Distribution of Per- and Polyfluoroalkyl Substances (PFASs) in a Waste-to-Energy Plant─Tracking PFASs in Internal Residual Streams

Per- and polyfluoroalkyl substances (PFASs) constitute a diverse group of man-made chemicals characterized by their water- and oil-repellent properties and persistency. Given their widespread use in consumer products, PFASs will inevitably be present in waste streams sent to Waste-to-Energy (WtE) plants. We have previously observed a subset of PFASs in residual streams (ashes, treated process water, and flue gas) from a WtE plant. However, the transport and distribution of PFASs inside the WtE plant have remained unaddressed. This study is part of a comprehensive investigation to create a synoptic overview of the distribution of PFASs in WtE residues. PFASs were found in all sample types except for boiler ash. The total levels of 18 individual PFASs (Σ₁₈PFASs) in untreated flue gas ranged from 5.2 to 9.5 ng m^-3, decreasing with 35% ± 10% after wet flue gas treatment. Σ₁₈PFASs in the condensate ranged from 46 to 50 ng L^-1, of which perfluorohexanoic acid (PFHxA) made up 90% on a ng L^-1 basis. PFHxA was also dominant in filter ash, where Σ₁₈PFASs ranged from 0.28 to 0.79 ng g^-1. This study shows that flue gas treatment can capture some PFASs and transfer them into WtE residues.