Fate of Escherichia coli O157:H7 during composting of bovine manure in a laboratory-scale bioreactor

Inactivation profiles of Escherichia coli O157:H7 in inoculated bovine manure-based compost ingredients were determined by composting these ingredients in a bioreactor under controlled conditions. A 15-liter bioreactor was constructed to determine the fate of E. coli O157:H7 and changes in pH, moisture content, temperature, and aerobic mesophilic and thermophilic bacterial counts during composting. Fresh cow manure, wheat straw, cottonseed meal, and ammonium sulfate were combined to obtain a moisture content of ca. 60% and a carbon/nitrogen ratio of 29:1. The compost ingredients were held in the bioreactor at a constant external temperature of 21 or 50 degrees C. Self-heating of the ingredients due to microbial activity occurred during composting, with stratified temperatures occurring within the bioreactor. At an external temperature of 21 degrees C, self-heating occurred for 0 to 3 days, depending on the location within the bioreactor. E. coli O157:H7 populations increased by 1 to 2 log10 CFU/g during the initial 24 h of composting and decreased by ca. 3.5 log10 CFU/g near the bottom of the bioreactor and by ca. 2 log10 CFU/g near the middle and at the top during 36 days of composting. At an external temperature of 50 degrees C. E. coli O157:H7 was inactivated rapidly (by ca. 4.9 log10 CFU/g at the top of the bioreactor, by 4.0 log10 CFU/g near the middle, and by 5.9 log10 CFU/g near the bottom) within 24 h of composting. When inoculated at an initial level of ca. 10(7) CFU/g. E. coli O157:H7 survived for 7 days but not for 14 days at all three sampling locations, as indicated by either direct plating or enrichment culture. At the top of the bioreactor a relatively constant moisture content of 60% was maintained, whereas the moisture content near the bottom decreased steadily to 37 to 45% over 14 days of composting. The pH of the composting mixture decreased to ca. 6 within 1 to 3 days and subsequently increased to 8 to 9. Results obtained in this study indicate that large populations (10(4) to 10(7) CFU/g) of E coli O157:H7 survived for 36 days during composting in a bioreactor at an external temperature of 21 degrees C but were inactivated to undetectable levels after 7 to 14 days when the external temperature of the bioreactor was 50 degrees C. Hence, manure contaminated with large populations (e.g., 10(7) CFU/g) of E. coli O157:H7 should be composted for more than 1 week, and preferably for 2 weeks, when held at a minimum temperature of 50 degrees C.     

Fate of endocrine disrupting compounds in membrane bioreactor systems

Yeast estrogen screen (YES) bioassay and liquid chromatography-mass spectrum-mass spectrum (LC-MS-MS) analysis were performed to investigate the fate of active and potential endocrine disrupting compounds in 3 pilot-scale and 2 lab-scale membrane bioreactor (MBR) systems. Compared with the overall estrogenicities of sewage treatment plant (STP) effluents from references, the MBR systems studied have relatively good performance in the removal of estrogenicity. Estrone (E1) was removed with relatively high efficiency (80.2-91.4%), but 17beta-estradiol (E2) was removed with moderate efficiency (49.3-66.5%) by the MBRs. However, the experimental results indicated that after the treatment by MBR, substantial amounts of E1, estrone-3-sulfate (E1-3S), estrone-3-glucuronide (E1-3G), and 17beta-estradiol-glucuronides (E2-G) passed through treatment systems and entered into the aquatic environment. The reduction in the levels of overall equivalent E1 (68.4%) and that of overall equivalent E2 (80.8%) was demonstrated for the pilot-scale MBR-B. For alkylphenol compounds, bisphenol A (BPA) was removed well with a removal efficiency of 68.9 -90.1%, but 4-nonylphenol (4-NP) concentration was amplified (removal efficiency of -439.5 to -161.1%) after MBR treatment which could be caused by the transformation of its parent compounds, nonylphenol polyethoxylates (NPnEOs). The amounts of adsorbed estrogens per kg dry mass was relatively low, due to short hydraulic retention time and high mixed liquor suspended solids in MBRs, compared to that in STPs.     

Occurrence of a nitro metabolite of a defined nonylphenol isomer in soil/sewage sludge mixtures

Uniformly [14C]-ring-labeled 4-(3,5-dimethyl-3-heptyl)phenol (353-nonylphenol) is a highly relevant isomer of the technical nonylphenol mixture. We studied the sorption, desorption, and degradation of the synthesized isomer in an agricultural sandy loam at various soil/sewage sludge ratios. Sorption of 353-nonylphenol was high and differed with the amount of suspended soil in water. log Koc values, which are used to assess the risk of nonylphenol, ranged from 3.80 to 5.75. Desorption was slow and low and resulted in constant concentrations of about 15 ng/L353-nonylphenol in water after several desorption steps. In degradation studies up to 6% of the applied 353-nonylphenol in soil was volatilized; we consider this an important source of nonylphenol in the environment. With increasing amounts of sewage sludge in the soil/sewage sludge mixtures, 353-nonylphenol was stabilized, probably because of the lack of oxygen in sludge aggregates even under oxic conditions in flow-through systems. Unexpectedly, a less-polar metabolite was detected in amounts up to 40% of the applied nonylphenol after 135 days of incubation. This novel metabolite was identified as 4-(3,5-dimethyl-3-heptyl)-2-nitrophenol. This product formation might indicate the existence of novel metabolic pathways of nonylphenol in the environment.     

Fate of naphthalene in laboratory-scale bioretention cells: implications for sustainable stormwater management

Bioretention cells are increasingly popular in low-impact development as a means to sustainably mitigate the environmental problems associated with stormwater runoff. Yet, much remains to be known regarding the removal and ultimate fate of pollutants such as petroleum hydrocarbons in bioretention cells. In this work, laboratory-scale bioretention cells were constructed inside sealed glass columns. The columns were periodically spiked with (14)C-naphthalene over a 5-month period and the fate of this representative hydrocarbon and the influence of vegetation on naphthalene fate was studied. Three column setups were used: one planted with a legume (Purple Prairie Clover, Dalea purpureum), one planted with grass (Blue-Joint Grass, Calamagrostis canadensis), and one unplanted (i.e., control). Overall naphthalene removal efficiency was 93% for the planted columns and 78% for the control column. Adsorption to soil was the dominant naphthalene removal mechanism (56-73% of added naphthalene), although mineralization (12-18%) and plant uptake (2-23%) were also important. Volatilization was negligible (<0.04%). Significant enrichment of naphthalene-degrading bacteria occurred due to contaminant exposure and plant growth as evidenced by increased biodegradation activity and increased naphthalene dioxygenase gene concentrations in the bioretention media. This research suggests that bioretention is a viable solution for sustainable petroleum hydrocarbon removal from stormwater, and that vegetation can enhance overall performance and stimulate biodegradation.     

Effects of microbial degradation of biofoulants on microfiltration membrane performance in a membrane bioreactor

In membrane bioreactors (MBRs) for wastewater treatment, membrane fouling, particularly biofouling caused by soluble microbial products (SMP), is a nuisance problem causing decreases in permeation flux. In a previous study, we identified primary biofoulants of microfiltration (MF) membranes in SMP as polysaccharides containing uronic acids that undergo inter- and intramolecular ionic cross-linking by polyvalent cations, forming a gelatinous mass that clogs membrane pores. In the present study, we therefore attempted to isolate biofoulant-degrading microorganisms from activated sludge on a polygalacturonic acid-overlaid agar medium and evaluate their efficiency for preventing biofouling of MF membranes. Among the isolates, the fungal strain HO1 identified as Phialemonium curvatum degraded 30% of polysaccharides containing uronic acids into smaller molecules in a SMP solution containing a high concentration of saccharides after 30 days of cultivation. Microfiltration tests using a laboratory-scale submerged MBR indicated that the filtration resistance of this degraded SMP solution was lower than that of the control SMP solution without fungal inoculation. Importantly, accumulation of gelatinous mass on the membrane responsible for biofouling was avoided in the SMP solution augmented with P. curvatum HO1 during the microfiltration test. This is the first report to describe a new method for avoiding biofouling of MBRs by microbial degradation of primary biofoulants.     

Characterization of cake layer in submerged membrane bioreactor

Cake layer formation on the membrane surface has been a major challenge in the operation of membrane bioreactors (MBRs). In this study, the cake layer formation mechanism in an MBR used for synthetic wastewater treatment was investigated. The major components of cake layer were systematically examined by particle size analyzer (PSA), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray fluorescence (XRF), energy-diffusive X-ray analyzer (EDX), and Fourier transform infrared (FTIR) spectroscopy. The results indicate that the small particles in sludge suspension had a strong deposit tendency on the membrane surface. The SEM and CLSM analysis exhibited that bacterial clusters and polysaccharides were significant contributors to membrane fouling. The main components of biopolymers were identified as proteins and polysaccharide materials by the FTIR. The examination by EDX and XRF demonstrated that Mg, Al, Ca, Si, and Fe were the major inorganic elements in fouling cake. Furthermore, the results suggest that bridging between deposited biopolymers and inorganic compounds could enhance the compactness of fouling layer. During the operation of MBRs, the biopolymers and inorganic elements in the bioreactor should be controlled to minimize membrane fouling.     

野生酵母菌在膜生物反应器中的适应性培养与发酵动力学研究

进行了野生酵母菌在硅橡胶膜生物反应器长期封闭循环连续发酵环境中的多轮发酵-优势菌株筛选-转移培养的适应性进化实验,研究了菌株的发酵性能变化和发酵动力学.发酵实验共进行了5轮,每轮发酵持续时间500h,且采用前一轮发酵残液中筛选出的优势菌株作为发酵菌种.第4轮、第5轮发酵实验在乙醇产率、乙醇生成比速率、细胞比生长率等发酵性能上较第一轮有显著提高.多轮适应性培养有效增强了酵母细胞对乙醇的耐受力以及缩短了发酵适应期.     

Fate of octyl- and nonylphenol ethoxylates and some carboxylated derivatives in three american wastewater treatment plants

The fate of a comprehensive group of nonylphenol and octylphenol ethoxylates (APEOs) and several of their carboxylated derivatives was studied in three American wastewatertreatment plants (WWTPs), two of which included advanced treatment. Influent and effluent concentrations of the alkylphenolic compounds (APEs) in the three plants were very similar, but effluent concentrations showed a seasonal dependency: both carboxylate and ethoxylate concentrations in the effluents were higher in winter than in summer. Sorption to particulate matter was higher for nonylphenolic compounds than for their octylphenolic counterparts, in agreement with their difference in Kow values. Both effluent concentrations and the removal efficiency of the APEOs were strongly correlated to water temperature, but no correlation was found with suspended solids or organic carbon removal. Although APEO removal from wastewater was high, overall removal from the WWTPs, including APEOs in waste sludge and transformation products, was relatively low and suggested that advanced treatment does not invariably result in better APEO removal. Additionally, a survey of urban sewers suggested that household products still constitute an important source of the APEOs reaching WWTPs.     

Removal of sulfur-organic polar micropollutants in a membrane bioreactor treating industrial wastewater

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

Biodegradability of 14C-labeled antibiotics in a modified laboratory scale sewage treatment plant at environmentally relevant concentrations

For all new pharmaceuticals, an environmental risk assessment (ERA) has to be performed according to guidelines developed by the European Medicines Evaluation Agency. An important factor of this procedure is the assessment of the predicted environmental concentration in the aquatic environment, which is significantly influenced by the biodegradability of pharmaceuticals in sewage treatment plants. Established standardized methods for determining biodegradation under laboratory conditions apply to substance concentrations, which are much higherthan those expected in reality. Against this background, the laboratory scale sewage treatment plant (LSSTP), as described by the Organisation for Economic Cooperation and Development (OECD) Guideline No. 303A, was modified to construct a lossless system, which allows laboratory testing at realistic concentrations. To verify the experimental setup, the antibiotics benzylpenicillin, ceftriaxone, and trimethoprim were tested at low concentrations (microg/L) using 14C-labeled compounds. The results show that approximately 25% of benzylpenicillin was mineralized, whereas ceftriaxone and trimethoprim were not mineralized at all. Due to the high total recoveries of added radioactivity (> or =95%) and the fact that the findings comply with available literature data, the lossless operation of the test system could be proved. Consequently, the modified LSSTP is a suitable tool to determine more realistic biodegradation data required for the exposure assessment within the scope of an ERA for pharmaceuticals.     

Correlating TMP increases with microbial characteristics in the bio-cake on the membrane surface in a membrane bioreactor

Subcritical flux operation is widely practiced in membrane bioreactors (MBRs) to avoid severe membrane fouling and, thus, to maintain sustainable permeability. Filtration at a constant subcritical flux, however, usually leads to a two-stage increase in the transmembrane pressure (TMP): initially slowly, then abruptly. We have investigated the mechanism of this two-stage TMP increase through analyses of the structure and microbial characteristics of the bio-cake formed on the membrane. The MBR was operated under various subcritical and supercritical flux conditions. Under subcritical conditions, we observed the typical two-stage TMP increase. When a constant flux augmented and reached the supercritical conditions, however, the dual TMP change gradually transformed into a steeper, one-stage TMP increase. The second stage TMP increase under the subcritical flux was closely related to the sudden increase in the concentration of extra-cellular polymeric substances (EPSs) at the bottom layer of the bio-cake; we attribute the one-stage TMP increase under the supercritical conditions to the accumulation of microbial flocs and the reduced porosity of the bio-cake under compression. We explain the variation of the EPS concentration in the bio-cake in terms of the spatial and temporal changes of the live-to-dead ratio along the depth of the bio-cake.     

MBR工艺处理印染废水的研究进展

纺织是高能耗、高污染行业,印染废水对我国环境影响巨大.近几十年,众多学者对印染废水的处理技术进行了大量研究.其中,膜生物反应器(M B R)由于占地面积小、出水水质好、污泥浓度高、污泥产率低等被用作处理印染废水的首选工艺之一.梳理了MBR工艺处理印染废水的研究文献,总结亟需解决的难题.     

Fate of nonylphenol ethoxylates and their metabolites in two Dutch estuaries: evidence of biodegradation in the field

The environmental behavior of nonylphenol ethoxylates (A9PEO) and their metabolites was investigated in field studies in the two Dutch estuaries Western Scheldt and the Rhine estuary. Using liquid chromatography-electrospray mass spectrometry (LC-ES-MS) analysis after solid-phase extraction, A9PEO, nonylphenol (NP), and the carboxylated metabolites (A9PEC) were determined in surface water and sediments. Maximum dissolved concentrations of 2.3, 0.9, and 8.1 microg L(-1), respectively, were found. In sediments, maximum concentrations of 242 and 1080 ng g(-1) for A9PEO and NP were observed. In almost half of the sediment samples, concentrations of A9PEC in sediments were below the detection limit. Occasionally relatively high values were observed, with a maximum of 239 ng g(-1). Metabolites of the carboxy alkylphenoxy ethoxy acetic acids (CAPEC) type could not be detected in any of the sediment or water samples. In the Scheldt estuary, dissolved concentration profiles showed nonconservative behaviorfor all detected compound groups. While A9PEO and NP concentrations strongly decreased along the salinity gradient, this decrease was weaker for the A9PEC metabolites. The increasing concentration ratio of A9PEC/A9PEO clearly illustratesthe important role that aerobic biodegradation plays in the estuarine fate of these compounds. It is concluded that the oxidative hydrolytic degradation pathway is the main degradation route in this nonstratified estuary. At high salinities, where concentrations drop to background levels of around 50 ng L(-1), this ratio decreases to about unity. Simple model calculations show that this can be explained if continuous diffuse discharges (e.g. from the intensive shipping in the estuary) are assumed. For the stratified Rhine estuary the water concentration profiles are less pronounced, possibly due to more complicated and turbulent water flows and point sources from the Rotterdam harbors.     

Characterization of membrane bioreactor for dry wine production

Characteristics of yeast growth and ethanol fermentation were examined in membrane bioreactor using a grape juice. After inoculation, batch fermentation was carried out for 24 h. When yeast growth reached the stationary phase, continuous fermentation was initiated. In continuous fermentation, a linear relationship was observed between cell concentration and dilution rate. In single-vessel membrane bioreactor, the cell concentrations of 18.7 g/l and 76.9 g/l (15 and 60 times higher than that of the batch fermentation, respectively) were observed at dilution rates of 0.1 h(-1) and 0.3 h(-1), respectively. The residual sugar concentration was higher than 10 g/l at the dilution rate of 0.1 h(-1), 0.2 h(-1) or 0.3 h(-1), therefore the single-vessel membrane bioreactor was not suitable for producing dry wine (sugar concentration: 4 g/l or less). In the double-vessel membrane bioreactor, it is most suitable to set the recycle ratio at 0.15 for keeping the sugar concentration below 4 g/l. The productivity of dry wine in the double-vessel membrane bioreactor was 28 times higher than that in the batch fermentation.     

Characteristics of a self-forming dynamic membrane coupled with a bioreactor for municipal wastewater treatment

A self-forming dynamic membrane (SFDM) method that used the biomass layer formed on a coarse mesh to effect solid-liquid separation was proposed. A 100-microm Dacron mesh material was used to make the SFDM modules. A SFDM coupled bioreactor (SFDMBR) was tested to treat actual municipal wastewater, and the performance and mechanisms of the SFDM were investigated. The SFDMBR worked by gravity filtration, and the water head drop was generally <5 cm. The effluent suspended solid concentrations were undetectable in most cases, and the COD and NH3 N removal efficiencies averaged 84.2% and 98.03%, respectively. An aeration in situ was adequate for cleaning the clogged modules, and the SFDM was readily and quickly re-formed. The biomass layer of the SFDM consisted of a cake layer and a gel layer. The gel layer had structures like conventional membranes and acted the key role in the SFDM. The permeability of the used mesh attached to the gel layer could be improved because the gel layer made the filtration surface more hydrophilic.     

The effects of intermittent aeration on the characteristics of bio-cake layers in a membrane bioreactor

The effects of a sequencing variation for dissolved oxygen (DO) concentrations on the membrane permeability in a submerged membrane bioreactor (MBR) were studied. An MBR was continuously operated under alternating DO conditions, e.g., 36 h of an aerobic phase, followed by 36 h of an anoxic phase. The rate of increase in transmembrane pressure (TMP) in the anoxic phase was always steeper than that in the aerobic phase, indicating that the fouling rate was higher in the anoxic than in the aerobic condition. Regardless of the phases, the rate of TMP increase became steeper as the cycles were repeated. However, this trend became less important as the cycle numbers increased. Even in identical microbial communities, the number of colloidal particles and soluble extracellular polymeric substances (EPS) in the bulk solution were increased during the anoxic condition, which caused a reduction in the porosity of the bio-cake. During analysis of the bio-cake profile along the cake depth, the temporal variation of the bio-cake structure was attributed to the temporal change in the number of colloidal particles as well as the change in compression forces acting on the bio-cake. The influence of the latter was found to be more important than that of the former, which was verified by comparing the various structures of bio-cake formed in differing DO environments.     

Effects of muffin processing on fumonisins from 14C-labeled toxins produced in cultured corn kernels

The persistence of fumonisins during cooking is known to be affected by several factors, including thermal degradation and the presence of various ingredients in corn-based food recipes that can react with the toxin. A method for the production of corn kernels containing 14C-fumonisins was developed. The corn kernels were colonized by Fusarium verticillioides MRC 826 and supplemented with 1,2-14C-sodium acetate. The specific activity of 14C-FB1 produced made the study of its fate in cornmeal muffins possible. The double-extraction acetonitrile-water-methanol/immunoaffinity column/o-phthaldialdehyde high-performance liquid chromatography (HPLC) method was used to determine FB1 levels in cornmeal muffins. Reductions in FB1 levels in muffins spiked with 14C-labeled and unlabeled FB1 (43 and 48%, respectively) were similar, indicating that the extraction method was efficient and consistent with previous reports. However, with the labeled corn kernel material, recovery levels based on the 14C counts for the eluate from an immunoaffinity column were much higher (90%). This finding indicates that some fumonisin-related compounds other than FB1 that were present in the cornmeal were recognized by the antibodies but not by the HPLC method.     

Performance of a sulfide-oxidizing, sulfur-producing membrane biofilm reactor treating sulfide-containing bioreactor effluent

Sulfide-containing waste streams are generated in mining, petrochemical plants, tanneries, viscose rayon manufacture, and the gasification of coal. Colorless sulfur bacteria can oxidize sulfide to elemental sulfur (S°), which can be recovered, when oxygen is their electron acceptor. This study evaluated sulfide oxidation and S° recovery in an oxygen-based membrane biofilm reactor (MBfR) treating the effluent from a sulfidogenic anaerobic baffled reactor. Sulfide oxidation efficiency (37-99%) and S° recovery (64-89% of oxidized sulfide) could be controlled by manipulating the sulfide loading, oxygen pressure to the fibers, and hydraulic retention time (HRT). For example, too-low oxygen pressure decreased S° recovery due to decreased sulfide oxidation, but too-high oxygen pressure lowered S° recovery due to its oxidation to sulfate. Most importantly, high sulfide oxidation (>98%) and conversion to S° (>75%) could be achieved together when the sulfide loading was less than 1.7 mol/m2·d and the O? pressure was sufficient to give an O? flux of at least 1.5 mol/m2·d. However, higher sulfide loading could be compensated by a higher O? pressure, and the best performance occurred when the sulfide loading was high (2 molS/m2·d), the O? pressure was high (～1 atm), and the HRT was short (1.9 h). Membrane fouling caused a low O? flux, which led to low sulfide-oxidation efficiency, but fouling could be reversed by mild acid washing.     

Fate of surfactants in membrane bioreactors and conventional activated sludge plants

Two membrane bioreactors (MBRs) were operated at high sludge retention time (SRT) (between 30 and 75 d) in parallel to a conventional activated sludge plant (CASP) conducted at SRT = 10 d. The fate of linear alkylbenzene sulfonate (LAS), nonylphenol ethoxylates (NP(n)EO, n = 1-15), nonylphenoxy carboxylates (NP(n)EC, n = 1-2), and nonylphenol (NP) in these systems was investigated. All systems were very efficient in the removal of LAS (around 99%). The analysis of variance showed that the difference in the removal efficiency of LAS in the CASP and the MBR operated at SRT = 65-75 d (respectively 99.0 ± 0.43 and 99.8 ± 0.11) were significant (p < 0.05), confirming the importance of SRT in the removal of LAS. Comparison between the CASP and the MBRs in the removal efficiency of nonylphenolic compounds were conducted considering NP(3-15)EO, the sum of NP(1-15)EO, NP(1-2)EC, and nonylphenol (NP). In all cases MBRs were more efficient than the CASP. In the case of NP the removal was about 76 ± 7.5% for the CASP and 90% ± 12.1 and 82 ± 8.7% for the MBRs. Better performance of MBRs in the removal of nonylphenolic compounds can be attributed to a better degradation. For example, if the sum of NP(1-15)EO and NP(1-2)EC is considered, estimated biodegradation was about 48% for the CASP and 72% for MBRs.