Refinery wastewater (RW) treatment in microbial fuel cell (MFC) was studied in batch mode operation followed by continuous mode operation with 8 h and 16 h hydraulic retention time (HRT). The MFC performance was evaluated in terms of power density, organics removal, specific contaminants (oil & grease, phenol and sulfide) removal and energy conversion efficiency with respect to operation mode. Higher power density of 225 +/- 1.4 mW/m(2) was observed during continuous mode operation with 16 h HRT along with a substrate degradation of 84.4 +/- 0.8% including the 95 +/- 0.6 of oil content. The columbic efficiency during this operation was about 2 +/- 0.8% and the projected power yield was 340 +/- 20 kWh/kg CODR/day. Batch mode operation also showed good substrate degradation (81 +/- 1.8%) but took longer HRT which resulted in significantly low substrate degradation rate (0.036 +/- 0.002 kg CODR/m(3)-day) over continuous mode operation (1.05 +/- 0.01 kg CODR/m(3)-day). Overall, current study depicted the possibility of utilizing RW as substrate in MFC for power generation along with its treatment. (C) 2016 Elsevier Ltd. All rights reserved.