Recent attention from mass media outlets has sparked concerns about forever chemicals in Australia’s water supply – but there’s a few myths that need to be busted.
PFAS, or per- and polyfluoroalkyl substances are a group of man-made chemicals that are commonly used in products that are resistant to heat, grease or water – such as non-stick pans, waterproofing and firefighting foams.
Often dubbed ‘forever chemicals’, PFAS don’t break down in the environment, they are highly mobile and they’re very difficult to remove once they enter a waterway.
So, are they in our drinking water?
For those not in the know, when these reports are talking about PFAS traces being detected, they’re talking about source water, such as dams or reservoirs, which undergoes extensive treatment before it enters the potable water network.
However, not all treatment methods can effectively remove PFAS from water, and with new drinking water guidelines on the horizon we turned to an industry expert to get some practical advice on just how utilities can tackle these chemicals.
Forever is a long time
As the fourth generation to lead this family business, James Cumming and Sons Managing Director, John Cumming, grew up in the water industry. With multiple diplomas and certifications in water treatment under his belt, Mr Cumming has spent more than a decade helping water authorities solve filtration challenges.
For Mr Cumming, it’s important that the community sees and understands the constant work that water authorities are putting in to keep PFAS out of our drinking water.
“They’re very conscious of [the risks] and a lot of water authorities are regularly engaging with people like us to [constantly improve] the way they tackle that issue. They’re going through options for [both] assessments, and [for the best way to treat] different levels of PFAS,” he said.
Water authorities regularly test both treated and untreated water supplies, and many utilities not only share these results publicly but also commit to a very high standard for testing procedures.
To further tackle this issue, the National Health and Medical Research Council (NHMRC) released draft update to Australian Drinking Water Guidelines on PFAS in late 2024, which proposes an even wider safety margin for the acceptable levels of four different PFAS.
Although at this stage these guidelines are a draft only, Mr Cumming said it’s important that water authorities are equipped with the right knowledge to make the best decisions they can about how they treat their water.
“PFAS is a group of compounds with a molecular structure that is characterised by either a long- or short-chain carbon-fluorine bond,” he said.
“The most prevalent source of PFAS in Australia comes from AFFF foams, particularly around defence sites and because these compounds are highly mobile, they infiltrate soil and groundwater, and then pass into our waterways. Their use through non-stick cookware, Tupperware and clothing also means that they circulate within our wastewater network.
“Because they are ‘forever’ chemicals, there is no natural biodegradation process and circulate until they either find a stable home or are removed from the network [via the treatment process].
“The challenge is that conventional treatment processes and infrastructure aren’t necessarily geared toward treatment of PFAS.”
Mr Cumming explained that the unique molecular structure of a carbon-fluorine bond – as opposed to a carbon-hydrogen bond – makes these compounds thermally and chemically stable.
PFAS are hydrophobic, but the heads of these compounds are also water soluble, which makes them very transferable through water and soil, and therefore they’re difficult to treat and highly mobile, In other words, they are amphiphilic.
“The biggest challenge with PFAS compounds is that they can’t be removed through, coagulation, flocculation, clarification, filtration, disinfection and pH adjustment – which make up the typical treatment train of a water treatment plant,” Mr Cumming said.
According to Mr Cumming, the most economical way to actually destroy PFAS is to break down the carbon-fluorine bond, which usually requires it to be heated to more than 1100°C. There are other destruction methods but nothing yet presents a economically viable method.
“There’s not that many places that can perform thermal destruction of compounds in the first place, and you obviously can’t just boil water at 1100°C to destroy PFAS,” he said.
“So, what you’re doing with treatment technologies is just containing the compounds themselves and moving them somewhere where they don’t end up in our environment, activated carbon does that.”
Treat them right
To meet the proposed new Drinking Water Guidelines, PFAS must be barely present in treated water, and according to Mr Cumming, the first step to hitting these targets is to establish a baseline and closely monitor water pre- and post-treatment.
“Then, [they’d need to] upgrade or retrofit plants with the advanced treatment techniques to meet the guidelines,” he said.
“The most common technologies used to remove PFAS from water are ion exchange resins, reverse osmosis (RO) and activated carbon, and [utilities should conduct] a cost–benefit analysis to find [the one that’s best for them].”
Granular activated carbon (GAC) and powdered activated carbon (PAC) are often the most cost-effective way to remove most, if not all, PFAS compounds depending on their chain length and molecular weight.
Mr Cumming explained that RO systems and ion exchange resins are effective, particularly as polishing steps for industrial wastewater treatment, but require a bigger investment and come with additional challenges in terms of maintenance and regeneration.
“GAC also needs to be replaced when it’s determined that breakthrough levels have exceeded guidelines, but RO and ion exchange resins require often burdensome additional infrastructure, whereas if the current filter beds are deep enough, and allow enough contact time, GAC will remove PFAS,” he said.
Chemical attraction
As there are thousands of PFAS variants, with different chain lengths and chemical structures, Mr Cumming said the right solution must be selected for effective treatment.
“[First of all] not all filters remove PFAS, and there can be some confusion between our filter coal and activated carbon. With filter coal, particles get trapped between the granules themselves, and it is very good at removing turbidity and particulates [but not PFAS].
“Whereas activated carbon both filters out turbidity and adsorbs compounds through Van der Waals forces, where these compounds adsorb to the pores within the granules.”
There are also different raw materials that are used to make activated carbon, and Mr Cumming said that coal, wood and coconut shell are the most common.
“Each of [these materials] have varying pore sizes and because a lot of PFAS, especially the ones in firefighting foams, tend to be larger molecules with longer chains you want more of a macro and meso porous structure – so coal-based carbons are typically more effective than coconut or wood-based carbons,” he said.
“[But] not all coal-based carbons are created equal, with variation on raw material source, manufacturing and activation technique and particle size grading.
“We focus on premium Australian coal, which gives us some advantages in terms of how the pore structure is formed within the carbon. The activation process [plays a big role] and the residence time that our coal spends in the activation kilns is longer compared to traditional activated carbon manufactured overseas, which gives it a uniquely Australian pore structure.”
Even with the best product at your disposal, Mr Cumming said that this method is only effective if the water is in contact with the activated carbon for the right amount of time.
“The longer the contact time, the better or more likely, the PFAS is to be removed,” he explained.
“A lot of conventional treatment plants already have a filtration system, and if they have sufficient bed depth, they can just retrofit GAC in a similar profile to what they’re currently using to be able to treat PFAS.”
If a facility does not have the sufficient bed depth for GAC, then they can use PAC to tackle PFAS, but it can be more difficult to ensure enough contact time with this approach.
“Essentially, if you’re wanting a cost-effective method of removing PFAS in water, typically GAC will be the first line of defence,” Mr Cumming said.
“PAC can also be used, but as it’s a dosed product, and PFAS levels tend to vary in the water, GAC is often going to be more effective because it can be saturated over time. Whereas PAC will be filtered out with other turbidity and not sustained within the treatment train.
“But [before we recommend any product] we’ll usually work with a water authority and supply samples for them to perform jar testing or pilot plant work to help them substantiate the effectiveness and value of our product for their specific plant or application. U
