Biosurfactant-Enhanced Electrokinetic-Biobarrier Remediation of Polycyclic Aromatic Hydrocarbon-Contaminated Soil from an Industrial Site
Polycyclic aromatic hydrocarbons (PAHs) in industrial soils pose significant risks due to their hydrophobicity and low bioavailability, limiting the efficacy of bioremediation. This study investigated the enhancement of an in-situ electrokinetic-biological barrier (EK-BB) system for PAH-contaminated soil using biosurfactants. Three biosurfactants—rhamnolipid (RL), alkyl polyglycoside (APG), and saponin (SAP)—were applied individually and in combinations at 10× critical micelle concentration (CMC), and the optimal RL+APG mixture was further tested at 2.5, 5.0, 7.5, and 10× CMC. Results showed that biosurfactant application improved soil electrical current, moisture retention, and PAH removal. Combined surfactants outperformed single ones, with the 10× CMC RL+APG treatment (Exp IV) achieving the highest average current intensity and moisture content, 1.31 and 1.12 times that of the control (CK), respectively, and a PAH removal of 106.02 mg·kg⁻¹. Biosurfactants also promoted bacterial growth in both contaminated soil and the biobarrier layer; the 10× CMC RL+APG treatment increased bacterial counts by 6.24-fold and 44.8%, respectively. However, excessive surfactant concentrations led to PAH accumulation in the biobarrier and clean soil. The 5× CMC RL+APG treatment provided optimal balance, maximizing PAH removal while maintaining barrier effectiveness. These findings confirm that appropriate biosurfactant concentrations can enhance EK-BB remediation, offering technical support for PAH-contaminated site remediation and safe reuse.