Date of Award

Fall 2026

Abstract

The occurrence of per- and polyfluoroalkyl substances (PFAS) has been widely studied in point source discharges to surface water bodies, such as municipal wastewater treatment facilities. However, little is known about the occurrence and fate of these compounds in non-point sources, such as onsite wastewater treatment systems (septic systems). This research investigated differences between PFAS occurrence in septic systems and municipal wastewater systems in New Hampshire. It also characterized seasonal dynamics of PFAS in community septic systems and investigated the role of nitrification and denitrification processes on PFAS transformations in conjunction with microbial communities and functional genes involved in both ammonium and methane oxidation. Study sites included two community septic systems in southern New Hampshire designed for enhanced nutrient removal of onsite wastewater. The septic system with higher effluent PFAS and dissolved oxygen >5 mg/l was abundant in Nitrosomonas, bacterial genera associated with nitrification using ammonium monooxygenase enzymes (amoA/amoB/amoC). Conversely, the septic system with suboxic conditions (DO < 3.2 mg/L) had few Nitrosomonas and more bacterial genera associated with denitrification and methane oxidation, with little change in PFAS despite clear denitrification occurrence. This data highlights the important role nitrogen removal and particularly nitrifiers may play in PFAS precursor transformation, and suggests that operational parameters (e.g., dissolved oxygen levels, recirculation ratios) and ammonium and methane oxidation pathways may influence PFAS discharge from septic systems.

Document Type

Master's Thesis

First Advisor

Paula J Mouser

Second Advisor

James P Malley Jr.

Department or Program

Civil and Environmental Engineering

Degree Name

Master of Science

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Available for download on Monday, April 12, 2027

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