Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals found in products like non-stick cookware, firefighting foam, and water-resistant clothing. Their widespread use has led to contamination of drinking water sources worldwide. PFAS are highly persistent in the environment and linked to adverse health effects, including cancer, thyroid disease, and immune system issues. In 2024, the United States Environmental Protection Agency (USEPA) set maximum contaminant limits (MCL) for drinking water for PFAS compounds. Public water systems rely on various removal technologies to mitigate PFAS contamination and meet the MCL’s. Common PFAS removal technologies include: Granular Activated Carbon (GAC), Ion Exchange (IX), Reverse Osmosis (RO), and High-Pressure Membrane Systems.
Granular Activated Carbon (GAC) Filtration
Granular activated carbon is a porous material with a large surface area, making it effective for adsorbing contaminants. PFAS, being hydrophobic, tend to cling to the carbon’s surface. A multitude of public water systems now utilize GAC in their water treatment due to its ability to remove longer-chain PFAS compounds.
Case Study: The New Jersey American Water utility implemented GAC filtration to treat PFAS-contaminated groundwater in their water system. In this case, GAC removed up to 99% of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) .
Advantages
- Effectively removes long-chain PFAS compounds
- Provides a cost-effective option for large-scale public water systems
- Supports regeneration and reuse through thermal reactivation
Disadvantages:
- Shows reduced efficiency for short-chain PFAS
- Spent carbon requires disposal or regeneration
- Frequent monitoring becomes necessary to prevent breakthrough
Ion Exchange (IX)
Ion exchange technology uses resins that exchange charged ions in water with ions attached to the resin. PFAS, which carry a negative charge, can exchange with other ions, such as chloride or hydroxide. This method is particularly effective for short-chain PFAS compounds, which are harder to remove by GAC.
Case Study: An U.S. Environmental Protection Agency (EPA) study in North Carolina showed that IX could effectively remove both short- and long-chain PFAS compounds with a resin specifically designed for this purpose.
Advantages:
- Removes both long- and short-chain PFAS
- Offers high capacity for PFAS removal
- Treats water faster than GAC
Disadvantages
- High costs of ion exchange resins
- Requires resin regeneration or replacement after exhaustion
- Requires pre-treatment to remove competing ions, such as sulfate
Reverse Osmosis (RO)
Case Study: Cape Fear Public Utility Authority in North Carolina adopted a RO system to treat water contaminated with a short-chain PFAS. The RO system reduced PFAS levels by more than 99%.
Advantages:
- Effectively removes PFAS of all chain lengths
- Removes other contaminants, such as salts and heavy metals
- Provides high-quality, clean water
Disadvantages
- Involves high operational costs due to energy requirements
- Generates a concentrated waste stream that needs further treatment
- Membrane fouling can reduce system efficiency over time
High-Pressure Membrane Systems
High-pressure membrane systems, including nanofiltration, function similarly to RO but use membranes with larger pores. Nanofiltration also operates at lower pressures than RO, which reduces energy consumption but still offers PFAS removal efficiency. High-pressure membrane systems are particularly effective at removing large chain PFAS.
Case Study: A pilot project in Orange County, California, demonstrated that nanofiltration could reduce PFAS levels in treated wastewater by 90-99%. This study shows the technology’s potential for water reuse applications.
Advantages:
- Consumes less energy than RO
- Can work in synergy with other treatment technologies to improve performance and reduce costs
- Reduces PFAS concentrations to near-zero levels
Disadvantages:
- Less effective for short-chain PFAS compared to RO
- Requires pre-treatment to prevent membrane fouling
- Involves higher maintenance and operational costs
Conclusion
Common PFAS removal technologies like GAC, IX, RO, and high-pressure membrane systems offer reliable solutions for public water systems. Each technology has its strengths and weaknesses, and often, a combination of these methods achieves the best results. As PFAS regulations continue to evolve, public water systems must balance cost, efficiency, and sustainability in their PFAS treatment choices. Researchers are studying new technologies with the hope to provide effective treatment at lower costs with no waste streams.