Master of Science in Civil Engineering (MSCE)
Civil and Environmental Engineering
The goal of the research presented here was to assess the ability of two bacterial strains, Dehalogenimonas lykanthroporepellens BL-DC-9T and Dehalogenimonas strain IP3-3, to reductively dehalogenate four contaminant mixtures comprised of combinations of the chlorinated solvents 1,2-dichloroethane (1,2-DCA), 1,2-dichloropropane (1,2-DCP), and 1,1,2-trichloroethane (1,1,2-TCA). Both of these bacteria were first isolated from contaminated groundwater at the PetroProcessors of Louisiana, Inc. Superfund site located near Baton Rouge, LA and are of interest because of their novel abilities to transform halogenated alkanes. In previous work (Yan et al., 2009, Bowman et al., 2012), it was demonstrated that both strain IP3-3 and D. lykanthroporepellens BL-DC-9T were able reductively dehalogenate 1,2-dichloroethane, 1,2-dichloropropane, and 1,1,2-trichlorethane when present as individual contaminants. The effects of these compounds as co-contaminant mixtures have not been thoroughly examined until now. Whether transformation of multiple contaminants occurs concurrently (i.e., both compounds transformed simultaneously) or sequentially (i.e., one compound transformed before the other) has important implications when assessing fate and transport of these contaminants in the environment. The experimental protocol involved inoculation of the strains into anaerobic media that had previously been amended with all three possible binary (i.e., two-component) mixtures as well as a three-component mixture. Duplicate batch serum bottles were repeatedly sampled at multiple time steps to assess contaminant transformation over time. Chlorinated solvent depletion and daughter product formation was determined by analyzing both the aqueous and gas headspace concentrations via gas chromatography. Preferential dechlorination of 1,1,2-TCA over both 1,2-DCA and 1,2-DCP was observed for both strains. In the combination of 1,2-DCP and 1,1,2-TCA, 1,2-DCP was not converted to propene until the 1,1,2-TCA aqueous concentration was relatively low (i.e., in the tenths of a mM range). Similarly, when 1,2-DCA and 1,1,2-TCA were present as co-contaminants, 1,2-DCA was not converted to ethene until the aqueous 1,1,2-TCA concentration were lower (i.e., <0.1 mM). When the strains were exposed to a combination of 1,2-DCA and 1,2-DCP, both compounds were utilized concurrently over a comparably large range.
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Dillehay, Jacob Laddye, "Bacterial Dehalogenation of Mixtures of 1,2-Dichloroethane, 1,2-Dichloropropane, and 1,1,2-Trichloroethane by Dehalogenimonas" (2012). LSU Master's Theses. 4099.