The EPA is increasingly concerned about threats to the environment and human health from PFAS found in landfill leachate. Here is how landfill operators can respond.
By Bernard Rieder
There has been a lot of uncertainty around how landfill operators should respond to the issue of PFAS-containing materials that have come in through their waste stream. While it seems inevitable that landfills will need to provide treatment of their leachate to remove PFAS, many operators are reluctant to do so, partly because of lack of clarity around the standards they will need to meet, and the timeline.
Why the Regulatory and Public Concern About PFAS?
Per-and Polyfluoroalkyl Substances, collectively known as PFAS, have for more than 50 years been used in a wide range of products, including firefighting foam, paints, cosmetics, breathable outerwear, and non-stick cookware.
Despite their usefulness, there is increased scientific and regulatory concern about the impacts of PFAS. Given its widespread use, PFAS is virtually everywhere. It tends to bio-accumulate, so it is concentrated in top predators in an ecological system, as well as human beings.
Recent EPA Actions
The way forward is becoming clearer through guidance documents issued by the EPA, for Publicly Owned Treatment Works (POTW). The EPA’s new guidance memorandum in December 2022 for state governments, provides direction on how they can use the National Pollutant Discharge Elimination System (NPDES) permitting program to address PFAS in waters of the U.S.
This is part of the EPA’s PFAS Strategic Roadmap, announced in October 2021, laying out a whole-of-agency approach to addressing PFAS. This roadmap sets out timelines for action to safeguard human populations and the natural environment, from the risks associated with PFAS.
As part of this initiative, the EPA provided guidance letters in early 2022 that directed POTWs to look upstream at the sources of their influent, to see which might be contributing significantly to any PFAS in the POTW’s effluent. The EPA has said that one of the industries that are known or suspected dischargers of PFAS-impacted wastewater, is the landfill sector.
On March 14, 2023, the U.S. EPA proposed a National Primary Drinking Water Regulation (NPDWR) to establish legally enforceable Maximum Contamination Levels (MCLs) for six PFAS in drinking water. The proposed rule will regulate two PFAS compounds—PFOA and PFOS—as individual contaminants with an MCL of 4 parts per trillion (ppt) each.
The EPA is also proposing a Hazard Index MCL to address mixtures containing one or more of PFNA, PFHxS, PFBS, and/or GenX Chemicals. The promulgation of MCLs, anticipated to be adopted by the end of 2023, will likely establish a basis for cementing more definitive surface and groundwater criteria as they relate to potential impact on drinking water sources.
Landfill Perspectives and Challenges
In the view of many members of the landfill sector, including SWANA, landfills are not “generators” of PFAS, but rather “receivers.” This implies that the PFAS problem rests on the desks of people who use PFAS in their products, which end up in landfills. The EPA’s response to that seems to be, “No.” As far as the EPA is concerned, the problem of PFAS flowing from landfill leachate is the landfill’s problem to solve. And because so much of what our society makes ends up in landfills, some of that PFAS flows into landfill leachate.
For decades, many landfills have taken the straightforward solution of pipelining or trucking their leachate to their local POTW for treatment. But many POTW operators, and their municipal owners, are becoming concerned about their environmental liabilities coming from their discharge pipes, due to potential impacts to surface water and aquatic species. As discharge requirements have become more restrictive and treatment infrastructure has aged, POTWs have faced increasing challenges to meet their requirements. In response, many POTWs have shut off or restricted landfill leachate acceptance. These trends have been occurring for years—well in advance of any public concerns or regulations regarding PFAS discharges.
Many states have developed their own MCLs and discharge requirements for PFAS—landfills in several states are seeing the impacts of state-led regulatory oversight. The recent EPA actions are anticipated to heighten regulatory and public scrutiny over the landfill sector and are expected to impact landfills in all states. Specifically, the recent changes in the EPA’s approach to PFAS management via the NPDES permit process, is likely to cause this trend to increase.
While unofficially it seems that the EPA is considering deadlines for action of around 2025 or 2026, it is important for landfill operators to understand these requirements and assess their options now. Conventional leachate treatment alternatives may meet current wastewater discharge requirements for a given POTW but may not address future PFAS-derived discharge requirements. Landfill operators should consider future-proofing their systems in anticipation of future PFAS-related discharge requirements.
Engineering consultants, equipment manufacturers and other suppliers with experience in managing landfill leachate will be receiving an increasing flow of requests for help from landfill operators. The solid waste and wastewater industries are already stressed with finding engineers, operators, and managers to meet ongoing labor shortages. All these factors will ultimately lead to a significant demand, coupled with shortages in supply chain, or expertise in managing these issues.
Leachate in PFAS: A Two-Stage Solution
Removing impurities from landfill leachate is nothing new. We have installed more than 500 reverse osmosis (RO) leachate treatment systems in Europe, North America, and elsewhere. As a full-spectrum solution, RO can remove PFAS from leachate, along with other contaminants.
Many landfill operators have installed their own leachate treatment systems, using a variety of technologies, because they do not want to be vulnerable to decisions made elsewhere, such as at their POTW. It also saves the costs of transporting leachate, which in its raw state, can involve a great deal of truck traffic, with impacts for community relations.
Unlike conventional wastewater constituents, such as ammonia, there is no commercially available technology that can effectively and completely destroy PFAS in wastewater. One PFAS management strategy involves the use of technologies that can separate PFAS from the liquid fraction, allowing for a PFAS-free waste stream and a lower volume, higher concentrated PFAS residual stream.
Stage One: Reduce the Scope of the Problem
Under this strategy, the first stage is intended to reduce the large volume of liquid involved. Four main solutions for separating water from the dissolved and suspended particles in the leachate are below.
#1: Foam Fractionation
This technology uses the surfactant qualities of PFAS, to remove them from water. Foam fractionation involves releasing bubbles of air from below the water to be treated. The bubbles naturally move to the surface. On the way, the surface-active molecules, including PFAS, attach themselves to the gas-liquid interface of the bubbles, rising to form a foam on the liquid’s surface. This foam can then be skimmed off and isolated. Foam fractionation is a promising technology, but largely PFAS-specific and does not effectively address the conventional wastewater constituents in leachate. Additional treatment of the PFAS-clean stream will be required. Of the innovative technologies being evaluated, foam fractionation is considered the closest to commercial availability.
#2: Activated Carbon/Ion Exchange
This method uses activated carbon or ion exchange resins designed to preferentially adsorb or bond with PFAS molecules. This technology has been proven effective to remove PFAS from drinking water sources and has been applied across the country (and world) for many years. However, leachate is a very strong, complex wastewater and the constituents in leachate that will interfere with or plug ion exchange media absent of additional pre-treatment. Like the other separation processes, this system will generate a PFAS-laden residual that must be disposed or regenerated.
#3: Evaporation
The use of thermal energy to “boil off’ or evaporate leachate is a proven technology that will discharge leachate as a vapor stream, with the concept that less volatile PFAS will remain in the “bottoms”. While leachate evaporation is the most common application, the jury is still out regarding the fate of PFAS in evaporators and the impacts of potential loss of PFAS from evaporation. End of pipe treatment alternatives can be employed to sorb or knock out PFAS that may have evaporated or is attached to water droplets. Leachate evaporation is an energy intensive process and most effectively used where excess landfill gas (otherwise flared) is readily available or waste heat from landfill gas combustion engines can be used.
#4: Reverse Osmosis
Reverse osmosis, or “RO”, involves using pumps to push the liquid up against a semi-permeable membrane. Water molecules are small enough to slip through the membrane, while larger contaminant particles and molecules—including PFAS—stay on the “concentrate” side of the barrier. RO is a proven technology for landfill leachate. Systems that have been in place for years (well before PFAS were on any landfill operator’s radar) have demonstrated their ability to completely remove PFAS (to less than detection limits).
To quote a report by the SWANA Applied Research Foundation, “PFAS Management and Treatment Options for Landfill Leachate” (summary is downloadable from SWANA.org): “Reverse osmosis (RO) is a commercially proven process for PFAS leachate treatment that does not require leachate pre-treatment through a membrane bioreactor or similar conventional wastewater treatment process. RO appears to provide a PFAS leachate treatment option that requires less wastewater process knowledge and operator involvement than some other technologies.”
Many RO installations have received permits to discharge their effluent to surface water, effectively making the concentrated liquid, perhaps 10 percent of the original volume, easier to manage.
All the above technologies are separation-based, in large extent they each serve to concentrate PFAS into a lower volume residual. They vary in commercial availability and ability to readily address PFAS and other constituents. In many instances, the technologies mentioned have been combined. RO, unlike the other three processes, will generate a very clean stream suitable for discharge to POTWs, or in many cases, direct discharge to surface water.
Stage Two: Residuals Management
Under the two-stage management scenario, the second problem is the difficulty of managing the residuals to prevent PFAS-laden materials from re-entering the environment. Ideally, this would best be accomplished through destruction of the PFAS molecules into their constituent atoms and benign molecules. However, this has proven to be extremely challenging due to the nature of PFAS molecules, which contain bonds between carbon and multiple fluorine atoms that are some of the strongest known to molecular science, making PFAS extremely resistant to breakdown. This is why they are often called “forever chemicals.”
While there is a wide array of promising technologies that have been studied and developed for accomplishing PFAS destruction, none of them has been proven to be fully commercially viable as most systems have only been proven at laboratory- or pilot-scale. Technologies that have been developed include: incineration, plasma, supercritical water oxidation, electrochemical oxidation, and hydrothermal alkaline treatment. Of these, incineration is the most commercially viable, but in certain locales may have its own challenges with respect to air permitting and public acceptance. In short, none of these technologies has yet been developed to readily accepted and proven commercially viable technologies.
Absent a proven PFAS destruction process, an alternative approach involves isolating PFAS from further release into the environment. A modern landfill is a highly engineered system that prevents surface water and groundwater impacts through state-of-the-art cover and liner systems designed to isolate waste and residuals from the environment. Leachate, which must be removed from the landfill is the primary “source” of PFAS. Where a site implements a separation process as noted above, the landfill offers the most effective disposal alternative for the concentrated residuals.
There have been numerous studies focused on the fate of PFAS in landfills that demonstrate landfills effectively “sequester” PFAS; the mass entering is far lower than the mass leaving (largely through leachate). By removing PFAS from the bulk leachate and maintaining the resultant residuals within the landfill’s containment system, a landfill can effectively isolate further PFAS release to the environment.
This isolation strategy is more readily adaptable to landfill operations as the separation strategies serve to generate a much lower volume of residuals for management. Currently, management of these residuals within the landfill footprint entail reapplication to the landfill working face, use of additional volume reduction processes, or stabilization of these residuals using cementitious materials, amongst others. While not necessarily the perfect solution, it remains the one option that can prevent PFAS release from landfills based on current technology limitations.
Many landfill operators are concerned about the future with regards to PFAS—to the extent that some are reluctant to test for PFAS in their leachate. However, the way towards a solution comes from knowledge. Then armed with that knowledge, it is best to reach out to potential solution providers, helping protect the environment and the human population. | WA
Bernard Rieder is the General Manager for Rochem Americas Inc. He holds a graduate degree in Environmental Engineering and has experience with Republic Services and Casella Waste Systems, Inc., and more than 20 years in total with Waste Management. Bernie can be reached at [email protected]. For more information, visit www.rochemamericas.com.