The Potential for Intrinsic Bioremediation of BTEX Hydrocarbons in Soil/Ground Water Contaminated with Gas Condensate

摘要

Gas condensate liquids contaminate soil and ground water at two gas production sites in the Denver Basin, CO. A detailed field study was carried out at these sites to determine the applicability of intrinsic bioreme-diation as a remediation option. Ground water monitoring at the field sites and analysis of soil cores suggested that intrinsic bioremediation is occurring at the sites by multiple pathways, including aerobic oxidation, sulfate reduction, and possibly reduction Fe(Ⅲ) reduction. Laboratory investigations were conducted to verify that the water-soluble components of the gas condensate (benzene, toluene, ethylbenzene, and xylene [BTEX]) are intrinsically biodegradable under anoxic conditions in the presence of alternate electron acceptors and soil from the field site. Slurry-phase experiments were conducted in which soil obtained from the field site was mixed with an aqueous phase containing nutrients and electron acceptors (nitrate, Fe[Ⅲ], sulfate and carbon dioxide) in serum bottles. The aqueous phase also contained soluble components of gas condensate, at two different hydrocarbon concentrations, obtained from the field site. The soil was either pristine (native) soil or soil obtained from a condensate-contaminated region. The aqueous phase was sampled for electron acceptors, hydrocarbons, and possible products of hydrocarbon degradation. Toluene and xylenes were biodegraded with nitrate or sulfate as the electron acceptor. No degradation of benzene was observed under anoxic conditions.