Cristina Tuser is associate editor for WQP. Tuser can be reached at [email protected].
Sep 01, 2021

PFAS Removal Technologies

Taking a look at the history of PFAS, removal technologies & the future of these contaminants

pfas

Per- and polyfluoroalkyl substances (PFAS) are a group of man-made chemicals that have been manufactured and used in a variety of industries. In the U.S., PFAS have been around since the 1940s, according to the U.S. EPA.

PFAS are used to make fluoropolymer coatings and products that resist heat, oil, stains, grease and water, according to the U.S. Centers for Disease Control and Prevention.

PFAS molecules are made up of a chain of carbon and fluorine atoms linked together, a bond that is one of the strongest ever created. As a result, these chemicals do not degrade, and some of the most commonly used PFAS chemicals like perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have long half-lives. This is where the nickname “forever chemical” is derived from.

There are more than 4,700 known PFAS chemicals that exist and these numbers are increasing.

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How Does PFAS Get Into Drinking Water?

PFAS can enter the environment through waste streams. The EPA gathers that PFAS found in drinking water can be attributed to specific facilities, including manufacturers, landfills, wastewater treatment plants, firefighter training facilities and more.

PFAS are transported through rainwater runoff and enter surface water, or seep through the soil, eventually entering groundwater. This is why when a public water system or private well gets its water from a surface or groundwater source contaminated with PFAS, the chemicals likely enter the drinking water until treatment.

What Does PFAS do to Humans?

There is increasing evidence that exposure to PFAS can lead to adverse health outcomes in humans and animals. PFAS remains in the environment for an unknown length of time, taking years to leave the body. They can be found in our blood and urine.

Based on research conducted by the National Institute of Environmental Health Sciences, health effects of PFAS in humans include: altered metabolism, fertility, reduced fetal growth and increased risk of being overweight or obese, and reduced immunity.

According to EPA, studies show that PFOA and PFOS can cause reproductive and developmental, liver and kidney, and immunological effects in lab animals.

PFOA, PFOS, and especially perfluorohexanesulphonic acid (PFHxS) can eventually reach up to thousands of times higher than the concentrations initially exposed to.

Short-Chain & Long-Chain PFAS

PFAS can either be short-chain PFAS or long-chain PFAS. Long-chain PFAS are often perfluoroalkyl sulfonic acids containing ≥ 6 carbons, and short-chain PFAS have fewer carbons.

PFOA and PFOS were the original long-chain PFAS chemicals that were developed and used widely. The next-generation PFAS chemicals currently in use are another story, however. Even less is known about these next-generation chemicals.

Eric Yeggy is the Water Quality Association’s (WQA) director of technical affairs, and he also coordinates the activities of WQA Water Sciences Committee. Yeggy has years of experience tackling the challenges facing the drinking water treatment industry. He began his career as an analytical chemist in the testing industry, which includes testing drinking water, so his experience with PFAS has been long-standing.

Yeggy has been eager to close the knowledge gap via ongoing research of these chemicals, and work with his colleagues to provide WQA members and the public with resources needed to protect drinking water.

“So in the industry, those were all phased out voluntarily (PFOA and PFOS) by 2015 in the U.S. market, those two were, but the industry then switched to these newer generation PFAS chemicals, which are shorter-chain in many cases,” Yeggy said.

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Can You Destroy PFAS?

EPA is considering multiple disposal techniques for PFAS removal, including incineration, to treat and dispose of PFAS waste.

PFAS compounds are difficult to break down due to strong carbon-fluorine bonds. In the event of incomplete destruction of PFAS compounds, the outcome may be the formation of smaller PFAS products or products of incomplete combustion (PICs).

“They call it the forever chemical because there’s really nothing in nature that can destroy this chemical,” Yeggy said. “It’s a man-made chemical that cannot be destroyed by natural mechanisms in the environment.”

Can You Treat PFAS in Drinking Water?

There are a few technologies that have been widely tested for PFAS removal, including reverse osmosis (RO), granular activated carbon (GAC) filters and ion exchange. All three come in point-of-entry (POE) configurations.

If you need a point-of-use (POU) solution, such as something that would go under the counter or sink, RO or filters are an appropriate option.

“In terms of effectiveness, this really comes down to the type of PFAS chemical that you’re treating for,” Yeggy said. “So the first thing is obviously always test the water to understand what PFAS chemical you’re dealing with, what the concentration is, so that you know which treatment is going to be effective. In general terms, the short-chain PFAS chemicals are more difficult to remove than the long-chain PFAS chemicals.”

PFAS chemicals can also be sulfonated or non-sulfonated. So short-chained, non-sulfonated would be the most difficult to remove. As a result of these variations, there is no one size fits all solution.

This is where the future of regulation comes into play. Regardless of the current status of PFAS regulations, there are a few PFAS contamination treatment methods widely studied and trusted for use.

Cathy Swanson, groundwater remediation specialist for Purolite, received a Bachelor of Science in Chemical Engineering from Northwestern University. Swanson has more than 20 years of business leadership experience, as well as a background in water treatment, specifically in treating drink water and groundwater remediation. Swanson’s work has delved into expanding current technologies for water treatments and tackling perchlorate, PFAS, nitrate, arsenic, softening, metals removal and more with resin technology.

“We’re going to have better data on toxicity, we’re going to have more guidance from the EPA,” Swanson said about the future of PFAS and removal methods. “And understanding which of the PFAS we need to get out is going to really help homeowners decide what treatment and how often they need to replace the media.”

Reverse Osmosis (RO)

With the longer-chain PFAS chemicals, RO is the ideal solution for PFAS removal.

Under-sink RO filtration is an option that is highly revered, as it has all plastic piping between you and the drinking source, so metal is not leaching out of the pipe and further impacting the water supply.

“With whole-house RO, you create a very aggressive water. The water needs to be remineralized, or it will leech, for example, copper out of the pipe,” Swanson said. “While RO is great at removing everything, it also removes everything. The advantages are that if you have multiple contaminants, it will take stuff out. It’s good for high total dissolved solids (TDS) water.”

From a sustainability standpoint, the PFAS water is not captured and therefore not ingested, and instead sent back to a wastewater treatment plant, according to Swanson.

Granular Activated Carbon (GAC)

Using granular activated carbon to remove PFAS entails the PFAS sticking to the small pieces of carbon as the water passes through. Because activated carbon is a highly porous material, it provides a large surface area for chemicals to be adsorbed.

GAC is abundant and takes out other organic contaminants, but a disadvantage is that it takes a 10 minute empty bed contact time, and the filters needed are large.

GAC removes chlorine from influent water, but if the vessel is left sitting for too long without flow on a consistent basis, bacteria can form. GAC works well on longer-chain PFAS, like PFOA and PFOS, but does not adsorb shorter-chain PFAS as well.

Ion Exchange Resin

Another technology that can treat PFAS in water is single-use ion exchange resin. Small beads (resins) made of hydrocarbons allow the chemicals to stick to the beads and be removed as the water passes through.

According to Swanson, with the resin, you can get fluffing of PFAS off of the resin. Other organics in the water, such as total organic carbons (TOCs) and even long-chain PFAS, will push off the smaller chain PFAS to levels that are twice the influent level in some cases, subjecting the water to additional hazards.

Ion exchange has a few advantages, however, the first being that it has a much smaller footprint compared to GAC. The resin typically has a longer bed life than the carbon, but it’s necessary to have a carbon filter in front of it or a layered bed in order to capture chlorine.

Ion exchange is less likely than GAC to pick up bacteria, but it is still possible and therefore important for the water not to remain idle. With ion exchange resins, it is possible to take out all of the short-chain chemicals and get the PFAS non-detect, but this is dependent on the water quality.

There are other technologies that researchers are working on and need to widely test.

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How Can You Test for PFAS?

Testing for PFAS in drinking water is often a simple process. The EPA recommends testing be conducted by collecting clean water samples, and to always use laboratory-provided, PFAS-free containers.

“I’ve heard estimates as high as 10,000 different PFAS chemicals, but more common estimates are somewhere exceeding 4,000 PFAS chemicals,” Yeggy said. “So there’s a lot of different PFAS chemicals out there, and I guess the thing we initially struggled with was a lack of information on what those chemicals were, so that we could actually do testing to see which of them could be successfully removed by which technology.”

How are water treatment dealers facing the challenge of treating PFAS? It is no easy feat, but with time and technology the understanding of PFAS has progressed, empowering water treatment dealers to better tackle its customers’ water treatment needs and face these contamination issues head-on. Before PFAS captivated the attention of the general public, many water treatment dealers had already anticipated that PFAS would be at the forefront of water issues.

SLOwater, a water dealership located centrally in Los Osos, California, was one such water dealer. When this dealership started finding and dealing with PFAS in the area, the water dealership seized the opportunity to tackle the rising contaminant concern by obtaining PFAS-certified filters.

Eric Foronjy, sales manager for SLOwater, then pursued emerging contaminant sampling training to learn more about this national concern and how to adequately test and treat it, describing this training as “elaborate, training and expensive.”

When Foronjy first began working for the dealership in 2001, the conversation around PFAS was at first minimal, but then quickly became of more concern as the water industry began to learn more about emerging contaminants and technologies.

Foronjy recounts one of his first experiences with testing and treating PFAS.

“I had a client who kind of brought a property behind what used to be a septic collective station for an entire neighborhood, and so the leach fuel from that effluent was basically his property that he then purchased, then he purchased the project adjacent to it,” Foronjy said. “So the city started doing emerging contaminant testing in his well, even though it’s private, and they found pretty high levels of PFAS.”

Once the county did additional testing at its site after SLOwater installed a PFAS filter, and the results of this testing showed that PFAS was non-detectable, the SLOwater team knew this issue would become more common.

The cost to test for PFAS is also determined by the method used for testing. EPA has created methods 533 and 537.1, so both government and private laboratories can now measure 29 types of PFAS in drinking water.

Method 533 determines if there is PFAS in drinking water by isotope dilution anion exchange solid phase extraction and liquid chromatography/tandem mass spectrometry. Method 537.1 measures PFAS by solid phase extraction and liquid chromatography/tandem mass spectrometry.

What is a Safe Level of PFAS?

EPA has established health advisory levels at 70 parts per trillion (ppt) for PFOA and PFOS in drinking water, but there is no real “safe level” of PFAS. These health advisory levels are non-enforceable and non-regulatory.

In April 2021, the EPA released an updated toxicity assessment for perfluorobutane sulfonic acid (PFBS), a member of a larger group of PFAS.

“To single out any one compound, to say this one’s dangerous and this one’s not, is not always easy. And then to put that into a matrix across 5,000 chemicals becomes very difficult,” said Swanson.

Non-detectable levels are the goal, but this is not always achievable. Although the EPA has not yet enacted a maximum contaminant level (MCL) for any PFAS, many states are taking matters into their own hands to propose drinking water regulations for PFAS.

About the author

Cristina Tuser is associate editor for WQP. Tuser can be reached at [email protected]

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