Initiatives

PFAS in Landfill Leachate

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:

Type and amount of waste landfilled
Age of the landfill
Sampling locations and years
Climate
Industrial discharges

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.

Survey on leachate at public landfills

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

How PFAS is treated in landfill leachate

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.

On-Site Leachate Treatment Technologies

Adsorption and ion exchange

Ion exchange resin beads — Image of beads (<0.5 mm in diameter) of ion exchange resin obtained from an educational lab prior to disposal.

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.

Granular Activated Carbon (GAC)

Schematic illustration of adsorption of PFOA and PFOS on activated carbon (from Yu, et al.)

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

Watercareservice, CC BY-SA 4.0 via Wikimedia Commons — Water purification reverse osmosis plant.

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:

Modified bentonite adsorbents
Foam fractionation
Supercritical water oxidation
Low temperature plasma
Photochemical degradation

Co-Treatment Issues with Wastewater Treatment Plants

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.

Over 60% of active landfills discharge PFAS to wastewater (EREF, 2018)
Contribution relatively minor (Masoner et al., 2020)
Non-leachate sources contribute greater mass to effluent than leachate

Barriers to Research

Shorter-chain compounds not measured
Unregulated compounds not being tested for

Special Thanks

A special thank you to the Landfill Technical Division Landfill Leachate and Liquids Committee for providing up-to-date scientific and technical data about PFAS in solid waste.

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