Composting the organic fraction of municipal solid waste (OFMSW) creates a nutrient rich soil amendment and reduces the amounts of wastes going to landfills or incineration. However, the occurrence and fate of persistent and challenging per-and polyfluoroalkyl substances (PFAS) in OFMSW composts have not been well studied. The loads and leachability of 17 perfluoroalkyl acids (PFAAs) were analyzed in nine OFMSW commercial composts and one backyard compost. PFAA loads ranged from 28.7 to 75.9 μg/kg for OFMSW composts that included food packaging and from 2.38 to 7.60 μg/kg for composts that did not include food packaging. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) were detected in all composts; however, OFMSW composts were dominated by short-chain PFAAs (>64%) and perfluoroalkyl carboxylates (PFCAs, >68%), particularly the C6 PFCA. The total oxidizable precursor assay indicated the presence of PFAS precursors in three OFMSW composts for which 6:2 fluorotelomer sulfonate and 6:2 dipolyfluoroalkyl phosphate ester were identified. Of the total PFAA load in the composts, 25−49% was released to porewater (∼1 g/2 mL). PFAA porewater concentrations versus PFAA loads as well as organic carbon-normalized sorption coefficients versus the number of PFAA CF 2 units are strongly correlated (R 2 > 0.85).

There is increasing concern over the presence of per-and polyfluoroalkyl substances (PFAS) in biosolids, while sales in commercially available biosolid-based products used as soil amendments are also increasing.Here, the occurrence of 17 perfluoroalkyl acids (PFAAs) present in 13 commercially available biosolid-based products, six organic composts (manure, mushroom, peat, and untreated wood), and one food and yard waste compost were studied. The PFAA concentration ranges observed are as follows: biosolidbased products (9.0−199 μg/kg) > food and yard waste (18.5 μg/kg) > other organic products (0.1−1.1 μg/kg). Analysis of 2014, 2016, and 2018 bags produced from one product line showed a temporal decrease in the total PFAAs (181, 101, and 74 μg/kg, respectively). The total oxidizable precursor (TOP) assay revealed the presence of PFAA precursors in the biosolid-based products at much higher levels, when the soluble carbon was removed by the ENVI-Carb clean-up prior to the TOP assay. Time-of-flight mass spectrometry confirmed the presence of three sulfonamides, two fluorotelomer sulfonates, and several polyfluoroalkyl phosphate diesters. Pore-water concentrations of water-saturated products were primarily of short-chain PFAAs and increased with increasing PFAA concentrations in the products. A strong positive log-linear correlation between organic carbon (OC)-normalized PFAA partition coefficients and the number of CF n units indicates that OC is a good predictor of PFAA release concentrations.

Per‐ and polyfluoroalkyl substances (PFAS) have been used in a variety of consumer and industrial products and are known to accumulate in sewage sludge due to sorption and their recalcitrant nature. Treatment processes ensure safe and high‐quality biosolids by reducing the potential for adverse environmental impacts such as pathogen levels; however, they have yet to be evaluated for their impact on the fate of PFAS. The objective of this study was to compare PFAS concentrations in four commercially available biosolid‐based products that received different types of treatments: heat treatment, composting, blending, and thermal hydrolysis. Seventeen perfluoroalkyl acids (PFAAs) were quantified using liquid chromatography with tandem quadrupole time‐of‐flight mass spectrometry followed by screening for 30 PFAA precursors. Treatment processes did not reduce PFAA loads except for blending, which served only to dilute concentrations. Several PFAA precursors were identified with 6:2 and 8:2 fluorotelomer phosphate diesters in all samples pre‐ and post‐treatment. Practitioner points Heat treatment and composting increased perfluoroalkyl acid (PFAA) concentrations. Only dilution from blending with non‐PFAS material decreased PFAA concentrations. Thermal hydrolysis process had no apparent effect on PFAA concentrations. PFAS sources are a greater driver of PFAS loads in biosolid‐based products than treatment processes.

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