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.