As the Australian Government launches a $2 billion lawsuit against 3M for damages related to PFAS chemicals, engineers are being tasked with solving the environmental and health fallout.
The consensus emerging from engineers, researchers and regulators around remediation of the enormous per- and poly-fluoroaklyl substances (PFAS) challenge is that there will never be a single solution.
Grant Scott FIEAust CPEng EngExec, Principal Consultant at Ambiolock, former Chair of Engineers Australia’s Chemical College and former Victoria Division President, describes the PFAS contamination as “the new asbestos”. But it goes further than that, because it can persist, migrate and create long‑term exposure pathways.
As with asbestos, there are growing concerns about the long-term human and ecological impacts effects of PFAS exposure.
In a class containing more than 12,000 chemicals, various PFAS compounds behave differently. It’s a class so wide-ranging that there is no agreement around the definition of a PFAS substance.
The simplest explanation is that PFAS in liquid form can do what seems impossible. Sprayed onto a fuel fire, rather than sizzling and evaporating, they instantly spread across the fuel like a thin blanket, cutting off oxygen supply and killing the fire fast.
PFAS molecules travel readily in water and at the same speed as water. Their unique properties have also seen them used on non-stick pans, waterproof jackets, stain-resistant carpets, fast-food packaging and more.
The greatest challenge lies in their persistence and ability to bind within materials, and move through surrounding environments. This is also what makes it such a problem to clean up, particularly in areas where it has been used in firefighting and firefighting training, including airports and defence bases, and in the surrounding soil and water.
READ: Saying farewell to forever chemicals
Start at the PFAS source
Most importantly, Scott said, the historical use of PFAS-based firefighting foams has largely ceased. The next most logical challenge is to control the contamination at its current source on Defence bases, at airports and elsewhere.
“From an engineering and cost perspective, the further PFAS migrates, the more expensive it generally becomes to manage,” Scott said. “Long-term groundwater treatment, disposal and destruction pathways can become very costly and operationally intensive.”
As most fire training exercises using PFAS chemicals took place on concrete surfaces, PFAS molecules were drawn deeply into the permeable concrete surrounds and soil. If these concrete stands are broken up and taken away in their current form, or are recycled for use as aggregate, they continue contaminating and creating exposure risks.
Engineering responses to PFAS contamination include source control, containment and material treatment approaches. Ambiolock technologies are examples of these approaches:
- Ambioseal is a penetrative treatment that prevents contamination leaching into soils, groundwater and surface waters by 98-99 per cent for up to 20 years, Scott said. The product penetrates deep into porous concrete, sealing any potential PFAS exits.
- Used with contaminated structural materials including concrete, bricks, gravel, asphalt, rock and sand, Ambiolock is mixed in with PFAS-impacted materials for recycling. After crushing and treatment, the recycled aggregate is then used in a new concrete substrate.
- Ambioprotect is for new concrete areas close or exposed to contamination, to stop the concrete being contaminated.
In every case, these products work by sealing and strengthening the concrete to which they’re applied, preventing further leaching of PFASs into the surrounding environment.
READ: Innovative methods for tackling PFAS contamination
Digging deeper
Soil that has experienced PFAS contamination can be treated or repurposed. Soil washing, essentially an industrial cleaning process, involves running the excavated soil through a wash of water and solvents to separate PFAS from the soil particles.
A 2024 study reported in the Journal of Hazardous Materials said the most effective washing efficiencies came from anything from a 0 per cent solvent mix – meaning water only – up to a 5 per cent solvent mix.
Other processes include the energy intensive superheating of the soil to break the strong carbon-fluorine bonds of PFASs via thermal desorption.
One study from East Carolina University found that “soil concentrations of PFASs showed a significant decrease at 350°C … by, on average, 43 per cent and 79 per cent in the fortified and field contaminated soils, respectively. At 450°C, >99 per cent of PFASs were removed from the fortified soils, while at 550°C the fraction removed ranged between 71-99 per cent for the field contaminated soil.”
Water treatment
When PFASs are in the water supply, PFAS molecules must be removed using filtration or adsorption processes.
Sydney Water, in its Cascade plant supplying water to parts of the Blue Mountains, uses granular activated carbon (GAC) and ion exchange resin to remove PFAS.
GAC involves pushing the water through activated carbon, which is highly porous and therefore has a large surface area. PFAS molecules stick to the carbon.
This method can be 100 per cent effective at removing PFAS molecules from water, depending on variables such as carbon depth, flow rate, temperature and competing contaminants, the American Environmental Protection Agency reported.
Ion exchange is a similar process using positively charged, engineered resin beads to attract and capture the negatively charged parts of PFAS molecules.
Other water treatment processes can include reverse osmosis similar to the desalination process, foam fractionation where air is bubbled through the water and PFAS molecules collect in the air bubbles in the foam on the surface because they are surfactants.
A study published in Remediation journal, commissioned by the Australian Department of Defence, found foam fractionation more than 99.5 per cent effective in removing three major types of PFAS from contaminated groundwater.
READ: Emergency floodwater treatment yields PFAS solution
PFAS separation is not the end
Whatever processes are used for treatment of hard surfaces, soil and water, the fact remains that any separated PFAS molecules or contaminated concrete, soil or water must still be destroyed. If not, it will continue to contaminate – hence the term forever chemical.
Scott said the most effective way to do this is through high-energy, high-temperature destruction methods, such as specialised incineration more than 900°C, or thermal treatment.
For this reason and more, Scott said, an important engineering focus is reducing mobilisation and exposure pathways at the source.
“Engineering measures that reduce PFAS mobilisation and environmental exposure pathways also contribute to limiting long-term human and ecological exposure risks.
“While there is still much work to be done, practical measures that reduce ongoing release into soils, groundwater and receiving environments are an important part of protecting communities and supporting long-term health and environmental outcomes.”
Wish to thank the Author for this timely article.
I would be thankful if the Author could whrite another article elaborating the Health and environmental risks caused by PFAS.
Or else one may think that do nothing could be an option.