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SUBMITTED DISSERTATION 09092019.pdf (7.03 MB)

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Degradation of Halogenated Hydrocarbons by Zero-Valent Magnesium and Copper/Magnesium Bimetallic Reductant, & Characterization of Poly- and Perfluoroalkyl Substances in Treated Wastewater Reclaimed for Direct Potable Reuse

Wang, Bo
http://rave.ohiolink.edu/etdc/view?acc_num=wright1568048522860247

Abstract Details

2019, Doctor of Philosophy (PhD), Wright State University, Environmental Sciences PhD.
Chlorinated hydrocarbons (CHCs) in groundwater can be treated by monometallic and bimetallic metal reductants through abiotic degradation. The breakdown of CHCs is achieved by gaining electrons from those reductants and removing chlorines from CHC molecules to transform the CHCs into less chlorinated compounds. This study explored the abiotic degradation of selected CHCs by zero valent magnesium Mg0 and bimetallic Cu/Mg reductant. Results showed that zero valent Mg0 was not effective in the treatment of carbon tetrachloride (CT), chloroform (CF) and dichloromethane (DCM). In contrast, the presence of Cu in Cu/Mg bimetallic reductant significantly accelerated the degradation kinetics. Degradation kinetics were observed to decrease with time, perhaps due to particle aging. The effect of Cu loading on degradation of the above compounds was also evaluated. Increasing Cu loading yielded faster degradation rates. No significant effect of Cu loading on the extent of CHC degradation was observed. CF degradation with Cu/Mg was promoted by acidic conditions. Methane (CH4), a desirable end product, was only formed as the major byproduct in CT and CF degradation by Cu/Mg bimetallic reductant. The higher yield of CH4 from CT or CF indicated that the complete reduction pathway was more significant compared with the hydrogenolysis pathway in degradation by Cu/Mg bi-metallic reductant. Instead of relying solely on surface water or groundwater sources, potable reuse of treated wastewater is becoming an increasingly common option for bolstering water resource portfolios in water-scarce regions. However, the concern over emerging trace contaminants that persist through wastewater treatment needs to be addressed to evaluate the potential risks of wastewater reuse. Poly- and perfluoroalkyl substances (PFASs) are used in a wide range of industrial and commercial applications, and are emerging contaminants posing a threat to safe drinking water. The information about their presence in reclaimed water for potable reuse is quite limited. In the present study, in order to evaluate the removal efficiency of selected PFAS residues during wastewater treatment, PFAS occurrence in the treatment plant influent and effluent was characterized at 3 wastewater treatment plants in West Texas that are intended to produce effluent suitable for potable reuse. These wastewater treatment plants (WWTPs) already are or are planning to construct direct potable reuse (DPR) facilities intended to treat wastewater to a level where the effluent would be suitable for use as a drinking water source without an environmental buffer. This study only evaluates the efficiency of wastewater treatment processes to remove PFASs in the WWTP before the water is sent to a DPR facility and subsequently to a drinking water treatment plant for further/advanced treatment. The results showed that perfluorinated sulfonic acids (PFSAs) were the largest contributor to the total PFAS concentrations in the influents and effluents of the WWTPs. Among PFSAs, perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonate (PFHS) were the predominant compounds. The average total PFAS concentrations in selected WWTPs were 50 (± 125) - 514 (± 328) ng/L in influents and 31(± 2) – 59 (± 24) ng/L in effluents (WWTP #1), 52 (± 2) - 295 (± 121) ng/L in influents and 54 (± 45) – 323 (±190) ng/L in effluents (WWTP #2), 278 (± 8) - 674 (± 166) ng/L in influents and 166 - 682 (± 160) ng/L in effluents (WWTP #3) throughout the year. Since PFOS based products were phased out by 3M company in 2002, perfluorobutane sulfonate (PFBS) has come in use in various applications as a PFOS substitute However, the detection of elevated concentrations of PFOS, PFHS and PFBS in the wastewater in this study, indicates that these PFSAs and their precursors are still in use. The distribution pattern of PFASs was heavily impacted by the influent wastewater characteristics. Due to these variabilities, no generalizations can be made regarding the efficiency of WWTPs to remove PFASs, but clearly WWTP effluent entering a DPR facility will potentially contain significant concentrations of PFAS. The data provided in this study will be a valuable resource that can be used in designing DPR treatment processes and evaluating the potential risks of consuming DPR-produced drinking water.
Abinash Agrawal, Ph.D. (Advisor)
David F. Dominic, Ph.D. (Committee Member)
David Kempisty, Ph.D. (Committee Member)
Marc A. Mills, Ph.D. (Committee Member)
Mark N. Goltz, Ph.D. (Committee Member)
202 p.
Environmental Science
Chlorinated hydrocarbons; CHCs; groundwater; abiotic degradation; zero valent magnesium; Mg0; bimetallic Cu Mg reductant; degradation; degradation kinetics; potable reuse of treated wastewater; wastewater reuse; PFAS residue; direct potable reuse facility

Recommended Citations

Citations

  • Wang, B. (2019). Degradation of Halogenated Hydrocarbons by Zero-Valent Magnesium and Copper/Magnesium Bimetallic Reductant, & Characterization of Poly- and Perfluoroalkyl Substances in Treated Wastewater Reclaimed for Direct Potable Reuse [Doctoral dissertation, Wright State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=wright1568048522860247

    APA Style (7th edition)

  • Wang, Bo. Degradation of Halogenated Hydrocarbons by Zero-Valent Magnesium and Copper/Magnesium Bimetallic Reductant, & Characterization of Poly- and Perfluoroalkyl Substances in Treated Wastewater Reclaimed for Direct Potable Reuse. 2019. Wright State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=wright1568048522860247.

    MLA Style (8th edition)

  • Wang, Bo. "Degradation of Halogenated Hydrocarbons by Zero-Valent Magnesium and Copper/Magnesium Bimetallic Reductant, & Characterization of Poly- and Perfluoroalkyl Substances in Treated Wastewater Reclaimed for Direct Potable Reuse." Doctoral dissertation, Wright State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1568048522860247

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Wright State University and OhioLINK.