A Guide To PFAS Treatment In Drinking Water

PFAS (per- and polyfluoroalkyl substances) are a large family of over 10,000 synthetic chemicals invented in the 1940s and used across many industries due to their ability to repel water, oil, stains, grease, and heat. These chemicals do not break down naturally in the environment and bioaccumulate in the human body and wildlife while contaminating water, soil, and air. Exposure to certain PFAS has been linked to severe adverse health effects.

Governments and regulatory bodies are increasingly restricting and phasing out PFAS, particularly the most studied and detrimental compounds like PFOA and PFOS. However, the large number of PFAS compounds makes regulation challenging. Efforts are underway to develop PFAS-free alternatives and clean up PFAS contamination, but the extreme persistence of these "forever chemicals" makes them difficult to remove from the environment once released.

Due to their everyday use in consumer products and industrial applications, PFAS substances have infected water supplies worldwide. Exposure to certain PFAS like PFOA and PFOS is associated with a variety of diseases and conditions, including cancer, reproductive issues, thyroid dysfunction, and impaired immune response. Because they bioaccumulate easily, they have become a global health issue.

Until recently, there have been no enforceable federal standards for PFAS in drinking water in the U.S., leading many states to enact their own limits, creating a patchwork of regulations. Therefore, the U.S. EPA has released new guidelines to create the first enforceable national standards for PFAS removal and destruction. Although necessary, these new regulations have severe consequences for the water industry as upgrading water treatment systems to remove and destroy PFAS can be highly costly to local water utilities and their ratepayers.

Due to PFAS’ impact on the water industry, we’ve created this comprehensive guide to explain the different types of PFAS, their prevalence in drinking water, recent regulations and guidelines, and best practices for detecting, removing, and destroying them.

Table Of Contents:

1. Understanding PFAS
2. PFAS Regulations And Guidelines
3. Cost Of PFAS Treatment
4. PFAS Detection And Monitoring
5. PFAS Treatment Technologies
6. PFAS Treatment System Design
7. Operation And Maintenance Of PFAS Removal Systems
8. PFAS Destruction Technologies
9. Engaging With The Community About PFAS
10. Future Outlook For PFAS Removal And Discharge
11. Final Thoughts

Understanding PFAS

Definition And Types Of PFAS

Although the term PFAS encompasses thousands of chemicals, their common denominator is that they each possess at least one fully fluorinated carbon atom. They generally include compounds with a perfluoroalkyl moiety (C-F2-C-) or a perfluoroalkyl ether moiety (C-F2-O-C-F2-). However, regulatory definitions often need to be more precise, such as requiring a minimum number of fully fluorinated carbons (e.g., three or more).

Types of PFAS include:

• Perfluoroalkyl substances (PFAAs): Fully fluorinated alkyl substances, such as PFOA and PFOS. These are considered the most concerning PFAS

• Polyfluoroalkyl substances (PFAS precursors): Partially fluorinated alkyl substances that can transform into PFAAs in the environment

• Fluoropolymers: Polymers with a carbon-only backbone and fluorine atoms directly attached, such as PTFE and PVDF

• Side-chain fluorinated polymers: Polymers with a non-fluorinated carbon backbone and polyfluoroalkyl side chains

• Perfluoropolyethers (PFPEs): Fluorinated polymers with carbon-oxygen backbones

PFAS Contamination In Drinking Water

Given the prevalence of PFAS in the commercial and industrial sectors, it’s not surprising that drinking water contamination is widespread in the U.S. and abroad.

PFAS are released into the environment through various industrial and consumer products, including firefighting foams, non-stick cookware, stain-resistant textiles, and food packaging. These chemicals can contaminate surface water and groundwater sources used for drinking water, especially near sites of PFAS manufacturing or use. Until recently, inadequate monitoring and management of PFAS in the environment led to ongoing source pollution and incomplete removal of these "forever chemicals".

PFAS can be found in water sources across the U.S., and a U.S. Geological Survey (USGS) study estimated that over 45% of U.S. tap water contains one or more types of PFAS.

Health And Environmental Concerns Associated With PFAS

PFAS are proven to harm human health and the environment, which are worsened by their prevalence and bioaccumulation. Health concerns include:

• Reproductive effects: decreased fertility and increased risk of high blood pressure in pregnant women

• Developmental effects: low birth weight, accelerated puberty, behavioral changes in children

• Increased cancer risk: prostate, kidney, and testicular cancers

• Immune system impacts: reduced ability to fight infections, decreased vaccine response

• Hormonal disruption: interference with the body's natural hormones

• Metabolic diseases: increased cholesterol and obesity risk

• Liver disorders: enzyme changes and non-alcoholic liver disease

• Thyroid effects: dysfunction and increased thyroid disease

In the environment, PFAS do not easily break down, contaminating water, soil, and air, leading to widespread environmental exposure . Due to this widespread contamination, PFAS can bioaccumulate in the food chain, which affects our food and water sources.

PFAS have been detected in drinking water, surface water, groundwater, and even remote environments like the Arctic. Cleanup and remediation of PFAS contamination is highly challenging due to their persistence.

PFAS Regulations And Guidelines

EPA’s New PFAS Drinking Water Regulations: Background

Regulations and guidelines regarding PFAS changed dramatically in 2023 and 2024. On April 10, 2024, the Biden-Harris administration issued groundbreaking legislation to protect Americans from PFAS. This rule is the culmination of the EPA's PFAS Roadmap strategy launched in 2021 as a three-year plan to combat PFAS contamination. Critical steps in the formation of this rule included:

• April 2023: the EPA issued an Advance Notice of Proposed Rulemaking to gather public input on potential future PFAS regulations under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund.

• June 2023: the EPA released a framework for addressing new uses of PFAS under TSCA to ensure they pose no harm before entering commerce.

• August 2023: the EPA finalized its National Enforcement and Compliance Initiatives for 2024-2027, including "Addressing Exposure to PFAS" to implement the EPA's PFAS Strategic Roadmap.

• October 2023: the EPA published a final rule under the Toxic Substances Control Act (TSCA) that requires all manufacturers (including importers) to report PFAS production volumes, disposal, exposures, and hazards. This provides the EPA, its partners, and the public with the largest-ever dataset on PFAS manufactured and used in the U.S.

• January 2024: the EPA finalized a rule establishing the first-ever nationwide, legally enforceable drinking water standards to protect communities from PFAS in their drinking water. This rule sets Maximum Contaminant Levels (MCLs) for PFOA and PFOS, the two most well-studied PFAS compounds. The EPA is also conducting the most comprehensive monitoring effort for 29 PFAS in public water systems through the Unregulated Contaminant Monitoring Rule 5 (UCMR 5).

Key Standards In The 2024 PFAS Rule

The Biden-Harris administration's goal is to protect 100 million Americans from PFAS. Therefore, the guidelines outlined in the new 2024 rule are designed to be strict and far-reaching to combat this growing health crisis aggressively:

1. Maximum Contaminant Levels (MCLs): for PFOA and PFOS, the enforceable MCL is set at 4.0 parts per trillion (ppt) individually. For PFNA, PFHxS, and GenX chemicals, the MCL is set at 10 ppt.

2. Health-Based Goals: the non-enforceable, health-based goal for PFOA and PFOS is set at zero.

3. Mixture Standard: there is also a limit set for any combination of four PFAS: PFNA, PFHxS, PFBS, and GenX chemicals.

4. Compliance Timeline: public water systems have three years to complete initial monitoring for these PFAS. Where PFAS levels exceed the standards, systems must implement solutions to reduce PFAS within five years.

5. Public Notification: water utilities must inform the public of the PFAS levels measured in their drinking water.

Kyle Thompson, National PFAS Lead at Carollo Engineers, discusses the impact of the EPA’s April 2024 PFAS rule with Travis Kennedy and Kevin Westerling on the Water Online Show.

CERCLA (Superfund) Designation Implications

The CERCLA hazardous substance designation for PFOA and PFOS under the Superfund law represents an important step in the regulatory framework and has far-reaching implications for the entire water industry as well as other sectors responsible for PFAS cleanup. This designation results in the following:

• Expanded Cleanup Obligations: Designating PFOA and PFOS as hazardous substances under CERCLA requires parties responsible for PFAS contamination to conduct cleanup and remediation efforts. This will significantly expand the number of sites where PFAS cleanup is required, as CERCLA provides a framework for identifying, investigating, and remediating contaminated sites.

• Increased Reporting And Disclosure Requirements: The CERCLA hazardous substance designation triggers new reporting requirements for releases of PFOA and PFOS into the environment, leading to more comprehensive data on PFAS contamination sources and locations, informing future regulatory actions.

• Potential Liability Concerns: Designating PFOA and PFOS as CERCLA hazardous substances exposes a broader range of parties to potential liability for PFAS contamination, including manufacturers, users, and waste handlers. Hopefully, this will incentivize companies to reduce PFAS use and properly manage PFAS-containing waste to avoid cleanup costs and legal liabilities.

The CERCLA designation alone may not be sufficient to fully address the broader class of PFAS compounds, as it is limited to just two specific substances. Ongoing challenges remain in terms of identifying all PFAS sources, establishing appropriate cleanup standards, and securing adequate funding for remediation efforts.

Cost Of PFAS Treatment

Complying with these new rules comes with a multi-billion-dollar price tag. However, the new guidance allows utility providers to hold polluters accountable for the high costs of compliance, and numerous lawsuits have already been filed in several states around the country in response to the new guidelines. Compliance costs cover three major areas:

• Drinking Water Utility Costs: According to a report by the American Water Works Association (AWWA) and Black & Veatch, drinking water utilities must invest over $50 billion over the next 20 years to install and operate treatment technology to comply with new PFAS standards. This includes the costs of designing, constructing, and operating treatment systems to remove PFAS from drinking water supplies.

• Wastewater Utility Costs: A survey by the National Association of Clean Water Agencies (NACWA) suggests that operational costs for individual clean water utilities will increase by up to 60% due to new PFAS regulations. For example, a study from Minnesota estimated the total wastewater costs for that state to remove PFAS to be between $14 and $28 billion over 20 years. Extrapolating this nationally, wastewater utilities are facing billions of dollars per annum in additional costs.

• Disposal And Compliance Costs: A hazardous substance designation for PFOA and PFOS under CERCLA could add another $3.5 billion per year in disposal costs for the water sector. Legal and regulatory compliance, e.g., obtaining permits and meeting reporting obligations, may also add significantly to the overall PFAS cleanup costs.

PFAS Detection And Monitoring

Before cleanup can begin, water utilities must test for PFAS contamination and have strategies in place for continuous monitoring. The EPA has approved several methods for testing and monitoring water quality.

EPA-Approved Drinking Water Methods

The EPA has approved two primary methods for testing drinking water:

• EPA Method 533: Determination of PFAS in Drinking Water by Isotope Dilution Anion Exchange SPE and LC/MS/MS

• EPA Method 537.1: Determination of Selected PFAS in Drinking Water by SPE and LC/MS/MS

These methods are designed and validated for analyzing 29 PFAS compounds in drinking water samples and are the recommended techniques for utilities to comply with new PFAS regulations.

Non-Potable Water And Environmental Media Methods

Methodologies for testing non-potable water and environmental media are still in development under EPA Draft Method 1633: Detection of PFAS in non-potable water, soil, sediment, and other ecological matrices using SPE and LC-MS/MS. This draft method is intended to expand PFAS analysis capabilities beyond just drinking water samples.

Emerging Techniques

Scientists are working to develop more efficient methods for detecting PFAS contamination, including:

• Fluorescent chemosensors: novel optical sensors that can detect and quantify PFAS in aqueous samples

• 3D-printed cone spray ionization (3D-PCSI) with mass spectrometry: an innovative technique for rapid, on-site PFAS detection

• Optical fiber sensor networks: used to detect PFOA in water samples

These emerging techniques may provide faster, more portable, and potentially lower-cost alternatives to the standard LC-MS/MS methods, though they have not yet been as extensively validated or approved for regulatory compliance.

PFAS Treatment Technologies

Water utilities have a variety of options for removing PFAS from drinking water to meet new compliance requirements.

Activated Carbon

Activated carbon filtration, in both granular (GAC) and powdered (PAC) forms, is the most studied and widely used treatment technology for removing PFAS from drinking water. GAC can be up to 100% effective at eliminating longer-chain PFAS like PFOA and PFOS, depending on factors like the type of carbon, flow rate, and presence of other contaminants. Shorter-chain PFAS like PFBS and PFBA do not adsorb as well onto activated carbon, resulting in earlier "breakthrough" and the need for more frequent carbon replacement or regeneration.

Mechanism Of PFAS Adsorption

Activated carbon, in both GAC and PAC forms, adsorbs PFAS compounds through the process of adsorption at the interface between the liquid (water) and solid (carbon) phases, acting as an effective adsorbent due to its highly porous structure, which provides a large surface area for contaminants like PFAS to adsorb onto.

• Influence Of PFAS Chain Length: Longer-chain PFAS like PFOA and PFOS are better adsorbed by activated carbon than shorter-chain PFAS like PFBA and PFPeA. This is due to the decreasing polarity of PFAS compounds as the carbon chain length increases, leading to stronger adsorption interactions with the carbon surface.

• Adsorption Capacity: The adsorption capacity of activated carbon for PFAS increases with chain length, as evidenced by higher Freundlich adsorption coefficients (KF) and lower Freundlich exponents (n). This means longer-chain PFAS can be adsorbed to a greater extent before the carbon becomes saturated.

• Breakthrough Behavior: Shorter-chain PFAS, like PFBA, exhibits earlier breakthroughs in GAC filters, meaning the carbon becomes saturated more quickly and requires more frequent replacement or regeneration. In contrast, longer-chain PFAS like PFOA can be effectively removed by GAC for a longer period before a breakthrough occurs.

GAC Filtration Process

GAC is typically used in a flow-through filter mode, where the water passes through a bed of granular activated carbon. The PFAS compounds adsorb onto the large surface area of the porous carbon material as the water flows through. Pretreatment to remove particulates and other contaminants is often required before the GAC filtration step to prevent fouling and maintain performance.

PAC Application

PAC can be added directly to the water and removed through filtration or clarification. However, it is less efficient and economical than GAC for PFAS removal, as it has a lower adsorption capacity and requires higher doses to achieve modest removal rates.

Additional Factors Influencing Activated Carbon Efficiency

Although activated carbon is a popular method for removing PFAS, utilities must consider specific operational factors when designing an activated carbon system.

• GAC replacement or regeneration frequency is a critical operational factor, as the carbon's PFAS removal efficiency decreases over time. When designing GAC systems, utilities must also plan for soaking and backwash requirements, pH adjustment, arsenic content, and disinfectant. Disposal or incineration of the spent, PFAS-laden carbon is another crucial environmental consideration.

• The type of activated carbon, including its surface charge, pore-size distribution, and surface area, can impact its PFAS adsorption capacity and efficiency. Positively charged activated carbons generally show higher adsorption capacities for PFAS compared to neutral or negatively charged carbons.

• The competition from other organic compounds, such as total organic carbon (TOC), can reduce the available adsorption sites on the activated carbon and decrease its PFAS removal efficiency. Pretreatment to remove particulates and other contaminants is often required before the GAC filtration step to prevent fouling and maintain performance.

• Operating conditions such as flow rate, bed depth, and contact time can affect the PFAS removal rates, with lower flow rates and deeper beds generally improving performance.

• The disposal or incineration of the spent, PFAS-laden activated carbon is an important environmental consideration, as the PFAS compounds are not destroyed during the process.

• Regeneration of the activated carbon can help extend its useful life, but the regenerated carbon may not be as effective as virgin carbon for PFAS removal.

Ion Exchange

Ion exchange (IX) is an effective technology for the remediation of PFAS-contaminated water, including surface water, groundwater, and wastewater. PFAS compounds, which are anionic, zwitterionic, and neutral, can be removed through adsorption and ion exchange mechanisms on specialized IX resins. The adsorption capacity of IX resins for PFAS can be up to 5 millimole per gram (mmol/g), with factors like resin porosity, PFAS chain length, and competing ions influencing the adsorption process. This removal process entails diffusion, electrostatic interactions, and hydrophobic effects between the PFAS and the resin surface.

Application In Drinking Water Treatment

IX resins can be more effective than activated carbon at removing emerging short-chain PFAS that are not well adsorbed by carbon-based processes. IX can achieve PFOA and PFOS removal rates of 77-99%, with the highest rates for sulfonates and longer-chain PFAS. These systems can also be designed and optimized for specific PFAS compounds, allowing for higher capacity and more targeted removal compared to general adsorption processes.

Challenges And Considerations

Despite these advantages, other competing ions and organic matter in the water can impact the IX resin's PFAS removal efficiency and require pretreatment. Regeneration of the spent IX resin is another important consideration, as its eluent composition and reuse can affect its long-term performance. Disposal or incineration of the PFAS-laden IX waste stream is a further environmental concern that must be addressed. Finally, capital and operating costs of IX systems can be similar to or higher than activated carbon, depending on the specific resin and treatment requirements.

Membrane Filtration

Membrane filtration, including nanofiltration (NF) and reverse osmosis (RO), is an effective technology for removing PFAS from water. The membrane acts as a physical barrier, allowing water to pass while retaining PFAS and other contaminants. Membrane filtration can achieve PFOA and PFOS removal rates over 99% and removal rates of 84-99% for other PFAS compounds. However, this type of filtration can be impacted by fouling, scaling, and high operating costs compared to other treatment methods like activated carbon and ion exchange.

Specific Membranes For PFAS Removal

Novel membrane materials have been developed to improve PFAS removal, such as fluorinated silane-functionalized aluminum oxide hydroxide membranes. Polymeric membranes modified with adsorbents like nanoparticles or graphene oxide can also enhance PFAS rejection. Ceramic membranes and nanoparticle-coated silica membranes have shown high PFAS removal efficiency, though they may experience irreversible changes to the membrane surface over time. Reactive electrochemical membranes and phosphorene nanocomposite membranes can not only remove PFAS but also degrade them through advanced oxidation processes.

Performance And Limitations

Membrane filtration is generally more effective at removing longer-chain PFAS like PFOA and PFOS compared to shorter-chain PFAS, but the presence of other contaminants like organic matter and dissolved solids can impact membrane performance and lead to fouling. Membrane systems require high operating pressures, which increases energy consumption and costs, and the waste-concentrated stream also needs to be managed appropriately. While membrane filtration is a promising technology, ongoing research is focused on improving materials, reducing fouling, and lowering operating costs to make it more widely deployable for PFAS removal.

Advanced Oxidation Processes (AOPs)

AOPs offer another effective method for eradicating PFAS from drinking water. These highly reactive oxidizing species, such as hydroxyl radicals, degrade and transform PFAS compounds in water. Standard AOP technologies include UV, UV/H2O2, ozone, ozone/H2O2 (peroxone), and photocatalysis using materials like TiO2 and boron nitride. The goal of AOPs is to break down the solid carbon-fluorine bonds in PFAS, leading to defluorination and the formation of shorter-chain or more easily removable compounds.

Comparative Analysis Of AOPs

Studies show that different AOP technologies have varying effectiveness for PFAS removal, with some being more suitable for certain PFAS compounds than others. For example, ozone and UV/H2O2 can achieve high removal rates (up to 100%) for longer-chain PFAS like PFOA and PFOS while less effective for shorter-chain PFAS. Photocatalytic processes using materials like TiO2 and boron nitride have also demonstrated promising PFAS degradation capabilities. The optimal AOP approach often depends on factors like PFAS composition, water matrix, operating conditions, and cost-effectiveness.

Real-World Applications And Outcomes

While AOPs have shown potential for PFAS removal in lab and pilot-scale studies, their real-world application is not straightforward. Unfortunately, AOPs can transform non-detected or unknown longer-chain PFAS into detectable shorter-chain PFAS, leading to an overall increase in the total PFAS concentration. This "transformation" of PFAS compounds makes it difficult to accurately assess the effectiveness of AOPs for PFAS removal, highlighting the need for more comprehensive analytical methods. To address this, some studies suggest using adsorbable organic fluorine (AOF) analysis before and after AOP treatment as a more holistic approach to evaluating PFAS removal.

PFAS Treatment System Design

Deciding Factors

Designing a treatment system is a multi-stage process that balances innovative science with pragmatic considerations. Whether water providers are looking for temporary or permanent solutions, the following factors should be weighed:

• PFAS Removal Capabilities: Naturally, the most critical aspect of any treatment technology is how effectively it removes the specific PFAS compounds in the water source. Technologies such as those described above have proven capabilities.

• Water Quality: The existing water quality, including other contaminants, organic matter, and water chemistry parameters, can impact the performance and effectiveness of PFAS removal technologies. These issues need to be carefully evaluated during the design process.

• Process Integration: The treatment system must integrate well with the utility's existing facilities, operations, and infrastructure. This includes evaluating available space, power requirements, waste disposal, and compatibility with other treatment processes.

• Operational Factors: The long-term operation and maintenance requirements of the PFAS treatment system, such as the need for resin regeneration, filter replacements, and waste disposal, must be accounted for in the design.

• Regulatory Compliance: The treatment system must meet any applicable regulatory requirements for PFAS levels in drinking water, as well as other water quality standards.

• Cost: Designers must also consider the capital and operating costs of the PFAS treatment system, including expenses for equipment, construction, energy, consumables, and waste disposal.

Large-Scale Water Treatment Plants

Large-scale treatment systems should consider all the above plus the following essential criteria:

• Treatment Objectives And Removal Targets: Clearly define the target PFAS compounds and the desired removal efficiencies to meet regulatory requirements or utility goals. Understand the specific PFAS properties (e.g., chain length, functional groups) and how they impact removal by different technologies.

• Treatment Technology Selection: Assess the effectiveness, reliability, and cost-effectiveness of varying PFAS removal technologies like activated carbon, ion exchange, and high-pressure membranes. Consider the integration of multiple treatment processes for enhanced PFAS removal. Conduct bench- and pilot-scale testing to validate the performance of selected technologies under site-specific conditions.

• Operational Factors: Determine the empty bed contact time (EBCT) requirements for activated carbon systems to achieve the desired PFAS removal. Evaluate the operational feasibility, maintenance needs, and waste management implications of the selected PFAS treatment technologies.

• Flexibility And Expandability: Incorporate design features that allow for future modifications or expansion to accommodate changes in water quality, regulations, or demand.

• Reliability And Redundancy: Ensure the treatment plant has sufficient reliability, backup systems, and redundancy to maintain consistent water supply and quality in the face of PFAS contamination.

Case Studies Showcasing Effective PFAS Treatment System Designs

Despite the challenges inherent in PFAS removal, success stories offer a roadmap to utilities looking to eradicate PFAS.

Horsham Water & Sewer Authority (HWSA) Case Study

The town of Horsham, outside of Philadelphia, experienced significant PFAS contamination due to its proximity to multiple polluters but now stands as a success story. In 2014, HWSA began to assess the problem and develop a solution. At first, HWSA planned to use granular activated carbon (GAC) adsorption for PFAS removal but later decided to pilot-test ion exchange (IX) resin as an alternative.

The pilot testing showed that the IX resin had significantly higher PFAS removal capacity than GAC, with 15-21 times higher bed volumes until the breakthrough for various PFAS compounds. As a result, HWSA decided to use IX resin for the final permanent PFAS treatment systems for their remaining wells despite the initial regulatory hurdles being more difficult for IX compared to GAC. Today, Horsham’s water stands as an example of successful PFAS removal.

Cape Fear Public Utility Authority (CFPUA) Case Study

CFPUA evaluated various treatment options, including GAC, IX, and high-pressure membranes, for PFAS removal at their Sweeney Water Treatment Plant. After considering economic and non-economic factors, CFPUA selected post-filter, deep-bed GAC contactors as the best overall PFAS treatment solution. The GAC facility was designed for a 20-minute empty bed contact time (EBCT) at the maximum 44-MGD treatment capacity, requiring about 3 million pounds of GAC. If needed, the GAC contactors were also designed for potential future conversion to IX resin. Their efforts succeeded in removing PFAS efficiently.

Operation And Maintenance Of PFAS Removal Systems

Operation and maintenance considerations must ensure proper system monitoring, implement rigorous maintenance protocols, and provide comprehensive training for water treatment personnel. Careful attention to these factors is essential for the long-term effectiveness of PFAS removal systems.

Operation And Monitoring

Water treatment units require regular monitoring and maintenance to ensure they continue working effectively over time. The different purification methods and materials require varying degrees of maintenance, but in every instance, improper operation or lack of maintenance can cause the systems to lose their PFAS removal effectiveness. Utilities need to closely monitor the PFAS levels in the treated water and make adjustments as needed.

Maintenance Protocols For Long-term Effectiveness

PFAS removal systems like activated carbon filters and reverse osmosis membranes must be serviced and replaced regularly to maintain their performance. This includes replacing filter media, membranes, and other components as they become saturated or fouled over time. Developing and following rigorous maintenance protocols is critical.

Personnel Education And Training

Proper operation and maintenance of PFAS removal systems requires specialized knowledge and skills. Water utilities need to provide thorough training for their treatment plant staff on the technology, monitoring procedures, maintenance requirements, and troubleshooting. Ongoing education is vital as regulations as best practices evolve.

PFAS Destruction Technologies

Thermal And Chemical PFAS Destruction Methods

Once PFAS are removed, they must be carefully and safely eradicated so they do not continue to harm people and the environment. A range of thermal and chemical technologies are being developed and deployed to destroy PFAS in water, each with its own advantages, disadvantages, and optimal applications.

Thermal Degradation/Incineration

Applying high heat (980°C to 1200°C) can destroy PFAS through thermal oxidation and mineralization, breaking the PFAS compounds into carbon dioxide, water, hydrogen fluoride, and other byproducts. However, this complex process requires high temperatures and long residence times to achieve satisfactory PFAS destruction. To expedite PFAS destruction, the EPA has created a database to help water utilities understand and implement thermal processes.

Chemical Destruction Technologies

New and emerging technologies offer alternatives to thermal degradation, including:

• Supercritical Water Oxidation (SCWO): high temperatures (374°C) and pressure oxidizes organic compounds like PFAS. The SCWO process can effectively destroy PFAS, though it struggles with high concentrations of salt and requires pretreatment.

• Hydrothermal Alkaline Treatment (HALT): similar to SCWO, this method uses high temperature and pressure along with a sodium hydroxide catalyst to destroy PFAS.

• Non-Thermal Plasma (NTP): an electrical discharge generates reactive species that can degrade PFAS. NTP has shown promising PFAS destruction capabilities, though water chemistry factors like pH and organic matter can impact it.

• Chemical Oxidation: advanced oxidation processes like ozonation, Fenton's reagent, and persulfate oxidation can chemically break down PFAS compounds. The effectiveness depends on the specific PFAS compounds and water quality.

• Electrochemical Oxidation (EO): oxidizes and degrades PFAS compounds through direct and indirect electrochemical reactions. EO has demonstrated >99% removal of long-chain PFAS, though short-chain PFAS are more challenging and can even increase in concentration due to precursor conversion.

• Photocatalytic Defluorination: photocatalysis uses light-activated catalysts like titanium dioxide to generate reactive species that can degrade PFAS. This method has relatively low energy requirements, but its PFAS destruction rates have been significantly lower than other technologies like EO.

Environmental Considerations For PFAS Destruction

Destroying PFAS responsibly includes protecting the environment from further contamination. Complete PFAS destruction, preventing the release of hazardous byproducts, managing PFAS-contaminated waste streams, and addressing the broader environmental justice implications are key factors when planning a destruction strategy. The following issues should be addressed:

• Incomplete Destruction And Byproduct Formation: Thermal treatment/incineration may not entirely destroy PFAS and can generate problematic byproducts like fluorinated organic compounds, HF gas, and contaminated ash/residues. Incomplete destruction can lead to the release of smaller PFAS molecules or other hazardous byproducts that can reenter the environment.

• Air And Soil Pollution Risks: Incineration and other thermal processes can release PFAS and other pollutants into the air, potentially contaminating nearby soil and water. There are reports of higher PFAS concentrations found in air, soil, and surface water near PFAS incineration facilities.

• Waste Management Challenges: PFAS-contaminated waste streams like ash, sludge, and filters from treatment processes must be handled appropriately to prevent further environmental release. Landfilling or deep-well injection of PFAS waste can lead to leaching and groundwater contamination.

• Energy And Resource Intensity: Many PFAS destruction technologies, like supercritical water oxidation, are highly energy- and resource-intensive. The entire lifecycle environmental impacts of these processes need to be carefully evaluated.

• Environmental Justice Considerations: The siting and operation of PFAS destruction facilities can disproportionately impact disadvantaged communities. Proper mitigation of environmental and health risks to these communities is crucial.

PFAS Destruction Case Study

A partnership in West Michigan has created the U.S.'s first high-volume, closed-loop PFAS destruction system. The system uses a combination of technologies, including supercritical water oxidation (SCWO), to effectively destroy PFAS on a large scale. After destruction, the treated water is cooled and discharged to the local wastewater treatment plant, meeting regulatory standards.

Engaging With The Community About PFAS

Given the immense scale of PFAS removal nationwide, local water utilities need collaboration and cooperation from their communities to succeed. First, utilities should employ effective communication strategies to inform the public about their PFAS removal efforts. Utilities should use proactive messaging to ensure they respond to customer inquiries about PFAS with respect, empathy, and transparency. They can create educational materials that cover the water system, the specific PFAS contaminant, existing solutions, and recommended information sources.

Next, utilities should involve community stakeholders to address concerns. Engaging with local leaders, environmental groups, and residents can help utilities understand the community's needs and priorities around PFAS remediation. Collaborative efforts can also help secure funding for PFAS treatment infrastructure, which is critical given the cost of high compliance.

Addressing public concerns and building trust is essential for successful PFAS removal efforts. Utilities should be open and honest about the challenges and limitations of PFAS treatment technologies and the compliance costs that may individuals and communities. Providing clear, science-based information and responding to customer inquiries can help utilities establish credibility and earn the public's trust.

Future Outlook For PFAS Removal And Discharge

Clay-Based PFAS Removal

Research to discover new, better ways to remove and destroy PFAS is ongoing. One solution that promises to be eco-friendly and cost-effective is clay-based PFAS removal. Natural clay minerals like phyllosilicates and oxidic clays have shown promise for adsorbing and removing PFAS from contaminated water and wastewater.

Modified clay minerals, such as those treated with surfactants or amines or combined with polymers and carbon materials (e.g., biochar), have demonstrated even higher PFAS removal capacities. Mechanisms like hydrophobic interactions, electrostatic attraction, and ligand exchange drive the adsorption of PFAS onto clay-based adsorbents.

Researchers have used the partition coefficient to compare the PFAS adsorption capacity of different clay-based adsorbents. Factors like pH, temperature, competing ions, and natural organic matter can influence the PFAS removal efficiency of clay-based systems.

Challenges include improving the regeneration and reuse of clay adsorbents and enhancing PFAS removal efficiency, especially for shorter-chain PFAS compounds. Future research will focus on developing clay-carbon composite materials, like clay-biochar, which may offer improved PFAS adsorption performance.

Anticipated Regulation Changes

The EPA continues to take significant steps to expand the regulation of PFAS discharges from various sources through new and revised New Effluent Limitation Guidelines (ELGs) and enhanced National Pollutant Discharge Elimination System (NPDES) permitting requirements. These actions are part of the agency's broader PFAS Strategic Roadmap to address PFAS contamination.

New Effluent Limitation Guidelines

The EPA has determined that revisions to the effluent limitations guidelines and pretreatment standards for the Landfills Category must address PFAS found in landfill leachate. The EPA plans to propose new ELGs for PFAS manufacturing facilities in the Spring of 2024 and metal finishers by the end of 2024. The EPA also announced plans to develop ELGs and pretreatment standards for landfills, textile mills, and concentrated animal feeding operations (CAFOs) to address PFAS discharges.

Expanded NPDES Permitting

In February 2024, the EPA released draft guidance to help state permitting authorities address PFAS discharges through the National Pollutant Discharge Elimination System (NPDES) permitting program. This will engender comprehensive monitoring and regulation of PFAS releases to waterways from combined sewer systems.

Final Thoughts

In short, PFAS removal is a complex and expensive undertaking that nonetheless is necessary to protect public health and the environment. As PFAS removal and destruction science evolves, it's crucial for utilities to stay informed on current trends and emerging technology. Water utilities should also follow best practices when creating strategies to meet the EPA's evolving rules and guidelines for PFAS removal and destruction and hold polluters accountable for cleanup costs. Likewise, they should partner with community leaders to address health and safety concerns. Working together, utilities and communities can create cleaner, safer water for all.

References:

1. 12 Treatment Technologies – PFAS — Per- and Polyfluoroalkyl Substances (itrcweb.org)
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