Accelerated decolorization of azo dye Congo red in a combined bioanode–biocathode bioelectrochemical system with modified electrodes deployment

In this study, BES with bioanode and biocathode was applied to decolorize an azo dye Congo red (CR). Results showed that the Congo red decolorization efficiency (CR-DE) within 23 h in a combined bioanode–biocathode single chamber BES was 98.3 ± 1.3%, significantly higher than that of mixed solution in a dual chamber BES (67.2 ± 3.5%) (P < 0.005). Various electrodes deployments (horizontal, vertical and surrounding) in the combined bioanode–biocathode BES were further compared based on the decolorization performance and electrochemical characterization. Results indicated that CR-DE within 11 h improved from 87.4 ± 1.3% to 97.5 ± 2.3%, meanwhile the internal resistance decreased from 236.6 to 42.2 Ω as modifying the horizontal deployment to be a surrounding deployment. It proved that the combination of bioanode and biocathode with suitable electrodes deployment could accelerate the decolorization of azo dye Congo red, which would be great potential for the application of bioelectrochemical technology in azo dye wastewater treatment.