Date of Award
5-2024
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Environmental Engineering and Science
Committee Chair/Advisor
Dr. David L. Freedman
Committee Member
Dr. Kevin T. Finneran
Committee Member
Dr. Sudeep C. Popat
Abstract
At the Lane Street Groundwater Contamination Superfund site in Elkhart, Indiana, which includes industrial, commercial, and residential properties, a plume of contaminated groundwater was identified that requires remediation. The plume is chiefly composed of trichloroethylene (TCE) and has impacted residents’ drinking water. A microcosm study was performed to evaluate the potential of various treatment methods to remediate the Lane Street Superfund Site groundwater. The objectives of this microcosm study are to evaluate the potential for biostimulation, bioaugmentation, and abiotic degradation for implementation at this Site and to evaluate toxicity factors that have precluded natural degradation of the site contaminants. The microbiological community within the microcosms was analyzed at the beginning and end of the experiment to evaluate the impacts of each treatment. Anaerobic microcosms were constructed with aquifer sediment and groundwater from the Site. The microcosms were amended with combinations of lactate, emulsified vegetable oil (EVO), microscale zero-valent iron (ZVI), sulfidated microscale ZVI, activated carbon, and a commercial bioaugmentation culture with Dehalococcoides (Dhc).
Bioaugmented microcosms amended with Dhc revealed the highest dechlorination rates among the treatment options. Bioaugmentation lowered the methane production and demand for electron donor and completely reduced TCE to ethene. There were no signs of inhibition due to toxicity factors in the bioaugmented microcosms. Two of the three lactate amended microcosms revealed complete dechlorination activity of TCE despite initial concentrations of dechlorinating microbes, specifically Dhc, below detection. Compared to the bioaugmented treatment, the lactate amended microcosms showed less consistent rates of dechlorination and vinyl chloride (VC) accumulation reaching stoichiometric levels. The EVO amended microcosms did not demonstrate the same dechlorinating activity as the lactate amended microcosms, which suggests that the fermenters required for long-chain fatty acids were absent.
Microcosms amended with microscale ZVI powder reduced the concentration of TCE at a first-order rate, in proportion to the dose of ZVI. However, by the end of the incubation period, the concentration of TCE persisted above the clean-up goal. Sulfidated-ZVI completely reduced TCE to ethene in a shorter time than the powder ZVI. VC accumulation was not observed with either of the ZVI products evaluated. Activated carbon rapidly adsorbed the TCE but showed no appreciable dechlorination activity.
The lactate amended microcosms revealed the presence of Dhc, despite initial levels of dechlorinating microbes being below detection. The lactate amended microcosms consisted primarily of tceA reductase (tceA) genes, compared to the bioaugmented microcosms which contained a larger percentage of vinyl chloride reductase (vcr) and BAV1 vinyl chloride reductase (bvc) genes. Dhc and Dehalogenimonas (Dhgm) were below detection in the unamended, EVO amended, and ZVI and EVO amended microcosms, which exhibited limited biological reductive dechlorination. These results reiterate the importance and value of microcosm studies when evaluating remediation methods to implement at a contaminated site.
The results of this microcosm study suggest that bioaugmentation has notable advantages as a treatment alternative over biostimulation or activated carbon. ZVI powder and sulfidated-ZVI were also effective treatment methods and reduced TCE to ethene without accumulating VC. Additional considerations, especially regarding cost, will need to be considered before arriving at a final recommendation for remediation of the Lane Street Superfund Site.
Recommended Citation
Costello, Alyssa, "Laboratory Evaluation of Remediation Alternatives for Groundwater at the Lane Street Superfund Site" (2024). All Theses. 4250.
https://open.clemson.edu/all_theses/4250