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 degrees C) was investigated using a lab-scale cross-flow RO apparatus by comparing with that at ambient temperature (25 degrees 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 degrees 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 degrees C were approximately 1/2 of that at 25 degrees C, while the DOC dissolved by alkali on the membranes at 10 degrees C were higher than and those at 25 degrees 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. Espe-cially, under low temperature condition, relative abundance of Patescibacteria, which was adapted to oligo-trophic, low temperature and high salt environments, was found to gradually increase over time.

Automated summary

Understanding the RO membrane fouling development at low feed water temperature is crucial for effective fouling control in wastewater reclamation. This study found that fouling development at a low temperature was milder, with less accumulation of foulants and biofilm on the RO membrane. Alkali cleaning was also more effective at alleviating membrane fouling at low temperature. The microbial community on the RO membrane gradually differentiated under the low temperature condition, with an increase in the relative abundance of Patescibacteria, which are adapted to oligo-trophic, low temperature, and high salt environments.