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Biotransformation of nitrogen- and sulfur-containing pollutants during coking wastewater treatment: Correspondence of performance to microbial community functional structure
No full textAlthough coking wastewater is generally considered to contain high concentration of nitrogen-and sulfur-containing pollutants, the biotransformation processes of these compounds have not been well understood. Herein, a high throughput functional gene array (GeoChip 5.0) in combination with Illumina MiSeq sequencing of the 16S rRNA gene were used to identify microbial functional traits and their role in biotransformation of nitrogen-and sulfur-containing compounds in a bench-scale aerobic coking wastewater treatment system operated for 488 days. Biotransformation of nitrogen and sulfur-containing pollutants deteriorated when pH of the bioreactor was increased to > 8.0, and the microbial community functional structure was significantly associated with pH (Mantels test, P < 0.05). The release of ammonia nitrogen and sulfate was correlated with both the taxonomic and functional microbial community structure (P < 0.05). Considering the abundance and correlation with the release of ammonia nitrogen and sulfate, aromatic dioxygenases (e.g. xylXY, nagG), nitrilases (e.g. nhh, nitrilase), dibenzothiophene oxidase (DbtAc), and thiocyanate hydrolase (scnABC) were important functional genes for biotransformation of nitrogen-and sulfur-containing pollutants. Functional characterization of taxa and network analysis suggested that Burkholderiales, Actinomycetales, Rhizobiales, Pseudomonadales, and Hydrogenophiliales (Thiobacillus) were key functional taxa. Variance partitioning analysis showed that pH and influent ammonia nitrogen jointly explained 25.9% and 35.5% of variation in organic pollutant degrading genes and microbial community structure, respectively. This study revealed a linkage between microbial community functional structure and the likely biotransformation of nitrogen-and sulfurcontaining pollutants, along with a suitable range of pH (7.0-7.5) for stability of the biological system treating coking wastewater. (C) 2017 Elsevier Ltd. All rights reserved
Isolation and characterization of a virulent bacteriophage infecting Acinetobacter johnsonii from activated sludge
No full textA double-stranded DNA phage named AJO1, infecting Acinetobacter johnsonii, which plays an important role in wastewater treatment, was isolated from activated sludge in a full-scale municipal wastewater treatment plant. Based on morphological taxonomy, AJO1, with an icosahedral head 55 +/- 2 nm in diameter and a non-contractile tail 8 +/- 2 nm in length, was classified as a member of the Podoviridae family. Bacterial infection characteristics were as follows: no polyvalent infectivity, optimal multiplicity of infection of 10(-2); eclipse and burst size of 30 min and 51.2 PFU-infected cells(-1), respectively. It showed considerable infectivity under a neutral pH condition (pH 6.0-9.0) and relatively high temperature (55 degrees C). Whole-genome sequencing of AJO1 revealed a linearly permuted DNA (41 437 bp) carrying 54 putative open reading frames and 4 repeats. This is the first report of isolation of an A. johnsonii phage, whose bacteriophage distribution and population dynamics are not well known. The results of this study could contribute to subsequent research on the interaction between bacteriophages and their hosts during wastewater treatment. In addition, AJO1 may become a candidate for potential therapy against A. johnsonii infection in clinical applications, since this species is an opportunistic pathogen. (C) 2017 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved
Nanostructure-induced colored TiO2 array photoelectrodes with full solar spectrum harvesting
No full textDifferent from regular bandgap narrowing for better sunlight absorption, a series of nanostructure-induced wedge-shaped colored TiO2 array photoelectrodes exhibited full solar spectrum light harvesting and enhanced performances exemplified by photoelectrochemical (PEC) degradation of Ni(II)-EDTA. Finite element method (FEM) simulation confirmed the influence of the nano-structure towards light absorption in UV, visible, and near-infrared (NIR) regions
Pyrosequencing analysis of source water switch and sulfate-induced bacterial community transformation in simulated drinking water distribution pipes
No full textInter-basin water transfer and source water switching will be increasingly launched due to significant population increase and the shortage of the local water resources in cities around the world. Source water switch may cause physiochemical and microbiological de-stabilization of pipe material, biofilms, and loose deposits in drinking water distribution system (DWDS). Great sulfate alteration during source water switch had been deemed as the main cause of a red water case that occurred in a northern China city. To ascertain the relationship between water quality changing and bacterial communities of biofilms in DWDS and possible bacteria risk in a red water case, water quality changing experiments in simulated DWDSs were conducted for approximately 2 years. Twenty-five corrosion scale samples and eight water samples collected from pipe harvest sites or during experimental periods were analyzed for their bacterial community composition by 454-pyrosequencing technology. Taxonomy results together with redundancy analysis (RDA) or canonical correspondence analysis (CCA) and hierarchical cluster analysis all indicated that bacterial community of samples with groundwater (GW) or surface water (SW) supply history and their variations under high sulfate water were rather different owing to different water source histories and the original pipe scale characteristics. Potential opportunistic pathogens: Burkholderia, Escherichia-Shigella, Mycobacterium, Serratia, Ralstonia, Novosphingobium, Flavobacterium, Sphingomonas, and Sphingopyxis were observed in scale or water samples
Reduced graphene oxide-NH2 modified low pressure nanofiltration composite hollow fiber membranes with improved water flux and antifouling capabilities
No full textReduced graphene oxide-NH2 (R-GO-NH2), a kind of amino graphene oxide, was embedded into the polyamide (PA) layer of nanofiltration (NF) composite hollow fiber membranes via interfacial polymerization to enhance the permeate flux and antifouling properties of NF membranes under low pressure conditions. In addition, it could mitigate the poor compatibility issue between graphene oxide materials and PA layer. To evaluate the influence of R-GO-NH2 on the performance of the NF composite hollow fiber membrane, SEM, AFM, FTIR, XPS and Zeta potentials were used to characterize the membranes. The results indicated that the compatibility and interactions between R-GO-NH2 and PA layer were enhanced, which was mainly due to the polymerization reaction between amino groups of R-GO-NH2 and acyl chloride groups of TMC. Therefore, salts rejection of the current membranes was improved significantly, and the modified membranes with 50 mg/L R-GO-NH2 demonstrated highest performance in terms of the rejections, which were 26.9%, 98.5%, 98.1%, and 96.1%, for NaCl, Na2SO4, MgSO4, and CaCl2 respectively. It was found that with the R-GO-NH2 contents rasing from 0 to 50 mg/L, pure water flux increased from 30.44 +/- 1.71 to 38.57 +/- 2.01 L/(m(2).h) at 2 bar. What's more, the membrane demonstrated improved antifouling properties. (C) 2017 Elsevier B.V. All rights reserved
Sulfamethazine degradation in water by the VUV/UV process: Kinetics, mechanism and antibacterial activity determination based on a mini-fluidic VUV/UV photoreaction system
No full textA mini-fluidic VUV/UV photoreaction system (MVPS) was developed in our previous study, and it was demonstrated as a powerful tool for studies on pollutant degradation by the VUV/UV process. In this study, we investigated the VUV/UV photodegradation of sulfamethazine (SMN), one of the most frequently detected antibiotics in the environment. The determination methods of photochemical kinetic parameters (e.g., photon fluence-based rate constant and quantum yield) were developed based on the MVPS. The photon fluence-based reaction rate constants for SMN degradation by UV alone and VUV/UV processes were determined as 0.07 x 10(3) and 4.11 x 10(3) m(2) einstein(-1), respectively, while their quantum yields were calculated as 0.019 and 0369, respectively. The second-order reaction rate constant between hydroxyl radical (HO center dot) and SMN was determined to be 8.9 x 109 M-1 s(-1) in VUV/UV irradiation experiments, which were conducted without addition of any other chemical. The pH effect on the SMN degradation by the VUV/UV process arose principally from SMN and HO center dot speciation. In addition, six byproducts were identified and the potential degradation pathways of SMN including hydroxylation and SO2 elimination were proposed. The antibacterial activity of the SMN solution, assessed by the growth inhibition tests of Escherichia coli, decreased by about 80% after VUV/UV treatment up to a photon fluence of 3.58 x 10(-3) einstein m(-2). This study has developed methods for the determination of photochemical kinetic parameters using the newly developed MVPS and has demonstrated that the VUV/UV process is an effective technology to remove sulfonamide antibiotics in water. (C) 2016 Elsevier Ltd. All rights reserved
Benchmarking the scientific research on wastewater-energy nexus by using bibliometric analysis
No full textWith an exponential increase in urbanization and industrialization, water pollution is an inevitable consequence of relatively lagging wastewater treatment facilities. The conventional activated sludge process for wastewater treatment primarily emphasizes the removal of harmful substances to maintain increasingly stringent effluent discharged standards, which is considered an energy-intensive technique. Therefore, innovative and sustainable wastewater treatment should pay more attention to energy and resource recovery in dealing with fossil fuel depletion, global-scale energy security, and climate change. A bibliometric analysis was applied to trace wastewater-energy nexus-related research during the period 1991 to 2015, with respect to the Science Citation Index EXPANDED (SCI-EXPANDED) database. Journal of Hazardous Materials, ranking 1st in h-index (79), was the most productive journal (431, 4.5%) during the same time, followed by International Journal of Hydrogen Energy (422, 4.4%) and Water Research (393, 4.1%) journal, the latter owning a topmost journal impact factor. Though, China (2154, 22.5%) was the most productive country, while the USA with highest h-index (88) was the favorest collaborative country. The Chinese Academy of Sciences, China (241, 2.5%) produced the maximum publications. A novel method called "word cluster analysis" showed that the emerging sustainable processes and novel renewable energy application are applied in response to the desire for a net wastewater-energy nexus system. Based on different wastewater types, the emerging energy and sources recovery treatment processes of Anammox, anaerobic digestion, and microbial fuel cells gained extensive innovation. Evaluation indicators including sustainability, life cycle assessment, and environmental impact were appropriately used to dissert feasibility of the novel treatment methods in regard of renewable energy utilization, energy savings, and energy recovery. The transformation of the new concept of "broaden income source, economize on expenditures and exploit inner potential" should be generalized in order to achieve an environmentally sustainable development of wastewater-energy nexus system
Ultrasound assisted alkaline pretreatment to enhance enzymatic saccharification of grass clipping
No full textGrass clipping, a cellulose-rich raw material, has great potential to produce biofuels, but must be firstly hydrolyzed to liberate fermentable sugars. In this study, grass clipping was pretreated with ultrasound (US), Ca (OH)(2), NaOH, US-Ca(OH)(2) and US-NaOH at relatively low temperature to enhance its enzymatic hydrolysis. The solubilization of hemicellulose and lignin, and crystallinity index of cellulose increased after US-alkaline pretreatment, leading to a significant increase of enzyme accessibility to cellulose. Compared with another four pretreatments, US-Ca(OH)(2) pretreatment of grass clipping showed the best improvement for reducing sugar yield. X-ray diffraction (XRD) determination and scanning electron microscope (SEM) observation showed that the crystallinity index of grass clipping increased and the grass clipping surface suffered from serious erosion after US-Ca(OH)(2) pretreatment. Then, the operating conditions of US-Ca(OH)(2) pretreatment and enzymatic hydrolysis were systematically optimized, and the suitable operating conditions were as follows: US power density of 0.65 W/ml, US pretreatment time of 30 min, Ca(OH)(2) concentration of 0.75%, pretreatment temperature of 75 degrees C, enzyme loading of 125 FPU/g, and hydrolysis time of 72 h. The reducing sugar yield of grass clipping pretreated by US-Ca(OH)(2) reached 414 mg/g, increasing by 3.5 times compared with that of raw grass clipping. The US-Ca(OH)(2) pretreatment of grass clipping at low temperature significantly enhanced the potential of grass clipping as a promising raw material to produce biofuels
Distribution of antibiotic resistance in the effluents of ten municipal wastewater treatment plants in China and the effect of treatment processes
No full textMunicipal wastewater treatment plant (WWTP) effluents represent an important contamination source of antibiotic resistance, threatening the ecological safety of receiving environments. In this study, the release of antibiotic resistance to sulfonamides and tetracyclines in the effluents of ten WWTPs in China was investigated. Results indicate that the concentrations of antibiotic -resistant bacteria (ARB) and antibiotic resistance genes (ARGs) ranged from 1.1 x 10(1) to 8.9 x 10(3) CFU mL(-1) and 3.6 x 10(1) (tetW) to 5.4 x 10(6) (tetX) copies mL(-1), respectively. There were insignificant correlations of the concentrations of ARB and ARGs with those of corresponding antibiotics. Strong correlations were observed between the total concentrations of tetracycline resistance genes and sulfonamide resistance genes, and both of which were significantly correlated with intl1 concentrations. Statistical analysis of the effluent ARG concentrations in different WWTPs revealed an important role of disinfection in eliminating antibiotic resistance. The release rates of ARB and ARGs through the effluents of ten WWTPs ranged from 5.9 x 10(12) to 4.8 x 10(15) CFU d(-1) and 6.4 x 10(12) (tetW) to 1.7 x 10(18) (sul1) copies d(-1), respectively. This study helps the effective assessment and scientific management of ecological risks induced by antibiotic resistance discharged from WWTPs. (C) 2017 Elsevier Ltd. All rights reserved
Insights into heterogeneous catalytic activation of peroxymonosulfate by Pd/g-C3N4: The role of superoxide radical and singlet oxygen
No full textPd nanoparticles anchored on graphitic nitride carbon (Pd/g-C3N4) hybrid catalytic system was prepared by a simple KBH4 reduction method. Pd/g-C3N4 was very active in the degradation of bisphenol A (BPA) by efficiently activating peroxymonosulfate (PMS). Important influencing factors, such as catalyst dosage, PMS concentration, pH and reaction temperature for the BPA removal were investigated. Pd/g-C3N4-PMS demonstrated a wide effective pH range, namely 3.0-9.0. Radical quenching tests and electron spin response (ESR) analyses revealed that superoxide radical (O-2 center dot(-)) and singlet oxygen (O-1(2)) instead of sulfate radical (SO4 center dot(-)) and hydroxyl radicals (" OH) were the major oxidized species for the degradation of BPA