Date of Award

Spring 2020

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

Paula Mouser

Second Advisor

James Malley

Third Advisor

Jenna Luek

Abstract

Per-and polyfluoroalkyl substances (PFAS) represent a major class of emerging contaminants composed of nearly 5000 human-made chemicals. PFAS have been used since the 1950s as surfactants in industrial and consumer products due to their unique water and oil repellency, high surface activity, and thermostability. These compounds can bioaccumulate and pose human and ecological health concerns; for example, PFAS intensive exposure can affect the liver, reproduction and development in humans and wildlife. Ubiquitous presence of these compounds in different environmental matrices, high persistency, and potential threats to human and environmental health, have made it critical to develop an understanding of how they are distributed in different matrices and how people get exposed. Previous studies have provided some understanding of how environmental conditions, chemical structures and properties affect PFAS distribution, fate, and their biotransformation. In addition, PFAS environmental exposure studies have been completed or are underway; and while it is clear that exposures are occurring, the effects associated with exposure are not fully understood and therefore there is significant uncertainty associated with evaluation of risks associated with PFAS in environment. Wastewater treatment facilities (WWTFs) are a conduit of PFAS which are not originally designed for the removal of these low level and diverse contaminants. In this study, PFAS distribution and fate in six WWTFs discharging their effluent into Great Bay Estuary in March and July 2019 were investigated. PFAS were detected in influent and effluent of WWTFs with up to 12 detected constituents out of 24 measured by standard analytical method (LC/MS/MS). In general, PFAS concentrations increased in effluent after biological treatment which supports the presence of unknown PFAS precursors in influent not measured during standard analytical method. Seasonal changes exhibited a significant influence on PFAS concentrations in effluent. Higher PFAS concentrations were detected in the warmer season, indicating the effect of temperature and higher microbial activities on PFAS precursor degradation. In addition, PFAS precursors were indirectly quantified by oxidizing precursors into terminal PFAAs compounds using the total oxidizable precursor assay (TOP assay). Higher perfluoroalkyl acids (PFAA) concentrations after oxidation compared to unoxidized samples confirmed the presence of PFAS precursors in WWTFs.

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