Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 124-132). Also available on the World Wide Web.

A number of bacterial species are capable of degrading the widespread environmental pollutant trichloroethylene (TCE) via aerobic cometabolism, but cytotoxic effects that can debilitate the microorganism often accompany this transformation. In this dissertation the effects of TCE degradation on the well-studied, toluene-oxidizing bacterium Burkholderia cepacia G4 were investigated at the physiological and genetic level and compared and contrasted to the effects elicited by several nonhalogenated, short chain alkenes and alkynes. Linear alkynes (C���-C������) were classified as strong mechanism-based inactivators of toluene 2-monooxygenase activity in B. cepacia G4, with 2- and 3-alkynes providing a more potent effect than their 1-alkyne counterparts. The C��� alkyne, acetylene, was weak inactivator of toluene 2-monooxygenase activity presumably because it does not bind efficiently to this oxygenase. Toluene-grown cells of B. cepacia G4 cells oxidized ethylene and propylene to their respective epoxides with no observable effect on cell culturability or general respiratory activity. In contrast, TCE oxidation was accompanied by a myriad of cytotoxic effects. Accumulation of general cellular damage, manifested as a loss of cell culturability and general respiratory activity, outpaced loss of toluene 2-monooxygenase activity during TCE oxidation. Measures of the culturability of TCE-injured cells varied up to 3 orders of magnitude (depending on the method of assessment), and it was found that TCE-injured cells were ultra sensitive to H���O��� on the surface of agar plates. It was proposed that a toxicity threshold exists for B. cepacia G4 during TCE oxidation, and once cells have degraded ���0.5 ��mol of TCE (mg of cells�����) the likelihood of recovery decreases significantly. Tn5 mutants of B. cepacia G4 with disruptions in genes putatively encoding enzymes involved in DNA repair (including UvrB, RuvB, RecA, and RecG) were ultra susceptible to killing by TCE, as well as the known DNA damaging agents, UV light, mitomycin C, and H���O���. Physiological and genetic analysis of the mutants provided suggestive evidence that nucleotide excision repair and recombinational repair activities are linked to the survivability of TCE-injured B. cepacia G4. / Graduation date: 2002

Thesis (Ph. D.)--University of Washington, 2002. / Includes bibliographical references (leaves 225-254).

Thesis (M.S. - Hydrology)--University of Arizona, 1983. / Includes bibliographical references (leaves 82-84).

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.

The industrial solvent trichloroethylene (TCE) is among the most ubiquitous chlorinated compounds found in groundwater pollution. TCE in environment can be removed by physical, chemical and biological procedures. The objective of this pilot-scale study was to apply an enhanced in situ bioremediation technology to remediate TCE-contaminated groundwater. Both aerobic and anaerobic remedial systems were evaluated at a TCE-spill site located in southern Taiwan. In the aerobic test zone, the effectiveness of air, nutrient, and sugarcane molasses injection to enhance the aerobic cometabolism on TCE degradation was evaluated. In the anaerobic test zone, the effectiveness of nutrient and sugarcane molasses injection to enhance the anaerobic reductive dechlorination on TCE degradation was also evaluated. Polymerase chain reaction was applied to analyze the gene variation in TCE-microbial degraders during the treatment process. Results from this study indicate that the aerobic TCE-degraders (type ¢º methanotrophs) and the gene of degradation enzymes (toluene monooxygenase, toluene dioxygenase, particulate methane monooxygenase) were detected after the treatment process in the aerobic test zone. Moreover, TCE concentration dropped from approximately 0.1 mg/L to below 0.05 mg/L in the aerobic test zone after six months of treatment. In the anaerobic treatment zone, Dehalococcoides (anaerobic TCE-degrader) and the gene of degradation enzyme (vcrA) were detected and a significant drop of TCE concentration was also observed. Results reveal that both the aerobic cometabolism and anaerobic dechlorination are feasible and applicable technologies to clean up TCE contaminated aquifers.

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 Washington, 2003. / Vita. Includes bibliographical references (leaves 256-290).

Trichloroethylene (TCE) is a major groundwater contaminant and is a cause of serious health concern. Methanotrophic TCE degradation is very promising compared with other treatments. Methanotrophs produce methane monooxygenases (MMOs) which catalyze methane oxidation and cometabolize chlorinated and aromatic compounds. High rate of TCE degradation is attributed to only soluble MMO (sMMO) expressed mainly by type II methanotrophs under copper-deficient conditions. To make methanotrophic TCE degradation practical, high density methanotrophic biomass with high sMMO activity is required. Methane is the primary substrate for methanotrophs and sufficient quantities must be supplied to support biomass growth. Because of the poor water solubility of methane, mass transfer limitation essentially restricts high biomass production. When methanol was used as the growth substrate, biomass concentration of 7.4 g l-1 Methylosinus trichosporium OB3b was achieved in a 160-h fermentation using an exponential feeding strategy based on pre-determined . Even higher biomass density of 19 and 29 g l-1 biomass were obtained by a modified feeding strategy based on carbon dioxide production. It is concluded that methanol is a promising substrate for the production of large amounts of M. trichosporium OB3bbiomass. In addition, allylthiourea was applied to methanotrophs growth medium to circumvent the inhibitory effect of copper, which inhibits sMMO activity but not particulate MMO (pMMO). We successfully retained sMMO activity by supplementing allylthiourea. Even when M. trichosporium OB3b was grown with 4.5 M copper, which would completely block sMMO expression, addition of 15 M allylthiourea preserved half of the sMMO activity. It was also observed that switching the growth substrate from methane to methanol did not significantly affect sMMO activity. An immobilized soil bioreactor was developed to examine the efficiency of methanotrophic TCE degradation by combining the knowledge obtained on high biomass production and applying allylthiourea for sMMO expression. In a batch TCE degradation experiment, about 63% of TCE was removed in 5.75 h. The maximal TCE degradation rate of 1.40 mg l-1 h-1 was obtained in a continuous TCE degradation at a dilution rate of 0.15 h-1. This study demonstrated the effectiveness of a novel bioreactor system for methanotrophic TCE degradation. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2008-09-30 14:51:26.59