Effects of applying external voltage on development of anaerobic dynamic membrane under high suspended solids conditions

Maintaining proper dynamic membrane (DM) thickness and structure is the key factor for effective filtration and biomass retention in DM bioreactors. This study investigated the effects of negative and positive applied voltages on the development and characteristics of anaerobic DM under high suspended solids conditions. The DM filtration experiments with anaerobic sludge were performed using submerged DM modules with stainless steel support material at applied voltages of –1.2 to +1.2 V. Negative applied voltage (i.e., cathodic DM) delayed the DM fouling, while positive applied voltage (i.e., anodic DM) accelerated the DM growth, within certain voltage ranges by the combined effect of electrostatic forces and electrochemical reactions. Too large negative or positive voltages caused electrochemical corrosion of support material and precipitation of mineral scales, resulting in serious chemical fouling. The cathodic and anodic DMs formed at different applied voltages achieved high suspended solids rejection efficiencies of 86.4–89.6%. The applied voltage had a significant effect not only on the DM growth and filtration resistance but also the surface morphology, cell viability (live/dead cell ratio), and extracellular polymeric substances distribution of DM. Cell damage by electrochemically formed reactive species was observed at high electrode potentials. The overall results suggest that applying external voltage within an appropriate range can be an effective way to control the DM development. Although much more research is needed, the findings of this study offer a new possibility to improve the feasibility of DM technology and its applicability in anaerobic DM bioreactors.