Original Date: 11/03/1996
Revision Date: 01/18/2007
Best Practice : Treatment of VOC Contaminated Soils
Oak Ridge National Laboratory (ORNL), in cooperation with university and private industry participants, has developed and successfully demonstrated an in-situ process to treat VOC contaminated soil utilizing soil mixing combined with thermal vapor extraction and peroxidation destruction. These processes were demonstrated at the Department of Energy (DOE) Portsmouth Gaseous Diffusion Plant near Piketon, Ohio.
Land plots were designed twenty years ago at many facilities to facilitate digestion of organic wastes by bacteria occurring naturally in the soil, at that time an acceptable practice. Process waste oils containing degreasing solvents were biodegraded in these plots. Because these oils contained some compounds including VOCs that could not be digested, contaminants remained in the soils and migrated to groundwater beneath the plots. In-situ, or in place, soil treatments today are given a high priority by the DOE to provide an effective alternative to cleaning up sites without the requisite extensive excavation of soils and associated worker exposure, storage, treatment, and disposal issues.
After more than a year of studies and laboratory tests managed by ORNL, a field demonstration was conducted at a large oil biodegradation plot at the Portsmouth facility. Four separate in-situ processes were demonstrated side by side. The most successful processes were peroxidation destruction and thermally enhanced vapor extraction combined with soil mixing. Peroxidation destroys VOCs by a chemical reaction when a diluted hydrogen peroxide mist is applied through an ambient air stream. Thermal vapor extraction involves mixing the contaminated soil with hot air or steam injection to vaporize the VOCs. The vapors are collected in a shroud covering the treatment area and are run through a mobile treatment unit containing both a carbon filter and a high efficiency particulate air filter to remove contaminants.
The peroxidation destruction method performed well with more than 70% VOC removal after one hour of experimental treatment. Enhancing thermal vapor extraction with peroxidation will optimize the process. The in-situ nature of this process reduces the problems and costs associated with worker exposure and storing, treating, and disposing of excavated wastes.
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