TREATMENT OF PAHs USING OZONE GAS FOR IN-SITU OXIDATION

摘要

In-situ ozonation is an emerging technology for the in-situ destruction of recalcitrant organic contaminants, such as polynuclear aromatic hydrocarbons (PAHs). The technology involves the injection of ozone (O_3) gas into the subsurface to chemically oxidize organic compounds. An intensively monitored field-scale application of in-situ ozonation was performed at a former wood treatment and cooling tower manufacturing facility, located in Sonoma County, California. Primary contaminants are pentachlorophenol (PCP) and creosote (i.e., polynuclear aromatic hydrocarbons (PAHs)). The project indicated successful treatment of PAHs and PCP by in-situ ozonation, despite the presence of highly heterogeneous, variably saturated, clayey subsurface conditions. Contaminant mass was reduced by 93% and non-aqueous phase liquid (NAPL) contamination was eliminated within one month of initiation of ozone injection. Treatment is ongoing, and further reductions are expected. The maximum pretreatment soil contamination was reduced greater than 98 percent from an initial value of 220 mg/kg PCP and 5,680 mg/kg total PAHs to below detection limits. Treatment of contaminants was non-selective, i.e. low solubility compounds such as benzo-a-pyrene were treated at the same rate as higher solubility compounds such as napthalene. This implies that in-situ ozonation directly attacks NAPL and sorbed contamination and is not limited by contaminant solubility. Ozone consumption was calculated at approximately 7 Ibs ozone per Ib. of PCP and PAH contaminant destroyed. This number is highly conservative, because the system was optimized for maximum ozone loading, and not for efficient ozone usage.