Date of Award

7-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Environmental Engineering

Advisor

Freedman, David L

Committee Member

Finneran, Kevin T

Committee Member

Carraway, Elizabeth R

Abstract

1,4-Dioxane is an emerging groundwater contaminant and probable human carcinogen with considerable potential remediation costs due to its hydrophilic and recalcitrant nature. Commonly occurring with 1,1,1-trichloroethane (1,1,1-TCA) plumes due to its application as a solvent stabilizer, 1,4-dioxane is also used in industrial lubricants and occurs as an impurity in numerous personal care products. Current treatment strategies to treat dioxane contamination include advanced oxidation processes and biological treatment, though only aerobic paths of biodegradation are currently understood. Laboratory and field studies have indicated the possible inhibitory effects of 1,1,1-TCA and its abiotically transformed daughter product, 1,1-dichloroethene (1,1-DCE) on the aerobic biodegradation of 1,4-dioxane. The goal of this research was to evaluate the biodegradability of 1,4-dioxane in a variety of redox environments. The aerobic biodegradation of dioxane has been characterized in both laboratory and field studies, yet anaerobic processes related to this compound are poorly understood. The specific goals of this microcosm study were to evaluate: 1) anaerobic biodegradation of 1,4-dioxane in microcosms prepared with soil and groundwater amended with Fe(III), Fe(III)-ethylenediaminetetraacetic acid (EDTA), Fe(III)-EDTA + inoculum with samples from current microcosms that exhibit the highest level of 1,4-dioxane transformation, Fe(III) + anthraquinone-2,6-disulfonate (AQDS), and sulfate; 2) anaerobic biodegradation of 1,4-dioxane in microcosms prepared with soil and mineral salts medium amended with nitrate, Fe(III)-EDTA, and sulfate; 3) aerobic cometabolism of 1,4-dioxane by indigenous propanotrophs and by bioaugmentation with a mixed culture of propanotrophs; 4) the effect of 1,1-DCE on aerobic cometabolism of 1,4-dioxane by propanotrophs; 5) the potential for sequential anaerobic dechlorination of 1,1-DCE to ethene followed by aerobic cometabolic biodegradation with propanotrophs; and 6) the presence of indigenous aerobic microbes capable of biodegrading 1,4-dioxane as their sole source of carbon and energy. The results of this research showed that: 1) 1,4-dioxane is recalcitrant under all anaerobic environment in which it acts as the sole electron donor; 2) the addition of readily degradable substrates may stimulate the biodegradation of 1,4-dioxane in sulfate, nitrate, and ferric iron reducing conditions, although the only ferric iron amended bottles that showed the possibility of 1,4-dioxane disappearance also contained a humic acid analog; 3) 1,4-dioxane is readily degraded to concentrations below 25 µg/L in aerobic environments in the presence of propanotrophs; 4) the mixed propanotroph culture, ENV487, is greatly inhibited by the presence of low concentrations of 1,1-DCE; 5) utilizing reductive dechlorinating bacteria to biodegrade 1,1-DCE to ethane prior to the establishment of aerobic conditions allows the cometabolic activity of ENV487 to proceed uninhibited, and; 6) bacteria capable of utilizing 1,4-dioxane as a sole source of energy and carbon occur in aerobic environments and are readily grown in a laboratory setting.

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Engineering Commons

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