John Brockgreitens, Claros Director of Research and Development

Clean freshwater is one of our most valuable natural resources, especially in the parched West. What if there were a “blue bin” that could be used to recycle industrial wastewater laden with pollutants into clean potable water? Widescale capture and treatment of wastewater so it can be reused for drinking, irrigation and industry would be a boon to municipal water supplies. New technologies hold the promise of making water recycling safe and cost-effective.

There is a lot of buzz surrounding per- and polyfluoroalkyl substances (PFAS) these days. The rising concern stems from the fact that PFAS are ubiquitous, hazardous and so environmentally persistent that they are called “forever chemicals.” PFAS can harm human health, having been linked to various cancers, hormone disruption, weakened immunity and reproductive problems. The “forever chemicals” also harm the environment, especially aquatic ecosystems downstream of industrial and wastewater treatment plants.

PFAS Regulation Accelerates

PFAS don’t break down naturally and their carbon-fluorine (C-F) bonds — the strongest bond in organic chemistry — are incredibly difficult to break. This family of chemicals resists grease, water and oil so well that they are used in everything from cookware to cosmetics to firefighting foams. They are so useful that more than 9,200 PFAS compounds have been created since their introduction in the 1940s. The U.S. Environmental Protection Agency (EPA) regulates at least 40 PFAS, but regulations are quickly expanding at the state level as well as the federal level.

The EPA recently released Effluent Guidelines Program Plan 15 (Plan 15), which “will work to protect the nation’s waterways by following the science and the Clean Water Act to develop technology-based pollution limits and studies on wastewater discharges from industrial sources.” The EPA plans to revise effluent limitations guidelines and pretreatment standards (ELGs) to reduce PFAS in leachate discharges from landfills. The agency also announced new studies including one of industrial effluents to publicly owned treatment works (POTW) to inform the development and implementation of pretreatment programs to address PFAS. These actions, which follow the path laid out by the EPA’s PFAS Strategic Roadmap, are critical to developing water recycling best practices that can be assuredly safe and brought to scale.

States Support Recycling Water

There is growing support for water recycling at the state level. The Alliance for Water Efficiency’s 2022 State Policy Scorecard for Water Efficiency and Sustainability reported that 14 states have both water-use regulations and funding in support of reuse projects. California topped the water reuse ranking because of initiatives such as Prop 1, which provides $625 million in funding for recycled water projects. Texas took second place and Arizona third in the rankings. An additional 15 states had reuse regulations without funding.

These trends are increasingly important because of climate change. The Alliance for Water Efficiency said nearly every state experienced drought in 2022. Water recycling is critical to building water resiliency.

PFAS Challenges Wastewater Treatment

Municipal wastewater treatment plants (WWTPs) are facing increased scrutiny since they are a major source of PFAS contamination. Take, for example, one study that named WWTP effluents as the main source of PFAS discharged into Lake Ontario and another study that found eight municipal WWTPs that discharged PFAS-laden effluents into San Francisco Bay.

PFAS enter wastewater treatment plants from three primary sources: consumer-use products that are flushed down the drain, industry effluents, and landfill leachates. The problem is that conventional wastewater treatment technologies only break down long-chain PFAS compounds into small-chain compounds that are emitted in the resulting sludge or effluent.

These short-chain PFAS are likely the reason why higher concentrations of PFAS are often measured in wastewater effluent and sludge than in the influent. For example, a paper published in Water Solutions in 2020 reported findings of studies that tested for 17 PFAS compounds at four U.S. wastewater treatment plants. The sludge measured 0.018–0.049 parts per million (ppm) before treatment and 0.008–0.123 ppm after treatment with heat or composting. Sludge incinerators operate at temperatures of 800-900°C, yet breaking down PFAS requires temperatures exceeding 1,000°C.

PFAS in treated sludge and wastewater effluent negatively affects watersheds. An analysis of U.S. drinking water found a strong correlation between the number of wastewater treatment plants within a watershed and PFAS concentrations in public water supplies. Higher concentrations of PFAS could lessen the ability to safely reuse the water for drinking and irrigation. Research should be conducted to determine what — if any — concentrations of PFAS in wastewater are safe.

Remediation still falls short

PFAS remediation is still in its nascent phase. Most commercially available PFAS tests detect fewer than 40 PFAS compounds and testing development seems to lag behind the growing list of known and regulated ones, particularly with increasing calls for a class-based approach to PFAS management. The EPA recently published a draft method for adsorbable organic fluorine (AOF) that analyzes PFAS as a class. Such a class-based approach holds a lot of promise, but AOF has some shortcomings. It is less sensitive, does not provide compound-specific information and is biased toward long-chain compounds.

There are various separation technologies that can applied to wastewater once PFAS has been identified. Reverse osmosis, foam fractionation, ion resins and granulated activated carbon are the most common methods used to filter out PFAS. Yet these methods have a hard time capturing short-chain PFAS, especially in complex wastewater with high concentrations of other organic compounds and competing ions.

Waste products from these separation technologies including spent filter media and liquid PFAS concentrates are then sent to landfills or incinerated, which doesn’t destroy PFAS but rather transfers the compounds to other environmental matrices. Incineration has been found to break long-chain PFAS into short-chain fluorinated molecules that are then dispersed to surrounding areas by ash and smoke. The U.S. Department of Defense recently banned incineration as a method of disposing of PFAS and some states are following suit.

In addition to the recontamination issue, the limited options available for landfilling and incineration are becoming increasingly expensive and the originator of the waste may still hold significant liability risk.

Where Innovation Flows

Innovative technologies hold the promise of permanently destroying PFAS.

The first step is testing that uses both compound-specific methods and class-based methods such as AOF and total organic fluorine (TOF). This in-depth analysis is used to design highly customized remediation strategies.

The second step is PFAS capture and concentration using new proprietary chemistries and methods that prove more efficient and effective. They can be used alone or in conjunction with existing capture systems such as ion resin and foam fractionation, paving the way for wide-scale adoption. Reducing millions of gallons of wastewater into only a few gallons of PFAS concentrate makes destruction much more manageable and affordable.

The final step is permanent destruction of PFAS through defluorination.

Recycling water is one of the best hopes for maintaining access to reliable, safe water sources for communities nationwide. Water resilience is increasingly important since climate change is predicted to threaten water availability and water quality. New technologies that provide robust testing, capture and concentration and permanent destruction of PFAS can instill confidence that recycled wastewater can be safely used for drinking, irrigation and watershed restoration without any harm to human or environmental health.

John Brockgreitens holds a Ph.D. in Biosystems Engineering from the University of Minnesota, and his expertise includes the development and application of nanomaterials in environmental systems. John serves as a Director of Research and Development for Claros Technologies, a company providing testing, capture, and destruction technologies for PFAS, heavy metals, and mercury pollutants.