This project aims to determine the effectiveness of thermal decomposition technologies for per- and polyfluoroalkyl substance (PFAS) destruction to address needs related to aqueous film-forming foam feedstocks and contaminated sources. Through laboratory- and pilot-scale testing, this work will improve the understanding of the fate of PFAS during thermal treatment and will demonstrate an easily applicable surrogate method to ensure complete destruction of PFAS wastes. This work’s objective is to provide the practical operating parameters of temperature and residence time that will ensure complete destruction of PFAS, without problematic byproducts, in systems applicable to multi-media treatment.

This work will combine laboratory experiments and pilot-scale testing to systematically evaluate the effectiveness of thermal treatment technologies for destruction of PFAS. PFAS thermal destruction reactivity will be determined in laboratory- and pilot-scale facilities and data from that work will be applied to determine an effective surrogate and to determine a technology’s PFAS Destruction and Removal Efficiency (DRE). Laboratory-scale studies of thermal destruction mechanisms of various PFAS will be used to determine the thermal destructibility of small perfluorocarbons and larger PFAS. The Environmental Protection Agency’s 66 kW pilot-scale Rainbow furnace will be included in this testing to develop a PFAS surrogate method, an easily measured molecule that can be doped into the treatment method to evaluate the DRE of industrial thermal treatment facilities. Preliminary studies with the Rainbow furnace indicate that tetrafluoromethane, hexafluoroethane, and other fluorocarbons may be suitable surrogates, since they require high temperatures for complete destruction and are easily measured using on-line infrared spectroscopy. The sampled DRE for the PFAS surrogate and PFAS in the furnace will allow the determination of the relationship between the DRE of the fluorocarbon surrogate and the PFAS waste.

EPA scientists use the “Rainbow” furnace, a pilot-scale incinerator, to conduct experiments to assess PFAS destruction by incineration and products of incomplete combustion that may be formed. Here a PFAS sample is being injected into the orange section of the furnace. A Fourier Transfer Infrared spectrometer (FTIR) and an evacuated canister are shown as they sample for volatile PFAS and fluorocarbon emissions. Other types of fluorinated emissions are collected using sampling trains on the floor above.

The accumulation of fundamental PFAS destruction data and a surrogate method to evaluate industrial-scale thermal treatment technologies will provide valuable information, practical evidence, and guidelines for PFAS destruction to transition to industry and the Department of Defense (DoD). This will give the DoD confidence that their PFAS wastes are being destroyed and potentially harmful PFAS byproducts are not being released into the environment. (Anticipated project completion - 2024)

Krug, J.D., P.M. Lemieux, C.W. Lee, J.V. Ryan, P.H. Kariher, E.P. Shields, L.C. Wickersham, M.K. Denison, K.A. Davis, D.A Swensen, R.P. Burnette, J.O.L Wendt, and W.P. Linak. 2022. Combustion of C1 and C2 PFAS: Kinetic Modeling and Experiments. Journal of the Air & Waste Management Association, 72:256-270.