In Situ Biological Treatment Test at Kelly Air Force Base. Volume 2. Field Test Results and Cost Model

The objective of this effort was to field test in situ biodegradation to treat aquifer contaminants. In situ biodegradation is enhanced by stimulating the indigenous subsurface microbial population by the addition of nutrients and an oxygen source to promote degradation of organic contaminants. In situ treatment affects contaminants sorbed to soil as well as dissolved in groundwater. It is potentially faster, and therefore cheaper, than conventional pump-and-treat technologies. The test site, located at Kelly AFB, Texas, was contaminated 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 chemicals 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.