In-situ biological treatment test at Kelly Air Force Base. Volume 2. Field test results and cost model. Final report, 1 June 1985-31 May 1987

The objective of this effort was to field test in-situ biodegradation to treat aquifer contaminants. In-situ biodegradation is enhanced by stimulating in indigenous subsurface microbial population by the addition of nutrients and an oxygen source to promote degradation of organic contaminants. In-situ treatments affects contaminants with a mixture of organic and inorganic chemicals. The treatment system consisted of an array of nine pumping wells and four infiltration wells. These wells circulated groundwater and transported the treatment chemical s throughout the 2800-square-feet treatment area. Oxygen was supplied by means of a hydrogen peroxide solution. Nutrients were principally ammonium and phosphate salts. The system was operated for 9 months. Data showed evidence of both aerobic and anaerobic biodegradation. Decreases in tetrachloroethylene and trichloroethylene concentrations in groundwater correlate with anaerobic microcosm tests. Aerobic biodegradation was indicated by acid and carbon dioxide production, and increases in petroleum hydrocarbon concentrations in groundwater, However, any biodegradation of these hydrocarbons was too small to be quantified. The study confirms that indigenous bacteria can be enhanced to degrade organic contaminants. The problems with in situ treatment are primarily those of delivery of chemicals and minimizing adverse reactions between injection chemicals and subsurface minerals.