The effect of crude oil on hydrolyzed polyacrylamide-containing wastewater treatment using microbial fuel cell biosystem

Abstract

One important way to recover valuable energy from the waste streams is to convert organic wastewater into bioelectricity. Microbial fuel cell (MFC) served as the green and sustainable biological treatment can simultaneously treat wastewater and produce moderate amounts of electricity. In the actual hydrolyzed polyacrylamide (HPAM)-containing wastewater of oilfield, crude oil is served as the important active components that affects HPAM bioconversion in biological treatment system. The effect of different crude oil levels on the bioelectric conversion of HPAM in MFC biosystem has not been explored. This study is the first to explore the bioelectric transformation of HPAM-containing wastewater in MFC biosystem under the stress of different initial crude oil levels. The output voltage, current density, coulombic efficiency and power density showed an upward tendency as crude oil level increased (0–300 mg·L−1), and their maximums reached 22.7 V, 267 mA·m−2, 59.6% and 2.42 W·m−2, respectively. The elevation of crude oil level improved HPAM biodegradation, total nitrogen (TN) removal, metabolite production and extracellular polymeric substance (EPS) intensity, and enhanced carbon/nitrogen bioconversion and electron transfer. Geobacter, Pseudomonas, Flavobacterium, Desulfosalsimonas and Acinetobacter exhibited both substrate degradation and bioelectrochemical activity, dominating the biosystem functions associated with bioelectricity generation, substrate bioconversion, metabolite production and EPS intensity. The elevation of crude oil level stimulated the abundance and function of functional bacteria. This study is of dual practical significance for bioenergy recovery and environmentally friendly bioconversion of HPAM-containing oilfield wastewater, promoting the ecological management of oilfields.