A membrane-less microbial fuel cell (ML-MFC) was developed to investigate the simultaneous carbon removal and denitrification. The removal rates of 0.64 kg COD m(-3) of liquid cathode volume (LCV) d(-1) and 0.186 g NO3--N m(-3) of LCV d(-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 0.0712 W m(-3) of LCV and 0.844 A m(-3) of LCV in approximately 24 h. 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% N-2, 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. (c) 2013 Elsevier Ltd. All rights reserved.