Bioaugmentation of butane-utilizing microorganisms for the in situ cometabolic treatment of 1,1-dichloroethene, 1,1-dichloroethane, and 1,1,1-trichloroethane

Bioaugmentation of microbial cultures is a potential method to enhance the performance of in situ bioremediation. In this study we evaluated the bioaugmentation of aerobic microorganisms that grow on butane that can transform chlorinated aliphatic hydrocarbon (CAH) mixtures, such as 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichhloroethane (1,1-DCA) and 1,1-dichloroethene (1,1-DCE). This mixture of contaminants is of interest, since 1,1,1-TCA was a frequently used solvent at Department of Defense (DoD) facilities in the United States, and 1,1-DCE and 1,1-DCA are abiotic and biotic transformation products of 1,1,1-TCA. Kinetic studies with butane grown enrichment cultures and pure cultures isolated from the enrichment culture showed effective transformation of mixtures of these contaminants, with 1,1-DCE most rapidly transformed, followed by 1,1-DCA, and 1,1,1-TCA. In laboratory microcosm batch experiments, with aquifer material and groundwater from the field site, microcosms bioaugmented with mixed and pure cultures outperformed microcosms where indigenous butane-utilizing microorganisms were stimulated. The microcosm tests were consistent with the kinetics from mixed and pure cultures. Field studies were conducted in the saturated zone at the Moffett Field In Situ Test Facility in California. Tests were performed in an indigenous test leg along with a bioaugmented test leg, and the bioaugmented test leg outperformed the indigenous test leg. In the bioaugmented leg, 1,1-DCE was more effectively transformed, followed by 1,1-DCA, and 1,1,1-TCA, consistent with the results from laboratory kinetic studies and microcosm studies.