Mechanistic insights into fouling mitigation by electroactive cathodic dynamic membrane

Membrane fouling is a critical challenge in the long-term operation of anaerobic membrane bioreactors (AnMBRs), and cathodic electroactive dynamic membranes have been proposed as an effective mitigation strategy. In this study, the fouling mitigation mechanism was investigated by comparing an AnMBR with a cathodic electroactive dynamic membrane (AnEDMBR) to a conventional anaerobic dynamic membrane bioreactor (AnDMBR). The AnEDMBR exhibited an approximately 33% reduction in fouling rate relative to the control. This improvement was primarily attributed to selective pressure imposed on membrane-associated microorganisms via local potential modulation, which suppressed highly adhesive species and enriched anaerobic fermentative bacteria. This shift accelerated organic matter degradation and reduced the accumulation of bioavailable carbon. The microbial response induced structural reorganization of extracellular polymeric substances (EPS): the protein content declined significantly, lowering the protein-to-polysaccharide ratio and promoting the formation of a loosely packed, low-aggregation biofilm layer that weakened sludge cohesion. Concurrently, a decrease in membrane zeta potential enhanced electrostatic repulsion and inhibited tight microbial adhesion. Furthermore, a more positive anode and more negative cathode potential facilitated redox reactions and EPS restructuring. Collectively, these effects demonstrate that the cathodic electroactive membrane mitigates fouling through a multi-level mechanism of “electrochemical modulation—microbial response—EPS restructuring—fouling suppression”, providing mechanistic insight and a theoretical basis for the efficient operation of AnMBRs.