Date of Award
Master of Science (MS)
Environmental Engineering and Earth Science
Dr. Kevin Finneran
Dr. David Freedman
Dr. Cindy Lee
TCE is currently remediated using physical methods like air stripping and granular activated carbon adsorption. While physical and chemical processes work on a site-specific basis, biological strategies have been favored as they are economical and reliable. The objective of this work was to determine the feasibility of using palm oil as an electron donor in the reductive dechlorination of TCE to ethene. Palm oil was considered for the study because it is locally grown in many parts of the world. The palm oil that does not meet the industry standards is discarded. Despite the environmental impacts caused by the palm oil industry as a whole, the utilization of discarded palm oil for bioremediation will be cost-effective. It is a slow fermenting substrate that is known to inhibit methanogenesis.
Two of the three objectives were to determine if palm oil serves as an electron donor for the reduction of TCE and to compare the performance with other common electron donors like Acetate-lactate mixture and EOS and to evaluate the methane generated by each of the donors during the process. The batch experiments demonstrated that palm oil promoted the complete reduction of TCE to ethene with minimal methane production when compared to the other electron donors tested. The amount of methane produced in the bottles with Emulsified Oil Substrates (EOS) and palm oil is less than in those with the acetate-lactate mixture. The paucity of methane observed is likely due to the accumulation of long-chain fatty acids (LCFA), mainly palmitic acid, during the fermentation of the electron donor, which inhibits methanogenesis. When carrying out in situ bioremediation, the generated methane accumulates in the aquifer and may escape if water reaches the surface or if the aquifer is shallow. If methane escapes to the environment, it causes adverse effects as it is a greenhouse gas. Thus, the aim of the research is to see if palm oil can promote quick reductive dechlorination of TCE ultimately to ethene with minimal methane production. The other objective of my work was to investigate the effect of adding exactly the stoichiometric need of electron donor and excess electron donor on the TCE degradation rate. Based on the current and past studies by Wei & Finneran, I inferred that adding excessive electron donors, as opposed to the stoichiometric need, does not speed up the reductive dechlorination process but allows other microbial processes to compete for electrons. Adding the stoichiometric requirement is beneficial as the low partial pressure of hydrogen gives a competitive advantage for the dechlorinators over the methanogens. The techno-economic analysis based on the experimental data also demonstrated that palm oil is an economical option when compared to the other electron donors considered for the experiment. Thus overall, palm oil can be used as an efficient and economical alternative for the existing electron donors available in the industry.
Swamy, Shivani, "The Effect of Using Palm Oil as an Electron Donor for the Reductive Dechlorination of Trichloroethylene (TCE)" (2021). All Theses. 3697.