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Use of Fluorinated Refrigerants as Indicators of Thermal Treatment Effectiveness for Per- and Polyfluoroalkyl Substances (PFAS)
Citation:
Krug, J., W. Roberson, E. Shields, J. Mattila, Pertti Virtaranta, P. Lemieux, W. Linak, R. Burnette, S. McDonald, G. Whitfield, AND W. Preston. Use of Fluorinated Refrigerants as Indicators of Thermal Treatment Effectiveness for Per- and Polyfluoroalkyl Substances (PFAS). 40th Annual International Conference on Thermal Treatment Technologies & Hazardous Waste Combustors, Charlotte, NC, September 13 - 14, 2023.
Impact/Purpose:
PFAS and fluoro-organic wastes are an emerging pollutant class with little in the way of published data to inform decisions regarding the efficacy of thermal treatment technologies to control emissions. There are concerns about whether conditions within the large variety of combustors and incinerators used to dispose PFAS laden wastes adequately mineralize PFAS (forming CO2 and HF) or if fluoro-organic structures survive to be emitted as products of incomplete combustion (PICs). While PFAS laden wastes are frequently composed of complex mixtures of high-molecular weight PFAS compounds resulting in many possible PICs and complex and costly methods for their measurement. A simplified approach for determining effectiveness of thermal treatment technologies is potentially useful for determining efficacy of thermal treatment technologies. This study investigates the formation of volatile, non-polar PICs from four commercial PFAS-laden aqueous film forming foam formulations and compares PIC formation to destruction efficiency of three fluorinated refrigerant compounds (CHF3, C2F6, and C3F8) within EPA’s pilot-scale incinerator.
Description:
EPA’s Office of Research and Development performed a series of experimental studies using a pilot-scale down-fired natural gas combustor to examine the thermal destruction of per and poly-fluorinated alkyl substances (PFAS). Testing was performed on four distinct PFAS containing formulations of Aqueous Film Forming Foam (AFFF) concentrates at a range of furnace injection temperatures indicative of incomplete mineralization. In addition to AFFF, injections of fluorinated refrigerant compounds (i.e., CHF3, C2F6, and C3F8) were individually and concurrently with AFFF injections to ascertain if they are indicators of thermal treatment performance of other PFAS compounds. Quantitative recoveries of the fluorinated refrigerants were achieved by Fourier infrared spectroscopy (FTIR), accompanied with dynamic spiking with each refrigerant. In addition, application of an in-development canister sampling method for analysis of volatile, non-polar PFAS compounds was used to evaluate formation of selected fluorinated products of incomplete combustion (PICs) from each of the AFFF mixtures. Species and concentrations of PICs were compared as a function of injection temperature and parent PFAS species in the liquid AFFF concentrates. Finally, the various PIC formations were compared to the apparent destruction efficiency (DE) of the injected refrigerant compounds to determine if there is correlation between AFFF PIC formations and the DE of potential surrogate compounds. This presentation will discuss the current experimental program, measurement techniques for both FTIR and canister sampling methods, experimental results from EPA’s pilot-scale combustor (including the formation and nature of PICs), and future research plans.