High-throughput microbial electrolysis cells (MECs) were used to perform treatability studies on many different refinery wastewater samples all having appreciably different characteristics, which resulted in large differences in current generation. A de-oiled refinery wastewater sample from one site (DOW1) produced the best results, with 2.1±0.2A/m2 (maximum current density), 79% chemical oxygen demand removal, and 82% headspace biological oxygen demand removal. These results were similar to those obtained using domestic wastewater. Two other de-oiled refinery wastewater samples also showed good performance, with a de-oiled oily sewer sample producing less current. A stabilization lagoon sample and a stripped sour wastewater sample failed to produce appreciable current. Electricity production, organics removal, and startup time were improved when the anode was first acclimated to domestic wastewater. These results show mini-MECs are an effective method for evaluating treatability of different wastewaters. © 2013 Elsevier Ltd.