Combined Air Sparge and Bioremediation of an Underground Coal Gasification Site

EG&G Technical Services of West Virginia (TSWV) Inc. is successfully remediating a former underground coal gasification (UCG) test site in northeastern Wyoming. EG&G is demonstrating the effectiveness of combined air sparge and biostimulation technology. This project is being conducted for the U.S. Department of Energy (DOE ) - Morgantown Energy Technology Center (METC), the lease holder of the site. UCG testing from 1976 through 1979 contaminated three water-bearing units at the site with benzene. Previous pump and treat operations at the site showed the presence of a persistent non-dissolved benzene source material. The Felix I coal seam is the most contaminated unit at the site and was the target unit for the initial demonstration. Air sparging was selected to strip dissolved benzene, volatilize the non- dissolved benzene source material, and to provide oxygen for increasing aerobic bacteria populations. Indigenous bacteria populations were stimulated with ammonium phosphate addition. EG&G designed the remediation system to take advantage of the hydrogeologic environment to produce a cost-effective approach to the groundwater remediation. Groundwater pumping was used to manipulate subsurface air flow, nutrient transport, and biomass management. Demonstration operations began on September 29, 1995, and were suspended on April 30, 1996 to begin demonstration expansion. Initial results of the demonstration show substantial reduction in benzene concentrations across the demonstration area. Benzene concentration reductions greater than 80% were observed two months after demonstration operations were suspended