Date of Award

8-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Environmental Engineering and Science

Advisor

Freedman, David L

Committee Member

Finneran, Kevin T

Committee Member

Carraway, Elizabeth R

Abstract

Groundwater contaminants at an industrial site in South Carolina include tetrachloroethene (PCE), trichloroethene (TCE), cis-1,2-dichloroethene (cDCE), vinyl chloride (VC), 1,2,4-trichlorobenzene (1,2,4-TCB), 1,2-dichlorobenzene (1,2-DCB), 1,4-dichlorobenzene (1,4-DCB), chlorobenzene (CB), and benzene. The source areas at the site include a tank farm area, a grease trap area, the former wastewater lagoons (WWTP) and the former oil retention pond (ORP). A microcosm evaluation was preformed to determine the potential for bioremediation to treat the organic contaminants in the four source areas (within the saturated zone) and in a downgradient portion of the groundwater plume. The objectives were to evaluate 1) anaerobic treatment at the source zones using biostimulation with lactate or emulsified vegetable oil; 2) bioaugmentation with a commercial chloroethene respiring culture; and 3) addition of zero valent iron (ZVI) with lactate. Additional microcosms were prepared using the same conditions and initially incubated anaerobically; these were then converted to aerobic conditions after the chlorinated ethenes were consumed. Controls included anaerobic conditions without amendments, aerobic conditions without amendments, water controls, and autoclaved controls. For the downgradient groundwater microcosms, the same treatments were used except for the two sets with ZVI. Triplicate bottles were prepared for each treatment, resulting in a total of 147 microcosms. Based on observations made during approximately 400 days of monitoring, the following conclusions were reached: Sequential anaerobic/aerobic bioremediation is a viable treatment approach for the WWTP, ORP, and downgradient locations. PCE and TCE can be efficiently dechlorinated to ethene under anaerobic conditions and the aromatic compounds can be oxidized under subsequent aerobic conditions. It is feasible to use only anaerobic biostimulation to remove PCE and TCE for the WWTP and ORP locations, whereas bioaugmentation will be required for the downgradient location. Consideration should also be given to using bioaugmentation for the WWTP and ORP locations, as this will accelerate removal of PCE and TCE so that a switch to aerobic conditions can occur more quickly. There was no compelling evidence in support of anaerobic biodegradation of the aromatic compounds, either via reductive dechlorination to benzene or via anaerobic oxidation. However, aerobic biodegradation of the aromatic compounds is feasible for the WWTP, ORP, and downgradient locations. Development of an aerobic enrichment culture for biodegradation of the aromatic contaminants at the WWTP, ORP and downgradient locations is advisable. Aerobic aromatic degraders are present at the WWTP. Groundwater from this location can be used to develop an indigenous bioaugmentation culture. The process of enrichment can either be done in an on-site reactor or by an off-site vendor. Bioaugmentation with an aerobic enrichment culture will significantly improve the rate of aerobic treatment of the aromatic compounds at the WWTP, ORP and downgradient locations. • Without additional evaluation, bioremediation alone is not feasible for the tank farm and grease trap locations. ZVI shows promise for treating the PCE and TCE, although additional study is warranted to find an appropriate dose. Also, additional studies are needed to ascertain if aerobic biological treatment would be feasible to address the aromatic compounds following ZVI treatment of PCE and TCE. • 1,2,4-TCB is at least partially responsible for the lack of PCE and TCE reductive dechlorination in the grease trap microcosms. This conclusion is based on the inhibition test, which showed that the presence of high concentrations of 1,2,4-TCB inhibited KB-1. Further experiments should conducted to determine the effectiveness of aerobic removal of aromatics, specifically 1,2,4-TCB, followed by anaerobic treatment.

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Engineering Commons

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