Removal of nutrients and pharmaceutical and personal care products in an electroconductive bed-membrane bioreactor (EcB-MBR): The role of conductive media

Abstract

In our previous work, an electroconductive moving bed membrane bioreactor was developed by introducing conductive media into an electrically assisted membrane bioreactor (EMBR). It incorporated microbial degradation, electrochemical processes, and membrane filtration for enhanced simultaneous removal of organics and nutrients. However, the additional aeration energy for suspending conductive media in the mixed liquor and the consumption of the reactive anode left bottlenecks for its broader application. In this study, an electroconductive bed membrane bioreactor (EcB-MBR) was developed. Graphite felt at a packing density of 0.10 (v/v) was equipped as the conductive media, and the anode was composed of a graphite electrode combined with iron. Simultaneous COD, TP, and TN removals of 98.5 ± 1.0%, 98.9 ± 0.7%, and 48.5 ± 14.9%, respectively, were achieved in the EcB-MBR. Specifically, TN removal significantly increased by approximately 89.5% compared with that in an EMBR under the same operating conditions (5 min-ON/5 min-OFF at 6.67 A/m2). The conductive media reduced the resistivity of mixed liquor, which enhanced electrochemical processes. In addition, the felt configuration served as a biocarrier and provided more reaction sites for microbiological activity. A 45.5% reduction in extracellular polymeric substances was observed in the EcB-MBR, probably due to the local electrochemical oxidation occurring on the conductive media. Nevertheless, insignificant membrane fouling control was achieved due to the fixed operating mode of the conductive media. Furthermore, the EcB-MBR successfully eliminated up to approximately 98% of several selected pharmaceutical and personal care products, demonstrating its ability to handle emerging contaminants in municipal wastewater.