Activated Sludge (activated + sludge)

Distribution by Scientific Domains
Distribution within Life Sciences

Terms modified by Activated Sludge

  • activated sludge process
  • activated sludge system

  • Selected Abstracts


    Effect of ethoxylate number and alkyl chain length on the pathway and kinetics of linear alcohol ethoxylate biodegradation in activated sludge

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2004
    Nina R. Itrich
    Abstract Batch activated-sludge die-away studies were conducted with various pure homologs to determine the effect of ethoxylate number and alkyl chain length on the kinetics of primary and ultimate biodegradation of linear alcohol ethoxylates. The 14C-(ethoxylate) homologs C14E1, C14E3, C14E6, and C14E9 were used to investigate the effect of ethoxylate number, and 14C-(ethoxylate) homologs C12E6, C14E6, and C16E6 were used to examine the effect of chain length. Activated sludge was dosed with a trace concentration (0.2 ,M) of each homolog, and the disappearance of parent, formation of metabolites, production of 14CO2, and uptake into solids were monitored with time. Ethoxylate number had little effect on the first-order decay rates for primary biodegradation, which ranged from 61 to 78 h,1. However, alkyl chain length had a larger effect, with the C16 chain-length homolog exhibiting a slower rate of parent decay (18 h,1) compared to its corresponding C12 and C14 homologs (61,69 h,1). Ethoxylate number affected the mechanism of biodegradation, with fission of the central ether bond to yield the corresponding fatty alcohol and (poly)ethylene glycol group increasing in dominance with increasing ethoxylate number. Based upon the measured rates of primary biodegradation, removal of parent during activated-sludge treatment was predicted to range between 99.7 and 99.8% for all homologs except C16E6, which had a predicted removal of 98.9%. Based upon the measured rates of ultimate biodegradation, removal of ethoxylate-containing metabolites was predicted to exceed 83% for all homologs. These predictions corresponded closely with previously published removal measurements in laboratory continuous activated-sludge systems and actual treatment plants. [source]


    Detection of denitrification genes by in situ rolling circle amplification-fluorescence in situ hybridization to link metabolic potential with identity inside bacterial cells

    ENVIRONMENTAL MICROBIOLOGY, Issue 9 2010
    Tatsuhiko Hoshino
    Summary A target-primed in situ rolling circle amplification (in situ RCA) protocol was developed for detection of single-copy genes inside bacterial cells and optimized with Pseudomonas stutzeri, targeting nitrite and nitrous oxide reductase genes (nirS and nosZ). Two padlock probes were designed per gene to target both DNA strands; the target DNA was cut by a restriction endonuclease close to the probe binding sites, which subsequently were made accessible by 5,-3, exonucleolysis. After hybridization, the padlock probe was circularized by ligation and served as template for in situ RCA, primed by the probe target site. Finally, the RCA product inside the cells was detected by standard fluorescence in situ hybridization (FISH). The optimized protocol showed high specificity and signal-to-noise ratio but low detection frequency (up to 15% for single-copy genes and up to 43% for the multi-copy 16S rRNA gene). Nevertheless, multiple genes (nirS and nosZ; nirS and the 16S rRNA gene) could be detected simultaneously in P. stutzeri. Environmental application of in situ RCA-FISH was demonstrated on activated sludge by the differential detection of two types of nirS -defined denitrifiers; one of them was identified as Candidatus Accumulibacter phosphatis by combining in situ RCA-FISH with 16S rRNA-targeted FISH. While not suitable for quantification because of its low detection frequency, in situ RCA-FISH will allow to link metabolic potential with 16S rRNA (gene)-based identification of single microbial cells. [source]


    Stable augmentation of activated sludge with foreign catabolic genes harboured by an indigenous dominant bacterium

    ENVIRONMENTAL MICROBIOLOGY, Issue 10 2002
    Kazuya Watanabe
    Summary Comamonas sp. rN7 is a phenol-degrading bacterium that represents the dominant catabolic population in activated sludge. The present study examined the utility of this bacterium for establishing foreign catabolic genes in phenol-digesting activated sludge. The phc genes coding for phenol hydroxylase and its transcriptional regulators of C. testosteroni R5 were integrated into the chromosome of strain rN7. The specific phenol-oxygenating activity of a resultant transformant designated rN7(R503) was three times higher than the activity of strain rN7, and the phc genes were stably inherited by rN7(R503) grown in a non-selective laboratory medium. Inoculation of phenol-acclimatized activated sludge with rN7(R503) resulted in a high phenol-oxygenating activity and improved resistance to phenol-shock loading compared to sludge inoculated with either no cells, rN7 or R5. Quantitative competitive polymerase chain reaction (PCR) showed that the phc genes were retained in the rN7(R503)-inoculated sludge at a density of more than 108 copies per ml of mixed liquor for more than 35 days, whereas those in the R5-inoculated sludge disappeared rapidly. No transfer of the phc genes to other indigenous populations was apparent in the rN7(R503)-harbouring sludge. From these results, we concluded that the phenol treatment of the activated sludge was enhanced by the phc genes harboured by the rN7(R503) population. This study suggests a possible bioaugmentation strategy for stably utilizing foreign catabolic genes in natural ecosystems. [source]


    Design and application of oligonucleotide probes for fluorescent in situ identification of the filamentous bacterial morphotype Nostocoida limicola in activated sludge

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


    Impact of five selected xenobiotics on isolated ammonium oxidizers and on nitrifying activated sludge

    ENVIRONMENTAL TOXICOLOGY, Issue 4 2006
    S. N. Dokianakis
    Abstract Sewage treatment plants (STPs) are usual receptors of xenobiotic compounds that have to be cotreated with municipal wastewaters before being discharged to the water environment. The presence of organic contaminants, such as surfactants, polycyclic aromatic hydrocarbons (PAHs), phthalates, and their primary degradation products in the influents of STPs may inhibit irreversibly sensitive biological processes, such as nitrification. The first step of nitrification, i.e., the oxidation of ammonium to nitrite (nitritification), is particularly sensitive. Inhibition of this step under uncontrolled conditions may completely inhibit biological nitrogen removal. The aim of this work was to study the possible inhibitory effect of five selected xenobiotics on (a) a mixed culture of ammonium-oxidizing bacteria isolated from activated sludge and (b) nitrifying activated sludge directly. The xenobiotics that were tested include nonylphenols (NP), nonylphenolethoxylates (NPEO), linear alkylbenzene sulfonates (LAS), di(2-ethylhexyl) phthalate (DEHP), as a representative phthalate ester, and the PAH phenanthrene. Remarkable inhibitory effects for all tested compounds were observed in this study even at xenobiotic concentrations as low as 1 mg/L. The observed inhibition of xenobiotics on nitrifying activated sludge was less pronounced, because of the masking effect exerted by the sludge flocs, but was still significant for many of the tested substances at concentrations up to 10 mg/L. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 310,316, 2006. [source]


    Effect of ethoxylate number and alkyl chain length on the pathway and kinetics of linear alcohol ethoxylate biodegradation in activated sludge

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2004
    Nina R. Itrich
    Abstract Batch activated-sludge die-away studies were conducted with various pure homologs to determine the effect of ethoxylate number and alkyl chain length on the kinetics of primary and ultimate biodegradation of linear alcohol ethoxylates. The 14C-(ethoxylate) homologs C14E1, C14E3, C14E6, and C14E9 were used to investigate the effect of ethoxylate number, and 14C-(ethoxylate) homologs C12E6, C14E6, and C16E6 were used to examine the effect of chain length. Activated sludge was dosed with a trace concentration (0.2 ,M) of each homolog, and the disappearance of parent, formation of metabolites, production of 14CO2, and uptake into solids were monitored with time. Ethoxylate number had little effect on the first-order decay rates for primary biodegradation, which ranged from 61 to 78 h,1. However, alkyl chain length had a larger effect, with the C16 chain-length homolog exhibiting a slower rate of parent decay (18 h,1) compared to its corresponding C12 and C14 homologs (61,69 h,1). Ethoxylate number affected the mechanism of biodegradation, with fission of the central ether bond to yield the corresponding fatty alcohol and (poly)ethylene glycol group increasing in dominance with increasing ethoxylate number. Based upon the measured rates of primary biodegradation, removal of parent during activated-sludge treatment was predicted to range between 99.7 and 99.8% for all homologs except C16E6, which had a predicted removal of 98.9%. Based upon the measured rates of ultimate biodegradation, removal of ethoxylate-containing metabolites was predicted to exceed 83% for all homologs. These predictions corresponded closely with previously published removal measurements in laboratory continuous activated-sludge systems and actual treatment plants. [source]


    Fate and effects of triclosan in activated sludge

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2002
    Thomas W. Federle
    Abstract Triclosan (TCS; 5-chloro-2-[2,4-dichloro-phenoxy]-phenol) is a widely used antimicrobial agent. To understand its fate during sewage treatment, the biodegradation and removal of TCS were determined in activated sludge. In addition, the effects of TCS on treatment processes were assessed. Fate was determined by examining the biodegradation and removal of TCS radiolabeled with 14C in the 2,4-dichlorphenoxy ring in laboratory batch mineralization experiments and bench-top continuous activated-sludge (CAS) systems. In batch experiments with unacclimated sludge, TCS was mineralized to 14CO2, but the total yield varied as a function of test concentration. Systems that were redosed with TCS exhibited more extensive and faster mineralization, indicating that adaptation was a critical factor determining the rate and extent of biodegradation. In a CAS study in which the influent level of TCS was incrementally increased from 40 ,g/L to 2,000 ,g/L, removal of the parent compound exceeded 98.5% and removal of total radioactivity (parent and metabolites) exceeded 85%. Between 1.5 and 4.5% of TCS in the influent was sorbed to the wasted solids, whereas >94% underwent primary biodegradation and 81 to 92% was mineralized to CO2 or incorporated in biomass. Increasing levels of TCS in the influent had no major adverse effects on any wastewater treatment process, including chemical oxygen demand, biological oxygen demand, and ammonia removal. In a subsequent experiment, a CAS system, acclimated to TCS at 35 ,g/L, received two separate 4-h shock loads of 750 ,g/L TCS. Neither removal of TCS nor treatment processes exhibited major adverse effects. An additional CAS study was conducted to examine the removal of a low level (10 ,g/L) of TCS. Removal of parent equaled 94.7%, and biodegradation remained the dominant removal mechanism. A subsequent series of CAS experiments examined removal at four influent concentrations (7.5, 11, 20, and 50 ,g/L) of TCS and demonstrated that removal of parent ranged from 98.2 to 99.3% and was independent of concentration. Although TCS removal across all experiments appeared unrelated to influent concentration, removal was significantly correlated (r2 = 0.87) with chemical oxygen demand removal, indicating that TCS removal was related to overall treatment efficiency of specific CAS units. In conclusion, the experiments show that TCS is extensively biodegraded and removed in activated-sludge systems and is unlikely to upset sewage treatment processes at levels expected in household and manufacturing wastewaters. [source]


    Biodegradation of poly(tetramethylene succinate-cotetramethylene abdicate) and poly(tetramethylene succinate) through water-soluble products

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2001
    Eiichi Kitakuni
    Abstract 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%. [source]


    Toxic event detection by respirometry and adaptive principal components analysis

    ENVIRONMETRICS, Issue 6 2005
    Sébastien Le Bonté
    Abstract Two methods based on adaptive principal components analysis (APCA) are compared to extract, from primary measurements, information related to the changes of wastewater characteristics induced by variable weather conditions and/or to the presence of toxic substances. The primary measurements are activated sludge respiratory data obtained by short-term experiments in an on-line batch respirometer, combined with indirect information on soluble pollution (UV-visible absorbance, turbidity, pH, etc.) and wastewater flow rate. The Benchmark Simulation Model 1 (BSM1), which simulates the functioning of a large wastewater treatment plant by activated sludge, has been used to obtain large data sets and to test the proposed APCA method, which has then been applied to real wastewater characteristics. Copyright © 2005 John Wiley & Sons, Ltd. [source]


    Ecophysiology of the filamentous Alphaproteobacterium Meganema perideroedes in activated sludge

    FEMS MICROBIOLOGY ECOLOGY, Issue 1 2005
    Caroline Kragelund
    Abstract A comprehensive study of the ecophysiology of the filamentous Meganema perideroedes affiliated to the Alphaproteobacteria, possessing a "Nostocoida limicola Type II" filamentous morphology was conducted. This morphotype often causes serious bulking problems in activated sludge wastewater treatment plants, and hardly anything is known about its physiology. The study was carried out by applying a suite of in situ methods in an industrial activated sludge treatment plant with excessive growth of this species. The experiments revealed a very versatile organism able to take up a large variety of organic substrates under aerobic conditions. It had a remarkably high storage capacity forming polyhydroxyalkanoates from most substrates tested. When nitrate was present as e-acceptor, the number of substrates to be consumed by M. perideroedes was more restricted compared to aerobic conditions. With nitrite as e-acceptor, only acetate and glucose among the substrates tested could be assimilated and used for storage and possibly growth. This indicated that M. perideroedes might be able to denitrify under certain conditions, which is unusual for filamentous bacteria in activated sludge. No substrate uptake or storage was seen under anaerobic conditions. M. perideroedes was relatively hydrophobic, compared to other filamentous bacteria and microcolonies present in the sludge, indicating the presence of a hydrophobic sheath. Several excreted surface-associated exoenzymes were detected in the sludge, but M. perideroedes never showed any activity, except once after a breakdown in the production facility. This confirmed that M. perideroedes mainly grows on soluble substrates. Based on the studies of the ecophysiology of M. perideroedes, potential control strategies are suggested. [source]


    Molecular characterization of microbial community in nitrate-removing activated sludge

    FEMS MICROBIOLOGY ECOLOGY, Issue 2 2002
    Han-Woong Lee
    Abstract The microbial community composition and dominant denitrifying populations in high-nitrate-removing (CR-I) and low-nitrate-removing (CR-II) activated sludge from continuous bioreactors were investigated with most probable number (MPN) enumeration, fluorescence in situ hybridization (FISH) and 16S rDNA characterization. MPNs of nitrate-reducing bacteria of sludge CR-I and sludge CR-II were 2.82×107 and 2.69×104 colony-forming units ml,1, respectively. Eight denitrifying bacteria and two nitrate-reducing bacteria were isolated from sludge CR-I, and four denitrifying bacteria and three nitrate-reducing bacteria from sludge CR-II. Small subunit rDNA characterization of the isolates showed that the majority belonged to the genus Pseudomonas. By using FISH up to 76% (CR-I) and 52% (CR-II) of total 4,6-diamidino-2-phenylindole cell counts hybridized to the bacterial probe EUB338. Members of ,-Proteobacteria were the most abundant proteobacterial group in both sludges, accounting for up to 41.6% and 37.1% of those detected by EUB338, respectively, whereas a higher number of Cytophaga,Flexibacter cluster members were observed in CR-I sludge compared to CR-II sludge. In contrast with culture-based results, the numbers of rRNA group I Pseudomonads accounted for less than 0.01% of those detected by EUB338 in both sludges. Ribosomal DNA clone library analysis showed that the ,-Proteobacteria were also dominant in both sludges. In CR-I sludge, they were related to Zooglorea ramigera, Alcaligenes defragrans, denitrifying Fe-oxidizing bacteria and Dechlorimonas sp., whereas in CR-II sludge, they were related to Nitrosomonas sp. and Dechlorimonas agitatus. When this reactor was operated under anaerobic and anoxic conditions, nitrifying bacteria could adapt to the anoxic environment. We inferred that anaerobic ammonium oxidation and nitrite oxidation may occur in low-nitrate-removing sludge CR-II and inhibit denitrification. [source]


    Genetic characterization of the dibenzofuran-degrading Actinobacteria carrying the dbfA1A2 gene homologues isolated from activated sludge

    FEMS MICROBIOLOGY LETTERS, Issue 1 2004
    Takashi Noumura
    Abstract Thirteen dibenzofuran (DF)-utilizing bacteria carrying the DF terminal dioxygenase genes homologous to those of Terrabacter sp. strain DBF63 (dbfA1A2) were newly isolated from activated sludge samples. The amplified ribosomal DNA restriction analysis and the hybridization analyses showed that these strains were grouped into five genetically different types of bacteria. The sequence analyses of the 16S rRNA genes and the dbfA1A2 homologues from these five selected isolates revealed that the isolates belonged to the genus Rhodococcus, Terrabacter or Janibacter and that they shared 99,100% conserved dbfA1A2 homologues. We investigated the genetic organizations flanking the dbfA1A2 homologues and showed that the minimal conserved DNA region present in all five selected isolates consisted of an ,9.0-kb region and that their outer regions became abruptly non-homologous. Among them, Rhodococcus sp. strain DFA3 possessed not only the 9.0-kb region but also the 6.2-kb region containing dbfA1A2 homologues. Sequencing of their border regions suggested that some genetic rearrangement might have occurred with insertion sequence-like elements. Also, within their conserved regions, some insertions or deletions were observed. [source]


    Biodegradation and transport of benzene, toluene, and xylenes in a simulated aquifer: comparison of modelled and experimental results

    HYDROLOGICAL PROCESSES, Issue 16 2002
    Jiin-Shuh Jean
    Abstract Both laboratory experiments and numerical modelling were conducted to study the biodegradation and transport of benzene,toluene,xylenes (BTX) in a simulated semi-confined aquifer. The factors incorporated into the numerical model include advection, hydrodynamic dispersion, adsorption, and biodegradation. The various physico-chemical parameters required by the numerical model were measured experimentally. In the experimental portion of the study, BTX compounds were introduced into the aquifer sand. After the contaminants had been transported through the system, BTX concentrations were measured at 12 equally spaced wells. Subsequently, microorganisms obtained from the activated sludge of a sewage treatment plant and cultured in BTX mixtures were introduced into the aquifer through the 12 sampling wells. The distribution data for BTX adsorption by the aquifer sand form a nonlinear isotherm. The degree of adsorption by the sand varies, depending on the composition of the solute. The degradation time, measured from the time since the bacteria were added to the aquifer until a specific contaminant was no longer detectable, was 35,42 h for BTX. The dissolved oxygen, after degradation by BTX compounds and bacteria, was consumed by about 40,60% in the entire simulated aquifer; thus the aerobic conditions were maintained. This study provides insights for the biodegradation and transport of BTX in aquifers by numerical modelling and laboratory experiments. Experimental and numerical comparisons indicate that the results by Monod degradation kinetics are more accurate than those by the first-order degradation kinetics. Copyright © 2002 John Wiley & Sons, Ltd. [source]


    Isolation of a low-temperature adapted lipolytic enzyme from uncultivated micro-organism

    JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2008
    C. Roh
    Abstract Aims:, The aim of the study was to isolate a novel lipolytic enzyme from the activated sludge of uncultured micro-organisms. Methods and Results:, The metagenomic DNA was directly extracted from the activated sludge, and a metagenomic library was constructed by using the pUC vector. The library was screened for lipolytic enzyme activity on 1% tributyrin agar plate. A clone among c. 100 000 recombinant libraries showed the lipolytic activity. The putative lipolytic gene encoding lipo1 from the metagenomic library was subcloned and expressed in Escherichia coli BL21 using the pET expression system. The expressed recombinant enzyme was purified by Ni-nitrilotriacetic acid affinity chromatography and characterized using general substrates of lipolytic property. The gene consisted of 972 bp encoding a polypeptide of 324 amino acids with a molecular mass of 35·6 kDa. Typical residues essential for lipolytic activity such as penta-peptide (GXSXG) and catalytic triad sequences (Ser166, Asp221 and His258) were detected. The deduced amino acid sequence of lipo1 showed low identity with amino acid sequences of esterase/lipase (32%, ZP_01528487) from Pseudomonas mendocina ymp and esterase (31%, AAY45707) from uncultured bacterium. This lipolytic enzyme exhibited the highest activity at pH 7·5 and 10°C. At thermal stability analysis, lipo1 was more unstable at 40°C than 10°C. Conclusions:, An activity based strategy has been an effective method for fishing out a low-temperature adapted lipolytic enzyme from the metagenomic library. This lipo1 enzyme can be considered to belong to the hormone-sensitive lipase family due to the enzyme's oxyanion hole by the sequence HGGG. Significance and Impact of the Study:, Lipo1 is a novel psychrophilic esterase obtained directly from the metagenomic library. Owing its support of significant activity at low temperature, this enzyme is expected to be useful for potential application as a biocatalyst in organic chemistry. [source]


    A fluorescently-labelled r-RNA targeted oligonucleotide probe for the in situ detection of G-bacteria of the genus Amaricoccus in activated sludge

    JOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2000
    A.-M. Maszenan
    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. [source]


    Aerobic granules for low-strength wastewater treatment: formation, structure, and microbial community

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2009
    Shu-Guang Wang
    Abstract BACKGROUND: To validate the possibility of aerobic granulation at a lower organic loading rate (OLR) than 2 kg COD m,3 day,1 (GS 1) in a sequencing batch reactor (SBR), the formation, structure, and microbial community of granular sludge (GS) were investigated. RESULTS: The overall experimental process involved the following stages: acclimation, granulation, maturation, and stabilization. The optical microscopic showed the structural changes from fluffy activated sludge (AS) to GS and scanning electron microscope (SEM) examination revealed that GS 1 was irregular filamentous aggregates composed mainly of various filamentous species, while the aerobic granules cultivated at OLR 1.68,4.20 kg COD m,3 day,1 (GS 2) was mycelial pellets consisting of fungi and filamentous microorganisms. A Biolog Ecoplate analysis indicated that significant differences existed between the microbial community structure and the substrate's utilization of AS and different GS samples. CONCLUSION: GS 1 was achieved and different from GS 2 in the formation, structure, and microbial community. Aerobic granulation with low strength wastewater is of importance for the full-scale application of this technology. Copyright © 2009 Society of Chemical Industry [source]


    Study of saline wastewater influence on activated sludge flocs through automated image analysis

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2009
    Daniela P Mesquita
    Abstract BACKGROUND: In activated sludge systems, sludge settling ability is considered a critical step in effluent quality and determinant of solid,liquid separation processes. However, few studies have reported the influence of saline wastewater on activated sludge. This work aims the evaluation of settling ability properties of microbial aggregates in a sequencing batch reactor treating saline wastewaters of up to 60 g L,1 NaCl, by image analysis procedures. RESULTS: It was found that the sludge volume index (SVI) decreased with salt content up to 20 g L,1, remaining somewhat stable above this value. Furthermore, it was found that between the first salt concentration (5 g L,1) and 20 g L,1 aggregates suffered a strong deflocculation phenomenon, leading to a heavy loss of aggregated biomass. Regarding SVI prediction ability, a good correlation coefficient of 0.991 between observed and predicted SVI values was attained. CONCLUSION: From this work the deflocculation of aggregated biomass with salt addition due to pinpoint floc formation, dispersed bacteria growth and protozoa absence could be established. With respect to SVI estimation, and despite the good correlation obtained, caution is advisable given the low number of SVI data points. Copyright © 2008 Society of Chemical Industry [source]


    Long-term performance of co-metabolic degradation of trichloroethylene in a fluidized bed reactor fed with benzene, toluene and xylene

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2008
    Wei-Min Wu
    Abstract BACKGROUND: Trichloroethylene (TCE) can be degraded under aerobic condition with toluene and other aromatic compounds. Inhibition by primary substrates and toxicity of TCE oxidation influence TCE degradation. RESULTS: Long-term co-metabolic degradation of TCE was evaluated using a laboratory-scale fluidized bed reactor (12 L) with granular activated carbon (1.57 kg) as media and activated sludge as inoculum. The reactor was fed with TCE and a mixture of benzene, toluene and xylene (BTX) and operated with one-pass (hydraulic retention time (HRT) of 5,6 min) for 6 months and then with recirculation (HRT of 20,30 min) for 18 months. BTX/TCE-degrading biofilm was developed within 1 month. TCE was effectively degraded with influent TCE concentrations from 48 to 280 µg L,1. BTX inhibited TCE degradation. Recirculation (or long HRT) increased TCE removal efficiency from 30% with one-pass to 90%. BTX/TCE load ratio influenced TCE removal efficiency and TCE/BTX removal ratio. TCE degradation fitted first-order kinetics. The biomass grown in the reactor also degraded cis -1,2-dichloroethylene (DCE), trans -1,2-DCE and vinyl chloride efficiently except for 1,1-DCE. CONCLUSION: Co-metabolic degradation of TCE by BTX-degrading biomass from activated sludge is sustainable in the long term. BTX/TCE load ratio is a key parameter for TCE removal performance. Copyright © 2008 Society of Chemical Industry [source]


    Storage of biodegradable polymers by an enriched microbial community in a sequencing batch reactor operated at high organic load rate

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2005
    Davide Dionisi
    Abstract The production of polyhydroxyalkanoates (PHAs) from organic acids by mixed bacterial cultures using a process based on aerobic enrichment of activated sludge, that selects for mixed microbial cultures able to store PHAs at high rates and yields, is described. Enrichment resulted from the selective pressure established by periodic feeding the carbon source in a sequencing batch reactor (SBR); a mixture of acetic, lactic and propionic acids was fed at high frequency (2 hourly), high dilution rate (1 d,1), and at high organic load rate (12.75 g chemical oxygen demand (COD) L,1 d,1). The performance of the SBR was assessed by microbial biomass and PHA production as well as the composition and polymer content of the biomass. A final batch stage was used to increase the polymer concentration of the excess sludge produced in the SBR and in which the behaviour of the biomass was investigated by determining PHA production rates and yields. The microbial biomass selected in the SBR produced PHAs at high rate [278 mg PHAs (as COD) g biomass (as COD),1 h,1, with a yield of 0.39 mg PHAs (as COD) mg removed substrates (as COD),1], reaching a polymer content higher than 50% (on a COD basis). The stored polymer was the copolymer poly(3-hydroxybutyrate/3-hydroxyvalerate) [P(HB/HV)], with an HV fraction of 18% mol mol,1. The microbial community selected in the SBR was analysed by DGGE (denaturing gradient gel electrophoresis). The operating conditions of the SBR were shown to select for a restricted microbial population which appeared quite different in terms of composition with respect to the initial microbial cenosis in the activated sludge used as inoculum. On the basis of the sequencing of the major bands in the DGGE profiles, four main genera were identified: a Methylobacteriaceae bacterium, Flavobacterium sp, Candidatus Meganema perideroedes, and Thauera sp. The effects of nitrogen depletion (ie absence of growth) and pH variation were also investigated in the batch stage and compared with the SBR operative mode. Absence of growth did not stimulate higher PHA production, so indicating that the periodic feed regime fully exploited the storage potential of the enriched culture. Polymer production rates remained high between pH 6.5 and 9.5, whereas the HV content in the stored polymer strongly increased as the pH value increased. This study shows that polymer composition in the final batch stage can readily be controlled independently from the feed composition in the SBR. Copyright © 2005 Society of Chemical Industry [source]


    Characterization and modelling of denim-processing wastewaters for activated sludge

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2001
    Derin Orhon
    Abstract The study involved characterization of denim-processing wastewaters, mainly to generate the necessary experimental data for the modelling and evaluation of the activated sludge process. The striking feature of the wastewater quality was the excessive suspended solids content requiring effective removal before biological treatment. COD fractionation was, however, typical for a textile effluent in general, with a biodegradable fraction of 90%, a readily biodegradable COD ratio of 20%, a predominantly soluble slowly biodegradable fraction of 55,60% and negligible particulate inert COD. Hydrolysis was identified as the significant step in the biodegradation kinetics with rate coefficients quite specific to plant operation. Evaluation of the hydrolysis kinetics showed that the magnitude of the slowly biodegradable COD could be reduced with a higher hydraulic detention time, effectively improving the quality of the soluble effluent. © 2001 Society of Chemical Industry [source]


    Ozonation of activated sludge in the recycle stream

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2001
    A Huysmans
    Abstract Intermittent ozonation of a part of the recycle sludge was performed two times a week for a laboratory-scale reactor at an average ozone dose of 0.019,g O3(gSSozonated),1. Under these conditions a decrease of about 50% in sludge growth was obtained for the ozone-treated system, in comparison with the control. As a consequence less sludge had to be removed from the test reactor. Only a slight decrease in quality of effluent was noticed. A comparative cost calculation was made, based on these results, between an ozone-treated activated sludge system and a traditional activated sludge system. © 2001 Society of Chemical Industry [source]


    A thermodynamic analysis of the activated sludge process: Application to soybean wastewater treatment in a sequencing batch reactor

    AICHE JOURNAL, Issue 10 2009
    Bing-jie Ni
    Abstract A bioenergetic methodology was integrated with a modified activated sludge model No.1 (ASM1) to analyze the activated sludge process, with the treatment of soybean-processing wastewater as an example. With the bioenergetic methodology established by McCarty and coworkers, the microbial yield was predicted and the overall stoichiometrics for biological reactions involving the key chemical and biological species in activated sludge were established. These obtained parameters were related to the ASM1 model, which was modified after coupling the biological reactions in activated sludge with electron balances. This approach was able to approximately describe the treatment of soybean wastewater by activated sludge in a sequencing batch reactor in terms of substrate utilization, biomass growth, and the elector acceptor consumption. Such an attempt provides useful information for accurate modeling of the complex activated sludge process. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]


    Biodegradable polymers based on renewable resources.

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2005

    Abstract Novel polycarbonates, with pendant functional groups, based on 1,4:3,6-dianhydrohexitols and L -tartaric acid derivatives were synthesized. Solution polycondensations of 1,4:3,6-dianhydro-bis- O -(p -nitrophenoxycarbonyl)hexitols and 2,3-di- O -methyl- L -threitol or 2,3- O -isopropylidene- L -threitol afforded polycarbonates having pendant methoxy or isopropylidene groups, respectively, with number average molecular weight (Mn) values up to 3.61 × 104. Subsequent acid-catalyzed deprotection of isopropylidene groups gave well-defined polycarbonates having pendant hydroxyl groups regularly distributed along the polymer chain. Differential scanning calorimetry (DSC) demonstrated that all the polycarbonates were amorphous with glass transition temperatures ranging from 57 to 98 °C. Degradability of the polycarbonates was assessed by hydrolysis test in phosphate buffer solution at 37 °C and by biochemical oxygen demand (BOD) measurements in an activated sludge at 25 °C. In both tests, the polycarbonates with pendant hydroxyl groups were degraded much faster than the polycarbonates with pendant methoxy and isopropylidene groups. It is noteworthy that degradation of the polycarbonates with pendant hydroxyl groups was remarkably fast. They were completely degraded within only 150 min in a phosphate buffer solution and their BOD-biodegradability reached nearly 70% in an activated sludge after 28 days. The degradation behavior of the polycarbonates is discussed in terms of their chemical and physical properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3909,3919, 2005 [source]


    Changes in the rRNA levels of specific microbial groups in activated sludge during sample handling and storage

    LETTERS IN APPLIED MICROBIOLOGY, Issue 2 2005
    J.E. Keith
    Abstract Aims:, To quantitatively analyse the changes in group-specific rRNA levels in activated sludge as a function of sample handling and storage procedure. Methods and Results:, Quantitative membrane hybridizations with 32P-labelled oligonucleotide probes were used to analyse the effects of different sample handling and storage conditions on the relative rRNA levels of the alpha, beta, and gamma-Proteobacteria, the Cytophaga-Flavobacteria group, and the mycolic acid-containing actinomycetes in activated sludge. Group-specific rRNA levels, expressed as percentages of total 16S rRNA detected with a universal probe, in samples maintained at room temperature significantly changed after 48 h. Group-specific rRNA levels in samples treated with chloramphenicol showed significant change after 72 h. Conclusions:, Sample storage at room temperature is a viable option if freezing or analysis can be performed within 24 h, while treatment with chlorampenicol can extend that time to at least 48 h. Significance and Impact of the Study:, Handling, shipping, and storage of environmental samples under several conditions may result in inaccurate determination of the microbial populations in microbial ecology studies. [source]


    A quantitative method for measuring the mass concentration of the filamentous bacterium Type 021N in activated sludge using fluorescence in situ hybridization

    LETTERS IN APPLIED MICROBIOLOGY, Issue 2 2003
    Y. Guan
    Abstract Aims: This study aimed to develop a quantitative method for measuring mass concentrations of Type 021N, a bacterium causing bulking in activated sludge. Methods and Results: Fluorescence in situ hybridization was used to determine the relationship between the concentration ratio of the mass of the bacterium Type 021N to mass of activated sludge, and the proportion of fluorescence area imparted by probe G123T specific for Type 021N to that obtained with probe EUB338 for bacteria. A linear relationship existed between the cube root of the mass concentration ratio and square root of this area proportion. Conclusions: A standard curve was obtained for quantifying Type 021N in activated sludge. Significance and Impact of the Study: This method may allow the determination of growth rate constant of filamentous bacteria in activated sludge, information that will help in understanding their ecology. [source]


    Lipase-Catalyzed Synthesis and Properties of Poly[(12-hydroxydodecanoate)- co -(12-hydroxystearate)] Directed towards Novel Green and Sustainable Elastomers

    MACROMOLECULAR BIOSCIENCE, Issue 1 2008
    Hiroki Ebata
    Abstract Novel green and sustainable elastomers having both good biodegradability and chemical recyclability properties were designed and synthesized using potentially biobased materials and lipase as an environmentally benign catalyst. High molecular weight poly[(12-hydroxydodecanoate)- co -(12-hydroxystearate)] [poly(12HD- co -12HS)] samples with varying monomer ratios were prepared by the polycondensation of 12-hydroxydodecanoic acid and methyl 12-hydroxystearate using immobilized lipase from Candida antarctica (IM-CA) in toluene in the presence of molecular sieves 4A at 90,°C. Although poly(12HD) is a highly crystalline polyester having a melting temperature (Tm) of 87.6,°C and crystalline temperature (Tc) of 64,°C, by the copolymerization of 12HD with 12HS, both the Tm and Tc of the copolymer decreased with increasing 12HS contents, and poly(12HD- co -12HS) containing more than 60 mol-% 12HS was a viscous liquid at room temperature. At the same time, the Young's modulus and hardness also decreased with increasing 12HS content, and poly(12HD- co -36 mol-% 12HS) exhibited an elastic behavior, having a hardness of 70 A using a durometer A. In addition, it showed an excellent biodegradability by activated sludge and chemical recyclability by lipase. [source]


    Surface Modification of Poly(propylene) Microporous Membrane to Improve Its Antifouling Characteristics in an SMBR: O2 Plasma Treatment

    PLASMA PROCESSES AND POLYMERS, Issue 1 2008
    Hai-Yin Yu
    Abstract Fouling is the major obstacle in membrane processes applied in water and wastewater treatment. To improve the antifouling characteristics of PPHFMMs in an SMBR for wastewater treatment, the PPHFMMs were surface-modified by O2 low temperature plasma treatment. Structural and morphological changes on the membrane surface were characterized by XPS and FE-SEM. The change of surface wettability was monitored by contact angle measurements. Results of XPS clearly indicated that the plasma treatment introduced oxygen containing polar groups on the membrane surface. The static water contact angle of the modified membrane reduced obviously with the increase of plasma treatment time. The relative pure water flux for the modified membranes increased with plasma treatment time up to 1 min, then it decreased with further increase of plasma treatment time. Decreases in the tensile strength and the tensile elongation at break of the modified membranes were also observed. To assess the relation between the plasma treatment and the membrane fouling in an SMBR, filtration for activated sludge was carried out by using synthetic wastewater. After continuous operation in the SMBR for about 75 h, flux recovery were 8.7 and 12.3%, reduction of flux were 91.6 and 87.4% for the nascent and O2 plasma treated PPHFMM for 1 min, relative flux ratio for O2 plasma treated PPHFMM for 1 min was 49.9% higher than that of the nascent PPHFMM. [source]


    Preparation and characterization of biodegradable waterabsorbent PAN/SS nanocomposite

    POLYMER COMPOSITES, Issue 11 2008
    Bijayashree Samal
    Polyacrylonitrile (PAN)/sodium silicate (SS) nanocomposite was prepared via nonconventional emulsion method using an in situ developed transition metal complex Cu(II)/glycine taking ammonium persulfate (APS) as initiator, with a novel motive of converting hydrophobic homopolymer PAN into hydrophilic nano material via nanotechnology by the inclusion of SS to the homopolymer. UV,visible spectral analysis was carried out which revealed various interactions between the in situ developed complex with other reaction components. The formation of the PAN/SS nanocomposite was confirmed by infrared spectra (IR). Furthermore, as evidenced by transmission electron microscopy (TEM), the composite so obtained was found to have nano scale structure. X-ray diffraction (XRD) was carried out suggesting that the silicate layers were exfoliated during the polymerization process. An increase in the thermal stability for the developed nanocomposite was recorded by thermogravimetric analysis (TGA). Surprisingly, it was also found that the PAN/SS nanocomposite showed considerable amount of waterabsorbency and was biodegradable as tested by activated sludge and cultured media and further confirmed by scanning electron microscopy (SEM). POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source]


    Stimulation of aerobic degradation of chlorinated ethenes in soil by microbial inoculation

    REMEDIATION, Issue 2 2008
    Talaat Balba
    Degradation of chlorinated ethenes under aerobic conditions has been reported using a cometabolic pathway. A site in Illinois had shallow contamination and sandy soils, which in combination created aerobic conditions. The aerobic conditions prevented the degradation of chlorinated ethenes by reductive dechlorination. Biodegradation of chloroethenes under aerobic conditions does not occur naturally at all sites; however, it can be enhanced if microorganisms capable of cometabolic degradation are introduced into the soil. In this study, trichloroethene (TCE) removal in the soil was enhanced by the injection of a commercially available microbial inoculum (CL-OUT® inoculum, CL-Solutions, Cincinnati, OH) and nutrients and was compared to chlorinated ethene removal in soil that had received nutrients only and soil that had received activated sludge and nutrients. Trichloroethene removal was measured after one week, seven weeks, and eleven weeks. After one week, no significant TCE removal had occurred in any of the test microcosms. After seven weeks, a slight decrease in TCE levels accompanied by an increase in cis -1,2-dichloroethene (cis -1,2-DCE) was seen in the microcosms that had received CL-OUT®. After 11 weeks, a marked decrease in TCE levels was observed in the microcosms that had received CL-OUT®. No significant TCE decrease was observed in any of the other microcosms. These data suggest that organisms capable of aerobic TCE degradation were not present at the site; however, the addition of an inoculum containing such organisms enabled aerobic degradation to occur. © 2008 Wiley Periodicals, Inc. [source]


    Optimization of metagenomic DNA extraction from activated sludge samples

    ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
    Yuan-Yuan Qu
    Abstract Metagenomic DNA extraction is essential for metagenomic technology. Therefore, optimization of a conventional total DNA extraction from activated sludge was investigated in detail in this study. Throughout two distinct orthogonal experiments, it was shown that the highest yield for metagenomic DNA could be obtained using TENP buffer, lysozyme of 1 mg ml,1 (1 h), protease K (200 µg ml,1), SDS (1%, 1 h). Furthermore, the quality of the differentially extracted DNA was subsequently assessed by the molecular fingerprint technology, such as denaturing gradient gel electrophoresis (DGGE) and ribosomal intergenic spacer analysis (RISA). The results indicated that the microbial diversity was dramatically different by different combined methods, and the DNA template quality for RISA was much better than that for polymerase chain reaction (PCR)-DGGE. This study provides detail process for metagenomic DNA extraction of activated sludge, and it would be useful for metagenomic DNA extraction of other environment samples. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]