Low-voltage electric field applied into MBR for fouling suppression: Performance and mechanisms

A low-voltage electro-membrane bioreactor (e-MBR) for fouling alleviation was designed using stainless steel anodes and a membrane module containing titanium cathodes (Fe-MBR). The electric field was applied intermittently once the suction pump was stopped. Compared with another e-MBR with titanium anodes (Ti-MBR) and with one MBR without an electric field, the Fe-MBR had lower transmembrane pressure (TMP), less irreversible fouling and higher pollutant removals under an intermittent voltage of 2.72 V and current of 0.1 A. Coagulation was not obvious because no significant changes were observed in either particle size or zeta potential. The electric field induced backwash was confirmed, by the Ti-MBR, to be effective to suppress fouling. The electric field force might prevent the tight precipitation of foulant on the membrane's surface and make the fouling layers looser and easier to be removed by aeration. Besides, a strong positive correlation was obtained between fouling indexes and total organic carbon of soluble microbial products (SMPs), suggesting that the reduction of SMPs in the Fe-MBR could have resulted in the fouling depression, and was related to the release of iron. Thus, the joint effects of the electric field force and the release of iron deducted foulant and irreversible fouling, and ultimately lessened the overall fouling. The energy consumption estimation showed 10% more electricity was consumed to make TMP reduce by 30%, indicating the Fe-MBR would be promising in application.