Membrane fouling mitigation by NaClO-assisted backwash in anaerobic ceramic membrane bioreactors for the treatment of domestic wastewater

In this study, the NaClO-assisted backwash was used to mitigate membrane fouling in anaerobic ceramic membrane bioreactors (AnCMBRs) treating domestic wastewater. Four NaClO concentrations (Cbackwash) - 0.05, 0.25, 1 and 10 mg/L were used for backwash. In general, the effectiveness of NaClO-assisted backwash is the balance of two forces - foulants removal from membranes (i.e., the direct effect) and modification of mixed liquor (i.e., the indirect effect). With increased Cbackwash, the direct effect of NaClO was enhanced through removal of more proteins. The indirect effect of NaClO was more complicated. The biodegradability of organics in the wastewater and the microbial activities of biomass were improved with low Cbackwash. However, high Cbackwash deteriorated cell metabolism and led to excessive production of cell lytic products. Optimal Cbackwash that was used in this study - the Cbackwash that provided the best fouling mitigation and acceptable treatment performances - was 1 mg/L.