University of New Hampshire
Elham Tavasoli is a Ph.D student at the University of New Hampshire, studying Environmental Engineering under supervision of Dr. Pula Mouser. She is in her second year of studies, focusing on per-and polyfluorinated alkyl substances (PFAS) as a major class of contaminants of emerging concern (CEC). She is investigating PFAS distribution, fate, and their degradability in wastewater treatment facilities.
Distribution and Fate of Per- and Polyfluorinated Alkyl Substances (PFAS) in Wastewater Treatment Plants with Different Biological Treatment
Anthropogenic compounds known as per-and polyfluorinated alkyl substances (PFAS) represent a major class of contaminants of emerging concern (CEC) composed of more than 3000 human-made chemicals. PFAS widespread use, broad environmental distribution, recalcitrance in the environment, and potential toxicity to humans and ecosystems have resulted in the considerable growing concern. PFAS are well known to be moderately toxic to marine and freshwater aquatic organisms, can bioaccumulate and pose human and ecological health concerns. Wastewater treatment facilities (WWTFs) are a continued source of PFAS to surface waters because of their direct tie to common household products and related industrial, municipal, and firefighting wastewater discharges. This study investigated the distribution and removal efficiency of twenty-four PFAS within six New Hampshire WWTFs that apply different biological and disinfection unit processes. PFAS quantification was conducted using two approaches: (1) direct LC-MS/MS analysis of 24 known compounds and (2) a total oxidizable precursor assay (TOP Assay) followed by LC-MS/MS to determine the total potential PFAS concentration. The TOP Assay uses a strong chemical oxidizing agent to convert larger fluorinated precursor compounds (for which no analytical standards exist) into their terminal end products that can be quantified by the 24-PFAS method. Therefore, TOP Assay expands our limited compound specific analytical techniques by providing an overall quantifiable estimate of all likely PFAS present. Of the 24 PFAS analyzed using LC-MS/MS, up to 7 were detected in WWTF influents while up to 11 were detected in effluents. Three of five measured precursors were detected in influent. When the TOP Assay was applied, up to 15 PFAS were detected in WWTF influents while up to 13 compounds were in effluents, confirming the presence of non-targeted PFAS precursors in WWTFs. PFAS concentrations measured using the TOP Assay ranged from 170 to 6400 ng/l in influents and 140 to 370 ng/l in effluents. Removal efficiency between influent and effluent varied from 4% to 95% across the WWTFs, with the highest removal associated with longer retention time and combination of aerobic and anaerobic zones in biological process. The major detected PFAS compounds were short and long-chain constituents of perfluoroalkyl carboxylic asides (PFCA) (e.g., perfluorohexanoic acid (PFHxA)), and perfluorooctanoic acid (PFOA). The continued detection of long chain PFAS after their phase out in the early 2000s combined with the variable removal efficiency of PFAS in the studied WWTFs highlights the need to better characterize unit processes influencing PFAS fate in WWTF, including discharge rates and loadings to receiving water bodies.