Synergistic surfactant cleaning-bioaugmentation strategy enables deep remediation of heavily petroleum-contaminated soils: Field validation and microbial mechanism

Petroleum pollutants pose significant environmental and human health risks, highlighting the urgent need to develop effective methods for remediation of heavily petroleum-contaminated soil. Current surfactant cleaning-bioaugmentation coupled technologies encounter challenges of inadequate profound remediation efficacy. This study conducted a field study of a composite surfactant cleaning method coupled with bioaugmentation in an oilfield. Initially, soil containing 153200 ± 1700 mg/kg total petroleum hydrocarbons (TPH) was washed with the composite surfactant SDBS-TX100, and the TPH was reduced to 36800 ± 1800 mg/kg. Subsequently, 92 days of bioremediation by bioaugmentation using a novel bacterial consortium decreased the TPH to 7600 ± 400 mg/kg, with a degradation rate of 79.35 %. The degradation rates of saturated hydrocarbons, aromatic hydrocarbons, resins, and asphaltenes in the four components of crude oil in the soil were 73.08 %, 73.24 %, 74.19 %, and 77.78 %, respectively. The C10-C40 in soil decreased from 4080 mg/kg to 330 mg/kg, which met the screening value (826 mg/kg) for Class I land use according to the Chinese Soil Environmental Quality-Construction Land Soil Pollution Risk Control Standards (Trial) (GB 36600-2018). This significant reduction is primarily attributed to the increase of soil dehydrogenase activity and the enrichment of alkane-degrading and aromatic-degrading bacteria. The introduction of bacterial consortium effectively regulated the soil microbial community, resulting in the enrichment of functional bacteria capable of degrading petroleum, thus enhancing the degradation process. This study provides a new strategy for the synergistic remediation of heavily petroleum-contaminated soil through composite surfactant cleaning and bioremediation.