Municipal sewage treatment plants (STPs) are thought to be important point sources of microplastics in freshwater systems and many peer-reviewed articles have been published on this issue since mid-2010s. In this review, we summarize existing literature on the occurrence of microplastics in STPs and experimental methods used for isolation and identification of microplastics. The number concentrations of microplastics in STP influents were 15.1-640 L⁻¹, whereas those in the STP effluents were highly variable and ranged from not detectable to 65 L⁻¹. For most of cases, conventional STPs are removing microplastics very effectively. Fragments and fibers are dominant shapes of microplastics. Thermoplastics (polyethylene and polypropylene) and polyester are the predominant materials recovered. Although further research is needed, size distribution of microplastics in STPs is likely to follow a power law, implying that different studies using different size cutoffs may be compared after establishing a power law relationship.
Fresh Water ; Jurisprudence ; Polyesters ; Sewage*

Municipal sewage treatment plants (STPs) are thought to be important point sources of microplastics in freshwater systems and many peer-reviewed articles have been published on this issue since mid-2010s. In this review, we summarize existing literature on the occurrence of microplastics in STPs and experimental methods used for isolation and identification of microplastics. The number concentrations of microplastics in STP influents were 15.1-640 L⁻¹, whereas those in the STP effluents were highly variable and ranged from not detectable to 65 L⁻¹. For most of cases, conventional STPs are removing microplastics very effectively. Fragments and fibers are dominant shapes of microplastics. Thermoplastics (polyethylene and polypropylene) and polyester are the predominant materials recovered. Although further research is needed, size distribution of microplastics in STPs is likely to follow a power law, implying that different studies using different size cutoffs may be compared after establishing a power law relationship.
Fresh Water ; Jurisprudence ; Polyesters ; Sewage

Internal-loop granular sludge bed nitrifying reactor is a new type of aerobic nitrifying equipment and has shown a good potential for nitrification. To study the flow pattern and construct the flow model, the tracer tests were performed using pulse stimulus-response technique. Based on the experimental results, the flow pattern in the settling section and the circulating section of reactor were analyzed by axial dispersion model and tank-in-series model, respectively. The dispersion number D/uL of 0.00148 in the settling section indicates that its flow pattern is similar to plug flow reactor (PFR), and the series number N of 1.021 in the circulating section indicates that its flow pattern is similar to continuously stirred tank reactor (CSTR). During steady state, the theoretic hydraulic retention time is 360 min, and the actual hydraulic retention time is 341.2 min. The percentage of dead space in the reactor is 5.22%, thereinto the dead space caused by biomass (db ) is 0.75 % and the hydraulic dead space (dh) is 4.47%, which shows that the structural performance of the reactor is excellent. Based on the experiments and analysis, a model of CSTR and PFR in series was constructed. The actual hydraulic retention time distribution of the reactor is in good agreement with the model predictions. Since the relative error between them is 8.56%, the model is accurate to describe the flow pattern. The results have laid a foundation for the kinetic model of the reactor and will be helpful for its design and operation.
Bioreactors ; Kinetics ; Models, Theoretical ; Nitrites ; metabolism ; Sewage

BACKGROUND/AIMS: Although metalic stents are established therapeutic options for the palliation of malignant biliary obstruction, it remains unclear which stricture or stent related factors affect the stent patency. METHODS: Metallic Wallstents (Microvasive, Boston-Scientific, MA, U.S.A.) were inserted endoscopically in 68 patients (mean age; 70.2+/-8.5, M:F=38:30) with malignant biliary obstruction. Patency rates were prospectively analyzed according to the characteristics of malignant strictures including length, morphologic type and degree of stricture. Furthermore, patient age, initial serum bilirubin level, the length of stent, the adequate expansion time, and the location of the distal stent end were evaluated as possible factors affecting the stent patency. Stent patency was assessed using the survival analysis of the Kaplan-Meier estimation and Cox regression analysis. RESULTS: Median overall stent patency was 231 days and overall rate of stent occlusion was 41.2% (28/68). The causes of stent blockage were tumoral ingrowth in 23 patients (33.8%), distal overgrowth of the cancer in 3 (4.4%), proximal overgrowth in 1 (1.5%) and sludge incrustation in 1 patient (1.5%). No significant differences in metallic stent patency rates according to primary tumor type, length and morphologic type of stricture, and length and location of distal end of the stent were found. Log-rank test and multivariate regression analysis, however, demonstrated that the degree of stricture assessed by cannula or guidewire passage and the adequate expansion time of the stent are independent factors associated with long-term metallic stent patency. CONCLUSIONS: Our study showed that early expansibility of the stent and easy passage of larger-caliber instruments over the stricture were favorable factors for long-term patency of the metallic stent.
Bilirubin ; Catheters ; Constriction, Pathologic ; Humans ; Prospective Studies ; Sewage ; Stents*

Homoacetogens are a group of microorganisms with application potential to produce chemicals and biofuels by the bioconversion of synthesis gas. In this study, we collected waste activated sludge samples to screen homoacetogens by Hungate anaerobic technique, and studied the effect of pH on acetate and alcohol production from H2/CO2 gas. The mixed culture contained Clostridium ljungdahlii, Lysinibacillus fusiformis and Bacillus cereus. Acetate concentration achieved 31.69 mmol/L when the initial pH was 7. The mixed culture containing homoacetogen could converting H2/CO2 to acetate, which provides an efficient microbial resource for the bioconversion of synthesis gas.
Acetates ; chemistry ; Bacteria ; classification ; Biofuels ; Carbon Dioxide ; Hydrogen ; Sewage ; microbiology

OBJECTIVETo investigate the biodegradation of tetrachloroethylene (PCE) using methanol as electron donor by acclimated anaerobic sludge.

METHODSHP-6890 gas chromatograph (GC), together with HP-7694 autosampler, was used to analyze the concentration of PCE and intermediates.

RESULTSPCE could be decholrinated reductively to DCE via TCE, and probably further to VC and ethylene. The degradation of PCE and TCE conformed to first-order reaction kinetics. The reaction rate constants were 0.8991 d(-1) and 0.068 d(-1), respectively, and the corresponding half-life were 0.77 d and 10.19 d, respectively. TCE production rate constant was 0.1333 d(-1), showing that PCE was degraded more rapidly than TCE.

CONCLUSIONMethanol is an electron donor suitable for PCE degradation and the cometabolic electron donors are not limiting factors for PCE degradation.

OBJECTIVEThis study was conducted to optimize the operational parameters of anaerobic-anoxic-oxic (A²/O) processes to reduce the toxicity of municipal wastewater and evaluate its ability to reduce toxicity.

METHODSA luminescent bacterium toxicity bioassay was employed to assess the toxicity of influent and effluent of each reactor in the A²/O system.

RESULTSThe optimum operational parameters for toxicity reduction were as follows: anaerobic hydraulic retention time (HRT) = 2.8 h, anoxic HRT = 2.8 h, aerobic HRT = 6.9 h, sludge retention time (SRT) = 15 days and internal recycle ratio (IRR) = 100%. An important toxicity reduction (%) was observed in the optimized A²/O process, even when the toluene concentration of the influent was 120.7 mg·L⁻¹.

CONCLUSIONSThe toxicity of municipal wastewater was reduced significantly during the A²/O process. A²/O process can be used for toxicity reduction of municipal wastewater under toxic-shock loading.

Microorganisms are the dominant players driving the degradation and transformation of chloramphenicol (CAP) in the environment. However, little bacterial strains are able to efficiently degrade and mineralize CAP, and the CAP degrading pathways mediated by oxidative reactions remain unclear. In this study, a highly efficient CAP-degrading microbial consortium, which mainly consists of Rhodococcus (relative abundance >70%), was obtained through an enrichment process using CAP-contaminated activated sludge as the inoculum. A bacterial strain CAP-2 capable of efficiently degrading CAP was isolated from the consortium and identified as Rhodococcus sp. by 16S rRNA gene analysis. Strain CAP-2 can efficiently degrade CAP under different nutrient conditions. Based on the biotransformation characteristics of the detected metabolite p-nitrobenzoic acid and the reported metabolites p-nitrobenzaldehyde and protocatechuate by strain CAP-2, a new oxidative pathway for the degradation of CAP was proposed. The side chain of CAP was oxidized and broken to generate p-nitrobenzaldehyde, which was further oxidized to p-nitrobenzoic acid. Strain CAP-2 can be used to further study the molecular mechanism of CAP catabolism, and has the potential to be used in in situ bioremediation of CAP-contaminated environment.
Biodegradation, Environmental ; Chloramphenicol ; RNA, Ribosomal, 16S/genetics* ; Rhodococcus/genetics* ; Sewage

In order to explore the microbial communities and functions of activated sludge in an Anaerobic-anoxic-oxic (A²/O) process under the start-up of Actinic reaction enzyme system (ARES) system and to understand the impact of the ARES system in domestic sewage treatment process, the activated sludge microbial community structure in the A²/O process system before and after ARES system start-up was analyzed by Illumina-HiSeq 2000 high-throughput sequencing platform. By combining with the main parameters related to the effect of sewage treatment, we analyzed the environmental functions of the microbial communities. The microbial community structure of activated sludge was significantly different before and after the ARES system start-up. There were 9 main bacterial phyla in the system (average relative abundance ≥1%), accounting for 96%-98% of the total bacteria sequenced. After the ARES system was started, the relative abundance of Betaproteobacteria and Chlorobi increased by 3.45%-3.85% and 0.45%-2.61%, respectively. In the anaerobic unit, the relative abundance of Bacteroidetes increased by 12.97%, while the Actinobacteria and Firmicutes decreased by 9.60% and 1.45%, respectively. At the genus level of bacteria, the relative abundance of Denitratisoma increased by 0.80%-3.27%, while the Haliangium and Arcobacter decreased by 3.36%-4.52% and 1.48%-3.45%, respectively. The relative abundance of bacteria was significantly different before and after the ARES system start-up. There were 7 abundant fungi phyla (average relative abundance ≥1%) in the system. After the ARES system was started, the relative abundance of Rozellomycota decreased by 42.71%-46.77%. In the anaerobic unit, the relative abundance of Ascomycota decreased by 13.39%, while the relative abundance of Glomeromycota increased by 13.86%. At the genus level of fungi. The relative abundance of Entomophthoraceae sp. and Glomcromycota sp. increased by 31.35%-36.50% and 6.27%-13.84%, respectively, while the Rozellomycota sp. and Xylochrysis lucida decreased by 42.71%-46.77% and 3.67%-5.54%, respectively. Our results showed that the application of ARES system caused the response of the microbial community to environmental changes, especially for the fungi communities, in the meanwhile, improved the effluent quality, especially the removal rate of total nitrogen.
Anaerobiosis ; Ascomycota ; Bioreactors ; Microbiota ; Nitrogen ; Sewage ; Waste Disposal, Fluid

Polyhydroxyalkanoates (PHA) synthesis by activated sludge using volatile fatty acids (VFAs) in fermentation liquid of excess sludge as carbon source is a hotspot in the field of environmental biotechnology. However, there is no unified conclusion on the effects of non-VFAs, mainly dissolved organic matter (DOM), on PHA production. Thus, this critical review mainly introduces the main characteristics and common analysis methods of DOM in anaerobic fermentation liquid. The effects of DOM on PHA production are analyzed from the aspects of microbiology, metabolic regulation and sludge properties. The results of different studies showed that high concentration of DOM is bad for PHA production, but an appropriate amount of DOM is conducive to the stability of sludge properties, reducing the final PHA purification cost. Finally, suitable strategies were proposed to regulate the PHA synthesis by activated sludge with DOM for PHA production by anaerobic fermentation liquid.
Anaerobiosis ; Bioreactors ; Fatty Acids, Volatile ; Fermentation ; Polyhydroxyalkanoates ; Sewage