Investigating the partitioning behavior of per- and polyfluoroalkyl substances (PFAS) during thermal landfill leachate evaporation

Thermal landfill leachate evaporator systems can reduce the volume of leachate by up to 97 percent, while releasing water vapor and producing residuals (volume-reduced leachate and sludge) that are managed on-site. On-site thermal evaporators offer landfill operators leachate management autonomy without being subject to increasingly stringent wastewater treatment plant requirements. However, little is known about the partitioning of PFAS within these systems, nor the extent to which PFAS may be emitted into the environment via vapor. In this study, feed leachate, residual evaporated leachate, sludge, and condensed vapor were sampled at two active full-scale thermal landfill leachate evaporators and from a laboratory-scale leachate evaporation experiment. Samples were analyzed for 91 PFAS via ultra-high pressure liquid chromatography - tandem mass spectrometry (UHPLC-MS/MS). Similar trends were observed from Evaporator 1, Evaporator 2, and the laboratory-scale evaporator; ∑PFAS were concentrated in the residual evaporated leachate during evaporation by a factor of 5.3 to 20. All condensed vapors sampled (n=5) contained PFAS, predominantly 5:3 fluorotelomer carboxylic acid (5:3FTCA), (full-scale vapors 729 – 4,087ng/L PFAS; lab-scale vapor 61.0ng/L PFAS). For Evaporators 1 and 2, an estimated 9 – 24% and 10%, respectively, of the PFAS mass entering the evaporators in leachate was released with vapor during the days of sample collection. ‘ Environmental Implications The US Environmental Protection Agency recently proposed the designation of nine select PFAS as hazardous constituents due to the chemicals’ adverse health effects. PFAS continue to enter landfills in disposed waste products, then exit landfills via aqueous discharge, landfill leachate. Landfill leachate is a complex liquid which poses many treatment challenges. In the search for cost-effective leachate management, landfill operators are installing on-site technologies such as thermal evaporators. Here we characterize PFAS behavior in landfill leachate evaporators and evaluate the extent to which evaporators emit PFAS in vapor and retain PFAS in evaporation residuals.