Joint response mechanism of bioanode and biocathode in single chamber biocathode microbial electrochemical systems started-up with a constant and low resistance

Abstract

Microbial electrochemical systems (MESs), particularly biocathode MESs, are recognized as environmentally friendly technologies in wastewater treatment. Rapid start-up and achievable high current and power density are desirable for scaled-up MES. The high output current can be obtained under low external resistance, but the response behaviors of bioanode and biocathode during start-up stage under low external resistance need to be clarified. In this study, a 10 L single-chamber biocathode microbial electrochemical system with microbial separator was successfully started within 11 days under a low external resistance of 20 Ω. The maximum power density reached 116.6 mW/m2 on the 9th day. However, the competition between oxygen-reducing bacteria and filamentous bacteria in the biocathode caused the decreased output power and power overshoot. Reducing the external resistance not only eliminated the power overshoot but also enhanced the electroactivity and organic removal efficiency of the bioanode. Additionally, it alleviated the constraint of filamentous bacteria on oxygen mass transfer, thereby enhancing the performance of the biocathode. The comprehensive regulation of the bioanode and the biocathode performance was achieved by reducing external resistance. This study analyzed the joint response mechanism of the bioanode and biocathode, aiming to provide guidance for the application of biocathode microbial electrochemical systems.