Enhanced Removal of Azo Dye by a Bioelectrochemical System Integrated with a Membrane Biofilm Reactor

Abstract

Azo dyes and their decolorized products are toxic and persistent to biodegradation, but must be properly removed before dye wastewater being discharged to a water body. In this study, a bioelectrochemical system (BES) combined with a membrane biofilm reactor (MBfR) has been investigated for removing azo dye and its reduction products. Acid orange 7 (AO7) as a model azo dye was efficiently removed (96.5 ± 0.6%) in the BES cathode, and its reduction product - sulfanilic acid was further degraded by the MBfR (64.7 ± 2.7%) at a lumen pressure of 30 psi. Loop operation eliminated the anode substrate addition by taking advantages of residue substrate from the MBfR. The energy consumption by this integrated system was estimated between 1.31 ± 0.01 and 2.33 ± 0.05 kWh kg AO7–1. It was demonstrated by cyclic voltammetry that decolorization products of the AO7 contained in the MBfR effluent could serve as redox mediators for enhancing current generation in the BES.