<b>Understanding treatment process effects on per- and polyfluoroalkyl substances in the municipal wastewater solids stream</b>

<p dir="ltr">Per- and polyfluoroalkyl substances (PFAS) have garnered increasing environmental concern due to their persistence and potential health risks, particularly as they accumulate in biosolids from wastewater treatment processes leading to further cycling of PFAS in the food web. Wastewater resource recovery facilities (WRRFs) are vital for treating and managing wastewater to protect public health and the environment which has greatly been challenged by the ubiquitous societal use and presence of PFAS. These facilities are essential for removing pollutants and contaminants from wastewater. WRRFs employ various treatment processes, including primary, secondary, and tertiary treatments, to remove pollutants, resulting in treated effluent and solid residues known as biosolids. PFAS presence in biosolids, a residual with beneficial reuse potential, is influenced by influent sources entering our water resource recovery facilities (WRRF), treatment processes, and the overall operational functions of the WRRFs. Understanding these effects is vital for informed decisions in treatment process selection, however, comprehensive studies to date are sparse. This dissertation addresses this issue by first optimizing of a method to successfully analyze PFAS in different types of biosolids with the least time and cost, without compromising the quality. This was followed by conducting a thorough analysis and comparison of methodologies to quantify PFAS in biosolids, assessing extraction solvents, clean-up methods, and injection solvents across various biosolids compositions. Methods studied included ME (methanolic extraction with ENVI-carb cleanup), ME-P (ME with isopropanol modification), U.S. EPA 1633 (involving ME, solid-phase extraction, and ENVI-carb cleanup), and QuEChERS (acid extraction with EMR-lipid and SPE cleanups). The research highlighted ME-P as particularly efficient in time and cost, demonstrating superior performance in handling diverse biosolid matrices, especially through intriguing the final injection vial preparation. Detailed analysis of sequential extractions revealed that approximately 75% of the total PFAS content was extracted in the first extraction.</p><p dir="ltr">The ME-P method was applied to investigate PFAS dynamics within the solids stream processes in treatment of wastewater, specifically anaerobic digestion (AD), thermal hydrolysis (THP), autothermal thermophilic aerobic digestion (ATAD) and storage nitrification-denitrification reactor (SNDR). These processes significantly influenced PFAS profiles by altering the relative concentrations of precursor and intermediate PFAS such as di-substituted polyfluoroalkyl phosphate esters (diPAPs) and fluorotelomer carboxylic acids (FTCAs). THP, when combined with AD, showed enhanced degradation of PFAS, particularly decreasing diPAPs and increasing PFCAs, underscoring its potential for improving PFAS removal efficiency in treatment facilities. Analysis of the ATAD and SNDR treatments revealed complex changes in PFAS classes, with notable increases in perfluoroalkyl alkyl acids (PFAAs) and varying impacts on phosphorus-containing PFAS and FTCAs. This dynamic analysis underscores the role of treatment conditions in shaping PFAS fate and concentrations within wastewater solids streams.</p><p dir="ltr">This research has provided valuable insights into how PFAS entering our WRRFs are altered through the various treatment processes, thus impacting the PFAS distribution in the final biosolids often land-applied for their carbon and nutrient value. Findings will contribute to optimizing PFAS management strategies at WRRFs, facilitating informed decision-making for effective treatment and disposal or reuse of biosolids. This holistic approach not only enhances our understanding of PFAS behavior in wastewater treatment but also underscores the importance of tailored methodologies and treatment processes to mitigate environmental impacts effectively.</p>