title: Microbial responses to membrane cleaning using sodium hypochlorite in membrane bioreactors: Cell integrity, key enzymes and intracellular reactive oxygen species.
abstract: Sodium hypochlorite (NaClO) is a commonly used reagent for membrane cleaning in membrane bioreactors (MBRs), while it, being a kind of disinfectant (oxidant), may impair viability of microbes or even totally inactivate them upon its diffusion into mixed liquor during membrane cleaning. In this study, we systematically examine the effects of NaClO on microorganisms in terms of microbial cell integrity, metabolism behaviours (key enzymes), and intracellular reactive oxygen species (ROS) under various NaClO concentrations. Different proportions of microbial cells in activated sludge were damaged within several minutes dependent on NaClO dosages (5-50 mg/g-SS), and correspondingly organic matters were released to bulk solution. Inhibition of key enzymes involved in organic matter biodegradation, nitrification and denitrification was observed in the presence of NaClO above 1 mg/g-SS, and thus organic matter and nitrogen removal efficiencies were decreased. It was also demonstrated that intracellular ROS production was increased with the NaClO dosage higher than 1 mg/g-SS, which likely induced further damage to microbial cells.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Xiaomeng
authors.initials: X
authors.lastname: Han
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China. Electronic address: zwwang@tongji.edu.cn.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Xueye
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Environment and Natural Resources, Renmin University of China, Beijing 100872, PR China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Jinxing
authors.initials: J
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Wu
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D057219:Biofouling / Q000517:prevention & control*; D019149:Bioreactors / Q000382:microbiology*; D002462:Cell Membrane / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D008567:Membranes, Artificial; D059013:Microbial Consortia / Q000187:drug effects* / Q000502:physiology; D010088:Oxidoreductases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012722:Sewage / Q000382:microbiology; D012973:Sodium Hypochlorite / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods
chemical_list: D008567:Membranes, Artificial; D017382:Reactive Oxygen Species; D012722:Sewage; D000255:Adenosine Triphosphate; D012973:Sodium Hypochlorite; D010088:Oxidoreductases
keywords: Cell integrity; Membrane bioreactor; Membrane cleaning; Sodium hypochlorite; Wastewater treatment