Federal and especially state regulatory attention on PFAS is increasing, with dozens of states having some policy in place. Meanwhile a lot more science is needed to understand these compounds’ potential environmental and health impacts. And landfill operators should pay attention since most of these highly toxic chemicals eventually end up at their facilities. That was the high-level takeaway of Part 1 of the WasteExpo session: “What is PFAS and How do we Treat it?”
The conversation moved on to address a lot of intriguing questions. Those at the podium were Bryan Staley, Environmental Education and Research Foundation (EREF); Sean McGinnis, The COEFFICIENT Group; and moderator Steven Menoff, Civil & Environmental Consultants.
There are about 4,500 PFAS compounds and limited research on them. Further, not all tests look at the same compounds or same number of compounds, so data from one study is typically not comparable to another.
Adding complexity, PFAS manufacturers will switch to different compounds, and tests do not exist for all of them.
So, Staley said, science and analytics are way behind. Science is working to try and catch up. But it’s been a challenge, he said, commenting, “This is one of the fastest-moving issues I’ve seen in the waste management industry, and it’s been somewhat of a bull to try and wrestle to the ground.”
There are a lot of important questions to ask: What is waste management’s contribution to human exposure? Where is PFAS coming from? How is it managed?
EREF, who recently funded six PFAS studies, is looking to learn more in areas such as effectiveness of thermal destruction as a treatment and how much PFAS could be in landfill gas.
Meanwhile, these long-lasting chemicals can be released from waste into leachate. And it’s in plenty that makes its way to landfill. It’s in products from grease-resistant food packaging to waterproof and fire-resistant gear.
What could be good news is that studies suggest landfills act as sequestration vehicles for PFAS, which is in alignment with what is known in general about how landfills behave and what happens with materials disposed on these sites.
Another small positive is that PFAS in leachate is in shorter chain compounds, suggesting a transformation happens in landfills, and PFAS in this form appear to have slightly less health and environmental effects.
Scientists are looking at whether landfill liners are able to create a sufficient barrier for PFAS control.
“Graphics show it moving through landfill liners, which suggests it goes in groundwater. But research suggests that’s not happening,” Staley said.
EREF is looking at this closer for more definitive answers, with a study at the University of Virginia testing to see if it goes through liners and, if so, to what extent.
PFAS compounds can mobilize and be found in fugitive gas emissions, studies suggest. But to what extent it may be in landfill gas is another unknown.
Currently there is no method to test PFAS in landfill gas, but there’s ongoing research to learn more at North Carolina State University, funded by the U.S. Environmental Protection Agency (EPA).
Another landfill gas focus is to see if flares destroy PFAS.
“Anecdotally there are suggestions that they do. But we do not know to what extent, so we are also looking into this,” Staley said.
There is research into thermal treatments. EREF is working to determine how quickly PFAS is combusted; at what temperature complete destruction occurs; and what will happen to it at waste-to-energy facilities.
There has been scrutiny around landfill leachate’s contribution to PFAS at publicly owned wastewater treatment plants (POTW). Studies indicate that non-leachate sources contribute more PFAS mass to these facilities.
McGinnis pointed to two such studies: one by North Carolina’s Department of Environmental Quality (DEQ) and one out of Michigan done with Michigan Waste & Recycling Association that also showed leachate is not a primary contributor of PFAS at POTW’s.
Also of note is not only that PFAS-containing leachate may go to POTW’s, but the biosolids accumulating in these compounds come back to landfill from those POTW’s.
Because of this back-and-forth cycling, said McGinnis, the wastewater sector and solid waste sector should communicate from a regulatory and policy development standpoint.
“They can share information to prevent disruptions as the PFAS regulatory landscape is unfolding,” he said.
There has been conversation around what happens to PFAS in compost. One study showed compost with food packaging contains 10 times more PFAS. But whether there are emissions has not been scientifically documented.
Less is known about what happens at materials recovery facilities, as it’s undetermined whether PFAS accumulates in products that use recycled material.
Another heavy research direction is to look at how to manage it, with one large focus being on solidification and encapsulation of material so it does not move. These techniques create non-leachable and solidified structures that can then be disposed of after first treating the leachate.
Ultimately Staley said, there needs to be an understanding of where the contribution is coming from, whether leachate or elsewhere.
“When all is said and done, we may find out that the solid waste industry is not the main contributor. But a lot of research is needed to learn more.”
“What is PFAS and How do we Treat it?” Part 2 took a highly technical look at PFAS with presenters Angus McGrath, Stantec Consulting Services; Arie Kremen, Cornerstone Environmental Group; and Ivan Cooper, Civil & Environmental Consultants.
Key takeaways McGrath shared on PFAS, impacts, and treatments:
Long chain and short chain PFAS compounds have different properties. Shorter chain PFAS are typically found in leachate, which has somewhat less impact than longer chain.
Concentrations depend on what landfills take in. There tend to be higher concentrations at disposal sites that accept construction debris.
Changes in climate conditions tend to have a greater impact on what happens with PFAS than the processes taking place at landfills.
Existing treatment technologies are adsorption, filtration, coagulation, and fractionation.
- The adsorption techniques, granular activated carbon and ion exchange, are technologies of choice for meeting effluent limits. Granular activated carbon has greater efficiency for longer chain. Ion exchange is making some inroads and seems to have greater efficiency with short chain PFAS.
- Reverse osmosis is one of the more successful established filtration processes. It can concentrate PFAS but typically requires further treatment. Coagulation may follow to drop out PFAS.
- This technology has a lot of promise because other contaminants do not interfere with it. There are specialty coagulants that can optimize treatment.
- There are a series of inorganic coagulants, and how they operate depends on dosing, but the process generates waste.
- Electrocoagulation may improve treatments, but it is expensive and has mixed results. It can remove PFAS and PFOA.
- There are also destructive technologies such as incineration. However, if the right temperature is not reached the outcome is poor due to incomplete oxidation. The Air Force has a moratorium on sending PFAS for incineration for this reason.
- Super critical water oxidation completely destroys PFAS and is not susceptible to co-contaminants other than possibly metal. However, this technology is very expensive.
Kremin shared key research findings around contributors to PFAS and pathways by which it leaves landfills to include:
Precursors can contribute to PFAS that are not degradable, and precursors can be converted.
Mass cannot be destroyed; only converted.
Main pathways by which PFAS can leave landfills is leachate and landfill gas, though much more appears to come into landfills than leave these sites.
Research indicates about 60 million gallons per year are leaving landfills, with a total concentration of 745 kg per year leaving landfills in leachate.
PFAS enters mainly through biosolids, cover material, and rainwater.
Cooper further elaborated on treatments:
Treatments are building blocks; a series of technologies are needed to achieve solutions.
Granular activated carbon, ion exchange, and modified bentonites are effective treatments.
The promising segregation technologies are deep well injection, reverse osmosis, and foam fractionation, with the first two being further along in development.
Civil & Environmental Consultants designed some reverse osmosis systems with minimal pretreatment that work well. It has achieved 99.9% removal of PFAS.
Deep well injection is an option, with the proper geology, to be able to go deep into the ground. And pretreatment is important when this technique is used. Deep well injection entails a long, expensive permit process. And it requires a lot of pressure, adding more cost for pumping.
Civil & Environmental Consultants is working with an adsorbent called FLUORO-SORB,which is a modified bentonite. It is able to solidify and stabilize PFAS. While modified bentonite seems effective in removing PFAS constituents it uses activated carbon quickly.
Supercritical water oxidation can destroy PFAS and other organic chemicals, but it requires a lot of energy to achieve the required heat and pressure. It removes more than 99% of PFAS.