Effect of temperature variation on membrane fouling and microbial community structure in membrane bioreactor

► SMPs and EPS in mixed liquor increased conspicuously as temperature decreased. ► Lower temperature resulted in higher polysaccharide content in SMPs. ► Temperature variation displayed a great influence on microbial community. ► Microbial community would be ultimately responsible for membrane fouling. This study aimed to investigate the effect of temperature variation on membrane fouling and microbial community in a membrane bioreactor (MBRs). The results indicated that extracellular polymer substances (EPS) and soluble microbial products (SMPs) increased due to decreasing temperature, which triggered membrane fouling as evidenced by the trans-membrane pressure (TMP) increase rate. Moreover, fluorescent intensity variations in the excitation–emission matrix (EEM) fluorescence spectroscopy of SMPs were closely related to rapid increase in TMP, suggesting that they might be used to monitor SMPs variations and indicate membrane performance. In addition, 16S rRNA clone library and sequence analyses results demonstrated the predominant phyla were always Proteobacteria, Nitrospira and Bacteroidetes. However, at lower temperature, α-proteobacteria and some filamentous bacteria such as Actinobacteria, Haliscomenobacteria and Thiothrix were relatively rich. At higher temperature, Zoogloea showed its presence. Detrended correspondence analysis (DCA) and Mantel test results also demonstrated that temperature had strongly influence on microbial community.