Author ORCID Identifier
Date of Award
Doctor of Philosophy in Environmental Engineering - (Ph.D.)
Civil and Environmental Engineering
Taha F. Marhaba
Carrie A. McDonough
One of the most pertinent challenges faced by the drinking water community is the widespread contamination of per- and polyfluoroalkyl substances (PFAS). These anthropogenic chemicals have been ubiquitously used in everyday products such as carpets, stain repellents, dyes, shampoos, non-stick cookware as well as in aqueous firefighting foams. PFAS are linked with adverse health effects in humans such as thyroid disease, obesity, immunological and reproductive disorders and linked to cancer in adults and low birth weight and developmental defects in infants.
Conventional water treatment technologies have proven to be largely ineffective in PFAS remediation, due to their extreme stability and resistance to degradation. The overall goal of this dissertation is to assess the feasibility and performance of novel destructive technologies in treating PFAS. The specific objectives of this study are to: (i) investigate the impact of water quality and operating parameters on the treatment of a suite of PFAS using two destructive techniques, a) electron beam (e-beam) and b) electrochemical oxidation process (eAOP); (ii) elucidate the primary degradation mechanism of PFAS in these systems; (iii) differentiate the performance (energy requirements) of these systems in treating PFAS isomers; and (iv) develop a novel air-bubbling system to extract PFAS from contaminated soils to combine with destructive technologies via a treatment-train approach. The effect of chain length and functional group is observed while treating PFAS with e-beam technology with the short chain perfluorobutanoic acid and perfluorobutanesulfonic acid showing highest resistance to degradation. This chapter additionally highlights previously unknown degradation pathways of PFAS using a combination of fluorine mass balance and suspect screening. In eAOP system, the composition of supporting electrolyte and anodic voltage did not impact PFAS degradation. PFAS degradation strongly correlates with compound hydrophobicity and this study is the first to differentiate between degradation and loss in concentration due to the phenomena of electrochemical aerosolization of PFAS. Branched PFAS isomers preferentially degrade by e-beam treatment but show comparative/poorer removal in an eAOP system, compared to their linear forms. Soil washing is studied as a removal approach for PFAS-contaminated soils, that can be used as a standalone technique or along with destructive techniques in a treatment train system. A novel air-bubbling assisted soil washing system is used to investigate the removal of adsorbed PFAS from contaminated soils. The extraction efficiency from the soil is found to be inversely proportional to PFAS hydrophobicity, with poorest results observed for long chain perfluorodecanoic acid. Results from this dissertation (i) identify ideal conditions and energy requirements for the destructive removal of PFAS, (ii) highlight the challenges and knowledge gaps for the remediation of contaminated soils, and (iii) provide insight into the variable mechanisms of PFAS destruction and removal, impacted by the PFAS structure and operating parameters in both aqueous and soil matrices.
Londhe, Kaushik Vinaykumar, "Assessing the feasibility and mechanism of destructive removal of per- and polyfluoroalkyl substances (PFAS) from water" (2023). Dissertations. 1717.