Tackling PFAS contamination at military bases and airports

By Michel France and Jennifer Kirk 

PFAS first went into widespread use after the U.S. government, responding to a deadly fire aboard a U.S. Navy aircraft carrier during the Vietnam War in 1967, commissioned a handful of major chemical companies to develop a firefighting foam that could quickly and dependably extinguished jet fuel fires. They came up with aqueous film forming foam (AFFF), which contains PFAS. This foam has since been used at military bases, airports and refineries and other industrial and commercial sites all over the world. 

AFFF is made up of a mix of fluorocarbons, surfactants, and solubilizers. The fluorochemical surfactant helps lower the surface tension of water, allowing the foam to create a thin film on top of liquid fuels. This film stops vapours, cuts off the fuel’s oxygen supply, and prevents fuel from evaporating and catching fire again. AFFF was also designed to spread quickly and smoothly over liquid fuel, making it very effective at putting out petroleum hydrocarbon fires.  

However, the environmental impacts and potential health effects of PFAS are under intense scrutiny, and we are seeing the promulgation of PFAS guidance and criteria leading to broader regulations and lower thresholds and standards in Canada and North America, in general.  

Regulatory trends

As the presence of PFAS is already widespread and ubiquitous in the environment, it is key to incorporate “background concentrations” into the assessment, delineation and remediation considerations of impacted sites. 

Of concern is that regulatory bodies, in particular in Europe and the U.S., have continued to lower the acceptable limits for PFAS in water, soil and air at the same time that they have banned or limited their use of AFFF and are moving towards restricting their use in certain consumer products. In fact, the U.S. has set PFAS limits at concentrations that are below what would typically be found in rainwater in rural and remote areas around the country.  

While PFAS-contaminated sites across Canada are at varying stages of investigation, risk management, and remediation efforts, the federal government is starting to initiate regulations and programs to phase out PFAS and transition to safer alternatives, including AFFF. The country is primarily following a risk-based approach, with top priority given to locations where drinking water supplies and other sensitive receptors have been affected.  

In fact, Health Canada has already set an objective of 30 ppt for the sum of 25 PFAS in drinking water, signaling the beginning of tighter regulatory controls to come. 

In the meantime, some provinces are taking the initiative to establish their own PFAS regulations. British Columbia, Alberta and the Atlantic provinces have already implemented a broad set of standards or guidelines, and Ontario has proposed a drinking water screening value for PFAS.  

However, the emergence of varying provincial regulations could lead to the kind of enforcement challenges we’re seeing in the U.S. with their state-by-state regulatory differences. In particular, the federal government is requiring businesses to report on the presence of PFAS in their supply chains by January 29, 2025. Given this regulatory backdrop, many industries are proactively seeking alternatives to PFAS-based products and are phasing out PFAS from their supply chains. This shift is not only a response to government actions but also to heightened public awareness of the health risks associated with PFAS exposure.  

Thus, the demand for, and adoption of safer, environmentally-friendly solutions like fluorine-free firefighting foams (F3s) continues to grow, while a number of countries, including Canada, have been initiating regulatory programs to completely phase out AFFF use. 

Assessing contamination at airports and military bases

The potential environmental liabilities brought on by decades of AFFF use creates a challenge when investigating and evaluating the possible risks to receptors and in developing an appropriate strategy to mitigate those risks when it’s deemed appropriate to do so.  

Regulatory pressure is put on airports and military bases where foam has routinely been used in firefighting and training exercises and each facility may be associated with multiple potential source areas. Because of the persistence, mobility and toxicity of PFAS, they are increasingly the subject of environmental investigations to evaluate the potential risks and determine whether a remediation or risk management strategy should be implemented. 

In Canada, where the investigation of many federal sites like military bases and airports has been conducted across the country, PFAS impacts in source areas have been observed in soil and groundwater. The downgradient impacts from source areas often also include surface waters, sediments, and biota found in streams and ditches that eventually flow into larger water bodies that may represent potential drinking water sources and/or commercial or recreational fisheries.  

These investigation programs have typically extended beyond simply determining whether there is a presence or absence of PFAS to incorporate forensics analyses meant to establish the source of impacts, as well as to make a distinction between any observed site-related impacts and any potential off-site sources or background concentrations. Such forensics programs typically rely on multiple lines of evidence, including evaluating the chemical mixture and concentration gradients of the detected PFAS, as well as looking at the mobility of the PFAS within the context of the site hydrogeology.  

Risk assessments, including evaluating both the potential risks to human and ecological receptors, are also often completed to inform potential mitigation strategies. The use of a risk-based approach that considers exposure and risk from site and background exposures is key, especially given the cost, challenges, and uncertainties associated with remediation of these compounds.  

Remediation strategies

The typical go-to source zone remediation strategy for PFAS-impacted soil is excavation. Materials are typically either stored on site in containment cells or transported and placed in specialized landfills. However, excavation is expensive, energy-intensive, and depending on scale of efforts, disruptive to the local community and not always practical for larger-sized source zones. It is also important to note that simply moving PFAS-laden material from one location to another doesn’t necessarily solve the problem in the long term. 

Source zone treatment involves addressing PFAS impacted soils and the continued leaching of PFAS to groundwater that may represent a risk to receptors downgradient of the source area. The two technologies discussed below offers cost efficient alternatives to excavation and landfilling of PFAS-impacted soils as well as greatly reduces long-term liabilities and potential cost that may be associated with off-site disposal of PFAS impacted soils. 

Soil washing: This volume reduction process involves ‘washing’ soil to transfer PFAS from the soil to the rinse water. This allows for reuse of the soil while the rinse water can be treated using conventional water treatment technologies. Soil washing is being evaluated at several sites in Canada. 

Stabilization and solidification: This approach involves mixing soils, either in-place or after excavation with commercially available stabilization agents like carbon or organo-clay and solidifying the treated soils with cement. The approach reduces the leachability of PFAS by several orders of magnitude and limits the infiltration of water. This particular method is being tested at sites in Canada, including evaluating its effectiveness under a variety of climatic conditions. 

The current de facto water treatment technologies that are being implemented include granular activated carbon and/or ion exchange treatment of PFAS containing water. However, liquids containing high concentrations of PFAS as well as water with more complex chemistry, represent a challenge for PFAS treatment, both in terms of efficiency and cost. A treatment train approach involving separation and concentration followed by destruction offers a solution to the challenge.  

This process, aimed at reducing treatment cost involves separating the PFAS into a small volume of concentrated liquid that can be targeted using a PFAS destructive technology. It takes a lot of energy to destroy PFAS and therefore volume reduction and concentration is key. 

Fractionation is a demonstrated technology to separate and concentrate PFAS. The process involves bubbling the impacted liquid with a gas, typically air or ozone, and taking advantage of PFAS’ preference for the air-water interphase. PFAS will be concentrated in a foam at the top of the fractionation vessels and skimmed.  

The resulting volume reduction may be on the order of 98% and multiple orders of magnitude increase in PFAS concentrations in the “reject.” The “reject” is the focus for destruction. There are multiple destructive technologies on the market at varying stages of development, commercialization, performance and cost efficiency.  

Examples of destructive technologies include sonolysis and supercritical water oxidation (SCWO). Sonolysis uses sound waves to break down the chemical structure of PFAS, while SCWO operates like a high-temperature pressure cooker to destroy PFAS. Whereas SCWO is commercially available, sonolysis is still in the earlier stages of commercialization. At Arcadis, we have been working on a range of destructive technologies in collaboration with some noted academic research partners in the UK and in the U.S. and are currently conducting demonstrations at military bases across North America. 

Transitioning from PFAS

While risk management and remediation can be viable means of dealing with PFAS accumulations in the natural environment, prevention is the key to ensuring no further occurrences happen in the future. In Canada, airports and military bases are transitioning away from AFFF to fluorine-free foams. However, this change is much more complicated than merely replacing one type of foam with another. 

PFAS residues in the AFFF systems are typically very hard to remove and result in significant PFAS concentrations in the new fluorine free foam (F3), so without proper and thorough cleaning or replacement of existing firefighting equipment and fire suppression infrastructure, there will continue to be significant environmental liabilities associated with the fire suppression systems, as well as challenges meeting the evolving regulations regarding PFAS. 

To address this challenge, Arcadis has developed a foam transition process that involves rigorous cleaning of all existing firefighting systems before fluorine-free foams are introduced. The process, which is made up of a five-step program, begins with a cost-benefit analysis on replacing or cleaning the components of a system. It ensures that very little PFAS remain in firefighting apparatus or pipes. As a process, it has been successfully applied at more than 250 sites worldwide over the past eight years.  

In Canada, the federal government has already listed several PFAS chemicals as toxic, banning their import or use, although limited exemptions have been allowed, including firefighting foam. Moving forward, stricter regulations will likely incentivize further reductions in PFAS use across all sectors. The current mandatory reporting requirement for Canadian companies who imported, manufactured, and/or used products containing certain PFAS in 2023 suggests the potential for  more restrictions to come. 

Regulatory developments and industry impact

As Canada takes further steps to regulate PFAS, there are opportunities for industries, airports and military bases to reduce their potential liabilities by transitioning away from PFAS-containing products and prioritizing action on PFAS-impacted sites that pose the greatest risk to receptors. At the same time, mitigation efforts should be driven by a level of pragmatism that limits the potential introduction of high-cost strategies that provide only short-term or inefficient solutions.  

Addressing the problem of environmental PFAS contamination is too large and complex for an isolated approach. Rather, it requires a combination of innovative methods to be brought together by a wide range of stakeholders joining forces to accelerate research and development focused on reducing large volumes of low-concentration PFAS into small, high-concentration waste streams for easier management or destruction.  

Michel France and Jennifer Kirk are with Arcadis.

This article was published in ES&E Magazine’s February 2025 issue.