Substrate removal and electricity generation in a membrane-less microbial fuel cell for biological treatment of wastewater

•A new membrane-less MFC with a biocathode was developed.•A power density of 30mW/m2 and 75.9% substrate degradation efficiency were achieved.•Pyrosequencing identified Bacteroidia as electron donors in the anode.•Coulombic efficiencies varied from 19.8% to 58.1%. Microbial fuel cells have gained popularity in recent years due to its promise in converting organic wastewater into renewable electrical energy. In this study, a membrane-less MFC with a biocathode was developed to evaluate its performance in electricity generation while simultaneously treating wastewater. The MFC fed with a continuous flow of 2g/day acetate produced a power density of 30mW/m2 and current density of 245mA/m2. A substrate degradation efficiency (SDE) of 75.9% was achieved with 48.7% attributed to the anaerobic process and 27.2% to the aerobic process. Sequencing analysis of the microbial consortia using 16S rDNA pryosequencing showed the predominance of Bacteroidia in the anode after one month of operation, while the microbial community in the cathode chamber was dominated by Gamma-proteobacteria and Beta-proteobacteria. Coulombic efficiencies varied from 19.8% to 58.1% using different acetate concentrations, indicating power density can be further improved through the accumulation of electron-transferring bacteria.