Mitigating membrane fouling by coupling coagulation and the electrokinetic effect in a novel electrocoagulation membrane cathode reactor

Abstract

Membrane reactors with efficient antifouling and low maintenance are desirable for distributed membrane water treatment. In this study, a novel membrane separation reactor with an Al anode and a conductive membrane as the cathode was built to develop a chemical-free method for mitigating membrane fouling via electrocoagulation coupled with the electrokinetic effect. The electrostatic repulsion between humic acid (HA) and the membrane cathode reduced the adhesion of HA foulants on the membrane, thereby contributing to antifouling in the initial stage. Electrocoagulation and polarization induced by the electric field enlarged the HA-Al flocs, which prevented membrane pore blocking and facilitated the formation of a porous cake layer, thereby leading to a high water flux of the electrocoagulation membrane cathode reactor (ECMCR) in the stable stage. The bubbles from hydrogen evolution on the membrane cathode scoured the HA foulants and washed out the dense cake layer, thereby playing an important role in membrane fouling mitigation. Compared with membrane filtration, the membrane cathode reactor, membrane anode reactor, and HA removal of the ECMCR increased by 9.6, 8.3, and 2.8 times, respectively, whereas the transmembrane pressure decreased by 84.6%, 21.5%, and 63.0%, respectively. The synergy of electrocoagulation and the electrokinetic effect provides the ECMCR with a feasible method of antifouling and improved effluent quality with low maintenance.