Enhanced crude oil degradation and reshaped microbial community structure using straw-sludge biochar-persulfate oxidative system in oil-contaminated soil

Abstract

The straw-sludge biochar is an environmentally friendly and novel alternative activator. In this study, a novel biochar (SSBC), co-pyrolyzed by waste rice straw and municipal sludge using ZnCl2 activation method, was applied in persulfate (PS)-based remediation for crude oil in soil, which has a high efficiency up to 69.11% in 35 days. Compared with sludge-BC, SSBC had a higher surface area of 667.81 m2‧g−1, pore volume of 0.47 cm3‧g−1, and pore surface area of 233.22 m2‧g−1, FT-IR showed that SSBC is in richer surface functional groups, e.g., -COOH with a content of 1.03 mM‧g−1 and -OH with a content of 2.77 mM‧g−1, which were responsible for its good PS activation performance. Besides, the EPR results showed that SSBC activated PS to generate SO4−• and •OH, which certainly supported the construction of the system. In SSBC-PS oxidative system, the SSBC dosage (0.03 g), the PS dosage (1 mM) and the initial pH value (7) of the system were optimized, and it were applied in oil-contaminated soil. Owing to the SSBC-PS oxidative system, the crude oil degradation rate reached to 34.17% in first week. And these long-chain alkanes were oxidized to short-chains, or cyclane and aromatics were oxidized into short-chain alkanes. Besides, the relative abundance of potential crude oil degraders greatly increased finally, including Alcanivorax (12.52% ∼ 12.86%), Marinobacter (10.78% ∼ 12.54%), Aliifodinibius (7.01% ∼ 7.09%) and Salinisphaera (6.55% ∼ 7.16%), which changed organic pollutions to CO2 and H2O via TCA cycle in crude oil degradation process. Consequently, the combination of SSBC-PS oxidative system and indigenous microbes would be a potential application in crude oil-contaminated soil remediation.