One source of concentrated poly- and perfluoroalkyl substances (PFAS) are landfills. These sources include leachates from different landfill types (ash, construction and demolition, and municipal solid waste), and from gas condensates, storm water and groundwater within the landfill boundaries. The objective of this study was to evaluate PFAS from these aqueous landfill sources for 26 PFAS species including 11 perfluoroaklyl carboxylic acids, 7 perfluoroalkyl sulfonates, 5 fluorotelomers, and 3 perfluorooctane sulfonamides. Landfills with leachate pre-treatment systems (reverse osmosis, powdered activated carbon, and biological aeration) were also evaluated to determine the effectiveness of treatment systems to remove or concentrate PFAS at full-scale landfill facilities. Results show that total PFAS concentrations were variable within groundwater and storm water with mean levels for groundwater of 1,100 ng/L and for storm water of 700 ng/L. The sites with highly elevated total PFAS in groundwater (5,000 to 10,000 ng/L) were characterized by unique landfill designs that could have contributed towards the elevated levels. Higher levels were observed in gas condensate (mean of 11,500 ng/L) with this liquid type representing the highest concentration measured to date through the current study (maximum of 81,000 ng/L). Among the landfill leachates, ash landfills tended to have the lowest levels of total PFAS on average (mean of 7,500 ng/L), followed by construction and demolition landfills (mean of 9,700 mg/L) and municipal solid waste landfills (MSW) (mean of 18,500 ng/L). Although ash landfills had the lowest average total PFAS concentration, this landfill type had the maximum total PFAS value for all leachates at 54,000 ng/L. Due to the high variability of the total PFAS levels, no statistical differences were observed between gas condensate and the different types of leachate. The predominant PFAS species in the samples showing extremely high levels (above 50,000 ng/L) were the perfluorooctane sulfonamides. Among the treatment systems reverse osmosis was the most effective with over 99% reductions in total PFAS within the permeate. The powdered activated carbon and biological aeration systems evaluated did not show significant reductions in total PFAS
