Biostabilization Technology for Treating PAH- and PCP-Impacted Soil to Environmentally Acceptable Endpoints

Abstract

Data from a 10-year field demonstration at a former wood treating site in Nashua, NH (USA) showed that soil heavily impacted by polycyclic aromatic hydrocarbons (PAH) from coal tar creosote and pentachlorophenol (PCP) was effectively managed using biostabilization. The remedial approach was initiated in 1986/1987 with active land treatment of heavily impacted soil in an engineered, solid-phase biotreatment system. This reduced an initial soil total PAH (tPAH) concentration of ca. 2,500 mg/kg and PCP concentration of ca. 75 mg/kg by >50% and >70%, respectively, within a two-to four-month period. Soil organic chemistry data showed that the soil was effectively stabilized in that there was a significant reduction in the concentration of the more leachable, bioavailable and potentially mobile compounds. Statistically significant data collected over the following six years (1987-1993) suggested a soil half-life for PCP under passive remediation conditions of 1,415 days. The soil half-life for tPAHs was 963 days. First-order decay rates for individual PAHs varied from 856 to 1,733 days. No vertical migration of PAHs or PCP was detected. Data collected in 1997 (ca. 10-years after active treatment) showed an additional half-life reduction in tPAHs from ca. 200 to 100 mg/kg soil given an additional 1,100 days of passive remediation; PCP was more recalcitrant. Nevertheless, passive bioremediation and natural attenuation processes effectively managed residual, less leachable and less mobile compounds as they slowly became bioavailable. Data from inorganic nutrient analyses, compound specific microbial counts, and TCLP analyses also support the position that biostabilization can provide a technically valid, safe and cost-efficient remediation strategy.

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