Thermal remediation involves heating subsurface environments and collecting fluids in order to recover contaminants such as tetrachloroethylene (PCE) and trichloroethylene (TCE). While increasing subsurface temperature can lead to changes in the distribution of contaminants between the solid, liquid, and gas phases, there is also an increased potential for PCE and TCE to degrade. This work was performed to determine the rate of PCE and TCE degradation and products formed in laboratory-scale experiments designed to simulate thermal remediation conditions. The conditions during transport of gas-phase TCE were simulated using flow-through experiments in the temperature range from 60 to 800C. Degradation of TCE was not evident at temperatures of less than 240C; however, chloroacetic acids, which comprised less than 0.1% of the influent TCE on a carbon basis, were detected. At temperatures greater than 300C, TCE readily degraded where the identities of the degradation products were a function of oxygen and water content. With oxygen present, TCE degraded to form CO, phosgene, CO2 with minor amounts of hexachloroethane, PCE, and carbon tetrachloride. Increasing the amount of water vapor was found to decrease the amount of TCE degraded. Vapor recovery systems used during thermal treatments are anticipated to capture these TCE degradation products. However, the amount of missing carbon (~17%) in experiments completed at 800C makes the prospect of recovering all TCE degradation products doubtful. Experiments were conducted using hermetically sealed ampules to simulate heating dissolved phase PCE and TCE over periods of up to 75 days. At 120C, the first-order TCE degradation half-life was 330 days and the degradation products included CO and CO2, glycolate, formate, and chloride. The rate of TCE disappearance was increased with the addition of 1% (wt.) goethite, which suggests that the presence of iron bearing soil minerals can increase rates of TCE degradation during thermal treatment. In contaminated field samples, TCE was found to degrade to form cis-1,2-dichloroethylene at 95C coincident with the formation of hydrogen gas. Degradation of PCE was not evident in field samples or in deionized water and is not expected to degrade during thermal remediation at temperatures below 95C.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 156-168). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 156-168). Also available on the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1949. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references: leaves 81-82.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 287-290).

Thesis (M. Env. St.)--University of Adelaide, 1984. / Dated 1983. Includes bibliographical references (leaves 174-181).

Thesis (Ph.D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Löffler, Frank E.; Committee Member: Hughes, Joseph B.; Committee Member: Pennell, Kurt D.; Committee Member: Spain, Jim C.; Committee Member: Taillefert, Martial

Thesis (M.S.)--University of Nevada, Reno, 2008. / "December, 2008." Includes bibliographical references (leaves 105-109). Online version available on the World Wide Web.

Chlorinated solvents are among the most prevalent contaminants at Superfund sites. Perchloroethylene (PCE) and its degradative byproducts pose a particular problem because of their persistence in the subsurface and their threat to ecological health. In this study, microcosms were used to test the viability of bioaugmentation as a possible remediation strategy at a PCE contaminated site at the Naval Amphibious Base at Little Creek located in Virginia Beach, Virginia. All microcosms were created in duplicate using spatially diverse soils and the bioaugmented series innoculated with a mixed microbial culture provided by the Dr. Frank Loffler. This culture has been found to be capable of completely degrading PCE to ethene. The aqueous ethene concentration was monitored over time. It is clear from the results that bioaugmentation successfully increased the degree of reductive dechlorination over their static counterpart. Without innoculation, shallow static microcosms showed an accumulation of cis-DCE, while deep soils never showed conversion beyond TCE. Shallow bioaugmented microcosms showed the production and loss of vinyl chloride indicated probable complete conversion of PCE to ethene while deep soils showed the production of cis-DCE. These differences in dechlorination between shallow and deep soils indicate a possible disparity in reduction capacity. At day 78, microcosms were spiked with higher concentrations of PCE resulting in a reduction in dechlorination activity. Static microcosms exhibited similar degradative trends but bioaugmented batches experienced dramatic reductions in dechlorination activity indicating possible inhibition effects of native organisms due to concentration or potential toxic shock. It appears that bioaugmentation is a remediation alternative worthy of further study including possible delivery methods, toxicity or inhibition effects of concentration, and fate/transport studies. / Master of Science

Dated 1983. Bibliography: leaves 174-181.