Pilot-Scale Thermal Destruction of Per- and Polyfluoroalkyl Substances in a Legacy Aqueous Film Forming Foam

The destruction of per- and polyfluoroalkyl substances(PFAS) iscritical to ensure effective remediation of PFAS contaminated matrices.The destruction of hazardous chemicals within incinerators and otherthermal treatment processes has historically been determined by calculatingthe destruction efficiency (DE) or the destruction and removal efficiency(DRE). While high DEs, >99.99%, are deemed acceptable for mosthazardouscompounds, many PFAS can be converted to other PFAS at low temperaturesresulting in high DEs without full mineralization and the potentialrelease of the remaining fluorocarbon portions to the environment.Many of these products of incomplete combustion (PICs) are greenhousegases, most have unknown toxicity, and some can react to create newperfluorocarboxylic acids. Experiments using aqueous film formingfoam (AFFF) and a pilot-scale research combustor varied the combustionenvironment to determine if DEs indicate PFAS mineralization. Severaloperating conditions above 1090 degrees C resulted in high DEs and fewdetectable fluorinated PIC emissions. However, several conditionsbelow 1000 degrees C produced DEs > 99.99% for the quantifiable PFASand mg/m(3) emission concentrations of several nonpolar PFASPICs. These results suggest that DE alone may not be the best indicationof total PFAS destruction, and additional PIC characterization maybe warranted.