What Water Suppliers Need to Know About PFAS Management

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.

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.

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.

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.

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.

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.

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.

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.

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:

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.

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.

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.

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.