In this study, the microbial electrolysis cell (MEC) was examined for treatment of wastewater containing nickel ion (Ni2+). Effects of initial Ni2+ concentrations in catholyte, pH values of catholyte, and applied voltages on MEC performance were determined. Results showed that the Ni2+ removal efficiency with the MEC was three times higher than those with an electrolysis cell and a microbial fuel cell. Ni2+ removal efficiencies decreased from 99 +/- 0.6% to 33 +/- 4.2% with the initial Ni2+ concentrations from 50 to 1000 mg/L, while the mass removal of Ni2+ increased consistently with the initial concentrations. Ni2+ removal efficiencies in the MEC increased from 51 +/- 4.6% to 67 +/- 5.3% with the applied voltages from 0.5 to 1.1 V. These results demonstrate that the MEC can be an alternative process to effectively remove Ni2+ from wastewater. (C) 2012 Elsevier Ltd. All rights reserved.