Effects of temperature on membrane fouling behavior and mechanisms in an electrochemical anaerobic membrane bioreactor

This study developed an electrochemical anaerobic membrane bioreactor (E-AnMBR) with a conductive filter membrane serving as both filtration medium and bioelectrochemical anode. Results showed that increasing temperature from 25°C to 35°C enhanced electrochemical performance, raising output current from 0.26 to 0.35 mA while reducing ohmic resistance from 1458.10 to 1056.10 Ω. Simultaneously, the abundance of electroactive microorganisms increased from 9.06% to 9.49%, indicating further enrichment. This enrichment considerably improved system performance in degrading membrane foulants. Through the presence of extracellular electrons, the refractory biodegradable humic-like components were effectively removed, as demonstrated by three-dimensional excitation-emission matrix fluorescence spectroscopy. This efficient degradation minimized extracellular polymeric substance (EPS) accumulation (174.82 mg/g MLSS) at 25°C. However, further temperature increases induced microbial stress responses, triggering secretion of protein-rich hydrophobic EPS with protein/polysaccharide ratio rising from 1.21 to 1.63, which increased adhesiveness and fouling potential. Although elevated temperatures improved electrochemical performance and degradation capacity, microbial stress effects ultimately dominated fouling behavior, increasing the membrane fouling rate from 1.08 to 1.48 kPa/d and compromising the fouling control efficiency. This study elucidates a temperature-regulated trade-off between bioelectrochemical degradation of membrane foulants and microbial stress effect within the E-AnMBR, providing a theoretical basis for process optimization and application.