Combined ozonation and biodegradation for remediation of mixtures of polycyclic aromatic hydrocarbons in soil

A study was conducted to investigate the feasibility of a combined treatment (i.e., ozonation and biodegradation) to overcome the inherent bacterial bioavailability limitation, and hence bioremediation limitation, of polycyclic aromatic hydrocarbons in soil. Ozonation was very efficient in the removal of naphthalene, fluorene, phenanthrene, and anthracene, but not for pyrene, chrysene, and benzo(a)pyrene from soil freshly spiked with the hydrocarbons. A similar result was obtained from coal tar-contaminated soil. Elimination of polycyclic aromatic hydrocarbons increased appreciably in sand containing 0.03% organic carbon, indicating the adverse effect of organic carbon on the efficiency of ozone treatment. In spiked and coal tar-contaminated soils, ozonation followed by biodegradation significantly increased the degradation of various polycyclic aromatic hydrocarbons including chrysene and benzo(a)pyrene which were not degraded by the test bacterial consortium alone. In particular, the effect of the combined treatment was more pronounced in coal tar-contaminated soil than in sterile soil spiked with hydrocarbons, probably due to the augmented biological activity of the introduced consortium. The results suggest that a combined treatment including ozonation and biodegradation may be a promising bioremediation technology in soil contaminated with mixtures of polycyclic aromatic hydrocarbons such as former manufactured gas plant sites.