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Abstract
A pilot-scale bioventing test was conducted at the Greenwood Chemical Superfund Site in Virginia. The characteristics of the site included clayey-sand soils and nonfuel organic contamination such as acetone, toluene, and naphthalene in the vadose zone. Based on the results of an earlier treatability study, an 80-ft by 80-ft (24-m by 24-m) treatment plot was established in a 35-ft (11-m) vadose zone. Air was injected at a low flowrate for 15 months. Performance monitoring included initial and final soil analysis and periodic soil gas analysis and in situ respiration tests. After beginning aeration, soil gas oxygen levels in the plot rose slowly, reaching 10% at virtually all measured locations in approximately 4 months. In situ respiration rates decreased with time indicating that the site was being cleaned. Soil concentrations of the target contaminants decreased significantly during the test, with > 98% confidence for acetone, naphthalene, benzene, chlorobenzene, and toluene, and > 90% confidence for 1,2-dichloroethane. Almost 80% of the initial mass of the target contamination was acetone. The bioventing system removed approximately 60 kg of acetone. The total oxygen consumed, estimated from respiration rates, was more than 80 times that needed to degrade the mass of contaminants removed as measured by soil analysis. Thus, it is likely that most if not all of the removal of the target compounds was attributable to biodegradation.