In-situ bioremediation of gasoline in soil and groundwater: A case history

This paper presents a case history of the in-situ biotreatment of gasoline in soil and groundwater at a leaking UST site in Greenville, North Carolina. The dissolved contaminant plume covers an area of about 18,000 sq. ft. and to a depth below the land surface (BLS) of about 15 ft. The total volume of the plume (1 pore volume) is estimated at about 40,000 cu. ft. or 300,000 gals. The initial concentration of gasoline in the plume averaged about 40 mg/l of total BTEX with some free phase product present. The in-situ bioremediation system consists of two 4-in. diameter ground water recovery wells, a treatment system and an infiltration gallery for treated effluent recycle to the subsurface. The above ground treatment system consists of transfer pumps, pressure filters, granulated activated carbon filters, air spargers, holding tanks, chemical feed system, propane fired hot water heater and monitoring instruments. The system was operated at a constant recirculation rate of about 25 gpm. The bioenhancement process includes water heating, nutrient demands in the form of monoammonium phosphate and trisodium phosphate and oxygen additions in the form of dilute hydrogen peroxide.