BACKGROUND: An ultrafiltration microbial fuel cell (UF-MFC) is a novel technology that can simultaneously produce high-quality effluent and electricity during wastewater treatment. To increase the power density and mitigate the inevitable biofouling phenomena in UF-MFCs, the anode direct contact (ADC) method was tested. ADC application in UF-MFCs improves the power densities by reducing the distance between the anode electrode and UF membrane (lowering the internal resistance), and mitigates biofouling on the UF membrane surface due to the direct contact of the porous anode electrode with the membrane surface. RESULTS: The maximum power density increased from 76.6 +/- 2.5 mW m(-2) to 129.4 +/- 13.9 mW m(-2) after applying the ADC, with the internal resistance decreasing from 0.49 Omega m(2) to 0.23 Omega m(2). The concentrations of extracellular polymeric substances (EPS) and total cell number were also analyzed as indicators for measuring biofouling on the UF membrane surface. EPS proteins and total cell numbers were reduced (62.8% and 64.9% each) with ADC application after 70 h operation, though no differences were observed in the specific permeate flux. CONCLUSION: ADC application is simple and its use can enhance the power densities and mitigate the biofouling phenomena of UF-MFCs. (C) 2013 Society of Chemical Industry