Frontiers of Environmental Science & Engineering

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ISSN 2095-2201 (Print)
ISSN 2095-221X (Online)
CN 10-1013/X
Postal Subscription Code 80-973
Formerly Known as Frontiers of Environmental Science & Engineering in China
2018 Impact Factor: 3.883
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Municipal wastewater treatment in China: Development history and future perspectives Collection
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
Abstract   HTML   PDF (1489KB)

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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End-of-life batteries management and material flow analysis in South Korea Collection
Hyunhee Kim, Yong-Chul Jang, Yeonjung Hwang, Youngjae Ko, Hyunmyeong Yun
Front. Environ. Sci. Eng.    2018, 12 (3): 3.   https://doi.org/10.1007/s11783-018-1019-x
Abstract   HTML   PDF (660KB)

Analysis of collection and recycling system of end-of-life batteries was examined.

Relatively limited fractions of portable batteries were collected by EPR system.

More effective and diverse collection pathways should be developed.

Consumers increasingly have worn-out batteries as electrical and electronic equipment with new technical developments are introduced into the market and quickly replace older models. As a result, large amounts of end-of-life (EOL) or waste batteries are generated. Such batteries may contain a variety of materials that includes valuable resources as well as toxic elements. Thus, the proper recycling and management of batteries is very important from the perspective of resource conservation and environmental effect. The collection and recycling of EOL batteries is relatively low in South Korea compared to other countries, although an extended producer responsibility (EPR) policy was adopted for battery recycling in 2003. In this study, the management and material flow of EOL batteries is presented to determine potential problems and quantitative flow, based on literature review, site visits to battery recycling facilities, and interviews with experts in the Korea Battery Recycling Association (KBRA), manufacturers, and regulators in government. The results show that approximately 558 tons of manganese-alkaline batteries, the largest fraction among recycling target items, was disposed in landfills or incinerators in 2015, while approximately 2,000 tons of batteries were recovered at a recycling facility by simple sorting and crushing processes. By raising environmental awareness, more diverse and effective collection systems could be established for consumers to easily dispose of EOL batteries in many places. Producers, retailers and distributors in South Korea should also play an important role in the collection of EOL batteries from consumers. Lithium-ion batteries from many electronic devices must be included in the EPR system for resource recovery.

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Oxidation and biotoxicity assessment of microcystin-LR using different AOPs based on UV, O3 and H2O2
Siyi Lu, Naiyu Wang, Can Wang
Front. Environ. Sci. Eng.    2018, 12 (3): 12.   https://doi.org/10.1007/s11783-018-1030-2
Abstract   HTML   PDF (344KB)

MC-LR removal performances under different AOPs were compared systematically.

Higher removal efficiency and synergistic effects were obtained by combined process.

The acute biotoxicity raised in different degrees after oxidation.

Microcystin-LR attracts attention due to its high toxicity, high concentration and high frequency. The removal characteristics of UV/H2O2 and O3/H2O2 advanced oxidation processes and their individual process for MC-LR were investigated and compared in this study. Both the removal efficiencies and rates of MC-LR as well as the biotoxicity of degradation products was analyzed. Results showed that the UV/H2O2 process and O3/H2O2 were effective methods to remove MC-LR from water, and they two performed better than UV-, O3-, H2O2-alone processes under the same conditions. The effects of UV intensity, H2O2 concentration and O3 concentration on the removal performance were explored. The synergistic effects between UV and H2O2, O3 and H2O2 were observed. UV dosage of 1800 mJ·cm2 was required to remove 90% of 100 mg·L1 MC-LR, which amount significantly decreased to 500 mJ·cm2 when 1.7 mg·L1 H2O2 was added. 0.25 mg·L1 O3, or 0.125 mg·L1 O3 with 1.7 mg·L1 H2O2 was needed to reach 90% removal efficiency. Furthermore, the biotoxicity results about these UV/H2O2, O3/H2O2 and O3-alone processes all present rising trends with oxidation degree of MC-LR. Biotoxicity of solution, equivalent to 0.01 mg·L1 Zn2+, raised to 0.05 mg·L1 Zn2+ after UV/H2O2 or O3/H2O2 reaction. This phenomenon may be attributed to the aldehydes and ketones with small molecular weight generated during reaction. Advice about the selection of MC-LR removal methods in real cases was provided.

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Current state and future perspectives of sewer networks in urban China
Dong Huang, Xiuhong Liu, Songzhu Jiang, Hongchen Wang, Junyan Wang, Yuankai Zhang
Front. Environ. Sci. Eng.    2018, 12 (3): 2.   https://doi.org/10.1007/s11783-018-1023-1
Abstract   HTML   PDF (635KB)

Sewer network construction is insufficient in China currently.

The management for sewer network is very disordered in China.

Maintenance is far from enough for current sewer networks in China.

China’s top priority for sewer networks is to elevate its overall performance.

The new technical route is an optimal option for sewer maintenance in China.

Chinese authorities and the public have largely ignored sewer networks; however, various problems are emerging nationwide with the increase construction of new sewers. The current state of sewer network construction, administration, and maintenance in China is comprehensively reviewed in this study. Serving about 444 million people, 511,200 km of sewer lines are located in urban areas. In 2014, $7 billion was invested in sewer network construction. However, both the sewer pervasion rate and the per capita sewer length were significantly lower than those in developed countries. Sewer administrative agencies in local governments are uncoordinated. Laws, regulations, and standards are incomplete, and some practices are unscientific. The future situation of sewer maintenance is extremely grim because sewer corrosion control measures have not been launched. Moreover, inspection and rehabilitation chiefly rely on traditional approaches. In contrast, the overall market share of innovative technologies is very low owing to high cost, funds shortage, and technical limitations. Approaches such as liner inversion cured-in-place pipe, pull-in ultraviolet light cured liners, and spiral wound lining are applied mostly in economically developed regions. According to status and problem analyses, China’s top priority will be to conduct aggressive maintenance work in sewer networks in the future. New technical route, corrosion control - periodic visualized inspection - trenchless rehabilitation, could be the best option for future sewer maintenance in China. Instructions and opportunities for applying this technical route are discussed in detail in this study. Finally, additional factors in the development of sewer networks in China are suggested.

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Biogas and its opportunities—A review
Panagiotis G. Kougias, Irini Angelidaki
Front. Environ. Sci. Eng.    2018, 12 (3): 14.   https://doi.org/10.1007/s11783-018-1037-8
Abstract   HTML   PDF (331KB)

A comprehensive description of the biogas process is presented.

Main operational parameters influencing the biogas process are reviewed.

A historical overview of the biogas development is extensively presented.

The current status of anaerobic digestion for biogas production is discussed.

New horizons for exploitation and utilisation of biogas are proposed.

Biogas production is a well-established technology primarily for the generation of renewable energy and also for the valorization of organic residues. Biogas is the end product of a biological mediated process, the so called anaerobic digestion, in which different microorganisms, follow diverse metabolic pathways to decompose the organic matter. The process has been known since ancient times and was widely applied at domestic households providing heat and power for hundreds of years. Nowadays, the biogas sector is rapidly growing and novel achievements create the foundation for constituting biogas plants as advanced bioenergy factories. In this context, the biogas plants are the basis of a circular economy concept targeting nutrients recycling, reduction of greenhouse gas emissions and biorefinery purposes. This review summarizes the current state-of-the-art and presents future perspectives related to the anaerobic digestion process for biogas production. Moreover, a historical retrospective of biogas sector from the early years of its development till its recent advancements gives an outlook of the opportunities that are opening up for process optimisation.

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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
Abstract   HTML   PDF (1520KB)

• 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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Review on design and evaluation of environmental photocatalysts
Xin Li, Jun Xie, Chuanjia Jiang, Jiaguo Yu, Pengyi Zhang
Front. Environ. Sci. Eng.    2018, 12 (5): 14.   https://doi.org/10.1007/s11783-018-1076-1
Abstract   HTML   PDF (8528KB)

Fundamentals on the photocatalytic degradation were systematically summarized.

Charge carrier dynamics for the photocatalytic degradation were reviewed.

Adsorption and photodegradation kinetics of reactants were highlighted.

The mechanism aspects, including O2 reduction, reactive oxidation species and key intermediates were also addressed.

Selectivity and stability of semiconductors for photodegradation were clarified.

Heterogeneous photocatalysis has long been considered to be one of the most promising approaches to tackling the myriad environmental issues. However, there are still many challenges for designing efficient and cost-effective photocatalysts and photocatalytic degradation systems for application in practical environmental remediation. In this review, we first systematically introduced the fundamental principles on the photocatalytic pollutant degradation. Then, the important considerations in the design of photocatalytic degradation systems are carefully addressed, including charge carrier dynamics, catalytic selectivity, photocatalyst stability, pollutant adsorption and photodegradation kinetics. Especially, the underlying mechanisms are thoroughly reviewed, including investigation of oxygen reduction properties and identification of reactive oxygen species and key intermediates. This review in environmental photocatalysis may inspire exciting new directions and methods for designing, fabricating and evaluating photocatalytic degradation systems for better environmental remediation and possibly other relevant fields, such as photocatalytic disinfection, water oxidation, and selective organic transformations.

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Cited: Crossref(33) WebOfScience(68)
Effects of eggshell addition on calcium-deficient acid soils contaminated with heavy metals
Weiqi Luo, Yanping Ji, Lu Qu, Zhi Dang, Yingying Xie, Chengfang Yang, Xueqin Tao, Jianmin Zhou, Guining Lu
Front. Environ. Sci. Eng.    2018, 12 (3): 4.   https://doi.org/10.1007/s11783-018-1026-y
Abstract   HTML   PDF (467KB)

The eggshell was used to remediate the contaminated soil by heavy metals.

The eggshell addition decreased the available state of the heavy metals.

The available calcium in the soil increased due to eggshell addition.

The efficiency was investigated in different moisture conditions.

In this study, effects of water conditions (flooded, wet, or dry) and eggshell dosages (0, 0.1, 1.0, and 10.0 g/kg soil, respectively) on pH variation, content of unavailable state of heavy metals, form of heavy metals, and available nutritious element calcium (Ca) in acid soils contaminated with heavy metals were investigated, respectively. The soil samples were continuously cultivated indoors and analyzed by toxicity characteristic leaching procedure and community bureau of reference (BCR) sequential extraction procedure. The results showed that the addition of eggshell could effectively improve the pH of acid soil and increase it to neutral level. Moreover, the contents of unavailable state of heavy metals Cu, Zn, and Cd increased significantly. Furthermore, when the soil was cultivated under the flooded condition with 1.0 g/kg eggshell, the unavailable state of Cu, Zn, and Cd increased the most, and these heavy metals were transformed into residual state. On the other hand, the amount of available state of Ca increased to 432.19 from 73.34 mg/kg with the addition of 1.0 g/kg eggshell, which indicated that the addition of eggshell dramatically improved the available state of Ca. Therefore, eggshell could ameliorate the soil environment as it led to the decrease of available heavy metals and improvement of fertilization effectively. In a word, this study indicates that the addition of eggshell would be a new potential method for remediation of acid field soils contaminated with heavy metals.

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Designing an in situ remediation strategy for polluted surface water bodies through the specific regulation of microbial community
Boran Wu, Xiaoli Chai, Youcai Zhao, Xiaohu Dai
Front. Environ. Sci. Eng.    2019, 13 (1): 4.   https://doi.org/10.1007/s11783-019-1088-5
Abstract   HTML   PDF (236KB)

Remediation of polluted water body via microbial community regulation is proposed.

EAS-induced microbial growth can enhance self-purification of polluted water body.

Principle of EAS is elaborated by the conceptual model description.

This paper proposes an in situ restoration strategy, ecosystem activation system (EAS), for self-purification abilities of polluted water ecosystems through the specific regulation of microbial community. EAS utilizes polyhydroxyalkanoates (PHA) to modify indigenous microbial communities of polluted water bodies. Microorganisms preferentially utilizing PHA as the carbon source for their enhanced growth are defined as specific, and those with no special selectivity to PHA and raw-water dissolved organic matter are defined as non-specific and can be phased out during EAS operation. As a result, the microbial community can be regulated to the specific structure, which is beneficial for the water quality improvement. The developed model described the above principle with accounting for the growth kinetics of specific microorganisms, competitive inhabitation of specific microorganisms on non-specific microorganisms, and coupled EAS-induced self-purification of polluted water bodies. The conceptual model is believed to be a primary step toward quantitative design, operation, and optimization of EAS.

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A review on application of dielectric barrier discharge plasma technology on the abatement of volatile organic compounds
Wenjing Lu, Yawar Abbas, Muhammad Farooq Mustafa, Chao Pan, Hongtao Wang
Front. Environ. Sci. Eng.    2019, 13 (2): 30.   https://doi.org/10.1007/s11783-019-1108-5
Abstract   HTML   PDF (565KB)

• Applications of non-thermal plasma reactors for reduction of VOCs were reviewed.

• Dielectric barrier discharge (DBD) plasma was considered.

• Effect of process parameters was studied.

• Effect of catalysts and inhibitors were evaluated.

Volatile organic compounds (VOCs) released from the waste treatment facilities have become a significant issue because they are not only causing odor nuisance but may also hazard to human health. Non-thermal plasma (NTP) technologies are newly developed methods and became a research trend in recent years regarding the removal of VOCs from the air environment. Due to its unique characteristics, such as bulk homogenized volume, plasma with high reaction efficiency dielectric barrier discharge (DBD) technology is considered one of the most promising techniques of NTP. This paper reviews recent progress of DBD plasma technology for abatement of VOCs. The principle of plasma generation in DBD and its configurations (electrode, discharge gap, dielectric barrier material, etc.) are discussed in details. Based on previously published literature, attention has been paid on the effect of DBD configuration on the removal of VOCs. The removal efficiency of VOCs in DBD reactors is presented too, considering various process parameters such as initial concentration, gas feeding rate, oxygen content and input power. Moreover, using DBD technology, the role of catalysis and inhibitors in VOCs removal are discussed. Finally, a modified configuration of the DBD reactor, i.e. double dielectric barrier discharge (DDBD) for the abatement of VOCs is discussed in details. It was suggested that the DDBD plasma reactor could be used for higher conversion efficiency as well as for avoiding solid residue deposition on the electrode. These depositions can interfere with the performance of the reactor.

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Anaerobic ammonia oxidizing bacteria: ecological distribution, metabolism, and microbial interactions
Dawen Gao, Xiaolong Wang, Hong Liang, Qihang Wei, Yuan Dou, Longwei Li
Front. Environ. Sci. Eng.    2018, 12 (3): 10.   https://doi.org/10.1007/s11783-018-1035-x
Abstract   HTML   PDF (251KB)

The unique characteristics of anammox bacteria were reviewed.

Ecological distribution and nitrogen loss contributions were well documented.

Ecological interactions between anammox bacteria and other organisms were discussed.

Anammox (ANaerobic AMMonia OXidation) is a newly discovered pathway in the nitrogen cycle. This discovery has increased our knowledge of the global nitrogen cycle and triggered intense interest for anammox-based applications. Anammox bacteria are almost ubiquitous in the suboxic zones of almost all types of natural ecosystems and contribute significant to the global total nitrogen loss. In this paper, their ecological distributions and contributions to the nitrogen loss in marine, wetland, terrestrial ecosystems, and even extreme environments were reviewed. The unique metabolic mechanism of anammox bacteria was well described, including the particular cellular structures and genome compositions, which indicate the special evolutionary status of anammox bacteria. Finally, the ecological interactions among anammox bacteria and other organisms were discussed based on substrate availability and spatial organizations. This review attempts to summarize the fundamental understanding of anammox, provide an up-to-date summary of the knowledge of the overall anammox status, and propose future prospects for anammox. Based on novel findings, the metagenome has become a powerful tool for the genomic analysis of communities containing anammox bacteria; the metabolic diversity and biogeochemistry in the global nitrogen budget require more comprehensive studies.

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Photolysis and photooxidation of typical gaseous VOCs by UV Irradiation: Removal performance and mechanisms
In-Sun Kang, Jinying Xi, Hong-Ying Hu
Front. Environ. Sci. Eng.    2018, 12 (3): 8.   https://doi.org/10.1007/s11783-018-1032-0
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UV photodegradation of 27 typical VOCs was systematically investigated.

Contribution of photolysis and photooxidation to VOCs removal was identified.

Gaseous VOC could be partially converted to particles by 185/254 nm UV irradiation.

The mineralization and conversion of 27 VOCs by UV irradiation were reported.

Photodegradation by ultraviolet irradiation (UV) is increasingly applied in volatile organic compound (VOC) and odor gas treatments. In this study, 27 typical VOCs, including 11 hydrocarbons and 16 hydrocarbon derivatives, at 150–200 ppm in air and nitrogen gas were treated by a laboratory-scale UV reactor with 185/254 nm irradiation to systematically investigate their removal and conversion by UV irradiation. For the tested 27 VOCs, the VOC removal efficiencies in air were within the range of 13%–97% (with an average of 80%) at a retention time of 53 s, which showed a moderate positive correlation with the molecular weight of the VOCs (R = 0.53). The respective contributions of photolysis and photooxidation to VOC removal were identified for each VOC. According to the CO2 results, the mineralization rate of the tested VOCs was within the range of 9%–90%, with an average of 41% and were negatively correlated to the molecular weight (R = -0.63). Many of the tested VOCs exhibited high concentration particulate matters in the off-gases with a 3–283 mg/m3 PM10 range and a 2–40 mg/m3 PM2.5 range. The carbon balance of each VOC during UV irradiation was analyzed based on the VOC, CO2 and PM10 concentrations. Certain organic intermediates and 23–218 ppm ozone were also identified in the off-gases. Although the UV technique exhibited a high VOC removal efficiency, its drawbacks, specifically low mineralization, particulate matters production, and ozone emission, must be considered prior to its application in VOC gas treatments.

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Effect of chemical dose on phosphorus removal and membrane fouling control in a UCT-MBR
Guangrong Sun, Chuanyi Zhang, Wei Li, Limei Yuan, Shilong He, Liping Wang
Front. Environ. Sci. Eng.    2019, 13 (1): 1.   https://doi.org/10.1007/s11783-019-1085-8
Abstract   HTML   PDF (1281KB)

Phosphorus removal was enhanced effectively by dosing aluminum sulfate and effluent phosphorus concentration was lower than 0.5 mg/L.

Sludge activity was not inhibited but improved slightly with addition of aluminum sulfate.

EPS concentrations both in mixed liquid and on membrane surface were decreased, contributing to the effective mitigation of membrane fouling.

To enhance phosphorus removal and make the effluent meet the strict discharge level of total phosphorus (TP, 0.5 mg/L), flocculant dosing is frequently applied. In this study, the performance of aluminum sulfate dosing in a University of Cape Town Membrane Bioreactor (UCT-MBR) was investigated, in terms of the nutrients removal performance, sludge characteristics and membrane fouling. The results indicated that the addition of aluminum sulfate into the aerobic reactor continuously had significantly enhanced phosphorus removal. Moreover, COD, NH4+-N and TN removal were not affected and effluent all met the first level A criteria of GB18918-2002. In addition, the addition of aluminum sulfate had improved the sludge activity slightly and reduced trans-membrane pressure (TMP) increase rate from 1.13 KPa/d to 0.57 KPa/d effectively. The membrane fouling was alleviated attributed to the increased average particle sizes and the decreased accumulation of the small sludge particles on membrane surface. Furthermore, the decline of extracellular polymeric substance (EPS) concentration in mixed sludge liquid decreased its accumulation on membrane surface, resulting in the mitigation of membrane fouling directly.

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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
Abstract   HTML   PDF (1062KB)

• 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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Relations between indoor and outdoor PM2.5 and constituent concentrations
Cong Liu, Yinping Zhang
Front. Environ. Sci. Eng.    2019, 13 (1): 5.   https://doi.org/10.1007/s11783-019-1089-4
Abstract   HTML   PDF (762KB)

Factors impacting indoor-outdoor relations are introduced.

Sulfate seems a fine tracer for other non-volatile species.

Particulate nitrate and ammonium desorb during outdoor-to-indoor transport.

OC load increases during the transport due to sorption of indoor SVOCs.

Outdoor PM2.5 influences both the concentration and composition of indoor PM2.5. People spend over 80% of their time indoors. Therefore, to assess possible health effects of PM2.5 it is important to accurately characterize indoor PM2.5 concentrations and composition. Controlling indoor PM2.5 concentration is presently more feasible and economic than decreasing outdoor PM2.5 concentration. This study reviews modeling and measurements that address relationships between indoor and outdoor PM2.5 and the corresponding constituent concentrations. The key factors in the models are indoor-outdoor air exchange rate, particle penetration, and deposition. We compiled studies that report I/O ratios of PM2.5 and typical constituents (sulfate (SO42-), nitrate (NO3-), ammonium (NH4+), elemental carbon (EC), and organic carbon (OC), iron (Fe), copper (Cu), and manganese (Mn)). From these studies we conclude that: 1) sulfate might be a reasonable tracer of non-volatile species (EC, Fe, Cu, and Mn) and PM2.5 itself; 2) particulate nitrate and ammonium generally desorb to gaseous HNO3 and NH3 when they enter indoors, unless, as seldom happens, they have strong indoor sources; 3) indoor-originating semi-volatile organic compounds sorb on indoor PM2.5, thereby increasing the PM2.5 OC load. We suggest further studies on indoor-outdoor relationships of PM2.5 and constituents so as to help develop standards for healthy buildings.

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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
Abstract   HTML   PDF (1081KB)

• 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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Molecular analysis of bacterial community in the tap water with different water ages of a drinking water distribution system
Feng Wang, Weiying Li, Yue Li, Junpeng Zhang, Jiping Chen, Wei Zhang, Xuan Wu
Front. Environ. Sci. Eng.    2018, 12 (3): 6.   https://doi.org/10.1007/s11783-018-1020-4
Abstract   HTML   PDF (1194KB)

The increase of water ages drove the deterioration of drinking water quality.

The relative abundance of Rhizobiales uniquely increase during distributing process.

Rhizobiales order was helpful for inhibiting corrosion under high chlorine level.

New disinfecting strategies should be developed to ensure drinking water safety.

Bacterial community in the drinking water distribution system (DWDS) was regulated by multiple environmental factors, many of which varied as a function of water age. In this study, four water samples with different water ages, including finished water (FW, 0 d) and tap water (TW) [TW1 (1 d), TW2(2 d) and TW3(3 d)], were collected along with the mains of a practical DWDS, and the bacterial community was investigated by high-throughput sequencing technique. Results indicated that the residual chlorine declined with the increase of water age, accompanied by the increase of dissolved organic matter, total bacteria counts and bacterial diversity (Shannon). For bacterial community composition, although Proteobacteria phylum (84.12%-97.6%) and Alphaproteobacteria class (67.42%-93.09%) kept dominate, an evident regular was observed at the order level. In detail, the relative abundance of most of other residual orders increased with different degrees from the start to the end of the DWDS, while a downward trend was uniquely observed in terms of Rhizobiales, who was inferred to be chlorine-resistant and be helpful for inhibiting pipes corrosion. Moreover, some OTUs were found to be closely related with species possessing pathogenicity and chlorine-resistant ability, so it was recommended that the use of agents other than chlorine or agents that can act synergically with chlorine should be developed for drinking water disinfection. This paper revealed bacterial community variations along the mains of the DWDS and the result was helpful for understanding bacterial ecology in the DWDS.

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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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Acidogenic sludge fermentation to recover soluble organics as the carbon source for denitrification in wastewater treatment: Comparison of sludge types Collection
Lin Lin, Ying-yu Li, Xiao-yan Li
Front. Environ. Sci. Eng.    2018, 12 (4): 3.   https://doi.org/10.1007/s11783-018-1043-x
Abstract   HTML   PDF (320KB)

CEPS sludge was compared with conventional primary and secondary sludge for the VFAs yield.

Fe-based CEPS sludge exhibited the highest efficiency of organic recovery.

Fermented CEPS sludge liquor provided a sufficient carbon source for denitrification.

99% of nitrate removal was achieved based on the Fe-CEPS and sludge fermentation.

For biological nitrogen (N) removal from wastewater, a sufficient organic carbon source is requested for denitrification. However, the organic carbon/nitrogen ratio in municipal wastewater is becoming lower in recent years, which increases the demand for the addition of external organic carbon, e.g. methanol, in wastewater treatment. The volatile fatty acids (VFAs) produced by acidogenic fermentation of sewage sludge can be an attractive alternative for methanol. Chemically enhanced primary sedimentation (CEPS) is an effective process that applies chemical coagulants to enhance the removal of organic pollutants and phosphorus from wastewater by sedimentation. In terms of the chemical and biological characteristics, the CEPS sludge is considerably different from the conventional primary and secondary sludge. In the present study, FeCl3 and PACl (polyaluminum chloride) were used as the coagulants for CEPS treatment of raw sewage. The derived CEPS sludge (Fe-sludge and Al-sludge) was then processed with mesophilic acidogenic fermentation to hydrolyse the solid organics and produce VFAs for organic carbon recovery, and the sludge acidogenesis efficiency was compared with that of the conventional primary sludge and secondary sludge. The results showed that the Fe-sludge exhibited the highest hydrolysis and acidogenesis efficiency, while the Al-sludge and secondary sludge had lower hydrolysis efficiency than that of primary sludge. Utilizing the Fe-sludge fermentation liquid as the carbon source for denitrification, more than 99% of nitrate removal was achieved in the main-stream wastewater treatment without any external carbon addition, instead of 35% obtained from the conventional process of primary sedimentation followed by the oxic/anoxic (O/A) treatment.

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Simultaneous removal of hydrogen sulfide and volatile organic sulfur compounds in off-gas mixture from a wastewater treatment plant using a two-stage bio-trickling filter system
Shihao Sun, Tipei Jia, Kaiqi Chen, Yongzhen Peng, Liang Zhang
Front. Environ. Sci. Eng.    2019, 13 (4): 60.   https://doi.org/10.1007/s11783-019-1148-x
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A two-stage BTF system was established treating odorous off-gas mixture from a WWTP.

The two-stage BTF system showed resistance for the lifting load of H2S and VOSC.

Miseq Illumina sequencing showed separated functional microbial community in BTFs.

Avoiding H2S inhibition and enhancement of VOSC degradation was achieved.

Key control point was discussed to help industrial application of the system.

Simultaneous removal of hydrogen sulfide (H2S) and volatile organic sulfur compounds (VOSCs) in off-gas mixture from a wastewater treatment plant (WWTP) is difficult due to the occasional inhibitory effects of H2S on VOSC degradation. In this study, a two-stage bio-trickling filter (BTF) system was developed to treat off-gas mixture from a real WWTP facility. At an empty bed retention time of 40 s, removal efficiencies of H2S, methanethiol, dimethyl sulfide, and dimethyl disulfide were 90.1, 88.4, 85.8, and 61.8%, respectively. Furthermore, the effect of lifting load shock on system performance was investigated and results indicated that removal of both H2S and VOSCs was slightly affected. Illumina Miseq sequencing revealed that the microbial community of first-stage BTF contained high abundance of H2S-affinity genera including Acidithiobacillus (51.43%), Metallibacterium (25.35%), and Thionomas (8.08%). Analysis of mechanism demonstrated that first stage of BTF removed 86.1% of H2S, mitigating the suppression on VOSC degradation in second stage of BTF. Overall, the two-stage BTF system, an innovative bioprocess, can simultaneously remove H2S and VOSC.

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Enhanced methane recovery and exoelectrogen-methanogen evolution from low-strength wastewater in an up-flow biofilm reactor with conductive granular graphite fillers Collection
Zechong Guo, Lei Gao, Ling Wang, Wenzong Liu, Aijie Wang
Front. Environ. Sci. Eng.    2018, 12 (4): 13.   https://doi.org/10.1007/s11783-018-1074-3
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Methane yield increased 22 times from low-strength wastewater by applying conductive fillers.

Conductive fillers accelerated the start-up stage of anaerobic biofilm reactor.

Conductive fillers altered methanogens structure.

Methane production from low-strength wastewater (LSWW) is generally difficult because of the low metabolism rate of methanogens. Here, an up-flow biofilm reactor equipped with conductive granular graphite (GG) as fillers was developed to enhance direct interspecies electron transfer (DIET) between syntrophic electroactive bacteria and methanogens to stimulate methanogenesis process. Compared to quartz sand fillers, using conductive fillers significantly enhanced methane production and accelerated the start-up stage of biofilm reactor. At HRT of 6 h, the average methane production rate and methane yield of reactor with GG were 0.106 m3/(m3.d) and 74.5 L/kg COD, which increased by 34.3 times and 22.4 times respectively compared with the reactor with common quartz sand fillers. The microbial community analysis revealed that methanogens structure was significantly altered and the archaea that are involved in DIET (such as Methanobacterium) were enriched in GG filler. The beneficial effects of conductive fillers on methane production implied a practical strategy for efficient methane recovery from LSWW.

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Effect of biological activated carbon filter depth and backwashing process on transformation of biofilm community
Wanqi Qi, Weiying Li, Junpeng Zhang, Xuan Wu, Jie Zhang, Wei Zhang
Front. Environ. Sci. Eng.    2019, 13 (1): 15.   https://doi.org/10.1007/s11783-019-1100-0
Abstract   HTML   PDF (1803KB)

We studied BAC biofilm during the process of initial operation and backwash.

Microbial diversity decreased gradually with the increase of BAC filter depth.

Proteobacteria dominated at the phylum level among the BAC biofilm samples.

α-proteobacteria increased about 10% in all carbon filter depth after backwash.

The biological activated carbon (BAC) is a popular advanced water treatment to the provision of safe water supply. A bench-scale device was designed to gain a better insight into microbial diversity and community structure of BAC biofilm by using high-throughput sequencing method. Both samples of BAC biofilm (the first, third and fifth month) and water (inlet water and outlet water of carbon filter, outlet water of backwashing) were analyzed to evaluate the impact of carbon filter depth, running time and backwash process. The results showed that the microbial diversity of biofilm decreased generally with the increase of carbon filter depth and biofilm reached a steady-state at the top layer of BAC after three months’ running. Proteobacteria (71.02%–95.61%) was found to be dominant bacteria both in biofilms and water samples. As one of opportunistic pathogen, the Pseudomonas aeruginosa in the outlet water of device (1.20%) was about eight times higher than that in the inlet water of device (0.16%) at the genus level after five-month operation. To maintain the safety of drinking water, the backwash used in this test could significantly remove Sphingobacteria (from 8.69% to 5.09%, p<0.05) of carbon biofilm. After backwashing, the operational taxonomic units (OTUs) number and the Shannon index decreased significantly (p<0.05) at the bottom of carbon column and we found the Proteobacteria increased by about 10% in all biofilm samples from different filter depth. This study reveals the transformation of BAC biofilm with the impact of running time and backwashing.

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Impacts of advanced treatment processes on elimination of antibiotic resistance genes in a municipal wastewater treatment plant Collection
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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Microbial responses to combined oxidation and catalysis treatment of 1,4-dioxane and co-contaminants in groundwater and soil Collection
Yu Miao, Nicholas W. Johnson, Kimberly Heck, Sujin Guo, Camilah D. Powell, Thien Phan, Phillip B. Gedalanga, David T. Adamson, Charles J. Newell, Michael S. Wong, Shaily Mahendra
Front. Environ. Sci. Eng.    2018, 12 (5): 2.   https://doi.org/10.1007/s11783-018-1071-6
Abstract   HTML   PDF (1984KB)

Groundwater microbial community was altered after catalysis and chemical oxidation.

The coupled treatment train removed 90% 1,4-dioxane regardless of co-contaminants.

Dynamics of microbial populations varied along with different treatment stages.

Many microbial taxa exhibited resilience against oxidative and catalytic treatments.

Metagenomic analysis will be valuable for long-term management of polluted sites.

Post-treatment impacts of a novel combined hydrogen peroxide (H2O2) oxidation and WOx/ZrO2 catalysis used for the removal of 1,4-dioxane and chlorinated volatile organic compound (CVOC) contaminants were investigated in soil and groundwater microbial community. This treatment train removed ~90% 1,4-dioxane regardless of initial concentrations of 1,4-dioxane and CVOCs. The Illumina Miseq platform and bioinformatics were used to study the changes to microbial community structure. This approach determined that dynamic shifts of microbiomes were associated with conditions specific to treatments as well as 1,4-dioxane and CVOCs mixtures. The biodiversity was observed to decrease only after oxidation under conditions that included high levels of 1,4-dioxane and CVOCs, but increased when 1,4-dioxane was present without CVOCs. WOx/ZrO2 catalysis reduced biodiversity across all conditions. Taxonomic classification demonstrated oxidative tolerance for members of the genera Massilia and Rhodococcus, while catalyst tolerance was observed for members of the genera Sphingomonas and Devosia. Linear discriminant analysis effect size was a useful statistical tool to highlight representative microbes, while the multidimensional analysis elucidated the separation of microbiomes under the low 1,4-dioxane-only condition from all other conditions containing CVOCs, as well as the differences of microbial population among original, post-oxidation, and post-catalysis states. The results of this study enhance our understanding of microbial community responses to a promising chemical treatment train, and the metagenomic analysis will help practitioners predict the microbial community status during the post-treatment period, which may have consequences for long-term management strategies that include additional biodegradation treatment or natural attenuation.

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G-CNTs/PVDF mixed matrix membranes with improved antifouling properties and filtration performance Collection
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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Influence of hydraulic retention time on behavior of antibiotics and antibiotic resistance genes in aerobic granular reactor treating biogas slurry Collection
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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Elimination of antibiotic resistance genes and control of horizontal transfer risk by UV-based treatment of drinking water: A mini review Collection
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
Abstract   HTML   PDF (2273KB)

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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Enhanced heterogeneous Fenton-like activity by Cu-doped BiFeO3 perovskite for degradation of organic pollutants
Jie Mao, Xie Quan, Jing Wang, Cong Gao, Shuo Chen, Hongtao Yu, Yaobin Zhang
Front. Environ. Sci. Eng.    2018, 12 (6): 10.   https://doi.org/10.1007/s11783-018-1060-9
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OH played a key role in heterogeneous Fenton-like catalytic oxidation of organic pollutants.

Doping Cu into BiFeO3 promoted the generation of Fe2+ and then facilitated the effective formation of •OH.

Cu-doped BiFeO3 exhibited higher catalytic performance for phenol degradation than non-doped BiFeO3.

Heterogeneous Fenton-like reaction has been extensively investigated to eliminate refractory organic contaminants in wastewater, but it usually shows low catalytic performance due to difficulty in reduction from Fe(III) to Fe(II). In this study, enhanced catalytic efficiency was obtained by employing Cu-doped BiFeO3 as heterogeneous Fenton-like catalysts, which exhibited higher catalytic performance toward the activation of H2O2 for phenol degradation than un-doped BiFeO3. BiFe0.8Cu0.2O3 displayed the best performance, which yielded 91% removal of phenol (10 mg L1) in 120 min. The pseudo first-order kinetic rate constant of phenol degradation in BiFe0.8Cu0.2O3 catalyzed heterogeneous Fenton-like reaction was 5 times higher than those of traditional heterogeneous Fenton-like catalysts, such as Fe3O4 and goethite. The phenol degradation efficiency could still reach 83% after 4 cycles, which implied the good stability of BiFe0.8Cu0.2O3. The high catalytic activity of BiFe0.8Cu0.2O3 was attributed to the fact that the doping Cu into BiFeO3 could promote the generation of Fe(II) in the catalyst and then facilitate the activation of H2O2 to degrade the organic pollutants.

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Advances in Fe(III) bioreduction and its application prospect for groundwater remediation: A review Collection
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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Transferral of HMs pollution from road-deposited sediments to stormwater runoff during transport processes
Qian Wang, Qionghua Zhang, Mawuli Dzakpasu, Nini Chang, Xiaochang Wang
Front. Environ. Sci. Eng.    2019, 13 (1): 13.   https://doi.org/10.1007/s11783-019-1091-x
Abstract   HTML   PDF (438KB)

Ratio of turbidity and TSS (Tur/TSS) was used to characterize PSD of stormwater particles.

Pb and Zn preferred to accumulate in finer RDS, while Cu, Cr and Ni in coarser RDS.

HMs pollution in stormwater particles increased linearly with Tur/TSS.

Dissolvability of HMs and PSD variations contribute to the differences between RDS and stormwater.

Stormwater runoff, derived from the wash-off of road-deposited sediments (RDS), contains elevated heavy metal (HM) concentrations and, thus, imposes an increasing threat to urban aquatic ecosystems. In-depth understanding of the variations of HMs pollution from RDS to stormwater during transport processes facilitates the development of effective RDS and stormwater control strategies. Toward this end, the distribution of HMs (Cu, Pb, Zn, Cr, and Ni) in RDS and stormwater were investigated simultaneously. The results show a preferential accumulation of Pb and Zn in the finer (<38.5 μm) RDS, and Cu, Cr and Ni in the coarser (38.5–150 μm) RDS. For stormwater, n.d.~48.6% of HMs fractionated into the dissolved phase, and stormwater particles constitute the primary carriers of HMs. Furthermore, the accumulation of HMs in stormwater particles increased linearly with finer particle size distributions (PSD). Geoaccumulation index (Igeo) highlighted the predominant pollution of both RDS and stormwater particles by Cu, Pb and Zn. Nonetheless, Cu, Pb, and Ni mostly contributed the potential ecological risk of RDS, whereas Cu, Pb, and Zn mainly contributed that of stormwater particles. Moreover, contamination by Cu, Pb and Zn was significantly higher in stormwater particles than that in RDS. These differences are attributable to the solubility and size-dependent accumulation of HMs in RDS, as well as the PSD variations during transport processes. The study outcomes highlight the importance of very fine (nano- and submicron- scale) RDS in stormwater pollution and the necessity of control.

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