Effect of seasonal succession of algal communities on fouling of MF membrane.

An emerging threat to membrane application is the seasonal proliferation of algae in water sources such as rivers, reservoirs and lakes. This study investigated the link between feed parameters and the membrane performance of a pilot-scale microfiltration (MF) plant for 7 months. The seasonal succession of algae in relation to temperature dynamics was monitored. Temperature-dependent seasonal patterns for algae species were observed. The water temperatures during the dominance of cyanobacteria, especially Microcystis, were relatively higher (over 25 °C) than those during the dominance of diatoms. Diatoms did not much affect membrane performance (less than 0.2 kgf/cm2), however, under the cyanobacterial dominance condition, especially Microcystis sp., transmembrane pressure (TMP) reached up to the limited level (0.4 kgf/cm2) within one month. Concurrently UV absorbance at 254 nm wavelength and dissolved organic carbon values increased significantly during the Microcystis bloom and the build-up rate of TMP increased up to 0.005 kgf/cm2/day. Membrane autopsy also showed that during the dominance of diatom, application of cleaning agents can fully remove foulants on the membrane surface. However, during the dominance of cyanobacteria, there is a lot of Al, Si and organic complex on the fouled membrane, indicating the formation of Al-organic complexes that contributed to the residual membrane fouling. It is suggested that the irrecoverable fouling layer still contained some Al, mostly in complex with organics. Thus, organic matter originated from cyanobacteria may cause a serious impact on membrane fouling by forming the complex with metal ions originated from coagulant.

Effects of Quorum Quenching on Biofilm Metacommunity in a Membrane Bioreactor.

Quorum quenching (QQ) has received attention for the control of biofilms, e.g., biofilms that cause biofouling in membrane bioreactors (MBRs). Despite the efficacy of QQ on biofouling, it is elusive how QQ influences biofilm formation on membranes. A pilot-scale QQ-MBR and non-QQ-MBR were identically operated for 4 days and 8 days to destructively sample the membranes. QQ prolonged the membrane filterability by 43% with no harmful influence on MBR performance. qPCR showed no effect of QQ on microbial density during either of these time periods. Community comparisons revealed that QQ influenced the bacterial and fungal community structures, and the fungal structure corresponded with the bacterial structure. Metacommunity and spatial analyses showed that QQ induced structural variation rather than compositional variation of bacteria and fungi. Moreover, QQ considerably enhanced the bacterial dispersal across membrane during the early development. As the dispersal enhancement by QQ counteracted the ecological drift, it eliminated the distance-decay relationship, reflecting a neutral theory archetype of metacommunity. Network analyses showed that QQ substantially reduced the amount and magnitude of interactions, e.g., competition and cooperation, for bacteria and fungi, and weakened their network structures, irrespective of time. Additionally, QQ suppressed the growth of specific microbial species (e.g., Acinetobacter), abundant and widespread at the early stage. These findings suggest that QQ influenced the community dynamics at the regional and local levels, correspondingly the ecological selection and dispersal processes, during the biofilm development.

Spatiotemporal dynamics and correlation networks of bacterial and fungal communities in a membrane bioreactor.

To systematically study biofilm communities responsible for biofouling in membrane bioreactors (MBRs), we characterized the spatiotemporal dynamics of bacterial and fungal biofilm communities, and their networks, in a pilot-scale flat-sheet MBR treating actual municipal wastewater. Activated sludge (AS) and membrane samples were collected on days 4 and 8. The membranes were cut into 18 tiles, and bacterial and fungal communities were analyzed using next generation sequencing. Nonmetric multidimensional scaling (NMDS) plots revealed significant temporal variations in bacterial and fungal biofilm communities due to changes in the abundances of a few dominant members. Although the experimental conditions and inoculum species pools remained constant, variogram plots of bacterial and fungal communities revealed decay in local community similarity with geographic distance at each sampling time. Variogram modeling (exponential rise to maximum, R2 ≥ 0.79) revealed that decay patterns of both communities were different between days 4 and 8. In addition, networks of bacteria or fungi alone were distinct in network composition between days 4 and 8. The day-8 networks were more compact and clustered than those of the earlier time point. Bacteria-fungi networks show that the number of inter-domain associations decreased from 113 to 40 with time, confirming that membrane biofilm is a complex consortium of bacteria and fungi. Spatiotemporal succession in biofilm communities may be common on MBR membranes, resulting from different geographic distributions of initial microbial populations and their priority effects.

Effects of Quorum Quenching on the Microbial Community of Biofilm in an Anoxic/Oxic MBR for Wastewater Treatment.

Recently, bacterial quorum quenching (QQ) has been proven to have potential as an innovative approach for biofouling control in membrane bioreactors (MBRs) for advanced wastewater treatment. Although information regarding the microbial community is crucial for the development of QQ strategies, little information exists on the microbial ecology in QQ-MBRs. In this study, the microbial communities of biofilm were investigated in relation to the effect of QQ on anoxic/oxic MBRs. Two laboratory-scale MBRs were operated with and without QQ-beads (QQ-bacteria entrapped in beads). The transmembrane pressure increase in the QQ-MBRs was delayed by approximately 100-110% compared with conventional- and vacant-MBRs (beads without QQ-bacteria) at 45 kPa. In terms of the microbial community, QQ gradually favored the development of a diverse and even community. QQ had an effect on both the bacterial composition and change rate of the bacterial composition. Proteobacteria and Bacteroidetes were the most dominant phyla in the biofilm, and the average relative composition of Proteobacteria was low in the QQ-MBR. Thiothrix sp. was the dominant bacterium in the biofilm. The relative composition of Thiothrix sp. was low in the QQ-MBR. These findings provide useful information that can inform the development of a new QQ strategy.

Crossing the Border between Laboratory and Field: Bacterial Quorum Quenching for Anti-Biofouling Strategy in an MBR.

Quorum quenching (QQ) has recently been acknowledged to be a sustainable antifouling strategy and has been investigated widely using lab-scale membrane bioreactor (MBR) systems. This study attempted to bring this QQ-MBR closer to potential practical application. Two types of pilot-scale QQ-MBRs with QQ bacteria entrapping beads (QQ-beads) were installed and run at a wastewater treatment plant, feeding real municipal wastewater to test the systems' effectiveness for membrane fouling control and thus the amount of energy savings, even under harsh environmental conditions. The rate of transmembrane pressure (TMP) build-up was significantly mitigated in QQ-MBR compared to that in a conventional-MBR. Consequently, QQ-MBR can substantially reduce energy consumption by reducing coarse bubble aeration without compromising the effluent water quality. The addition of QQ-beads to a conventional MBR substantially affected the EPS concentrations, as well as microbial floc size in the mixed liquor. Furthermore, the QQ activity and mechanical stability of QQ-beads were well maintained for at least four months, indicating QQ-MBR has good potential for practical applications.

Fate and behavior of extended-spectrum ß-lactamase-producing genes in municipal sewage treatment plants.

Extended-spectrum ß-lactamases (ESBLs) have the capability of hydrolyzing a variety of the newer ß-lactam antibiotics, including the third-generation cephalosporins and monobactams known as a rapidly evolving group of ESBLs. The purpose of this study was to investigate the occurrence and fate of ß-lactamase producing genes (CTX-M type 1, type2, CTX-M probe for all groups except CTX-M-1, and TEM, SHV, OXA) through wastewater treatment utilities. ß-lactamase producing genes in influent, digested sludge, activated sludge, and disinfected effluent were monitored. The results showed that influent contained high level of all target genes, and all CTX-M types, SHV, and OXA gene decreased significantly in biological treatment process such as activated sludge process and anaerobic digestion, however, TEM type was not effectively eliminated. Possibly, host microbes of TEM could be most resistant in target genes or to some extent gene transfer occurred in wastewater treatment processes. All target genes were significantly reduced during disinfection. Consequently, wastewater treatment process apparently reduced host microbes carrying ß-lactamase producing genes effectively, although they are selectively removed in biological processes. In addition, the significant reduction during disinfection was shown, although slightly differences of removal efficiency were observed in resistance.

Long-term survival of methanogens of an anaerobic digestion sludge under starvation and temperature variation.

To investigate starvation effect on methanogen community, two identical membrane reactors were continuously operated for 84 consecutive days, with a temperature change from 50 degrees C to 20 degrees C. Continuous feeding washed out 97% biomass from reactors during the experimental period. Quantitative PCR, using mcrA genes, indicated that the methanogen abundance decreased from 7.0 x 10(7) to 1.2 x 10(7) mcrA copies ml(-1) (volume basis) at 50 degrees C, and then increased to 4.4 x 10(7) mcrA copies ml(7) at 20 degrees C (p<0.05). Correspondence analysis indicated that methanogen communities were distinctly grouped by each temperature. Canonical correspondence analysis indicated that temperature showed a significant correlation with the methanogen community composition. These results suggest that methanogens can survive for a long time (at least more than 84 days) under starvation conditions, and that temperature could be a primary factor determining the density and community of methanogens.

Effects of granular activated carbon on methane removal performance and methanotrophic community of a lab-scale bioreactor.

Two identical lab-scale bioreactor systems were operated to examine the effects of granular activated carbon (GAC) on methane removal performance and methanotrophic community. Both bioreactor systems removed methane completely at a CH4 loading rate of 71.2 g-CH4·d(-1) for 17 days. However, the methane removal efficiency declined to 88% in the bioreactor without GAC, while the bioreactor amended with GAC showed greater methane removal efficiency of 97% at a CH4 loading rate of 107.5 g-CH4·d(-1). Although quantitative real-time PCR showed that methanotrophic populations were similar levels of 5-10 × 10(8) pmoA gene copy number·VSS(-1) in both systems, GAC addition changed the methanotrophic community composition of the bioreactor systems. Microarray assay revealed that GAC enhanced the type I methanotrophic genera including Methylobacter, Methylomicrobium, and Methylomonas of the system, which suggests that GAC probably provided a favorable environment for type I methanotrophs. These results indicated that GAC is a promising support material in bioreactor systems for CH4 mitigation.

Biodegradation capacity utilization as a new index for evaluating biodegradation rate of methane.

Density of catalytic organisms can determine the biodegradation capacity and specific biodegradation rate (SBR). A new index, biodegradation capacity utilization (BCU, %), was developed for estimating the extent of actual biodegradation of a gas compound over the full capacity. Three methanotrophic cultures were serially diluted (1-1/25), and methane SBR and BCU were measured. Consistently, biomass reduction increased the SBR and decreased the BCU. Linearity (p < 0.05, r > 0.97) between the BCU and cell density indicated the reflection of biodegradation capacity by BCU. Therefore, BCU is indicative of whether the density of catalytic organisms is pertinent for SBR evaluation of low-soluble gaseous compounds.

Use of artificial DNA with multiple probe sites as reference DNA templates for quantitative real-time PCR to examine methanogen communities.

Isolation of reference DNA templates for quantitative real-time PCR assays is an expensive, labor-intensive and time-consuming process if they are not readily available. Two artificial DNA templates with multiple probe sites were designed for quantifying methanogens and their 10 subgroups, based on the methyl coenzyme M reductase gene (mcrA). Their standards were comparable to each other. PCR amplification efficiencies (cycle vs. cumulative fluorescence) of the artificial DNAs were also comparable to those of the observed methanogen groups from anaerobic digesters. The artificial templates can be alternatives to the actual references.

Net methane oxidation performance of anaerobic sewage sludge.

The anaerobic oxidation of methane (AOM) in anaerobic sewage sludge was characterized. The net methane oxidation was observed in samples amended with methane plus sulfate or with methane alone, whereas methane formation was observed in the samples without methane, indicating that methane oxidation and formation occurred simultaneously. The ratio of the net methane oxidation rate to H2S formation was 100:1, suggesting that the AOM was not closely associated with sulfate reduction in the anaerobic sludge. The net AOM was positively associated with the methane concentration and sludge dilution ratio. However, the rate of AOM was negatively correlated with organic substrate (acetate) concentration. Therefore, the production and oxidation of methane could be controlled by environmental conditions and dissolved organic compounds in the bulk solution.

Electron density-based transformation of trimethoprim during biological wastewater treatment.

This research investigated the biological transformation of trimethoprim (TMP). Partial TMP removal was observed in the presence of ammonia and toluene, and increasing the solids retention time from 20 days to 60 days improved TMP removal in both the nitrifying and heterotrophic bioreactors. Two TMP-related metabolites were identified, the first (5-(3,4,5-trimethoxybenzyl) pyrimidine-2,4-diamine, 5-hydroxyl) showing that a hydroxylation reaction took place, and the second (5-(1-carboxyl, 1-methoxy, 5-methoxy 1-,4-pentene) pyrimidine-2,4-diamine, 5-hydroxyl) showing that the trimethoxybenzyl ring was cleaved. This research is the first that we are aware of to report these two TMP-related byproducts. TMP metabolites show that initiating reactions take place where the electron density is highest, and that these initiating reactions shift the electron density of TMP, likely affecting the course of transformation.

Structure and dynamics of microbial community in full-scale activated sludge reactors.

Phospholipid fatty acid (PLFA) profiles in four full-scale activated sludge reactors (ASR1 ~ 4) treating municipal wastewater, South Korea, were monitored to evaluate the influence of influent water quality on microbial community structure (MCS) and the effect of the MCS on effluent water quality. In ASR1 ~ 3, PLFA profiles were very similar, regardless of the influent water quality and seasonal differences, and 16:17c/15:0iso2OH and 16:0 were dominant. PLFA profiles in ASR4 during summer and autumn were very similar to those in ASR1 ~ 3, but increases in specific fatty acids, 16:1ω5c, 11methyl18:1ω7c and 15:0iso3OH, were found in ASR4 during winter and spring, with relatively high total suspended solid (TSS) concentrations in the effluent. 16:1ω5c and 15:0iso3OH, possibly related with Flexibacter sp., caused a bulking problem in the activated sludge. The community diversity indices such as Shannon diversity and equability decreased in summer but increased in autumn in all the ASRs. Canonical correspondence analysis results suggested that the influent BOD concentration played the most important role in changing MCS, followed by influent TSS concentration. In addition, the TSS and total phosphorus concentrations in the effluent were significantly affected by the change of the MCS.

Characterization of a methane-oxidizing biofilm using microarray, and confocal microscopy with image and geostatic analyses.

A mixed methane-oxidizing biofilm was characterized, concurrently using a number of advanced techniques. Community analysis results by microarray exhibited that type II members dominated the methanotrophic community, in which Methylocystis was most abundant, followed by Methylosinus. Observation results by fluorescent in situ hybridization and confocal microscopy showed multiple biofilm colonies that were irregular, bell-shaped, with mean thickness of approximately 20 µm. Image analysis results indicated that the relative abundance of methanotrophs peaked at a depth of about 5 µm. Although the biofilm colonies differed in size, methanotrophs accounted for 4-9%. Gaussian and linear regression results between the biofilm volumes and types I (r (2) = 0.86) and II volumes (r (2) = 0.92), respectively, revealed that type I members played a role in the growth of the biofilm but only below a threshold volume, whereas type II members supported the overall growth. Geostatistical analyses results revealed concentration of types I and II methanotrophic individuals with decreasing depth, and randomness between the spatial locations and population levels. Collectively, the methane-oxidizing biofilm was a highly organized system with methanotrophs and their cohabitants.

Using electronic theory to identify metabolites present in 17α-ethinylestradiol biotransformation pathways.

This research used electronic theory to model the biotransformation of 17α-ethinylestradiol (EE(2)) under aerobic conditions in mixed culture. The methodology involved determining the Frontier Electron Density (FED) for EE(2) and various metabolites, as well as invoking well-established degradation rules to predict transformation pathways. We show that measured EE(2) metabolites are in good agreement with what is expected based on FED-based modeling. Initiating reactions occur at Ring A, producing metabolites that have been experimentally detected. When OH-EE(2) and 6AH-EE(2) are transformed, Ring A is cleaved before Ring B. The metabolites involved in these pathways have different estrogenic potentials, as implied by our analysis of the log P values and the hydrogen bonding characteristics. The OH-EE(2) and 6AH-EE(2) transformation pathways also show redox-induced electron rearrangement (RIER), where oxidation reactions lead to the reduction of carbon units present along the bond axis. Sulfo-EE(2) appears to be difficult to biotransform. These findings clarify theoretical and practical aspects of EE(2) biotransformation.

Biodegradation of petroleum hydrocarbons by Neosartorya sp. BL4.

A new petroleum hydrocarbon-degrading fungus, isolated from an oil contaminant soil, was identified as Neosartorya (teleomorph of Aspergillus) sp. This isolate was able to degrade total petroleum hydrocarbons (TPHs) without a lag phase, but degradation rates decreased with increasing initial TPH concentrations (5,000-20,000 mg L(-1)). The TPH degradation by the isolate showed a substrate inhibition behavior with an inhibition constant (K(i)) of 1,860 mg L(-1). Dual lag phase of TPH degradation indicated the ability to adapt its metabolic activity to utilize different types of hydrocarbons as an electron donor. Initially n-alkanes were rapidly removed without lag phase in the whole range of substrate and heavy molecular weight alkanes (HMWAs; C23-C24) and low molecular weight alkanes (LMWAs C9-C15) out of n-alkane hydrocarbons were degraded rapidly, whereas the removal of mid molecular weight alkanes (MMWAs; C16-C22) was relatively slower. Relatively slow degradation of MMWAs is probably caused by biotransformation of HMWAs or non-alkane hydrocarbons to MMWAs.

Characterization of methane oxidation by a methanotroph isolated from a landfill cover soil, South Korea.

A methane-oxidizing bacterium was isolated from the enriched culture of a landfill cover soil. The closest relative of the isolate, designated M6, is Methylocystis sp. Based on a kinetic analysis, the maximum specific methane oxidation rate and saturation constant were 4.93 mmol·g--dry cell weight--1·h⁻¹ and 23 microM, respectively. This was the first time a kinetic analysis was performed using pure methanotrophic culture. The methane oxidation by M6 was investigated in the presence of aromatic (m- and p-xylene and ethylbenzene) or sulfur (hydrogen sulfide, dimethyl sulfide, methanthiol) compounds. The methane oxidation was inhibited by the presence of aromatic or sulfur compounds.

Novel biodegradation pathways of cyclohexane by Rhodococcus sp. EC1.

The metabolism of cyclohexanes by Rodococcus sp. EC1 was investigated using a sequential tracking method of degradation intermediate. Evidence for the formation of cyclohexanol, cyclohexaone, 2-cyclohexen-1-one, and phenol was presented. EC1 metabolized cyclohexane to phenol by aromatization of 2-cyclohexen-1-one, and furthermore gamma-butyrolactone as an intermediate of 2-cyclohexen-1-one was formed. Aromatization by EC1 was confirmed using tetrahydrofuran. Tetrahydrofuran was metabolized through aromatization reaction, involving furan and 2,3-dihydrofuran as key intermediates. EC1 can degrade cyclohexane and tetrahydrofuran in aromatization via desaturation.

Exploring 17α-ethinylestradiol removal, mineralization, and bioincorporation in engineered bioreactors.

This research investigated removal, mineralization, and bioincorporation of 17α-ethinylestradiol (EE(2)) in membrane bioreactors and conventional bioreactors. When the influent EE(2) concentration was >50 µg/L, the membrane bioreactor (MBR) biomass removed more EE(2) than conventional bioreactor (CBR) biomass in continuous tests, likely because the sorption partitioning coefficients are higher for MBR biomass. Microautoradiography was carried out to investigate the distribution of EE(2) within the aggregates retrieved from the bioreactors, and the results revealed concentration gradients present within the floc. Experiments using radiolabeled (14)C-EE(2) experiments (done with 24.5 µg/L EE(2)) showed that EE(2) removal rates and the amount of EE(2) mineralized were similar in MBRs and CBRs. Direct measurements and bioenergetic estimates suggest that EE(2)-related carbon is probably incorporated into active biomass, despite the fact that EE(2) was added at a concentration that was much lower than that of the primary growth substrates.

The effect of nitrate and sulfate on mediator-less microbial fuel cells with high internal resistance.

Microbial fuel cells (MFCs) simultaneously provide waste treatment while capturing energy in the form of electricity. Although these devices are being used in engineered and natural environments where nitrate or sulfate may inhibit power production, the effects of these electron acceptors have not been fully explored. This research investigated the effect of nitrate and sulfate on MFC power production when these chemicals are present at the anode. Nitrate decreased the maximum current and power density by 15 and 17%, respectively, when present at 20 mg/L, and sulfate caused the maximum current and power density to decrease by 4 and 7%, respectively (also at 20 mg/L). Stronger inhibition was observed at higher nitrate and sulfate concentrations, but power production persisted. Coulombic efficiency decreased as nitrate and sulfate levels increased, although this was not primarily due to the biochemical reduction of nitrate or sulfate; rather, it was probably because of the inhibition of exoelectrogens.