Enhancing the anode performance of microbial fuel cells in the treatment of oil-based drill sludge by adjusting the stirring rate and supplementing oil-based drill cuttings

Abstract

This was the first attempt to investigate the bioelectricity output based on a solid–liquid cooperation in the microbial fuel cell (MFC) treatment of oil-based drill sludge by adjusting the stirring rate and supplementing oil-based drill cuttings (OBDCs). According to the results, the maximum power density output reached 671 ± 42.4 mW m⁻² (5.4 ± 0.34 kWh m⁻²) when the stirring rate was 100 rpm and the OBDC concentration was 2 g L⁻¹ in the anode chamber, which was more than 2.4 times as high as that of the control group and significantly higher than those of other MFCs. Extremely high removal efficiencies of chemical oxygen demand (COD), ammonia and total inorganic nitrogen (TIN) were realized in optimization, with values of 52.3 ± 1.9% (the removal quality was 12 081 ± 432 mg L⁻¹), 74.5 ± 0.2% and 58.9 ± 0.2%, respectively. Electrochemical measurement and high-throughput sequencing revealed that the cooperation of stirring and OBDCs could activate microbial activity while reducing the overpotential loss in anode systems and could thus be responsible for the enrichment of electrogenic bacteria with extracellular electron transfer functions (such as Proteobacteria, Bacteroidetes and Actinobacteria) and denitrifying bacteria (such as Bacilli, Anaerolineae and Rhodopseudomonas). Moreover, functional groups were analyzed and phase structure characterization of the substrate was performed via Fourier-transform infrared spectrometry (FTIR) and X-ray diffraction (XRD). This investigation offers a new strategy for the treatment/application of solid and liquid waste produced from oil and gas fields by bioelectrochemical technology.