Mechanism of mitigating organic fouling on an electro-conductive membrane under anaerobic conditions and cathodic operation

Abstract

Anaerobic electroconductive membrane (ECM) bioreactors are promising wastewater treatment technology, yet their organic antifouling mechanism remains unclear. This research investigated the impact of reactive oxygen species (ROS) oxidation, pH alteration, and electrostatic repulsion on carbon nanotube-based ECM organic fouling. Using a decoupled anode–cathode filtration system ensured unbiased results from the anode while studying distinct conditions near the cathodic ECM surface. The results demonstrated a 50 % reduction in transmembrane pressure (TMP) onset applying potential due to electroosmosis, emphasizing its importance in fouling studies. Fouling experiments using alginate in synthetic wastewater solution showed substantial organic fouling at open circuit potential, −1 and −1.5 V, as the TMP increased by about 2.5 times than the initial value. Fouling decreased significantly at −2.5 V (vs. Ag/AgCl), as indicated by the stable TMP. Analysis of ROS effects and fouling experiments at pH 7–––12 found no influence on organic fouling. Simplified force balance analysis and filtration tests suggested electrostatic repulsion as the antifouling mechanism. At potentials below −2.5 V, electrostatic repulsion maximizes closer to the ECM surface, causing fouling from short-range attractive forces. Electrochemical quartz crystal microbalance analysis at 0.1 V (vs. Ag/AgCl) proposed that a smooth ECM surface can reduce organic fouling at lower potentials.