Analytical protocol for detection and prioritization of per- and polyfluoroalkyl substances (PFAS) in biosolid leachates

Land application of biosolids from wastewater treatment plants (WWTPs) can potentially release per- and polyfluoroalkyl substances (PFAS) into the environment. Limited data is available on PFAS types and levels in biosolids from South Florida. This study outlines analytical protocols for detecting and quantifying PFAS in biosolid leachate and solid residue, by modifying and validating a method based on the U.S. EPA Method 1633. The method achieved detection limits as low as 0.02 ng/L in leachate and 0.01 ng/g in the biosolid residues and was applied to samples from two Miami-Dade WWTPs, in which 22 of 40 targeted PFAS were detected in leachates and 19 in solid residues after leaching. Distinct PFAS composition and levels were observed among the WWTPs, whereas the sum of PFAS (∑ 22 PFAS) in leachates ranged from 57 to 463 ng/L, and in the solid residue ∑ 19 PFAS ranged from 187 to 571 ng/g. The 5:3 Fluorotelomer carboxylic acid (5:3 FTCA) was the most prevalent and abundant PFAS found, with a detection frequency between 83 % and 100 %. Key PFAS were prioritized based on their concentration and detection frequency. These findings highlight PFAS occurrence and distribution in biosolids at different treatment stages, underscoring the need for further monitoring and regulation.