performance of the pilot plant during these periods is described and the different operational modes are compared to each other.

Chemosphere, 2001 Aug, 44(4), 865 - 72
Primary biodegradation of veterinary antibiotics in aerobic and anaerobic surface water simulation systems; Ingerslev F et al.; The primary aerobic and anaerobic biodegradability at intermediate concentrations (50-5000 microg/l) of the antibiotics olaquindox (OLA), metronidazole (MET), tylosin (TYL) and oxytetracycline (OTC) was studied in a simple shake flask system simulating the conditions in surface waters . The purpose of the study was to provide rate data for primary biodegradation in the scenario where antibiotics pollute surface waters as a result of run-off from arable land . The source of antibiotics may be application of manure as fertilizer or excreta of grazing animals . Assuming first-order degradation kinetics, ranges of half-lives for aerobic degradation of the four antibiotics studied were 4-8 days (OLA), 9.5-40 days (TYL), 14-104 days (MET) and 42-46 days (OTC) . OLA and OTC were degraded with no initial lag phase whereas lag phases from 2 to 34 days (MET) and 31 to 40 days (TYL) were observed for other substances . The biodegradation behaviour was influenced by neither the concentrations of antibiotics nor the time of the year and location for sampling of surface water . Addition of 1 g/l of sediment or 3 mg/l of activated sludge from wastewater treatment increased the biodegradation potential which is believed to be the result of increased bacterial concentration in the test solution . Biodegradation was significantly slower in tests conducted in absence of oxygen . Assessments of the toxic properties of antibiotics by studying the influence on the biodegradation rates of 14C-aniline at different concentrations of antibiotics showed that no tests were conducted at toxic concentrations.

Chemosphere, 2001 Aug, 44(4), 823 - 6
Biodegradability of ethylenediamine-based complexing agents and related compounds; Pitter P et al.; The biological degradability (Zahn-Wellens test) of ethylenediamine derivatives with carboxymethyl and 2-hydroxyethyl groups was investigated . Mixed bacterial culture (activated sludge) was used as inoculum (non-adapted sludge and sludge adapted at different mean biomass retention time, the so-called sludge age) . Biodegradability of ethylene(propylene)di(tri)amine-based complexing agents depends on the character and number of substituents and nitrogen atoms in the molecule . Tetra(penta)substituted derivatives with two or more tertiary nitrogen atoms and carboxymethyl or 2-hydroxyethyl groups in the molecule (EDTA, DTPA, PDTA, HEDTA) are very stable from an environmental point of view . On the contrary, disubstituted derivatives with two secondary nitrogen atoms in the molecule (e.g., EDDA) are potentially degradable.

Chemosphere, 2001 Aug, 44(4), 721 - 8
Degradability of selected azo dye metabolites in activated sludge systems; Ekici P et al.; The stability of eight environmentally relevant azo dye metabolites {o-aminotoluene (2), 4,4'-thiodianiline (4), 4,4'-diaminodiphenylmethane (6), p-chloroaniline (7), 2,4-toluylenediamine (9), p-kresidine (14), 2,4-diaminoanisole (15), and 2-naphthylamine (18)} was investigated in activated sludge systems and compared to their hydrolysis stability . For both studies, test systems of the EC and EPA were used . The results show that degradation under aerobic conditions proceeds via oxidation of the substituents located on the aromatic ring or on the side chain . Under anaerobic conditions, the azo bond is reductively cleaved, which leads to the substituted amines . These are toxic and potentially hazardous to the environment.

J Environ Biol, 2001 Jan, 22(1), 23 - 7
Microbial decolourisation of pulp and paper mill effluent in presence of nitrogen and phosphorus by activated sludge process; Chandra R; The effect of pH, nutrient and aeration was studied on the removal of colour and reduction of BOD, COD and heavy metals with addition of readily available source of nitrogen and phosphorus in concentration of 1.0 g/L . Recalcitrant compound was effectively degraded by active microbial consortia . The isolated bacteria were identified as Pseudomonas putida (S1), Citrobacter sp . (S4) and Enterobacter sp . (S5) . These organisms not only decolourised effluent upto 97% but reduced BOD, COD, phenolics and sulfide upto 96.63, 96.80, 96.92 and 96.67% respectively within 24 hrs of aeration and the heavy metals were removed upto 82-99.80% . The TSS and TDS were sharply reduced due to degradation . The absorption maxima was also decreased to 90% . However, in control without the microbial consortium no noticeable change was produced.

J Appl Microbiol, 2001 Aug, 91(2), 299 - 305
Synthesis of intracellular storage polymers by Amaricoccus kaplicensis, a tetrad forming bacterium present in activated sludge; Falvo A et al.; AIMS: The study investigated the physiology of Amaricoccus kaplicensis to determine whether it could outcompete polyphosphate accumulating bacteria in activated sludge systems removing phosphorus, by preferentially assimilating substrates in the anaerobic stages of these processes . METHODS AND RESULTS: The storage processes were investigated under anaerobic, anoxic and aerobic conditions in both batch and periodically fed cultures in an aerobic sequencing batch reactor (SBR) . Amaricoccus kaplicensis showed a high capacity for storing aerobically large amounts of acetate as poly beta-hydroxybutyrate (PHB) at high rates . However, no acetate assimilation under anaerobic conditions and very slow assimilation under anoxic conditions could be detected . CONCLUSION: Amaricoccus kaplicensis in pure culture does not behave as polyphosphate accumulating bacteria competitor; therefore it is difficult to understand why anaerobic/aerobic systems often contain such large numbers of Amaricoccus cells . SIGNIFICANCE AND IMPACT OF THE STUDY: Amaricoccus kaplicensis is probably not responsible for the failure of activated sludge systems removing phosphorus, and other organisms capable of anaerobic substrate assimilation should be sought.

Water Sci Technol, 2001, 43(12), 183 - 6
Occurrence of Cryptosporidium in Japan and counter-measures in wastewater treatment plants; Suwa M et al.; The outbreak of cryptosporidiosis in Ogose in 1996 forced the wastewater treatment authorities to rethink the level of contamination by Cryptosporidium of wastewater and waters in the watersheds and counter-measures in wastewater treatment plants . A survey of Cryptosporidium concentrations in wastewater and treated wastewater conducted nationwide showed relatively low levels . Also, evaluation of wastewater treatment showed a 2 log oocyst removal with an activated sludge process and an additional 1 log removal with coagulant dosing.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2001 May, 36(5), 819 - 31
Domestic wastewater treatment using immobilized sludge fluidized-bed reactors; An M et al.; Bench-scale fluidized-bed reactors using the immobilized activated sludge process were studied for the treatment of domestic wastewater . Different intermittent aeration patterns were investigated in order to improve the total nitrogen (TN) removal . The best TN removal at 74.4% was achieved at an HRT of 6 hours (with corresponding BOD loading rate of 0.766 kg/m3/d) and an aeration-pattern of 1,3 (the hours of aeration and non-aeration time cycle) . The removal efficiencies for organic carbon, NH4(+)-N, TKN and TSS were not affected and remained at more than 90% . Simultaneous organic carbon and nitrogen removal was accomplished in a single immobilized sludge reactor . The impact of various influent feed patterns on the treatment was examined . The continuous feed pattern was recommended as it ensured good TN removal without any adverse impacts on the removal of organic carbon, NH4(+)-N, TKN and TSS . The immobilized sludge beads exhibited satisfactory mechanical stability without apparent breakage over the 180-day experiment period.

Water Res, 2001 Aug, 35(11), 2702 - 10
Nutrient addition to enhance biological treatment of greywater; Jefferson B et al.; This study compares the chemical oxygen demand (COD) removal and respiration rates of a microbial population treating real and synthetic greywaters dosed with nutrient supplements . The nutrient composition of the real and synthetic greywaters was analysed and the dosing regime for nitrogen, phosphorus and a range of trace metals planned accordingly . The doses consisted of eight single additives (macronutrients and trace metals) to the control greywater and six trace metal additions to C: N : P balanced greywater . The COD removal for the control real and synthetic greywater in lab-scale activated sludge systems (0.038 and 0.286 kg COD kg MLSS(-1) d(-1), respectively) confirmed nutrient limitation and the poor degree of greywater treatment . Nutrient dosing increased the COD removal rate and oxygen uptake rate in many cases . The greatest stimulation of microbial activity was observed with zinc additions to C: N: P balanced real greywater (1.291 kg COD kg MLSS(-1) d(-1) over 30 times the control) . Inhibitory effects to various extents were rare and limited mainly to the additions of metals to synthetic greywater . The dominance of chemicals effects was observed on addition of some micronutrients; notably iron and aluminium, metals on which many coagulants for use in biotreatment of other wastewaters are based . The data indicate that the impact of understanding microbial processes and the nutrients required for wastewater treatment can only serve to optimise process efficiency for the proposed treatment of greywater.

Water Res, 2001 Aug, 35(11), 2693 - 701
Simultaneous storage and degradation of PHB and glycogen in activated sludge cultures; Carta F et al.; Bacteria in activated sludge are subjected to periods of substrate availability and absence of external substrates . The response of bacteria to such dynamic conditions was studied in a 2 L sequencing batch reactor (SBR) by subjecting a mixed microbial population to successive periods of external substrate availability (feast period) and no external substrate availability (famine period) . In previous studies, acetate or glucose was used as single substrate leading to the storage of polyhydroxybutyrate or glycogen, respectively . In this study, a mixture of acetate and glucose was used . It appeared that both substrates were consumed simultaneously . The relative contribution of growth and storage processes was in these experiments similar as in the systems fed with a single substrate only . The ratio of substrate uptake over substrate storage was 0.6 Cmol/Cmol for both substrates . The uptake rate of acetate was not influenced by the simultaneous uptake of glucose . The degradation kinetics and rates of the storage compounds were the same as for the systems in which only one compound was stored in the activated sludge . The global performance of the culture grown on mixed substrates could therefore be described as the sum of the conversions observed in cultures fed with the individual substrates.

Water Res, 2001 Aug, 35(11), 2661 - 8
The storage of acetate under anoxic conditions; Dionisi D et al.; Till now the role of storage in activated sludge processes under transient conditions has been deeply investigated under anaerobic (EBPR processes) or aerobic (bulking control) environments . Little attention has been given to the role of storage in processes including anoxic environments . Hence, the aim of the present work was to investigate the anoxic storage along with other substrate removal mechanisms under transient conditions . Several mixed culture were ad hoc selected under anoxic environment and periodic feeding (acetate as carbon source) at different organic load rate (OLR) and feed length; then their transient response to substrate spike was investigated by batch tests under both anoxic and aerobic conditions . The relative role of different mechanisms in the substrate removal was established on the basis of COD balance assuming that the acetate COD removed from the liquid phase could be oxidised for energy needs or recovered into solids as poly-3-hydroxybutyric acid (PHB) (storage), other internal precursors or intermediates (accumulation) and active biomass (growth, as estimated by ammonium uptake) . In all tested conditions, growth response was very little while PHB storage was prevailing . In some operating conditions, indirect evidence of accumulation (in forms still to be identified) was also found . The transient response was not affected by the presence of free amino acids, at least for the unacclimated mixed culture under observation . Transient response under aerobic condition was quite similar to the anoxic one.

Water Res, 2001 Aug, 35(11), 2615 - 20
Effect of acid and surfactant treatment on activated sludge dewatering and settling; Chen Y et al.; The effect of pretreating activated sludge with sulfuric acid and surfactant on its exocellular polymer(ECP), dewaterability and settleability was investigated . It was observed that the centrifugal dewatering efficiency was increased with the decrease of sludge pH value, and which was further improved if the surfactant was simultaneously applied . However, to the filtration dewatering, the water content reached the minimum in the case of pH 2.5, and the additional use of surfactant was also favorable . The water content of sludge dewatered with filtration reached 73.99% when a pH 2.5 and a 0.1 g surfactant were employed, which was reduced by around 2% as compared with surfactant unused . Experimental results indicated that the sludge sedimentation rate was significantly accelerated under pH 2.5 condition, and which was increased once more by the utilization of surfactant . Further studies revealed that treating activated sludge with sulfuric acid at pH 2.5 or combined with surfactant was an effective method to remove the polymers from sludge surface and induced the decrease of ECP, which resulted in the improvement of dewaterability and settleability . This study suggested the potentiality of improving activated sludge mechanical dewaterability by the use of sulfuric acid to control its pH at 2.5 or together with a surfactant.

Water Sci Technol, 2001, 43(11), 75 - 82
Activated sludge flocculation: direct determination of the effect of calcium ions; Biggs CA et al.; The effect of calcium on activated sludge flocculation dynamics is investigated using a unique experimental technique . The technique allows on-line analysis of the size of activated sludge flocs during flocculation and provides valuable insight into the mechanisms of flocculation . Activated sludge samples were firstly sonicated for 3 minutes at 50 W and then stirred at 100 rpm . The floc size was subsequently measured on-line using a Malvern Mastersizer/E . For concentrations of calcium less than 4 meq/L no significant increase in final floc size was observed even though an increase in the initial rate of change of floc size could be seen . Addition of calcium greater than 4 meq/L resulted in a dramatic increase in floc size . Results from this investigation support the theory that cations are involved in flocculation through cationic bridging, and will be used in ongoing investigations to model the flocculation process.

Water Sci Technol, 2001, 43(11), 51 - 8
Aerobic treatment of inhibitory wastewater using a high-pressure bioreactor with membrane separation; Male PC et al.; Wastewater high in phenolic content (948 mg/l) and dissolved solids (5.4 g/l) had to be treated to remove most of the organic material and toxic compounds . A laboratory scale High Pressure (3 bar) Bioreactor (HPB) was developed and operated to treat the wastewater using a ceramic ultra filtration membrane as biomass separator . The performance of the system was compared to a normal activated sludge plant (ASP) using sludge settling for separation . The HPB was more stable than the ASP, which twice became unstable with a resulting biomass loss . Both reactors removed 90% of the chemical oxygen demand (COD) loading, reducing the phenol concentration below 20 mg/l . The maximum COD removal rate of the HPB was 28 kg/m3.d compared to 15 kg/m3.d of the ASP, while the HPB achieved 16-32 times better oxygen transfer than the ASP . It was concluded that the HPB was the preferred treatment system compared to the ASP, when treating high strength inhibitory wastewaters, due to its stable operating performance and high COD removal rate.

Water Sci Technol, 2001, 43(11), 323 - 8
Performance evaluation of a UASB--activated sludge system treating municipal wastewater; von Sperling M et al.; Recent research has indicated the advantages of combining anaerobic and aerobic processes for the treatment of municipal wastewater, especially for warm-climate countries . Although this configuration is seen as an economical alternative, is has not been investigated in sufficient detail on a worldwide basis . This work presents the results of the monitoring of a pilot-scale plant comprising of an UASB reactor followed by an activated sludge system, treating actual municipal wastewater from a large city in Brazil . The plant was intensively monitored and operated for 261 days, divided into five different phases, working with constant and variable inflows . The plant showed good COD removal, with efficiencies ranging from 69% to 84% for the UASB reactor, from 43% to 58% for the activated sludge system only and from 85% to 93% for the overall system . The final effluent suspended solids concentration was very low, with averages ranging from 13 to 18 mg/l in the typical phases of the research . Based on the very good overall performance of the system, it is believed that it is a better alternative for warm-climate countries than the conventional activated sludge system, especially considering the total low hydraulic detention time (4.0 h UASB; 2.8 h aerobic reactor; 1.1 h final clarifier), the savings in energy consumption, the absence of primary sludge and the possibility of thickening and digesting the aerobic excess sludge in the UASB reactor itself.

Water Sci Technol, 2001, 43(11), 145 - 52
Transfer number in fine bubble diffused aeration systems; Capela S et al.; On the basis of full-scale data from 58 clean water tests performed in 26 activated sludge tanks equipped with fine bubble diffusers and of a theoretical approach, it can be stated that fine bubble aeration systems with total floor coverage arrangement provide higher kLa values and the lowest spiral liquid circulation . An efficiency criterion for oxygen transfer (NT) was defined on the basis of the dimensional analysis . The transfer number NT allows us to take account of the impact of vertical liquid circulation movements on oxygen transfer . The values of NT calculated from the results of full scale nonsteady-state clean water tests vary from 5.3 x 10(-5) to 9.1 x 10(-5) and are directly dependent upon the arrangement of air diffusers . It has been shown that the highest transfer numbers corresponded to the total floor coverage arrangement and the average calculated NT values is 7.7 x 10(-5), independently of the diffuser density and of the gas velocity, over the ranges studied . The lowest transfer numbers are obtained when the diffusers are located in separate grids, and the transfer number is reduced with increasing air flow rate.

Lett Appl Microbiol, 2001 Jul, 33(1), 17 - 20
A microwave-based method for nucleic acid isolation from environmental samples; Orsini M et al.; AIMS: A simple and rapid method was described for DNA isolation directly from activated sludge or other environmental sources, including soil and sediments . METHODS AND RESULTS: The present method is based on microwave thermal shock and provides DNA suitable for further analysis . It is also effective for RNA extraction . CONCLUSION: The protocol is effective, easy, fast and does not require the use of expensive equipment or reagents . SIGNIFICANCE AND IMPACT OF THE STUDY: The described method can be applied to difficult substrates in environmental microbiology studies.

J Appl Microbiol, 2001 Jul, 91(1), 168 - 75
Microscopic observation of aerobic granulation in sequential aerobic sludge blanket reactor; Tay JH et al.; AIMS: This paper attempts to provide visual evidence of how aerobic granulation evolves in sequential aerobic sludge blanket reactors . METHODS AND RESULTS: A series of experiments were conducted in two column-type sequential aerobic sludge reactors fed with glucose and acetate as sole carbon source, respectively . The evolution of aerobic granulation was monitored using image analysis and optical and scanning electron microscopy . The results indicated that the formation of aerobic granules was a gradual process from seed sludge to compact aggregates, further to granular sludge and finally to mature granules with the sequential operation proceeding . Glucose- and acetate-fed granules have comparable characteristics in terms of settling velocity, size, shape, biomass density and microbial activity . However, the microbial diversity of the granules was associated with the carbon source supplied . In this work, an important aerobic starvation phase was identified during sequential operation cycles . It was found that periodical aerobic starvation was an effective trigger for microbial aggregation in the reactor and further strengthened cell-cell interaction to form dense aggregates, which was an essential step of granulation . The periodical starvation-induced aggregates would finally be shaped to granules by hydrodynamic shear and flow . CONCLUSION: Aerobic granules can be formed within 3 weeks in the systems . The periodical starvation and hydrodynamic conditions would play a crucial role in the granulation process . SIGNIFICANCE AND IMPACT OF THE STUDY: Aerobic granules have excellent physical characteristics as compared with conventional activated sludge flocs . This research could be helpful for the development of an aerobic granule-based novel type of reactor for handling high strength organic wastewater.

Ecotoxicol Environ Saf, 2001 Jul, 49(3), 275 - 80
Toxicity of organotin compounds to activated sludge; Stasinakis AS et al.; Inhibition of respiration rate of activated sludge heterotrophic microorganisms was determined for tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), and triphenyltin (TPhT) . TBT, DBT, and TPhT exhibit similar acute toxicity to activated sludge, while MBT is less toxic . The effect of various experimental parameters, such as sludge age, concentrations of suspended solids, and exposure time, on toxicity was investigated . An increase in sludge age or in the concentration of suspended solids reduces the observed inibition . Longer exposure seems to increase the inhibition of TBT, DBT, and TPhT during the first hours of exposure, while later the inhibition remains constant . In the case of MBT, 24 h after exposure, the respiration rate was similar to that of the control biomass .

Water Sci Technol, 2001, 43(10), 203 - 9
Feasibility of the membrane bioreactor process for water reclamation; Adham S et al.; The feasibility of the membrane bioreactor (MBR) process for water reclamation was studied . Process evaluation was based on the following: literature review of MBRs, worldwide survey of MBRs, and preliminary costs estimates . The literature review and the survey have shown that the MBR process offers several benefits over the conventional activated sludge process, including: smaller space and reactor requirements, better effluent water quality, disinfection, increased volumetric loading, and less sludge production . The MBR process can exist in two different configurations, one with the low-pressure membrane modules replacing the clarifier downstream the bioreactor (in series), and the second with the membranes submerged within the bioreactor . Four major companies are currently marketing MBRs while many other companies are also in the process of developing new MBRs . The MBR process operates in a considerably different range of parameters than the conventional activated sludge process . The preliminary cost evaluation has shown that the MBR process is cost competitive with other conventional wastewater treatment processes.

Environ Toxicol Chem, 2001 Jul, 20(7), 1517 - 27
Reproductive, biochemical, physiological, and population responses in perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) downstream of two elemental chlorine-free pulp and paper mills; Karels A et al.; Perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) populations in a state of late vitellogenesis were studied downstream of two pulp and paper mills and at upstream references in southern Lake Saimaa, Finland . The mills used elemental chlorine-free bleaching and activated sludge effluent treatment technologies . The exposure of fish to pulp mill effluents, as measured by concentrations of chlorophenolics in the bile and liver ethoxyresorufin-O-deethylase (EROD) activity, was low and almost similar to the references . Nevertheless, bile resin acid concentrations in exposed perch and roach (260-320 micrograms/ml) and bile beta-sitosterol concentrations in exposed roach (1.5-3.5 micrograms/ml) were, respectively, 10 to 30 times and 2 to 5 times higher compared with the references . Reproductive parameters like plasma 17 beta-estradiol and testosterone levels were lower in exposed male and female perch but the same in roach . Vitellogenin concentrations in plasma and liver cytosol of roach were similar . Gonad weight and fecundity were lower in exposed female perch but similar in roach . The relative liver weight was higher in exposed roach but not in perch . The body condition and immunologic parameters in fish were the same . The growth and age at maturity of exposed perch and roach were similar to the references . The size and age distribution of perch in the recipient of one of the mills was shifted toward smaller and younger fish . Our results show that several reproductive variables were altered in late vitellogenic perch in the vicinity of the mills, but they were not altered in roach.

Huan Jing Ke Xue, 2001 Mar, 22(2), 41 - 5
{Biodegradation behavior of ethylenediaminetetraethylene acid}; Yang X et al.; Aerobic and anaerobic degradability of ethylenediaminetetraethylene acid(EDTA) were measured on Warburg respirometer and anaerobic batch reactors . Biodegradation of EDTA as a single substance was poor, but biodegradation of EDTA with co-substrate could be improved . The wastewater containing EDTA can be treated by activated sludge process . The EDTA removal efficiency was 80% under the circumstance HRT 16 h and EDTA removal efficiency reached to 92.5%-95.1% when HRT was 20 h . The main factor affecting the biodegradability of EDTA is sludge remained time.

Environ Technol, 2001 May, 22(5), 497 - 507
Evaluation of Activated Sludge Model No . 2 at high phosphorus concentrations; Seco A et al.; This paper presents laboratory scale experimentation carried out to study enhanced biological phosphorus removal at high phosphorus concentrations in a sequencing batch reactor . Four series of data obtained in a sequencing batch reactor are examined in light of the Activated Sludge Model No . 2 . This model was calibrated using data from the first and second series working at low phosphorus concentrations . The Activated Sludge Model No . 2 successfully characterised the enhanced biological phosphorus removal performance of the sequencing batch reactor at low phosphorus concentrations . The calibrated model was then used to adjust experimental results of the other series working at high phosphorus concentration . Differences between model predictions and experimental data could be explained by redissolution in the anaerobic phase and precipitation in the aerobic phase of calcium phosphates not taken into account by the model . This hypothesis can be justified by the conditions of pH and phosphorus concentration prevailing in the experiments and it was confirmed by the results of another experiment in which precipitated phosphorus profile was measured during the cycle.

J Ind Microbiol Biotechnol, 1999 Oct, 23(4-5), 374 - 379
Lessons learned from Sphingomonas species that degrade abietane triterpenoids; Mohn WW et al.; Abietane terpenoid-degrading organisms include Sphingomonas spp which inhabit natural environments and biological treatment systems . An isolate from the high Arctic indicates that these organisms occur far from trees which synthesize abietanes and suggests that some of these organisms can occupy a niche in hydrocarbon-degrading soil communities . Abietane-degrading Sphingomonas spp provide additional evidence that the phylogeny of this genus is independent of the catabolic capabilities of its members . Studies of Sphingomonas sp DhA-33 demonstrate that biological treatment systems for pulp mill effluents have the potential to mineralize abietane resin acids . On the other hand, these studies indicate that some chlorinated dehydroabietic acids are quite recalcitrant . Strain DhA-33 grows relatively well on some chlorinated dehydroabietic acids but transforms others to stable metabolites . Using strain DhA-33, a novel method was developed to measure the metabolic activity of an individual population within a complex microbial community . Oligonucleotide hybridization probes were used to assay the 16S rRNA:rDNA ratio of DhA-33 as it grew in an activated sludge community . However, this method proved not to be sufficiently sensitive to measure naturally occurring resin acid-degrading populations . We propose that the same approach can be modified to use more sensitive assays.

J Ind Microbiol Biotechnol, 1999 Oct, 23(4-5), 261 - 267
Detection of sphingomonads and in situ identification in activated sludge using 16S rRNA-targeted oligonucleotide probes; Neef A et al.; The increasing significance of members of the genus Sphingomonas in biotechnological applications has led to an increased interest in the diversity, abundance and ecophysiological potential of this group of Gram-negative bacteria . This general focus provides a challenge to improve means for identification of sphingomonads; eg molecular genetic methods for rapid and specific detection could facilitate screening of new isolates . Here, fluorescently labeled oligonucleotide probes targeted against 16S rRNA were used to typify strains previously assigned to the genus . All 46 sphingomonads tested including type strains of 21 Sphingomonasspecies could be detected with a probe originally designed for the genus and all but one with a probe designed for the alpha-4 subgroup of the Proteobacteria . The two probes are suitable for direct detection of sphingomonads in pure and mixed cultures as well as in environmental samples of unknown composition . The probes were used to identify sphingomonads in situ in activated sludge samples . Sphingomonads were rather abundant accounting for about 5-10% of the total cells in municipal sludges . Distinct patterns in aggregation of the cells suggest that these organisms could be involved in the formation process of sludge flocs.

Chemosphere, 2001 Jul, 44(1), 37 - 43
Efficiency of biological treatment affected by high strength of ammonium-nitrogen in leachate and chemical precipitation of ammonium-nitrogen as pretreatment; Li XZ et al.; Leachate samples with a high strength of ammonium-nitrogen (NH4+-N) were collected from a local landfill site in Hong Kong . Two experiments were carried out to study (1) the inhibition of microbial activity of activated sludge by NH4+-N and (2) the chemical precipitation of NH4+-N from leachate as a preliminary treatment prior to the activated sludge process . The experimental results demonstrated that the efficiency of COD removal decreased from 97.7% to 78.1%, and the dehydrogenase activity of activated sludge decreased from 9.29 to 4.93 microg TF/mg MLSS, respectively, when the NH4+-N concentration increased from 53 to 800 mg/l . The experiment also demonstrated that the NH4+-N in the leachate can be quickly precipitated as MgNH4PO4 x 6H2O after addition of MgCl2 x 6H2O + Na2HPO4 x 12H2O . The NH4+-N concentration was reduced from 5618 to 112 mg/l within 15 min when a molar ratio of Mg2+:NH+:PO4(3-) = 1:1:1 was used . The optimum pH to reach the minimum solubility of MgNH4PO4 x 6H2O was found to be in the range of 8.5-9.0 . Attention should be given to the high salinity formed in the treated leachate by using MgCl2 x 6H2O + Na2HPO4 x 12H2O, which may affect microbial activity in the following biological treatment processes . Using two other combinations of chemicals {MgO + 85%H3PO4 and Ca(H2PO4)2 x H2O + MgSO4 x 7H2O} could minimise salinity generation after precipitation, while they were less efficient for NH4+-N removal.

Appl Microbiol Biotechnol, 2001 May, 55(5), 609 - 18
Insights into the genetic diversity of initial dioxygenases from PAH-degrading bacteria; Moser R et al.; Alpha subunit genes of initial polyaromatic hydrocarbon (PAH) dioxygenases were used as targets for the PCR detection of PAH-degrading strains of the genera Pseudomonas, Comamonas and Rhodococcus which were obtained from activated sludge or soil samples . Sequence analysis of PCR products from several Pseudomonas strains showed that alpha subunits (nahAc allele) of this genus are highly conserved . PCR primers for the specific detection of alpha subunit genes of initial PAH dioxygenases from Pseudomonas strains were not suitable for detecting the corresponding genes from the genera Comamonas and Rhodococcus . Southern analysis using a heterologous gene probe derived from the P . putida OUS82 PAH dioxygenase alpha subunit identified segments of the PAH-degradation gene cluster from C . testosteroni strain H . Parts of this gene cluster containing three subunits of the initial PAH dioxygenase were isolated . These three subunits {ferredoxin (pahAb), alpha (pahAc) and beta (pahAd) subunit} were amplified by PCR as one fragment and expressed in Escherichia coli DH5alpha, resulting in an active initial dioxygenase with the ability to transform indole and phenanthrene . The DNA sequence alignment of alpha subunits from C . testosteroni H and various PAH-degrading bacteria permitted the design of new primers and oligonucleotide probes which are useful for the detection of the initial PAH dioxygenases from strains of Pseudomonas, Comamonas and Rhodococcus.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2001, 36(4), 447 - 63
Toxicity and biodegradation of products from polyester hydrolysis; Kim MN et al.; Toxicity of products from polyester hydrolysis such as succinic acid (SA), adipic acid (AA), mandelic acid (MA), terephthalic acid (TA), 1,4-butanediol (1,4-B), ethylene glycol (EG), styrene glycol (SG) and 1,4-cyclohexane dimethanol (1,4-C) was evaluated by phytotoxicity test on germination of young radish seeds and by cytotoxicity test on HeLa cells . The phytotoxicity test revealed SG > MA > 1,4-C > AA approximately SA > TA approximately EG > 1,4-B in order of decreasing toxicity taking into consideration the growth behavior after germination as well as the percentage of germination . Toxicity on HeLa cells decreased in slightly different order compared to that on young radish seeds, i.e . SG > 1,4-C > MA > TA > SA > AA > EG > 1,4-B . Tests for the phytotoxicity and for cytotoxicity indicated that the aromatic compounds were more harmful than the aliphatic ones . Each group of 4 strains which grew most rapidly on each agar plate containing SA, AA, MA, TA, 1,4-B, EG, SG and 1,4-C respectively as a sole carbon source was identified by the fatty acid methyl esters analysis . The modified Sturm test was carried out using the single isolated strain, an activated sludge or a mixed soil to measure the rate of mineralization of the compounds into carbon dioxide . The aliphatic compounds were mineralized more easily than the aromatic compounds . 1,4-C showed the most exceptionally slow degradation . A scrutiny of residual 1,4-C after degradation is required before polyesters containing 1,4-C could be classified into compostable because 1,4-C has detrimental effects on young radish seeds and HeLa cells and has a tendency to accumulate in the environment due to its slow degradability.

Water Res, 2001 Jul, 35(10), 2543 - 53
A simple system to rapidly monitor activated sludge health and performance; Archibald F et al.; A set of four assays designed to rapidly measure the health and biodegradative performance of pulp and paper mill activated sludges was developed . Three of the assays are specific oxygen uptake rates (SOURs) that measure the normal "working" aeration tank BOD (biochemical oxygen demand) removal rate (SOURAT), a near-maximum BOD removal rate (SOURNMAX), and a rate (SOURTOX) used in combination with the SOURNMAX to indicate the presence of toxic or inhibitory substances . The fourth assay is the specific adenosine triphosphate (SATP) content of the sludge, used as a measure of its viable cell content . Fresh biomass (sludge) samples from one laboratory reactor and four mill biotreatment systems were fed raw mill effluents and used to evaluate the four-assay set . The SOURAT values of all systems were 10-40% of their SOURNMAX values: thus the SOURAT:SOURNMAX ratios indicate that each system's free biodegradative capacity was far greater than its operating rate . It was demonstrated using phenol that the SOURNMAX:SOURTOX ratio can indicate the presence of substances toxic or inhibitory to the biomass . The results also indicated that the SOURNMAX is a much better indicator of improving or worsening sludge performance and capacity than the SOURAT . SATP was shown to be a useful monitor of the proportion of viable cells in an activated sludge and a toxicity indicator complementary to the SOURNMAX:SOURTOX ratio and similar in principle to the commercial Microtox toxicity test . This four-assay set was also applied to three practical situations: (a) at-mill monitoring of a biotreatment system; (b) effects of cold storage on biomass; and (c) effects of decreased BOD loading on biomass.

Water Res, 2001 Jul, 35(10), 2523 - 33
The fate of xenobiotic organic compounds in wastewater treatment plants; Byrns G; The effective operation of wastewater treatment plants plays an important role in minimising the release of xenobiotic compounds into the aquatic environment . Considerable effort has been expended in developing models to quantify the overall removal and fate of these compounds in biological treatment plants . A synthesis and modification of these approaches has been made and a generalised fate model for organic compounds in an activated sludge plant is presented . The influence of the different removal mechanisms, such as sorption, volatilisation and advection for chemicals with different physico-chemical properties is investigated and the important role of biotransformation is discussed . The effect of some operating parameters has been found to have an important influence upon the concentration of xenobiotic released in the sludges and final effluent . This may have significance for a wide range of ecotoxic compounds and in particular the class of compounds increasingly recognised as having the potential to disrupt endocrine activity in some aquatic vertebrates.

Water Res, 2001 Jul, 35(10), 2377 - 84
Experimental analysis of centrifugal dewatering process of polyelectrolyte flocculated waste activated sludge; Chu CP et al.; The study experimentally investigated the centrifugal separation of moisture from activated sludge subject to cationic polyelectrolyte flocculation . An arm-suspended centrifuge was employed which allowed in-situ detection on all positions of interfaces of centrifuged sludge as functions of time . Experimental results revealed that, sludge flocculation would yield a significant sedimentation effect at the first phase of centrifugation . Therefore, not as suggested in conventional centrifugal-filtration models, the most significant moisture-removal stages included filtrate to flow through a wet cake . Moreover, an optimal rotational speed exists at which the moisture-removal rate reaches a maximum value . New theories/correlations are required to describe centrifugation dewatering of polyelectrolyte flocculated sludge.

Water Sci Technol, 2001, 43(8), 83 - 90
Evaluation of flocculation and dissolved air flotation as an advanced wastewater treatment; Pinto Filho AC et al.; A bench scale study was carried out in order to evaluate the applicability of dissolved air flotation (DAF) as an advanced treatment for effluents from three different domestic wastewater treatment processes, namely: (i) a tertiary activated sludge plant; (ii) an upflow sludge blanket anaerobic reactor (UASB); and (iii) a high-rate stabilization pond.

Environ Sci Technol, 2001 May 15, 35(10), 1989 - 95
Organochlorine pesticide residues in archived UK soil; Meijer SN et al.; Archived background soils ("Broadbalk', 1944-1986) and sludge-amended soils ("Luddington", 1968-1990), collected from long-term agricultural experiments in the UK, were analyzed for a range of organochlorine (OC) pesticides to establish trends over time . Concentrations typically ranged from 0.1 to 10 ng/g of soil (dry weight), with gamma-hexachlorocyclohexane (gamma-HCH), dieldrin, and p,p'-DDE consistently having the highest concentrations . The trends in the Broadbalk background soils are largely consistent with usage patterns, with peak concentrations occurring in the 1960s for DDTs and between the 1960s and the 1980s for the other OCs . In the Luddington control and sludge-amended soils, several of the OCs show a significant decline in concentrations from the late 1960s to 1990, with half-lives ranging from approximately 7 years (alpha-HCH) to approximately 25 years (dieldrin) . The sludge-amended plot received 125 tonnes of sludge per ha in 1968, which was mixed in to a depth of 15 cm . It appears that the sludge treatment had little effect on concentrations in the soil, with no significant difference between control soil and sludge-amended soil for most compounds, except for HCB, p,p'-DDE, and dieldrin . Enantiomeric fractions (EFs) of some chiral pesticides (alpha-HCH, cis- and trans-chlordane, and o,p'-DDT) were determined in the Luddington soils . Results reveal that enantioselective degradation of OC pesticides is occurring in these soils for trans-chlordane (TC) and cis-chlordane (CC) . However, the depletion over time is not statistically significant, and there is no statistically significant difference between EFs in the control soil and sludge-amended soil . This indicates that enantioselective microbial degradation was not consistent over time and that the addition of sludge to soil did not significantly alter the enantiomeric preference of the microbial community.

Biotechnol Prog, 2001 May-Jun, 17(3), 462 - 7
Treatment of high strength distillery wastewater (cherry stillage) by integrated aerobic biological oxidation and ozonation; Beltran FJ et al.; The performance of integrated aerobic digestion and ozonation for the treatment of high strength distillery wastewater (i.e., cherry stillage) is reported . Experiments were conducted in laboratory batch systems operating in draw and fill mode . For the biological step, activated sludge from a municipal wastewater treatment facility was used as inoculum, showing a high degree of activity to distillery wastewater . Thus, BOD and COD overall conversions of 95% and 82% were achieved, respectively . However, polyphenol content and absorbance at 254 nm (A(254)) could not be reduced more than 35% and 15%, respectively, by means of single biological oxidation . By considering COD as substrate, the aerobic digestion process followed a Contois' model kinetics, from which the maximum specific growth rate of microorganisms (mu(max)) and the inhibition factor, beta, were then evaluated at different conditions of temperature and pH . In the combined process, the effect of a post-ozonation stage was studied . The main goals achieved by the ozonation step were the removal of polyphenols and A(254) . Therefore, ozonation was shown to be an appropriate technology to aid aerobic biological oxidation in the treatment of cherry stillage.

Ecotoxicol Environ Saf, 2001 Jun, 49(2), 144 - 54
Effects of pulp mill effluents and restricted diet on growth and physiology of rainbow trout (Oncorhynchus mykiss); Mattsson K et al.; Juvenile female rainbow trout was exposed for 4.5 months (June to October) to two dilutions of untreated and activated sludge treated whole mill effluent from a pulp mill producing bleached ECF pulp . Two controls were used, on fed ad libitum and a second receiving 0.5% feed of the body weight . All effluent exposed groups were fed ad libitum . Mean weight of the fish was measured monthly . At the end of the experiment a number of physiological and biochemical parameters were analyzed in order to establish the physiological status of the exposed fish in comparison with unexposed fish that obtained ad libitum or restricted amount of feed . The fish exposed to treated effluent grew significantly more than ad libitum control fish until August, whereupon growth retarded in fish exposed to the lower effluent dilution (400 v/v) . The growth of fish exposed to untreated effluent did not deviate significantly from the control fed ad libitum . The results from the hematological analysis clearly showed that fish fed restricted amount of feed deviated significantly in most parameters compared with the control fed ad libitum . Fish exposed to treated effluent showed a response pattern similar to that of the control fed restricted amount of feed, whereas the fish exposed to untreated effluent showed a response pattern that did not deviate from that of the ad libitum control . The metabolic parameters suggested that fish exposed to treated effluent had a higher metabolic demand than ad libitum control and that the energy allocation at the end of the experiment was directed to processes other than growth . The responses on hematology were mainly a consequence of the increased energy demand and were not primary effects . The implications of using feed related parameters at field studies are discussed .

Ecotoxicol Environ Saf, 2001 May, 49(1), 40 - 53
Structure of microbial communities in activated sludge: potential implications for assessing the biodegradability of chemicals; Forney LJ et al.; Various methods used to assess the biodegradability of chemicals often employ activated sludge as an inoculum since chemicals that ultimately enter the environment are often discharged through wastewater . Differences in the structure and function of activated sludge microbial communities that may complicate interpretation of biodegradation tests could arise from differences in wastewater composition, wastewater treatment plant (WWTP) operation, or manipulations done after collection of the activated sludge . In this study, various methods were used to characterize the structure of microbial communities found in freshly collected activated sludge from WWTPs in Japan, Europe, and the United States, as well as sludge that had been continuously fed either sewage or a glucose-peptone mixture for several weeks after collection . Comparisons of biomass levels, whole-community substrate utilization (determined using Biolog GN and GP plates), and phospholipid fatty acid (PLFA) profiles indicated there were both geographical and temporal differences among freshly collected activated sludge samples . Moreover, marked shifts in the structure of activated sludge microbial communities occurred upon continuous cultivation in the laboratory for 5 weeks using a glucose-peptone feed . These shifts were evident from whole-community substrate utilization and PLFA profiles as well as differences in the profiles of 16S rDNA genes from numerically dominant populations obtained by denaturing gradient gel electrophoresis and terminal restriction fragment analyses . Further studies are needed to better define the variability within and between activated sludge from wastewater treatment plants and laboratory reactors and to assess the impact of such differences on the outcome of biodegradability tests .

Water Sci Technol, 2001, 43(7), 97 - 104
On-line viable biomass measurement and estimation of the specific growth rate of activated sludge from municipal wastewater treatment; November EJ et al.; In order to control wastewater processes, on-line measurements of important process variables are crucial . This contribution focuses on the applicability of the Biomass Monitor for on-line viable biomass measurement of activated sludge from a municipal wastewater plant . In addition, the specific growth rate of the sludge is estimated on-line, based on the information derived from the device under study . Compared to dry weight measurements, the Biomass Monitor hardware offers the advantage of a biologically more appropriate observation of the biomass by only taking into account the viable cells in the population . The optimal measurement frequency of the biomass monitoring device for the given experimental conditions has been determined . Furthermore, the capacitance readings have been correlated with off-line analyses of dry weight of the sludge during the experimental phase in which no death of cells occurred . Finally, an evaluation of the estimator of the specific growth rate including its tuning is presented.

Water Sci Technol, 2001, 43(7), 91 - 6
Automated monitoring of activated sludge in a pilot plant using image analysis; da Motta M et al.; An automated procedure for the characterisation by image analysis of the morphology of activated sludge has been used to monitor the biomass in a pilot wastewater treatment plant, in complement to the usual settleability (sludge volume index, settling velocity) and size distribution (by laser granulometry) measurements.

Water Sci Technol, 2001, 43(7), 9 - 17
Modelling of activated sludge acclimisation to a non-ionic surfactant; Carvalho G et al.; A model is proposed to describe activated sludge acclimatisation to a non-ionic surfactant . The model was calibrated automatically, using WEST, a specific software environment for wastewater treatment model building, simulation and parameter estimation . The assays have been performed in a sequencing-batch reactor (SBR), using a non-ionic surfactant as sole carbon source and non-acclimatised sludge . The best fitting model was based on the assumption of three sequentially degraded COD fractions, where the second fraction is a metabolite of the original molecule and the third fraction is a more slowly biodegradable metabolite resulting from the secondary degradation . For primary degradation, hydrolysis with no associated growth was assumed . The growth of microorganisms responsible for degradation of the second and third COD fractions was presumed to follow Haldane and first order kinetics, respectively . The model was able to fit four consecutive assays of the same acclimatisation process, using Brij 30 as carbon source, with different food/microorganism ratios . The parameters obtained showed that the (self-)inhibition of the growth on the second COD fraction decreased along acclimatisation.

Water Sci Technol, 2001, 43(7), 39 - 46
Modelling and simulation of the steady-state of secondary settlers in wastewater treatment plants; Queinnec I et al.; This paper discusses the steady-state modelling of thickening in circular secondary settlers of activated sludge processes . The limitations of the solid flux theory basic models to represent steady-state operating conditions serve as a basis to introduce more sophisticated models derived from computational fluid dynamics . Parameter identification and sensitivity studies have been performed from lab-scale continuous experiments.

Water Sci Technol, 2001, 43(7), 367 - 76
A systematic approach to error isolation in computerized wastewater simulation models; Lennox JA et al.; Activated sludge models are used extensively in the study of wastewater treatment processes . While various commercial implementations of these models are available, there are many people who need to code models themselves using the simulation packages available to them . Quality assurance of such models is difficult . While benchmarking problems have been developed and are available, the comparison of simulation data with that of commercial models leads only to the detection, not the isolation of errors . To identify the errors in the code is time-consuming . In this paper, we address the problem by developing a systematic and largely automated approach to the isolation of coding errors . There are three steps: firstly, possible errors are classified according to their place in the model structure and a feature matrix is established for each class of errors . Secondly, an observer is designed to generate residuals, such that each class of errors imposes a subspace, spanned by its feature matrix, on the residuals . Finally, localising the residuals in a subspace isolates coding errors . The algorithm proved capable of rapidly and reliably isolating a variety of single and simultaneous errors in a case study using the ASM1 activated sludge model . In this paper a newly coded model was verified against a known implementation . The method is also applicable to simultaneous verification of any two independent implementations, hence is useful in commercial model development.

Water Sci Technol, 2001, 43(7), 357 - 65
Parameter estimation procedure for complex non-linear systems: calibration of ASM No . 1 for N-removal in a full-scale oxidation ditch; Abusam A et al.; When applied to large simulation models, the process of parameter estimation is also called calibration . Calibration of complex non-linear systems, such as activated sludge plants, is often not an easy task . On the one hand, manual calibration of such complex systems is usually time-consuming, and its results are often not reproducible . On the other hand, conventional automatic calibration methods are not always straightforward and often hampered by local minima problems . In this paper a new straightforward and automatic procedure, which is based on the response surface method (RSM) for selecting the best identifiable parameters, is proposed . In RSM, the process response (output) is related to the levels of the input variables in terms of a first- or second-order regression model . Usually, RSM is used to relate measured process output quantities to process conditions . However, in this paper RSM is used for selecting the dominant parameters, by evaluating parameters sensitivity in a predefined region . Good results obtained in calibration of ASM No . 1 for N-removal in a full-scale oxidation ditch proved that the proposed procedure is successful and reliable.

Water Sci Technol, 2001, 43(7), 329 - 38
Identifiability and uncertainty analysis of the river water quality model no . 1 (RWQM1); Reichert P et al.; State of the art models as used in activated sludge modelling and recently proposed for river water quality modelling integrate the knowledge in a certain field . If applied to data from a specific site, such models are nearly always overparameterised . This raises the question of how many parameters can be fitted in a given context and how to find identifiable parameter subsets given the experimental layout . This problem is addressed for the kinetic parameters of a simplified version of the recently published river water quality model no . 1 (RWQM1) . The selection of practically identifiable parameter subsets is discussed for typical boundary conditions as a function of the measurement layout . Two methods for identifiable subset selection were applied and lead to nearly the same results . Assuming upstream and downstream measurements of dissolved substances to be available, only a few (5-8) model parameters appear to be identifiable . Extensive measurement campaigns with dedicated experiments seem to be required for successful calibration of RWQM1 . The estimated prior uncertainties of the model parameters are used to estimate the uncertainty of model predictions . Finally an estimate is provided for the maximum possible decrease in prediction uncertainty achievable by a perfect determination of the values of the identifiable model parameters.

Water Sci Technol, 2001, 43(7), 29 - 38
Adequate model complexity for scenario analysis of VOC stripping in a trickling filter; Vanhooren H et al.; Two models describing the stripping of volatile organic contaminants (VOCs) in an industrial trickling filter system are developed . The aim of the models is to investigate the effect of different operating conditions (VOC loads and air flow rates) on the efficiency of VOC stripping and the resulting concentrations in the gas and liquid phases . The first model uses the same principles as the steady-state non-equilibrium activated sludge model Simple Treat, in combination with an existing biofilm model . The second model is a simple mass balance based model only incorporating air and liquid and thus neglecting biofilm effects . In a first approach, the first model was incorporated in a five-layer hydrodynamic model of the trickling filter, using the carrier material design specifications for porosity, water hold-up and specific surface area . A tracer test with lithium was used to validate this approach, and the gas mixing in the filters was studied using continuous CO2 and O2 measurements . With the tracer test results, the biodegradation model was adapted, and it became clear that biodegradation and adsorption to solids can be neglected . On this basis, a simple dynamic mass balance model was built . Simulations with this model reveal that changing the air flow rate in the trickling filter system has little effect on the VOC stripping efficiency at steady state . However, immediately after an air flow rate change, quite high flux and concentration peaks of VOCs can be expected . These phenomena are of major importance for the design of an off-gas treatment facility.

Water Sci Technol, 2001, 43(7), 19 - 27
A new approach towards modelling of the carbon degradation cycle at two-stage activated sludge plants; Winkler S et al.; A pilot plant has been operated in order to investigate the performance and operating characteristics of the plant concept developed for the extension of the main Vienna STP . Due to the different operational modes included in the plant concept, modelling of the carbon degradation becomes of crucial importance . A new activated sludge model is introduced which combines parts of the carbon degradation model concepts as they have been released in the ASM1-model and the ASM3-model, respectively . A method is presented which utilises results from mass balance calculations and sludge stabilisation experiments to reduce the uncertainty in the determination of the values of the simulation model parameters.

Water Sci Technol, 2001, 43(7), 167 - 74
Application of mathematical tools to improve the design and operation of activated sludge plants . Case study: the new WWTP of Galindo-Bilbao . Part II: Operational strategies and automatic controllers; Galarza A et al.; This paper presents a new sensitivity analysis methodology for Activated Sludge WWTPs . It is based on both (a) the calculation of the range of "manipulated input variables" that satisfy the restrictions imposed on the "output variables" and (b) on the computation of isolines of the output variables inside the feasible operating space . This analysis allows a more precise description of the operating constraints, facilitates the understanding of the steady-state behaviour of the process and detects possible areas where the process is very sensitive to small disturbances . The feasible operating space for two Activated Sludge WWTP processes for CN removal (RDN, DRDN), using SRT and DO level as "input variables" as well as effluent quality and exploitation costs as the main "output variables" is studied . The proposed methodology facilitates the selection of the appropriate operational strategy and the design of automatic controllers . Some examples of the application of this methodology for the design of automatic controllers in a real WWTP are briefly presented.

Water Sci Technol, 2001, 43(7), 157 - 65
Application of mathematical tools to improve the design and operation of activated sludge plants . Case study: the new WWTP of Galindo-Bilbao . Part I: Optimum design; Rivas A et al.; This paper presents a mathematical formulation for the optimum design of a new activated sludge WWTP . The WWTP optimum design problem has been formulated as a Mathematical Programming problem, which is solved through a nonlinear optimisation method . The plant model has been based on the ASM1 . The minimum volume of the biological reactors and the minimum total cost (including construction and exploitation costs) have been considered as optimisation criteria . Some practical results are also included, using as a case study the design of the second stage of the Galindo-Bilbao WWTP.

Water Sci Technol, 2001, 43(7), 131 - 8
Operational control of storm sewage at an activated sludge process; Chen J et al.; Operational control of storm sewage at a wastewater treatment plant has attracted intensive concern over the last decade in the context of river basin management . The focus is on the exploitation of the full capacity of the wastewater treatment plant in attenuating storm sewage, and minimizing a direct storm sewage bypass to the river . Attention is particularly paid to the surge of storm water on the activated sludge process . Based on two typical rain events, this paper discusses the performance of several practical controllers in achieving an optimal effluent performance under storm loadings, without risking internal biomass stability and sludge overflow . The control algorithms tested include various controls of recycle rate, step-feed and step-sludge . Prediction errors of influent characteristics and process responses are also under consideration in the assessment . The results illustrate well the desirability, effectiveness and robustness of the tested controllers.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2001, 36(2), 243 - 57
Kinetic analysis of inhibitory substrate degradation in bioaugmented activated sludge process; Liu WD et al.; A steady-state model coupling Haldane kinetics and mass conservative principles was developed herein to depict the degradation of a single inhibitory substrate in a bioaugmented activated sludge reactor . The substrate toxicity impact on the bioaugmentation was evaluated for three levels of inhibition coefficient Ki: 0.1, 10, and 1000 mg/L . Under high toxicity conditions of Ki = 0.1 mg/L, the input biomass markedly enhanced the substrate removal . However, at less toxicity of Ki > 10 mg/L, the input biomass was ineffective . The sensitivity study confirmed the parameters of k, Ks, and bd has no connection with Ki, but depends on the amounts of degradative bacteria inside the reactor . Alternatively, parameter Y is important only when Ki is greater than 10 mg/L and the bacteria significantly utilize the substrate . In addition, a novel indicator of marginal solids retention time examines the economic advantages of adding biomass as compared to extending the solids retention time.

Water Sci Technol, 2000, 41(3), 195 - 202
Full scale co-digestion of organic waste; Kubler H et al.; Operational results of a co-digestion facility were assessed over a period of 18 months . The organic fraction of municipal solid waste (OFMSW) contains a considerable amount of contaminants and grit (up to 6% w/w) . A BTA-Pulper efficiently treated the different waste streams and converted a high amount of volatile solids (VS) into the digester feedstock . The seasonal fluctuations of the waste composition significantly influenced the biogas production . The impact of this seasonally variant degradability of VS had to be considered by evaluating the operation results . The waste streams investigated did not show any negative impact on digester performance . The hydraulic retention time (HRT) in the digester considerably affected the VS-reduction . Despite a considerable decrease of VS-degradation a reduction of HRT from 14 to 8 days slightly improves the gas production rate (GPR) . An activated sludge system efficiently reduced the pollution of the effluent . The nutrient content of the anaerobic compost was favourable and the content of pollutants was low . The facility produced surplus electrical power up to 290 MJ/t . An overall energy balance shows that the facility substitutes primary energy.

Water Sci Technol, 2001, 43(6), 97 - 103
In situ detection of cell surface hydrophobicity of probe-defined bacteria in activated sludge; Nielsen JL et al.; The surface hydrophobicity of different types of bacteria in activated sludge were investigated under in situ conditions by following the adhesion of fluorescent microspheres with defined surface properties to bacterial surfaces (the MAC-method) . This technique was combined with identification of the bacteria with fluorescence in situ hybridization with rRNA-targeted oligonucleotides (FISH) and could thus be used for characterization of surface properties of probe-defined bacteria directly in a complex system without prior enrichment or isolation . This MAC-FISH technique could be used for single bacteria as well as filamentous bacteria . In the investigated activated sludge from an industrial wastewater treatment plant, two types of filamentous bacteria dominated . One morphotype consistently attracted only very few hydrophobic microspheres, indicating that the thin sheath of exopolymers around the cells had a hydrophilic surface . Use of a hierarchical set of gene probes revealed that these filaments were sulphide oxidising Thiothrix spp . The other predominating filamentous morphotype had a thick, very hydrophobic exopolymeric sheath . This filamentous bacterium was found to belong to the alpha-Proteobacteria . The relevance of the significant differences in surface hydrophobicity for the two morphotypes in respect to substrate uptake and floc formation is discussed.

Water Sci Technol, 2001, 43(6), 87 - 95
Fluorescence spectroscopy and molecular weight distribution of extracellular polymers from full-scale activated sludge biomass; Esparza-Soto M et al.; Two fractions of extracellular polymer substances (EPSs), soluble and readily extractable (RE), were characterised in terms of their molecular weight distributions (MWD) and 3-D excitation-emission-matrix (EEM) fluorescence spectroscopy signatures . The EPS fractions were different: the soluble EPSs were composed mainly of high molecular weight compounds, while the RE EPSs were composed of small molecular weight compounds . Contrary to previous thought, EPS may not be considered only as macromolecular because most organic matter present in both fractions had low molecular weight . Three different fluorophore peaks were identified in the EEM fluorescence spectra . Two peaks were attributed to protein-like fluorophores, and the third to a humic-like fluorophore . Fluorescence signatures were different from other previously published signatures for marine and riverine environments . EEM spectroscopy proved to be a suitable method that may be used to characterise and trace organic matter of bacterial origin in wastewater treatment operations.

Water Sci Technol, 2001, 43(6), 67 - 75
Quantification of the bond energy of bacteria attached to activated sludge floc surfaces; Mikkelsen LH et al.; The great majority of activated sludge bacteria exist incorporated in flocs . The increase in dispersed bacteria when exposed to increasing turbulent shear rates has been successfully modelled by a model assuming that the adhesion and erosion of cells may be considered in analogy to ordinary chemical phase transitions . By this adhesion-erosion model (AE-model), an "enthalpy" of cell adhesion can be estimated, and this value in turn determines the range of shear rates in which erosion of cells predominates . Application of the model has indicated that only a mass fraction less than ca . 6-17% may be released from activated sludge, even when exposed to a severe turbulent environment, i.e . only a small fraction of the flocs is dispersible by means of erosion by turbulence . The shear sensitivity and the dispersible floc fraction were found to depend on the floc composition . A net decrease in the floc EPS content during anaerobic sludge stabilisation causes a dramatic increase in the dispersed fraction, indicating the important role of EPS for the floc strength . It was found also that activated sludge cells do not reflocculate completely after exposure to high shear rates . This may be an indication that the cohesion energy of bacteria growing in colonies is greater than the energy of the more stochastic adhesion of dispersed cells to floc surfaces . It could also be another indicator of the importance of entanglement forces, which do not reform instantly, once broken . When the bond strength of cell attachment to sludge surfaces is altered by changes in the chemical environment, this may cause a change in the dispersible floc fraction as well as a change in the shear range of erosion . When the shear sensitivity constant kss is adopted for sludge characterisation, an increased degree of dispersion under standard test conditions will result in increased shear sensitivity estimates . The shear sensitivity may be used for the estimation of en equivalent change in the Gibb's energy of cell adhesion (delta (delta Gad/RT)).

Water Sci Technol, 2001, 43(6), 59 - 66
Adsorption of heavy metals by EPS of activated sludge; Liu Y et al.; Extracellular polymeric substances (EPSs) were extracted by high-speed centrifugation at 20,000 G for 30 min from an activated sludge treating municipal wastewater . Each gram of sludge, as measured in volatile suspended solids (VSS), contained 7.3 mg of EPS, including 6.5 mg of protein (EPSp) and 0.8 mg of carbohydrate (EPSc) . The EPSp had a mean MW of 2.0 x 105; about 18% of EPSp had MW over 5 x 104 and 16% below 5 x 103 . For heavy metal concentrations ranging 10-100 mg/l, EPS on average removed 99% of Zn2+, 98% of Cu2+, 97% of Cr3+, 85% of Cd2+, 69% of Co2+, 37% of Ni2+, and 26% of CrO4(2-) . The relative degrees of metal removals were inconsistent with those reported for the activated sludge process . Each mg of ESP had the capacity to remove up to 1.48 mg of Zn2+, 1.12 mg of Cu2+, 0.83 mg of Cr3+, 0.90 mg of Cd2+, 1.10 mg of Co2+, 0.25 mg each of Ni2+ and CrO4(2-) . Results suggest the feasibility of recovering ESP from waste sludge for use as adsorbent . Freundlich isotherm correlated satisfactorily with the adsorption data of Ni2+, Cu2+, Cd2+, and CrO4(2-) (R2 ranging 0.89-0.97), whereas Langmuir isotherm correlated satisfactorily with those of Zn2+, Cr3+ and Ni2+ (R2 ranging 0.93-0.96) . Both correlated poorly for those of Co2+.

Water Sci Technol, 2001, 43(6), 33 - 40
Hydrolysis of wastewater colloidal organic matter by extracellular enzymes extracted from activated sludge flocs; Guellil A et al.; Enzymatic activities associated with the exopolymeric substances (EPSs) extracted from activated sludges were tested for their ability to hydrolyse the organic colloidal fraction of wastewater . Bacteria extracted with EPS and concentrated by wastewater microfiltration were inhibited with NaN3 or KCN . The protein hydrolysis mainly resulted from the enzymatic activity of EPS, whereas the glycolytic activity was mainly present in the organic colloidal fraction of the wastewater.

Water Sci Technol, 2001, 43(6), 25 - 31
A new method for extraction of extracellular polymeric substances from biofilms and activated sludge suitable for direct quantification of sorbed metals; Wuertz S et al.; A method for extraction of extracellular polymeric substances (EPSs) with a dicyclohexyl-18-crown-6 ether was developed to determine levels of organic and inorganic contaminants sorbed to EPS . The crown ether selectively binds alkaline and alkaline earth metals but not heavy metals . The effectiveness of the extraction procedure was higher than that of 2 other methods tested and comparable with that of a method based on a cation exchange resin . On average it was possible to extract 20% of the TOC, 12% of the total protein content, and 4% of the total carbohydrate content of sludge or biofilm biomass . Metal sorption studies in activated sludge showed no influence of exposure time on the fractionation of metals within the biomass . Metals sorbed mostly to cellular material . In biofilms 12.2% of the cadmium and 9.1% of the zinc added was found in the EPS . In activated sludge EPS contained only 2.9% zinc . The distribution of metals within the biomass was dose dependent . The percentage of metals found in EPS decreased with increasing metal concentration . This indicates a higher affinity of metals for cellular binding sites . Time course experiments in a rotating biofilm annular reactor, which consisted of an external cylinder with removable slides and an internal solid drum, revealed a gradual change in zinc concentration associated with EPS, although the total zinc concentration in the biomass remained constant . Concurrently, the amount of extractable EPS decreased . This was a consequence of a microbial population shift, with bacterial counts decreasing and algal and fungal biomass increasing . Using confocal laser scanning microscopy and the fluorescent metal complexing agent Newport Green for in situ detection of zinc it was shown that metals were bound to algae and fungi in the latter part of the experiment . The biofilm became more and more heterogeneous coinciding with a decrease in EPS . To summarize, the observed sorption behavior of metals cannot be explained with the conventional paradigm of EPS as hydrophilic gel . Obviously, different binding mechanisms must be invoked to explain the role of EPS in the sorption and removal of toxic substances in activated sludge and biofilm systems . It is important to consider the microbial population to understand differences in sorption in different matrices.

Water Sci Technol, 2001, 43(6), 174 - 84
Cell surface and exopolymer characterization of laboratory stabilized activated sludge from a beverage bottling plant; Boyette SM et al.; Fermentor-stabilized activated sludge from an industrial beverage bottling plant was grown on three different food sources: normal plant wastewater, plant wastewater containing high sucrose concentrations, and a synthetic glucose-based feed stock . Surface charge, hydrophobicity, and exopolysaccharide composition were measured on the stabilized bacterial flocs . Cell surface charge was measured by electrophoretic mobility, dye exchange titration, and a standard colloid titration, while cell hydrophobicity was determined using the bacterial adhesion to hydrocarbons (BATH) test . Exopolysaccharide profiles were determined by measuring concentrations of glucose, galactose, mannose, glucuronic, and galacturonic acids in digested exopolymer extractions using HPLC . Changes in the physical surface properties of the bacteria and the chemical composition of the extracted exopolymers were correlated with differences in the three food sources . Cell surface hydrophobicity was similar for cultures grown on different plant wastewaters, while the culture grown on synthetic food produced less floc hydrophobicity . Electrophoretic mobility measurements, charge titrations, and dye exchange titrations showed different total surface charge as well as varying charge availability . Additionally, total surface charge and total exopolysaccharide concentrations appeared less dependent on food source than the food-to-mass ratio . High concentrations of biodegradable food produced dispersed growth and high concentrations of exopolysaccharides that contributed to poor settling.

Water Sci Technol, 2001, 43(6), 17 - 23
Remember the water--a comment on EPS colligative properties; Keiding K et al.; The relationship between water and activated sludge components was examined . Reevaluation of published data on freezing point depression, drying rates and dewatering has been performed . The basis of this has been the assumption that the water/sludge relationship is considered to be a colligative effect . Since the results indicate this to be the case, we suggest that the published concepts of "pools of water" are false . Data on swelling properties of EPS as a function of pH suggests that the colligative properties are largely determined by the counterions of charged polymers and surfaces.

Water Sci Technol, 2001, 43(6), 105 - 12
SEM-EDS for determining the phosphorus content in activated sludge EPS; Oosthuizen DJ et al.; Not all phosphorus removed in activated sludge systems can be accounted for by polyphosphate accumulating organisms (PAO) . A method for the qualitative and quantitative in situ characterization of PAO cell clusters and closely associated extracellular polysaccharides (EPS) is described . X-ray microanalysis was performed on samples from four activated sludge plants situated in Pretoria, South Africa . Analyses were done by means of Scanning Electron Microscopy (SEM) 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 23 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 . Extraction of EPS from two different activated sludge plants yielded different amounts of EPS, which, in combination with SEM-EDS, may shed light on different phosphate uptake abilities of different activated sludges.

Water Sci Technol, 2001, 43(3), 77 - 84
Performance of triple ditch: effects of duration and periodic operation programs; Ma LM et al.; The periodic variation of operation states in triple ditch (BIO-DENITRO process) was investigated in a pilot-scale and a full-scale triple ditch treating raw wastewater containing 70% petrochemical wastewater and 30% domestic wastewater . Mathematical models describing the periodic variation of activated sludge concentrations in each ditch were proposed based on theoretical analysis and were verified in the pilot-scale and full-scale triple ditches respectively . The existence of optimal cycle time and time arrangement of periodic operation programs were demonstrated and discussed according to the mathematical models and the experimental results of the pilot-scale triple ditch operated in four different stages . Four rulers determining the duration and operation programs are suggested.

Water Sci Technol, 2001, 43(3), 35 - 43
Using the flexibility index to compare batch and continuous activated sludge processes; Hopkins LN et al.; This paper considers the question of which is better: the batch or the continuous activated sludge processes? It is an important question because dissension still exists in the wastewater industry as to the relative merits of each of the processes . A review of perceived differences in the processes from the point of view of two related disciplines, process engineering and biotechnology, is presented together with the results of previous comparative studies . These reviews highlight possible areas where more understanding is required . This is provided in the paper by application of the flexibility index to two case studies . The flexibility index is a useful process design tool that measures the ability of the process to cope with long term changes in operation.

Water Sci Technol, 2001, 43(3), 323 - 30
SBR technology in Germany--an overview; Teichgraber B et al.; The SBR technology is applied in about 1.3% of the wastewater treatment plants (WWTP) in Germany . This caused the German Association for the Water Environment (ATV) to prepare the guideline ATV-M 210 to represent the state of the art for this type of WWTPs in Germany . The basic design parameters were derived from the standard ATV-A 131 for activated sludge plants to prepare a basis for the comparison of alternatives . In Bavaria numerous small WWTPs utilize SBR technology . Operational experiences show that these plants require specifically trained personnel . The plants produce effluents comparable to those of continuous flow plants in every respect . Hence the choice of system can be based on economic criteria.

Water Sci Technol, 2001, 43(3), 215 - 22
Simulation and applications of a novel modified SBR system for biological nutrient removal; Wu W et al.; Dynamic simulation and applications of a novel, continuous-fed, constant level modified sequencing batch reactor for biological nutrient removal are presented . The underlying mathematical model and practical applications of the simulation are discussed . Case studies are presented to illustrate the applications as well as the flexibility of the system in meeting different wastewater treatment requirements . Operation experience from full-scale wastewater treatment plant demonstrates the reliability, ease of operation and high efficiency of the system . Average BOD5, total nitrogen, total phosphorus and TSS removals of 97, 81, 88 and 94% are achieved respectively on an annual basis with little operator attention . Consistently high waste activated sludge concentrations are demonstrated, averaging approximately 20,000 mg/L.

Water Sci Technol, 2001, 43(3), 131 - 8
Performance of an SBR-plant for advanced nutrient removal, using septic sludge as a carbon source; Morling S; The Tjustvik SBR-plant outside Stockholm, Sweden has been in operation for four years . The plant has to meet stringent effluent standards, BOD7 < 10 PPM, total N < 15 PPM and total P < 0.3 PPM . The plant is a typical two reactor SBR-plant, sized for about 15,000 inhabitants . During the first year of operation there were difficulties in meeting the P consent level . The difficulties were linked to a deficit of available organic carbon and a secondary phosphorus release . The problem was solved with the addition of septic sludge, in an amount equivalent to about 10,000 to 15,000 inhabitants with respect to the BOD-load . The altered operation resulted in a very stable and good effluent quality from the plant that has been maintained ever since, giving typical discharge levels as follows: BOD7, < 3 mg/l; Total-P, < 0.15 mg/l; Total-N, < 7 mg/l; NH4-N, < 1 mg/l . The change of process saved the community from a major investment in a separate treatment facility for the septic sludge . The stabilisation degree of the waste activated sludge is sufficient to by pass the anaerobic digestion for the time being . In the beginning, the SBR-process stability played an unwanted role during start up as it maintained a secondary phosphorus release for a considerable time . Later the process stability became an asset as the varying loads from the septic sludge addition were handled with very good results.

Water Sci Technol, 2001, 43(3), 1 - 8
Monitoring of the microbial community of a sequencing batch reactor bioaugmented to improve its phosphorus removal capabilities; Dabert P et al.; The acclimatisation of an activated sludge to enhanced biological phosphorus removal conditions was followed after and without bioaugmentation with a low amount of phosphorus-accumulating sludge . Phosphorus removal yields were monitored by conventional analytical methods and microbial communities evolutions were followed by a finger printing molecular technique (PCR-SSCP) . While the benefit of the bioaugmentation seems real at the level of the reactor parameters, bioaugmentation speeded up the installation of good and stable phosphorus removal yield, the establishment of the inoculated microbial community in the bioaugmented reactor is still unclear . Both the bioaugmented and the control microbial communities evolved in a similar way to end up with apparently comparable populations . At the time of the experiment, the results suggest that the microbial community inoculated for the bioaugmentation did not establish in the reactor but compensated for phosphorus accumulation until the acclimatisation of an endogenous microbial community arose.

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2001, 36(1), 101 - 15
Activated sludge immobilization using the PVA-alginate-borate method; An M et al.; The PVA-alginate-borate method was used successfully to immobilize activated sludge . The optimum polyvinyl alcohol (PVA) concentration in the immobilized sludge was determined to be 10-12.5% . A minimal alginate of 1% in the beads was needed to prevent bead agglomeration . If the pH of the saturated boric acid was adjusted to 7.0 prior to allowing droplets of the mixture of PVA, alginate and sludge to enter the solution, a high level of sludge activity could be maintained in the beads formed . During the continuous operation of a fluidized bed reactor, with hydraulic retention time (HRT) in the range of 24-3 h (BOD loading from 0.176 to 0.766 kg/d/m3) and an aeration rate at 1.0 L/min, more than 90% of BOD5, NH4(+)-N and TKN were removed . The immobilized sludge exhibited satisfactory mechanical stability without apparent breakage.

Water Sci Technol, 2001, 43(2), 51 - 8
Changes in the organic composition of wastewater during biological treatment as studied by NMR and IR spectroscopies; Dignac MF et al.; Despite its importance, relatively little is known about the composition and fate of wastewater organic matter (OM) in treatment plants . Monitoring the chemical changes in OM during activated sludge treatment can improve our knowledge of the processes involved in the biological elimination of OM . Direct chemical analyses of treated water OM typically account for about 20% of the OM, and structural information was obtained in this study using Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) spectroscopic techniques . Distinct changes in the OM during wastewater biological treatment were underlined . 13C and 1H NMR showed that aromatic carbons were minor constituents of the samples . Alkyl chains exhibited a more highly branched character in treated water, as compared to long chain aliphatic carbons present in wastewater . Carboxyl signals in the 13C NMR spectrum of wastewater could be due to peptide bonds in proteins, whereas in the treated water spectrum, this signal could be related to the presence of non-proteinaceous nitrogen . Besides the non-degraded compounds, treated water OM could contain recondensation products of simple molecules . Their refractory character probably derives from their complex structures rather than from particular chemical functions, as suggested by the lack of fundamental differences in the chemical structures of wastewater and treated water OM.

Water Sci Technol, 2001, 43(2), 355 - 62
Comparison of dye wastewater treatment by normal and anoxic + anaerobic/aerobic SBR activated sludge processes; Panswad T et al.; In this research, the effects of different color intensities, anoxic + anaerobic times and types of substrate on color removal effectiveness were studied using 16-litre bench scale sequencing batch reactor (SBR) anoxic + anaerobic/aerobic models . The systems were fed with a synthetic wastewater containing 500 mg/l of COD, 50 mg/l of N, 15 mg/l of P along with 10, 40 and 80 mg/l of reactive diazo Remazol Black B dye . The anoxic + anaerobic/aerobic periods were 0/11 (normal aerobic SBR), 2/9, 4/7 and 8/3 hours, respectively . The color removal occurred mainly under the anaerobic environment, while a slight attenuation was noticed under the aerobic condition . A better decolorization could be achieved with a longer anoxic + anaerobic period . The sodium acetate was a slightly better co-substrate for the color removal than glucose . The decolorization efficiency dwindled as the fed dye concentration increased, but the overall color removal leaned in the opposite direction . The phosphorus removal of the anoxic + anaerobic/aerobic systems was outstanding, whereas only 50% removal was achieved for the aerobic process . A dye concentration of up to 80 mg/l did not have any significant impact on the performance of the polyphosphate accumulating organisms (PAOs) . The removal of organic carbon and TKN was comparable among all experiments regardless of system configurations, color intensities and types of substrate.

Water Sci Technol, 2001, 43(1), 99 - 106
Characterization of microbial community in an activated sludge process treating domestic wastewater using quinone profiles; Hu HY et al.; The dynamics of microbial community structure of activated sludges in a small-scale domestic wastewater treatment process were examined using a novel approach of quinone profiles . The composition and content of quinones in the activated sludges were analyzed monthly over a period of one year . More than 4 types of ubiquinones and 12 types of menaquinones were observed in the activated sludges, with the dominant quinones being ubiquinone (UQ)-8, menaquinone (MK)-7, followed by UQ-10, MK-8 and MK-6 . The total quinone contents in the activated sludges varied from 0.93 to 2.68 mumol per gram of particle organic carbon . The molar ratio of ubiquinones to menaquinones (UK/MK) changed from 0.38 to 0.98, indicating that anaerobic bacteria dominated the microbial community of the activated sludges examined . The ratio of UQ/MK varied similar to that of dissolved oxygen in the bulk . The microbial diversity of the activated sludges calculated from the quinone compositions was 13.4-16.8 . The diversity of menaquinones was much higher than that of ubiquinones, and increased slightly with increasing temperature . The microorganisms containing menaquinones appear to be sensitive to the change in temperature than those containing ubiquinones.

Water Sci Technol, 2001, 43(1), 91 - 8
16S rRNA in situ probing for the determination of the family level community structure implicated in enhanced biological nutrient removal; Mudaly DD et al.; Knowledge of a discrete physiological group capable of excess biological phosphate removal (EBPR) remains unclear . Consequently, microbial community analysis of an enhanced continuous laboratory-scale activated sludge process displaying a strong EBPR mechanism was conducted . Unit design was configured upon the three-stage Phoredox process and characterization of the activated sludge bacterial community was carried out using fluorescent in situ hybridization (FISH) techniques . Fixed activated sludge samples were hybridized with fluorescently labeled oligonucleotide probes targeting the following bacterial phylogenetic divisions: a kingdom level probe specific for all bacteria (EUB338); family level probes specific for the alpha, beta and gamma subclasses of the class Proteobacteria; Gram positive bacteria with a high (G + C) DNA content (GPBHGC) or Actinobacteria; the Cytophaga-Flavobacterium (CF) subclass within the Cytophaga-Flavobacterium-Bacteriodes division; and genus level probes specific for Pseudomonas spp., Aeromonas spp., and Acinetobacter spp . Bacterial predominance between the anaerobic, anoxic and aerobic zones of the EBPR sludge were comparable and appeared as follows; beta (22%), alpha (19%), gamma (17%), GPBHGC (11%) and CF (8%) . The incidence of Acinetobacter spp . appeared to be generally low with counts amounting to < 9% of the total bacterial count . A population shift in the alpha Proteobacteria subclass was evident between the non-nutrient removal seed sludge and the EBPR sludge, implicating this group in EBPR . The overall results indicate that the beta and alpha Proteobacteria can be metabolically functional in EBPR processes and reiterate the functional misconception of Acinetobacter spp . in EBPR systems.

Water Sci Technol, 2001, 43(1), 83 - 90
Biolog for the determination of microbial diversity in activated sludge systems; van Heerden J et al.; In this study, different carbon source profiles were generated by inoculating Biolog GN microwell plates, with different dilutions of microbial communities from a number of activated sludge systems . This led to the successful generation of patterns reflecting diversity and evenness in the different systems . The high number of substrates utilized at the lower dilutions (10(-1) and 10(-2)) indicated a high microbial diversity in the community, but not necessarily evenness of each species . Evenness of each species was reflected upon further dilution . Our results indicated differences in the microbial community composition amongst some of the activated sludge systems studied . These differences were not specifically related to phosphate removing and non phosphate removing systems.

Water Sci Technol, 2001, 43(1), 321 - 6
Removal of organics from wastewater using a novel biological hybrid system; al-Sharekh HA et al.; This paper summarizes the results obtained using the hybrid aerated submerged fixed-film (HASFF) process . HASFF is an innovative system comprising a four-compartment reactor having an array of fixed ceramic plates maintained under diffused aeration to support attached biomass, with activated sludge recycle to promote suspended growth in the reactor . Wastewater from a municipal treatment plant was fed to the reactor and its activated sludge was used for recycling in the hybrid system . Four pilot units were operated in the plant at various hydraulic retention times, HRTs (2, 4, 6 and 8 h), using primary-settled wastewater under organic loading rates up to 0.7 g BOD/gMLTVS . d . Data obtained showed that the overall BOD percentage removal efficiencies were consistently above 94.0% at all HRTs including the 2 hours while the COD percentage removal efficiencies ranged between 65.7-76% . The effluent's mean filtered BOD concentration ranged between 4.5-7.5 mg/l whereas the mean filtered COD concentration ranged between 70.0-89.6 mg/l . Increasing the hydraulic loading rate by four-folds from 0.08 to 0.32 m3/m2.d had a minor effect on the unit's BOD and COD percentage removal efficiencies indicating a robust biological process that is resilient to hydraulic shock loads, thereby offering a viable upgrading option.

Water Sci Technol, 2001, 43(1), 173 - 80
Microbial storage products, biomass density, and settling properties of enhanced biological phosphorus removal activated sludge; Schuler AJ et al.; The relationships between bacterial storage products, density, and settling characteristics were determined in a laboratory-scale sequencing batch reactor (SBR) enhanced biological phosphorus removal (EBPR) system . Both long-term and single anaerobic-aerobic cycle variations in these properties were studied . Increased polyphosphate (PP) content of the biomass during long-term operation resulted in improved sludge volume index (SVI) values . End-aerobic phase (after phosphate (P) uptake) SVI values were consistently lower than end-anaerobic phase (after P release) values . Neither filamentous nor slime bulking were evident by microscopic observations . Biomass density increased at a rate of 1.2 mg/L per each 1% increase in biomass P content . End-aerobic phase samples had an average 25% higher buoyant density than end-anaerobic phase samples; which was attributed to aerobic P uptake . Biomass density was negatively correlated with SVI values, and SVI values increased sharply at low biomass density . A mathematical model developed by Mas et al . (1985) was modified to predict total cell density based on literature values of PP, glycogen (GLY), and poly-b-hydroxybutyrate (PHB) densities . Model predictions were in good agreement with experimental results, although improved measurement of PP density is required to improve model predictions.

Water Sci Technol, 2001, 43(1), 165 - 72
Transformation of lipids in activated sludge; Dueholm TE et al.; Transformation of lipids in activated sludge treatment plants is of interest for two reasons: lipids contribute 30-40% of the chemical oxygen demand (COD) in wastewater, and they may stimulate the growth of filamentous microorganisms in nutrient removal activated sludge plants . The transformation of lipids was investigated under aerobic and anoxic conditions by measuring the oxygen and nitrate uptake rates (OUR and NUR) . The maximal OUR and NUR of long-chain fatty acid was found to be at the same level as acetate indicating that long-chain fatty acid was as easily consumable . However, the adsorption of long-chain fatty acid to surfaces of sludge flocs made it difficult to determine initial uptake rates of long-chain fatty acids . It was not possible to describe the hydrolysis rate of triacylglyceride by OUR and NUR to long-chain fatty acids because the hydrolysis rate was very slow . For a better description of the processes involved in transformation of lipids, a conceptual model was suggested . The processes in the suggested model were the adsorption/desorption of both triacylglyceride, and long-chain fatty acid onto surfaces of sludge flocs, hydrolysis of triacylglyceride by lipases and the uptake of long-chain fatty acid by bacteria under various conditions . The model can be helpful to structure design and evaluation of activated sludge experiment with lipids.

Water Sci Technol, 2001, 43(1), 123 - 30
Stress protein expression in domestic activated sludge in response to xenobiotic shock loading; Bott CB et al.; Using the Western blot immunochemical analysis method, the heat shock protein, GroEL, was found to be either induced or repressed in activated sludge microorganisms exposed to a range of xenobiotics . At the EC25 concentration, pentachlorophenol (PCP), cadmium, nickel, 2,4-dichloroaniline, benzoquinone, 2,4-dinitrophenol, and 1,1,1-trichloroethane all rapidly induced measurable GroEL expression, even though the time-dependent response for each of these compounds was somewhat varied . Toluene and hydroquinone resulted in repression of GroEL expression to levels below that measured in the control mixed liquor . For PCP concentrations at or exceeding the EC25, there was a significant and consistent increase in effluent volatile suspended solids from activated sludge sequencing batch reactors relative to unstressed controls . These preliminary results indicate that stress proteins may serve as sensitive and rapid indicators of toxicity which can adversely impact treatment process performance in activated sludge systems.

Water Res, 2001 Jun, 35(9), 2277 - 85
Storage and degradation of poly-beta-hydroxybutyrate in activated sludge under aerobic conditions; Dircks K et al.; This research analyses the accumulation and degradation of poly-beta-hydroxybutyrate (PHB) in experiments with pulse addition of acetate to samples of activated sludge from pilot-plant and full-scale wastewater treatment plants . The experiments are divided into two periods: a feast period defined as the time when acetate is consumed and a famine period when the added acetate has been exhausted . In the feast period the significant process occurring is the production of PHB from acetate . The produced PHB is utilised in the famine period for production of glycogen and biomass . According to modelling results approximately 90% of the total potential growth occurs in the famine period utilising the stored PHB . The degradation rate for PHB in the famine period is found to be dependent on the level of PHB obtained at the end of the feast period . It was found that multiple order kinetics gives a good description of the rate of PHB degradation . The examined sludge of low SRT origin is found to degrade PHB faster than long SRT sludge at high fractions of PHB . The observed yield of glycogen on PHB in the famine period is in the range of 0.22-0.33 g COD/g COD depending on the SRT . The storage pool of glycogen in the examined sludge is more slowly degraded than PHB (COD/COD/h).

Water Res, 2001 Jun, 35(9), 2137 - 44
Effect of pump shear on the performance of a crossflow membrane bioreactor; Kim JS et al.; The influences of pumping shear on the performance of a crossflow membrane bioreactor (MBR) were investigated . To compare the intensity of pumping shear, two types of pumps (a centrifugal pump and a rotary one) were used in turn to recirculate mixed liquor . Rotary pump system imposed much stronger shear to microbial floc than centrifugal one and resulted in severe floc breakage . Colloidal particles and organics were liberated from microbial floc by shear and caused rapid loss of membrane permeability by the formation of dense cake layers on the surface of membrane . Recirculation of mixed liquor with a rotary pump gradually increased the soluble COD in the bioreactor and deteriorated microbial activity . After 7 days' operation, specific oxygen uptake rate (SOUR) of microorganisms in rotary pump system reduced to 78%, of initial condition . With a centrifugal pump, however, buildup of soluble COD was not observed and change in microbial activity was negligible . Sludge yield in MBR process was lower than that (0.4-0.5 g MLVSS gCOD(-1)) reported in a conventional activated sludge process: 0.3 g MLVSS gCOD(-1) for the centrifugal pump system and 0.2 g MLVSS gCOD(-1) for the rotary pump system.

Biochem, Eng . J. . 2001 Jul, 8(1), 9 - 18
Removal of mixtures of acetaldehyde and propionaldehyde from waste gas in packed column with immobilized activated sludge gel beads; Ibrahim MA et al.; The removal of mixed acetaldehyde and propionaldehyde as a model of the binary contaminants in waste gas was studied in the packed column containing the immobilized activated sludge gel beads together with the hollow plastic balls developed for the removal of a single aldehyde in the previous work . The rate of each aldehyde biodegradation by the gel beads in the aldehydes mixture was expressed by the Michaelis-Menten type rate equation with an inhibitory term due to the other coexistent aldehyde . The kinetic parameters involved were found to be the same as those determined previously for biodegradation of a single aldehyde . A model for prediction of removal of each aldehyde in the packed column was developed assuming that each aldehyde dissolved in the aqueous phase within the gel bead was biodegraded according to the above rate equation with no mass transfer effect . The packed column was stable and efficient for removal of the binary aldehydes mixture with a very low pressure drop for gas flow due to a reduced gel beads bed compaction by the hollow plastic balls . Removal of each aldehyde decreased with increasing the inlet aldehyde concentrations since each biodegradation rate itself approached asymptotically the maximum one with increase in each aldehyde concentration . The observed removals for each aldehyde in the aldehydes mixture agreed well with those calculated from the design equations developed . The contact efficiency of gel beads with the waste gas stream was estimated to be the same value of 0.24 as in the previous work, supporting that the efficiency was specific to the geometrical and physical properties of the packed column used.

Biochem, Eng . J. . 2001 Jul, 8(1), 1 - 7
Kinetic analysis of disruption of excess activated sludge by Dyno Mill and characteristics of protein release for recovery of useful materials; Jung J et al.; Solubilization of excess sludge (ES) cultivated in a laboratory and that obtained from real wastewater treatment plants by continuous Dyno Mill disruption were studied for the purpose of effective reuse of ES . The total soluble protein concentration released during the ES disruption was found to be closely dependent upon the released protease activity, which suggests the possibility of the enzyme recovery as one of the ES reuse methods . The operating parameters of Dyno Mill significantly affected the ES solubilization . A high ES solubilization ratio of about 53%, defined by soluble TOC per total carbon contained in the laboratory-cultivated ES, was achieved by using glass beads of 0.5mm in diameter with the 60% (v/v) bead loading at the disc agitating speed of 3200rpm . The ES solubilization by the continuous mill disruption was successfully analyzed by a kinetic model consisting of first-order disruption kinetics . The collision frequency between the moving beads correlated well with the ES solubilization rate constant under all the operating conditions . This study proposes the applicability of mill disruption to the ES solubilization and to its reuse process.

Environ Technol, 2001 Feb, 22(2), 195 - 204
Prediction of mean circulation velocity in oxidation ditch; Simon S et al.; In wastewater treatment, oxidation ditches are used for the removal of carbon and nitrogen of activated sludge . The control of the single-phase flow is essential to the optimisation of the whole process . Among the two global functioning parameters (mean liquid velocity Uc, power dissipated per unit of volume P/V), the mean circulation velocity can be recommended . Indeed, the values of the power dissipated per unit of volume P/V obtained in different scale plant show that the industrial criterion on P/V leads to an overdesign of channel . Therefore a mean liquid circulation velocity Uc created by horizontal impellers must be maintained inside the ditch . In order to predict the velocity Uc, a model has been proposed based on the Equations of the continuity and motion and using a few simple parameters . Experiments were carried out on pilot plant (1 m3) and full scale ditches (860, 1400 and 2800 m3) in which the characteristics of the mixing system and the dimensions of channels were varied . A good agreement was observed between the model predictions and experimental data for the mean circulation velocity Uc.

Environ Sci Technol, 2001 Mar 15, 35(6), 1041 - 9
Distribution and behavior of nonylphenol, octylphenol, and nonylphenol monoethoxylate in Tokyo metropolitan area: their association with aquatic particles and sedimentary distributions; Isobe T et al.; Distributions of alkylphenols (APs) {i.e., nonylphenol (NP), octylphenol (OP)}, and nonylphenol monoethoxylate (NP1EO) in wastewater effluents, river water, and riverine and bay sediments in the Tokyo metropolitan area were demonstrated . During sewage treatments, NP and OP were efficiently removed from the sewage effluents through activated sludge treatments . Greater removal for NP (93% on average) than OP (84% on average) was consistent with their partitioning behavior to particles in primary and secondary effluents . NP concentrations in the river water samples ranged from 0.051 to 1.08 microg/L with higher concentrations in summer and spring than in colder seasons . In the river water samples, approximately 20% of NP was found in the particulate phase . Organic carbon-normalized apparent partition coefficients (K'OC) for NP (10(5.22 +/- 0.38)) and OP (10(4.65 +/- 0.42)) were 1 order of magnitude higher than those expected from their octanol-water partition coefficients (K(OW)), indicating strong affinity of APs to aquatic particles . Among NP isomers, no significant differences in their K'OC values were suggested . This is consistent with surprisingly uniform isomer peak profiles among the technical standard and all the environmental samples analyzed . NP and OP were widely distributed in the river sediments in Tokyo, and relatively high concentrations (0.5-13.0 microg/g dry) of NP were observed in a long reach (approximately 10 km) in the Sumidagawa River . In situ production of APs in the river sediment was suggested . Seaward decreasing trend in APs concentration was observed from the estuary to the Tokyo Bay . APs were well preserved in a sediment core collected from the bay . The profile shows subsurface maximum of AP concentrations in the layer deposited around the mid-1970s . The recent decrease in AP concentrations can be attributed to the legal regulation of industrial wastewater in the early 1970s.

Appl Microbiol Biotechnol, 2001 Apr, 55(3), 369 - 73
Biodegradation of tert-butyl alcohol and related xenobiotics by a methylotrophic bacterial isolate; Piveteau P et al.; A new aerobic bacterial strain, CIP 1-2052, isolated from an activated sludge sample, was able to use tert-butyl alcohol (TBA), a product of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) degradation, as its sole carbon and energy source . Cobalt ions stimulated TBA mineralization . The maximum growth and TBA degradation rates were 0.032 +/- 0.004 h(-1) and 35.8 +/- 8.5 mg TBA x g(-1) (cell dry mass) per h, respectively . The growth yield on TBA was 0.54 +/- 0.02 g x g(-1) . Strain CIP 1-2052 exhibited a particular substrate specificity towards alcohols . It degraded tertiary alcohols, TBA and tert-amyl alcohol (TAA), but neither their primary and secondary alcohol homologues, nor ethanol . However, one-carbon compounds, namely methanol and formate, were degraded by strain CIP 1-2052, showing the methylotrophic nature of this isolate . The properties of this new strain suggest that it could be used for bioremediation of contaminated aquifers.

Environ Toxicol Chem, 2001 May, 20(5), 941 - 6
Biodegradation of poly(tetramethylene succinate-co-tetramethylene adipate) and poly(tetramethylene succinate) through water-soluble products; Kitakuni E et al.; Poly(tetramethylene succinate-co-tetramethylene adipate) (PBSA) and poly(tetramethylenesuccinate) (PBS) were hydrolyzed experimentally into water-soluble oligomers and monomers by Chromobacterium extracellular lipase . The oligomers were identified by high-performance liquid chromatography-mass spectrometry and 1H-nuclear magnetic resonance, which indicated that a total of 28 oligomer species were liberated from PBSA, and that 13 of them were identical to the hydrolysates from PBS . Moreover, 20 of the species were polyester-based compounds of monomer units, and the other 8 species were small amounts of diurethane compounds . Bis(hydroxybutyl) succinate (BSB) and bis(hydroxybutyl) hexamethylene dicarbamate (BHB) were the typical oligomers and were chemically synthesized . Biodegradability of BSB and BHB was examined for 28 d in the activated sludge, and analysis of the results of this study indicated that the final conversion rate of constituent carbon to carbon dioxide was estimated at 80 mol% for BSB and 10 mol% for BHB . The remaining amount of carbon in the undegraded BHB was 20 mol% . In the presence of BSB, the biodegradability of BHB was increased by about 1.5 times . The suggestion was made that BSB induced a growth of microorganisms and helped BHB degradation . This is consistent with the observation that the biodegradation of BHB in native soil for 60 d reached > 60%.

Water Res, 2001 Jun, 35(8), 2038 - 48
A model for membrane bioreactor process based on the concept of formation and degradation of soluble microbial products; Lu SG et al.; A mathematical model of soluble microbial products (SMPs) formation-degradation was established based on the activated sludge model no . 1 and was applied to the membrane bioreactor process with high concentration of activated sludge under intermittent aerobic operational condition . The simulation results were in good agreement with the experimental data which indicated that the coefficients used in the model could successfully describe the treatment performance . The most advantage of this modified model over the conventional one was that the significant importance of SMP existence was demonstrated and the model provided an reasonable comprehension for SMP concept . The present study demonstrated that SMPs contributed most to the organic matter in the effluent, and the results coincided well with the observations of many other researchers.

Water Res, 2001 Jun, 35(8), 2010 - 6
Biodegradability of ethylenediamine-based complexing agents; Sykora V et al.; Biological degradability of ethylenediamine derivatives depends on the type and number of substituents . The susceptibility to biodegradation decreases in the sequence of substituents -COCH3, -CH3, -C2H5, -CH2CH2OH, -CH2COOH and with polysubstitution . The biodegradability depends also on the kind and number of nitrogen atoms . Complexing agents with a single-nitrogen atom in the molecule (e.g . NTA) succumb relatively readily to biodegradation whereas, compounds with two or more tertiary amino groups are biologically highly stable and do not undergo biodegradation even in experiments with activated sludge adapted at an age of up to 30 days (EDTA, DTPA, PDTA, HEDTA) . A lowering of the degree of substitution brings about an increased susceptibility to biodegradation . This holds, e.g., for replacement of tertiary amino groups with secondary ones; thus the symmetrically disubstituted ethylenediamine-N,N'-diacetic acid (EDDA) possesses still sufficient complexing ability while belonging already to the group of potentially degradable substances.

Water Res, 2001 Jun, 35(8), 2003 - 9
Ultrasonic waste activated sludge disintegration for improving anaerobic stabilization; Tiehm A et al.; The pretreatment of waste activated sludge by ultrasonic disintegration was studied in order to improve the anaerobic sludge stabilization . The ultrasound frequency was varied within a range from 41 to 3217 kHz . The impact of different ultrasound intensities and treatment times was examined . Sludge disintegration was most significant at low frequencies . Low-frequency ultrasound creates large cavitation bubbles which upon collapse initiate powerful jet streams exerting strong shear forces in the liquid . The decreasing sludge disintegration efficiency observed at higher frequencies was attributed to smaller cavitation bubbles which do not allow the initiation of such strong shear forces . Short sonication times resulted in sludge floc deagglomeration without the destruction of bacteria cells . Longer sonication brought about the break-up of cell walls, the sludge solids were distintegrated and dissolved organic compounds were released . The anaerobic digestion of waste activated sludge following ultrasonic pretreatment causing microbial cell lysis was significantly improved . There was an increase in the volatile solids degradation as well as an increase in the biogas production . The increase in digestion efficiency was proportional to the degree of sludge disintegration . To a lesser degree the deagglomeration of sludge flocs also augmented the anaerobic volatile solids degradation.

Environ Technol, 2001 Apr, 22(4), 477 - 86
Development of a case-based system for the supervision of an activated sludge process; Roda IR et al.; The development of a case-based reasoning system for the supervision of an activated sludge process is presented here . The methodology proposed permits the use of past experiences to solve new problems that arise in the process . These experiences are classified as cases or situations . The adaptation of cases and the generation of new cases are used to tune the response of the system and to learn from the new information generated by the process . The case and the case library definition, the initial seed, the search and retrieval process, the adaptation, the action, the evaluation and the learning steps are presented and outlined . The process studied is the wastewater treatment plant of Girona, Spain . Two examples of the response of the system to two different operational situations are presented . The paper also outlines the integration of different fields in a multidisciplinary approach as the most optimal solution to ensure the successful control and supervision of complex processes like the activated sludge process . With this aim the integration of an array of specific supervisory intelligent systems (for the logical analysis and reasoning) and numerical computations for detailed engineering is suggested.

Water Res, 2001 May, 35(7), 1804 - 16
Anaerobic codigestion of municipal solid waste and biosolids under various mixing conditions--I . Digester performance; Stroot PG et al.; The feasibility of codigestion of the organic fraction of municipal solid waste, primary sludge, and waste activated sludge was evaluated in mesophilic (37 degrees C), laboratory-scale digesters . In a first experiment, different startup strategies were compared using four digesters, operated under continuously mixed conditions . After two weeks, the experiment was continued under minimally mixed conditions . Results demonstrated that reducing the level of mixing improved digester performance . Therefore, in a second experiment, six digesters were operated to compare performance under continuous mixing and reduced mixing levels at various loading rates and solids levels . The continuously mixed digesters exhibited unstable performance at the higher loading rates, while the minimally mixed digesters performed well for all loading rates evaluated . In a third experiment, it was demonstrated that an unstable, continuously mixed digester was quickly stabilized by reducing the mixing level . These experiments confirmed that continuous mixing was not necessary for good performance and was inhibitory at higher loading rates . In addition, reduction of mixing levels may be used as an operational tool to stabilize unstable digesters.

Environ Microbiol, 2001 Feb, 3(2), 131 - 6
Complete mineralization of dodecyldimethylamine using a two-membered bacterial culture; Kroon AG et al.; Complete degradation of dodecyldimethylamine was achieved using a two-membered bacterial culture isolated from activated sludge . One member, identified as Burkholderia cepacia, was capable of degrading the alkyl chain of the molecule . The other member, identified as Stenotrophomonas maltophilia, was able to degrade dimethylamine, the product of the former . Batch culture experiments revealed that the two-membered culture consisting of B . cepacia and S . maltophilia was based on a commensalistic relationship under carbon-limited conditions . Under nitrogen-limited conditions, the relationship of this culture was transformed from a commensalistic to a mutualistic one . A two-membered culture was therefore imperative for growth on dodecyldimethylamine under nitrogen-limited conditions, whereas a pure culture of B . cepacia was capable of growth on dodecyldimethylamine under carbon-limited conditions.

J Appl Microbiol, 2001 Mar, 90(3), 309 - 19
RAPD-PCR typing of Acinetobacter isolates from activated sludge systems designed to remove phosphorus microbiologically; Carr E et al.; AIMS: This study investigated whether there were differences in RAPD fingerprints between already described genomic species of Acinetobacter and those from activated sludge systems . Whether plant-specific populations of acinetobacters exist was also examined . METHODS AND RESULTS: Fifty-two isolates of Acinetobacter from four biological phosphorus removal (EBPR) systems of different configurations, and the known genomic species, were characterized using RAPD-PCR, and fragments separated on agarose gels . Patterns were analysed using Gel Pro software and data analysed numerically . RAPD-PCR produced patterns suggesting that many environmental isolates differ from known genomic species . In two cases, strains from individual plants clustered closely enough together to imply that there may be plant-specific populations of acinetobacters . CONCLUSION: The data suggest that current understanding of the taxonomic status of Acinetobacter may need modifying to accommodate non-clinical isolates, as many of the clusters emerging after numerical analysis of RAPD-PCR fragments from activated sludge isolates were quite separate from the clusters containing the already described genomic species . Some evidence was also obtained from the clusters generated to support a view that particular populations of Acinetobacter may occur in individual activated sludge plants . SIGNIFICANCE AND IMPACT OF THE STUDY: These data suggest that the current understanding of the systematics of Acinetobacter, based as it is almost exclusively on clinical isolates, may need drastic revision to accommodate environmental strains . They also suggest that a re-examination of the importance and role of Acinetobacter in the activated sludge process may be appropriate.

Rocz Panstw Zakl Hig, 2000, 51(4), 417 - 24
{The effect of selected tannery chemical compounds on selected bacteria of activated sludge}; Mendrycka M et al.; Influence of tannery chemical compounds on the selected bacteria of the activated sludge was investigated . The chromium compounds must be diluted to 1:15-1:20 to loss its activity on the bacteria . Other compounds like: natrium chloratum, natrium formate and greased oils have any influence on the growth of the selected bacteria.

Environ Technol, 2001 Jan, 22(1), 113 - 22
The impact of residual coagulant on downstream treatment processes; Lees EJ et al.; A series of jar tests were undertaken to optimise for suspended solids (SS) and phosphorus removal from raw wastewater . The residual metal concentration in the settled wastewater from the jar test experiments and the residual concentration from the optimum doses plus two higher doses were selected for investigation . The identified levels of residual metal were fed into a four lane activated sludge pilot plant to investigate the impact of metal concentration on (i) activated sludge performance and (ii) sludge production and characteristics . Optimum pre-precipitation studies showed residual ion concentrations of 1.68 and 3.46 mg l-1 for Fe(III) and Al(III) respectively . At these levels %P removal increased by approximately 25 and 60% respectively . NH3 removal decreased by approximately 20 and 34% in the activated sludge treatment process . Chemically dosed biomass had a significantly lower oxygen uptake rate than the control which was accompanied by a reduction in VSS; 10% for Fe(III) and 17% for Al(III) . Changes in sludge characteristics were also observed . Chemical sludge had a greater settleability but a lower dewaterability than biological sludge . Sludge floc morphology was characterised which showed chemical flocs to be consistently smaller and visually denser than biological sludge flocs . The work presented in this paper considers the impact of residual iron and aluminium coagulants on downstream treatment processes.

Appl Environ Microbiol, 2001 Apr, 67(4), 1490 - 3
Method for host-independent detection of generalized transducing bacteriophages in natural habitats; Sander M et al.; Despite an increasing interest in horizontal gene transfer in bacteria, the role of generalized transduction in this process has not been well investigated yet . Certainly one of the reasons is that only a small fraction of general transducing bacteriophages have been characterized, because many bacterial hosts needed for propagation and identification are not culturable or are simply unknown . A method for host-independent detection of transducing bacteriophages was developed . Phage-encapsulated DNA was used as a template for PCR amplification of 16S ribosomal DNA using primers specific for the 16S rRNA genes of most eubacteria . Sequencing of the cloned amplification products permits the identification of the host bacteria . The Salmonella phage P22 was used as an example . Applying this method to a sample of the supernatant of the mixed liquor in the aeration tank of an activated sludge treatment works revealed the presence of transducing phages infecting several bacterial species for which such phages have not yet been described . This method is suitable for estimating the contribution of generalized transduction to horizontal gene transfer in different habitats.

Res Microbiol, 2001 Jan-Feb, 152(1), 105 - 12
Biodiversity and horizontal gene transfer in culturable bacteria isolated from activated sludge enriched in nonylphenol ethoxylates; Barberio C et al.; One hundred and twenty bacterial isolates, from activated sludge of a treatment plant collecting wastes enriched in ethoxylated nonylphenols, were studied . Sixty isolates were selected on rich medium and 60 on mineral medium containing two nonylphenol ethoxylates as the sole carbon source . Analysis of biodiversity at the species level was performed by comparing the AluI restriction patterns of the 16S ribosomal DNA amplified by PCR from 120 isolates . The rDNA restriction analysis enabled us to cluster the isolates into 15 groups, five of which represented nearly 77% of the community . Phylogenetic analysis of five strains belonging to these main groups made it possible to assign four of them to the genera Acinetobacter, Aeromonas and Shewanella and one to the Proteus group . The analysis of plasmid content showed a high variability and suggested that horizontal gene transfer had taken place at the intraspecific, interspecific and intergeneric levels.

Bioresour Technol, 2001 May, 77(3), 275 - 86
The treatment of pulp and paper mill effluent: a review; Thompson G et al.; The manufacture of paper generates significant quantities of wastewater; as high as 60 m3/tonne of paper produced . The raw wastewaters from paper and board mills can be potentially very polluting . Indeed, a recent survey within the UK industry has found that their chemical oxygen demands can be as high as 11000 mg/l . This paper reviews the processes involved in paper making and examines the effects which they could have on the environment . It also evaluates the treatment processes which are used to minimise these effects . In line with the majority of UK practice, it focuses mainly on aerobic biological treatment and, in particular, on the activated sludge process . This means that there is an in-depth discussion about the problems associated with filamentous bacteria and sludge "bulking" . The paper also discusses the way in which anaerobic digestion can be applied to the treatment of liquid wastes from the manufacture of paper.

Water Res, 2001 Apr, 35(5), 1219 - 24
The utilization of aniline, chlorinated aniline, and aniline blue as the only source of nitrogen by fungi in water; Emtiazi G et al.; The ability of fungi to degrade aniline and its derivatives in water is reported . Several fungi are able to degrade aniline and its derivatives as a sole nitrogen, carbon and energy source . Some of these fungi were obtained from activated sludge by enrichment technique . Among the 10 studied fungi, Fusarium sp . and Rhizopus sp . utilize aniline as a sole nitrogen, carbon and energy source, with production of acetanilide and catechol . Fusarium sp . utilized 70% of 10 mmol aniline and produced 3.55 mM ammonia during 30 days . Rhizopus sp . utilized 65% of 10 mmol aniline during 30 days . Rhizopus sp . and Fusarium sp . utilized only 2-chloroaniline and 3-chloroaniline as nitrogen source in the presence of glucose, with production of catechol, ammonium and chloride . The utilization of 2-chloroaniline was better than 3-chloroaniline, by Fusarium sp . and Rhizopus sp . Cladosporium sp . was the best isolate which could use aniline blue as the only source of nitrogen . This fungus reduced 89% of aniline blue, and ammonia is produced as the result of aniline blue biodegradation by Cladosporium sp.

Water Res, 2001 Jan, 35(1), 91 - 100
The immunochemical detection of stress proteins in activated sludge exposed to toxic chemicals; Bott CB et al.; The heat shock protein, GroEL, was found to be induced in activated sludge cultures exposed to perturbations of chemicals (cadmium, pentachlorophenol, and acetone) or heat stress . In laboratory activated sludge reactors, GroEL was rapidly induced (within minutes) in the presence of 5 mg/l or greater total cadmium . At 5 mg/l cadmium, however, moderate to insignificant changes in activated sludge process performance indicators {effluent suspended solids concentration, chemical oxygen demand (COD) removal, and specific oxygen uptake rate} were observed . As total cadmium concentrations increased above 5 mg/l, there was a significant and consistent increase in effluent volatile suspended solids concentrations from activated sludge sequencing batch reactors relative to unstressed controls . These results indicate that stress proteins may serve as sensitive and rapid indicators of mixed liquor toxicity which can adversely impact treatment process performance, but that GroEL may not be a good candidate protein for this purpose.

Water Res, 2001 Jan, 35(1), 49 - 56
Thermal pyrolysis characteristics of polymer flocculated waste activated sludge; Chu CP et al.; Polyelectrolyte conditioning is a common practice in wastewater management . This paper experimentally elucidated the thermal pyrolysis characteristics of waste activated sludge at a temperature range of 300-900 K (27-627 degrees C) using thermogravimetric analysis (TGA) in inert atmosphere, with especial attention on the effect of polyelectrolyte flocculation (using cationic polyacrylamide) . On the pyrolysis rate vs temperature plot two maxima were noted . At the heating rate of 8 degrees C/min, polyelectrolyte does not influence the pyrolysis process . As higher heating rates (14 and 20 degrees C/min), on the other hand, flocculation to charge neutralization point would enhance the rate of thermal pyrolysis . A simple two parallel-reaction kinetic model is applied to interpret the experimental data . Possible roles of flocculant on sludge pyrolysis are discussed on the basis of change in sludge structures and the hindrance of surface reactions of sludge particles.

Water Res, 2001 Jan, 35(1), 160 - 6
Hybrid reactor for priority pollutant-trichloroethylene removal; Misra C et al.; The present study was initiated to explore the potential of a hybrid biological reactor, combining trickling filter (TF) and activated sludge process (ASP), to treat wastewater containing trichloroethylene (TCE) at ambient temperature at different hydraulic retention time (HRT) . The biofilm acclimation was achieved in 55-60 days with gradual increase in TCE concentration from 1 mg/l to 100 mg/l with a parallel increase in the concentration of substrate sodium acetate and other nutrients . COD and TCE concentration were taken as prime parameters for monitoring the growth of biofilm . During acclimation COD removal varied between 54.6-97.5% while TCE was removed 72.6-99.9% . HRT study was performed after acclimation . The removal efficiency increased with decreasing flow rate with maximum TCE removal (99.99%) at 6 l/d corresponding to an HRT of 28 h (TF 18 h + ASP 10 h) . This was followed by a C:N:P ratio study . A ratio of 100:20:1 led to the sustenance of maximum TCE removal . Maximum TCE removal (99.99%) was observed at a substrate:cosubstrate ratio of 100:1 . A pH of 7.4 +/- 0.2 was found to be optimum for degradation . Finally, volatilization losses were estimated to be 18.5% . A mass balance gave an efficiency of 81.51% for biological removal of TCE.

Water Res, 2001 Jan, 35(1), 151 - 9
Controlled struvite crystallisation for removing phosphorus from anaerobic digester sidestreams; Munch EV et al.; Enhanced biological phosphorus removal wastewater treatment plants that use anaerobic digesters for sludge treatment, have high phosphorus concentrations in the sidestreams from their sludge dewatering equipment . To remove phosphorus from such sidestreams controlled struvite crystallisation can be used . Struvite (or MAP) is a naturally occurring crystal of magnesium, ammonium and phosphate . We present operational results obtained with a continuously operated pilot-scale MAP reactor . The pilot-scale reactor (143 l) was an air agitated column reactor with a reaction and a settling zone, based on the Phosnix process of Unitika Ltd., Japan . The influent to the MAP reactor was centrate from the centrifuge that dewaters anaerobically digested sludge at the Oxley Creek wastewater treatment plant in Brisbane . We used a 60% magnesium hydroxide slurry to add the required magnesium to the process and to obtain the alkaline pH value required . The pilot-scale MAP process achieved an ortho-P removal ratio of 94% from an average influent ortho-P concentration of 61 mg/l . The reactor was operated at a pH of around 8.5 . Insufficient dosing of magnesium reduced the P removal performance . There was no influence of the hydraulic residence time on the process in the range of 1-8 h . The dry MAP product had cadmium, lead and mercury concentrations well below the legal limits for fertilisers in Queensland, Australia and can be reused as a valuable slow-release fertiliser.

Water Res, 2001 Jan, 35(1), 143 - 50
Transfer of organic matter between wastewater and activated sludge flocs; Guellil A et al.; The organic matter of wastewater was fractionated into settleable (i.e., particulate) and non-settleable (i.e., colloidal + soluble) fractions by settling followed by 0.22 micron filtration . Particulate, colloidal and soluble proportions were found to be relatively constant (45, 31 and 24% of the total COD, respectively) . Transfer of soluble fraction always occurred from the wastewater to the activated sludge flocs, whereas bidirectional transfer occurred for the colloidal fraction . The transfer of soluble and colloidal matter reached a steady state after 40 min-mixing and 20 min-mixing, respectively . Desorption of a part of the colloidal organic matter pre-sorbed on the activated sludge flocs was evidenced . The biosorption capacity of activated sludge was around 40-100 mgCODg-1TSS . The biosorbable fraction of wastewater represented on average 45% of the non-settleable fraction.

Water Res, 2001 Jan, 35(1), 129 - 34
Influence of transient substrate overloads on the proliferation of filamentous bacterial populations in an activated sludge pilot plant; Pernelle JJ et al.; Using oligonucleotide probes directed at the rRNA of filamentous bacteria, this study looks at the influence of the components of transient substrate overloads on the growth of the dominant filamentous bacteria of activated sludge fed by a synthetic substrate . By dissociating the massive input of organic matter from the oxygen shortage that the latter generally induces, it is revealed that each of these factors applied alone, induces only transitory, small-scale growth of the filaments Nostocoida limicola, Haliscomenobacter hydrossis . Thiothrix and of type 021N . In contrast, combining them during a reconstituted transient substrate overload with an artificially created oxygen deficit, induces very fast growth of H . hydrossis which is responsible for establishing major proliferation . This massive proliferation was easily reduced by chlorination.

Biotechnol Bioeng, 2001 Apr 20, 73(2), 85 - 94
Glycogen metabolism in aerobic mixed cultures; Dircks K et al.; In this study, the metabolism of glycogen storage and consumption in mixed cultures under aerobic conditions is described . The experimental results are used to calibrate a metabolic model, which as sole stoichiometric variables has the efficiency of oxidative phosphorylation (delta) and maintenance requirement in units of adenosine triphosphate (m(ATP)) . Using the experimental data and values from the literature we show that delta and m(ATP) are strongly coupled and that the values determined for glycogen and poly-beta-hydroxybutyrate (PHB) metabolism are similar . We also demonstrate that storage of glycogen and subsequent growth occur without significant loss of energy, as compared with direct growth on glucose . For kinetic modeling, Monod kinetics is used most commonly in activated sludge models to describe the rate of microbial transformation . Monod kinetics, however, does not provide a good description of the data obtained . Second-order kinetics gives a better description of the rate of glycogen degradation . Formation and consumption of glycogen appears to be much faster than for PHB .

Syst Appl Microbiol, 2000 Dec, 23(4), 528 - 34
The filamentous bacterial morphotype 'Nostocoida limicola' I contains at least two previously described genera in the low G+C gram positive bacteria; Liu JR et al.; Isolates of eight bacterial filaments fitting the published morphological description of 'Nostocoida limicola' I were obtained from the mixed liquor of four different Australian and one Czech Republic activated sludge plants by micromanipulation . On the basis of their near complete (Ben 200 and Ben 201), or partial (Ben 77, Ben 78, Ben 202, Ben 203, Ben 204 and Ben 205) 16S rRNA gene sequences, six of these isolates were 99.3-100% similar to Lactosphaera pasteurii and Trichococcus flocculiformis, a bulking filament only reported previously in Germany . The other two (Ben 203 and Ben 204) were 99.9% similar to Streptococcus suis . Hence, all are in the low mol % G+C gram-positive bacteria division of the Bacteria . On this evidence 'N . limicola' I is phylogenetically unrelated to 'Nostocoida limicola' II, which is now known to be in the Actinobacteria, even though these two filamentous bacteria appearing in activated sludge systems have been considered to be closely related to each other historically.

Environ Microbiol, 2000 Feb, 2(1), 51 - 8
Modification of the aggregation behaviour of the environmental Ralstonia eutropha-like strain AE815 is reflected by both surface hydrophobicity and amplified fragment length polymorphism (AFLP) patterns; Bossier P et al.; After inoculation of the plasmid-free non-aggregative Ralstonia eutropha-like strain AE815 in activated sludge, followed by reisolation on a selective medium, a mutant strain A3 was obtained, which was characterized by an autoaggregative behaviour . Strain A3 had also acquired an IncP1 plasmid, pLME1, co-aggregated with yeast cells when co-cultured, and stained better with Congo red than did the AE815 strain . Contact angle measurements showed that the mutant strain was considerably more hydrophobic than the parent strain AE815, and scanning electron microscopy (SEM) revealed the production of an extracellular substance . A similar hydrophobic mutant (AE176R) could be isolated from the AE815-isogenic R . eutropha-like strain AE176 . With the DNA fingerprinting technique repetitive extragenic palindromic-polymerase chain reaction (REP-PCR), no differences between these four strains, AE815, A3, AE176 and AE176R, could be revealed . However, using the amplified fragment length polymorphism (AFLP) DNA fingerprinting technique with three different primer combinations, small but clear reproducible differences between the banding patterns of the autoaggregative mutants and their non-autoaggregative parent strains were observed for each primer set . These studies demonstrate that, upon introduction of a strain in an activated sludge microbial community, minor genetic changes readily occur, which can nevertheless have major consequences for the phenotype of the strain and its aggregation behaviour.

Water Res, 2001 Mar, 35(4), 929 - 36
pH sequential ozonation of domestic and wine-distillery wastewaters; Beltran FJ et al.; Domestic and wine-distillery wastewaters were treated by semi-batch and continuous pH sequential ozonations . The process involves a succession of acidic and alkaline wastewater pH conditions . The alkaline periods allow oxidation of organic matter by hydroxyl radical and produce carbonates that eventually would inhibit the oxidation . On the other hand, the acidic periods favour the development of direct ozone reactions and strip off carbonates as carbon dioxide from the wastewater . Experimental results of pH sequential ozonation showed degradation and removal rates of wastewater pollutants higher than those achieved at constant either acidic or basic pH . The most significant improvement of ozone efficiency and pollutants removal were obtained by controlling the number of cycles, pH and time of acidic and alkaline phases . Also, ozonated wastewaters showed high biodegradability as deduced from their BOD/COD ratios . The feasibility of treating domestic and wine-distillery wastewater by an integrated activated sludge (ASP)-pH sequential ozonation system was evaluated . Integrated ASP-ozonation at constant pH processes were also carried out for comparative purposes . In these combined experiments, pH sequential ozonation showed advantages compared to ozonation at constant pH in reducing global parameters such as COD, TOC and TKN, but ozonation at constant pH led to higher removal of polyphenols and UV254 absorbing compounds.

Water Res, 2001 Mar, 35(4), 883 - 90
Bioaugmentation with resin-acid-degrading bacteria enhances resin acid removal in sequencing batch reactors treating pulp mill effluents; Yu Z et al.; Resin acids are the major toxicants in pulp and paper mill effluents (PPMEs), and they form pitch interfering with papermaking . Efficient and reliable resin acid removal is critically important to prevent toxicity discharge and ensure proper functioning of paper machines . Two resin-acid-degrading bacteria, Pseudomonas abietaniphila BKME-9 and Zoogloea resiniphila DhA-35, were tested in laboratory sequencing batch reactors (SBRs) for their ability to enhance resin acid removal by biomass from a full-scale biotreatment system treating PPMEs . Both bacteria enhanced resin acid removal but not removal of total organic carbon (TOC) by either pH-shocked or starved activated sludge . These two bacteria also increased resin acid removal when the sludge was given high concentration (200 microM) of resin acid . A most-probable-number polymerase chain reaction (MPN-PCR) assay showed that these two bacteria were initially not detectable (detection limit: 10(2) bacterial cells/ml) in the sludge community and were persistent after inoculation . Both bacteria did not substantially change the indigenous microbial community composition, as assayed by ribosomal intergenic spacer analysis (RISA) . Our results suggest that it is feasible and potentially useful to enhance resin acid removal by bioaugmentation using resin-acid-degrading bacteria such as BKME-9 and DhA-35.

Water Res, 2001 Mar, 35(4), 1029 - 37
Effect of sludge fasting/feasting on growth of activated sludge cultures; Che GH et al.; Reduction of excess sludge in an oxic-settling-anoxic (OSA) activated sludge process might be attributed to a "sludge fasting (insufficient food under an anoxic condition)/feasting (sufficient food under an oxic condition)" treatment . This paper was to examine this explanation by investigating both the sludge fasting/feasting phenomenon and the effect of a fasting/feasting treatment on sludge growth . In this study, five different activated sludge cultures cultivated using synthetic wastewater composed of mainly glucose and other necessary nutrients: (1) an aerobic batch culture, (2) an intermittently aerated batch culture, (3) an anoxic batch culture, (4) a continuous aerobic culture, and (5) an OSA culture, were employed . It was found that only the aerobic batch culture and the aerobic continuous culture are fastable when the oxidation reduction potential (ORP) level is below 100 mV under no-food condition during a 2-h fasting treatment, showing that both the biomass and carbohydrate storage of these two cultures were reduced after the treatment . When the fasted cultures were treated in a feasting environment, an accumulation of carbohydrate storage did not occur, while specific oxygen uptake rates (SOUR) showed a sharp increase . Both the substrate utilization and biomass growth rates were also accelerated . It was therefore confirmed that a sludge feasting did occur after a fasting treatment for the fastable cultures . However, an increase in sludge ATP content was not brought about by the feasting treatment . The sludge fasting/feasting treatment in this paper could not induce a reduction of the observed growth yield (Y(obs)) in all the cultures cultivated with glucose-based synthetic wastewater.

Appl Microbiol Biotechnol, 2001 Jan, 55(1), 117 - 21
Biodegradation of ethyl t-butyl ether (ETBE), methyl t-butyl ether (MTBE) and t-amyl methyl ether (TAME) by Gordonia terrae; Hernandez-Perez G et al.; Gordonia terrae strain IFP 2001 was selected from activated sludge for its capacity to grow on ethyl t-butyl ether (ETBE) as sole carbon and energy source . ETBE was stoichiometrically degraded to t-butyl alcohol (TBA) and the activity was inducible . A constitutive strain, G . terrae IFP 2007, derived from strain IFP 2001, was also selected . Methyl t-butyl ether (MTBE) and t-amyl methyl ether (TAME) were not used as carbon and energy sources by the two strains, but cometabolic degradation of MTBE and TAME was demonstrated, to TBA and t-amyl alcohol (TAA) respectively, in the presence of a carbon source such as ethanol . No two-carbon compound was detected during growth on ETBE, but formate was produced during cometabolic degradation of MTBE or TAME . A monooxygenase was involved in the degradation of ethers, because no degradation of ETBE was observed under anaerobic conditions and the presence of a cytochrome P-450 was demonstrated in G . terrae IFP 2001 after induction by cultivation on ETBE.

Environ Microbiol, 2000 Aug, 2(4), 389 - 98
Studies on the in situ physiology of Thiothrix spp . present in activated sludge; Nielsen PH et al.; The in situ physiology of the filamentous sulphur bacterium Thiothrix spp . was investigated in an industrial wastewater treatment plant with severe bulking problems as a result of overgrowth of Thiothrix . Identification and enumeration using fluorescence in situ hybridization (FISH) with species-specific 16S and 23S rRNA probes revealed that 5-10% of the bacteria in the activated sludge were Thiothrix spp . By using a combination of FISH and microautoradiography it was possible to study the in situ physiology of probe-defined Thiothrix filaments under different environmental conditions . The Thiothrix filaments were very versatile and showed incorporation of radiolabelled acetate and/or bicarbonate under heterotrophic, mixotrophic and chemolithoautotrophic conditions . The Thiothrix filaments were active under anaerobic conditions (with or without nitrate) in which intracellular sulphur globules were formed from thiosulphate and acetate was taken up . Thiothrix-specific substrate uptake rates and growth rates in activated sludge samples were determined under different conditions . Doubling times of 6-9 h under mixotrophic conditions and 15-30 h under autotrophic conditions were estimated . The key properties that Thiothrix might be employing to outcompete other microorganisms in activated sludge were probably related to the mixotrophic growth potential with strong stimulation of acetate uptake by thiosulphate, as well as stimulation of bicarbonate incorporation by acetate in the presence of thiosulphate.

Water Res, 2001 Mar, 35(3), 786 - 94
Co-conditioning and dewatering of chemical sludge and waste activated sludge; Chang GR et al.; The conditioning and dewatering behaviors of chemical and waste activated sludges from a tannery were studied . Capillary suction time (CST), specific resistance to filtration (SRF), and bound water content were used to evaluate the sludge dewatering behaviors . Zeta potentials were also measured . Experiments were conducted on each sludge conditioned and dewatered separately, and on the sludge mixed at various ratios . Results indicate that the chemical sludge was relatively difficult to be dewatered, even in the presence of polyelectrolyte . When the waste activated sludge was mixed with the chemical sludge at ratios of 1:1 and 2:1, respectively, the dewaterability of chemical sludge improved remarkably while the relatively better dewaterability of the waste activated sludge deteriorated only to a limited extent . As the mixing ratios became 4:1 and 8:1, the dewaterability of the mixed sludge was equal to that of the waste activated sludge . The optimal polyelectrolyte dosage for the mixed sludge was equal to or less than that of the waste activated sludge . It is proposed that the chemical sludges act as skeleton builders that reduce the compressibility of the mixed sludge whose dewaterability is enhanced . Bound water contents of sludge decreased at low polyelectrolyte dosage and were not significantly affected as polyelectrolyte dosage increased . Advantages and disadvantages of co-conditioning and dewatering chemical sludge and waste activated sludge were discussed.

Fresenius J Anal Chem, 2000 May, 367(2), 157 - 64
Analysis of poly-beta-hydroxybutyrate in environmental samples by GC-MS/MS; Elhottova D et al.; Application of gas chromatography-mass spectrometry (GC-MS) can significantly improve trace analyses of compounds in complex matrices from natural environments compared to gas chromatography only . A GC-MS/MS technique for determination of poly-beta-hydroxybutyrate (PHB), a bacterial storage compound, has been developed and used for analysis of two soils stored for up to 319 d, fresh samples of sewage sludge, as well as a pure culture of Bacillus megaterium . Specific derivatization of beta-hydroxybutyrate (3-OH C4:0) PHB monomer units by N-tert-butyl-dimethylsilyl-N-methyltrifluoracetamide (MTBSTFA) improved chromatographic and mass spectrometric properties of the analyte . The diagnostic fragmentation scheme of the derivates tert-butyldimethylsilyl ester and ether of beta-hydroxybutyric acid (MTBSTFA-HB) essential for the PHB identification was shown . The ion trap MS was used, therefore the scan gave the best sensitivity and with MS/MS the noise decreased, so the S/N was better and also with second fragmentation the amount of ions increased compared to SIM . The detection limit for MTBSTFA-HB by GC-MS/MS was about 10(-13) g microL(-1) of injected volume, while by GC (FID) and GC-MS (scan) it was around 10(-10) g microL(-1) of injected volume . Sensitivity of GC-MS/MS measurements of PHB in arable soil and activated sludge samples was down to 10 pg of PHB g(-1) dry matter . Comparison of MTBSTFA-HB detection in natural soil sample by GC (FID), GC-MS (scan) and by GC-MS/MS demonstrated potentials and limitations of the individual measurement techniques.

Environ Microbiol, 2000 Dec, 2(6), 581 - 93
Microbiology of the 'G-bacteria' in activated sludge; Seviour RJ et al.; This review discusses a group of bacteria, the 'G-bacteria', which have a distinctive morphology of cocci in tetrads, sheets or clusters, that are seen in large numbers in many activated sludge biomass samples . Isolates of 'G-bacteria' that have been grown axenically are phylogenetically diverse . The Gram-negative members include several alpha- and beta-proteobacteria, among which is the genus Amaricoccus, while the Gram-positive 'G-bacteria' contain several members of the actinobacteria . It is probable that other, as yet uncharacterized, 'G-bacteria' exist in activated sludge . The hypothesis that these 'G-bacteria' are detrimental to the process of enhanced biological phosphate removal by competing for substrates anaerobically with the phosphate-accumulating bacteria in such systems, based as it is largely on mixed-culture studies, receives little support from studies using those available in pure culture . The evidence on which these conclusions are founded is discussed, as are the arguments used to explain why these 'G-bacteria' all appear to thrive under conditions found in certain activated sludge systems.

Int J Syst Evol Microbiol, 2001 Jan, 51(Pt 1), 195 - 202
Phylogeny of the filamentous bacterium 'Nostocoida limicola' III from activated sludge; Liu JR et al.; Five strains of the filamentous bacterium 'Nostocoida limicola' III were successfully isolated into pure culture from samples of activated sludge biomass from five plants in Australia . 16S rRNA gene sequence analyses showed that all isolates were members of the Planctomycetales, most closely related to Isosphaera pallida, but they differed phenotypically from this species in that they did not glide and were not thermotolerant . The ultrastructure of these 'N . limicola' III isolates was also consistent with them being Planctomycetales, in that they possessed complex intracellular membrane systems compartmentalizing the cells . However, the arrangements of these intracellular membranes differed between isolates . These data confirm that 'N . limicola' III is phylogenetically unrelated to both 'N . limicola' I and 'N . limicola' II, activated sludge filamentous bacteria which share morphological features in common with 'N . limicola' III and which have been presumed historically to be the same or very similar bacteria.

Environ Microbiol, 1999 Apr, 1(2), 125 - 35
Phylogeny and in situ identification of a morphologically conspicuous bacterium, Candidatus Magnospira bakii, present at very low frequency in activated sludge; Snaidr J et al.; A morphologically conspicuous bacterium that constituted a very small fraction (< 0.01%) of the total microbial community of activated sludge was enriched and analysed phylogenetically by a combination of cultivation-independent molecular and physical methods . The large, corkscrew-shaped, filamentous bacteria were first detected in municipal activated sludge by light microscopy owing to their unusual rotating gliding motility . Various attempts at microbiological enrichment and pure culture isolation with traditional techniques failed, as did attempts to retrieve the morphotype of interest by micromanipulation . In situ hybridization with the group-specific, rRNA-targeted oligonucleotide probe CF319a indicated a phylogenetic affiliation to the Cytophaga-Flexibacter group of the Cytophaga-Flavobacterium-Bacteroides phylum . Based on strong morphological resemblance to members of the genus Saprospira, additional 16S rRNA-targeted oligonucleotides with more narrow specificity were designed and evaluated for in situ hybridization to the morphotype of interest . Flow cytometric cell sorting based on the fluorescence conferred by probe SGR1425 and forward scatter enabled a physical enrichment of the helical coiled cells . Subsequent polymerase chain reaction (PCR) amplification of 16S rDNA fragments from whole fixed sorted cells with a primer pair based on probes CF319a and SGR1425 resulted in the retrieval of 12 almost identical partial 16S rDNA fragments with sequence similarities among each other of more than 99.2% . In situ hybridizations proved that the sequences that showed the highest similarity (88.4%) to the 16S rRNA of Saprospira grandis were indeed retrieved from the corkscrew-shaped filaments . The bacterium is likely to be a member of a genus of which no species has been cultured hitherto . It was consequently tentatively named 'Magnospira bakii' and has the taxonomic rank of Candidatus Magnospira bakii, as the ultimate taxonomic placement has to await its cultivation . In this study, it was demonstrated that even bacteria occurring at very low frequencies in highly complex environmental samples can be retrieved selectively without cultivation for further molecular analysis.

Lett Appl Microbiol, 2001 Feb, 32(2), 103 - 7
Empirical model for the autotrophic biodegradation of thiocyanate in an activated sludge reactor; du Plessis CA et al.; AIMS: The aim of this investigation was to develop an empirical model for the autotrophic biodegradation of thiocyanate using an activated sludge reactor . METHODS AND RESULTS: The methods used for this purpose included the use of a laboratory scale activated sludge reactor unit using thiocyante feed concentrations from 200 to 550 mg x l(-1) . Reactor effluent concentrations of <1 mg x l(-1) thiocyanate were consistently achieved for the entire duration of the investigation at a hydraulic retention time of 8 h, solids (biomass) retention of 18 h and biomass (dry weight) concentrations ranging from 2 to 4 g x l(-1) . A biomass specific degradation rate factor was used to relate thiocyanate degradation in the reactor to the prevailing biomass and thiocyanate feed concentrations . A maximum biomass specific degradation rate of 16 mg(-1) x g(-1) x h(-1) (mg thiocyanate consumed per gram biomass per hour) was achieved at a thiocyanate feed concentration of 550 mg x l(-1) . The overall yield coefficient was found to be 0.086 (biomass dry weight produced per mass of thiocyanate consumed) . CONCLUSION: Using the results generated by this investigation, an empirical model was developed, based on thiocyanate feed concentration and reactor biomass concentration, to calculate the required absolute hydraulic retention time at which a single-stage continuously stirred tank activated sludge reactor could be operated in order to achieve an effluent concentration of <1 mg x l(-1) . The use of an empirical model rather than a mechanistic-based kinetic model was proposed due to the low prevailing thiocyanate concentrations in the reactor . SIGNIFICANCE AND IMPACT OF THE STUDY: These results represent the first empirical model, based on a comprehensive data set, that could be used for the design of thiocyanate-degrading activated sludge systems.

J Theor Biol, 2001 Jan 7, 208(1), 27 - 36
Predation in the presence of decoys: an inhibitory factor on pathogen control by bacteriophages or bdellovibrios in dense and diverse ecosystems; Wilkinson MH; Several attempts have been made at the removal of specific pathogens from the intestinal microflora using either bacteriophages or "predatory" bacteria such as Bdellovibrio spp . To date these attempts have had mixed success . A mechanism explaining these findings based on competitive hindrance by non-prey, or decoy species is put forward . It is shown that this hindrance tends to damp out predator-prey oscillations, and therefore reduces the probability of prey extinction . Possible experiments to verify this theory are discussed . The decoy effect may play a role in any system with high densities of bacteria or other particulate matter, such as activated sludge or biofilms .

Appl Environ Microbiol, 2001 Feb, 67(2), 632 - 45
Alpha- and beta-Proteobacteria control the consumption and release of amino acids on lake snow aggregates; Schweitzer B et al.; We analyzed the composition of aggregate (lake snow)-associated bacterial communities in Lake Constance from 1994 until 1996 between a depth of 25 m and the sediment surface at 110 m by fluorescent in situ hybridization with rRNA-targeted oligonucleotide probes of various specificity . In addition, we experimentally examined the turnover of dissolved amino acids and carbohydrates together with the microbial colonization of aggregates formed in rolling tanks in the lab . Generally, between 40 and more than 80% of the microbes enumerated by DAPI staining (4',6'-diamidino-2-phenylindole) were detected as Bacteria by the probe EUB338 . At a depth of 25 m, 10.5% +/- 7.9% and 14.2% +/- 10.2% of the DAPI cell counts were detected by probes specific for alpha- and beta-Proteobacteria . These proportions increased to 12.0% +/- 3.3% and 54.0% +/- 5.9% at a depth of 50 m but decreased again at the sediment surface at 110 m to 2.7% +/- 1.4% and 41.1% +/- 8.4%, indicating a clear dominance of beta-Proteobacteria at depths of 50 and 110 m, where aggregates have an age of 3 to 5 and 8 to 11 days, respectively . From 50 m to the sediment surface, cells detected by a Cytophaga/Flavobacteria-specific probe (CF319a) comprised increasing proportions up to 18% of the DAPI cell counts . gamma-Proteobacteria always comprised minor proportions of the aggregate-associated bacterial community . Using only two probes highly specific for clusters of bacteria closely related to Sphingomonas species and Brevundimonas diminuta, we identified between 16 and 60% of the alpha-Proteobacteria . In addition, with three probes highly specific for close relatives of the beta-Proteobacteria Duganella zoogloeoides (formerly Zoogloea ramigera), Acidovorax facilis, and Hydrogenophaga palleroni, bacteria common in activated sludge, 42 to 70% of the beta-Proteobacteria were identified . In the early phase (<20 h) of 11 of the 15 experimental incubations of aggregates, dissolved amino acids were consumed by the aggregate-associated bacteria from the surrounding water . This stage was followed by a period of 1 to 3 days during which dissolved amino acids were released into the surrounding water, paralleled by an increasing dominance of beta-Proteobacteria . Hence, our results show that lake snow aggregates are inhabited by a community dominated by a limited number of alpha- and beta-Proteobacteria, which undergo a distinct succession . They successively decompose the amino acids bound in the aggregates and release substantial amounts into the surrounding water during aging and sinking.

Biochem, Eng . J. . 2001 Jan, 7(1), 79 - 84
Biosorption of reactive dyes by dried activated sludge: equilibrium and kinetic modelling; Aksu Z; The biosorption of reactive dyes (Reactive Blue 2 - RB2 and Reactive Yellow 2 - RY2) onto dried activated sludge was investigated . The dye binding capacity of biosorbent was shown as a function of initial pH, initial dye concentration and type of dye . The equilibrium data fitted very well to both the Freundlich and Langmuir adsorption models . The results showed that both the dyes uptake processes followed the second-order rate expression.

Ecotoxicol Environ Saf, 2000 Nov, 47(3), 314 - 22
Evaluation of an inactivation procedure for determining the sorption of organic compounds to activated sludge; Kerr KM et al.; A batch method was developed and validated for determining the sorption coefficient (Kd) of biodegradable organic compounds to activated sludge solids using a nonspecific analytical technique, total organic carbon (TOC) analysis . In this method, activated sludge solids were first inactivated by lyophilization and dry heat (103 degrees C) and then washed to remove any dissolved organic carbon released during the inactivation procedure . The inactivated sludge solids were exposed to a range of concentrations of different test compounds in synthetic wastewater until equilibrium was achieved (< 2 h) . The amount of test compound sorbed to the solids was then determined by measuring TOC levels in centrifuged supernatants . Results revealed that the sorption coefficients (Kd values) for four detergent chemicals in inactivated sludge solids using TOC analysis were in good agreement with values determined in fresh activated sludge using radiolabeled materials . These Kd values are suitable for use in estimating environmental exposure concentrations and for developing screening-level models to assess the removal of organic compounds by sorption and settling during activated sludge wastewater treatment.

Appl Environ Microbiol, 2001 Jan, 67(1), 411 - 9
Investigation of candidate division TM7, a recently recognized major lineage of the domain Bacteria with no known pure-culture representatives; Hugenholtz P et al.; A molecular approach was used to investigate a recently described candidate division of the domain Bacteria, TM7, currently known only from environmental 16S ribosomal DNA sequence data . A number of TM7-specific primers and probes were designed and evaluated . Fluorescence in situ hybridization (FISH) of a laboratory scale bioreactor using two independent TM7-specific probes revealed a conspicuous sheathed-filament morphotype, fortuitously enriched in the reactor . Morphologically, the filament matched the description of the Eikelboom morphotype 0041-0675 widely associated with bulking problems in activated-sludge wastewater treatment systems . Transmission electron microscopy of the bioreactor sludge demonstrated that the sheathed-filament morphotype had a typical gram-positive cell envelope ultrastructure . Therefore, TM7 is only the third bacterial lineage recognized to have gram-positive representatives . TM7-specific FISH analysis of two full-scale wastewater treatment plant sludges, including the one used to seed the laboratory scale reactor, indicated the presence of a number of morphotypes, including sheathed filaments . TM7-specific PCR clone libraries prepared from the two full-scale sludges yielded 23 novel TM7 sequences . Three subdivisions could be defined based on these data and publicly available sequences . Environmental sequence data and TM7-specific FISH analysis indicate that members of the TM7 division are present in a variety of terrestrial, aquatic, and clinical habitats . A highly atypical base substitution (Escherichia coli position 912; C to U) for bacterial 16S rRNAs was present in almost all TM7 sequences, suggesting that TM7 bacteria, like Archaea, may be streptomycin resistant at the ribosome level.

Appl Microbiol Biotechnol, 2000 Nov, 54(5), 719 - 23
Reclamation of an activated-sludge microbial consortium by selective biostimulation; Watanabe K et al.; Our previous study showed that an activated-sludge process broke down at the phenol-loading rate of 1.5 g l(-1) day(-1), when non-flocculating bacteria (called R6T and R10) overgrew the sludge, resulting in a sludge washout . In this study, we attempted to circumvent this breakdown problem by reclaiming the consortium structure . Activated sludge was fed phenol, and the phenol-loading rate was increased stepwise from 0.5 g l(-1) day(-1) to 1.0 g l(-1) day(-1) and then to 1.5 g l(-1) day(-1) . Either galactose or glucose (at 0.5 g l(-1) day(-1)) was also supplied to the activated sludge from the phenol-loading rate of 1.0 g l(-1) day(-1) . Pure culture experiments have suggested galactose to be a preferential substrate for a floc-forming bacterium (R6F) that predominantly degrades phenol under low phenol-loading conditions . Supplying galactose allowed sustainment of the R6F population and suppression of the overgrowth of R6T and R10 at the phenol-loading rate of 1.5 g l(-1) day(-1) . This measure allowed the activated-sludge process to treat phenol at a phenol-loading rate up to 1.5 g l(-1) day(-1), although it broke down at 2.0 g l(-1) day(-1) . In contrast, supplying glucose reduced the R6F population and allowed the activated-sludge process to break down at the phenol-loading rate of 1.0 g l(-1) day(-1) . This study demonstrated that reclamation of the activated-sludge consortium by selective biostimulation of the floc-forming population improved the phenol-treating ability of the process.

J Hazard Mater, 2001 Jan 29, 81(1-2), 193 - 203
The influence of different soil constituents on the reaction kinetics of wet oxidation of the creosote compound quinoline; Thomsen AB et al.; Creosote contaminated sites have become a widespread problem in industrialized countries . Recently, wet oxidation using high temperature, pressure, water and oxygen followed by activated sludge treatment proved to be an efficient method for removing a wide selection of creosote compounds in contaminated soils . Wet oxidation of the creosote compound quinoline was carried out in the presence of montmorillionite, quartz and humic acid . The products derived from wet oxidation were identified and treated biologically by activated sludge testing their biodegradability . The influence on the oxidation kinetics of quinoline during wet oxidation was pH dependent . Humic acid supported the oxidation of quinoline, whereas the addition of montmorillionite and quartz had either an inhibiting effect or led only to a slight increase in oxidation . In mixtures of soil constituents, especially at low contents of humic acid, the adsorption of quinoline on montmorillionite prevented oxidation at neutral pH . Thus, alkaline extraction of both quinoline and humic acid was needed for an efficient oxidation . A proposed reaction mechanism suggests that quinoline was oxidized by hydroxyl radicals formed during the oxidation of the humic acid . A wide selection of reaction products (mainly carboxylic acids, benzene and pyridine derivatives) derived from the wet oxidation of humic acid and quinoline . The reaction products from humic acid degradation had a rate limiting effect on the wet oxidation of quinoline leaving small residues of quinoline after the treatment . On the contrary, these reaction products also improved the biodegradation of products from the quinoline oxidation due to co-digestion of carboxylic acids . Therefore, the presence of soil components (mainly humic acid) improved the combined wet oxidation and biological activated sludge treatment of quinoline.

Int Microbiol, 2000 Jun, 3(2), 103 - 6
Assessment of microbial community structure changes by amplified ribosomal DNA restriction analysis (ARDRA); Gich FB et al.; Amplified ribosomal DNA restriction analysis (ARDRA) is a simple method based on restriction endonuclease digestion of the amplified bacterial 16S rDNA . In this study we have evaluated the suitability of this method to detect differences in activated sludge bacterial communities fed on domestic or industrial wastewater, and subject to different operational conditions . The ability of ARDRA to detect these differences has been tested in modified Ludzack-Ettinger (MLE) configurations . Samples from three activated sludge wastewater treatment plants (WWTPs) with the MLE configuration were collected for both oxic and anoxic reactors, and ARDRA patterns using double enzyme digestions AluI+MspI were obtained . A matrix of Dice similarity coefficients was calculated and used to compare these restriction patterns . Differences in the community structure due to influent characteristics and temperature could be observed, but not between the oxic and anoxic reactors of each of the three MLE configurations . Other possible applications of ARDRA for detecting and monitoring changes in activated sludge systems are also discussed.

Appl Environ Microbiol, 2000 Dec, 66(12), 5155 - 60
Coliform bacteria and nitrogen fixation in pulp and paper mill effluent treatment systems; Gauthier F et al.; The majority of pulp and paper mills now biotreat their combined effluents using activated sludge . On the assumption that their wood-based effluents have negligible fixed N, and that activated-sludge microorganisms will not fix significant N, these mills routinely spend large amounts adding ammonia or urea to their aeration tanks (bioreactors) to permit normal biomass growth . N(2) fixation in seven Eastern Canadian pulp and paper mill effluent treatment systems was analyzed using acetylene reduction assays, quantitative nitrogenase (nifH) gene probing, and bacterial isolations . In situ N(2) fixation was undetectable in all seven bioreactors but was present in six associated primary clarifiers . One primary clarifier was studied in greater detail . Approximately 50% of all culturable cells in the clarifier contained nifH, of which >90% were Klebsiella strains . All primary-clarifier coliform bacteria growing on MacConkey agar were identified as klebsiellas, and all those probed contained nifH . In contrast, analysis of 48 random coliform isolates from other mill water system locations showed that only 24 (50%) possessed the nifH gene, and only 13 (27%) showed inducible N(2)-fixing activity . Thus, all the pulp and paper mill primary clarifiers tested appeared to be sites of active N(2) fixation (0.87 to 4.90 mg of N liter(-1) day(-1)) and a microbial community strongly biased toward this activity . This may also explain why coliform bacteria, especially klebsiellas, are indigenous in pulp and paper mill water systems.

Biotechnol Bioeng, 2000 Dec 20, 70(6), 677 - 84
Two parameters account for the flocculated growth of microbes in biodegradation assays; Brandt BW et al.; Microbes in activated sludge tanks mostly occur in flocs rather than in cell suspensions . Flocculation results in a limited supply of substrate to the bacteria inside the flocs, which reduces the biodegradation rate of organic compounds by several orders of magnitude . This article presents a simple two-parameter extension of growth models for cell suspensions to account for the ensuing reduction of the degradation rate . The additional parameters represent floc size at division and diffusion length . The biomass of small flocs initially increases exponentially at a rate equal to that of cell suspensions . After this first phase, the growth rate gradually decreases and finally the radius becomes a linear function of time . At this time flocs are large and have a kernel of dead biomass . This kernel arises when the substrate concentration decreases below the threshold level at which cells are just able to pay their maintenance costs . We deduce an explicit approximative expression for the interdivision time of flocs, and thereby for the growth of flocculated microbial biomass at constant substrate concentrations . The model reveals that the effect of stirring on degradation rates occurs through a reduction of the floc size at division . The results can be applied in realistic biodegradation quantifications in activated sludge tanks as long as substrate concentrations change slowly.

Appl Environ Microbiol, 2000 Nov, 66(11), 5043 - 52
Phylogenetic analysis of and oligonucleotide probe development for eikelboom type 021N filamentous bacteria isolated from bulking activated sludge; Kanagawa T et al.; Fifteen filamentous strains, morphologically classified as Eikelboom type 021N bacteria, were isolated from bulking activated sludges . Based on comparative 16S ribosomal DNA (rDNA) sequence analysis, all strains form a monophyletic cluster together with all recognized Thiothrix species (88.3 to 98.7% 16S rDNA sequence similarity) within the gamma-subclass of Proteobacteria . The investigated Eikelboom type 021N isolates were subdivided into three distinct groups (I to III) demonstrating a previously unrecognized genetic diversity hidden behind the uniform morphology of the filaments . For in situ detection of these bacteria, 16S rRNA-targeted oligonucleotide probes specific for the entire Eikelboom type 021N-Thiothrix cluster and the Eikelboom type 021N groups I, II, and III, respectively, were designed, evaluated, and successfully applied in activated sludge.

J Antimicrob Chemother, 2000 Sep, 46 Suppl 1, 53 - 8; discussion 63-5
Environmental risk assessment of antibiotics: comparison of mecillinam, trimethoprim and ciprofloxacin; Halling-Sorensen B et al.; The effects of mecillinam, trimethoprim and ciprofloxacin, antibiotics used in the treatment of urinary tract infections, on the aquatic environment were assessed . Mecillinam and ciprofloxacin were both readily biodegradable (primary degradation) in activated sludge, whereas trimethoprim persisted . The toxicity of these antibiotics towards sludge bacteria, a green alga, a cyanobacterium, a crustacean and a fish were investigated; both mecillinam and ciprofloxacin were highly toxic to the cyanobacterium Microcystis aeruginosa (EC50 in the range 5-60 microg/L) . Risk characterization for the aquatic environment was performed for the three compounds by calculating the predicted environmental concentration (PEC) and the predicted no-effects concentration (PNEC) . A PEC/PNEC ratio of <1 indicates that, with the present pattern of use, no environmental risk is expected . PEC/PNEC ratios of <1 for present usage in Europe were found for mecillinam and trimethoprim whereas a PEC/PNEC ratio >1 was found for ciprofloxacin.

J Hazard Mater, 2000 Dec 1, 79(1-2), 173 - 87
Removal mechanisms of VOCs in an activated sludge process; Hsieh CC; This study investigated the factors in plant operating parameters effecting volatile organic compound (VOC) removal and elucidated each individual mechanism in an activated sludge process (ASP) . The results suggest that stripping increase with an increase in Henry's law constant with the exception of toluene, which differed because of the effect of biodegradation competition . The emission rate can be controlled by increasing the active biomass concentration (X(b)) in the aeration basin, hydraulic retention time (HRT), and oxygen transfer efficiency (OTE) . Increasing X(b) enhances total VOC removal and biodegradation, which reduces the fraction of the stripping removal . Longer HRT can reduce stripping removal significantly if other variables such as oxygen requirement and OTE are held constant . For the same volatile compound, a process with higher air-to-water ratio requires a higher active biomass concentration to reduce stripping removal . Increasing OTE decreases the air-to-water ratio requirement, which reduces the gas-phase transfer of VOCs into the atmosphere . The results show a reasonable agreement between measured and predicted stripping values.

J Antimicrob Chemother, 2000 Aug, 46 Suppl A, 53 - 58
Environmental risk assessment of antibiotics: comparison of mecillinam, trimethoprim and ciprofloxacin; Halling-Sorensen B et al.; The effects of mecillinam, trimethoprim and ciprofloxacin, antibiotics used in the treatment of urinary tract infections, on the aquatic environment were assessed . Mecillinam and ciprofloxacin were both readily biodegradable (primary degradation) in activated sludge, whereas trimethoprim persisted . The toxicity of these antibiotics towards sludge bacteria, a green alga, a cyanobacterium, a crustacean and a fish were investigated; both mecillinam and ciprofloxacin were highly toxic to the cyanobacterium Microcystis aeruginosa (EC(50) in the range 5-60 Ig/L) . Risk characterization for the aquatic environment was performed for the three compounds by calculating the predicted environmental concentration (PEC) and the predicted no-effects concentration (PNEC) . A PEC/PNEC ratio of <1 indicates that, with the present pattern of use, no environmental risk is expected . PEC/PNEC ratios of <1 for present usage in Europe were found for mecillinam and trimethoprim whereas a PEC/PNEC ratio >1 was found for ciprofloxacin.

Appl Environ Microbiol, 2000 Sep, 66(9), 3905 - 10
Starvation improves survival of bacteria introduced into activated sludge; Watanabe K et al.; A phenol-degrading bacterium, Ralstonia eutropha E2, was grown in Luria-Bertani (LB) medium or in an inorganic medium (called MP) supplemented with phenol and harvested at the late-exponential-growth phase . Phenol-acclimated activated sludge was inoculated with the E2 cells immediately after harvest or after starvation in MP for 2 or 7 days . The densities of the E2 populations in the activated sludge were then monitored by quantitative PCR . The E2 cells grown on phenol and starved for 2 days (P-2 cells) survived in the activated sludge better than those treated differently: the population density of the P-2 cells 7 days after their inoculation was 50 to 100 times higher than the population density of E2 cells without starvation or that with 7-day starvation . LB medium-grown cells either starved or nonstarved were rapidly eliminated from the sludge . The P-2 cells showed a high cell surface hydrophobicity and retained metabolic activities . Cells otherwise prepared did not have one of these two features . From these observations, it is assumed that hydrophobic cell surface and metabolic activities higher than certain levels were required for the inoculated bacteria to survive in the activated sludge . Reverse transcriptase PCR analyses showed that the P-2 cells initiated the expression of phenol hydroxylase within 1 day of their inoculation into the sludge . These results suggest the utility of a short starvation treatment for improving the efficacy of bioaugumentation.

Biochem, Eng . J. . 2000 Oct 1, 6(2), 145 - 151
Determination of the biosorption heats of heavy metal ions on Zoogloea ramigera and Rhizopus arrhizus; Sag Y et al.; The biosorption of Fe(III), Cr(VI), Pb(II), Cu(II) and Ni(II) ions on Zoogloea ramigera (activated sludge bacterium) and Rhizopus arrhizus (filamentous fungus) has been studied as a function of initial metal ion concentration and temperature . The applicability of the Langmuir model for each metal-microorganism system has been tested at different temperatures . The enthalpy change for the biosorption process has been evaluated by using the Langmuir constant b, related to the energy of adsorption . Thermodynamic parameters indicate the exothermic nature of Cu(II) and Ni(II) biosorption on both microorganisms . Fe(III), Cr(VI) and Pb(II) biosorption is determined to be an endothermic process since increased binding occurs as the temperature is increased in the range 15-45 degrees C.

Appl Microbiol Biotechnol, 2000 Jul, 54(1), 121 - 5
Biodegradability of volatile hydrocarbons of gasoline; Solano-Serena F et al.; The biodegradability under aerobic conditions of volatile hydrocarbons (4-6 carbons) contained in gasoline and consisting of n-alkanes, iso-alkanes, cycloalkanes and alkenes, was investigated . Activated sludge was used as the reference microflora . The biodegradation test involved the degradation of the volatile fraction of gasoline in closed flasks under optimal conditions . The kinetics of biodegradation was monitored by CO2 production . Final degradation was determined by gas chromatographic analysis of all measurable hydrocarbons (12 compounds) in the mixture after sampling the headspace of the flasks . The degradation of individual hydrocarbons was also studied with the same methodology . When incubated individually, all hydrocarbons used as carbon sources, except 2,2-dimethylbutane and 2,3-dimethylbutane, were completely consumed in 30 days or less with different velocities and initial lag periods . When incubated together as constituents of the light gasoline fraction, all hydrocarbons were metabolised, often with higher velocities than for individual compounds . Cometabolism was involved in the degradation of dimethyl isoalkanes.

J Hazard Mater, 2000 Oct 2, 77(1-3), 177 - 91
The use of municipal sewage sludge for the stabilization of soil contaminated by mining activities; Theodoratos P et al.; The ability of municipal sewage sludge to immobilize Pb, Zn and Cd contained in contaminated soil originating from a former mining area in Lavrion, Greece was investigated . The soil was cured with sewage sludge in various proportions . The stabilization was evaluated primarily by applying chemical tests and complemented by the performance of additional biological tests . Application of the U.S . EPA Toxicity Characteristic Leaching Procedure (TCLP) on the stabilized mixtures proved that Pb, Zn and Cd solubility was reduced by 84%, 64% and 76%, respectively, at 15% w/w sludge addition, while a 10% w/w addition was sufficient to reduce Pb solubility below the U.S . EPA TCLP regulatory limit . The results of the extraction using EDTA solution showed the same trend, resulting in 26%, 36% and 53% reduction in the Pb, Zn and Cd extractable fractions, respectively . Speciation analysis of the treated soils revealed a significant decrease in the mobile fractions of heavy metals, which was attributed to their retention in sewage sludge by adsorption and organic complexation mechanisms . For the assessment of possible phytotoxicity, experiments including growing dwarf beans in the treated soil was carried out . It was found that sewage sludge addition had a positive effect on plant growth . Furthermore, the Pb and Zn uptake of plant leaves and roots was reduced, while Cd uptake was unaffected by the sludge treatment . The results of this study support the hypothesis that municipal sewage sludge is a potential effective stabilizing agent for contaminated soil containing Pb, Zn and Cd.

Can J Microbiol, 2000 Jul, 46(7), 643 - 52
Cometabolic biotransformation of nitrobenzene by 3-nitrophenol degrading Pseudomonas putida 2NP8; Zhao JS et al.; A strain of Pseudomonas putida (2NP8) capable of growing on both 2-nitrophenol and 3-nitrophenol, but not on nitrobenzene (NB), was isolated from municipal activated sludge . 2-Nitrophenol was degraded by this strain with production of nitrite . Degradation of 3-nitrophenol resulted in the formation of ammonia . Cells grown on 2-nitrophenol did not degrade nitrobenzene . A specific nitrobenzene degradation activity was induced by 3-nitrophenol . Ammonia, nitrosobenzene, and hydroxylaminobenzene have been detected as metabolites of nitrobenzene degradation by cells grown in the presence of 3-nitrophenol . These results indicated a NB cometabolism mediated by 3-nitrophenol nitroreductase.

Appl Environ Microbiol, 2000 Jul, 66(7), 2906 - 13
Bioaugmentation of activated sludge by an indigenous 3-chloroaniline-degrading Comamonas testosteroni strain, I2gfp; Boon N et al.; A strain identified as Comamonas testosteroni I2 was isolated from activated sludge and found to be able to mineralize 3-chloroaniline (3-CA) . During the mineralization, a yellow intermediate accumulated temporarily, due to the distal meta-cleavage of chlorocatechol . This strain was tested for its ability to clean wastewater containing 3-CA upon inoculation into activated sludge . To monitor its survival, the strain was chromosomally marked with the gfp gene and designated I2gfp . After inoculation into a lab-scale semicontinuous activated-sludge (SCAS) system, the inoculated strain maintained itself in the sludge for at least 45 days and was present in the sludge flocs . After an initial adaptation period of 6 days, complete degradation of 3-CA was obtained during 2 weeks, while no degradation at all occurred in the noninoculated control reactor . Upon further operation of the SCAS system, only 50% 3-CA removal was observed . Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes revealed a dynamic change in the microbial community structure of the activated sludge . The DGGE patterns of the noninoculated and the inoculated reactors evolved after 7 days to different clusters, which suggests an effect of strain inoculation on the microbial community structure . The results indicate that bioaugmentation, even with a strain originating from that ecosystem and able to effectively grow on a selective substrate, is not permanent and will probably require regular resupplementation.

Curr Microbiol, 2000 Aug, 41(2), 79 - 83
Low-substrate regulated microaerophilic behavior as a stress response of aquatic and soil bacteria; Mazumder R et al.; Low-substrate regulated microaerophilic behavior (LSRMB) was observed in 10-54% of the bacteria isolated from several fresh-water lakes or ponds, subsurface soils, activated sludge, and Antarctic dry valley soils . Five Pseudomonas and two Bacillus type species showed LSRMB . A subsurface Pseudomonas jessenii strain was used as a model to show the metabolic interaction between substrate and oxygen concentrations, cell band movement, and the appearance of unique stress lipids and proteins . When the oxygen in the P . jessenii culture medium was increased from 11% to 100% saturation under atmospheric condition, the concentration of 17:0 cyclopropane fatty acid, a stress indicator, increased five-fold, and four unique proteins were also detected . This stress response occurred only in low-substrate media . It is our hypothesis that LSRMB is a common but under-appreciated trait of many aquatic and soil bacteria.

Curr Opin Biotechnol, 2000 Jun, 11(3), 286 - 9
Field applications of genetically engineered microorganisms for bioremediation processes; Sayler GS et al.; Genetically engineered microorganisms (GEMs) have shown potential for bioremediation applications in soil, groundwater, and activated sludge environments, exhibiting enhanced degradative capabilities encompassing a wide range of chemical contaminants . However, the vast majority of studies pertaining to genetically engineered microbial bioremediation are supported by laboratory-based experimental data . In general, relatively few examples of GEM applications in environmental ecosystems exist . Unfortunately, the only manner in which to fully address the competence of GEMs in bioremediation efforts is through long-term field release studies . It is therefore essential that field studies be performed to acquire the requisite information for determining the overall effectiveness and risks associated with GEM introduction into natural ecosystems.

Appl Biochem Biotechnol, 2000 Spring, 84-86, 1127 - 35
Effect of food:microorganism ratio in activated sludge foam control; Chua H et al.; Foaming is a common operational problem in activated sludge processes that often adversely affects the quality of the treated effluent . Overgrowth of the filamentous Nocardia spp . in the microbial ecosystem was previously identified as the cause of foaming . In the present study, the specific growth rate of Nocardia amarae was found to be much higher than that of nonfilamentous bacteria under food:microorganism (F:M) ratios lower than 0.5 mg of biological oxygen demand (BOD)/(mg of mixed liquor suspended solids {MLSS}.d) . This indicated that filamentous overgrowth may occur in normal activated sludge processes that are continually operated under the usual F:M range of 0.2-0.6 mg of BOD/(mg of MLSS.d) . A novel two-component feast-fast operation (FFO) that capitalized on the sensitivity of filamentous bacteria to F:M ratio was designed to prevent and control foaming problems . The F:M ratio in the "feasting" aeration unit was 0.8 mg of BOD/(mg of MLSS.d) whereas that in the "fasting" aeration unit was 0.2 mg of BOD/(mg of MLSS.d) . The FFO resulted in an overall process F:M ratio that still remained within the normal range, while avoiding prolonged exposure of the activated sludge ecosystem to an F:M ratio below 0.5 mg of BOD/(mg of MLSS.d) . The FFO suppressed the overgrowth of filamentous bacteria without adversely affecting the organic treatment efficiency of the modified process.

Appl Biochem Biotechnol, 2000 Spring, 84-86, 981 - 9
Optimal production of polyhydroxyalkanoates in activated sludge biomass; Ma CK et al.; Polyhydroxyalkanoates (PHAs) have been recognized as good candidates for biodegradable plastics, but their high price compared with conventional plastics has limited their use . In this study, activated sludge microorganisms from a conventional wastewater treatment process were induced, by controlling the carbon:nitrogen (C:N) ratio in the reactor liquor, to accumulate PHAs . In addition, an intermittent nitrogen feeding program was established to optimize the volumetric PHA productivity in a wastewater treatment process . The optimal overall polymer production yield of 0.111 g of polymer/g of carbonaceous substrate consumed was achieved under a C:N ratio of 96:1 by feeding nitrogen in the reactor liquor once every four cycles . At the same time, the amount of excess sludge generated from the wastewater treatment process was reduced by 22.9%.

Appl Biochem Biotechnol, 2000 Spring, 84-86, 487 - 500
Effects of trace levels of copper, chromium, and zinc ions on the performance of activated sludge; Sin SN et al.; The effects of copper, chromium, and zinc ions, at trace levels, on the performance of a simulated activated sludge process were investigated . The results of batch adsorption experiments showed that the adsorption of copper, chromium, and zinc ions followed both the Langmuir and Freundlich isotherms . The presence of trace levels of these three metals not only reduced the adsorption rate of organic matters but also the chemical oxygen demand adsorption capacity (CAC) of the activated sludge . Metal ions competed with the organic substrate for adsorption binding sites on the surfaces of activated sludge bioflocs and reduced the CAC . Studies performed in a sequential batch reactor (SBR) showed that the presence of trace levels of heavy metal ions in wastewater affected the SBR performance to different extents depending on the hydraulic retention time (HRT) . When the reactors were operated at short HRTs of 2.5 d or less, the presence of trace levels of heavy metal ions reduced substantially the CAC of activated sludge, which, in turn, affected significantly the performance of the SBR . However, under longer HRTs (e.g., 5 d), the heavy metal ions in the wastewater reduced the CAC but had no significant effect on the chemical oxygen demand removal efficiency.

Schriftenr Ver Wasser Boden Lufthyg, 2000, 105, 337 - 40
Sewage sludge treatment with lime; Herbst B; The article describes the application of lime as a method for treatment and hygienisation of sewage sludges with lime products such as quicklime, slake lime and dolomitic lime . As a result of the increase in temperature and pH-value during sludge and lime mixing most pathogenic vectors of disease (i.e . bacteria, worms, viruses and parasites) are reduced in concentration and viability to manufacture a safe product for further application on agricultural land.

Schriftenr Ver Wasser Boden Lufthyg, 2000, 105, 297 - 303
Upgrading wastewater treatment plants; Hegemann W; Instead of construction of new wastewater treatment plants upgrading of existing plants may increase capacity or achieve higher efficiency in meeting effluent standards . This paper describes several possibilities of upgrading existing technical wastewater treatment plants, e.g . activated sludge plants, e.g . by precipitation/flocculation processes, increase of biomass concentration, influent balancing, increase of oxygenation capacity with pure oxygen, increase of the capacity of final clarifiers, and pretreatment of industrial effluents.

Schriftenr Ver Wasser Boden Lufthyg, 2000, 105, 289 - 95
Selection criteria for wastewater treatment technologies to protect drinking water; von Sperling M; The protection of water bodies used as sources for drinking water is intimately linked to the adoption of adequate technologies for the treatment of the wastewater generated in the catchment area . The paper presents a general overview of the main technologies used for the treatment of domestic sewage, with a special emphasis on developing countries, and focussing on the main parameters of interest, such as BOD, coliforms and nutrients . A series of tables, figures and charts that can be used for the preliminary selection of treatment technologies is presented . The systems analysed are: stabilisation ponds, activated sludge, trickling filters, anaerobic systems and land disposal . Within each system, the main process variants are covered . Two summary tables are presented, one for quantitative analysis, including easily usable information based on per capita values (US$/cap, Watts/cap, m2 area/cap, m3 sludge/cap), and another for a qualitative comparison among the technologies, based on a one-to-five-star scoring system . The recent trend in tropical countries in the use of UASB (Upflow Anaerobic Sludge Blanket) reactors is also discussed.

Chemosphere, 2000 Sep, 41(5), 757 - 62
4-Nonylphenols and 4-tert-octylphenol in water and fish from rivers flowing into Lake Biwa; Tsuda T et al.; Surveys of 4-nonylphenols (NOs) and 4-tert-octylphenol (OC) were performed for water and fish samples obtained from eight rivers flowing into Lake Biwa once every two months from April 1998 to March 1999 . For water samples, NOs were detected all the year round (0.11-3.08 ng ml(-1)) at high frequency (48/48) in the eight rivers . OC was detected at lower concentrations (ND approximately 0.09 ng ml(-1)) and at lower frequency (23/48) . The concentrations of NOs in the river water always showed minimum values at 5-8 degrees C in winter . It was presumed that the formation of NOs by the biotransformation of nonylphenol polyethoxylates decreased much in the sludge treatment of nonionic surfactants at the low temperature (5-8 degrees C) in winter . Average BCF values of NOs and OC in the six kinds of fish were calculated from the field data . The field BCF values of NOs 15-31 in the six kinds of fish were lower than the laboratory BCF values of 167 in Killifish and 282 in Salmon . For OC, the field BCF values 129-297 for the three kinds of fish were nearly equal to the laboratory BCF value, 261, in Killifish.

Microb Ecol, 2000 Feb, 39(2), 168 - 173
Reduced Growth Yield of Activated Sludge in Organic Protonophore-Containing Batch Culture; Liu Y; The effects of organic protonophores 2,4-dinitrophenol (dNP) and para-nitrophenol (pNP) on the observed growth yield (Y(obs)) was studied using batch cultures of activated sludge microorganisms . A growth yield model was proposed in relation to the ratio of initial protonophore concentration (C(u)) to initial biomass concentration (X(0)) and was verified with experimental data . It was found that Y(obs) decreased with the increase of the C(u)/X(0) ratio, while the specific rate of glucose consumption was increased . Results showed that the C(u)/X(0) ratio could more reasonably reflect the real strength of organic protonophore exerted to activated sludge than using C(u) only . Based on the concept of growth yield, a model describing the uncoupling degree between energy generated via electron transport system and energy used for growth was further developed for protonophore-containing batch culture . It was shown that more than 60% of glucose was consumed through a futile cycle of energy rather than for growth at higher C(u)/X(0) ratios . This research usefully shows that the dissipation of energy via uncoupling biochemical processes can reduce excessive production of activated sludge markedly.

Int J Syst Evol Microbiol, 2000 Jan, 50 Pt 1, 201 - 7
Micropruina glycogenica gen . nov., sp . nov., a new Gram-positive glycogen-accumulating bacterium isolated from activated sludge; Shintani T et al.; A new Gram-positive non-spore-forming bacterium, strain Lg2T, was isolated from an activated sludge reactor showing enhanced biological phosphorus removal activity . The new isolate was a slowly growing organism and was capable of accumulating large amounts of intracellular glycogen from substrate taken up . Both oxidase and catalase were produced . The new isolate contained meso-diaminopimelic acid (DAP) in the cell wall . Complex fatty acid patterns with iso-C14:0, anteiso-C15:0, C16:0, iso-C16:0 and four other minor saturated or unsaturated straight-chain fatty acids were detected . The isolate contained a high genomic G+C content (70.5 mol%) . Phylogenetic analysis based on the 16S rRNA gene sequence placed the isolate in the high G+C Gram-positive group with Microlunatus phosphovorus and Friedmanniella antarctica as the closest relatives (sequence similarities are 93 and 92 %, respectively) . These three organisms shared common features in morphology, but strain Lg2T could be differentiated from the other species by its peptidoglycan type (meso-DAP), fatty acid composition, carbon source utilization profile and G+C content . On the basis of these findings, it is proposed that a new genus and species, Micropruina glycogenica, should be created for the new isolate; the type strain is strain Lg2T (= JCM 10248T).

Comput Biol Med, 2000 Jul, 30(4), 207 - 23
Numerical approach to plug-flow activated sludge reactor kinetics; Muslu Y; In this study, general relationships applicable to a wide variety of microbial-mediated treatment processes are developed using a number of continuous-flow stirred tank reactors-in-series . Simultaneous equations resulting from mass balance on substrate and biomass are solved numerically taking the longitudinal biomass gradient into account . A relationship between substrate and biomass concentrations is developed as a function of hydraulic residence time . Monod kinetics and mathematical models of reactors-in-series are used to represent the actual conditions resulting from varying degrees of axial dispersion and wastewater quality . Dimensionless quantities are used to reduce the number of parameters to be taken into account . Computer techniques are applied to express the results generally . By means of the numerical approach, the variation of the ratio between the hydraulic residence time of a given reactor and that of an equivalent plug-flow tank with the same inlet and outlet conditions is investigated . Results are expressed in the form of graphs to characterize the plug-flow activated sludge systems and to provide a basis of design . Experimental data reported in the literature are also evaluated to demonstrate the cases where the existing classical solution to the problem differs from the actual results obtained from the computer program and the design graphs given.

Mol Gen Genet, 2000 Apr, 263(3), 471 - 82
Phenotypic and molecular characterization of conjugative antibiotic resistance plasmids isolated from bacterial communities of activated sludge; Droge M et al.; In order to isolate antibiotic resistance plasmids from bacterial communities found in activated sludge, derivatives of the 3-chlorobenzoate-degrading strain Pseudomonas sp . B13, tagged with the green fluorescent protein as an identification marker, were used as recipients in filter crosses . Transconjugants were selected on agar plates containing 3-chlorobenzoate as the sole carbon source and the antibiotic tetracycline, streptomycin or spectinomycin, and were recovered at frequencies in the range of 10(-5) to 10(-8) per recipient . A total of 12 distinct plasmids, designated pB1-pB12, was identified . Their sizes ranged between 41 to 69 kb and they conferred various patterns of antibiotic resistance on their hosts . Two of the plasmids, pB10 and pB11, also mediated resistance to inorganic mercury . Seven of the 12 plasmids were identified as broad-host-range plasmids, displaying extremely high transfer frequencies in filter crosses, ranging from 10(-1) to 10(-2) per recipient cell . Ten of the 12 plasmids belonged to the IncP incompatibility group, based on replicon typing using IncP group-specific PCR primers . DNA sequencing of PCR amplification products further revealed that eight of the 12 plasmids belonged to the IncPbeta subgroup, whereas two plasmids were identified as IncPalpha plasmids . Analysis of the IncP-specific PCR products revealed considerable differences among the IncPbeta plasmids at the DNA sequence level . In order to characterize the gene "load" of the IncP plasmids, restriction fragments were cloned and their DNA sequences established . A remarkable diversity of putative proteins encoded by these fragments was identified . Besides transposases and proteins involved in antibiotic resistance, two putative DNA invertases belonging to the Din family, a methyltransferase of a type I restriction/modification system, a superoxide dismutase, parts of a putative efflux system belonging to the RND family, and proteins of unknown function were identified.

J Microbiol Methods, 2000 May, 40(3), 255 - 63
The use of the tetrazolium salt XTT for the estimation of biological activity of activated sludge cultivated under steady-state and transient regimes; Bensaid A et al.; The tetrazolium salt 3'- inverted question mark1-{(phenylamino)-carbonyl}-3, 4-tetrazolium inverted question mark-bis (4-methoxy-6-nitro) benzenesulfonic acid hydrate (XTT) was used as a tool for estimating the activity of the electron transport system (ETS) in activated sludge cultivated under steady-state and transient regimes in chemostat culture . Production of formazan by reduction of XTT depended on the initial concentration of the XTT following a saturation law and was proportional to live cell biomass . Addition of cyanide (KCN) to activated sludge gave an initial 1.5-fold increase in XTT reduction, while addition of 3,5-dichlorophenol (3,5-DCP) reduced this value drastically . At steady-state and transient regimes of an activated sludge chemostat, oxygen uptake rate (OUR) and XTT reduction rate were highly correlated and indicated significant variations depending on the growth conditions.

J Hazard Mater, 2000 Jun 30, 74(3), 197 - 211
Enhanced TCDD degradation by Fenton's reagent preoxidation; Kao CM et al.; The dioxin isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been called the most toxic compound known to man . Because of its poor bioavailability and low biodegradibility, bioremediation technology cannot effectively degrade TCDD when used alone . In this study, chemical pretreatment (partial oxidation) in combination with biodegradation technique was developed to efficiently remediate TCDD-contaminated soils . An oxidizing reagent {Fenton's Reagent (FR)} was applied in a slurry reactor to transform TCDD with a concentration of 96 microg per kg of soil to compounds more amenable to biodegradation . Up to 99% TCDD was transformed after the chemical pretreatment process . The slurry reactor was then converted to a bioreactor for the following biodegradation experiment . The detected TCDD oxidation byproducts including chlorophenols (CPs) and chlorobenzenes (CBs) were transformed in this bioreactor under aerobic conditions . Two other biodegradation experiments were performed in parallel to investigate the biodegradabiliy of TCDD under aerobic and anaerobic conditions without chemical pretreatment . Approximately 53% TCDD was transformed under anaerobic conditions possibly due to the reductive dechlorination process using organic materials contained in the activated sludge as the primary substrates . No TCDD degradation was observed under aerobic conditions . Results show that FR can oxidize TCDD to less-chlorinated and less-toxic byproducts, promoting their bioavailability to microbial communities . The bench-scale results indicate that the two-stage (partial oxidation followed by biodegradation) system has the potential to be developed to remediate TCDD-contaminated soils on-site.

J Appl Microbiol, 2000 May, 88(5), 826 - 35
A fluorescently-labelled r-RNA targeted oligonucleotide probe for the in situ detection of G-bacteria of the genus Amaricoccus in activated sludge; Maszenan A et al.; A fluorescently-labelled r-RNAtargeted oligonucleotide probe specific for members of the genus Amaricoccus, which includes one group of the Gram-negative G-Bacteria seen in activated sludge systems, is described . These organisms, previously 'identified' on their distinctive morphology of cocci in tetrads, have been associated with poor performance of biological nutrient removal (EBNR) plants, by out-competing the polyphosphate accumulating bacteria . Methods of sample preparation for probing activated sludge are detailed, and preliminary surveys of 46 plants, using this probe, show that G-Bacteria belonging to the genus Amaricoccus are seen not only in large numbers in EBNR systems but also in conventional plants . The presence of single cells of this organism was common, emphasizing the dangers of relying on morphology and cell arrangement to identify these bacteria.

Appl Environ Microbiol, 2000 May, 66(5), 2154 - 65
Monitoring precursor 16S rRNAs of Acinetobacter spp . in activated sludge wastewater treatment systems; Oerther DB et al.; Recently, Cangelosi and Brabant used oligonucleotide probes targeting the precursor 16S rRNA of Escherichia coli to demonstrate that the levels of precursor rRNA were more sensitive to changes in growth phase than the levels of total rRNA (G . A . Cangelosi and W . H . Brabant, J . Bacteriol . 179:4457-4463, 1997) . In order to measure changes in the levels of precursor rRNA in activated sludge systems, we designed oligonucleotide probes targeting the 3' region of the precursor 16S rRNA of Acinetobacter spp . We used these probes to monitor changes in the level of precursor 16S rRNA during batch growth of Acinetobacter spp . in Luria-Bertani (LB) medium, filtered wastewater, and in lab- and full-scale wastewater treatment systems . Consistent with the previous reports for E . coli, results obtained with membrane hybridizations and fluorescence in situ hybridizations with Acinetobacter calcoaceticus grown in LB medium showed a more substantial and faster increase in precursor 16S rRNA levels compared to the increase in total 16S rRNA levels during exponential growth . Diluting an overnight culture of A . calcoaceticus grown in LB medium with filtered wastewater resulted in a pattern of precursor 16S rRNA levels that appeared to follow diauxic growth . In addition, fluorescence in situ hybridizations with oligonucleotide probes targeting total 16S rRNA and precursor 16S rRNA showed that individual cells of A . calcoaceticus expressed highly variable levels of precursor 16S rRNA when adapting from LB medium to filtered sewage . Precursor 16S rRNA levels of Acinetobacter spp . transiently increased when activated sludge was mixed with influent wastewater in lab- and full-scale wastewater treatment systems . These results suggest that Acinetobacter spp . experience a change in growth activity within wastewater treatment systems.

Int J Syst Evol Microbiol, 2000 Mar, 50 Pt 2, 703 - 9
'Candidatus Nostocoida limicola', a filamentous bacterium from activated sludge; Blackall LL et al.; Five strains of 'Candidatus Nostocoida limicola' were isolated by micromanipulation from two activated sludge plants . Two (Ben17 and Ben18) were from Sunbury, Victoria, Australia, and three (Ben67, Ver1 and Ver2) were from Verona, Italy . The near complete 16S rDNA sequences were determined for five strains and the phylogenetic location of this important bulking filament in the actinomycete subphylum is reported for the first time . Phylogenetically, the Ben strains formed one group with 99.4% 16S rDNA similarity, and the Ver strains formed another with 99.9% 16S rDNA similarity . The mean similarity between the two groups was 97.4% . By 16S rDNA comparison, the closest relative to all strains was Terrabacter sp . strain DPO1361 (95.0-95.5% identical) . On R2A medium, all strains generally grew as short filaments or clumps of cocci, whereas on glucose sulfide (GS) medium, all grew as irregular twisting filaments comprising Gram-positive and Gram-negative cells, which is close to their in situ morphology . Polyphosphate was stored either as granules (R2A) or throughout the trichomes (GS) . None of the strains could grow without added nitrogen, reduce nitrate to nitrogen gas or grow anaerobically, whereas all could grow at 15-30 degrees C, produce catalase and reduce nitrate to nitrite . All were inactive in the Hugh & Leifson test . This paper describes 'Candidatus Nostocoida limicola'.

Int J Syst Evol Microbiol, 2000 Mar, 50 Pt 2, 593 - 603
Three isolates of novel polyphosphate-accumulating gram-positive cocci, obtained from activated sludge, belong to a new genus, Tetrasphaera gen . nov., and description of two new species, Tetrasphaera japonica sp . nov . and Tetrasphaera australiensis sp . nov; Maszenan AM et al.; Two isolates of Gram-positive cocci (Ben 109T and Ben 110) which could accumulate polyphosphate and were microscopically similar in appearance to so-called 'G-bacteria', appearing as tetrads, were isolated from samples of activated sludge biomass by micromanipulation and grown in axenic culture . On the basis of their phenotypic and chemotaxonomic characters and 16S rDNA sequences, these isolates, together with strain T1-X7T isolated and described previously in Japan, belong to a new genus . These isolates are phylogenetically different from Tessaracoccus bendigoensis, Friedmanniella spumicola and Friedmanniella capsulata, Gram-positive cocci isolated previously in this laboratory . They are characterized by type A1 gamma peptidoglycan, with meso-diaminopimelic acid as the diagnostic diamino acid . The main cellular fatty acid of Ben 109T, Ben 110 and T1-X7T is 14-methylpentadecanoic acid (i-C16:0) . The major menaquinones of Ben 109T are MK-8(H4), with MK-8(H2) and MK-8 in trace amounts . In Ben 110 MK-8(H4) and MK-6(H4) are the major menaquinones, while T1-X7T has MK-8(H4), MK-7(H4) and MK-6(H4) as its menaquinones . All three contain phosphatidylinositol, phosphatidylglycerol and diphosphatidylglycerol as their polar lipids . These properties, together with 16S rDNA sequence data, suggest that they all belong to a single new genus for which the name Tetrasphaera gen . nov . is proposed . However, the lipid, cellular fatty acid profiles and DNA-DNA similarity data suggest that Ben 109T and Ben 110 are sufficiently different from T1-X7T to represent a different species of the genus Tetrasphaera . Strain T1-X7T represents the type species Tetrasphaera japonica sp . nov . of this new genus, and strains Ben 109T and Ben 110 belong to the other species, Tetrasphaera australiensis sp . nov.

Microb Ecol, 1999 Nov, 38(4), 348 - 357
Quantitation of the Population Size and Metabolic Activity of a Resin Acid Degrading Bacterium in Activated Sludge Using Slot-Blot Hybridization to Measure the rRNA:rDNA Ratio; Muttray AF et al.; The 16S rRNA:rDNA ratio is a useful parameter for measuring metabolic activity of a selected member of a complex microbial community, as in pulp effluent activated sludge systems . The RNA:DNA ratio of Sphingomonas sp . DhA-33, previously isolated from a sequencing batch reactor treating pulp mill effluent, is positively correlated with its growth rate (micro) under steady-state conditions . DhA-33 was grown in a chemostat with growth rates ranging from 0.04 to 0.15 cell divisions per hour . DhA-33 was also able to degrade dehydroabietic acid in bleached kraft mill effluent (BKME) plus mineral medium in batch culture . Slot-blot hybridization with radioactively labeled species-specific oligonucleotide probes for 16S rRNA and 16S rDNA was used to measure rRNA, rDNA, and the RNA:DNA ratio of this strain when in a mixed sludge community . An increase in DhA-33 rDNA indicated growth of DhA-33 within the community . The RNA:DNA ratio of DhA-33 increased sharply during exponential growth and declined as cells entered stationary phase . The RNA:DNA ratio decreased earlier and faster in DhA- 33/sludge co-cultures than in DhA-33 pure cultures, presumably due to an earlier depletion of nutrients . The species-specific quantification of the RNA:DNA ratio makes it possible to estimate the metabolic activity of selected members of a microbial community in situ.

Microbiology, 2000 Mar, 146 ( Pt 3), 701 - 7
Yeast spores seem to be involved in biological phosphate removal: a microscopic in situ case study; Melasniemi H et al.; The principal polyphosphate-accumulating organism (PAO) in a biological-phosphate-removal activated-sludge process was assessed microscopically . The organism was recognized by its distinct morphotype most easily after polyphosphate staining . The PAO occurred in large, homogeneous clusters . The cells of the PAO were the biggest cells abounding in the sludge--clearly bigger than average sludge bacteria . Typical of the principal PAO was a variation of cell size, even in fresh sludge . In acetate minimal medium containing ampicillin, the original principal PAO clusters were converted to clusters of clearly larger, polyphosphate-containing, vegetative yeast-like cells . Cycloheximide addition inhibited this and caused flock disintegration, disappearance of the principal PAO clusters and growth of free bacteria . The cell wall of the principal PAO was not of the usual bacterial character . It showed anomalous Gram staining, stained for chitin (not found in bacteria) and bound concanavalin A, like cell walls of many yeasts . In addition, the PAO cell wall was resistant to lysozyme, but sensitive to an enzyme mixture that lyses yeast cell walls . It was concluded that the principal PAO cells in the studied sludge were clustered spores of a yeast.

Biochemistry (Mosc), 2000 Mar, 65(3), 341 - 8
Microbial selection of polyphosphate-accumulating bacteria in activated sludge wastewater treatment processes for enhanced biological phosphate removal; Mino T; Activated sludge processes with alternating anaerobic and aerobic conditions (the anaerobic-aerobic process) have been successfully used for enhanced biological phosphate removal (EBPR) from wastewater . It is known that polyphosphate-accumulating bacteria (PAB) play an essential role for EBPR in the anaerobic-aerobic process . The present paper reviews limited information available on the metabolism and the microbial community structure of EBPR, highlighting the microbial ecological selection of PAB in EBPR processes . Exposure of microorganisms to alternate carbon-rich anaerobic environments and carbon-poor aerobic environments in the anaerobic-aerobic process induces the key metabolic characteristics of PAB, which include organic substrate uptake followed by its conversion to stored polyhydroxyalkanoate (PHA) and hydrolysis of intracellular polyphosphate accompanied by subsequent Pi release under anaerobic conditions . Intracellular glycogen is assumed to function as a regulator of the redox balance in the cell . Storage of glycogen is a key strategy for PAB to maintain the redox balance in the anaerobic uptake of various organic substrates, and hence to win in the microbial selection . Acinetobacter spp., Microlunatus phosphovorus, Lampropedia spp., and the Rhodocyclus group have been reported as candidates of PAB . PAB may not be composed of a few limited genospecies, but involve phylogenetically and taxonomically diverse groups of bacteria . To define microbial community structure of EBPR processes, it is needed to look more closely into the occurrence and behavior of each species of PAB in various EBPR processes mainly by molecular methods because many of PAB seem to be impossible to culture.

Lett Appl Microbiol, 2000 Jan, 30(1), 28 - 32
Detection of GroEL in activated sludge: a model for detection of system stress; Duncan AJ et al.; GroEL is a ubiquitous constitutively synthesized protein that is also stress inducible . Activated sludge, which is a standard biological process used in wastewater treatment systems, is made up of a diverse microbial consortium . The synthesis of GroEL in activated sludge was significantly induced after heat (42 degrees C) shock . The increased level of GroEL expression was shown to be due to de novo protein synthesis . We have demonstrated a method which shows that stress proteins can be detected in activated sludge, and propose their use as specific indicators of system stress.

Biosens Bioelectron, 2000 Feb, 14(12), 883 - 93
Immobilised activated sludge based biosensor for biochemical oxygen demand measurement; Liu J et al.; A biochemical oxygen demand (BOD) sensor, based on an immobilised mixed culture of microorganisms in combination with a dissolved oxygen electrode, has been developed for the purpose of on-line monitoring of the biological treatment process for waste and wastewater . The sensor was designed for easy replacement of the biomembrane, thereby making it suitable for short-term use . The drawbacks of activated sludge based sensor, such as short sensor lifetime, were thereby circumvented . The sensor BOD measurements were carried out in the kinetic mode using a flow injection system, resulting in 25 s for one measurement followed by 4-8 min recovery time . Based on the results of normalised sensor responses, the OECD synthetic wastewater was considered to be a more suitable calibration solution in comparison with the GGA solution . Good agreement was achieved between the results of the sensor BOD measurement and those obtained from BOD5 analysis of a wastewater sample from a food-processing factory . Reproducibility of responses using one sensor was below +/- 5.6%, standard deviation . Reproducibility of responses using different sensors was within acceptable bias limits, viz . +/- 15% standard deviation.

J Hazard Mater, 2000 Apr 3, 73(2), 129 - 42
Oxygen uptake rate inhibition with PACT sludge; Sher MI et al.; Oxygen uptake rate (OUR) experiments were performed with sludge from six laboratory-scale, continuously fed, activated sludge and PACT reactors (sludge ages of 4-, 8-, and 12-days) to evaluate the sludge's resistance to inhibitory compounds . Three inhibitory compounds with varied ability to sorb on activated carbon were tested: 3,5-dichlorophenol (3,5-DCP, strongly adsorbed), phenol (moderately adsorbed), and zinc (poorly adsorbed) . The inhibitory compound concentration that reduced the unacclimated sludge's specific oxygen uptake 50% from its maximum rate was determined (IC(50)) . For the organic compounds, PACT sludge resisted acute inhibition better for all sludge ages; sorption studies indicate that phenol sorbed onto the PACT sludge could account for the IC(50) difference at the higher sludge ages . With 3,5-DCP, the 4- and 8-day-old PACT and activated sludge solids sorbed similar amounts of 3,5-DCP at concentrations near the IC(50) values, yet the PACT sludge exhibited higher IC(50) values; biomass differences may have accounted for the improved resistance to inhibition . With the poorly adsorbed zinc, no difference in IC(50) or sorption was noted with the 4-day-old sludge . For the 12-day-old sludge, the PACT sludge was much more resistant to zinc exposure, with changes in the biomass rather than sorption on carbon the apparent reason.

Appl Environ Microbiol, 2000 Mar, 66(3), 1175 - 82
Identification of polyphosphate-accumulating organisms and design of 16S rRNA-directed probes for their detection and quantitation; Crocetti GR et al.; Laboratory-scale sequencing batch reactors (SBRs) as models for activated sludge processes were used to study enhanced biological phosphorus removal (EBPR) from wastewater . Enrichment for polyphosphate-accumulating organisms (PAOs) was achieved essentially by increasing the phosphorus concentration in the influent to the SBRs . Fluorescence in situ hybridization (FISH) using domain-, division-, and subdivision-level probes was used to assess the proportions of microorganisms in the sludges . The A sludge, a high-performance P-removing sludge containing 15.1% P in the biomass, was comprised of large clusters of polyphosphate-containing coccobacilli . By FISH, >80% of the A sludge bacteria were beta-2 Proteobacteria arranged in clusters of coccobacilli, strongly suggesting that this group contains a PAO responsible for EBPR . The second dominant group in the A sludge was the Actinobacteria . Clone libraries of PCR-amplified bacterial 16S rRNA genes from three high-performance P-removing sludges were prepared, and clones belonging to the beta-2 Proteobacteria were fully sequenced . A distinctive group of clones (sharing >/=98% sequence identity) related to Rhodocyclus spp . (94 to 97% identity) and Propionibacter pelophilus (95 to 96% identity) was identified as the most likely candidate PAOs . Three probes specific for the highly related candidate PAO group were designed from the sequence data . All three probes specifically bound to the morphologically distinctive clusters of PAOs in the A sludge, exactly coinciding with the beta-2 Proteobacteria probe . Sequential FISH and polyphosphate staining of EBPR sludges clearly demonstrated that PAO probe-binding cells contained polyphosphate . Subsequent PAO probe analyses of a number of sludges with various P removal capacities indicated a strong positive correlation between P removal from the wastewater as determined by sludge P content and number of PAO probe-binding cells . We conclude therefore that an important group of PAOs in EBPR sludges are bacteria closely related to Rhodocyclus and Propionibacter.

Appl Environ Microbiol, 2000 Mar, 66(3), 1158 - 66
Quantitative use of fluorescent in situ hybridization to examine relationships between mycolic acid-containing actinomycetes and foaming in activated sludge plants; Davenport RJ et al.; The formation of viscous foams on aeration basins and secondary clarifiers of activated sludge plants is a common and widespread problem . Foam formation is often attributed to the presence of mycolic acid-containing actinomycetes (mycolata) . In order to examine the relationship between the number of mycolata and foam, we developed a group-specific probe targeting the 16S rRNA of the mycolata, a protocol to permeabilize mycolata, and a statistically robust quantification method . Statistical analyses showed that a lipase-based permeabilization method was quantitatively superior to previously described methods (P << 0.05) . When mixed liquor and foam samples were examined, most of the mycolata present were rods or cocci, although filamentous mycolata were also observed . A nested analysis of variance showed that virtually all of the measured variance occurred between fields of view and not between samples . On this basis we determined that as few as five fields of view could be used to give a statistically meaningful sample . Quantitative fluorescent in situ hybridization (FISH) was used to examine the relationship between foaming and the concentration of mycolata in a 20-m(3) completely mixed activated sludge plant . Foaming occurred when the number of mycolata exceeded a certain threshold value . Baffling of the plant affected foaming without affecting the number of mycolata . We tentatively estimated that the threshold foaming concentration of mycolata was about 2 x 10(6) cells ml(-1) or 4 x 10(12) cells m(-2) . We concluded that quantitative use of FISH is feasible and that quantification is a prerequisite for rational investigation of foaming in activated sludge.

Chemosphere, 1999 Dec, 39(15), 2681 - 92
Sub-lethal effects of heavy metals on activated sludge microorganisms; Chua H et al.; The effects of heavy metals, at sub-lethal concentrations, on activated sludge microbial ecosystem were investigated . Adsorption capacity and rate of copper, chromium, lead and zinc on microbial flocs were much faster than that of organic matters . Metals affected not only the adsorption rate of organic matters but also the COD adsorption capacity of the activated sludge . Effects of heavy metals, on wastewater treatment performance of a sequencing batch reactor were also studied . Metal-laden wastewater at sub-lethal levels affected the performance to different extents, depending on the hydraulic retention time . Metal ions acted as a strong competitor against the organic compounds for active sites on the bioflocs instead of acting as a toxic microbial inhibitor, thus hampering organic adsorption and affecting the COD removal efficiency under shorter HRTs.

Biotechnol Bioeng, 2000 Feb 20, 67(4), 379 - 89
Stoichiometry and kinetics of poly-beta-hydroxybutyrate metabolism in aerobic, slow growing, activated sludge cultures; Beun JJ et al.; This paper discusses the poly-beta-hydroxybutyrate (PHB) metabolism in aerobic, slow growing, activated sludge cultures, based on experimental data and on a metabolic model . The dynamic conditions which occur in activated sludge processes were simulated in a 2-L sequencing batch reactor (SBR) by subjecting a mixed microbial population to successive periods of external substrate availability (feast period) and no external substrate availability (famine period) . Under these conditions intracellular storage and consumption of PHB was observed . It appeared that in the feast period, 66% to almost 100% of the substrate consumed is used for storage of PHB, the remainder is used for growth and maintenance processes . Furthermore, it appeared that at high sludge retention time (SRT) the growth rate in the feast and famine periods was the same . With decreasing SRT the growth rate in the feast period increased relative to the growth rate in the famine period . Acetate consumption and PHB production in the feast period both proceeded with a zero-order rate in acetate and PHB concentration respectively . PHB consumption in the famine period could best be described kinetically with a nth-order degradation equation in PHB concentration . The obtained results are discussed in the context of the general activated sludge models .

Syst Appl Microbiol, 1999 Sep, 22(3), 454 - 65
Enrichment, phylogenetic analysis and detection of a bacterium that performs enhanced biological phosphate removal in activated sludge; Hesselmann RP et al.; Activated sludge communities which performed enhanced biological phosphate removal (EBPR) were phylogenetically analyzed by 16S rRNA-targeted molecular methods . Two anaerobic-aerobic sequencing batch reactors were operated with two different carbon sources (acetate vs . a complex mixture) for three years and showed anaerobic-aerobic cycles of polyhydroxybutyrate- (PHB) and phosphate-accumulation characteristic for EBPR-systems . In situ hybridization showed that the reactor fed with the acetate medium was dominated by bacteria phylogenetically related to the Rhodocyclus-group within the beta-Proteobacteria (81% of DAPI-stained cells) . The reactor with the complex medium was also predominated by this phylogenetic group albeit at a lesser extent (23% of DAPI-stained cells) . More detailed taxonomic information on the dominant bacteria in the acetate-reactor was obtained by constructing clone libraries of 16S rDNA fragments . Two different types of Rhodocyclus-like clones (R1 and R6) were retrieved . Type-specific in situ hybridization and direct rRNA-sequencing revealed that R6 was the type of the dominant bacteria . Staining of intracellular polyphosphate- and PHB-granules confirmed that the R6-type bacterium accumulates PHB and polyphosphate just as predicted by the metabolic models for EBPR . High similarities to 16S rDNA fragments from other EBPR-sludges suggest that R6-type organisms were present and may play an important role in EBPR in general . Although the R6-type bacterium is closely related to the genus Rhodocyclus, it did not grow phototrophically . Therefore, we propose a provisional new genus and species Candidatus Accumulibacter phosphatis.

Artif Cells Blood Substit Immobil Biotechnol, 1999 Sep-Nov, 27(5-6), 423 - 8
Pilot scale study on retrofitting conventional activated sludge plant for biological nutrient removal; Chiang WW et al.; Eutrophication of receiving waters due to the discharge of nitrogen and phosphorus through the wastewater effluent has received much interest in recent years . Numerous techniques have been proposed and aimed at retrofitting the existing conventional activated sludge process for nutrient removal . A pilot-scale research program was conducted to evaluate the effectiveness of a biological nutrient process for this purpose . The results indicated that creating an anoxic/anaerobic zone before aeration basin significantly enhances total phosphorus (TP) and total nitrogen (TN) removal . Without internal cycle, about 80 percent TP and TN removal were respectively achieved under their optimal conditions . However, adverse trends for phosphorus and nitrogen removal were observed when the ratio of return sludge to the influent was varied in the range between 0.5 and 3.0 . The total phosphorus removal decreased as the concentration of BOD5 in the mixture of influent and return sludge decreased . Improved sludge settling properties and reduced foaming problems were also observed during the pilot plant operation . Based upon experimental results, the strategies to modify an existing conventional activated sludge plant into a biological nutrient removal (BNR) system are discussed.

Microb Ecol, 1999 Oct, 38(3), 201 - 214
Localization and Identification of Populations of Phosphatase-Active Bacterial Cells Associated with Activated Sludge Flocs; Van Ommen Kloeke F et al.; Abstract The majority of phosphatase (PO(4)ase) activity detected in fresh aerobic activated sludge from a municipal wastewater treatment plant was associated with suspended floc material . PO(4)ase activity appeared to be localized in discrete bacteria-containing areas of the floc matrix based on the distribution of nucleic acid-stained cells and precipitated fluorescent crystals produced as a result of reaction of the enzyme(s) with the artificial substrate ELFtrade mark-PO(4) . Of the total floc-associated bacterial cells that stained positive with the nucleic acid-binding fluorochrome acridine orange (AO), 8.8 +/- 1.2% displayed PO(4)ase activity based on the proximity of AO-stained cells to precipitated ELF crystals . Using a 16S rRNA oligonucleotide probe specific for the cytophaga-flavobacteria group, it was determined that 17-20% of the floc-associated bacteria that probed positive also displayed PO(4)ase activity . Furthermore, 35-45% of the ELF fluorescence was associated with bacterial cells that probed positive for the cytophaga-flavobacteria group . The results suggest that the cytophaga-flavobacteria, as a group, is important in mediating the liberation of inorganic orthophosphate (P(i)) from phosphomonoesters of detrital organic phosphate (organic-P) in the aerobic activated sludge process of wastewater treatment.http://link.springer-ny.com/link/service/journals/00248/bibs/38n3p201.html</hea

Chemosphere, 1999 Dec, 39(13), 2313 - 23
Biodegradation in laboratory activated sludge plants and aquatic toxicity of herbicides; Nitschke L et al.; The biodegradation and the aquatic toxicity of four herbicides (isoproturon, terbuthylazine, mecoprop, metamitron) were investigated . Laboratory activated sludge plants were used for biodegradation experiments . The biodegradation of mecoprop reached nearly 100%, the other herbicides were not eliminated by biodegradation . The acute Daphnia magna 24-h assay, the algal 72-h inhibition test, and the recently developed lemna growth inhibition 7-d test were applied to evaluate the biological effects of herbicides as original substances . EC 50 and EC 10 values were determined . Algal and lemna test show that isoproturon and terbuthylazine are both much more toxic than mecoprop and metamitron . Daphnids are generally less sensitive against herbicides than plants . Biodegradation and toxicity test were coupled for mecoprop to assess biological long-term effects of possible biodegradation products of this herbicide . The effluents of the laboratory activated sludge units were used in toxicity tests (Daphnia magna 21-d reproduction test, lemna growth inhibition 7-d test) . No inhibiting effect on the tested organisms was observed.

Appl Microbiol Biotechnol, 1999 Nov, 52(5), 698 - 703
Screening and characterization of bioflocculant produced by isolated Klebsiella sp; Dermlim W et al.; Sixteen strains of polymer-producing bacteria were isolated from the activated sludge samples taken from two seafood processing plants in Southern Thailand . Their culture broths possessed the ability to flocculate kaolin suspension in the presence of 1% CaCl2 . Based on the flocculating activity, the strain S11 was selected and identified to be a Klebsiella sp . using the partial 16S rRNA sequencing method . The growth of the isolated Klebsiella sp . was maximal (1.026 g l-1 dry cell mass) after 1 day cultivation while the highest polymer yield (0.973 g l-1) was achieved after 5 days cultivation . The flocculating activity of the culture broth, however, was highest after 2 days cultivation . The polymer was identified to be an acidic polysaccharide containing neutral sugar and uronic acid as its major and minor components, respectively . Results on the properties of the partially purified polysaccharide from Klebsiella sp . S11 revealed that it consisted of galactose, glucose and mannose in an approximate ratio of 5:2:1 . It was soluble in acidic or basic solutions but not in organic solvents . Its molecular mass was greater than 2 x 10(6) Da . Infrared spectra showed the presence of hydroxyl, carboxyl and methoxyl groups in its molecules . Differential scanning calorimetry of the polysaccharide indicated the crystalline melting point (Tm) at 314 degrees C . The optimum dosage of polysaccharide to give the highest flocculating activity was 15 mg l-1 in the presence of 1% CaCl2.

Appl Microbiol Biotechnol, 1999 Nov, 52(5), 647 - 51
A kinetic model incorporating energy spilling for substrate removal in substrate-sufficient batch culture of activated sludge; Liu Y et al.; Batch assays are currently used to study the kinetic behavior of microbial growth . However, it has been shown that the outcome of batch experiments is greatly influenced by the initial ratio of substrate concentration (S(o)) to biomass concentration (Xo) . Substrate-sufficient batch culture is known to have mechanisms of spilling energy that lead to significant nongrowth-associated substrate consumption, and the Monod equation is no longer appropriate . By incorporating substrate consumption associated with energy spilling into the balance of the substrate oxidation reaction, a kinetic model for the observed specific substrate consumption rate was developed for substrate-sufficient batch culture of activated sludge, and was further verified by experimental data . It was demonstrated that the specific substrate consumption rate increased with the increase of the S(o)/Xo ratio, and the majority of substrate was consumed through energy spilling at high S(o)/Xo ratios . It appears that the S(o)/Xo ratio is a key parameter in regulating metabolic pathways of microorganisms.

ISA Trans, 1999, 38(3), 231 - 41
Nonlinear control of an activated sludge aeration process: use of fuzzy techniques for tuning PID controllers; Rodrigo MA et al.; In this paper, several tuning algorithms, specifically ITAE, IMC and Cohen and Coon, were applied in order to tune an activated sludge aeration PID controller . Performance results of these controllers were compared by simulation with those obtained by using a nonlinear fuzzy PID controller . In order to design this controller, a trial and error procedure was used to determine, as a function of error at current time and at a previous time, sets of parameters (including controller gain, integral time and derivative time) which achieve satisfactory response of a PID controller actuating over the aeration process . Once these sets of data were obtained, neural networks were used to obtain fuzzy membership functions and fuzzy rules of the fuzzy PID controller.

Int J Syst Bacteriol, 1999 Oct, 49 Pt 4, 1667 - 80
Friedmanniella spumicola sp . nov . and Friedmanniella capsulata sp . nov . from activated sludge foam: gram-positive cocci that grow in aggregates of repeating groups of cocci; Maszenan AM et al.; Two Gram-positive, non-motile, non-spore-forming, strictly aerobic, pigmented cocci, strains Ben 107T and Ben 108T, growing in aggregates were isolated from activated sludge samples by micromanipulation . Both possessed the rare type A3 gamma' peptidoglycan . Major menaquinones of strain Ben 107T were MK-9(H4) and MK-7(H2), and the main cellular fatty acid was 12-methyltetradecanoic acid (ai-C15:0) . In strain Ben 108T, MK-9(H4), MK-9(H2) and MK-7(H4) were the menaquinones and again the main fatty acid was 12-methyltetradecanoic acid (ai-C15:0) . Polar lipids in both strains consisted of phosphatidyl inositol, phosphatidyl glycerol and diphosphatidyl glycerol with two other unidentified glycolipids and phospholipids also present in both . These data, together with the 16S rDNA sequence data, suggest that strain Ben 107T belongs to the genus Friedmanniella which presently includes a single recently described species, Friedmanniella antarctica . Although the taxonomic status of strain Ben 108T is far less certain, on the basis of its 16S rRNA sequence it is also adjudged to be best placed in the genus Friedmanniella . The chemotaxonomic characteristics and DNA-DNA hybridization data support the view that Ben 107T and Ben 108T are novel species of the genus Friedmanniella . Hence, it is proposed that strain Ben 107T (= ACM 5121T) is named as Friedmanniella spumicola sp . nov . and strain Ben 108T (= ACM 5120T) as Friedmanniella capsulata sp . nov.

J Microbiol Methods, 1999 Oct, 38(1-2), 25 - 31
Novel method for screening bacterial colonies for phosphatase activity; van Ommen Kloeke F et al.; Current methods for screening large numbers of bacterial colonies for phosphatase activity, rely heavily on the use of colorimetric assays . While such methods have been applied extensively in the laboratory, they are not without their drawbacks . We here describe a precipitating fluorescent probe that can be used to screen phosphatase activity in bacterial colonies . This probe can be incorporated directly into agar plates used to culture the organisms of interest . The approach offers several advantages over current methodologies including the ability to monitor the development of phosphatase activity with colony development, and the ability to distinguish between activity arising from cell-bound and cell-free enzyme . This enzyme probe was successfully used to detect and isolate phosphatase-producing bacteria from activated sludge.

Chemosphere, 1999 Oct, 39(10), 1679 - 88
Advanced oxidation of a pulp mill bleaching wastewater; Yeber MC et al.; The degradation, by several advanced oxidation reactions, of a pulp mill ECF bleaching effluent, was studied . The initial biodegradability of the organic matter present in the effluent, estimated as the BOD5/COD, was low (0.3) . When the effluent was submitted to ozonation and to five different advanced oxidation systems (O3/UV, O3/UV/ZnO, O3/UV/TiO2, O2/UV/ZnO, O2/UV/TiO2), the biodegradability increase significantly . After five minutes of reaction, the O3/UV system appears as the most efficient in to transform the organic matter to more biodegradable forms . A similar effect was observed when the effluent was submitted to an activated sludge treatment . The COD, TOC and toxicity reduction correlated well with the biodegradability enhancement after AOPs treatments.

Appl Microbiol Biotechnol, 1999 Aug, 52(2), 261 - 6
Degradation of 2,4,5-trichlorophenol and 2,3,5,6-tetrachlorophenol by combining pulse electric discharge with bioremediation; Chauhan S et al.; Degradation of 2,4,5-trichlorophenol (2,4,5-TCP) and 2,3,5,6-tetrachlorophenol (TeCP) was studied using a two-stage approach that utilized efficient pulse electric discharge (PED) followed by biological degradation with a consortium from acclimated return activated sludge . The chlorinated phenols were treated in the PED reactor as an aerosol at a voltage of 55-60 kV, a frequency of 385 Hz, a current of 50-60, and with a 200-ns pulse . As determined by gas chromatography and mass spectrometry (GC/MS), the first stage converted 500 ppm 2,4,5-TCP to 163 ppm 2,4,5-TCP and dimethyldecene, dichloronaphthalenol, octyl acetate, and silyl esters . The total carbon content of 2,4,5-TCP after PED treatment was determined to be 228 +/- 35 ppm . The remaining 2,4,5-TCP and the products formed were then mineralized by the acclimated activated sludge in shake flasks; the initial rate of degradation of 2,4,5-TCP was calculated to be 5 nmol min-1 mg protein-1 at 163 ppm initial concentration (three orders of magnitude higher than the only rate found in the literature) . By combining the two techniques, a synergistic effect (2.3-fold increase in the concentration of 2,4,5-TCP degraded and 3.3-fold increase in total carbon degraded) was observed, in that bacteria without any treatment degraded a maximum of 70 ppm, 2,4,5-TCP but after PED treatment 163 ppm 2,4,5-TCP was degraded . TeCP was also mineralized by the acclimated activated sludge after treatment with PED . This two-stage approach was also evaluated using a continuous 1-l fluidized-bed reactor.

Chemosphere, 1999 Oct, 39(9), 1421 - 32
Monitoring the toxicity of phenolic chemicals to activated sludge using a novel optical scanning respirometer; Chan CM et al.; This paper reports the development of optical scanning respirometer for determining the toxicity of chemicals to activated sludge . The respirometer is used to measure the dissolved oxygen concentration by monitoring the luminescence intensity of ruthenium dye immobilized in a polymer film in contact with the wastewater sample . The intensity is related to the extent of oxygen quenching of luminescence . The toxicity of chemicals can be evaluated by measuring the inhibition on respiration rate of microorganism using the scanning respirometer . The IC50 values (concentration of a chemical that exhibits 50% respiration inhibition) of various phenolic chemicals in activated sludge were determined . The performance of this method is compared with other toxicity methods . The experimental results indicate that the reproducibility and sensitivity of this respirometer are reasonably good.

Appl Environ Microbiol, 1999 Sep, 65(9), 4077 - 84
Identification of some of the major groups of bacteria in efficient and nonefficient biological phosphorus removal activated sludge systems; Bond PL et al.; To investigate the bacteria that are important to phosphorus (P) removal in activated sludge, microbial populations were analyzed during the operation of a laboratory-scale reactor with various P removal performances . The bacterial population structure, analyzed by fluorescence in situ hybridization (FISH) with oligonucleotides probes complementary to regions of the 16S and 23S rRNAs, was associated with the P removal performance of the reactor . At one stage of the reactor operation, chemical characterization revealed that extremely poor P removal was occurring . However, like in typical P-removing sludges, complete anaerobic uptake of the carbon substrate occurred . Bacteria inhibiting P removal overwhelmed the reactor, and according to FISH, bacteria of the beta subclass of the class Proteobacteria other than beta-1 or beta-2 were dominant in the sludge (58% of the population) . Changes made to the operation of the reactor led to the development of a biomass population with an extremely good P removal capacity . The biochemical transformations observed in this sludge were characteristic of typical P-removing activated sludge . The microbial population analysis of the P-removing sludge indicated that bacteria of the beta-2 subclass of the class Proteobacteria and actinobacteria were dominant (55 and 35%, respectively), therefore implicating bacteria from these groups in high-performance P removal . The changes in operation that led to the improved performance of the reactor included allowing the pH to rise during the anaerobic period, which promoted anaerobic phosphate release and possibly caused selection against non-phosphate-removing bacteria.

Appl Environ Microbiol, 1999 Sep, 65(9), 3920 - 8
Glucose metabolism and kinetics of phosphorus removal by the fermentative bacterium Microlunatus phosphovorus; Santos MM et al.; Phosphorus and carbon metabolism in Microlunatus phosphovorus was investigated by using a batch reactor to study the kinetics of uptake and release of extracellular compounds, in combination with (31)P and (13)C nuclear magnetic resonance (NMR) to characterize intracellular pools and to trace the fate of carbon substrates through the anaerobic and aerobic cycles . The organism was subjected to repetitive anaerobic and aerobic cycles to induce phosphorus release and uptake in a sequential batch reactor; an ultrafiltration membrane module was required since cell suspensions did not sediment . M . phosphovorus fermented glucose to acetate via an Embden-Meyerhof pathway but was unable to grow under anaerobic conditions . A remarkable time shift was observed between the uptake of glucose and excretion of acetate, resulting in an intracellular accumulation of acetate . The acetate produced was oxidized in the subsequent aerobic stage . Very high phosphorus release and uptake rates were measured, 3.34 mmol g of cell(-1) h(-1) and 1.56 mmol g of cell(-1) h(-1), respectively, values only comparable with those determined in activated sludge . In the aerobic period, growth was strictly dependent on the availability of external phosphate . Natural abundance (13)C NMR showed the presence of reserves of glutamate and trehalose in cell suspensions . Unexpectedly, {1-(13)C}glucose was not significantly channeled to the synthesis of internal reserves in the anaerobic phase, and acetate was not during the aerobic stage, although the glutamate pool became labeled via the exchange with intermediates of the tricarboxylic acid cycle at the level of glutamate dehydrogenase . The intracellular pool of glutamate increased under anaerobic conditions and decreased during the aerobic period . The contribution of M . phosphovorus for phosphorus removal in wastewater treatment plants is discussed on the basis of the metabolic features disclosed by this study.

Can J Microbiol, 1999 May, 45(5), 427 - 32
Microbial degradation of nitrobenzene and mono-nitrophenol by bacteria enriched from municipal activated sludge; Zhao JS et al.; Using a mixture of three mono nitrophenols as sole carbon, nitrogen and energy sources, mixed cultures were enriched from municipal activated sludge to degrade both nitrophenols and nitrobenzene . Bacterial growth and degradation rate could be increased by supplementing the medium with 0.1% YE . Microorganisms were isolated from the nitrophenols enrichment, and they were identified as strains of Comamonas testosteroni and Acidovorax delafieldii . These strains showed broad degradation ability toward nitrophenols and nitrobenzene.

Chemosphere, 1999 Aug, 39(4), 611 - 25
Studies of the behaviour and fate of the polymer-additives octadecyl-3-(3.5-di-t-butyl-4-hydroxyphenyl)propionate and tri-(2.4-di-t-butylphenyl)phosphite in the environment; Fischer K et al.; In order to evaluate the environmental risk potential of the polymer-additives octadecyl-3-(3.5-di-t-butyl-4-hydroxyphenyl)propionate (additive 1) and tri-(2.4-di-t-butylphenyl)phosphite (additive 2) we have studied the degradation of the 14C-labelled single components and their release from a polypropylene matrix in abiotic and biotic test systems as well as their transport behaviour in soil . The biotic degradation in waste compost, activated sludge and in soil was studied . In order to conduct release tests, waste disposal material were used as well . The abiotic degradation was effectuated by photooxidation at a catalytic surface . The highest mineralisation rates were obtained by photooxidative degradation of the two test substances . The maximum content of bounded residues was found for additive 1 in soil and for additive 2 in waste compost . In the extracts of soil and compost, the principal metabolites could be identified in the case of additive 1 as 7.9-di-t-butyl-1-oxaspiro{4.5}deca-6.9-dien-2.8-dion and in activated sludge as the methyl ester of 3-(3.5-di-t-butyl-4-hydroxyphenyl) propionic acid . Additive 2 metabolised in all degradation tests nearly completely under formation of two products . The main component was identified as tri-(2.4-di-t-butylphenyl)phosphate . Both polymer-additives were eluated from the chosen soil types . The transport behaviour of additive 1 was independent from the soil type . In all test matrices additive 1 as well as additive 2 were released from polypropylene . Because the amounts of additive 1 and 2 absorbed onto soil particles were taken into account, the highest liberation rates were found in the soil test.

Appl Microbiol Biotechnol, 1999 Jun, 51(6), 883 - 90
Towards a reduction in excess sludge production in activated sludge processes: biomass physicochemical treatment and biodegradation; Rocher M et al.; To decrease activated sludge production, microbial cell lysis can be amplified to enhance cryptic growth (biomass growth on lysates) . Cell breakage techniques (thermal, alkaline, acid) were studied to generate Alcaligenes eutrophus and sludge lysates and to evaluate their biodegradability . Gentle treatment conditions produced the best results . Complete cell deactivation was obtained for temperatures higher than 55 degrees C . The release kinetics were similar for temperatures varying from 60 degrees C to 100 degrees C . A 20-min incubation was suitable for reaching 80% of the maximum releasable carbon . In thermal-chemical hydrolysis, NaOH was the most efficient for inducing cell lysis . Carbon release was a two-step process . First an immediate release occurred, which was of the same order of magnitude for A . eutrophus and sludge {100-200 mg dissolved organic C (DOC) g total suspended solids (TSS)-1}, followed by a post-treatment release . The second step was virtually equivalent to the first for sludge, and weaker for A . eutrophus (< 50 mg DOC g TSS-1) . The biodegradability of the soluble fraction, both the immediate and the post-treatment carbon release, was investigated . The optimal degradation yield, obtained with sludge cells, reached 55% after 48 h of incubation and 80% after 350 h . The most consistent lysis and biodegradation results occurred at pH 10 and 60 degrees C after a 20-min incubation.

J Colloid Interface Sci, 1999 Jul 15, 215(2), 443 - 445
Effects of Salinity on Expression Dewatering of Waste Activated Sludge; Jean DS et al.; This work evaluates filtration followed by consolidation characteristics of sodium chloride containing activated sludge . Experimental results indicate that contact time and salinity level affect the dewatering efficiency . Considering the consolidation stage, a critical salinity level (around 1-2% (w/w)) is observed at which the contribution of secondary consolidation stage reaches its minimum . Meanwhile the creeping among constituent aggregates becomes much easier than in the original sludge . In addition, double-layer compression/hydrophobic interactions and ion exchange partially account for the experimental results .

Int J Biol Macromol, 1999 Jun-Jul, 25(1-3), 105 - 9
PHA production by activated sludge; Satoh H et al.; The production of polyhydroxyalkanoate by anaerobic-aerobic activated sludge was reviewed concentrating on the biochemical mechanisms and on the trials to increase polyhydroxyalkanoate (PHA) content in activated sludge . The anaerobic aerobic activated sludge system selects microorganisms with the capabilities to couple glycolysis, polyphosphate degradation, and PHA accumulation for anaerobic substrate uptake . Some of the PHA-related metabolisms observed there have not been seen in pure cultures so far . Such metabolisms are the formation of PHA containing 3-hydroxy-2-methylvalerate, and '3-hydroxyvalerate fermentation' in which glucose or glycogen is converted to 3-hydroxyvalerate-rich PHA while yielding energy . The PHA content of activated sludge can be increased up to 62% by applying a microaerophilic-aerobic activated sludge process . PHA production by activated sludge is worth investigation.

Biotechnol Bioeng, 1999 Jun 5, 63(5), 507 - 15
Anaerobic phosphate release from activated sludge with enhanced biological phosphorus removal . A possible mechanism of intracellular pH control
Bond PL, Keller J, Blackall LL.
The biochemical mechanisms of the wastewater treatment process known as enhanced biological phosphorus removal (EBPR) are presently described in a metabolic model . We investigated details of the EBPR model to determine the nature of the anaerobic phosphate release and how this may be metabolically associated with polyhydroxyalkanoate (PHA) formation . Iodoacetate, an inhibitor of glycolysis, was found to inhibit the anaerobic formation of PHA and phosphate release, supporting the pathways proposed in the EBPR metabolic model . In the metabolic model, it is proposed that polyphosphate degradation provides energy for the microorganisms in anaerobic regions of these treatment systems . Other investigations have shown that anaerobic phosphate release depends on the extracellular pH . We observed that when the intracellular pH of EBPR sludge was raised, substantial anaerobic phosphate release was caused without volatile fatty acid (VFA) uptake . Acidification of the sludge inhibited anaerobic phosphate release even in the presence of VFA . From these observations, we postulate that an additional possible role of anaerobic polyphosphate degradation in EBPR is for intracellular pH control . Intracellular pH control may be a metabolic feature of EBPR, not previously considered, that could have some use in the control and optimisation of EBPR .

Syst Appl Microbiol, 1999 May, 22(2), 205 - 14
Genotypic diversity of Acidovorax strains isolated from activated sludge and description of Acidovorax defluvii sp . nov; Schulze R et al.; Fluorescence in situ hybridization of activated sludge samples from a municipal wastewater treatment plant using oligonucleotide probes specific for Acidovorax demonstrated that these bacteria are highly abundant in this environment . For the targeted cultivation of representatives belonging to this genus, isolates grown on agar plates after serial dilution were screened by whole-cell hybridization with specific probes . The obtained strains clustered in two phylogenetic groups as determined by 16S rRNA gene sequence analyses . The isolates of one cluster were phylogenetically and genotypically closely related to A . delafieldii . In contrast, the strains of the other cluster were genotypically and phenotypically distinct from the hitherto known Acidovorax species . Therefore, a new species, Acidovorax defluvii sp . nov., was proposed for these strains . The main characteristics of the newly defined species are as follows: Gram-negative, motile or non-motile rods with rounded ends, often with large polyhydroxybutyrate granules . In broth cultures flocs are formed . Test for cytochrome oxidase is positive with all strains . The majority of strains is catalase positive and reduces nitrate . All strains are metabolically inactive against most carbohydrates and organic acids . Fatty acid patterns are typical for the genus Acidovorax . The guanine-plus-cytosine content of DNAs varies between 62 and 64 mol% . The type strain of A . defluvii is BSB411T (DSM 12644) . A new 16S rRNA-targeted oligonucleotide probe reacting by in situ hybridization with all known Acidovorax species, including A . defluvii sp . nov., was designed.

Syst Appl Microbiol, 1999 May, 22(2), 186 - 96
Specific oligonucleotide probes for in situ detection of a major group of gram-positive bacteria with low DNA G + C content; Meier H et al.; Almost one thousand 16S rRNA sequences of Gram-positive bacteria with a low DNA G + C content from public databases were analyzed using the ARB software package . A signature region was identified between positions 354 and 371 (E . coli numbering) for the Bacillus sub-branch of the Gram-positive bacteria with a low DNA G + C content, the former orders Bacillales and Lactobacillales . Three oligonucleotide probes, namely LGC354A, LGC354B, and LGC354C, were designed to target this diagnostic site . Their fluorescent derivatives were suitable for whole cell detection by fluorescence in situ hybridization (FISH) . Hybridization conditions were adjusted for differentiation of target and related non-target reference species . When applying FISH to whole bacterial cells in a sample of activated sludge from a communal wastewater treatment plant, members of the Bacillus sub-branch were detected at levels from 0.01% of cells in samples fixed with paraformaldehyde to over 8 percent in the same samples fixed with ethanol and treated with lysozyme . The problems of quantitative in situ analysis of Gram-positive bacteria with a low DNA G + C content in biofilm flocs are discussed and recommendations made . Members of the Bacillus sub-branch were detected in different abundances in activated sludge samples from different wastewater plants.

J Appl Microbiol, 1999 Jun, 86(6), 1008 - 16
Biodegradation of gasoline: kinetics, mass balance and fate of individual hydrocarbons; Solano-Serena F et al.; The degradation of gasoline by a microflora from an urban waste water activated sludge was investigated in detail . Degradation kinetics were studied in liquid cultures at 30 degrees C by determination of overall O2 consumption and CO2 production and by chromatographic analysis of all 83 identifiable compounds . In a first fast phase (2 d) of biodegradation, 74% of gasoline, involving mostly aromatic hydrocarbons, was consumed . A further 20%, involving other hydrocarbons, was consumed in a second slow phase (23 d) . Undegraded compounds (6% of gasoline) were essentially some branched alkanes with a quaternary carbon or/and alkyl chains on consecutive carbons but cycloalkanes, alkenes and C10- and C11-alkylated benzenes were degraded . The degradation kinetics of individual hydrocarbons, determined in separate incubations, followed patterns similar to those observed in cultures on gasoline . Carbon balance experiments of gasoline degradation were performed . The carbon of degraded gasoline was mainly (61.7%) mineralized into CO2, the remaining carbon being essentially converted into biomass.

Appl Environ Microbiol, 1999 Jul, 65(7), 2813 - 9
An outbreak of nonflocculating catabolic populations caused the breakdown of a phenol-digesting activated-sludge process; Watanabe K et al.; Activated sludge was fed phenol as the sole carbon source, and the phenol-loading rate was increased stepwise from 0.5 to 1.0 g liter-1 day-1 and then to 1.5 g liter-1 day-1 . After the loading rate was increased to 1.5 g liter-1 day-1, nonflocculating bacteria outgrew the sludge, and the activated-sludge process broke down within 1 week . The bacterial population structure of the activated sludge was analyzed by temperature gradient gel electrophoresis (TGGE) of PCR-amplified 16S ribosomal DNA (rDNA) fragments . We found that the population diversity decreased as the phenol-loading rate increased and that two populations (designated populations R6 and R10) predominated in the sludge during the last several days before breakdown . The R6 population was present under the low-phenol-loading-rate conditions, while the R10 population was present only after the loading rate was increased to 1.5 g liter-1 day-1 . A total of 41 bacterial strains with different repetitive extragenic palindromic sequence PCR patterns were isolated from the activated sludge under different phenol-loading conditions, and the 16S rDNA and gyrB fragments of these strains were PCR amplified and sequenced . Some bacterial isolates could be associated with major TGGE bands by comparing the 16S rDNA sequences . All of the bacterial strains affiliated with the R6 population had almost identical 16S rDNA sequences, while the gyrB phylogenetic analysis divided these strains into two physiologically divergent groups; both of these groups of strains could grow on phenol, while one group (designated the R6F group) flocculated in laboratory media and the other group (the R6T group) did not . A competitive PCR analysis in which specific gyrB sequences were used as the primers showed that a population shift from R6F to R6T occurred following the increase in the phenol-loading rate to 1.5 g liter-1 day-1 . The R10 population corresponded to nonflocculating phenol-degrading bacteria . Our results suggest that an outbreak of nonflocculating catabolic populations caused the breakdown of the activated-sludge process . This study also demonstrated the usefulness of gyrB-targeted fine population analyses in microbial ecology.

Can J Microbiol, 1999 Feb, 45(2), 106 - 15
Laboratory evaluation of crude oil biodegradation with commercial or natural microbial inocula; Thouand G et al.; Experiments have been performed to screen eight microbial commercial products that, according to the manufacturers, are able to degrade crude oil . This study compared the crude oil biodegradation activity of commercial inocula with that of natural inocula (activated sludge and tropical aquarium water) . Some of the latter were previously adapted to the crude oil as the only carbon source . Nutrients and sorbents in the commercial formulations were eliminated, and each inoculum was precultured on marine yeast extract medium . Crude oil biodegradability tests were conducted with close initial substrate concentration to initial bacterial concentration ratios (S0/X0) of 0.94 g of crude oil/10(9) CFU, which allowed a comparison of biodegradation activity . The inocula oxidized the crude oil after a short lag time of less than 3-18 days . After that time, the rate of oxidation varied between 45 and 244 mg O2/(L.day) . Crude oil biodegradation after a 28-day test was effective only for 10 out of 12 inocula (from 0.1 to 25% in weight) . Biodegradation mainly corresponded to the saturated fraction of the crude oil; the asphaltene fraction was never significantly biodegraded . Our results led to the conclusion that natural inocula, either adapted or not adapted to crude oil, were the most active (from 16 to 25% of loss in crude oil weight) and only one commercial inoculum was able to degrade 18% of the crude oil . Other inocula had a biodegradation activity ranging from 0.1 to 14%.

Curr Microbiol, 1999 Jun, 38(6), 315 - 9
DNA extraction from activated sludges; Bourrain M et al.; To optimize the cell lysis step for DNA extraction from activated sludge samples, two floc dispersion methods (sonication versus stirring with a cation exchange resin), and three cell lysis treatments (lysozyme + SDS, sonication in a water bath, and thermal shock) were tested . For dispersion, stirring with cation exchange resin was more efficient than sonication . The cell lysis procedures were applied in two sequences, and DNA was quantified after each cell lysis treatment . Lysozyme + SDS was the most effective step in the cell lysis procedures . The cell lysis treatment sequences giving the highest DNA yields were not the same for all the sludges . The differences in sludge microbial compositions and floc structures required specifically adapted cell lysis protocols . The proposed protocols were highly efficient for DNA extraction, yielding about 50 mg DNA g-1 volatile suspended solids, and allowed PCR amplification of 16S rDNA.

J Hazard Mater, 1999 May 31, 67(1), 95 - 109
Factors influencing suspended solids concentrations in activated sludge settling tanks; Kim Y et al.; A significant fraction of the total mass of sludge in an activated sludge process may be in the settling tanks if the sludge has a high sludge volume index (SVI) or when a hydraulic overload occurs during a rainstorm . Under those conditions, an accurate estimate of the amount of sludge in the settling tanks is needed in order to calculate the mean cell residence time or to determine the capacity of the settling tanks to store sludge . Determination of the amount of sludge in the settling tanks requires estimation of the average concentration of suspended solids in the layer of sludge (XSB) in the bottom of the settling tanks . A widely used reference recommends averaging the concentrations of suspended solids in the mixed liquor (X) and in the underflow (Xu) from the settling tanks (XSB=0 . 5 inverted question markX+Xu inverted question mark) . This method does not take into consideration other pertinent information available to an operator . This is a report of a field study which had the objective of developing a more accurate method for estimation of the XSB in the bottom of the settling tanks . By correlation analysis, it was found that only 44% of the variation in the measured XSB is related to sum of X and Xu . XSB is also influenced by the SVI, the zone settling velocity at X and the overflow and underflow rates of the settling tanks . The method of averaging X and Xu tends to overestimate the XSB . A new empirical estimation technique for XSB was developed . The estimation technique uses dimensionless ratios; i.e., the ratio of XSB to Xu, the ratio of the overflow rate to the sum of the underflow rate and the initial settling velocity of the mixed liquor and sludge compaction expressed as a ratio (dimensionless SVI) . The empirical model is compared with the method of averaging X and Xu for the entire range of sludge depths in the settling tanks and for SVI values between 100 and 300 ml/g . Since the empirical model uses dimensionless ratios, the regression parameters are also dimensionless and the model can be readily adopted for other activated sludge processes . A simplified version of the empirical model provides an estimation of XSB as a function of X, Xu and SVf and can be used by an operator when flow conditions are normal .

Int J Syst Bacteriol, 1999 Apr, 49 Pt 2, 459 - 68
Tessaracoccus bendigoensis gen . nov., sp . nov., a gram-positive coccus occurring in regular packages or tetrads, isolated from activated sludge biomass; Maszenan AM et al.; An isolate of a Gram-positive bacterium, designated strain Ben 106T, was obtained in pure culture by micromanipulation of a biomass sample obtained from a laboratory-scale sequencing batch reactor . This isolate grew axenically as cocci or clusters of cocci arranged in regular tetrads and was morphologically similar to the dominant organism observed in the biomass . This morphology resembled that of some Gram-positive and -negative bacteria and the so-called 'G-bacteria' commonly seen in activated sludge samples . Strain Ben 106T is a non-motile, facultative anaerobe . It is oxidase-negative, catalase-positive and is capable of reducing nitrate . This organism can grow between 20 and 37 degrees C, with an optimum temperature of 25 degrees C . The pH range for growth is between 6.0 and 9.0, with an optimum pH of 7.5 . The isolate stained positively for intracellular polyphosphate granules . The diagnostic diamino acid of the peptidoglycan is LL-diaminopimelic acid (LL-A2pm) with a glycine moiety at position 1 of the peptide subunit, which characterizes the presence of a rare peptidoglycan (type A3-gamma') . Two menaquinones, MK-9(H4) and MK-7(H4), are present and the main cellular fatty acid is 12-methyltetradecanoic acid . The G + C content is 74 mol% . From phenotypic characteristics and 16S rDNA sequence analysis, the isolate differed sufficiently from its closest phylogenetic relatives, namely Propionibacterium propionicum, Propioniferax innocua, Friedmanniella antarctica, Luteococcus japonicus and Microlunatus phosphovorus in the A1 subdivision of the Gram-positive bacteria (i.e . Firmicutes with a high G + C content), suborder Propionibacterineae, to be placed in a new genus, Tessaracoccus, as Tessaracoccus bendigoensis gen . nov., sp . nov . The type strain is Ben 106T (= ACM 5119T).

FEMS Microbiol Lett, 1999 May 1, 174(1), 9 - 17
Monitoring the conjugal transfer of plasmid RP4 in activated sludge and in situ identification of the transconjugants; Geisenberger O et al.; A GFPmut3b-tagged derivative of broad host-range plasmid RP4 was used to monitor the conjugative transfer of the plasmid from a Pseudomonas putida donor strain to indigenous bacteria in activated sludge . Transfer frequencies were determined to be in the range of 4 x 10(-6) to 1 x 10(-5) transconjugants per recipient . In situ hybridisation with fluorescently labeled, rRNA-targeted oligonucleotides was used to phylogenetically affiliate the bacteria that had received the plasmid.

Sci Total Environ, 1999 Feb 16, 227(1), 41 - 7
Distribution of 1,4-dioxane in relation to possible sources in the water environment; Abe A; The distribution of 1,4-dioxane was investigated in surface and groundwater in relation to possible sources . Water samples from river, coastal sea, and groundwater were collected and examined in Kanagawa Prefecture, Japan, from 1995 to 1998 . Almost all samples were contaminated by 1,4-dioxane . On annual changes, the concentrations did not vary significantly in river water . However, some samples were still heavily polluted in groundwater . The highest correlation was between the concentration of 1,4-dioxane and 1,1,1-trichloroethane in the polluted groundwater samples . Soil and groundwater that was polluted by 1,1,1-trichloroethane in the past is still a possible source of 1,4-dioxane . In regard to a survey of other sources, effluents from the combined collection treatment from apartment houses, river basin sewage systems, and chemical plants were examined . The load unit of 1,4-dioxane from the treated effluent of domestic wastewater was assumed to be approximately 0.25 mg/person/day . This was derived from commonly used household chemicals, which contained 1,4-dioxane as a by-product . In river basin sewage systems, the concentrations in effluents varied significantly . High concentration inflows were probably not degraded and released . Although 50-60% of removal was recognized in acclimatized activated sludge from a chemical plant, 1,4-dioxane was easily desorbed with water from sludge.

Sci Total Environ, 1999 Feb 16, 227(1), 13 - 28
Mass balance and distribution of sludge-borne trace elements in a silt loam soil following long-term applications of sewage sludge; Baveye P et al.; Soil samples were collected at 15-cm increments to a depth of 75 cm from plots on a silt loam soil where until several years earlier and for 14 years, anaerobically digested sewage sludge had been annually applied by furrow irrigation . The study protocol consisted of four replications of 6.1 x 12.2-m plots with 0 (T0), 1/4-maximum (T1), 1/2-maximum (T2) and maximum (T3) sludge application rates randomized within blocks . When sludge applications were terminated, maximum sludge-treated plots had received 765 Mg ha-1 (dry weight equivalent) of sludge solids . Total soil concentrations of Cd, Cr, Cu, Ni, Pb and Zn had been significantly enhanced by all sludge application rates to a soil depth of 30 cm . Below the 30-cm depth, total soil Cd was increased to 75 cm, total Zn to 45 cm (T2 and T3 only), total Cr to 60 cm (T2 and T3 only), but total Cu, Pb, and Ni were not increased at depth . Despite the lack of significant increases in subsoil concentrations for some metals, mass balance calculations showed a relatively high proportion of all the above sludge-borne heavy metals to be unaccounted for in the soil profile for each application rate . Mass balance calculations of losses ranged from a high of 60% for Ni to a low of 36% for Cu and Pb . Similar losses were calculated from metal concentrations measured in soil samples taken at the time the sludge was applied . In soil surface samples (0-15 cm) from maximum sludge-treated plots, percentages of total metal concentration extracted with 4.0 M HNO3 ranged from a low of 31 for Zn to a high of 75 for Cu . Efficiency of metal extraction by HNO3 was inconsistent, depending on the soil horizon and sludge treatment, so that evaluation of HNO3-extractable metals is not a reliable method of estimating total metal retention in the profiles . In soil surface samples from maximum sludge-treated plots, the percentage of total metal contents extracted with DTPA ranged from a low of 0.03 for Cr to a high of 59 for Cd . The DTPA extractable levels of Cu, Ni, and Pb were higher in the subsoils of the sludge-treated soils, indicating that these metals had been redistributed from the surface layer to deeper zones in the profile of sludge-amended soil, despite the absence of elevated total concentrations of these three metals in the deeper subsoil.

J Microbiol Methods, 1999 Mar, 35(2), 111 - 9
Determination of polyhydroxyalkanoates in activated sludge by ion chromatographic and enzymatic methods; Hesselmann RP et al.; Two new detection methods for the determination of poly-beta-hydroxybutyrate (PHB) and -valerate (PHV) are described . Both methods are based on depolymerization of PHB/PHV to 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) . Depolymerization was achieved by either propanolic or hydrolytic digestion . Propanolic digestion transformed commercial PHB/PHV stoichiometrically into 3HB/3HV and yielded apparently complete recoveries of bacterial PHB/PHV from activated sludge . Hydrolytic digestion was suitable only for PHB determination . For quantification of 3HB and 3HV directly from digested sludge, a method based on ion-exchange chromatography and conductivity detection was developed (IC-method) . Alternatively, the total of 3HB and 3HV was quantified using a commercial enzymatic test kit and colorimetric detection (enzyme method) . Both detection methods are easier to perform than previous methods and are suitable for complex matrices such as activated sludge . The IC-method is recommended for high sample throughputs or if distinction between PHB and PHV is essential . Enzymatic detection is recommended if a few samples per day have to be measured immediately or if an ion chromatograph is unavailable.

Biotechnol Bioeng, 1998 Aug 20, 59(4), 438 - 44
Degradation of perchloroethylene and dichlorophenol by pulsed-electric discharge and bioremediation
Yee DC, Chauhan S, Yankelevich E, Bystritskii V V, Wood TK.
Pulsed electric discharge (PED) and bioremediation were combined to create a novel two-stage system which dechlorinates the halogenated pollutants, 2,4-dichlorophenol and perchloroethylene, with repetitive (0.1-1 kHz), short pulse ( approximately 100 ns), low voltage (40-80 kV) discharges and then mineralizes the less chlorinated products with aerobic bacteria . A 6.1 mM aqueous dichlorophenol sample was cycled through the PED reactor (60 kV of applied pulsed voltage and 300 Hz) 6 times, resulting in the release of 55% of the initial dichlorophenol chloride ions (1 mM Cl- removed each cycle) . The respective average specific efficiency is 0.4-0.6 keV/(Cl- molecule) . Pseudomonas mendocina KR1, which grows in minimal medium supplemented with phenol but not with dichlorophenol, increased in cell density in all cultures supplemented with the PED-treated DCP samples and yielded a maximum of two-fold additional Cl- released compared to the PED-related alone . The number of PED-treatment cycles, voltage, and frequency were also varied, showing that both cell densities and overall dichlorophenol dechlorination were highly dependent upon the number of PED-treatment cycles, rather than the tested voltages and frequencies . Using this two-stage treatment system, PED released 31% of the initial chloride ions from dichlorophenol (after three cycles at 40-45 kV and 1.2 kHz) while P . mendocina KR1 in the second stage increased dechlorination to 90% . These results were corroborated by the 35% additional chloride release found with activated sludge cultures . Perchloroethylene (0.6 mM) was similarly treated in a first-stage PED reactor (80% chloride removal after four cycles) followed by biodegradation of the dechlorinated products with a recombinant toluene o-monooxygenase-expressing Pseudomonas fluorescens strain . Gas chromatographic analysis showed that the PED reactor created less-chlorinated byproducts (i.e., trichloroethylene) that were removed (74%) upon exposure to the recombinant bacterium .

Biotechnol Bioeng, 1998 Jan 20, 57(2), 155 - 63
Analysis of endogenous process behavior in activated sludge; Keesman KJ et al.; In this article, an autonomous four-compartment model that describes the endogenous respiration in an aerobic biodegradation process is proposed and analyzed theoretically . First, the multi-time scale of the system's behavior, to be taken into account in subsequent analyses, is emphasized . Then, an identifiability and observability study, given measurements of MLVSS (mixed liquor volatile suspended solids) and respiration rate, is performed for use under practical circumstances, such as in state and parameter estimation . It appears that the process is observable, but not fully identifiable . Hence, for the identification of some of the model parameters, additional measurements or experiments, also indicated here, have to be performed . Furthermore, it is shown that, under quasi-steady state conditions which, in general, appear shortly after initialization of an endogenous respiration experiment, the model can be reduced significantly . Finally, results of parameter estimation from available data are presented and discussed .

J Microbiol Methods, 1999 Feb, 35(1), 53 - 63
Analysis of the structural diversity of mycolic acids of Rhodococcus and Gordonia {correction of Gordonla} isolates from activated sludge foams by selective ion monitoring gas chromatography-mass spectrometry (SIM GC-MS)
Stratton HM, Brooks PR, Seviour RJ.
A method using Selective Ion Monitoring (SIM) gas chromatography-mass spectrometry is described for analysis of mycolic acids which reveals a hitherto unrecognised chemical structural diversity among these in some members of the Mycolata . The structural interpretation of mass spectral data of mycolic acids from Rhodococcus spp and Gordonia {corrected} spp using SIM is discussed.

Antonie Van Leeuwenhoek, 1998 Jul-Oct, 74(1-3), 41 - 8
In situ detection of rhodococci associated with activated sludge foams; Davenport RJ et al.; Genus-specific 16S rRNA targeted oligonucleotide probes, Rco1 and Rco2, were designed and used to detect rhodococci in activated sludge foam samples by confocal laser scanning microscopy . Pure cultures were used to find the optimal hybridisation conditions which were determined by comparing the mean fluorescent intensities of target and non-target cells from images captured using a confocal laser scanning microscope (CLSM) . The combination of fluorescent in situ hybridisation with rRNA-targeted oligonucleotide probes and confocal laser scanning microscopy provides an effective way of detecting rhodococci in environmental samples.

Ecotoxicol Environ Saf, 1999 Feb, 42(2), 163 - 70
A study of toxic effects of heavy metal contaminants from sludge-supplemented diets on male Wistar rats; Bag S et al.; Activated sludge is a rich source of nitrogenous matter and has been recommended as cheap supplement in animal feed . It has been incorporated into cattle and poultry feed . It is well known that sewage of purely domestic origin is also contaminated with heavy metals, pesticides, and other organic pollutants . A study was undertaken to determine the toxic effects of heavy metal-contaminated domestic sewage sludge on young male Wistar rats by supplementing dehydrated activated sludge in their diet at concentrations of 5, 10, 15 and 20% . The sludge was found to be contaminated with 1.820 (zinc), 0.273 (nickel), 0.017 (lead), 0.053 (copper), 0.006 (chromium), and 0.005 (cadmium)mg/g of dry sludge, by analysis by atomic absorption spectroscopy . The toxic effects of sludge-supplemented diets on individual groups of rats were assessed by assaying various enzyme activities in serum, liver, muscle, and brain . Levels of serum and liver alanine aminotransferase and succinate dehydrogenase (SDH) were significantly low in all the sludge-supplemented diet-fed (SSDF) rats . Similarly, serum lactate dehydrogenase (LDH) and muscle SDH activity were also significantly reduced in the SSDF rats . On the other hand, liver and muscle LDH, serum and liver aspartate aminotransferase, and serum and muscle alkaline phosphatase activities were significantly higher in all the SSDF animals . Brain and muscle acetylcholinesterase activity was significantly high in all the SSDF groups . This study indicates that even though the sludge is a rich source of nitrogenous matter, its supplementation in poultry and animals feed should be done with caution . Otherwise, the contaminants found in the sludge will biomagnify in the food chain and lead to various toxicological hazards .

Appl Environ Microbiol, 1999 Mar, 65(3), 1289 - 97
Combination of fluorescent in situ hybridization and microautoradiography-a new tool for structure-function analyses in microbial ecology; Lee N et al.; A new microscopic method for simultaneously determining in situ the identities, activities, and specific substrate uptake profiles of individual bacterial cells within complex microbial communities was developed by combining fluorescent in situ hybridization (FISH) performed with rRNA-targeted oligonucleotide probes and microautoradiography . This method was evaluated by using defined artificial mixtures of Escherichia coli and Herpetosiphon aurantiacus under aerobic incubation conditions with added {3H}glucose . Subsequently, we were able to demonstrate the potential of this method by visualizing the uptake of organic and inorganic radiolabeled substrates ({14C}acetate, {14C}butyrate, {14C}bicarbonate, and 33Pi) in probe-defined populations from complex activated sludge microbial communities by using aerobic incubation conditions and anaerobic incubation conditions (with and without nitrate) . For both defined cell mixtures and activated sludge, the method proved to be useful for simultaneous identification and analysis of the uptake of labeled substrates under the different experimental conditions used . Optimal results were obtained when fluorescently labeled oligonucleotides were applied prior to the microautoradiographic developing procedure . For single-cell resolution of FISH and microautoradiographic signals within activated sludge flocs, cryosectioned sample material was examined with a confocal laser scanning microscope . The combination of in situ rRNA hybridization techniques, cryosectioning, microautoradiography, and confocal laser scanning microscopy provides a unique opportunity for obtaining cultivation-independent insights into the structure and function of bacterial communities.

Acta Microbiol Pol, 1998, 47(3), 305 - 12
An attempt to use selected strains of bacteria adapted to high concentrations of petroleum oil to increase the effective removal of petroleum products in excess activated sludge in laboratory conditions; Bieszkiewicz E et al.; Forty two strains of bacteria were isolated from excess activated sludge from petroleum wastewater treatment plant . The strains were identified and classified to the following groups: Enterobacteriaceae (7 strains), Anitratum (3 strains), Pseudomonas (13 strains), Micrococcus (12 strains), Comamonas (2 strains), Xanthomonas (2 strains), Achromobacter (1 strain) and Vibrio-Aeromonas (1 strain) . One of the isolates was found to be a yeast strain . Following preliminary selection ten strains, showing the best growth in medium with oil fraction as sole carbon source, were chosen for further studies . The selected strains belong to Pseudomonas (6 strains), Xanthomonas (2 strains), Micrococcus (1 strain) and Saccharomyces (1 strain) . The strains were adapted to high oil concentration (500-2000 mg/L) and an attempt to use them to intensify removal of petroleum products from excess activated sludge was made . The sludge was inoculated with a mixture of the isolated strains . The experiment was carried out three times, each time with a fresh sample of the excess sludge . The obtained results show that the inoculation of activated sludge with the strains active against oil reduced the petroleum products content by 20% in 14 days . The greatest reduction of oil was observed in sludge with the lowest dry weight, that is with the greatest degree of hydration . The dry weight of the excess sludge did not significantly decrease during the course of the experiment, after having been inoculated with the mixture of strains.

Ecotoxicol Environ Saf, 1999 Jan, 42(1), 16 - 21
Toxicity of chromium to activated sludge; Vankova S et al.; The work deals with the toxicity of hexavalent and trivalent chromium to activated sludge . Cr(VI) was added as K2Cr2O7, and Cr(III) as Cr2(SO4)3 . Toxicity is expressed as the inhibition of respiratory activity of microorganisms present in activated sludge . Respiration was measured by two methods, by means of an oximeter with an oxygen electrode and by means of a manometric apparatus permitting continuous observation of biological oxygen demand (BOD) . The equation of the normal distribution function was used to construct inhibition curves and to calculate effective concentration (EC50) . The influence of exposure time was observed as was the influence of concentration of activated sludge on the value of EC50 . The 1-h EC50 for Cr(VI) by the ISO method was determined to be in the range of 40-90 mg/liter . A greater scatter of measured values, 46-201mg/liter, was found for the first hour of exposure by the manometric method . In the case of Cr(III) only combined inhibition by chromium ions and pH was determined . The 0.5-h EC50 was 49 mg/liter .

Microbiology, 1998 Dec, 144 ( Pt 12), 3257 - 66
Monitoring a widespread bacterial group: in situ detection of planctomycetes with 16S rRNA-targeted probes; Neef A et al.; The group of planctomycetes represents a separate line of descent within the domain Bacteria . Two phylum-specific 16S rRNA-targeted oligonucleotide probes for planctomycetes have been designed, optimized for in situ hybridization and used in different habitats to detect members of the group in situ . The probes, named PLA46 and PLA886, are targeting all or nearly all members of the planctomycete line of descent . Planctomycetes could be detected in almost all samples examined, e.g . a brackish water lagoon, activated sludge, and other wastewater habitats . In situ probing revealed quite uniform morphology and spatial arrangement of the detected cells but profound differences in abundance ranging from less than 0.1% to several percentage of the total cells . Single coccoid cells with diameters between 1 and 2.5 microm were dominating in most samples with the exception of the lagoon, in which rosettes of pear-shaped cells were abundant . The planctomycetes showed generally no hybridization signals with the bacterial probe EUB338, which is in accordance with base changes in their 165 rRNA sequences . A discrete ultrastructure of planctomycete cells was suggested by double staining with rRNA-targeted probes and the DNA-binding dye 4',6-diamidino-2-phenylindole (DAPI) . The probe-conferred fluorescence was distributed in a ring-shaped manner around a central DAPI spot . The two probes developed extend the existing set of group-specific rRNA-targeted probes and help to elucidate the basic composition of bacterial communities in a first step of differential analysis . In situ hybridization of environmental samples indicated widespread presence of planctomycetes in different ecosystems.

Appl Environ Microbiol, 1999 Jan, 65(1), 102 - 9
Thermal gradient gel electrophoresis analysis of bioprotection from pollutant shocks in the activated sludge microbial community; Eichner CA et al.; We used a culture-independent approach, namely, thermal gradient gel electrophoresis (TGGE) analysis of ribosomal sequences amplified directly from community DNA, to determine changes in the structure of the microbial community following phenol shocks in the highly complex activated sludge ecosystem . Parallel experimental model sewage plants were given shock loads of chlorinated and methylated phenols and simultaneously were inoculated (i) with a genetically engineered microorganism (GEM) able to degrade the added substituted phenols or (ii) with the nonengineered parental strain . The sludge community DNA was extracted, and 16S rDNA was amplified and analyzed by TGGE . To allow quantitative analysis of TGGE banding patterns, they were normalized to an external standard . The samples were then compared with each other for similarity by using the coefficient of Dice . The Shannon index of diversity, H, was calculated for each sludge sample, which made it possible to determine changes in community diversity . We observed a breakdown in community structure following shock loads of phenols by a decrease in the Shannon index of diversity from 1.13 to 0.22 in the noninoculated system . Inoculation with the GEM (Pseudomonas sp . strain B13 SN45RE) effectively protected the microbial community, as indicated by the maintenance of a high diversity throughout the shock load experiment (H decreased from 1.03 to only 0.82) . Inoculation with the nonengineered parental strain, Pseudomonas sp . strain B13, did not protect the microbial community from being severely disturbed; H decreased from 1.22 to 0.46 for a 3-chlorophenol-4-methylphenol shock and from 1.03 to 0.70 for a 4-chlorophenol-4-methylphenol shock . The catabolic trait present in the GEM allowed for bioprotection of the activated sludge community from breakdown caused by toxic shock loading . In-depth TGGE analysis with similarity and diversity algorithms proved to be a very sensitive tool to monitor changes in the structure of the activated sludge microbial community, ranging from subtle shifts during adaptation to laboratory conditions to complete collapse following pollutant shocks.

J Colloid Interface Sci, 1998 Aug 15, 204(2), 357 - 62
Determination of Structure of Aggregates by Confocal Scanning Laser Microscopy; Thill A et al.; The fractal dimension of a particle aggregate can provide fundamental information on the structure and origin of the aggregate . The analysis of large chemically homogeneous fractal objects has been achieved, but reliable methods of estimating the fractal dimensions of large and chemically heterogeneous aggregates are needed . To this end, we used confocal scanning laser microscopy in which thin optical sections of aggregates were obtained in order to calculate their 2D and ultimately 3D fractal dimensions according to the Mandelbrot theory . Fractal dimensions of 2.08 +/- 0.11 for a Brownian aggregation of latex particles and 2.25 +/- 0.12 for shear aggregation were determined using the confocal technique . These values are within the ranges for universality classes predicted for such aggregates and observed by previous investigators . Thus, this method appears to provide reliable estimates of the fractal dimension with particular utility in the characterization of aggregates composed of larger particles or complex materials where the fractal dimension may not be accessible by light-scattering measurements . The confocal method is used to analyze flocs of activated sludge material as one example of the application of this method to more complex, large (up to 500 microm), and chemically heterogeneous flocs .

Biodegradation, 1998, 9(2), 91 - 102
Biodegradation of N-methylmorpholine-N-oxide; Meister G et al.; N-Methylmorpholine-N-oxide (NMMO) is capable of dissolving cellulose without any further addition of chemicals . The solution can be used to produce cellulosic staple fibres by pressing it through spinning jets into an aqueous spinning bath . Because of results from conventional biodegradation tests using non-adapted activated sludge, the solvent is generally considered being persistent . The object of the described work was to show, whether and how activated sludge can be adapted to N-methylmorpholine-N-oxide and whether it is possible to purify NMMO-containing wastewaters in conventional wastewater treatment plants . The experiments showed that the sludge can be adapted within about 15-20 days . Adapted sludge can degrade the substance itself and its most important metabolites to concentrations below their detection levels and retain this ability even during limited periods without solvent being present in the wastewater . The main requirement for a successful adaptation is a high sludge age . The degradation takes place in several steps . First, NMMO is reduced to N-methylmorpholine . The next step is a demethylation of N-methylmorpholine to morpholine . This step is crucial for the adaptation process . Once morpholine has been formed, the adaptation proceeds very quickly until none of the substances in question can be detected any longer . So the next step must be the cleavage of the morpholine ring structure.

Appl Environ Microbiol, 1998 Nov, 64(11), 4396 - 402
Molecular detection, isolation, and physiological characterization of functionally dominant phenol-degrading bacteria in activated sludge; Watanabe K et al.; DNA was isolated from phenol-digesting activated sludge, and partial fragments of the 16S ribosomal DNA (rDNA) and the gene encoding the largest subunit of multicomponent phenol hydroxylase (LmPH) were amplified by PCR . An analysis of the amplified fragments by temperature gradient gel electrophoresis (TGGE) demonstrated that two major 16S rDNA bands (bands R2 and R3) and two major LmPH gene bands (bands P2 and P3) appeared after the activated sludge became acclimated to phenol . The nucleotide sequences of these major bands were determined . In parallel, bacteria were isolated from the activated sludge by direct plating or by plating after enrichment either in batch cultures or in a chemostat culture . The bacteria isolated were classified into 27 distinct groups by a repetitive extragenic palindromic sequence PCR analysis . The partial nucleotide sequences of 16S rDNAs and LmPH genes of members of these 27 groups were then determined . A comparison of these nucleotide sequences with the sequences of the major TGGE bands indicated that the major bacterial populations, R2 and R3, possessed major LmPH genes P2 and P3, respectively . The dominant populations could be isolated either by direct plating or by chemostat culture enrichment but not by batch culture enrichment . One of the dominant strains (R3) which contained a novel type of LmPH (P3), was closely related to Valivorax paradoxus, and the result of a kinetic analysis of its phenol-oxygenating activity suggested that this strain was the principal phenol digester in the activated sludge.

Appl Environ Microbiol, 1998 Oct, 64(10), 3731 - 9
Structural and functional dynamics of sulfate-reducing populations in bacterial biofilms
Santegoeds CM, Ferdelman TG, Muyzer G, de Beer D.
We describe the combined application of microsensors and molecular techniques to investigate the development of sulfate reduction and of sulfate-reducing bacterial populations in an aerobic bacterial biofilm . Microsensor measurements for oxygen showed that anaerobic zones developed in the biofilm within 1 week and that oxygen was depleted in the top 200 to 400 &mgr;m during all stages of biofilm development . Sulfate reduction was first detected after 6 weeks of growth, although favorable conditions for growth of sulfate-reducing bacteria (SRB) were present from the first week . In situ hybridization with a 16S rRNA probe for SRB revealed that sulfate reducers were present in high numbers (approximately 10(8) SRB/ml) in all stages of development, both in the oxic and anoxic zones of the biofilm . Denaturing gradient gel electrophoresis (DGGE) showed that the genetic diversity of the microbial community increased during the development of the biofilm . Hybridization analysis of the DGGE profiles with taxon-specific oligonucleotide probes showed that Desulfobulbus and Desulfovibrio were the main sulfate-reducing bacteria in all biofilm samples as well as in the bulk activated sludge . However, different Desulfobulbus and Desulfovibrio species were found in the 6th and 8th weeks of incubation, respectively, coinciding with the development of sulfate reduction . Our data indicate that not all SRB detected by molecular analysis were sulfidogenically active in the biofilm.

Indian J Exp Biol, 1998 Mar, 36(3), 321 - 4
Biodegradation of dimethylterephthalate by Comamonas acidovorans D-4; Patel DS et al.; Comamonas acidovorans D-4, capable of utilizing dimethylterephthalate (DMT) as the sole carbon source, was isolated from the activated sludge of petrochemical wastewater treatment plant . Almost complete utilization of as high as 0.5% (w/v) DMT was observed in 72 hr . Growth kinetics followed a parallel relation between the growth, DMT utilization and cell associated esterase activity . A cell free broth of DMT grown cells showed an extracellular esterase activity . During the DMT degradation an extracellular accumulation of terephthalic acid was found . Although, C . acidovorans grew on a number of phthalate esters and phthalic acids as the sole carbon source, growth was significantly high on phthalic acids . The potential of this organism in petrochemical pollution abatement is discussed.

Curr Microbiol, 1998 Sep, 37(3), 191 - 4
Bioremediation of epsilon-caprolactam from nylon-6 waste water by use of Pseudomonas aeruginosa MCM B-407; Kulkarni RS et al.; Nylon-6, a man-made polymer that finds its application in the manufacture of car tires, ropes, fabrics, automobile parts etc., is manufactured with epsilon-caprolactam . Waste water generated during production of nylon-6 contains the unreacted monomer . Owing to the polluting and toxic nature of epsilon-caprolactam, its removal from waste streams is necessary . Pseudomonas aeruginosa MCM B-407 was isolated from activated sludge used to treat waste from a factory producing nylon-6 . This organism was able to remove epsilon-caprolactam with simultaneous reduction in chemical oxygen demand (COD) . The degradation of epsilon-caprolactam in waste water was found to be optimal over a wide range of pH from 5.0 to 9.0, temperature of 30 degrees C, and under shake or aerated conditions, with an inoculum density of 10(5) cells/ml and with an incubation period of 24 - 48 h . Thus, Pseudomonas aeruginosa MCM B-407 isolated from the activated sludge exposed to epsilon-caprolactam may play an important role in the bioremediation of epsilon-caprolactam from the waste waters of industries manufacturing nylon-6.

Microb Ecol, 1998 Sep, 36(2), 111 - 20
Estimating the Growth Rate of a Bacterial Species in a Complex Mixture by Hybridization of Genomic DNA
Pollard PC.
> Abstract Advances in molecular techniques have enabled new approaches to identifying bacteria . However, once identified, there is no quantitative information on the in situ growth rate of the species, mainly because the technology has not been available . The quantitative incorporation of {methyl-3H}thymidine into dividing bacteria is coupled with a molecular (hybridization) method, to determine the growth rate of bacterial species in situ . The basis of this molecular method is a reverse gene probe-natural populations are labeled in situ with {methyl-3H}thymidine . The probe (3H-Tdr-DNA) is captured, using a hybridization procedure, on a positively charged nylon membrane on which is attached non-labeled target DNA . Two bacterial species, Bacillus cereus and Zoogloea ramigera, were used to demonstrate the principle in laboratory cultures and in a municipal activate sludge treatment process . The DNA of the dividing bacteria in activated sludge was radioactively labeled with {methyl-3H}thymidine, and the DNA of Z . ramigera was recovered using a DNA hybridization method . The recovered radioactively-labeled DNA was used to estimate the growth rate (0.03 x 10(9) cells . ml-1 . h-1) of Z . ramigera in situ . Simultaneously applying these two powerful molecular-based methods could potentially be used to study bacterial population dynamics in situ.

Appl Environ Microbiol, 1998 Aug, 64(8), 2853 - 8
Successive mineralization and detoxification of benzo{a}pyrene by the white rot fungus Bjerkandera sp . strain BOS55 and indigenous microflora; Kotterman MJ et al.; White rot fungi can oxidize high-molecular-weight polycyclic aromatic hydrocarbons (PAH) rapidly to polar metabolites, but only limited mineralization takes place . The objectives of this study were to determine if the polar metabolites can be readily mineralized by indigenous microflora from several inoculum sources, such as activated sludge, forest soils, and PAH-adapted sediment sludge, and to determine if such metabolites have decreased mutagenicity compared to the mutagenicity of the parent PAH . 14C-radiolabeled benzo{a}pyrene was subjected to oxidation by the white rot fungus Bjerkandera sp . strain BOS55 . After 15 days, up to 8.5% of the {14C}benzo{a}pyrene was recovered as 14CO2 in fungal cultures, up to 73% was recovered as water-soluble metabolites, and only 4% remained soluble in dibutyl ether . Thin-layer chromatography analysis revealed that many polar fluorescent metabolites accumulated . Addition of indigenous microflora to fungal cultures with oxidized benzo{a}pyrene on day 15 resulted in an initially rapid increase in the level of 14CO2 recovery to a maximal value of 34% by the end of the experiments (>150 days), and the level of water-soluble label decreased to 16% of the initial level . In fungal cultures not inoculated with microflora, the level of 14CO2 recovery increased to 13.5%, while the level of recovery of water-soluble metabolites remained as high as 61% . No large differences in 14CO2 production were observed with several inocula, showing that some polar metabolites of fungal benzo{a}pyrene oxidation were readily degraded by indigenous microorganisms, while other metabolites were not . Of the inocula tested, only PAH-adapted sediment sludge was capable of directly mineralizing intact benzo{a}pyrene, albeit at a lower rate and to a lesser extent than the mineralization observed after combined treatment with white rot fungi and indigenous microflora . Fungal oxidation of benzo{a}pyrene resulted in rapid and almost complete elimination of its high mutagenic potential, as observed in the Salmonella typhimurium revertant test performed with strains TA100 and TA98 . Moreover, no direct mutagenic metabolite could be detected during fungal oxidation . The remaining weak mutagenic activity of fungal cultures containing benzo{a}pyrene metabolites towards strain TA98 was further decreased by subsequent incubations with indigenous microflora.

J Appl Microbiol, 1998 Feb, 84(2), 272 - 84
Numerical taxonomy of Skermania piniformis and related isolates from activated sludge; Sodell JA et al.; The microscopic morphology of nocardioforms causing foaming problems in activated sludge usually consists of filaments with branches at either right angles (Nocardia amarae-Like Organisms, NALO) or acute angles (Pine Tree-Like Organisms, PTLO) . Fifty-nine nocardioforms, mainly with PTLO morphology, isolated from mixed liquor and foam samples from Australian activated sludge plants, and 39 reference strains of nocardioforms, including type strains, were characterized using 109 morphological and physiological characters . Cluster analysis and Principal Component Analysis showed that the activated sludge isolates clustered in six groups . All isolates that had typical PTLO morphology clustered unambiguously with the Skermania piniformis type strain (formerly called Nocardia pinensis) showing that, unlike NALO, reliable unequivocal identification of S . piniformis, based on microscopic morphology in activated sludge, was possible . Other foam isolates whose morphology consisted of branches with both acute angles and right angles clustered as two separate groups, probably representing new species . These could not be confused microscopically with S . piniformis, despite some branches showing acute angles . The remaining three groups had typical NALO morphology . One of these groups did not cluster with any reference cultures and may be a new species or genus.

Chemosphere, 1998 Jul, 37(2), 301 - 18
The efficiency of different phenol-degrading bacteria and activated sludges in detoxification of phenolic leachates; Kahru A et al.; Phenolic composition, toxicity and biodegradability of three different phenolic leachates/samples was studied . Samples A and C were the leachates from the oil-shale industry spent shale dumps at Kohtla-Jarve, Estonia . Sample B was a laboratory-prepared synthetic mixture of 7 phenolic compounds mimmicking the phenolic composition of the leachate A . Toxicity of these 3 samples was analyzed using two photobacterial test (BioTox and Microtox), Daphnia test (DAPHTOXKIT F pulex) and rotifiers' test (ROTOXKIT F) . All the LC50 values were in the range of 1-10%, leachate A being the most toxic . The growth and detoxifying potential (toxicity of the growth medium was measured using photobacterial tests) of 3 different phenol-utilizing bacteria and acclimated activated sludges was studied in shake-flask cultures . 30% leachate A (altogether 0.6 mM total phenolic compounds) was too toxic to rhodococci and they did not grow . Cell number of Kurthia sp . and Pseudomonas sp . in 30% leachate A increased by 2 orders of magnitude but despite of the growth of bacteria the toxicity of the leachate did not decrease even by 7 weeks of cultivation . However, if the activated sludge was used instead of pure bacterial cultures the toxicity of the 30% leachate A was eliminated already after 3 days of incubation . 30% samples B and C were detoxified by activated sludge even more rapidly, within 2 days . As the biodegradable part of samples A and B should be identical, the detoxification of leachate A compared to that of sample B was most probably inhibited by inorganic (e.g . sulphuric) compounds present in the leachate A . Also, the presence of toxic recalcitrant organic compounds in the leachate A (missed by chemical analysis) that were not readily biodegradable even by activated sludge consortium should not be excluded.

Chemosphere, 1998 Jul, 37(2), 219 - 35
Identification of lipophilic pollutants discharged from a Finnish pulp and paper mill; Koistinen J et al.; Lipophilic organic compounds originating from kraft pulping and papermaking were identified by straight gas chromatography/mass spectrometry (GC/MS) analyses . Samples analyzed included a primary clarifier effluent (PE) and a secondary clarifier effluent (SE) from the activated sludge treatment plant of a Finnish ECF-bleached (Elementally Chlorine Free) kraft pulp and paper mill . Liquid-liquid extraction composition of PE was compared with solid phase extraction (SPE) and dialysis of a semipermeable membrane device (SPMD) exposed to PE . Dichloromethane extracts of particulate material isolated from PE, sludges from both the primary and secondary clarifier, a sediment collected in the vicinity of the mill and whitefish subacutely exposed to the secondary treatment effluent were also investigated . Typical pulp mill-related compounds such as terpenes, terpenoids and aromatic compounds were identified in PE whereas these were non-detectable in SE . For example, thunbergene, thunbergol, squalene, longifolene and derivatives of abietic acid were observed in PE . Alkylated polycyclic aromatics were major compounds identified in the sediment sample with retene (C4-alkyl phenanthrene) as a predominant component.

Appl Environ Microbiol, 1998 Jul, 64(7), 2503 - 12
Quantification of Gordona amarae strains in foaming activated sludge and anaerobic digester systems with oligonucleotide hybridization probes; de los Reyes MF et al.; Previous studies have shown the predominance of mycolic acid-containing filamentous actinomycetes (mycolata) in foam layers in activated sludge systems . Gordona (formerly Nocardia) amarae often is considered the major representative of this group in activated sludge foam . In this study, small-subunit rRNA genes of four G . amarae strains were sequenced, and the resulting sequences were compared to the sequence of G . amarae type strain SE-6 . Comparative sequence analysis showed that the five strains used represent two lines of evolutionary descent; group 1 consists of strains NM23 and ASAC1, and group 2 contains strains SE-6, SE-102, and ASF3 . The following three oligonucleotide probes were designed: a species-specific probe for G . amarae, a probe specific for group 1, and a probe targeting group 2 . The probes were characterized by dissociation temperature and specificity studies, and the species-specific probe was evaluated for use in fluorescent in situ hybridizations . By using the group-specific probes, it was possible to place additional G . amarae isolates in their respective groups . The probes were used along with previously designed probes in membrane hybridizations to determine the abundance of G . amarae, group 1, group 2, bacterial, mycolata, and Gordona rRNAs in samples obtained from foaming activated sludge systems in California, Illinois, and Wisconsin . The target groups were present in significantly greater concentrations in activated sludge foam than in mixed liquor and persisted in anaerobic digesters . Hybridization results indicated that the presence of certain G . amarae strains may be regional or treatment plant specific and that previously uncharacterized G . amarae strains may be present in some systems.

Arch Microbiol, 1998 Apr, 169(4), 293 - 302
Characterization of Aquamicrobium defluvii gen . nov . sp . nov., a thiophene-2-carboxylate-metabolizing bacterium from activated sludge; Bambauer A et al.; A gram-negative bacterium was isolated from activated sewage sludge with thiophene-2-carboxylate as the sole source of carbon and with nitrate as an electron acceptor . The isolate, strain NKK, was a motile, oxidase- and catalase-positive, rod-like bacterium with a G+C content of 61.7 mol% . Besides nitrate, oxygen could serve as a terminal electron acceptor . Among many carbon sources tested, only a few sugars, fatty acids, and thiophene-2-carboxylate supported growth . Other heterocyclic compounds were not used . The sulfur atom of thiophene-2-carboxylate was oxidized to thiosulfate when cells were grown aerobically, or to elemental sulfur when cells were grown anaerobically with nitrate . Nitrate was reduced to nitrite . Growth on thiophene-2-carboxylate was dependent on the addition of molybdate to the medium . Tungstate, a specific antagonist of molybdate, inhibited growth on thiophene-2-carboxylate at concentrations > 10(-7) M . Three inducible enzymes involved in the metabolism of thiophene-2-carboxylate were detected: an ATP-, CoA-, thiophene-2-carboxylate- and Mg2+-dependent thiophene-2-carboxyl-CoA ligase (AMP-forming), a molybdenum-containing thiophene-2-carboxyl-CoA dehydrogenase, and a thiophene-2-carboxyl-CoA thioesterase . The sequence of the 16S rRNA gene suggested a classification of strain NKK within the alpha-subgroup of the Proteobacteria as a new genus and species, Aquamicrobium defluvii gen . nov . sp . nov . (DSM 11603), closely related to Mesorhizobium sp . and Phyllobacterium sp., but representing a distinct lineage equal in depth to those of the two mentioned genera . Aquamicrobium defluvii can be distinguished from both genera by a distinct spectrum of substrates, the maximal growth temperature, and a different salt tolerance.

Appl Environ Microbiol, 1998 Jun, 64(6), 2126 - 32
Low-frequency horizontal transfer of an element containing the chlorocatechol degradation genes from Pseudomonas sp . strain B13 to Pseudomonas putida F1 and to indigenous bacteria in laboratory-scale activated-sludge microcosms; Ravatn R et al.; The possibilities for low-frequency horizontal transfer of the self-transmissible chlorocatechol degradative genes (clc) from Pseudomonas sp . strain B13 were investigated in activated-sludge microcosms . When the clc genes were transferred into an appropriate recipient bacterium such as Pseudomonas putida F1, a new metabolic pathway for chlorobenzene degradation was formed by complementation which could be selected for by the addition of mono- or 1, 4-dichlorobenzene (CB) . Under optimized conditions with direct donor-recipient filter matings, very low transfer frequencies were observed (approximately 3.5 x 10(-8) per donor per 24 h) . In contrast, in matings on agar plate surfaces, transconjugants started to appear after 8 to 10 days, and their numbers then increased during prolonged continuous incubation with CB . In activated-sludge microcosms, CB-degrading (CB+) transconjugants of strain F1 which had acquired the clc genes were detected but only when strain B13 cell densities of more than 10(5) CFU/ml could be maintained by the addition of its specific growth substrate, 3-chlorobenzoate (3CBA) . The CB+ transconjugants reached final cell densities of between 10(2) and 10(3) CFU/ml . When strain B13 was inoculated separately (without the designated recipient strain F1) into an activated-sludge microcosm, CB+ transconjugants could not be detected . However, in this case a new 3CBA-degrading strain appeared which had acquired the clc genes from strain B13 . The effects of selective substrates on the survival and growth of and gene transfer between bacteria degrading aromatic pollutants in a wastewater ecosystem are discussed.

Appl Environ Microbiol, 1998 May 1, 64(5), 1700 - 7
Improved Most-Probable-Number Method To Detect Sulfate-Reducing Bacteria with Natural Media and a Radiotracer
Vester F, Ingvorsen K.
A greatly improved most-probable-number (MPN) method for selective enumeration of sulfate-reducing bacteria (SRB) is described . The method is based on the use of natural media and radiolabeled sulfate (35SO42-) . The natural media used consisted of anaerobically prepared sterilized sludge or sediment slurries obtained from sampling sites . The densities of SRB in sediment samples from Kysing Fjord (Denmark) and activated sludge were determined by using a normal MPN (N-MPN) method with synthetic cultivation media and a tracer MPN (T-MPN) method with natural media . The T-MPN method with natural media always yielded significantly higher (100- to 1,000-fold-higher) MPN values than the N-MPN method with synthetic media . The recovery of SRB from environmental samples was investigated by simultaneously measuring sulfate reduction rates (by a 35S-radiotracer method) and bacterial counts by using the T-MPN and N-MPN methods, respectively . When bacterial numbers estimated by the T-MPN method with natural media were used, specific sulfate reduction rates (qSO42-) of 10(-14) to 10(-13) mol of SO42- cell-1 day-1 were calculated, which is within the range of qSO42- values previously reported for pure cultures of SRB (10(-15) to 10(-14) mol of SO42- cell-1 day-1) . qSO42- values calculated from N-MPN values obtained with synthetic media were several orders of magnitude higher (2 x 10(-10) to 7 x 10(-10) mol of SO42- cell-1 day-1), showing that viable counts of SRB were seriously underestimated when standard enumeration media were used . Our results demonstrate that the use of natural media results in significant improvements in estimates of the true numbers of SRB in environmental samples.

Appl Environ Microbiol, 1998 Apr, 64(4), 1203 - 9
Population dynamics of phenol-degrading bacteria in activated sludge determined by gyrB-targeted quantitative PCR; Watanabe K et al.; A method for quantifying bacterial populations introduced into an activated-sludge microbial community is described . The method involves extraction of DNA from activated sludge, appropriate dilution of the extracted DNA with DNA extracted from nonintroduced activated sludge, PCR amplification of a gyrB gene fragment from the introduced strain with a set of strain-specific primers, and quantification of the electrophoresed PCR product by densitometry . The adequacy of the method was examined by analyzing the population dynamics of two phenol-degrading bacteria, Pseudomonas putida BH and Comamonas sp . strain E6, that had been introduced into phenol-digesting activated sludge . The density of each of the two populations determined by the PCR method immediately after the introduction was consistent with the density estimated from a plate count of the inoculum . This quantitative PCR method revealed different population dynamics for the two strains in the activated sludge under different phenol-loading conditions . The behavior of both of these strains in the activated sludge reflected the growth kinetics of the strains determined in laboratory axenic cultures.

Ecotoxicol Environ Saf, 1998 Feb, 39(2), 112 - 9
Structure- and property-activity relationship models for prediction of microbial toxicity of organic chemicals to activated sludge; Nirmalakhandan N et al.; Two quantitative structure-activity relationship (QSAR) and two quantitative property-activity relationship (QPAR) models reported in the literature for predicting toxicity of synthetic organic chemicals to activated sludge microorganisms are summarized and compared . The QSAR models were developed using solvatochromic parameters and molecular connectivity indices; the QPAR models, using octanol-water partition coefficient and aqueous solubility . Experimental data on 16 chemicals not used in developing the above models are used to compare and evaluate the predictive ability of these QSAR/QPAR models . Based on the quality of the original models, their predictions, ease of application, and availability of model parameters, molecular connectivity indices and log P appear to be the most suitable in toxicity predictions.

Microbiology, 1998 Feb, 144 ( Pt 2), 519 - 28
Floc stability and adhesion of green-fluorescent-protein-marked bacteria to flocs in activated sludge; Olofsson AC et al.; Wastewater is often treated using the activated sludge process . Flocculation and subsequent sedimentation of flocs are vital steps in this process that have direct influence on the quality of the effluent water from wastewater treatment plants . Since cells that remain free-living will decrease the quality of the effluent water it is important to understand the mechanisms of bacterial adhesion to flocs . The green fluorescent protein (GFP) was used as a cellular marker to study bacterial adhesion to activated sludge flocs in situ in sludge liquor . Cell surface hydrophobicity (CSH) was shown to be an important factor that determined the relative bacterial adhesion potential . High CSH correlated with high numbers of attached cells . However, the absolute adhesion of two test bacteria to different sludge flocs varied and could not be explained by the floc characteristics . Confocal laser scanning microscopy of GFP-marked cells showed their position in the floc matrix in situ . Hydrophobic cells attached not only on the surface but also within the floc, whereas hydrophilic cells did not . This indicates that cells may penetrate the flocs through channels and pores and increase the effective surface, which in turn makes the clarification of the wastewater effluent more efficient . The addition of polymers is common practice in wastewater treatment and was shown to increase bacterial adhesion to the flocs . A decrease in surface tension caused by addition of DMSO decreased adhesion, indicating the detrimental effect of surfactants on flocculation . An understanding of basic bacterial adhesion and aggregation mechanisms is important for the management and control of biotechnological wastewater treatment.

Ann N Y Acad Sci, 1997 Nov 21, 829, 118 - 34
Microbial degradation and treatment of polycyclic aromatic hydrocarbons and plasticizers; Kurane R; Rhodococcus erytropolis and Pseudomonas sp . rapidly degrade many kinds of polycyclic aromatic hydrocarbon (PAH) compounds such as phenanthrene and phthalate esters such as di(2-ethylhexyl) phthalate, used as plasticizers . These compounds were efficiently removed from wastewater by inoculating viable cells of Rhodococcus erythropolis and Pseudomonas sp . into activated sludge as a biological treatment system . The rapid PCR method and fluorescent antibody techniques were successfully applied for tracing the specified microorganisms, which were inoculated into a mixed culture system . The relationship of microflora to the removal rate of these compounds such as phthalate esters in inoculated biological treatment systems was examined . The metabolic pathway was investigated and enzymes were purified.

Microbiology, 1998 Jan, 144 ( Pt 1), 249 - 59
In situ identification of nocardioform actinomycetes in activated sludge using fluorescent rRNA-targeted oligonucleotide probes; Schuppler M et al.; Hitherto, few environmental samples have been investigated by a 'full cycle rRNA analysis' . Here the results of in situ hybridization experiments with specific rRNA-targeted oligonucleotide probes developed on the basis of new sequences derived from a previously described comparative 16S rRNA analysis of nocardioform actinomycetes in activated sludge are reported . Application of the specific probes enabled identification and discrimination of the distinct populations of nocardioform actinomycetes in activated sludge . One of the specific probes (DLP) detected rod-shaped bacteria which were found in 13 of the 16 investigated sludge samples from various wastewater treatment plants, suggesting their importance in the wastewater treatment process . Another probe (GLP2) hybridized with typically branched filaments of nocardioforms mainly found in samples from enhanced biological phosphorus removal plants, suggesting that these bacteria are involved in sludge foaming . The combination of in situ hybridization with fluorescently labelled rRNA-targeted oligonucleotide probes and confocal laser scanning microscopy improved the detection of nocardioform actinomycetes, which often showed only weak signals inside the activated-sludge flocs.

Appl Environ Microbiol, 1998 Jan, 64(1), 159 - 65
Degradation of morpholine by an environmental Mycobacterium strain involves a cytochrome P-450; Poupin P et al.; A Mycobacterium strain (RP1) was isolated from a contaminated activated sludge collected in a wastewater treatment unit of a chemical plant . It was capable of utilizing morpholine and other heterocyclic compounds, such as pyrrolidine and piperidine, as the sole source of carbon, nitrogen, and energy . The use of in situ 1H nuclear magnetic resonance (1H NMR) spectroscopy allowed the determination of two intermediates in the biodegradative pathway, 2-(2-aminoethoxy)acetate and glycolate . The inhibitory effects of metyrapone on the degradative abilities of strain RP1 indicated the involvement of a cytochrome P-450 in the biodegradation of morpholine . This observation was confirmed by spectrophotometric analysis and 1H NMR . Reduced cell extracts from morpholine-grown cultures, but not succinate-grown cultures, gave rise to a carbon monoxide difference spectrum with a peak near 450 nm, which indicated the presence of a soluble cytochrome P-450 . 1H NMR allowed the direct analysis of the incubation medium containing metyrapone, a specific inhibitor of cytochrome P-450 . The inhibition of morpholine degradation was dependent on the morpholine/metyrapone ratio . The heme-containing monooxygenase was also detected in pyrrolidine- and piperidine-grown cultures . The abilities of different compounds to support strain growth or the induction of a soluble cytochrome P-450 were assayed . The results suggest that this enzyme catalyzes the cleavage of the C-N bond of the morpholine ring.

J Appl Microbiol, 1997 Nov, 83(5), 561 - 8
Biodegradation studies of polyaromatic hydrocarbons in aqueous media; Sepic E et al.; Sixteen bacterial strains isolated from an activated sludge and Mycobacterium ssp . PYR-1 were tested for their ability to degrade polyaromatic hydrocarbons (PAHs) . The bacterial strains Pasteurella ssp . (B-2) and Mycobacterium ssp . PYR-1 (AM) showed a high biodegradation potential of three- and four-ring PAHs . Bacterial strain AM was able to degrade up to 80% of three and four-ring PAHs (phenanthrene, fluoranthene and pyrene) within the first month of incubation, while the bacterial strain B-2 achieved the same biodegradation in 2 months . The metabolic pathway of PAH degradation was studied using fluoranthene and the bacterial strain AM . Ninety per cent of fluoranthene was biodegraded within the first 9 d of incubation when applied as a single substrate . Retention factor values from thin-layer chromatography studies, gas chromatography with mass selective detection and tandem mass spectrometry identified 9-fluorenone-1-carboxylic acid as one of the stable metabolic products and from this a fluoranthene biodegradation pathway is proposed.

Biosci Biotechnol Biochem, 1997 Nov, 61(11), 1957 - 9
Biodegradabilities of ethylenediamine-N,N'-disuccinic acid (EDDS) and other chelating agents; Takahashi R et al.; Biodegradabilities of chelating agents were tested with activated sludge . Ethylenediaminetetraacetic acid (EDTA) remained intact in the effluent even after acclimation for 100 days, but propanediamine-N,N'-disuccinic acid (PDDS) and nitrilotriacetic acid (NTA) were biodegraded after acclimation for 5 and 23 days, respectively . Optical isomers of ethylenediamine-N,N'-disuccinic acid (EDDS) had different biodegradabilities: SS- and RS-isomers were susceptible to biodegradation, but the RR-isomer was resistant . SS-isomer was degraded even by activated sludge without acclimation.

Appl Microbiol Biotechnol, 1997 Oct, 48(4), 441 - 8
Biodegradation of the pesticide 4,6-dinitro-ortho-cresol by microorganisms in batch cultures and in fixed-bed column reactors; Gisi D et al.; A mixed culture of microorganisms able to utilize 4,6-dinitro-ortho-cresol (DNOC) as the sole source of carbon, nitrogen and energy was isolated from soil contaminated with pesticides and from activated sludge . DNOC was decomposed aerobically in batch cultures as well as in fixed-bed column reactors . Between 65% and 84% of the substrate nitrogen was released as nitrate into the medium, and 61% of the carbon from uniformly 14C-labelled DNOC was recovered as 14CO2 . The mixed microbial culture also decomposed 4-nitrophenol and 2,4-dinitrophenol but not 2,3-dinitrophenol, 2,6-dinitrophenol, 2,4-dinitrotoluene, 2,4-dinitrobenzoic acid or 2-sec-butyl-4,6-dinitrophenol (Dinoseb) . Maximal degradation rates for DNOC by the bacterial biofilm immobilized on glass beads in fixed-bed column reactors were 30 mmol day-1 (1 reactor volume)-1, leaving an effluent concentration of less than 5 micrograms l-1 DNOC in the outflowing medium . The apparent Ks value of the immobilized mixed culture for DNOC was 17 microM . Degradation was inhibited at DNOC concentrations above 30 microM and it ceased at 340 microM, possibly because of the uncoupling action of the nitroaromatic compound on the cellular energy-transducing mechanism.

Appl Environ Microbiol, 1997 Nov, 63(11), 4516 - 22
Characterization of microbial diversity by determining terminal restriction fragment length polymorphisms of genes encoding 16S rRNA; Liu WT et al.; A quantitative molecular technique was developed for rapid analysis of microbial community diversity in various environments . The technique employed PCR in which one of the two primers used was fluorescently labeled at the 5' end and was used to amplify a selected region of bacterial genes encoding 16S rRNA from total community DNA . The PCR product was digested with restriction enzymes, and the fluorescently labeled terminal restriction fragment was precisely measured by using an automated DNA sequencer . Computer-simulated analysis of terminal restriction fragment length polymorphisms (T-RFLP) for 1,002 eubacterial sequences showed that with proper selection of PCR primers and restriction enzymes, 686 sequences could be PCR amplified and classified into 233 unique terminal restriction fragment lengths or "ribotypes." Using T-RFLP, we were able to distinguish all bacterial strains in a model bacterial community, and the pattern was consistent with the predicted outcome . Analysis of complex bacterial communities with T-RFLP revealed high species diversity in activated sludge, bioreactor sludge, aquifer sand, and termite guts; as many as 72 unique ribotypes were found in these communities, with 36 ribotypes observed in the termite guts . The community T-RFLP patterns were numerically analyzed and hierarchically clustered . The pattern derived from termite guts was found to be distinctly different from the patterns derived from the other three communities . Overall, our results demonstrated that T-RFLP is a powerful tool for assessing the diversity of complex bacterial communities and for rapidly comparing the community structure and diversity of different ecosystems.

Appl Environ Microbiol, 1997 Nov, 63(11), 4223 - 31
Flow sorting of microorganisms for molecular analysis; Wallner G et al.; Not only classical cultivation-based methods but also the new molecular approaches may result in incomplete and selective information on the natural diversity of microbial communities . Flow sorting of microorganisms from environmental samples allows the deliberate selection of cell populations of interest from highly diverse systems for molecular analysis . Several cellular parameters that can be measured by flow cytometry are useful as sort criteria . Here, we report sorting of bacteria from activated sludge, lake water, and lake sediment according to differences in light scattering, DNA content, and/or affiliation to certain phylogenetic groups as assessed by fluorescein-labeled, rRNA-targeted oligonucleotide probes . Microscopy of the sorted cells showed that populations of originally low abundance could be strongly enriched by flow sorting (up to 280-fold), depending on the original abundance of the cells of interest and the type of sample sorted . The purity of the cells of interest could be further increased by repeated sorting, but this increase was limited by cell aggregation in the case of activated-sludge samples . It was possible to amplify almost full-length 16S ribosomal DNA (rDNA) fragments from sorted microbial cells by PCR, even after fixation with paraformaldehyde and in situ hybridization . Dot blot hybridization and sequencing demonstrated that most of the amplified rDNA originated from those cells that had been selected for by flow sorting . Comparative analysis of 16S rDNA sequences revealed previously unknown species of magnetotactic or activated-sludge bacteria.

Ecotoxicol Environ Saf, 1997 Aug, 37(3), 229 - 37
Environmental fate assessment of two synthetic polycarboxylate polymers; Jop KM et al.; In order to estimate the proportion which may enter the aquatic environment and characterize exposure potential, the environmental fate properties of two polycarboxylate polymers in activated sludge were determined . The polycarboxylates studied were a polymer emulsion (PE), a high-molecular-weight polymer (MW 50,000-60,000), and a resin polymer (RP), a low-molecular-weight polymer (MW 4500 to 9000) . Both polymers exhibited a high degree of sorption to sludge solids in a series of sorption/ desorption studies, indicating a high potential for removal during wastewater treatment . In isotherm tests, the adsorption coefficient, Koc, was 1060 and 2730 for the RP and the PE, respectively . The biodegradation of the two polymers was measured under aerobic conditions in a 60-day semicontinuous activated sludge test and in a 60-day modified Sturm test using 14C-labeled compounds . In both studies, polymers accumulated in sludge solids over time and there was no evidence of significant biodegradation, although small amounts of radiolabeled CO2 were produced, suggesting the potential for biodegradation . Testing confirmed that the lack of biodegradation was not due to inhibition of microbial respiration by the polymers . High removals of PE and RP during wastewater treatment were confirmed in a field study at a facility receiving polymer inputs from households and manufacturing plants.

FEMS Microbiol Lett, 1997 Aug 1, 153(1), 181 - 90
Detection and in situ identification of representatives of a widely distributed new bacterial phylum; Ludwig W et al.; 16S rRNA gene libraries were prepared by polymerase chain reaction amplification and cloning from soil samples taken periodically from a field with genetically modified plants . Sequence analyses of the cloned rDNAs indicated that 140 of them clustered apart from known bacterial phyla . Based on 31 full sequences a new phylum could be defined . It includes Holophaga foetida, 'Geothrix fermentans' and Acidobacterium capsulatum as the only cultured species so far . Therefore, this line of descent was named the Holophagal Acidobacterium phylum . About 50 published partial sequences of cloned rDNAs retrieved from soil, freshwater sediments or activated sludge from different continents indicate the occurrence of further representatives of this phylum . Two specific hybridization probes were constructed for members of one of four subclusters . A careful data analysis revealed the importance and problems of identifying and dealing with artefacts such as chimeric structure when defining new phylogenetic groups based mainly upon cloned amplified rDNAs . For the first time, the presence of bacterial cells representing this group could be shown in soil, sediment, activated sludge and lake snow by in situ hybridization.

FEMS Microbiol Lett, 1997 Jul 15, 152(2), 299 - 306
Determination of bacterial cell surface hydrophobicity of single cells in cultures and in wastewater in situ; Zita A et al.; Bacterial cell surface hydrophobicity is one of the most important factors that influence bacterial adhesion . A new method microsphere adhesion to cells, for measuring bacterial cell surface hydrophobicity was developed . Microsphere adhesion to cells is based on microscopic enumeration of hydrophobic, fluorescent microspheres attaching to the bacterial surface . Cell surface hydrophobicity estimated by microsphere adhesion to cells correlates well with adhesion of bacteria to hydrocarbons or hydrophobic interaction chromatography for a set of hydrophilic and hydrophobic bacteria (linear correlation coefficients, R2, were 0.845 and 0.981 respectively) . We also used microsphere adhesion to cells to investigate the in situ properties of individual free-living bacteria directly in activated sludge . Results showed that the majority of the bacteria were hydrophilic, indicating the importance of cell surface hydrophobicity for bacterial adhesion in sludge, and for the overall success of the wastewater treatment process.

Appl Microbiol Biotechnol, 1997 Jul, 48(1), 73 - 9
Comparison of partial 16S rRNA gene sequences obtained from activated sludge bacteria; Vainio EJ et al.; The cultivated and uncultivated bacterial communities of an activated sludge plant were studied . Two samples were taken and a total of 516 bacterial isolates were classified into groups using their whole-cell protein patterns . The distribution of bacteria into protein-pattern groups differed significantly between the two samples, suggesting variation in culturable bacterial flora . Partial 16S rRNA gene sequences were determined for representatives of the commonest protein-pattern groups . Most of the sequences obtained were previously unknown, but relatively closely related to known sequences of organisms belonging to the alpha, beta or gamma subclasses of the proteobacteria, the first two subclasses being predominant . This classification of bacteria isolated on a diluted nutrient-rich medium differed from recent culture-dependent studies using nutrient-rich media . The uncultivated bacterial community was studied by analyzing ten partial 16S rRNA gene sequences cloned directly from activated sludge . None of the cloned sequences was identical to those determined for culturable organisms; or to those in the GenBank database . They were, however, related to the alpha or beta subclasses of the proteobacteria, or to the gram-positive bacteria with a high G + C DNA content.

Lett Appl Microbiol, 1997 Jul, 25(1), 63 - 9
The characterization and description of representatives of 'G' bacteria from activated sludge plants; Blackall LL et al.; The name Tetracoccus cechii is proposed for two strains of the tetrad arranged cocci, previously known as 'G' bacteria, which were isolated from laboratory scale activated sludge plants in the Czech Republic and in Italy . They were morphologically, phenotypically and phylogenetically characterized and found to comprise a novel lineage in the alpha-3 group of the proteobacterial phylum in the domain Bacteria . The strains are Gram-negative and produce intracellular inclusions of poly-beta-hydroxybutyrate . Although commonly seen in activated sludge mixed liquor as cocci 1-2 microns in diameter, arranged in tetrads, in pure culture they can also grow in amorphous aggregations and the cells are generally more variable in their size and shape with coccobacilli as well as cocci being present . They are not able to grow phototrophically, nor can they reduce nitrate beyond nitrite nor grow anaerobically . The closest phylogenetic neighbours of T . cechii are Rhodobacter sphaeroides and R . capsulatus which are 93% similar by 16S rDNA comparison . Tetracoccus cechii is oxidase- and catalase-positive, non-motile and has an optimal growth temperature between 25 degrees and 35 degrees C . The 16S rRNA of T . cechii has a 21 nucleotide deletion in the V9 region (Escherichia coli positions 1258-1278) and this feature is a unique molecular synapomorphy in the alpha-3 group.

FEMS Microbiol Lett, 1997 Jul 1, 152(1), 45 - 9
Partially oxidized polycyclic aromatic hydrocarbons show an increased bioavailability and biodegradability; Meulenberg R et al.; Polycyclic aromatic hydrocarbons have a low water solubility and tend to adsorb on soil particles, which both result in slow bioremediation processes . Many microorganisms, known for their ability to degrade polycyclic aromatic hydrocarbons, only partially oxidize these compounds . White rot fungi, for instance, convert polycyclic aromatic hydrocarbons to more water soluble and bioavailable products . Polycyclic aromatic hydrocarbon metabolites were more readily mineralized by natural mixed bacterial cultures, like activated sludge and soil, than the parent polycyclic aromatic hydrocarbon compounds . These results suggest that sequential breakdown by white rot fungi followed by indigenous bacteria leads to an effective polycyclic aromatic hydrocarbon bioremediation process.

Int J Syst Bacteriol, 1997 Jul, 47(3), 727 - 34
Amaricoccus gen . nov., a gram-negative coccus occurring in regular packages or tetrads, isolated from activated sludge biomass, and descriptions of Amaricoccus veronensis sp . nov., Amaricoccus tamworthensis sp . nov., Amaricoccus macauensis sp . nov., and Amaricoccus kaplicensis sp . nov; Maszenan AM et al.; Three isolates of gram-negative bacteria, strains Ben 102T, Ben 103T, and Ben 104T, were obtained in pure culture by micromanipulation from activated sludge biomass from wastewater treatment plants in Italy, Australia, and Macau, respectively . These isolates all had a distinctive morphology; the cells were cocci that usually were arranged in tetrads . Based on this criterion, they resembled other bacteria from activated sludge previously called "G" bacteria . On the basis of phenotypic characteristics and the results of 16S ribosomal DNA sequence analyses, the three isolates were very similar to each other, but were sufficiently different from their closest phylogenetic relatives (namely, the genera Rhodobacter, Rhodovulum, and Paracoccus in the alpha subdivision of the Proteobacteria) to be placed in a new genus, Amaricoccus gen . nov . Each of the three isolates represents a new species of the genus Amaricoccus; strains Ben 102T, Ben 103T, and Ben 104T are named Amaricoccus veronensis, Amaricoccus tamworthensis, and Amaricoccus macauensis, respectively . An isolate designated Ben 101T, which was isolated independently by Cech and Hartman in Kaplice, Czech Republic, was also characterized and belongs to the same genus . We propose that the isolate of Cech and Hartman should be placed in another new species, Amaricoccus kaplicensis.

Appl Environ Microbiol, 1997 Jul, 63(7), 2884 - 96
Phylogenetic analysis and in situ identification of bacteria in activated sludge; Snaidr J et al.; The bacterial community structure of activated sludge of a large municipal wastewater treatment plant was investigated by use of the rRNA approach . Almost-full-length genes coding for the small-subunit rRNA (rDNA) were amplified by PCR and subsequently cloned into the pGEM-T vector . Clones were screened by dot blot hybridization with group-specific oligonucleotide probes . The phylogenetic affiliations of clones were compared with the results obtained with the original sample by in situ hybridization with fluorescently labeled, rRNA-targeted oligonucleotide probes and found to be in general agreement . Twenty-five 16S rDNA clones were fully sequenced, 11 were almost fully (> 80%) sequenced, and 27 were partially sequenced . By comparative sequence analyses, the majority of the examined clones (35 of 67) could be affiliated with the beta subclass of the class Proteobacteria . The gamma and alpha subclasses of Proteobacteria were represented by 13 and 4 clones, respectively . Eight clones grouped with the epsilon group of Proteobacteria, and five clones grouped with gram-positive bacteria with a low DNA G+C content . The 16S rDNA of two clones showed similarity with 16S rDNA genes of members of the phyla Chlamydiae and Planctomyces . 16S rRNA-targeted oligonucleotide probes were designed and used for the enumeration of the respective bacteria . Interestingly, potentially pathogenic representatives of the genus Arcobacter were present in significant numbers (4%) in the activated sludge sample examined . Pairs of probes targeted to the 5' and 3' regions were used for detection of chimeric sequences by in situ hybridization . Two clones could be identified as chimera by applying such a pair of probes.

Sci Total Environ, 1997 Apr 30, 197(1-3), 149 - 60
Land application of sewage sludge in China; Wang MJ; Land application of sewage sludge in China is thoroughly reviewed . Operation of sewage sludge disposal is usually expensive and/or easy to contaminate the environment . In China, most sewage sludge has not been treated and disposed of properly, resulting in environmental pollution and potential exposure to humans . In the near future, sewage sludge production in China will increase rapidly together with the dramatic increase of municipal wastewater treatment ratio (treated/produced), implying that the problem of sewage sludge disposal will become more serious and unavoidable . Proper land utilization of stabilized sewage sludge can make a positive contribution to agriculture, forestry, horticulture and city development . Heavy metals, organic pollutants and pathogens concentrated in sewage sludge during wastewater treatment are the main obstacles to land application of sewage sludge . To promote land application of sewage sludge in China, a statewide survey of sewage sludge production and harmful components in sewage sludge should be carried out . Sewage sludge management and technologies for sludge treatment and disposal suitable to Chinese conditions should be paid more attention.

J Ind Microbiol Biotechnol, 1997 Apr, 18(4), 235 - 40
Microbial biodegradation of organic wastes containing surfactants in a continuous-flow reactor; Konopka A et al.; In a continuous flow bioreactor seeded with microbes from municipal activated sludge, complete organic carbon oxidation of simulated graywater (wastewater produced in human residences, excluding toilet wastes) was achieved at dilution rates up to 0.36 h-1 in the presence of 64.1 microM linear alkylbenzenesulfonate (LAS) L-1 . At LAS concentrations of 187 microM, the system functioned only at dilution rates up to 0.23 h-1, and the biomass yield was two-fold lower . There were physiological changes in the microbial communities under different operating conditions, as measured by specific contents of ATP and extracellular hydrolases as well as the respiratory potential of the biomass . LAS inhibited the activity of LAS-degrading microbes at >150 microM LAS, and the activity of other microbes at >75 microM LAS . Chemical analysis of graywater indicated that samples consisted primarily of biological polymers (proteins and polysaccharides) and lower concentrations of surfactants . Biological remediation of graywater is possible, although treatment efficiency is influenced by the operating conditions and wastestream composition.

What Is Biofilter?, What is Food Microbiology?, What Is Protein?, What Is Growth Medium?, What Is Genetics?, c, Microbiology, o, Bacteria, s, Bacteriology, e, Microbe, r, Microorganisms, a, Bacteriological, a, Streptococci, i, Prokaryotes, s, Cell cultures, c, Microbial, c, Gram positive, s, Yeasts, r, Lactobacillus, r, Microbiological, e, Microbial, i, Pasteurella, o, Escherichia coli, s, Antimicrobial, e, Phage, o, Salmonella, r, S. cerevisiae, o, Antibiotics, n, Clostridia, a, Bacteriological, r, Microbial, c, Erythromycin

Scientific Publications - Work Done by Microbiology Reader Bioscreen C
Agricultural Microbiology Anaerobic Microbiology Antimicrobial Susceptibility Artificial Atmosphere Bioassay of Antibiotics Biofilm Microbiology Bioreactor Technology Biotechnology Cell Biology Clinical Microbiology Environmental Microbiology Experiments with Yeast	Fermentation Food Microbiology Functional Genomics Gene Technology Growth Media Development Growth Rate and Lag Time Industrial Microbiology Medical/Pharmaceutical Field Microbiological Assay Microbiological Research Microbiology of Cosmetics go to a specific theme...	Military Microbiology Molecular Microbiology Mutagenicity and Genotoxicity Oral Microbiology Patents Postantibiotic Studies Soil Microbiology Spore Microbiology Veterinary Microbiology Waste/Wastewater Treatment Water Microbiology Wine Microbiology

� 2005 Transgalactic Ltd (manufacturer of Bioscreen C software) | Privacy Statement | P.O. Box 1393, 00101 Helsinki, Finland, phone: +358 9 85172920, fax: +358 9 8749481, e-mail: microbiology@bionewsonline.com

Last modified: May 25, 2005