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Use of C2 to C10 Organic Acids to Enhance Bioremediation of DNAPL Contaminated Aquifers

Principal Investigators
S.A. Gibson, J.C. Tracy, and M.S. Kennedy, South Dakota State University


Goal: This project will address the possibility of using sodium salts of organic acids from 2 carbons to 10 carbons in length to support dehalogenation of chlorinated hydrocarbons.

Rationale: Previous work has demonstrated anaerobic biotransformation of chlorinated solvents both in laboratory settings and in field demonstrations. However, there has been no investigation of the addition of organic electron donors to both increase solubility and to act as the electron donor for dehalogenation. Also, there is no clear delineation of the upper concentrations at which reductive dechlorination is possible. This study will provide information regarding the potential for use of medium length fatty acids for bioremediation of chloroethenes. Applications of these results could facilitate development of technologies for in situ bioremediation of dense nonaqueous phase liquid (DNAPL) contaminated aquifers.

Approach: The project will consist of four phases: (1) evaluating different concentrations of the sodium salt of each acid on the solubility and diffusion rate of tetrachloroethene (PCE) and trichloroethene (TCE) into water; (2) delineating the concentrations of each acid which can support dehalogenation of PCE or TCE in slurries made using aquifer solids from an anaerobic zone in chloroethene-contaminated aquifer and site ground water; (3) determining the microbial community tolerance to high levels of PCE or TCE; and (4) modeling of the predicted movement of selected chloroethene, added electron donor, acetic acid, and partially dechlorinated chloroethene intermediates which are formed in the aquifer.

Status: Start-up activities for this project have been initiated. Eight surfactants have been selected for evaluation of the effect of their presence on PCE dechlorination. Polyoxyethylene ethers to be used are 10 Lauryl Ether, 10 Cetyl Ether, 10 Stearyl Ether, 10 Oleyl Ether, 20 Cetyl Ether, 20 Stearyl Ether, 20 Oleyl Ether, and 23 Lauryl Ether. Initial microcosms have been started to screen site material for the potential of the indigenous organisms to anaerobically degrade the surfactants in question at 1 mM concentrations. The R.S. Kerr Environmental Research Lab has been invited to collaborate on the project. This project is in its first year.

Clients/Users: This project will be of interest to other researchers and federal agencies.

Key words: organic acids, bioremediation, dense nonaqueous phase liquids, aquifers.

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