Chlorine-resistant bacteria (CRB) in the reverse osmosis system for wastewater reclamation: Isolation, identification and membrane fouling mechanisms

Li-Wei Luo; Yin-Hu Wu; Gen-Qiang Chen; Hao-Bin Wang; Yun-Hong Wang; Xin Tong; Yuan Bai; Yu-Qing Xu; Zi-Wei Zhang; Nozomu Ikuno; Hong-Ying Hu

doi:10.1016/j.watres.2021.117966

Chlorine-resistant bacteria (CRB) in the reverse osmosis system for wastewater reclamation: Isolation, identification and membrane fouling mechanisms

Water Res. 2022 Feb 1:209:117966. doi: 10.1016/j.watres.2021.117966. Epub 2021 Dec 15.

Authors

Affiliations

¹ Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, China; Beijing Laboratory for Environmental Frontier Technologies, Beijing 100084, China.
² Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, China; Beijing Laboratory for Environmental Frontier Technologies, Beijing 100084, China. Electronic address: wuyinhu@mail.tsinghua.edu.cn.
³ Kurita Water Industries Ltd., Nakano-ku, Tokyo 164-0001, Japan.
⁴ Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, China; Beijing Laboratory for Environmental Frontier Technologies, Beijing 100084, China; Research Institute for Environmental Innovation (Suzhou), Tsinghua, Suzhou, Jiangsu 215163, China.

PMID: 34952485
DOI: 10.1016/j.watres.2021.117966

Abstract

Chlorine disinfection is often used as a pretreatment technology to control biofouling of reverse osmosis (RO) membranes. However, previous studies showed that biofouling of the RO system was aggravated after chlorine disinfection. Chlorine-resistant bacteria (CRB) were presumed to be closely related to the aggravation of fouling caused by chlorine disinfection. In order to analyze the membrane fouling mechanisms of CRB, 5 CRB strains were isolated from the surface of fouled RO membranes for wastewater reclamation, and 3 reference bacterial strains, Sphingopyxis soli BM1-1, Pseudomonas aeruginosa PAO1 and Escherichia coli CGMCC1.3373, were selected for comparative study. The chlorine resistance, membrane fouling potential, secretion and adhesion characteristics of these strains were evaluated. Among these isolated strains, 3 strains showed much higher chlorine resistance than PAO1 under the condition of 0.5, 2, 5 mg/L-Cl₂, especially Bacillus CR19 and Bacillus CR2. Furthermore, a significant positive correlation was found between membrane fouling potential and chlorine resistance of all the strains in this study. The membrane fouling potential of the above 8 strains increased monotonically with the increase of chlorine resistance (under the condition of 0.5 mg/L-Cl₂). Serious fouling caused by extracellular substances was observed in biofouling layers of the strains with high chlorine resistance, which lead to more severe flux decline. Extracellular polymeric substances (EPS) amount per cell was found to be the main factor related to the chlorine resistance as well as the fouling potential. Computational fluid dynamics (CFD) simulation was used to demonstrate the filtration resistance induced by the secretion of EPS. However, CRB with higher EPS amount may not show higher membrane adhesion potential, and thus may not be the dominant strain on the RO membranes before chlorine disinfection. These CRB with high fouling potential but low membrane adhesion potential, such as Bacillus CR19 and Bacillus CR2, may become the dominant bacteria on the membrane surface after chlorine disinfection and thus aggravate membrane fouling significantly.

Keywords: Adhesion potential; Chlorine-resistant bacteria (CRB); EPS secretion; Fouling potential; Reverse osmosis.