Coupling of Biostimulation and Bioaugmentation for Benzene, Toluene, and Trichloroethylene Removal from Co-Contaminated Soil

The coexistence of various organic pollutants in soil always draws extensive attention because of their difficulties and complexity for remediation. Especially, the impacts of bioremediation on soil co-contaminated with benzene, toluene, and trichloroethylene (TCE) have seldom been comprehensively evaluated yet. In this study, the contributions of biostimulation, bioaugmentation, and their combination for the bioremediation of the co-contaminated soil containing benzene, toluene, and TCE were systematically investigated. The addition of nutrients ((NH4)2SO4 (as N source), K2HPO4 (as P source), vegetable oil and CH3COONa (as C sources)) enhanced the degradation efficiency of the co-contaminated soil by 10.19% to 49.62%. The optimal biostimulation condition involved using vegetable oil as the carbon source with a C: N: P ratio of 100: 10: 1. Meanwhile, the addition of the microbial cultures screened and domesticated from the co-contaminated soil, named B-T, effectively enhanced the removal rate of contaminants by 33.02% to 37.55%. The genera comprising Pseudomonas, Stenotrophomonas, and Chryseobacterium in B-T exhibited the highest relative abundance, suggesting their potential for the removal of benzene, toluene, and TCE. Besides, the coupling of biostimulation and bioaugmentation enhanced the degradation efficiency by 62.38% to 68.84%, showing the most effective biodegradation effects. The coupled strategy showed synergistic effects of both, increasing the quantity and activity of microorganisms and accelerating the biodegradation of target contaminants. The findings indicated that the coupling of bioaugmentation and biostimulation treatment strategy holds promise for the bioremediation of benzene, toluene, and TCE from co-contaminated soil.