Study on biofouling mechanism in IMBR for wastewater treatment with different temperatures

The main goal of the present study was to examine the operating characteristics and mechanisms of membrane fouling in integrated membrane bioreactors (IMBRs) at different temperatures. Two IMBRs, each with identical dimensions and configurations, were used in the study using synthetic domestic sewage at a low temperature (10°C) and high temperature (25°C). The results indicated that the removal efficiency of chemical oxygen demand reached 93–96%, but the membrane contribution rate of IMBR2 (10°C) was higher than that of IMBR1 (25°C). The separation burden of the membrane on organic compounds increased at low temperature, which may have sped up the rate of membrane biofouling. The absolute rate of trans-membrane pressure build-up was faster at low temperature, leading to shorter IMBR operating times. Soluble microbial products (SMPs) and extracellular polymeric substances (EPSs) in the IMBRs significantly increased at low temperature. These substances intensified deflocculation, with an accompanying reduction of floc size and the release of EPSs at low temperature, which facilitated the formation of cake foulants on the surface, covering the entire membrane area. The protein and polysaccharide concentrations of SMPs and EPSs in the IMBRs were correlated with the concentration of C8-HSL. It was demonstrated that temperature affected the concentration of C8-HSL, which controlled the excretion of EPSs and SMPs and thus the membrane biofouling process.