Per- and polyfluoroalkyl substances (PFAS) in landfill leachate, condensate, and groundwater: Characterization by landfill age and evaluation of activated carbon, ion exchange, and electrochemical treatment

Municipal landfills contain elevated PFAS in leachate and gas condensate which can contaminate groundwater and burden wastewater treatment facilities. Gas condensate and leachate were collected from young (primarily active in the last 5 years) and mature (active 1960's to 2010's) municipal landfill piles, together with groundwater and leachate at point-of-discharge. The sum of 30 analyzed PFAS ranged from 0.11 μg/L in groundwater to 8.8 μg/L in young leachate, with young landfill samples containing twice the PFAS of mature samples. Batch adsorption tests found ion exchange (IEX) outperforms granular activated carbon (GAC) based on higher PFAS affinity (up to Freundlich K = 393 μg/g/μg/L, n = 1.0) and uptake (pseudo-first order rate constant k₁= 0.03-0.05/min). Poor dissolved organic carbon (DOC) uptake was observed for both GAC and IEX (10-20% removal), while bicarbonate uptake coupled with chloride release (equivalent to 30-50% resin capacity) confirms electrostatic exchange even in saline leachate. Batch electrochemical treatment was less effective at treating young leachate than mature leachate, achieving 50% removal of ΣPFAS after 12 h in the former compared to near-complete removal for mature leachate. Higher organic content and chloride in young leachate (DOC = 2 g/L, chloride = 1 g/L) than mature leachate (DOC = 1.5 g/L, chloride = 0.5 g/L) resulted in significant energy diversion (DOC removal 65%) to the detriment of PFAS destruction. IEX and electrochemical treatment achieve significant PFAS removal from landfill condensate and leachate, with mature landfill waste emerging as a strategic target for further treatment testing.