BIOREMEDIATION OF OIL TAR-CONTAMINATED SOIL

Abstract

Oil tar is a heterogeneous mixture of petroleum compounds, including polycyclic aromatic hydrocarbons (PAHs). These are a significant health concern because many are suspected and known carcinogens. An oil gasification facility in Pt. Stanley, Ontario, Canada, deposited residual oil tars into two onsite lagoons. Using landfarm bioaugmentation technology, Waste Stream Technology was commissioned to remediate 40,000 m3of contaminated soil and accompanying groundwater. Bioremediation was performed in a 150 M x 60 M biopad, confined with an impermeable clay liner and berm. Soil was excavated and stockpiled in a contained pretreatment area, then loaded into the biopad as 4,000-5,000 M3"lifts." WST Bioblend M-5 was used for soil remediation by daily culturing in six 1,300 L bioreactors, followed by soil inoculation and rototilling. Soil was treated daily to achieve a viable microbial concentration of approximately 109colony forming units per gram of soil. Groundwater and rainwater run off was treated in six 10,000 liter fixed film bioreactors supplemented with CAPTM. Treated water was discharged onto the stockpiled, pretreatment soil. Analytical data showed that the water PAH content was reduced from >900 ppb initially, to below detectable limits. Solid phase bioremediation resulted in the reduction of soil PAHs, from an average initial concentration of 1,000 ppm total PAH (TPAH) and 100 ppm Benzo(a)Pyrene, to <100 ppm TPAH and <10 ppm Benzo(a)Pyrene.