- Small and rural water systems face much higher treatment costs per gallon than large utilities.
- Ion exchange generally has lower costs and environmental impacts than granular activated carbon.
- Short-chain “forever chemicals” can be especially difficult and expensive to remove.
- Water quality can change, which affects which treatment method performs best.
- The study evaluated treatment at 82 U.S. drinking water systems.
- Researchers cautioned that their models have important limits.
Wednesday, October 7, 2026 — Removing “forever chemicals” from drinking water may be especially difficult for the smallest communities, according to a new nationwide study of water treatment systems.
The research, published in Nature Communications,
compared two widely used methods for removing per- and polyfluoroalkyl substances, commonly called PFAS or forever chemicals, from drinking water. Researchers examined both the financial cost and the broader environmental impacts of treatment.
One finding stood out: size matters.
Small and rural water systems can face much greater treatment burdens than large utilities because equipment, materials, and operations costs are spread across far less water.
The researchers identified utility size as the “overarching driver” of economic and environmental performance. They also found that the type of PFAS in the water and the quality of the source water can make a major difference.
Two Ways to Capture Forever Chemicals.
The study focused on two established PFAS treatment technologies.
The first is granular activated carbon. In simple terms, contaminated water passes through carbon material that captures PFAS and other chemicals.
The second is ion exchange resin. This method uses specially designed resin to capture PFAS as water passes through it.
Neither method destroys the PFAS. Instead, the contaminants are separated from the drinking water and collected in the treatment material.
That distinction is important. Technologies that could actually destroy PFAS are being studied, but the researchers said questions remain about their cost, ability to operate at large scale and possible byproducts. For now, separation technologies such as activated carbon and ion exchange offer a more practical route for many water utilities.
Small Systems Pay More.
Researchers modeled water systems ranging from very small facilities treating about 30,000 gallons per day to large utilities treating roughly 75 million gallons per day.
Scale made a major difference.
A large treatment plant can spread the cost of equipment, energy, and treatment materials across millions of gallons of water. A tiny system cannot.
As a result, the smallest utilities generally had the highest costs for each unit of water treated. They also tended to use more materials and energy per unit of treated water.
The study found that costs generally fell as the amount of water being treated increased.
That finding could be particularly significant for small and rural communities because those systems may have fewer customers to spread treatment costs across.
The researchers concluded that “small and rural systems face disproportionate burdens” and said targeted financial and policy support may be needed.
Ion Exchange Often Came Out Ahead.
Across most of the scenarios examined, ion exchange performed better than granular activated carbon when researchers considered both cost and environmental effects.
In the initial comparisons, ion exchange consistently produced a lower global warming impact than activated carbon.
The researchers later examined nine different categories of environmental effects. Ion exchange had lower impacts than activated carbon in eight of the nine categories for both very small and large utilities.
The exception was ozone depletion potential. Ion exchange had a higher impact in that category, particularly when treating one of the short-chain PFAS studied.
Activated carbon also offers benefits that simply declaring one technology the winner cannot capture. The researchers noted that activated carbon can remove organic matter and a broad range of other trace contaminants, while PFAS-selective ion exchange resin is designed specifically to target PFAS.
Some Forever Chemicals Are Harder to Remove.
Not all PFAS behave the same way.
The researchers compared several different compounds, including long-chain and shorter-chain chemicals. One of the shorter-chain compounds, perfluorohexanoic acid, proved substantially more expensive to remove with ion exchange.
At the largest utility size studied, its ion-exchange treatment cost was more than five times the cost calculated for perfluorooctanoic acid, a better-known long-chain PFAS.
The reason comes down to chemistry.
The shorter-chain compound does not stick as readily to the treatment resin. That means a utility may need more treatment material or may have to replace the material more frequently.
Activated carbon also had higher costs for the shorter-chain compound, although the difference was less dramatic.
The researchers cautioned that some PFAS with even shorter chemical chains than those modeled may be still more difficult to remove.
The Water Itself Matters.
Treatment costs are not determined only by how much PFAS is present.
The researchers found that the water surrounding the PFAS can be just as important.
This was particularly true for granular activated carbon.
Surface water can contain naturally occurring organic material. That material competes with PFAS for space on activated carbon. As the amount of organic carbon in the water rises, the treatment material can become less effective, increasing both costs and environmental impacts.
Ion exchange was much less affected by organic carbon in the study.
That means a treatment technology that performs well for one water system may not necessarily be the best choice somewhere else.
Groundwater and surface water can produce different results, and local water chemistry can change the economics of treatment.
Researchers Examined 82 Water Systems.
The nationwide portion of the study modeled treatment at 82 U.S. drinking water systems where measured concentrations exceeded the 4-nanogram-per-liter level used for perfluorooctanoic acid and perfluorooctane sulfonate.
Of those systems, 48 relied on groundwater and 34 relied on surface water.
The analysis produced an interesting result: the concentration of PFAS itself was not necessarily the biggest factor determining treatment cost.
Utility size and water quality often mattered more.
For example, Pine Valley, California, had a reported perfluorooctanoic acid concentration of 181.4 nanograms per liter. Despite that comparatively high concentration, its modeled treatment costs remained below those calculated for some very small systems elsewhere in the country. The researchers attributed the broader pattern primarily to differences in system size and water quality rather than PFAS concentration alone.
Reno, Nevada, was another western system included in the analysis. The study used a population of 442,000 customers and a perfluorooctane sulfonate concentration of 13 nanograms per liter for the surface-water system. Its estimated median activated-carbon treatment cost was 19 cents per cubic meter of water.
New Mexico Was an Exception in the Dataset.
One finding deserves careful interpretation.
Six states, including New Mexico, were excluded from the study’s city-level comparison because the dataset did not contain cities in those states reporting PFAS concentrations above the regulatory thresholds used in the analysis. The other five were North Dakota, Louisiana, Iowa, Hawaii and Arkansas.
That does not mean PFAS are absent from those states. It describes only what was reported in the dataset used for this particular analysis.
Treatment Creates Another Problem: What Happens to PFAS?
Capturing PFAS does not make the chemicals disappear.
Once activated carbon or ion exchange resin has collected PFAS, the spent material must be handled.
For its calculations, the study assumed that used carbon and resin would ultimately be sent to a landfill. The distance to a suitable landfill could itself increase environmental impacts, particularly for very small ion-exchange systems where transportation represents a larger share of the total impact.
The researchers acknowledged that this is one of the study’s limitations.
Other disposal methods could produce different costs and environmental consequences, and the researchers said more study is needed.
The Study Has Limits.
The authors identified several other limitations that are important when interpreting the results.
Some of the treatment models rely heavily on groundwater studies. Surface water can be more variable, meaning actual treatment costs and environmental impacts could be higher than the model estimates in some places.
The study also did not cover every type of PFAS. It concentrated on chemicals that could be modeled using existing U.S. Environmental Protection Agency treatment models.
Some shorter and ultra-short-chain PFAS may be more difficult to capture than the chemicals examined in the study.
The analysis also focused on single-use activated carbon and ion exchange resin. It did not fully evaluate whether regenerating or reactivating those materials could change the long-term economics or environmental impacts.
No Single Treatment Fits Every Community.
The study does not identify one PFAS treatment method as the best choice everywhere.
Instead, the results show how many pieces have to fit together.
A utility’s size matters. The source of its water matters. The amount of organic material in that water matters. The particular forever chemicals present matter. Even the lifespan of filters and the distance that used treatment material must travel for disposal can affect the outcome.
For smaller systems, those factors can become particularly important because there are fewer gallons of water and fewer customers across which to spread the expense.
As communities prepare for PFAS treatment requirements, the researchers said those differences should be considered when treatment systems and financial assistance are planned.
Citation:
Tushar, Md. Moshiur Rahman, Zaki Alam Pushan, Christopher Sutton Page, Nirupam Aich, and Lewis Stetson Rowles. “Nationwide sustainability assessment of PFAS treatment in U.S. water utilities.” Nature Communications, Article in Press. Received April 13, 2026; accepted August 26, 2026. DOI: 10.1038/s41467-026-77509-w.
