Bioremediation of a btex contaminated soil and groundwater (ABH petroleum inc. site)

An abandoned underground storage tank was found when a land developer who desired to * purchase a plot of land in northeast Bryan, Texas, USA in January 1995. An environmental site assessment of the area determined that high levels of BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes) were contaminating the soil in the area surrounding the storage tank. in addition, possible groundwater contamination may have also occurred in the water below the vadose zone of the contaminated site. The land was previously owned and operated by a chemical company that used the tank for gasoline storage. Plume size of the site was estimated to include 62,500 cubic meters with leachate percolating into the groundwater. An initial soil analysis of the site found BTEX concentration to be at 6.2 mg per liter.
Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX) are known carcinogens and neurotoxins to mammalian systems. Due to potential health hazards, it was decided that the tank must be removed immediately and bioremediation of the soil and groundwater would begin in early April. Bioremediation of the site would incorporate the use of a mutant strain of Phanerochaete chrysosporium, a bed reactor, and a pump-and-treat system. Phanerochaete chrysosporium is a white-rot fungus that degrades BTEX most efficiently in a non-lignin aerobic environment at 25 degree Celcius and at a pH of 6.5
Initial site analysis found that the soil is a sandy loam with and underlying vadose zone of high porosity. The site, which is a post oak savannah located in the Brazos Valley of Texas is a typical grassland with slightly acidic soils. The underlying groundwater is resting on a clay pan with a slightly sloping grade causing the groundwater to flow in a southeasterly direction.
The remediation of the site, by ABH Petroleum Inc., was estimated to cost 1.2 million dollars and would be completed in September of 1995.