Low feed water temperature effects on RO membrane fouling development for municipal wastewater reclamation

Understanding the RO membrane fouling development at low feed water temperature plays an important role in the membrane fouling control for wastewater reclamation. In this study, RO membrane fouling development at low feed water temperature (10 °C) was investigated using a lab-scale cross-flow RO apparatus by comparing with that at ambient temperature (25 °C). At low temperature, the normalized flux decline of RO membrane was much milder than that at ambient temperature. The final normalized flux was twice of that at 25 °C. The foulants and biofilm gradually accumulated on the RO membrane, while the living bacteria on the membrane remained stable after a period of running time because of the living space limitation. The amount of the foulants and biofilm thickness at 10 °C were approximately 1/2 of that at 25 °C, while the DOC dissolved by alkali on the membranes at 10 °C were higher than and those at 25 °C. Therefore, alkali cleaning might be more effective in alleviating the membrane fouling at low temperature. Under the selection pressure of low temperature, the microbial community on the RO membranes gradually differentiated from that at ambient temperature. Especially, under low temperature condition, relative abundance of Patescibacteria, which was adapted to oligotrophic, low temperature and high salt environments, was found to gradually increase over time. [Display omitted] •Effect of low temperature on RO membrane fouling development has been evaluated.•The RO membrane fouling development was much milder at low temperature.•The foulant amount and biofilm thickness increase were slower at low temperature.•DOC and living bacteria on the RO membrane were higher at low temperature.•Alkali cleaning might be more effective in alleviating the fouling at low temperature.