Cathode membrane fouling reduction and sludge property in membrane bioreactor integrating electrocoagulation and electrostatic repulsion

Abstract

Applying minute electric field on conductive membrane cathode and Fe anode effectively reduced membrane fouling in eMBR (electric field attached membrane bioreactor) by integrating electrocoagulation (EC) with electrostatic rejection of the foulants. The effect and the mechanism of electric currents on the anode corrosion and release of ferrous iron, sludge activity and fouling reduction were investigated in EC-eMBR. Comparative tests were carried out using four reactors, fed with the same influent, but operated under different electric current, constantly at 0mA, 1mA, 3mA and 5mA. Without electric current (0mA), the membrane filtration lasted 34days, when 3times membrane cleaning were conducted (average 11days/cycle). With 1mA current, the filtration lasted 48days with only 2times membrane cleaning (average 24days/cycle), indicating an optimal balanced effect of EC and electrostatic rejection on foulants. Under higher currents at 3mA and 5mA, 3times membrane cleaning were required during 54days and 47days lasting filtration (18days or 16.3days/cycle), respectively. The integration of EC and electrostatic rejection extended the filtration cycle and reduced the cleaning frequency. High currents EC tends to counteract and reduce the electrostatic rejection effect of high currents electric field on foulants. The positive effects of EC included the increase in sludge activity, the decrease of both the extracellular polymeric substance (EPS) and the specific filtration resistances.