Conversion of biomass energy of dewatered oily sludge to electricity is the rate-limiting process in bioelectrochemical system (BES). In this study, 2 mg g(-1) rhamnolipids were added to dewatered oily sludge, resulting in a significant enhancement in maximum power density from 3.84 +/- 0.37 to 8.63 +/- 0.81Wm(-3), together with an increase in total organic carbon (TOC) and total petroleum hydrocarbon (TPH) removal from 24.52 +/- 4.30 to 36.15 +/- 2.79 mg g(-1) and 29.51 +/- 3.30 to 39.80 +/- 2.47 mg g(-1), respectively. Rhamnolipids can also enhance the solubilization and promote the hydrolysis of dewatered oily sludge with increases in SOCD from 14.93 +/- 2.44 to 18.40 +/- 0.08 mg g(-1) and VFAs from 1.02 +/- 0.07 to 1.39 +/- 0.12 mg g(-1). Furthermore, bacteria related to substrate degradation were predominant in dewatered oily sludge, and bacteria related to the sulfate/sulfide cycle were significantly enriched by rhamnolipid addition. (C) 2017 Elsevier Ltd. All rights reserved.