Bioremediation of Polycyclic Aromatic Hydrocarbon (PAH) & Pentachlorophenol
Soils impacted with PAH and Pentachlorophenol were treated in situ and ex situ in an independent study for the US EPA Superfund Innovative Technology Evaluation (SITE) program. The in situ treatment plot’s initial mean PAH concentration was 118.0 mg/kg. Chlorophenol was not evaluated in the in situ plot due to a very low initial mean concentration of 1.61 mg/kg. The ex situ treatment plot’s initial mean PAH concentration was 1,774.4 mg/kg, and the chlorophenol initial mean concentration was 182.8 mg/kg. The PAH mean concentrations were reduced by 95%. The chlorophenol mean concentration was reduced by 98%.
Remedial goals for PAHs and chlorophenols were established by the Canadian Council of Ministers of the Environment (CCME) in 1991 (Table 1). To reach these criteria, (e.g., PCP = 5 mg/kg, Benzo(a)pyrene = 10 mg/kg, etc.) removal efficiencies as high as 99% were required in some sampling zones for some compounds.
DARAMEND® was applied ex situ in two treatment cells (plots) and in situ in one treatment plot. The treatment cells were enclosed within a greenhouse enclosure to extend the length of the effective treatment season. DARAMEND® was applied to the soil surface and incorporated to a depth of 2 ft. with a specialized deep rotary tiller. Mixing also aerated and homogenized the soil. Water was then applied to increase and maintain the soil moisture content to 50%-60% of the soil water holding capacity.
DARAMEND® bioremediation technology supported efficient removal of all target compounds in soil at the Domtar Wood Preserving Site to levels below the CCME criteria. This project was evaluated by the US EPA under its SITE program and was determined to be among the most effective bioremediation technologies available for use on soils impacted with wood preserving chemicals.
• PAH concentrations within the ex situ plot were reduced by 95% (1,774.4 mg/kg to 95.2 mg/kg).
• Chlorophenol concentrations within the ex situ plot were reduced by 98% (182.8 mg/kg to 3.3 mg/kg).
• PAH levels within the in situ plot were reduced by 47% (118.0 mg/kg to 62.6 mg/kg).
The costs, as estimated by the US EPA during the SITE program evaluation, were approximately $60/ton for in situ applications and less than $90/ton for ex situ applications.
Treatment required 209 days in one treatment cell, 259 days in the other, and 308 days in situ.