Microbial fuel cells (MFCs) are a bioreactor system that can generate electricity coupled to the oxidation of organic compounds though microbial actions. MFCs represent a technology for treating wastewater and simultaneously producing electricity. Performance of MFC was evaluated to treat synthetic wastewater and diary wastewater. A two-chamber MFC containing a proton exchange membrane (PEM) was inoculated with an anaerobic digestion sludge of sewage disposal plant. Over a period of a few days, electricity generation gradually increased to a maximum power density of 866 mW/m2. Electricity generation was accompanied with COD removal efficiency of 75.72%. These results indicate that wastewater such a sewage can be used for electricity generation in MFCs while at the same time achieving wastewater treatment.