Granular activated carbon and ion exchange are two technologies proven effective in treating waters that contain PFAS.

One issue with both is that, as in other applications, the carbon or ion exchange resin accumulates the pollutants and then must be either regenerated or disposed of responsibly. De Nora now offers GAC and ion exchange treatments that reduce PFAS to nondetectable levels.

The company’s preconfigured SORB systems include a regenerable multi-use ion exchange technology now being pilot tested. It can be paired with electrochemical advanced oxidation processes, significantly prolonging resin use and reducing the need for media disposal.

The GAC and ion exchange systems are optimized locally depending on variables such as flow, seasonality and the targeted contaminants. The treatments are proven up to 99.99% effective with features designed to streamline processes from installation to operation, according to the company.

Units are configured with features that allow maintenance to be done from outside the tank, reducing the need for permits, added personnel or media removal. Nicholas Armstrong, product manager for organic and inorganic contaminant removal, talked about the treatments in an interview with Treatment Plant Operator.

How did these technologies fit into the realm of PFAS treatment?

Armstrong: Granular activated carbon has been used in industry for generations for multiple applications in organics treatment, and ion exchange has been widely used for removal of inorganics. The systems we supply today are large steel vessels containing media that’s specific to removing a contaminant of concern. With PFAS, there is no silver bullet of technology. You have to look at the water chemistry and cater to the site-specific need.

How do your technologies deal with PFAS-contaminated drinking water?

Armstrong: We have standardized the product line to take some of the guesswork out of the system and vessels. Our GAC offering, SORB CX, is effective on lower-challenge long-chain PFAS and for waters that contain other organic contaminants, such as chlorinated compounds and disinfection byproducts. Now with advanced analytical techniques that can identify more and more PFAS in drinking water, along with the updated advisories released by the EPA in June, the market is moving more toward ion exchange.

What are the advantages of ion exchange technology?

Armstrong: Ion exchange uses a synthetic formulated media that can be specifically tailored to target PFAS. Because of ion exchange properties in which positive and negative charges are attracted to each other, it can remove not only long-chain, but some short-chain PFAS.

Can these two types of media be used in tandem?

Armstrong: Yes. Where you have a large amount of PFAS in the water along with other organic compounds, you can combine the two technologies. A GAC system up front does the heavy lifting and knocks out the organics, and ion exchange on the back end takes out the PFAS. Another advantage of ion exchange is that it has capacity for regeneration. The key is to identify how we go about destroying PFAS and what the destruction technique looks like.

How are spent GAC and ion exchange media typically dealt with now?

Armstrong: Typically, the carbon and ion exchange media, once used and exhausted, needs to go to an incinerator to be destroyed. Whether that truly destroys the PFAS or just moves the problem from the water to the air is still an open question. Ion exchange with a destruction process on the back end is ultimately where we need to go. We want to concentrate the PFAS and then pass it through a process for destruction.

What is your company’s approach to destruction of PFAS?

Armstrong: It is an electrochemical process that uses an anode and cathode reactor, formulated using a specific type of metal base and a proprietary coating. After concentrating the PFAS on the ion exchange resin beads, we use high-salinity water to rinse the PFAS off. Now you have a concentration of salinity and PFAS, and that’s where this electrochemical process comes in.

What is the nature of the destruction accomplished by the electrochemical process?

Armstrong: It breaks the chain of the fluorocarbon bonds, and the resulting materials are absorbed into the coating of the reactor. So ultimately, you can have the ion exchange resin on site for multiple years without having to move it to a regeneration facility. An additional benefit is that the destruction process is not energy intensive. It is not a thermal process.

Is there still a waste product that needs special handling or disposal?

Armstrong: There is still a waste stream in the form of saline water. The expectation is that this water would simply contain chlorides and could either go direct to the drain or to treatment on the wastewater side.

Has the electrochemical destruction process been proven in the field?

Armstrong: While still in the early stages of development, it has been used in applications involving high concentrations of PFAS, like landfill leachate, and it has shown promising results.

What differentiates your PFAS removal offerings from other GAC and ion exchange technologies?

Armstrong: On the GAC side we use a carbon that is specifically formulated to optimize PFAS removal. It’s a combination of carbons specified for the application. And on the ion exchange side we have the regenerable solution that we expect can pair with a destruction technology on the back end. Another differentiator is on the system design side, the optimization of flow through the media to deliver maximum removal.

How is the regeneration and destruction technology actually deployed on a site?

Armstrong: Much of that is still very much in the piloting stage. The expectation is that this process would be done as service, meaning that a mobile asset would come to site to perform the regeneration and destruction process. Ultimately, a cost analysis should be done to identify what is the right solution for each specific site. We believe our regeneration package will set the standard for the future, allowing utilities to promise safety for both water and the environment.