Where do we get exposed to PFAS and how can we remove them?

In October, the National Health and Medical Research Council invited public consultation onnew draft limits for 'forever chemicals'— also known as per- and polyfluoroalkyl substances, or PFAS — found in Australia's drinking water.

The draft guidelinespropose lowering the limit for three PFAS compounds and setting a new value for a fourth.

PFAS can bioaccumulate in the human body, meaning their concentrations can increase over time through repeated exposure. They are linked topossible increased risk of cancers, changes in the functioning of hormone and immune systems, and adverse developmental effects.

But while much public attention has been focused on PFAS in Australia's drinking water supplies, the issue of PFAS contamination, and what we can do about them, is much broader than the contamination of drinking water alone.

What are PFAS?

PFAS are a class of about 12,000 manufactured chemical compounds. A few, with known health impacts, are regulated.

PFAS compounds are similar to plastics and hydrocarbons, except they contain carbon-fluoride bonds that are strong and stable, making the compounds more difficult to biodegrade and destroy.

They are similar in form to surfactants or detergents, meaning they often collect at surfacesto make products water-, stain- and grease-resistant.

They are also good at stabilising emulsions and foams. Combined with their ability to withstand high temperatures without breaking down, this has made PFAS useful as firefighting foams.

Their unique properties mean they have foundapplications in a diverse range of products: from packaging including food packaging, body care products like shampoos, cosmetics including nail polish, and mobile phones, to name only a few.

The ubiquitous use of PFAS mean they are also integrated into the supply chains of many products.

For example, they are currently used in the production of computer chips, although efforts are underway to reduce oreliminate this reliance on PFAS.

But it's not just the present uses of PFAS but also their history that we need to contend with.

Where might elevated levels of PFAS be found?

Most sites initially under investigation for elevated levels of PFAS in Australia were associated with PFAS from firefighting foams.

While the use of PFAS as a fire suppressanthas been phased out, thepersistence, bioaccumulation and environmental toxicityof PFAS compounds means these sites are legacy issues for Australia to manage.

Historical use of these foams by the Australian Defence Force led to PFAS-contaminated land at Williamtown in New South Wales and is linked to80 percent higher rates of kidney and lung cancersthan those of other areas without PFAS contamination.

Aclass actionagainst the Department of Defence on behalf of about 500 Williamtown residents was launched in 2016.

The pervasive use of PFAS in a variety of products has also led to a build-up of the chemicals in our waste systems.

Elevated PFAS sites now includelandfills,wastewater treatment plantsthat concentrate PFASin the biosolids or treated sludge that they produceand industrial sites that use PFAS compounds in the production process.

PFAS contamination primarily occurs in soil, but can also transfer to water bodies via water circulation. Therefore, cleaning up PFAS-contaminated soils is an important thing we need to do.

What can we do about PFAS?

Severalsoil PFAS treatment or removal methods, such as turning PFAS-contaminated soil into concrete, thermal treatment or biodegradation and oxidationhave been proposed.

However, the significant drawbacks of these methods — such as the risk of secondary contamination if PFAS leak from the concrete, the high costs of heating huge amounts of soil, and the generation of a more toxic chemical after biodegradation and oxidation —restrict their practical large-scale applications.

The US Environmental Protection Agency's interim guidance onthe destruction and disposal of PFAS and PFAS-containing materialsrecognises three processes for managing PFAS-contaminated waste.

Two involve containment of the PFAS contamination: for example, underground disposal in a contained aquifer or disposal in a secure landfill.

The third method is high temperature thermal destruction in an incinerator.

Currently, destruction at over 1,000 degrees Celsius for two seconds is required to ensure complete destruction of PFAS and a licence is required to operate such facilities in Australia.

Consequently, most current treatment approaches focus on containment methods while they find an economic destruction process.

In Australia, destructive treatment generally involves concentrating PFAS from water or extracting it from soils in concentrated form, followed by transport to a licensed facility for destruction. The costs of transporting and incinerating PFAS are much lower if PFAS is concentrated.

New developments to help remove PFAS

Over the last few years, scientists have developed a range of ways to make PFAS removal more cost-efficient and effective.

The use of 'adsorbents' — solid substances to which other substances stick — has become common in PFAS removal.

Adsorbents such asactivated carbon or an adsorbent resinare often used to isolate PFAS from water; the PFAS are essentially trapped by the activated carbon or resin. Research is now being conducted to find ways toregenerate these adsorbents afterwardsto reduce costs still further.

Gas fractionation for PFAS contaminated water is a physical method that exploits the chemical properties of PFAS to separate different PFAS substances from water. It is nowcommercially availablefromseveral suppliers. More recently,gas fractionationmethods usingenhanced soil-washing technologyhave been developed for PFAS removal.

EGL Water in 2022built a pilot gas fractionation plantwith a treatment capacity of 300 kilograms a day for PFAS-contaminated soil in Laverton, Victoria.

Results have shownthat gas fractionation technology improves the efficiency of PFAS removal by over 500 percent compared with water extraction alone. And the process allows for over 80 percent of the extraction water to be recycled to be used for extracting PFAS from soil again.

The high concentration rates achieved with gas fractionation lowers the cost of PFAS treatment. Over the next few years, further demonstration and verification of technology will likely build confidence in the technology's adoption.

Water authorities are also investing inbiochar technology.This technology aims to remove PFAS from wastewater treatment plant biosolids, to enable beneficial use of biosolids as biochar (a charcoal-like substance that contains no petroleum). The technology is moving to thedemonstration phase.

Efforts to achieve destruction of PFAS compounds in situ, rather than transporting these chemicals, is another focus of research.

These approaches includedestruction of PFASusingnovel catalysts,plasma destruction of PFASandbiodegradation of PFAS.

Research published in November shows scientists are also turning tolight-activated catalystsas a way of breaking down PFAS. While these efforts directed to in-situ degradation show varying degrees of promise, none of these approaches are yet practiced commercially.

For now, PFAS's legacy remains unresolved in many locations.

This content is originally published under the Creative Commons license by 360info™. The Ground Report editorial team has made some changes to the original version.

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