Science Inventory

Per- and Polyfluoroalkyl Substances (PFAS) Distribution in Landfill Gas Collection Systems: leachate and gas condensate partitioning

Citation:

Smallwood, T., N. Robey, Y. Liu, J. Bowden, T. Tolaymat, H. Solo-Gabriele, AND T. Townsend. Per- and Polyfluoroalkyl Substances (PFAS) Distribution in Landfill Gas Collection Systems: leachate and gas condensate partitioning. JOURNAL OF HAZARDOUS MATERIALS. Elsevier Science Ltd, New York, NY, 448:130926, (2023). https://doi.org/10.1016/j.jhazmat.2023.130926

Impact/Purpose:

The results of this study may contribute to a better understanding of how PFAS in waste contributes to PFAS in landfill effluent, which includes leachate and LFG. While the two leachate matrices studied here are typically combined and managed in the same manner as any other leachate type, separate management may reduce, for instance, precursor PFAS concentrations in leachate, which is treated using standard wastewater treatment techniques that may have the potential to transform precursor PFAS to terminal PFAS, which are more likely to be regulated and are of concern. This study represents the most in-depth characterization of these discrete leachate matrices to date.

Description:

While per- and polyfluoroalkyl substances (PFAS) have been reported extensively in landfill leachate, discrete sources of leachate from within MSW landfills are not as well understood. Samples of gas condensate (GC) – a liquid formed when water vapor in landfill gas condenses – and leachate collected from within gas wells (gas well pump-out, GWP) from three municipal solid waste (MSW) landfills underwent physical-chemical characterization and PFAS analysis to provide a better understanding of the conditions under which these liquids form and to shed light on PFAS partitioning, transformation, and potential volatilization within landfills. GC was observed to be a clear liquid consisting mostly of ammonia and alkalinity while GWP strongly resembles leachate – dark in color, and high in chloride and ammonia. GC contained a lower average concentration of ΣPFAS (18,857 ng L-1) compared to gas well pump-out (55,589 ng L-1), however, GC contained a greater diversity of PFAS, with a total of 53 PFAS quantified in GC, compared to 44 in GWP. Among terminal PFAS, GC contained fewer sulfonic acids, which volatilize less readily than carboxylic acids. GC also contained proportionally more precursor PFAS than GWP, including higher concentrations of semi-volatile fluorotelomer alcohols and perfluoroalkane sulfonamido ethanols. The results of this study provide, for the first time, a detailed comparison of these matrices and data to inform timely leachate management and treatment decisions.