Performance and kinetics of benzo(a)pyrene biodegradation in contaminated water and soil and improvement of soil properties by biosurfactant amendment

Abstract

As a hydrophobic pollutant, benzo(a)pyrene (BaP) is difficult to be degraded by microbes due to its poor water solubility. To improve its water solubility, this study harvested a biosurfactant from swine wastewater. The role of the biosurfactant in BaP biodegradation in contaminated water and soil were investigated. The biodegradation kinetics of BaP in contaminated water and the improvement of soil properties were determined. Results showed that critical micelle concentration (CMC) of the biosurfactant was 46.8 mg/L. The biosurfactant has a high pH stability in range of 3–9 and a strong salt stability in NaCl concentration range of 0–20%. At concentrations of 1, 2, 3, 4 and 5 CMC, the biosurfactant increased BaP water solubility by 1.4, 2.6, 4.0, 5.2 and 6.6 times. BaP biodegradation in contaminated water was effectively promoted by the biosurfactant, and the concentrations of BaP in sludge phase decreased to 1.015 mg/L (47.9% decrement) and 0.675 mg/L (65.4% decrement) when the dosed biosurfactant were 1 and 3 CMC, respectively. The biodegradation kinetics of BaP in contaminated water by the biosurfactant fitted well with the two-compartment kinetic model well (R2 > 0.90). For the bioremediation of BaP contaminated soil, adding 0.1%–0.5% (w/w) biosurfactant biodegraded 39.2%–84.8% of BaP, while the control without biosurfactant was 24.2%. In addition, the application of the biosurfactant significantly improved the properties of the contaminated soil, behaved as the increase in microbial quantity, water holding capacity (WHC) and dehydrogenase (DH) activity of the soil. To sum up, the biosurfactant facilitated the BaP biodegradation and can be effectively used in in–site remediation of polycyclic aromatic hydrocarbons (PAHs) (BaP in this study) contaminated water and soil.