School of Civil and Environmental Engineering
Ph.D. Thesis Defense Announcement
The Minus Approach to Redefine the Standard of Practice of Drinking Water Treatment: Philosophy and Case Studies on the Adsorption of Per- and Polyfluoroalkyl Substances onto Powder Activated Carbon and Membrane Surfaces
By: Elliot Mark Stuart Reid
Advisors: Dr. Yongsheng Chen and Dr. Ching-Hua Huang
Committee Members: Dr. Xing Xie (CEE), Dr. Katherine Graham (CEE), Dr. Shane Snyder (CEE), Dr. Qingguo Huang (Crop and Soil Sciences, University of Georgia)
Date and Time: April 14, 2025 – 4-6 PM
Location: Price Gilbert Library 4222
Zoom: Zoom Link / Passcode = 961526
Victorian-aged water treatment practices that rely on chemical additions to remove contaminants (i.e., “Plus Approaches”) are ineffective at removing many known, unknown, and emerging contaminants (KUECs) and also create toxic disinfection byproducts (DBPs) in-situ. Although finished drinking water is usually compliant with permitting standards, numerous questions arise regarding its ultimate safety for human consumption. This thesis introduces the philosophy of the “Minus Approach,” a toolbox of practices and technologies to mitigate KUECs and DBPs in drinking water while also producing biologically stable water containing pathogens at levels having negligible human health risk. We describe how the Minus Approach contrasts with the Plus Approach and can ultimately change the standard of practice of drinking water treatment.
Adsorption is a fundamental Minus Approach technology to bolster overall water quality. Herein, a commercially available powder activated carbon (PAC) is pyrolyzed to amplify its hydrophobicity and encourage greater adsorption metrics of per- and polyfluoroalkyl substances (PFAS), which are key chemical targets of the Minus Approach. We perform a comprehensive examination of adsorbent surface chemistry and morphology. Adsorption isotherms, kinetic studies, and a mixed PFAS removal test are conducted to evaluate performance of the hydrophobically improved PAC compared to its precursors. A density functional theory (DFT) calculation is performed to quantitatively evaluate the adsorption energies of PFAS onto a graphene skeleton containing different organic functional groups at differing concentrations in order to further validate experimental results.
Inadvertent PFAS adsorption onto membrane materials can result in concentration underestimations. Herein, we report on the adsorption of six different PFAS onto eleven syringe filters, differing in either manufacturer, polymer material, diameter, and/or pore size under various experimental conditions. We perform comprehensive materials characterization, exhibiting differences in morphology and surface roughness, area, and charge. Evaluation of post-filtration PFAS recovery demonstrated significant impacts of filter material and surface area, initial PFAS concentration, pH, and the co-occurrence of cations and anions. Machine learning predictions of Abraham’s solute descriptors were used to develop qualitative hypotheses describing the forces governing PFAS adsorption onto different materials.