Acceleration of organic removal and electricity generation from dewatered oily sludge in a bioelectrochemical system by rhamnolipid addition

•A bio-cathode BES with dewatered oily sludge as electron donor was constructed.•Power output of BES was significantly increased by rhamnolipids addition.•The electricity conversion process was enhanced in the presence of rhamnolipids.•Anodic microorganisms participating in the sulfate/sulfide cycle were enriched.

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 ± 0.81 W m−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.

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