Perfluoroalkyl, fluorotelomer sulfonate, and perfluorooctane sulfonamide contamination in biosolids: Composition, co-contamination and re-use implication
By Julie A. Sleep & Albert L. Juhasz
Env. Poll.
July 13, 2020
DOI: 10.1016/j.envpol.2020.115120
In this study, biosolids from 12 waste water treatment plants across Australia were analysed to quantify the concentration of 28 per- and polyfluoroalkyl substances (PFAS). PFAS concentration varied significantly between locations (5.4–150 μg kg-1) while perfluorooctane sulfonic acid (PFOS) was the predominant analyte in 9 of 12 biosolid samples (4.7–86 μg kg-1) contributing 17–93% to the total PFAS concentration. However, in WWTP2 and WWTP10, PFAS composition differed significantly, with fluorotelomer sulfonic acids (FTSAs) and perfluorooctane sulfonamide-based substances (FOSAMs), precursor compounds of restricted PFAS, contributing significantly to Σ28 PFAS concentration. Five additional biosolid samples from historical stockpiles of varying ages located at WWTP3 were analysed to assess changes in Σ28 PFAS concentration with biosolid age (10–50 years). While temporal trends in Σ28 PFAS or individual PFAS concentration were not observed, a strong negative correlation was observed between pH and Σ28 PFAS concentration over a pH range of 4.1–6.6. Three samples (WWTP2, 3 and 10) were selected for further analysis using the total oxidisable precursor (TOP) assay to provide insights into the potential impact of oxidative transformation on individual PFAS concentration. Treatment with persulfate resulted in the decrease of 6:2 and 8:2 FTS (WWTP2), MeFOSE (WWTP2 and 3), EtFOSE (WWTP2), MeFOSAA (WWTP2, 3, 10) and EtFOSAA (WWTP2, 3, 10) with an increase in C4–C9 PFCAs (1–232 μg kg-1), while changes in PFSA concentrations were negligible (<7 μg kg-1). Application of PFAS biosolids international guidance to samples analysed highlighted that 24–88% of biosolids exceeded regulatory standards, although this number increased when precursor compound oxidation was taken into consideration.
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