Enhancing electrokinetic remediation of TPH-Cr(VI) co-contaminated soils with biochar-immobilized bacteria as biological permeable reactive barriers

The co-contamination soil caused by petroleum pollution poses a significant challenge for remediation. The complexity of pollution composition and interaction increases the difficulty of the remediation process. This study established a methodology that employs biochar-immobilized bacteria to enhance the electrokinetic (EK) remediation technique. A 25-day experiment was conducted in the laboratory to remediate co-contaminated soil with total petroleum hydrocarbons(TPH) (9252.51 mg/kg) and Cr (VI) (147.17 mg/kg). The results indicate that adding biochar-immobilized bacteria leads to the most effective remediation performance in the EK system. Compared to the standalone EK remediation, TPH removal efficiency increased by 22.57 %, and the removal rate of Cr (VI) increased by 53.15 %. The study also examined the response of microbial communities in the remediation system. The study results on microbial diversity reveal that introducing the EK system reduces the diversity of soil microbial communities. In contrast, incorporating biochar-immobilized bacteria impacts the microbial community structure in the soil, enhancing microbial communities' stability. This study demonstrates the effectiveness of adding biochar-immobilized bacteria in enhancing EK remediation of co-contaminated soil and its impact on microbial community structure.