Date of Award
December 2020
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Environmental Engineering and Earth Sciences
Committee Member
Kevin T. Finneran
Committee Member
David L. Freedman
Committee Member
Brian A. Powell
Abstract
Contaminants pose a serious concern due to their relative ease of transport through groundwater, where they can accumulate and become a plume (i.e. dissolved contaminants that move with groundwater flow). Chlorinated solvents are contaminants of concern due to their potential for causing cancer, organ disease, and other ailments. Due to improper storage and disposal, these solvents find themselves in groundwater reserves, and thus warrant the need for finding treatment options to remove them from the water. In-situ biodegradation of TCE is a respiratory process consisting of electron donors, acceptors, and microorganisms that are either native or introduced into the system. Energy from the oxidation of electron donors by microorganisms is coupled to the reduction of TCE and its daughter products (referred to as “reductive dechlorination”). The focus of the research is to investigate a new technology, in-situ activated carbon, and its ability to act as both an adsorbent, for attracting the contaminants and the bacteria onto itself, and as a bridge for easier transfer of electrons between the microorganisms and chlorinated compounds.
Experiments consisting of 11 batches of triplicates with two different electron donors, and three different activated carbon mass loadings. Each electron donor, namely emulsified oil substrate (EOS), which is a soybean oil-based electron donor, and a mixture of acetate-lactate, was evaluated with the three mass loadings. The mass loadings of activated carbon used in the experiments were a high mass loading of 78 mg/mL, a medium mass loading of 26 mg/mL, and a low mass loading of 1 mg/mL. The two higher mass loadings were based on vendor recommendations. The remaining batches were control batches consisting of activated carbon unamended batches, batches unamended with electron donors, and a sterile batch. A gas chromatograph was used for analyzing the headspace samples of the batches to detect the amount of TCE, its daughter products, and methane present denoted as μmole/bottle.
Results from the batch experiment demonstrated that the activated carbon unamended batch and the 1mg/mL batch, both amended with the acetate-lactate mixture, had the most amount of ethene recovered in comparison to other batches. The batch with 1 mg/mL of GAC demonstrated ethene being generated earlier than the GAC unamended batch. However, the 1 mg/mL of GAC batch also generated extremely high amounts of methane in the system. The No GAC control batch had the highest ethene recovery, followed by the 1 mg/mL of GAC batch. The batches with the higher GAC mass loads did not have any ethene during the entire period, but this could have been a function of ethene adsorption to the extreme GAC mass loadings despite its limited adsorption capacity. A separate enrichment experiment was conducted using bacteria from these two batches, No GAC control and 1 mg/mL GAC batches, where the inoculum from both batches was subjected to a GAC amended and GAC unamended environments, with acetate-lactate as the electron donor. The enrichments amended with inoculum from the 1 mg/mL GAC batch had more ethene recovered at the end of the incubation period, with the GAC unamended enrichment recovering more ethene than the GAC amended enrichment. The GAC amended enrichment from this same batch generated the largest amount of methane among all the enrichments.
Recommended Citation
Harigovind, Sreedhar, "The Effect of In-Situ Activated Carbon on Biodegradation of TCE" (2020). All Theses. 3434.
https://tigerprints.clemson.edu/all_theses/3434