An environmentally sustainable approach for online chemical cleaning of MBR with activated peroxymonosulfate

Online chemical cleaning of membrane bioreactor (MBR) has been widely applied as a promising alternative to alleviate membrane fouling, while sustaining the permeability of MBR. However, the conventional chlorine-based chemical cleaning of MBR has been receiving increasing concerns on product water quality, environmental sustainability and human health due to the generation of harmful halogenated by-products. Therefore, in this study, peroxymonosulfate (PMS), a chlorine-free and thermodynamically strong oxidant, was explored as an environmentally friendly agent for online chemical cleaning of MBRs. Results show that the cleaning efficiency of fouled membrane by PMS was comparable with that by NaClO at the same dosages. Moreover, Fe2+-activated PMS could significantly improve the cleaning efficiency of the membrane, leading to a 75% reduction in chemical dosage against NaClO. It was also found that Fe2+-activated PMS was more effective than PMS in removing organic foulants from the cake layer and supressing cell survivability, ultimately leading to significantly reduced adhesion force of foulants to membrane surfaces. More importantly, as a chlorine-free chemical cleaning agent, Fe2thorn-activated PMS had a lower tendency of forming halogenated by-products during chemical cleaning. Consequently, this study indicates that Fe2+-activated PMS offers a promising alternative to commonly used NaClO for online chemical cleaning of MBR, not only for more effective cleaning at lower dosages but also the lack of toxic by-products.