Pilot scale ex-situ bioremediation of heavily PAHs-contaminated soil by indigenous microorganisms and bioaugmentation by a PAHs-degrading and bioemulsifier-producing strain

This study aims at the remediation of heavily PAH-contaminated soil containing 375 mg of total PAHs per kilogram dry soil. Pilot scale bioremediation experiments were carried out by three approaches with contaminated soil from abandoned sites of Beijing Coking Plant using outdoor pot trials. The first approach was bioaugmentation with a bacterial strain which degrades PAH and produces bioemulsifier, the second approach comprised of biostimulation of indigenous microorganisms with supplementing nutrients and the last approach involved the combination of both biostimulation and bioaugmentation. An on-site land farming group was set as a control in which the total PAHs and 4-6 ring-PAHs were reduced by 23.4% and 10.1%, respectively after 175 days. Meanwhile, in the first approach group, the total PAHs and 4-6 ring-PAHs were reduced by 26.82% and 35.36%, respectively; in the second approach group both percentages were 33.9% and 11.0%, respectively; while in the third approach group, these pollutants were reduced by 43.9% and 55.0%, respectively. The results obtained suggested that biostimulation and bioaugmentation combined could significantly enhance the removal of PAHs in the contaminated soil.