Landfill leachate is the effluent formed by rainwater percolating through waste in landfills. Leachate generation may continue even after a landfill’s closure period, as a result of inherent liquids in the waste or if the cap system fails.
We estimate that between 27.7–29.2% of landfilled PFAS is collected with leachate in the US. That amounts to about 1,241–1,407 lbs (563–638 kg) of PFAS in leachate per year.
Several factors can affect the type and concentration of PFAS in landfill leachate:
Landfills located in wet weather regions may show much higher PFAS leaching than those in temperate and arid regions, because abundant precipitation facilitates the leaching process.
Drs. Stephanie Bolyard (Florida State University) and Nick Chen (University of Central Florida) are conducting a short survey on the generation and treatment of leachate at public landfills in the Eastern US and Pacific Northwest in 2021. More information about the study is on MySWANA.Reps for eastern US & Pacific Northwest public landfills can fill out the survey here
Landfill leachate can be treated on-site or off-site. The most common off-site treatment is to export leachate to a wastewater treatment plant (WWTP where) it is mixed with wastewater and treated.
Adsorption is a physical mass transfer process that uses ionic forces to bind the entire PFAS molecule to the surface areas of adsorptive media (such as iron and aluminum).
Ion exchange targets and binds to the hydrophilic ionized—or functional—end of the molecule (for example, the sulfonate in PFOS), while releasing an equivalent amount of an innocuous ion (for example, chloride) into treated water.
Removal of PFAS by GAC is a physical mass transfer process from the liquid phase into solid media. GAC is very similar to adsorption technologies, except it does not involve or trigger any form of chemical degradation or transformation. Temporary and permanent GAC systems can be rapidly deployed and require minimal operator attention (if intensive pretreatment is not needed).
Reverse osmosis is a technology used to remove a large majority of contaminants (including PFAS) from water by pushing the water under pressure through a semipermeable membrane. The most common membrane module configuration is spiral-wound, which consists of flat sheet membrane material wrapped around a central collection tube.
Other technologies are still being researched:
The most common off-site approach is to export leachate to a wastewater treatment plant (WWTP where) it is mixed with wastewater and treated. However, conventional wastewater treatment technologies are generally unable to treat or control PFAS.
This report provides solid waste landfill managers with up-to-date information and guidance on PFAS options for landfill leachate.
The full report is available free to SWANA Members ($99 for the general public).