Operation strategy of cubic-meter scale microbial electrochemistry system in a municipal wastewater treatment plant

Abstract

A 1.5 m3 pilot biocathode microbial electrochemistry system (MES) is developed with separate plug-in modular design and operated in a municipal wastewater treatment plant for treating effluent of primary sedimentation tank. Comprehensive operation strategies are investigated for the operation of pilot MES and for the high-efficiency operation of further full-size MES. Controlling with wastewater distribution system, an alternating direction parallel flow mode is achieved in pilot biocathode MES at 48 h interval and prevents the substrate limitation to downstream anodes along flow path. Intermittent aeration strategy with various air-liquid (A/L) ratios is optimized to save aeration energy of biocathode. Consequently, the optimized energy requirement is only 7.3% of that in a typical activated sludge process (0.3 kWh m−3). The dynamic microbial separator in pilot MES effectively blocks the oxygen leakage from cathode to anode compartment under tested A/L ratios (2.9–40) and enables aeration process to mainly affect biocathode performance. The incomplete polytetrafluoroethylene-coated (PTFE-coated) carbon brushes are well performed as biocathodes of pilot MES, improving the maximum power output by 15% under oxygen-limited condition. The hydrophobic surface provides oxygen source for cathode reduction due to the high air-affinity and supports a great amount of biomass on cathode brushes.