This Small Business Innovation Research Phase I project will explore ways to treat chlorinated solvent contamination in subsurface environments such as aquifers. Chlorinated solvents, like trichloroethylene (TCE), are particularly prevalent aquifer contaminants. Depending on the degree of contamination, their physical properties may cause them to occur as DNAPLs and sorb to aquifer sediments, which make them difficult to remediate by pump-and-treat methods. For these cometabolic contaminants, biodegradation by indigenous bacterial populations may be limited by the lack of a suitable indigenous population or inducing cosubstrates for degradative activity. For many sites, especially aquifer contamination, remediation will require bioaugmentation or the introduction of degradative bacteria into the subsurface. ENVIROGEN has developed bacteria specifically for the in situ remediation of chlorinated solvents. These strains are adhesion-deficient for enhanced transport; they express TCE-degrading enzymes constitutively, eliminating the need for inducing cosubstrates; and they can be grown with large amounts of energy storage polymers for prolonged degradation. The application of these strains, however, may be limited at sites that have extensive DNAPL contamination. Free product chlorinated solvents are toxic to these bacteria. To broaden the applications for these highly specialized organisms, we propose to combine these organisms with a foam technology which will act to disperse the microorganisms as well as the DNAPLs, thereby reducing their toxicity. This foam technology may also provide a mechanism for providing nutrients and oxygen to extend the degradative activity of the introduced strains. The successful demonstration of the proposed work will result in an in situ bioaugmentation technology for treating even the most highly contaminated aquifers. This technology is broadly applicable; chlorinated solvents are common groundwater contaminants at both government and private sites.
