Available at: https://digitalcommons.calpoly.edu/theses/3211
Date of Award
12-2025
Degree Name
MS in Civil and Environmental Engineering
Department/Program
Civil and Environmental Engineering
College
College of Engineering
Advisor
Derek Manheim
Advisor Department
Civil and Environmental Engineering
Advisor College
College of Engineering
Abstract
Per- and poly-fluoroalkyl substances (PFAS) are persistent contaminants that move through municipal and industrial wastewater systems with limited attenuation. As a result, they are increasingly detected in drinking water supplies. Despite growing regulatory concern, a systems-level understanding of PFAS behavior across multiple treatment facilities and watershed settings remains incomplete. This study compiled influent, effluent, and biosolids datasets from more than one hundred California wastewater treatment plants to evaluate PFAS occurrence, transformation, and partitioning across diverse treatment configurations. Analytical steps included calculating removal efficiencies, assessing precursor-to-product oxidation, evaluating co-contaminant correlations, and grouping facilities by process design to quantify configuration-specific fate patterns. Results show that apparent “removal” is dominated by solids-associated partitioning and specific biotransformation pathways: long-chain PFAS preferentially sorb to biosolids, while short-chain acids persist in effluent due to higher solubility, weak hydrophobic interactions, and low affinity for organic matter. Negative removal efficiencies provide evidence of in-plant oxidation of fluorotelomer and sulfonamido precursors to terminal perfluoroalkyl acids. Statistically significant correlations with divalent cations and TSS support ionic and solids-mediated controls on PFAS attenuation rather than biological degradation. Advanced treatment processes such as GAC, IX, and RO achieve high long-chain PFAS removal but concentrate PFAS into waste residuals requiring destruction. Collectively, these findings show that wastewater treatment plants function as reactive conduits that redistribute PFAS rather than eliminate them, underscoring the need for integrated treatment processes, waste residuals management, and precursor-focused monitoring to safeguard drinking water resources.