Per- and polyfluoroalkyl substances in municipal solid waste incineration ash: occurrence and management implications

Per- and polyfluoroalkyl substances (PFAS) have been detected in municipal solid waste incineration (MSWI) ash, but the extent to which they partition between bottom ash (BA) and fly ash (FA) remains poorly understood. This study examined 52 PFAS at four Florida MSWI facilities, finding BA had a higher mean ⅀₅₂PFAS concentration (2.2ng g^-1) than FA (0.33ng g^-1). Fluorotelomer phosphate diesters (diPAPs) predominated in BA, whereas FA exhibited a more varied PFAS profile; however, the quantification of diPAPs in FA is subject to uncertainty due to low extraction recoveries. BA emerged as the primary PFAS source in MSWI residues, accounting for 89 % of the state annual estimate (2.4 kg). A significant correlation between loss on ignition (LOI), a measure of unburned organic matter, and PFAS in BA, suggests that improving burnout could reduce PFAS in ash. Preliminary estimation suggests 1.2 % to 8.6 % of PFAS remained post-incineration in ash, with the most efficient burnout retaining the least PFAS. However, stack testing is necessary to ascertain the extent of PFAS destruction or emission through exhaust gas. A risk assessment revealed that PFAS in BA are below existing EPA benchmarks, but the highest detected PFAS neared the limits calculated based on the strictest proposed drinking water standards. Future research should evaluate PFAS leaching risks from BA during reuse, especially for the dominant diPAPs.