Water treatment plants can remove PFAS contamination, but there's a catch (2025)

"Forever chemicals" are almost impossible to avoid. They can be found in clothes, cosmetics, furnishings, non-stick cookware, food packaging — and, in rare occasions, end up in water from the kitchen tap.

The chemicals, technically known as per- and polyfluoroalkyl substances or PFAS, encompass a class of more than 14,000 synthetic compounds.

As their nickname suggests, forever chemicals persist in the environment, taking hundreds to thousands of years to naturally break down, and there are growing concerns about their potential health effects in humans.

One environmental source of human exposure to PFAS is drinking water, according to the World Health Organization.

In Australia, PFAS levels were recently found exceeding national drinking water guidelines in two dams in the Blue Mountains and bore water in north-east NSW.

There is currently a NSW inquiry into PFAS contamination in waterways and drinking water; and a national inquiry investigating the sources, potential health and environmental impacts, and the role of regulation.

The National Health and Medical Research Council is also reviewing its 2018 guidelines around safe levels of PFAS in drinking water.

Draft guidelines released last year proposed significantly lowering safe levels for some types of PFAS, with the final guidance due in April.

The new limits mean some of Australia's water supplies may not comply if the draft guidelines stand.

So what's involved in cleaning PFAS out of our waterways?

Removing PFAS from contaminated water sources isn't necessarily difficult, according to Denis O'Carroll, an environmental engineer and director of the UNSW Water Research Laboratory.

It depends on the scale and complexity of the contamination site, water quality parameters, and, of course, the cost.

"It would be very costly if you wanted to remove PFAS from stormwater as an example," he said.

"But to remove PFAS at drinking water treatment plants, it's relatively straightforward."

So when PFAS is detected in a town's drinking water supply, how is it removed?

Cleaning PFAS-contaminated tap water

Conventional drinking water treatment processes include adding chlorine or chlorine-containing substances to kill microbes, or rapid sand filtration, where water flows through coarse sand to filter out impurities.

While these techniques can effectively deal with bacteria and other nasties, they cannot remove PFAS from contaminated water. But there are other processes that can, Professor O'Carroll said.

Two widely used and effective PFAS remediation technologies in water treatment are called granular activated carbon and ion-exchange resin.

Granular activated carbon is the most-studied PFAS-removal treatment. It is a highly porous, carbon-rich material with a large surface area that traps PFAS molecules, effectively removing them from the surrounding water.

A second technology is ion exchange resin, a positively charged material that attracts and holds onto the negatively charged parts of PFAS molecules. It's more expensive than activated carbon but can remove more PFAS types.

Another water treatment technology is called foam fractionation.

It involves gas (typically air) being bubbled through a liquid to produce a "PFAS-enriched foam on the surface" that is then removed, explained Ian Wright, a water scientist at Western Sydney University.

While it's not routinely used in water treatment plants, it can remove PFAS from, for instance, contaminated groundwater.

Dr Wright pointed to a2021 Australian study that found foam fractionation removed at least 99.5 per cent of three common types of PFAS from contaminated groundwater.

This system also used an ion exchange resin "polisher" to remove all trace detectable PFAS molecules from the water following the foam fractionation treatment.

The effectiveness of a PFAS-removal technology also depends on how well a drinking water treatment plant is managed and maintained, Dr Wright said, adding that its performance should be "regularly tested".

However, there is a catch to such PFAS removal techniques.

"The issue with them is that they don't destroy the PFAS molecule," Professor O'Carroll said.

"It just concentrates them on the activated carbon or the ion exchange resin, and then you have to do something with that PFAS-laden activated carbon or ion exchange resins."

Commercial companies that use these technologies must dispose of that by-product, he said.

For example, the liquid waste could be sent to an incinerator or a landfill — but those are expensive options which, in turn, pose another set of contamination risks.

"What engineers and scientists like me are trying to do is develop technologies that can break apart the PFAS molecule, but we're not quite there yet," Professor O'Carroll said.

"PFAS is really, really hard to break apart."

His research team at UNSW has been developing a new system using zinc and vitamin B12 to degrade PFAS chemicals.

"[Other] people at UNSW are also looking at using microbes to degrade PFAS, and we can degrade some PFAS, but certainly not all," he said.

Can I remove PFAS from water at home?

You can, but according to Dr Wright, it's "probably wasted money" if your drinking water supplier can reassure you that it has low PFAS concentrations — "ideally consistent with the tough US EPA guidelines", which are stricter than current Australian guidelines.

If you really wanted a home PFAS treatment system, he suggested a reverse osmosis, dual-stage filter installed "under the sink".

Reverse osmosis forces water through semi-permeable filtration membranes, producing clean water separate to a waste liquid often referred to as "brine".

"There are lots on the market and they can be used as 'bench top' or 'under the sink' systems that are installed by a plumber," Dr Wright said.

"But all systems will need to be carefully maintained. Filters do need to be maintained and regularly replaced."

Along with installation, this can be very expensive.

A simple bench-top activated carbon filter system will cost between $100 and $200, while under-sink reverse osmosis systems are pricier, ranging from $400 to more than $1,000. Replacement filters each cost between $30 and $80.