Four white tiles each contain one blue letter to spell PFAS. The tiles are laid on top of soil.

What Water Suppliers Need to Know About PFAS Management

What Water Suppliers Need to Know About PFAS Management


July 10, 2023
Lori Kappen, PE; Sophia Liskovich, PE; Jamie Shambaugh, PE
Four white tiles each contain one blue letter to spell PFAS. The tiles are laid on top of soil.

Known as “forever chemicals,” per- and polyfluoroalkyl substances (PFAS) are highly resistant to degradation over time and can persist for thousands of years. Even at low concentrations, PFAS are known to have adverse impacts on human health and the environment.

In March 2023, the U.S. Environmental Protection Agency (EPA) proposed drinking water maximum contaminant levels (MCL) for six PFAS, and limits on using and discharging PFAS are in development. To best prepare for this pending federal legislation, water suppliers should understand:

  • The EPA’s proposed drinking water MCL.
  • Treatment alternatives and considerations for PFAS.
  • The benefits of hydrogeologic modeling of contamination plumes.
  • State and federal funding opportunities.

What Are PFAS?

PFAS are a class of synthetic chemicals used in manufacturing consumer products, such as water- and chemical-resistant coatings for raincoats, umbrellas, and nonstick surfaces. PFAS also are active ingredients in firefighting foam.

Over the years, and as a byproduct of these manufacturing and firefighting applications, PFAS were discharged into the environment. Previously undetected due to the absence of sampling requirements, today, PFAS are ubiquitous in the environment and are found in our air, soil, and water supplies.

Scientists discovered that some of the health risks associated with PFAS – even at low concentrations – include:

  • Increased cancer risk.
  • Changes in liver enzymes.
  • Thyroid issues.
  • Increased chance of high blood pressure.
  • Pre-eclampsia associated with pregnancy.
  • Decreased birth weight.

Understanding EPA's Proposed Drinking Water MCL Regulations

The EPA’s proposed National Primary Drinking Water Regulation (NPDWR) will limit the levels of six PFAS compounds in drinking water to reduce health implications caused by PFAS contamination. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) will be limited to four parts per trillion, a level close to the detection limit.

CompoundProposed MCL
PFOA4.0 ppt
PFOS4.0 ppt
PFNA1.0 (Hazard Index)
PFHxS1.0 (Hazard Index)
PFBS1.0 (Hazard Index)
HFPO-DA (GenX Chemicals)1.0 (Hazard Index)

The proposed limits on PFAS compounds under the National Primary Drinking Water Regulation.

Four compounds will be regulated by a combined hazard index:

  • Perfluorononanoic acid (PFNA).
  • Hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt, also known as “GenX chemicals.”
  • Perfluorohexane sulfonic acid (PFHxS).
  • Perfluorobutane sulfonic acid (PFBS).

The hazard index sums the ratio of each compound’s concentration relative to its target maximum concentration to calculate a net ratio for the four compounds.

Hazard index equation to determine PFAS net risk.

Hazard index equation to determine PFAS net risk.

The NPDWR requires PFAS treatment for water utility companies. Under the regulation, public water suppliers must:

  • Monitor their systems for these PFAS.
  • Notify the public of the levels of PFAS present in their systems.
  • Reduce the levels of the six PFAS in the drinking water if they exceed the maximum contaminant level goals.

While your state may already have PFAS standards, the new federal drinking water requirement may be more stringent, requiring treatment even if the current state standards do not.

States with PFAS drinking water requirements as of February 2023.

The EPA also is investigating ways to reduce PFAS, such as:

  • Cleaning up contaminated groundwater and the surrounding environment.
  • Regulating new discharges from industrial sources.
  • Researching the effects of publicly owned treatment works and wastewater treatment plants to see how contamination dissipates during treatment, how much gets discharged, and what happens if it ends up in biosolids.

Under the Safe Drinking Water Act (SDWA), the EPA issued a list of unregulated contaminants to be monitored by public water systems (PWS). A PWS is a water system that provides potable water to the public and serves at least 15 service connections or 25 people for at least 60 days of the year.

The fifth Unregulated Contaminant Monitoring Rule (UCMR 5) of the SDWA will provide new data that is critically needed to improve the EPA’s understanding of the frequency and levels of 29 PFAS found in the nation’s drinking water systems.

PFAS Treatment Alternatives and Considerations

Adsorption onto a solid media – typically granular activated carbon (GAC) or an ion exchange resin – is the most conventional way to treat PFAS in drinking water. Alternative adsorbents are also available, with additional materials in various stages of testing for PFAS treatment potential. Membrane filtration technologies, including reverse osmosis and nanofiltration, effectively remove PFAS from drinking water but are more costly to build and operate than the adsorption technologies. They also require more pretreatment and create a concentrated waste stream that is difficult to dispose of.

Granular Activated Carbon and an Ion Exchange Resin

GAC and ion exchange resins adsorb PFAS with more than 99% removal efficiency. Typical adsorption uses trains of two tanks operated in a lead-lag configuration, in which the water flows through the two tanks in series.

When the first tank is exhausted, the valve positions are switched, and the lag tank assumes the lead position. The result is relatively clean media in the lead tank to adsorb the higher concentrations and new media in the lag tank to remove lower concentrations that may remain after treatment in the lead tank.

Following are some considerations for GAC and ion exchange resins:

  • GAC can be used in a gravity filter-adsorber mode and may be a good treatment option for low PFAS concentrations. However, interactions between the GAC and particulate matter accumulating on the filter media might make it less effective for PFAS absorption. In addition, available empty bed contact times in a gravity filter may be less than in a designed lead-lag PFAS removal system. Pilot testing is recommended before selecting or designing a filter-adsorber for PFAS removal to confirm treatment effectiveness and design parameters.
  • Adding powdered activated carbon (PAC) to the process flow also can absorb PFAS to some extent. However, the effectiveness will highly depend on the water quality, PAC dose, and available contact time. Since PAC’s effectiveness increases with contact time, adding it upstream from the sedimentation and filtration aids in PFAS removal.
  • Pilot testing is beneficial in comparing how background contaminants, ions, and organic contaminants determine GAC or resin effectiveness. Pilot testing usually requires six to 12 months to collect data on the bed life until PFAS contaminants break through. However, the results allow better decisions about which resin or GAC will perform best for the water source.

Comparison of GAC and Ion Exchange

GAC needs a long empty bed contact time to remove the PFAS effectively, so the typical design results in 15 to 25 minutes of total empty bed contact time. In contrast, an ion exchange typically needs 3 to 5 minutes. The GAC generally operates at a lower surface loading rate than ion exchange resin, so it will normally require larger diameter tanks or more treatment trains than an ion exchange resin-based treatment system.

Organic chemicals like volatile organic compounds, synthetic organic chemicals, and total organic carbon can interfere with the adsorption of PFAS on GAC by competing for adsorption sites, leading to a reduced operating time before GAC replacement is required. By comparison, ion exchange resins are more affected by the presence of ions in the water. Nitrate, sulfate, chloride, and other ions have a significant impact that can reduce the life of the ion resin before requiring replacement.

GAC requires more substantial backwashing before the initial startup to remove fines. An ion resin requires a shorter backwash to remove fines. We recommend backwashing the resin so the saturated and unsaturated resins don’t mix, which can lead to a premature breakthrough of the PFAS.


Costs per cubic foot for GAC are significantly less than for ion resin; however, because the resin requires less empty bed contact time than GAC, it requires less volume to be installed for the same treatment capacity.

Therefore, one of the key considerations in comparing costs for a GAC treatment system versus an ion resin exchange system is understanding how frequently the media will need to be replaced and how that impacts the treatment system’s operating costs. GAC or ion exchange resin is more cost-effective depending on the water quality to be treated.

Water flowing from green moss-covered rocks into a stream.

Benefits of Hydrogeologic Modeling of Contamination Plumes

PFAS are highly mobile in groundwater because they are hydrophobic, lipophobic, and have surfactant properties that help them infiltrate the ground quickly.

Groundwater model development allows us to run several pumping scenarios to study a plume’s migration and its impacts on various wells. When multiple wells have elevated PFAS concentrations, the initial reaction may be to shut down the contaminated wells and use wells where PFAS haven’t been detected, and that’s a suitable initial procedure. However, changes in groundwater use can impact the plume’s movement. Hydrogeologic modeling can assist in long-term planning to optimize well use and identify likely future changes in PFAS concentrations at wells. For example:

  • If you’re no longer pumping water from contaminated wells, how might that impact other wells in the area? Groundwater modeling evaluates those scenarios.
  • In the early days of PFAS discovery, wells were pumped to waste to keep contamination plumes from spreading. However, modeling can be used to consider how untreated waste potentially contributes to the plume’s migration.
  • Strategies to optimize pumping of the wells or apply treatment to contain the plume and protect other wells in the system or surrounding areas can be evaluated with modeling.

Design Considerations

When considering a PFAS removal system, some items to keep in mind are:

  • Pressure losses.
  • Waste generation and disposal.
  • Site constraints and access.
  • Permitting and costs.

The components of typical PFAS removal systems include:

  • Feed pumps to overcome new pressure loss (20-30 pounds per square inch).
  • Pretreatment (bag/cartridge filter) with redundancy.
  • Vessels.
  • Sample ports.
  • Instrumentation.
  • Chemical feed points (possibly relocated).

Waste Generation and Disposal

GAC and ion exchange resin disposal options include incineration or landfilling. However, the long-term viability of landfilling may change as research and regulations advance. Current research indicates that incinerating the media under controlled conditions and high temperatures destroys PFAS, which can help permanently remove PFAS from the environment.

GAC also has the option of being regenerated and reused. The regeneration process uses heat at a controlled high temperature to reactivate the carbon. Current research indicates that PFAS are destroyed during the regeneration process.

It is technologically possible to regenerate resin using steam to remove the PFAS. However, this method does not destroy the PFAS; the remaining concentrated PFAS solution will need a disposal solution, so this may not be practical for many water providers.

A design consideration is waste discharge. GAC and most of the available PFAS treatment resins will require flushing when first installed to remove fine particles that may be present in the media and to stratify the bed.

During the initial flushing procedures, when GAC is installed, GAC can release arsenic, which is naturally present in the carbon. Arsenic will be discharged with the waste and may go to the sewer or a waste holding tank, so waste disposal should be coordinated with the receiving entity. Pre-rinsed GAC is available, which can reduce initial flushing requirements and waste volumes.

Another issue is tolerance to chlorine. GAC can handle low chlorine levels, but ion exchange cannot. Keep this in mind with the current water source used for backwash.

Site Constraints and Access

Treatment vessels vary in output from a few gallons per minute to millions of gallons per day and vary in diameter from 30 inches to 14 feet. Site constraints must be considered when deciding how to deliver and house the vessels. Double, overhead, or removable doors make vessel replacement easier.

Two water treatment vessels are connected by valves. The labels in the picture show the vessels’ height, width, and length, as well as components.

Consider site constraints and access when choosing a vessel building.

State and Federal Funding Opportunities

State and federal funding will ease the burden of capital costs associated with PFAS removal. There are three pockets of money designated for dealing with emerging contaminants:

Drinking Water State Revolving Fund

The Drinking Water State Revolving Fund (DWSRF) is a financial assistance program to help water systems and states achieve the SDWA’s objectives. Congress appropriates funding for the DWSRF, and then the EPA awards capitalization grants to states based on their most recent drinking water infrastructure needs survey and assessment results.

Clean Water State Revolving Fund

The Clean Water State Revolving Fund (CWSRF) is a federal-state partnership that provides low-cost financing to communities for water quality infrastructure projects. The Bipartisan Infrastructure Law (BIL) appropriated $1 billion through 2026 to the CWSRF specifically to address PFAS.

Emerging Contaminants in Small or Disadvantaged Communities Grant

The Emerging Contaminants in Small or Disadvantaged Communities Grant awards grants non-competitively to small or disadvantaged communities to address emerging contaminants, including PFAS. In February 2023, the EPA announced the BIL’s availability of $2 billion to promote access to safe and clean water in small, rural, and disadvantaged communities. Eligible projects include:

  • Activities to address emerging contaminants in communities.
  • Technical assistance to evaluate problems.
  • Programs to provide household water quality testing.
  • Training for local contractors.
  • Installation of centralized water treatment.

Gannett Fleming’s water engineers are ready to assist you with your PFAS-related challenges, from environmental investigations, planning, and permitting to treatment design, construction management, and funding. Contact one of us to see how we can help you achieve regulatory compliance and ensure the future health of your community.

Gannett Fleming is Ready to Assist with PFAS-Related Challenges

Our water engineers are ready to assist you with your PFAS-related challenges, from environmental investigations, planning, and permitting to treatment design, construction management, and funding. Contact one of us to see how we can help you achieve regulatory compliance and ensure the future health of your community.


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