A microbial fuel cell (MFC), a bio-electrochemical device, can simultaneously remove carbonaceous and nitrogenous pollution, while generating bioelectricity. The batch condition was designed with a temperature of 37°C, pH 7.0, and fixed external resistance at 1,000 ohms. At steady state operation, the extent of organic pollutants removed from artificial nitrogen-rich and tannery wastewaters was 590 and 700 mg COD L-1. The nitrogen removal from the artificial wastewater was 384 mg L-1 after 1-d operation and for tannery wastewater the value was 214 mg L-1 after 4-d operation, respectively. Alphaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria are the dominant bacterial groups at the steady state operation. Gammaproteobacteria and Deltaproteobacteria (exo-electrogenic bacteria) were previously reported as electricity producing bacteria. These results confirmed that the MFC could be used for treating wastewater and generating electricity in a single reactor.