Evaluating the potential of thermal evaporation for onsite retention of per- and polyfluoroalkyl substances (PFAS) in landfill leachate.

Since traditional management of landfill leachate at wastewater treatment plants was found to release per- and polyfluoroalkyl substances (PFAS), alternative technologies are being evaluated for PFAS treatment efficiency. Thermal evaporation is an emerging landfill leachate treatment option allowing for autonomous, onsite management of concentrated residuals while discharging the treated bulk as vapor. This study evaluated the potential of thermal evaporation for onsite PFAS retention by comparing PFAS concentrations in the inputs (leachate and landfill gas) and outputs (evaporation residuals and vapor) of a full-scale evaporator and explored PFAS deposition onto nearby soil. Liquid chromatography-tandem mass spectrometry analyzing 66 anionic PFAS (iPFAS) and gas chromatography-high resolution mass spectrometry analyzing 27 neutral PFAS (nPFAS) were employed. Both iPFAS and nPFAS were measured in vapor emissions (126 and 783 ng/m3, respectively). The percent removal of iPFAS from re-condensed vapor was > 92 % for six perfluoroalkyl acids, but only 32 % for 5:3 fluorotelomer carboxylic acid, the dominant iPFAS in vapor. However, the percent retention in evaporation residuals was only 48-82 % for the same perfluoroalkyl acids, and an added resin sampler captured additional gas-phase iPFAS emissions previously overlooked. iPFAS and nPFAS present in landfill gas (106 and 621,000 ng/m3, respectively) may also contribute to PFAS emissions due to incomplete combustion. Concentrations of iPFAS in soil within 100 m of the evaporator (0.174-4.87 ng/g) were higher (p-value < 0.01) than those in soil 1-4 km away (0.016-0.393 ng/g). These results demonstrate the need for further optimization of thermal evaporation systems to prevent airborne PFAS emissions.