A mini-review of PFAS thermal treatment and operating conditions at commercial hazardous waste rotary kiln incinerators

In this mini-review article, the United States Environmental Protection Agency's (EPA) PFAS Analytic Tools database was used to identify shipments of per- and polyfluoroalkyl substances (PFAS)-containing wastes from points of generation to points of treatment, disposal and destruction. After 'Other Recovery or Reclamation for Reuse', 'Incineration' is the largest treatment category. Since mid-2018, approximately 6500 tonnes of PFAS-containing wastes have been treated at eight United States (US) commercial hazardous waste incineration (HWI) facilities equipped with rotary kiln primary combustion chambers (PCCs) followed by secondary combustion chambers (SCCs). A search of publicly available data was used to document design, permit and operating parameters for these eight HWI facilities. Results from this survey will be used to help inform the design of experimental efforts using EPA's rotary kiln incinerator simulator (RKIS) to study how these process parameters affect the thermal destruction of PFAS-containing wastes. Of particular interest is the effect of routine transient operations of the rotary kiln due to the batch introduction of containerised wastes on PFAS destruction, mineralisation and the formation of fluorinated and mixed halogenated products of incomplete combustion (PIC). Permit minimum PCC and SCC temperatures for the 10 rotary-kiln-based HWIs located at the 8 facilities ranged from 461°C to 1076°C in the PCCs and 923°C-1156°C in the SCCs. Initial evaluation suggests that temperatures in this range may be comparable to temperatures reported to produce measurable fluorinated PICs, especially considering the variable operation inherent in these systems, and that permit minimum temperatures are based on 1-hour rolling averages of 1-minute average temperature measurements.