Voltage-Dependent Metabolic Shifts Regulate the Fouling Behavior of the Anaerobic-Anodic Membrane

Fouling remains the key barrier to durable membrane operation, against which electrochemical processes offer a promising fouling control strategy. However, the performance of an anodic membrane under anaerobic conditions exhibits significant instability, the mechanism of which remains unclear and represents a critical knowledge gap. This study systematically investigated the response of membrane fouling evolution to gradient electric fields within anodic membranes. A distinct threshold behavior of electric field strength on membrane fouling was observed, with a system-dependent threshold occurring between 0.7 and 1.0 V. Following an initial fouling layer, subthreshold fields (≤0.7 V) exacerbated fouling accumulation, whereas supra-threshold fields (≥1.0 V) slowed down membrane fouling development. Comprehensive analysis revealed that surpassing critical field strength enhanced anodic electron-accepting capacity, likely facilitating microbial extracellular electron release and alleviating reductive pressure. This triggered a nonlinear, threshold-dependent metabolic switch from biosynthesis-dominated to catabolism-enhanced pathways, coupled with quorum quenching that inhibited biofilm maturation. These synergistic transitions underpinned the fouling reversal. This work advances the understanding of anaerobic-anodic membrane fouling from an empirical observation into a threshold-governed electrochemical–microbial switching process, thereby providing the scientific foundation for harnessing this interplay to achieve durable and efficient operation in anaerobic wastewater treatment and resource recovery systems.