Chinese Academy of Sciences, China

Aijie Wang, Professor of Research Center for Eco-Environmental Sciences (RCEES), Chinese Academy of Sciences (CAS), P.R. China ...

... She is the Deputy Director of National Engineering Laboratory for Industrial Wastewater Treatment, and Head of Key Laboratory for Environmental Biotechnology, CAS. She was awarded as Distinguished Professor of Yangtze River Scholar by Ministry of Education in 2011. She received the National Outstanding Youth Science Fund Award in 2012, the Youth Science and Technology Innovation Talent Award in 2013 and the Ten-Thousand People Program: Leading Talent Award in 2016. In 2015, she was awarded as a member of the IWA Fellows. Her research interests cover water pollution control and resource recovery, which includes bio-based technology for heavily polluted industrial wastewater treatment, polluted aquatic environment bioremediation, and resources/bioenergy recovery from waste (water)/biosolids. A well-recognized feature of her research is the effective integration of fundamental (interdisciplinary) and practically applicable research. Her work on anaerobic acidogensis of recalcitrant organic compounds based on the concept of biological phase separation have been proved to bring substantial benefits to the Chinese industries (e.g. Pharmaceutical Industry, Chemical Engineering Industry), which suffer from heavy pollution long. Her latest research includes the electrochemically assisted anaerobic wastewater treatment that could significantly accelerate the reductive detoxification, decolorization and dehalogenation of refractory pollutants, as well as facilitate their deep removal from wastewater. This technology has been indicated by various application cases and got wide interests around industry.

 

Abstract


Physicochemical and biological coupled process as an efficient way for enhanced degradation of antibiotic contaminants

Ai-Jie Wang1,2, *, Yang-Cheng Ding1, Bin Liang1, Wen-Li Jiang1

1Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China

2State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090, China

*Corresponding author. E-mail addresses: This email address is being protected from spambots. You need JavaScript enabled to view it., This email address is being protected from spambots. You need JavaScript enabled to view it. (A. Wang).

There are anaerobic reducing reactions of microorganisms that can detoxify pollutants, such as dehalogenation and denitirification. In these reducing reactions, it has been shown that the microorganisms can utilize the external electrons directly received from the electron mediators, such as humic substances, present in soils and sediments. Humic substances are classified into three categories, based on the solubility into aqueous solutions at different pH: fulvic acids (soluble at any pH), humic acids (soluble at alkaline pH), and humin (insoluble at any pH). We found that anaerobic dehaloganating reactions of microorganisms were supported by solid-phase humin, but not by humic acids. Thus, in this study, we have characterized solid-phase humin polyphasically as the external electron mediator for microbial reduction.

Humin was extracted from various soils and sediments as reported previously (Zhang and Katayama, 2012). The freeze dried humin powder were subjected to the physical, chemical, and microbial characterizations (Zhang et al 2015), as well as electrical analyses.

Global-scale pollution of various environmental settings with diverse antibiotics and antibiotic resistance genes (ARGs) has attracted considerable attention (Van Boeckel et al., 2015; Zhang et al., 2015; Zhu et al., 2017). The deep elimination of emerging antibiotic contaminants with high-efficiency and low-cost ways towards different water environments is one of the important goals and scientific frontiers in ensuring the global water security (Eggen et al., 2014; Larsen et al., 2016; Pruden 2014). The microbial-dominated biotechnology has the advantages of environmental friendliness, and low operating costs, and it is a commonly used technology all over the world (van Loosdrecht and Brdjanovic 2014). However, biological treatment systems have been confined by their low detoxification/transformation efficiency and instability for these toxic emerging contaminants (Gonzalez-Gil et al., 2016; Tran et al., 2016). On the other hand, biological treatment is not only referred to the degradation/attenuation process of antibiotic contaminants, but also associated with the ARGs transmission, evolution, and dynamic changes (Aydin et al., 2015; Varela et al., 2014). Therefore, it is urgent to develop novel (pre)treatment technologies before and after biological treatment unit.

Livestock or antibiotic producing wastewater containing high concentration of antibiotics and organic substances is currently treated with biological processes, but antibacterial activity from the persistent presence of antibiotics could inhibit the biological activity of wastewater treatment plants (WWTPs) due to their strong bacteriostatic effects (Deng et al. 2012, Yi et al. 2016). Therefore, it is expected to develop an efficient pretreatment with discriminating destroy functional groups of antibiotic compounds in multicomponent wastewater. In this study, based on the batch array tests, we selected UV254 light (photons of 254 nm) to reduce antibacterial activity of high concentration antibiotics, including cefalexin (CFX), amoxicillin (AMOX), ampicillin (AMP), tetracycline (TC), ofloxacin (OFX), florfenicol (FLO) and sulfadiazine). With decomposition of typical functional groups under UV irradation, it is demonstrated that antibacterial activity were significantly reduced. As for FLO, photo-defluorination and transformation from thero to erythro configuration was likely the main pathway to reduce its antibacterial activity. Similarly, defluorination was also the main reduction pathway to antibiotic with fluorine substituent, like OFX. The transformation pathway of OFX also included hydroxyl substitution, decarboxylation and the loss of N-methyl piperazine moiety. β-lactam antibiotic, such as CFX, AMOX and AMP, was easily ring-opened by UV irradiation and decreased its antibacterial activity. Additionally, TC has more functional groups, including the tricarbonyl system, dimethyl ammonium and phenolic diketone. Deamidization or damage of diketone structure was likely a pathway to eliminate its antibacterial activity under UV light. The above results indicated that UV photolysis could be adopted as a simple and feasible pretretment strategy for antibiotic containing wastewater.

Following pretreatment, we further studied biological degradation of antibiotic contaminants using efficient antibiotic-mineralizing consortium. Taken chloramphenicol (CAP) for example, an efficient CAP-mineralizing consortium was successfully acclimated in the biological treatment system. This consortium is capable of growing well with CAP as the sole carbon and nitrogen sources and completely degrading 50 mg/L CAP within 24 h under aerobic condition. After 5 d, 71.50±2.63% of CAP was mineralized and Cl- recovery efficiency was 90.80±7.34%. Interestingly, CAP degradation efficiency obviously decreased to 18.22±3.52% within 12 h with co-metabolic carbon source glucose. p-nitrobenzoic acid (p-NBA) was identified as an intermediate product during the CAP degradation process. Microbial community analysis indicated that the dominant genera in the CAP-mineralizing consortium all belong to Proteobacteria (especially the relative abundance of Sphingobium sp. over 63.38%), and most bacteria could degrade aromatic compounds including p-NBA, suggesting these genera involved in the upstream and downstream pathway of CAP mineralization. The community structure and core genera were not remarkblely changed after long term passage, which was consistent with the stable CAP degradation efficiency observed under different culture conditions.

Recent studies showed that low concentrations of antibiotic residues are detected frequently in the effluent of biological treatment (Gonzalez-Gil et al., 2016; Tran et al., 2016). This calls for the development of advanced treatment to alleviate the potential threat of antibiotic-resistant bacteria (ARB) and ARGs. In this study, a graphene modified electro-Fenton (e-Fenton) catalytic membrane (EFCM) was fabricated for in-situ degradation of low-concentration antibiotic FLO. The removal efficiency was 90%, much higher than that of electrochemical filtration (50%) and single filtration process (27%). This demonstrated that EFCM acted not only as a cathode for e-Fenton oxidation process in a continuous mode but also as a membrane barrier to concentrate and enhance the mass transfer of florfenicol, which increased its oxidation chances. The removal rate of FLO by EFCM was much higher (10.2 ± 0.1 mg m−2 h−1) than single filtration (2.5 ± 0.1 mg m−2 h−1) or batch e-Fenton processes (4.3 ± 0.05 mg m−2 h−1). Long-term operation and fouling experiment further demonstrated the durability and anti-fouling property of EFCM. Four main degradation pathways of FLO were proposed by tracking the degradation byproducts. The above results highlighted the feasibility of this integrated membrane catalysis process for advanced water purification.

The ultimate goals of this study are to provide the theoretical support for the deep elimination of emerging antibiotic contaminants in wastewater treatment system based on the multiple coupled technology (UV light pretreatment---biological treatment---electro-Fenton catalytic membrane advanced treatment), as well as offer the feasible and efficient physicochemical and biological (pre)treatment systems for water ecological security.


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Zhu, Y.G., Zhao, Y., Li, B., Huang, C.L., Zhang, S.Y., Yu, S., Chen, Y.S., Zhang, T., Gillings, M.R., Su, J.Q., 2017. Continental-scale pollution of estuaries with antibiotic resistance genes. Nat. Microbiol. 2(4), 16270.<\p>