Simultaneous carbon removal, denitrification and power generation in a membrane-less microbial fuel cell

•It may be the first time to achieve denitrification in the cathode of ML-MFC.•Increase of ammonia in cathode might be due to dissimilatory nitrate reduction.•The cathodic coulombic efficiency was from 152% to 475%, calculated with new method. A membrane-less microbial fuel cell (ML-MFC) was developed to investigate the simultaneous carbon removal and denitrification. The removal rates of 0.64kgCODm−3 of liquid cathode volume (LCV)d−1 and 0.186gNO3-–Nm-3 of LCVd−1 were achieved, which resulted in the maximal COD and nitrate removal rates of 100% and 36.7%, respectively. The ML-MFC also achieved a maximal power output of 0.0712Wm−3 of LCV and 0.844Am−3 of LCV in approximately 24h. The maximal coulombic efficiency of anode (CEAn) and cathode (CECa) was 5.1% and 475%, respectively. The anodic gas phase was consisted of 77.2±4.0% CH4, 3.9±0.5% CO2, and 3.9±1.5% N2, which indicated that the low anode coulombic efficiency was due to anodic methane production. The results of this study demonstrated the potential application of ML-MFC in simultaneous carbon and nitrogen removal and energy (electricity) production.