Frontiers of Environmental Science & Engineering

ISSN 2095-2201

ISSN 2095-221X(Online)

CN 10-1013/X

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Municipal wastewater treatment in China: Development history and future perspectives
Jiuhui Qu, Hongchen Wang, Kaijun Wang, Gang Yu, Bing Ke, Han-Qing Yu, Hongqiang Ren, Xingcan Zheng, Ji Li, Wen-Wei Li, Song Gao, Hui Gong
Front. Environ. Sci. Eng.    2019, 13 (6): 88-.   https://doi.org/10.1007/s11783-019-1172-x
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The history of China’s municipal wastewater management is revisited.

The remaining challenges in wastewater sector in China are identified.

New concept municipal wastewater treatment plants are highlighted.

An integrated plant of energy, water and fertilizer recovery is envisaged.

China has the world’s largest and still growing wastewater sector and water market, thus its future development will have profound influence on the world. The high-speed development of China’s wastewater sector over the past 40 years has forged its global leading treatment capacity and innovation ability. However, many problems were left behind, including underdeveloped sewers and sludge disposal facilities, low sustainability of the treatment processes, questionable wastewater treatment plant (WWTP) effluent discharge standards, and lacking global thinking on harmonious development between wastewater management, human society and the nature. Addressing these challenges calls for fundamental changes in target design, policy and technologies. In this mini-review, we revisit the development history of China’s municipal wastewater management and identify the remaining challenges. Also, we highlight the future needs of sustainable development and exploring China’s own wastewater management path, and outlook the future from several aspects including targets of wastewater management, policies and technologies, especially the new concept WWTP. Furthermore, we envisage the establishment of new-generation WWTPs with the vision of turning WWTP from a site of pollutant removal into a plant of energy, water and fertilizer recovery and an integrated part urban ecology in China.

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Cited: WebOfScience(2)
Excitation-emission matrix (EEM) fluorescence spectroscopy for characterization of organic matter in membrane bioreactors: Principles, methods and applications
Jinlan Yu, Kang Xiao, Wenchao Xue, Yue-xiao Shen, Jihua Tan, Shuai Liang, Yanfen Wang, Xia Huang
Front. Environ. Sci. Eng.    2020, 14 (2): 31-.   https://doi.org/10.1007/s11783-019-1210-8
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• Principles and methods for fluorescence EEM are systematically outlined.

• Fluorophore peak/region/component and energy information can be extracted from EEM.

• EEM can fingerprint the physical/chemical/biological properties of DOM in MBRs.

• EEM is useful for tracking pollutant transformation and membrane retention/fouling.

• Improvements are still needed to overcome limitations for further studies.

The membrane bioreactor (MBR) technology is a rising star for wastewater treatment. The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter (DOM) in the system. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, a powerful tool for the rapid and sensitive characterization of DOM, has been extensively applied in MBR studies; however, only a limited portion of the EEM fingerprinting information was utilized. This paper revisits the principles and methods of fluorescence EEM, and reviews the recent progress in applying EEM to characterize DOM in MBR studies. We systematically introduced the information extracted from EEM by considering the fluorescence peak location/intensity, wavelength regional distribution, and spectral deconvolution (giving fluorescent component loadings/scores), and discussed how to use the information to interpret the chemical compositions, physiochemical properties, biological activities, membrane retention/fouling behaviors, and migration/transformation fates of DOM in MBR systems. In addition to conventional EEM indicators, novel fluorescent parameters are summarized for potential use, including quantum yield, Stokes shift, excited energy state, and fluorescence lifetime. The current limitations of EEM-based DOM characterization are also discussed, with possible measures proposed to improve applications in MBR monitoring.

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Elimination of antibiotic resistance genes and control of horizontal transfer risk by UV-based treatment of drinking water: A mini review
Virender K. Sharma, Xin Yu, Thomas J. McDonald, Chetan Jinadatha, Dionysios D. Dionysiou, Mingbao Feng
Front. Environ. Sci. Eng.    2019, 13 (3): 37-.   https://doi.org/10.1007/s11783-019-1122-7
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Antibiotic-resistant bacteria and antibiotic resistance genes are in water bodies.

UV/chlorination method is better to remove ARGs than UV or chlorination alone.

Research on UV/hydrogen peroxide to eliminate ARGs is forthcoming.

UV-based photocatalytic processes are effective to degrade ARGs.

Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have been recognized as one of the biggest public health issues of the 21st century. Both ARB and ARGs have been determined in water after treatment with conventional disinfectants. Ultraviolet (UV) technology has been seen growth in application to disinfect the water. However, UV method alone is not adequate to degrade ARGs in water. Researchers are investigating the combination of UV with other oxidants (chlorine, hydrogen peroxide (H2O2), peroxymonosulfate (PMS), and photocatalysts) to harness the high reactivity of produced reactive species (Clž·, ClOž·ž, Clž2·ž, žž·OH, and SOž4ž·€) in such processes with constituents of cell (e.g., deoxyribonucleic acid (DNA) and its components) in order to increase the degradation efficiency of ARGs. This paper briefly reviews the current status of different UV-based treatments (UV/chlorination, UV/H2O2, UV/PMS, and UV-photocatalysis) to degrade ARGs and to control horizontal gene transfer (HGT) in water. The review also provides discussion on the mechanism of degradation of ARGs and application of q-PCR and gel electrophoresis to obtain insights of the fate of ARGs during UV-based treatment processes.

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Impacts of advanced treatment processes on elimination of antibiotic resistance genes in a municipal wastewater treatment plant
Lian Yang, Qinxue Wen, Zhiqiang Chen, Ran Duan, Pan Yang
Front. Environ. Sci. Eng.    2019, 13 (3): 32-.   https://doi.org/10.1007/s11783-019-1116-5
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The distributions of ARGs were monitored in a WWTP in Harbin during six months.

CASS had the best removal efficacy of ARGs compared to other processes in the WWTP.

UV disinfection could effectively control the HGT.

AGAC significantly remove ARGs and organics due to its high absorption capacity.

Combination of ozone and AGAC significantly improve removal of ARGs and organics.

Antibiotic resistance genes (ARGs) pose a serious threat to public health. Wastewater treatment plants (WWTPs) are essential for controlling the release of ARGs into the environment. This study investigated ARG distribution at every step in the treatment process of a municipal WWTP located in Harbin for six consecutive months. Changes in ARG distribution involved in two advanced secondary effluent treatment processes, ozonation and granular activated carbon (GAC) adsorption, were analyzed. Biological treatment resulted in the highest ARG removal (0.76–1.94 log reduction), followed by ultraviolet (UV) disinfection (less than 0.5-log reduction). Primary treatment could not significantly remove ARGs. ARG removal efficiency increased with an increase in the ozone dose below 40 mg/L. However, amorphous GAC (AGAC) adsorption with a hydraulic retention time (HRT) of 1 h showed better removal of ARGs, total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) than ozonation at a 60 mg/L dose. UV treatment could efficiently reduce the relative ARG abundance, despite presenting the lowest efficiency for the reduction of absolute ARG abundance compared with GAC and ozone treatments. The combination of ozone and AGAC can significantly improve the removal of ARGs, TOC, TN and TP. These results indicate that a treatment including biological processing, ozonation, and AGAC adsorption is a promising strategy for removing ARGs and refractory organic substances from sewage.

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Influence of hydraulic retention time on behavior of antibiotics and antibiotic resistance genes in aerobic granular reactor treating biogas slurry
Jie Liao, Chaoxiang Liu, Lin Liu, Jie Li, Hongyong Fan, Jiaqi Ye, Zhichao Zeng
Front. Environ. Sci. Eng.    2019, 13 (3): 31-.   https://doi.org/10.1007/s11783-019-1115-6
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Longer HRT can enhance degradation rate of sulfamethoxazole in granular reactor.

Longer HRT can reduce accumulated concentrations of TCs and QNs in sludge.

Longer HRT may have increased relative abundances of ARGs in aerobic granules.

The behavior of antibiotics and the corresponding resistance genes in aerobic granular reactors for treating biogas slurry under different hydraulic retention times (10.7 h, R1; 8 h, R2) was investigated in this study. The results indicated that the hydraulic retention time could affect the effluent concentrations and removal efficiencies of sulfonamides. The average removal rates of tetracyclines, fluoroquinolones, and sulfonamides were 63%, 46%, and 90% in R1, and 62%, 46%, and 86% in R2, respectively. Although the removal efficiencies of tetracyclines and fluoroquinolones were similar in both reactors, the respective accumulated concentrations of tetracyclines and fluoroquinolones in R1 were 7.00 and 11.15 µg/g SS, which were lower than those in R2 (8.92 and 13.37 µg/g SS, respectively). The difference in the relative abundance of target antibiotic resistance genes between both reactors was not significant, yet the average relative abundances of all target resistance genes in R1 were higher than those in R2 after 45 days of operation. The results of this study suggested that a longer hydraulic retention time could enhance the antibiotic removal ability of aerobic granular sludge, yet it may also increase the risk of surplus sludge utilization from a resistance genes point of view.

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Combined Fenton process and sulfide precipitation for removal of heavy metals from industrial wastewater: Bench and pilot scale studies focusing on in-depth thallium removal
Huosheng Li, Hongguo Zhang, Jianyou Long, Ping Zhang, Yongheng Chen
Front. Environ. Sci. Eng.    2019, 13 (4): 49-.   https://doi.org/10.1007/s11783-019-1130-7
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Addition of alkali to pH 10 is effective for precipitation of precipitable metals.

Fenton treatment is effective for substantial removal of Tl, Cd, Cu, Pb, and Zn.

Sulfide precipitation is a final step for removal of trace Tl, Cd, Cu, Pb, and Zn.

Bench and pilot studies demonstrated the effectiveness of this combined technique.

Thallium (Tl) in industrial wastewater is a public health concern due to its extremely high toxicity. However, there has been limited research regarding Tl removal techniques and engineering practices to date. In this investigation, bench and pilot studies on advanced treatment of industrial wastewater to remove Tl to a trace level were conducted. The treatment process involved a combination of hydroxide precipitation, Fenton oxidation, and sulfide precipitation. While hydroxide precipitation was ineffective for Tl+ removal, it enabled the recovery of approximately 70%–80% of Zn as Zn hydroxide in alkaline conditions. The Fenton process provided good Tl removal (>95%) through oxidation and precipitation. Tl was then removed to trace levels (<1.0 µg/L) via sulfide precipitation. Effective removal of other heavy metals was also achieved, with Cd<13.4 µg/L, Cu<39.6 µg/L, Pb<5.32 µg/L, and Zn<357 µg/L detected in the effluent. X-ray photoelectron spectroscopy indicated that Tl2S precipitate formed due to sulfide precipitation. Other heavy metals were removed via the formation of metal hydroxides during hydroxide precipitation and Fenton treatment, as well as via the formation of metal sulfides during sulfide precipitation. This combined process provides a scalable approach for the in-depth removal of Tl and other heavy metals from industrial wastewater.

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Cited: Crossref(6) WebOfScience(13)
Presence, dissemination and removal of antibiotic resistant bacteria and antibiotic resistance genes in urban drinking water system: A review
Qiaowen Tan, Weiying Li, Junpeng Zhang, Wei Zhou, Jiping Chen, Yue Li, Jie Ma
Front. Environ. Sci. Eng.    2019, 13 (3): 36-.   https://doi.org/10.1007/s11783-019-1120-9
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Reviewed the change of ARGs and ARB in full-scale urban drinking water systems.

Conventional processes are more promising than BAC process in ARGs removal.

Mechanisms of ARGs enrichment and spread in BAC filter and DWDSs are discussed.

Raise the need of future research on ARGs and ARB change in building plumbing systems.

Antibiotic resistance in aquatic environment has become an important pollution problem worldwide. In recent years, much attention was paid to antibiotic resistance in urban drinking water systems due to its close relationship with the biosafety of drinking water. This review was focused on the mechanisms of antibiotic resistance, as well as the presence, dissemination and removal of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the urban drinking water system. First, the presence of ARB and ARGs in the drinking water source was discussed. The variation of concentration of ARGs and ARB during coagulation, sedimentation and filtration process were provided subsequently, in which filtration was proved to be a promising technology to remove ARGs. However, biological activated carbon (BAC) process and drinking water distribution systems (DWDSs) could be incubators which promote the antibiotic resistance, due to the enrichment of ARGs and ARB in the biofilms attached to the active carbon and pipe wall. Besides, as for disinfection process, mechanisms of the inactivation of ARB and the promotion of conjugative transfer of ARGs under chlorine, ozone and UV disinfection were described in detail. Here we provide some theoretical support for future researches which aim at antibiotic resistance controlling in drinking water.

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Environmental Antibiotics and Antibiotic Resistance: From Problems to Solutions
Xin Yu, Virender K. Sharma, Hui Li
Front. Environ. Sci. Eng.    2019, 13 (3): 47-null.   https://doi.org/10.1007/s11783-019-1137-0
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Association between heavy metals and antibiotic-resistant human pathogens in environmental reservoirs: A review
Christine C. Nguyen, Cody N. Hugie, Molly L. Kile, Tala Navab-Daneshmand
Front. Environ. Sci. Eng.    2019, 13 (3): 46-.   https://doi.org/10.1007/s11783-019-1129-0
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Heavy metals can act as co-selecting agents and promote antibiotic resistance.

Most frequent resistances to heavy metals are observed for zinc and cadmium.

P. aeruginosa and E. coli are commonly resistant to heavy metals and antibiotics.

Heavy metals proliferate antibiotic resistance through co- and cross-resistance.

Heavy metal and antibiotic resistances are common near anthropogenic activities.

Antibiotic resistance in human pathogens can proliferate under selective pressures. Heavy metals in environmental reservoirs may contribute to selecting antibiotic-resistant strains. To determine the associations between heavy metals and antibiotic resistance, a literature review was conducted to systematically collect and categorize evidence for co-occurrence of resistance to heavy metals and antibiotics within human pathogenic bacteria in water, wastewater, and soil. In total, 42 publications adhered to inclusion criteria. Across the reservoirs, zinc and cadmium were the most commonly observed heavy metals associated with resistance to antibiotics. Pseudomonas aeruginosa and Escherichia coli were the most commonly studied bacteria with reported co-occurrence of resistance to several heavy metals and antibiotic classes. As co-selecting agents, prevalence of heavy metals in the environment can proliferate resistance to heavy metals and antibiotics through co-resistance and cross-resistance mechanisms. In comparing different reservoirs, soils and sediments harbor higher heavy metal and antibiotic resistances compared to water environments. Additionally, abiotic factors such as pH can affect the solubility and hence, the availability of heavy metals to bacterial pathogens. Overall, our review demonstrates heavy metals act as co-selecting agents in the proliferation of antibiotic resistance in human pathogens in multiple environmental reservoirs. More studies that include statistical data are needed to further describe the exposure-response relationships between heavy metals and antibiotic resistance in different environmental media. Moreover, integration of culture-based and molecular-based methods in future studies are recommended to better inform our understanding of bacterial co- and cross-resistance mechanisms to heavy metals and antibiotics.

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Culturomics and metagenomics: In understanding of environmental resistome
Monika Nowrotek, Łukasz Jałowiecki, Monika Harnisz, Grażyna Anna Płaza
Front. Environ. Sci. Eng.    2019, 13 (3): 40-.   https://doi.org/10.1007/s11783-019-1121-8
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State of the art of culturomics and metagenomics to study resistome was presented.

The combination of culturomics and metagenomics approaches was proposed.

The research directions of antibiotic resistance study has been suggested.

Pharmaceutical residues, mainly antibiotics, have been called “emerging contaminants” in the environment because of their increasing frequency of detection in aquatic and terrestrial systems and their sublethal ecological effects. Most of them are undiscovered. Both human and veterinary pharmaceuticals, including antibiotics, are introduced into the environment via many different routes, including discharges from municipal wastewater treatment plants and land application of animal manure and biosolids to fertilize croplands. To gain a comprehensive understanding of the widespread problem of antibiotic resistance, modern and scientific approaches have been developed to gain knowledge of the entire antibiotic-resistant microbiota of various ecosystems, which is called the resistome. In this review, two omics methods, i.e. culturomics, a new approach, and metagenomics, used to study antibiotic resistance in environmental samples, are described. Moreover, we discuss how both omics methods have become core scientific tools to characterize microbiomes or resistomes, study natural communities and discover new microbes and new antibiotic resistance genes from environments. The combination of the method for get better outcome of both culturomics and metagenomics will significantly advance our understanding of the role of microbes and their specific properties in the environment.

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FESE’s Best Papers of 2018
Front. Environ. Sci. Eng.    2019, 13 (3): 48-null.   https://doi.org/10.1007/s11783-019-1138-z
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Aggravation of membrane fouling and methane leakage by a three-phase separator in an external anaerobic ceramic membrane bioreactor
Chao Pang, Chunhua He, Zhenhu Hu, Shoujun Yuan, Wei Wang
Front. Environ. Sci. Eng.    2019, 13 (4): 50-.   https://doi.org/10.1007/s11783-019-1131-6
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The existence of three-phase separator did not affect COD removal in the EAnCMBR.

The existence of three-phase separator aggravated methane leakage of EAnCMBR.

The existence of three-phase separator aggravated membrane fouling rate of EAnCMBR.

Start-up of EAnCMBR equipped three-phase separator was slightly delayed.

The three-phase separator is a critical component of high-rate anaerobic bioreactors due to its significant contribution in separation of biomass, wastewater, and biogas. However, its role in an anaerobic membrane bioreactor is still not clear. In this study, the distinction between an external anaerobic ceramic membrane bioreactor (EAnCMBR) unequipped (R1) and equipped (R2) with a three-phase separator was investigated in terms of treatment performance, membrane fouling, extracellular polymers of sludge, and microbial community structure. The results indicate that the COD removal efficiencies of R1 and R2 were 98.2%±0.4% and 98.1%±0.4%, respectively, but the start-up period of R2 was slightly delayed. Moreover, the membrane fouling rate of R2 (0.4 kPa/d) was higher than that of R1 (0.2 kPa/d). Interestingly, the methane leakage from R2 (0.1 L/d) was 20 times higher than that from R1 (0.005 L/d). The results demonstrate that the three-phase separator aggravated the membrane fouling rate and methane leakage in the EAnCMBR. Therefore, this study provides a novel perspective on the effects of a three-phase separator in an EAnCMBR.

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Nanoscale zero-valent iron supported on biochar for the highly efficient removal of nitrobenzene
Gaoling Wei, Jinhua Zhang, Jinqiu Luo, Huajian Xue, Deyin Huang, Zhiyang Cheng, Xinbai Jiang
Front. Environ. Sci. Eng.    2019, 13 (4): 61-.   https://doi.org/10.1007/s11783-019-1142-3
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• Biochar supported nanoscale zero-valent iron composite (nZVI/BC) was synthesized.

• nZVI/BC quickly and efficiently removed nitrobenzene (NB) in solution.

• NB removal by nZVI/BC involves simultaneous adsorption and reduction mechanism.

• nZVI/BC exhibited better catalytic activity, stability and durability than nZVI.

The application of nanoscale zero-valent iron (nZVI) in the remediation of contaminated groundwater or wastewater is limited due to its lack of stability, easy aggregation and iron leaching. To address this issue, nZVI was distributed on oak sawdust-derived biochar (BC) to obtain the nZVI/BC composite for the highly efficient reduction of nitrobenzene (NB). nZVI, BC and nZVI/BC were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). For nZVI/BC, nZVI particles were uniformly dispersed on BC. nZVI/BC exhibited higher removal efficiency for NB than the simple summation of bare nZVI and BC. The removal mechanism was investigated through the analyses of UV-Visible spectra, mass balance and XPS. NB was quickly adsorbed on the surface of nZVI/BC, and then gradually reduced to aniline (AN), accompanied by the oxidation of nZVI to magnetite. The effects of several reaction parameters, e.g., NB concentration, reaction pH and nZVI/BC aging time, on the removal of NB were also studied. In addition to high reactivity, the loading of nZVI on biochar significantly alleviated Fe leaching and enhanced the durability of nZVI.

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Advances in Fe(III) bioreduction and its application prospect for groundwater remediation: A review
Yu Jiang, Beidou Xi, Rui Li, Mingxiao Li, Zheng Xu, Yuning Yang, Shaobo Gao
Front. Environ. Sci. Eng.    2019, 13 (6): 89-.   https://doi.org/10.1007/s11783-019-1173-9
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Microbial Fe(III) reduction is closely related to the fate of pollutants.

Bioavailability of crystalline Fe(III) oxide is restricted due to thermodynamics.

Amorphous Fe(III) (hydro)oxides are more bioavailable.

Enrichment and incubation of Fe(III) reducing bacteria are significant.

Microbial Fe(III) reduction is a significant driving force for the biogeochemical cycles of C, O, P, S, N, and dominates the natural bio-purification of contaminants in groundwater (e.g., petroleum hydrocarbons, chlorinated ethane, and chromium). In this review, the mechanisms and environmental significance of Fe(III) (hydro)oxides bioreduction are summarized. Compared with crystalline Fe(III) (hydro)oxides, amorphous Fe(III) (hydro)oxides are more bioavailable. Ligand and electron shuttle both play an important role in microbial Fe(III) reduction. The restrictive factors of Fe(III) (hydro)oxides bioreduction should be further investigated to reveal the characteristics and mechanisms of the process. It will improve the bioavailability of crystalline Fe(III) (hydro)oxides and accelerate the anaerobic oxidation efficiency of the reduction state pollutants. Furthermore, the approach to extract, culture, and incubate the functional Fe(III) reducing bacteria from actual complicated environment, and applying it to the bioremediation of organic, ammonia, and heavy metals contaminated groundwater will become a research topic in the future. There are a broad application prospects of Fe(III) (hydro)oxides bioreduction to groundwater bioremediation, which includes the in situ injection and permeable reactive barriers and the innovative Kariz wells system. The study provides an important reference for the treatment of reduced pollutants in contaminated groundwater.

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Increasing prevalence of antibiotic resistance genes in manured agricultural soils in northern China
Nan Wu, Weiyu Zhang, Shiyu Xie, Ming Zeng, Haixue Liu, Jinghui Yang, Xinyuan Liu, Fan Yang
Front. Environ. Sci. Eng.    2020, 14 (1): 1-.   https://doi.org/10.1007/s11783-019-1180-x
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• Manure application increased the abundances of ARGs and MGEs in agricultural soils.

• Five classes of ARGs and two MGEs were prevalent in manured and unfertilized soils.

• Genera Pseudomonas and Bacteroidetes might be the dominant hosts of intI1 and ermF.

• The abundances of ARGs positively correlated with TC, TN, OM, Cu, Zn, Pb and MGEs.

Land application of manure tends to result in the dissemination of antibiotic resistance in the environment. In this study, the influence of long-term manure application on the enrichment of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in agricultural soils was investigated. All the analyzed eight ARGs (tetA, tetW, tetX, sulI, sulII, ermF, aac(6’)-Ib-cr and blaTEM) and two MGEs (intI1 and Tn916/1545) were detected in both the manured and control soils, with relative abundances ranging from 10-6 to 10-2. Compared with the control soil, the relative abundances of ARGs and MGEs in manured soils were enriched 1.0–18.1 fold and 0.6–69.1 fold, respectively. High-throughput sequencing analysis suggested that at the phylum level, the bacteria carrying intI1 and ermF might be mainly affiliated with Proteobacteria and Bacteroides, respectively. The dominant genera carrying intI1 and ermF could be Pseudomonas and Bacteroides, independent of manure application. Correlation analysis revealed that ARGs had strong links with soil physicochemical properties (TC, TN, and OM), heavy metals (Cu, Zn and Pb) and MGEs, indicating that the profile and spread of ARGs might be driven by the combined impacts of multiple factors. In contrast, soil pH and C/N exhibited no significant relationships with ARGs. Our findings provide evidence that long-term manure application could enhance the prevalence and stimulate the propagation of antibiotic resistance in agricultural soils.

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G-CNTs/PVDF mixed matrix membranes with improved antifouling properties and filtration performance
Xiaoyan Guo, Chunyu Li, Chenghao Li, Tingting Wei, Lin Tong, Huaiqi Shao, Qixing Zhou, Lan Wang, Yuan Liao
Front. Environ. Sci. Eng.    2019, 13 (6): 81-.   https://doi.org/10.1007/s11783-019-1165-9
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A novel nanocomposite OMWCNT-A-GO was synthesized by conjugating OMWCNT and GO.

The P-OMWCNT-A-GO membrane was fabricated by non-solvent induced phase inversion.

The P-OMWCNT-A-GO exhibits the best water flux, BSA rejection and flux recovery.

It should be due to the enhanced membrane pore size, porosity and hydrophilicity.

Although carbon nanomaterials have been widely used as effective nanofillers for fabrication of mixed matrix membranes (MMMs) with outstanding performances, the reproducibility of the fabricated MMMs is still hindered by the non-homogenous dispersion of these carbon nanofillers in membrane substrate. Herein, we report an effective way to improve the compatibility of carbon-based nanomaterials with membrane matrixes. By chemically conjugating the oxidized CNTs (o-CNTs) and GO using hexanediamine as cross-linker, a novel carbon nanohybrid material (G-CNTs) was synthesized, which inherited both the advanced properties of multi-walled carbon nanotubes (CNTs) and graphene oxide (GO). The G-CNTs incorporated polyvinylidene fluoride (PVDF) MMMs (G-CNTs/PVDF) were fabricated via a non-solvent induced phase separation (NIPS) method. The filtration and antifouling performances of G-CNTs/PVDF were evaluated using distillate water and a 1 g/L bovine serum albumin (BSA) aqueous solution under 0.10 MPa. Compared to the MMMs prepared with o-CNTs, GO, the physical mixture of o-CNTs and GO and pure PVDF membrane, the G-CNTs/PVDF membrane exhibited the highest water flux up to 220 L/m2/h and a flux recovery ratio as high as 90%, as well as the best BSA rejection rate. The excellent performances should be attributed to the increased membrane pore size, porosity and hydrophilicity of the resulted membrane. The successful synthesis of the novel nanohybrid G-CNTs provides a new type of nanofillers for MMMs fabrication.

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Characteristic and correlation analysis of influent and energy consumption of wastewater treatment plants in Taihu Basin
Luxi Zou, Huaibo Li, Shuo Wang, Kaikai Zheng, Yan Wang, Guocheng Du, Ji Li
Front. Environ. Sci. Eng.    2019, 13 (6): 83-.   https://doi.org/10.1007/s11783-019-1167-7
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Poor biodegradability and insufficient carbon source are discovered from influent.

Influent indices presented positively normal distribution or skewed distribution.

Average energy consumption of WWTPs in Taihu Basin was as high as 0.458 kWh/m3.

Energy consumption increases with the increase in influent volume and COD reduction.

The total energy consumption decreases with the NH3-N reduction.

The water quality and energy consumption of wastewater treatment plants (WWTPs) in Taihu Basin were evaluated on the basis of the operation data from 204 municipal WWTPs in the basin by using various statistical methods. The influent ammonia nitrogen (NH3-N) and total nitrogen (TN) of WWTPs in Taihu Basin showed normal distribution, whereas chemical oxygen demand (COD), biochemical oxygen demand (BOD5), suspended solid (SS), and total phosphorus (TP) showed positively skewed distribution. The influent BOD5/COD was 0.4%–0.6%, only 39.2% SS/BOD5 exceeded the standard by 36.3%, the average BOD5/TN was 3.82, and the probability of influent BOD5/TP>20 was 82.8%. The average energy consumption of WWTPs in Taihu Basin in 2017 was 0.458 kWh/m3. The specific energy consumption of WWTPs with a daily treatment capacity of more than 5 × 104 m3 in Taihu Basin was stable at 0.33 kWh/m3. A power function relationship was observed between the reduction in COD and NH3-N and the specific energy consumption of pollutant reduction, and the higher the pollutant reduction is, the lower the specific energy consumption of pollutant reduction presents. In addition, a linear relationship existed between the energy consumption of WWTPs and the specific energy consumption of influent volume and pollutant reduction. Therefore, upgrading and operation with less energy consumption of WWTPs is imperative and the suggestions for Taihu WWTPs based on stringent discharge standard are proposed in detail.

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Membrane-based treatment of shale oil and gas wastewater: The current state of knowledge
Tiezheng Tong, Kenneth H. Carlson, Cristian A. Robbins, Zuoyou Zhang, Xuewei Du
Front. Environ. Sci. Eng.    2019, 13 (4): 63-.   https://doi.org/10.1007/s11783-019-1147-y
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• Shale oil and gas production generates wastewater with complex composition.

• Membrane technologies emerged for the treatment of shale oil and gas wastewater.

• Membrane technologies should tolerate high TDS and consume low primary energy.

• Pretreatment is a key component of integrated wastewater treatment systems.

• Full-scale implementation of membrane technologies is highly desirable.

Shale oil and gas exploitation not only consumes substantial amounts of freshwater but also generates large quantities of hazardous wastewater. Tremendous research efforts have been invested in developing membrane-based technologies for the treatment of shale oil and gas wastewater. Despite their success at the laboratory scale, membrane processes have not been implemented at full scale in the oil and gas fields. In this article, we analyze the growing demands of wastewater treatment in shale oil and gas production, and then critically review the current stage of membrane technologies applied to the treatment of shale oil and gas wastewater. We focus on the unique niche of those technologies due to their advantages and limitations, and use mechanical vapor compression as the benchmark for comparison. We also highlight the importance of pretreatment as a key component of integrated treatment trains, in order to improve the performance of downstream membrane processes and water product quality. We emphasize the lack of sufficient efforts to scale up existing membrane technologies, and suggest that a stronger collaboration between academia and industry is of paramount importance to translate membrane technologies developed in the laboratory to the practical applications by the shale oil and gas industry.

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Cited: WebOfScience(1)
Analysis of antibiotic resistance of Escherichia coli isolated from the Yitong River in North-east China
Yangyang Yu, Xiaolin Zhu, Guanlan Wu, Chengzhi Wang, Xing Yuan
Front. Environ. Sci. Eng.    2019, 13 (3): 39-.   https://doi.org/10.1007/s11783-019-1123-6
Abstract   HTML   PDF (774KB)

The concentrations of four types of antibiotics in the Yitong River were detected.

The concentration of total coliforms in summer was higher than that in spring.

There was a seasonal difference in antibiotic resistance of E. coli.

The E. coli in the Yitong River was found to have multiple antibiotic resistance.

The Yitong River is one of the largest secondary tributaries of the Songhua River. The area where the Yitong River flows is densely populated and contains the livestock and poultry breeding areas of north-east China. These areas introduce a high risk of antibiotic contamination. In this study, the concentrations of four types of typical antibiotics including quinolones, tetracyclines, sulfonamides, and trimethoprim were determined by solid phase extraction-high performance liquid chromatography. The antibiotic resistance of Escherichia coli caused by antibiotic pollution was investigated. The concentration of total coliforms in the Yitong River was detected by the plate counting method. The antibiotic resistance of E. coli to quinolones, tetracyclines, sulfonamides, and trimethoprim was analyzed by the Kirby-Bauer method. The results showed that the concentration of total coliforms in the summer was higher than that in the spring. There was a seasonal difference in the resistance rate of E. coli to antibiotics except trimethoprim. The antibiotic resistance to fluoroquinolones was relatively low. The resistance rate to tetracyclines was higher during the summer. Moreover, resistance to several antibiotics was observed in all sections. This study provides basic data for research on pollution characteristics and prevention of antibiotic exposure in rivers.

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Screening of textile finishing agents available on the Chinese market: An important source of per- and polyfluoroalkyl substances to the environment
Mehvish Mumtaz, Yixiang Bao, Wenchao Li, Lingxiao Kong, Jun Huang, Gang Yu
Front. Environ. Sci. Eng.    2019, 13 (5): 67-.   https://doi.org/10.1007/s11783-019-1145-0
Abstract   HTML   PDF (619KB)

Kendrick mass defect was used for PFASs screening in textile finishing agents (TFAs).

Total oxidizable precursor assay provides insight into unknown precursors.

Perfluorooctane sulfonate was found as impurity in short ECF technology based TFAs.

Perfluorooctanoate was also detected in C6 telomerization based TFAs.

Long chain precursors were also observed in both types of TFAs.

Organofluorinated surfactants are widely employed in textile finishing agents (TFAs) to achieve oil, water, and stain repellency. This has been regarded as an important emission source of per-and polyfluoroalkyl substances (PFASs) to the environment. China is the biggest manufacturer of clothes, and thus TFA production is also a relevant industrial activity. Nevertheless, to date, no survey has been conducted on PFAS contents in commercially available TFAs. In the present study, TFA products were investigated by the Kendrick mass defect method. The quantification results demonstrated a significant presence of perfluorooctane sulfonate (0.37 mg/L) in TFAs manufactured by electrochemical fluorination technology. The products obtained by short-chain PFAS-based telomerization were dominated by perfluorooctanoic acid (mean concentration: 0.29 mg/L), whose values exceeded the limits stated in the European Chemical Agency guidelines (0.025 mg/L). Moreover, the total oxidizable precursor assay indicated high levels of indirectly quantified precursors with long alkyl chains (C7–C9). Together, these results suggest that there is currently a certain of environmental and health risks in China that originates from the utilization of TFAs, and a better manufacturing processes are required to reduce such risks.

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Attached cultivation of Scenedesmus sp. LX1 on selected solids and the effect of surface properties on attachment
Victor M. Deantes-Espinosa, Tian-Yuan Zhang, Xiao-Xiong Wang, Yinhu Wu, Guo-Hua Dao, Hong-Ying Hu
Front. Environ. Sci. Eng.    2019, 13 (4): 57-.   https://doi.org/10.1007/s11783-019-1141-4
Abstract   HTML   PDF (1376KB)

Attachment of Scenedesmus sp. LX1 was tested on certain materials.

A criterion for selection of materials was used to choose seven materials.

The amount of S. sp. LX1 attached on polyurethane foam was 51.74 mg/L.

Materials’ surface influenced the attachment of microalgae.

Hydrophilic and hydrophobic properties also affected the attachment of S. sp. LX1.

Attached cultivation systems in the literature do not present a methodology to screen materials for microalgal growth. Hence, a method is needed to find suitable materials for attached cultivation that may enhance attachment of microalgae. In this paper, we have tested seven materials culturing Scenedesmus sp. LX1 (S. sp. LX1) to evaluate the attachment of microalgae on the material surface, its growth in suspension phase and the properties of the materials. Two materials showed attachment of S. sp. LX1, polyurethane foam and loofah sponge, and allowed microalgae to grow both in the surface of the material and suspended phase. Polyurethane foam proved to be a good material for attachment of S. sp. LX1 and the amount of attached microalgae obtained was 51.73 mg/L when adding 100 pieces/L. SEM images showed that the surface and the pore size of the materials affected the attachment of the microalgae, increasing its attachment in scaffold-like materials. Furthermore, the hydrophilic and hydrophobic properties of the materials also affected the attachment of microalgae. This research can be used as a methodology to search for the assessment of a material suitable for attachment of microalgae.

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Degradation of extracellular genomic, plasmid DNA and specific antibiotic resistance genes by chlorination
Menglu Zhang, Sheng Chen, Xin Yu, Peter Vikesland, Amy Pruden
Front. Environ. Sci. Eng.    2019, 13 (3): 38-.   https://doi.org/10.1007/s11783-019-1124-5
Abstract   HTML   PDF (1008KB)

Extracellular DNA structure damaged by chlorination was characterized.

Integrity of extracellular ARG genetic information after chlorination was determined.

Typical chlorine doses will likely effectively diminish extracellular DNA and ARGs.

Plasmid DNA/ARGs were less readily broken down than genomic DNA.

The Bioanalyzer methodology effectively documented damage incurred to DNA.

There is a need to improve understanding of the effect of chlorine disinfection on antibiotic resistance genes (ARGs) in order to advance relevant drinking water, wastewater, and reuse treatments. However, few studies have explicitly assessed the physical effects on the DNA. Here we examined the effects of free chlorine (1–20 mg Cl2/L) on extracellular genomic, plasmid DNA and select ARGs. Chlorination was found to decrease the fluorometric signal of extracellular genomic and plasmid DNA (ranging from 0.005 to 0.05 mg/mL) by 70%, relative to a no-chlorine control. Resulting DNA was further subject to a fragment analysis using a Bioanalyzer, indicating that chlorination resulted in fragmentation. Moreover, chlorine also effectively deactivated both chromosomal- and plasmid-borne ARGs, mecA and tetA, respectively. For concentrations >2 mg Cl2//L × 30 min, chlorine efficiently reduced the qPCR signal when the initial concentration of ARGs was 105 copies/mL or less. Notably, genomic DNA and mecA gene signals were more readily reduced by chlorine than the plasmid-borne tetA gene (by ~2 fold). Based on the results of qPCR with short (~200 bps) and long amplicons (~1200 bps), chlorination could destroy the integrity of ARGs, which likely reduces the possibility of natural transformation. Overall, our findings strongly illustrate that chlorination could be an effective method for inactivating extracellular chromosomal- and plasmid-borne DNA and ARGs.

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Transmembrane transport of polycyclic aromatic hydrocarbons by bacteria and functional regulation of membrane proteins
Hongqi Wang, Ruhan Jiang, Dekang Kong, Zili Liu, Xiaoxiong Wu, Jie Xu, Yi Li
Front. Environ. Sci. Eng.    2020, 14 (1): 9-.   https://doi.org/10.1007/s11783-019-1188-2
Abstract   HTML   PDF (1873KB)

• Explaintheadsorption, uptake and transmembrane transport of PAHs by bacteria.

• Analyze functional regulation of membrane proteins inthe transmembrane transport.

• Proteomics technology such as iTRAQ labeling was used to access expressed proteins.

• Single cell analysis technology wereused to study the morphological structure.

In recent years, increasing research has been conducted on transmembrane transport processes and the mechanisms behind the microbial breakdown of polycyclic aromatic hydrocarbons (PAHs), including the role of membrane proteins in transmembrane transport and the mode of transmission. This article explains the adsorption, uptake and transmembrane transport of PAHs by bacteria, the regulation of membrane protein function during the transmembrane transport. There are three different regulation mechanisms for uptake, depending on the state and size of the oil droplets relative to the size of the microbial cells, which are (i) direct adhesion, (ii) emulsification and pseudosolubilization, and (iii) interfacial uptake. Furthermore, two main transmembrane transport modes are introduced, which are (i) active transport and (ii) passive uptake and active efflux mechanism. Meanwhile, introduce the proteomics and single cell analysis technology used to address these areas of research, such as Isobaric tags for relative and absolute quantitation (iTRAQ) technology and Nano Secondary ion mass spectrometry (Nano-SIMS). Additionally, analyze the changes in morphology and structure and the characteristics of microbial cell membranes in the process of transmembrane transport. Finally, recognize the microscopic mechanism of PAHs biodegradation in terms of cell and membrane proteins are of great theoretical and practical significance for understanding the factors that influence the efficient degradation of PAHs contaminants in soil and for remediating the PAHs contamination in this area with biotechnology.

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Effects of cultivation strategies on the cultivation of Chlorella sp. HQ in photoreactors
Xiaoya Liu, Yu Hong, Peirui Liu, Jingjing Zhan, Ran Yan
Front. Environ. Sci. Eng.    2019, 13 (5): 78-.   https://doi.org/10.1007/s11783-019-1162-z
Abstract   HTML   PDF (559KB)

Heterotrophic cultivation caused high level of ROS and high lipids accumulation.

HMTC is the best culture strategy for improving the microalgal biomass.

Chlorella sp. HQ had great nutrient removal capacity under five culture strategies.

The effects of cultivation strategies (including autotrophic cultivation (AC), heterotrophic cultivation (HC), fed-batch cultivation (FC), heterotrophic+ autotrophic two-stage cultivation (HATC), and heterotrophic+ mixotrophic two-stage cultivation (HMTC)) on the growth and lipid accumulation of Chlorella sp. HQ and its total nitrogen (TN) and total phosphorus (TP) removal in secondary effluent were investigated in column photoreactors. The results showed that the TN and TP removal rates ranged between 93.72%–95.82% and 92.73%–100%, respectively, under the five different strategies. The microalgal growth potential evaluated by the maximal growth rate (Rmax) was in the order of HMTC>HC>FC>AC>HATC. The values of biomass, total lipid yield, triacylglycerols (TAGs) yield, and total lipid content of the microalga cultivated in the last 5 d increased significantly, but the TAGs productivities of the five strategies were lower than those in the first 7 d. Compared with all the other cultivation strategies, the TAGs productivity and yield after 12 d of cultivation under the heterotrophic condition reached the highest values accompanying the highest level of intracellular reactive oxygen species (ROS), in which the TAGs yield reached 40.81 mg/L at the end of the cultivation period. The peaks in TAGs yield and ROS level suggested that HC was beneficial for lipids accumulation via regulating the cellular redox status and exerting ROS stress on microalgal cells. In summary, HMTC was the best cultivation strategy for improving the microalgal biomass and HC was the best strategy for microalgal TAGs accumulation to produce biodiesel.

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Enhanced nitrogen removal and microbial analysis in partially saturated constructed wetland for treating anaerobically digested swine wastewater
Zhenfeng Han, Ying Miao, Jing Dong, Zhiqiang Shen, Yuexi Zhou, Shan Liu, Chunping Yang
Front. Environ. Sci. Eng.    2019, 13 (4): 52-.   https://doi.org/10.1007/s11783-019-1133-4
Abstract   HTML   PDF (1088KB)

Anaerobically digested swine wastewater was treated by a novel constructed wetland.

Tidal operation was better for total nitrogen removal than intermittent flow.

Mechanism of nitrogen removal by biozeolite-based constructed wetland was discussed.

Simultaneous nitrification and denitrification were determined in zeolite layer.

Nitrogen removal of wastewater containing high-strength ammonium by the constructed wetlands (CWs) has been paid much attention. In this study, the ability of a partially saturated CW to treat anaerobically-digested decentralized swine wastewater under varying operating parameters from summer to winter was investigated. The partially saturated CW achieved better NH4+-N and TN removal by tidal flow than intermittent flow. With surface loading rates of 0.108, 0.027, and 0.029 kg/(m2·d) for COD, NH4+-N, and TN, the partially saturated CW by tidal operation achieved corresponding removal efficiencies of 85.94%, 61.20%, and 57.41%, respectively, even at 10°C. When the rapid-adsorption of NH4+-N and the bioregeneration of zeolites reached dynamically stable, the simultaneous nitrification and denitrification in the aerobic zeolite layer was observed and accounted for 58.82% of the total denitrification of CW. The results of Illumina high-throughput sequencing also indicated that nitrifiers (Nitrospira and Rhizomicrobium) and denitrifiers (Rhodanobacter and Thauera) simultaneously existed in the zeolite layer. The dominant existence of versatile organic degraders and nitrifiers/denitrifiers in the zeolite layer was related to the removal of most COD and nitrogen in this zone. The contribution of the possible nitrogen removal pathways in the CW was as follows: nitrification-denitrification (86.55%)>substrate adsorption (11.70%)>plant uptake (1.15%)>microbial assimilation (0.60%).

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Cited: Crossref(1) WebOfScience(5)
Ozonation as an efficient pretreatment method to alleviate reverse osmosis membrane fouling caused by complexes of humic acid and calcium ion
Xuehao Zhao, Yinhu Wu, Xue Zhang, Xin Tong, Tong Yu, Yunhong Wang, Nozomu Ikuno, Kazuki Ishii, Hongying Hu
Front. Environ. Sci. Eng.    2019, 13 (4): 55-.   https://doi.org/10.1007/s11783-019-1139-y
Abstract   HTML   PDF (2877KB)

Humic acids (HA) didn’t cause obvious reverse osmosis (RO) membrane fouling in 45 h.

Osmotic pressure (NaCl) affected slightly the RO membrane fouling behavior of HA.

Ca2+ promoted aggregation of HA molecules and thus aggravated RO membrane fouling.

Ozonation eliminated the effect of Ca2+ on the RO membrane fouling behavior of HA.

The change of the structure of HA was related to its membrane fouling behavior.

Humic acid has been considered as one of the most significant sources in feed water causing organic fouling of reverse osmosis (RO) membranes, but the relationship between the fouling behavior of humic acid and the change of its molecular structure has not been well developed yet. In this study, the RO membrane fouling behavior of humic acid was studied systematically with ozonation as a pretreatment method to control RO membrane fouling. Furthermore, the effect of ozone on the structure of humic acid was also explored to reveal the mechanisms. Humic acid alone (10–90 mg/L, in deionized water) was found not to cause obvious RO membrane fouling in 45-h operation. However, the presence of Ca2+ aggravated significantly the RO membrane fouling caused by humic acid, with significant flux reduction and denser fouling layer on RO membrane, as it was observed by scanning electron microscope (SEM) and atomic force microscope (AFM). However, after the pretreatment by ozone, the influence of Ca2+ was almost eliminated. Further analysis revealed that the addition of Ca2+ increased the particle size of humic acid solution significantly, while ozonation reduced the SUVA254, particle size and molecular weight of the complexes of humic acid and Ca2+ (HA-Ca2+ complexes). According to these results and literature, the bridge effect of Ca2+ aggregating humic acid molecules and the cleavage effect of ozone breaking HA-Ca2+ complexes were summarized. The change of the structure of humic acid under the effect of Ca2+ and ozone is closely related to the change of its membrane fouling behavior.

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Cited: WebOfScience(4)
Degradation of metronidazole by dielectric barrier discharge in an aqueous solution
Zhipeng Yang, Anxing Lai, Hangyu Chen, Youxiang Yan, Ye Yang, Weiwei Zhang, Lei Wang
Front. Environ. Sci. Eng.    2019, 13 (3): 33-.   https://doi.org/10.1007/s11783-019-1117-4
Abstract   HTML   PDF (1113KB)

The discharge characteristics during the degradation of MNZ by DBD were investigated.

Increasing the discharge frequency can promote the degradation of MNZ.

MNZ removal reaches 99.1% at the initial concentration of 40 ppm within 120 min.

Coexisting organic matter inhibits the degradation of MNZ.

The energy efficiency of DBD for MNZ removal is higher than other technologies.

Degradation of metronidazole (MNZ) which is a representative and stable antibiotic by dielectric barrier discharge (DBD) in an aqueous solution has been studied. Effects of initial MNZ concentration, solution pH and coexisting organics on the degradation were investigated. The results illustrated that increasing the input power and the discharge frequency can improve the removal of MNZ. At low initial concentration, the removal of MNZ can reach up to 99.1%. Acidic and neutral conditions are more favorable for MNZ removal than alkaline condition in the early stage of degradation. However, the difference in MNZ removal between those in acidic or neutral media and that in alkaline one could be neglected with prolonging of the treatment time. Therefore, this method can be applied to MNZ degradation with a wide pH range. Coexisting organic matter in water can attenuate the removal to some extent. This study could provide valuable references for the degradation of nitroimidazole antibiotics by DBD.

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Shipboard bilge water treatment by electrocoagulation powered by microbial fuel cells
Xiaoxue Mei, Heming Wang, Dianxun Hou, Fernanda Leite Lobo, Defeng Xing, Zhiyong Jason Ren
Front. Environ. Sci. Eng.    2019, 13 (4): 53-.   https://doi.org/10.1007/s11783-019-1134-3
Abstract   HTML   PDF (1396KB)

Reveals the synergy between microbial fuel cells and electrocoagulation.

Demonstrates MFC-ECC shipboard wastewater treatment is advantageous.

MFC-ECC integration enables energy neutral bilge water treatment.

Ships generate large amounts of wastewater including oily bilge water, blackwater and greywater. Traditionally they are treated separately with high energy consumption. In this study we demonstrate the feasibility that these waste streams can be treated using an integrated electrocoagulation cell (ECC) and microbial fuel cell (MFC) process, which not only synergized the contaminants removal but also accomplished energy neutrality by directly powering EC with MFC electricity. Results showed that MFC stack powered ECC removed 93% of oily organics, which is comparable to the performance of an external DC voltage powered ECC. In the meantime, more than 80% of COD was removed from MFCs when fed with either acetate or municipal wastewater. Moreover, the ECC electrode area and distance showed notable effects on current generation and contaminants removal, and further studies should focus on operation optimization to enhance treatment efficiency.

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Distribution and removal of antibiotic resistance genes during anaerobic sludge digestion with alkaline, thermal hydrolysis and ultrasonic pretreatments
Mengli Wang, Ruying Li, Qing Zhao
Front. Environ. Sci. Eng.    2019, 13 (3): 43-.   https://doi.org/10.1007/s11783-019-1127-2
Abstract   HTML   PDF (1367KB)

Sludge digestion is critical to control the spread of ARGs from wastewater to soil.

Fate of ARGs in three pretreatment-AD processes was investigated.

UP was more efficient for ARGs removal than AP and THP in pretreatment-AD process.

The total ARGs concentration showed significant correlation with 16S rRNA gene.

The bacteria carrying ARGs could be mainly affiliated with Proteobacteria.

Sewage sludge in the wastewater treatment plants contains considerable amount of antibiotic resistance genes (ARGs). A few studies have reported that anaerobic digestion (AD) could successfully remove some ARGs from sewage sludge, but information on the fate of ARGs in sludge pretreatment-AD process is still very limited. In this study, three sludge pretreatment methods, including alkaline, thermal hydrolysis and ultrasonic pretreatments, were compared to investigate the distribution and removal of ARGs in the sludge pretreatment-AD process. Results showed that the ARGs removal efficiency of AD itself was approximately 50.77%, and if these three sludge pretreatments were applied, the total ARGs removal efficiency of the whole pretreatment-AD process could be improved up to 52.50%–75.07%. The ultrasonic pretreatment was more efficient than alkaline and thermal hydrolysis pretreatments. Although thermal hydrolysis reduced ARGs obviously, the total ARGs rebounded considerably after inoculation and were only removed slightly in the subsequent AD process. Furthermore, it was found that the total ARGs concentration significantly correlated with the amount of 16S rRNA gene during the pretreatment and AD processes, and the bacteria carrying ARGs could be mainly affiliated with Proteobacteria.

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Dechlorination of dichlorodiphenyltrichloroethane (DDT) by Fe/Pd bimetallic nanoparticles: Comparison with nZVI, degradation mechanism, and pathways
Kubra Ulucan-Altuntas, Eyup Debik
Front. Environ. Sci. Eng.    2020, 14 (1): 17-.   https://doi.org/10.1007/s11783-019-1196-2
Abstract   HTML   PDF (2298KB)

• DDT undergoes dechlorination via Fe/Pd bimetallic nanoparticle.

• The oxidation effect of nZVI on DDT is greatly improved when Pd is dopped.

• The highest concentration to be treated under cancerogenesis limit was 110 mg/L.

• The dechlorination of DDT is more like to DDE via Fe/Pd but to DDD via nZVI.

• Degradation products concentrations are lowered via Fe/Pd when compared with nZVI.

In this study, the bimetallic Fe/Pd nanoparticle was synthesized using the catalytic element palladium to increase the effect of nano zero valent iron (nZVI), in the light of the information obtained from our previous study, in which the nZVI synthesis method was modified. Dichlorodiphenyltrichloroethane (DDT), one of the most widely used persistent organic pollutant pesticides in the world, was investigated in terms of its degradation by Fe/Pd nanoparticles and the difference with nZVI was determined. During the study, the Fe/Pd concentration, initial DDT concentration, and contact time were selected as variables affecting the treatment. The highest possible initial DDT concentration for the treatment with Fe/Pd bimetallic nanoparticle was investigated to obtain the DDT effluent concentration below the carcinogenesis limit, 0.23 µg/L. The highest concentration that could be treated was found to be 109.95 mg/L with Fe/Pd. It was found that 44.3 min of contact time and 550 mg/L Fe/Pd concentration were needed to achieve this treatment.

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