Per- and polyfluoroalkyl substances (PFAS) have been a major environmental concern globally due to their persistence and potential health risks. PFAS are widely used in industrial and consumer products, such as non-stick cookware, waterproof clothing, and firefighting foam. The landfill industry is one of the sectors affected by the presence of PFAS in leachate and groundwater. Landfill operators face a significant challenge in treating and managing PFAS-containing waste streams. In recent years, several treatment methods have been developed to address the PFAS problem, with foam fractionation emerging as a promising technology, having several advantages over alternative treatment methods.
Understanding the Basics of Foam Fractionation
Before we delve into the pros and cons of various treatment methods, it is essential to understand the basics of foam fractionation. Foam fractionation is a physical separation process that separates dissolved or suspended substances based on their affinity to adsorb to the surface of air bubbles generated in a foam column. The foam is generated by injecting air into a column containing a solution with the target compound. The target compounds are then adsorbed onto the surface of the air bubbles and are subsequently separated from the liquid phase as the froth rises from the column. The separated target compounds are then collected in a foam concentrate, while the purified liquid effluent is discharged. Foam fractionation has been used in several industries, including aquaculture, wastewater treatment, mining, and food processing.
Alternative Treatment Methods
Another alternative method for PFAS treatment is reverse osmosis (RO), a process that uses a semi-permeable membrane to separate contaminants from water. While RO is effective at removing PFAS, it is a costly process that requires high energy inputs, which translates to increased operational costs. Moreover, the concentrate stream generated during RO treatment can range from 10 to 20 percent of influent flow, and it contains high levels of PFAS, which requires further treatment or disposal.
Ion exchange resins are also used to remove PFAS from wastewater. Ion exchange resins work by exchanging ions in the liquid phase with ions attached to the resin surface. However, ion exchange resins can be limited by their capacity for the same reasons as activated carbon in complex water types. Generally, PFAS resins are not regenerated so the process can generate high volumes of waste.
Foam Fractionation as an Effective Method
Foam fractionation as a method is very effective at removing PFAS compounds because they are surfactants and have a hydrophilic and a hydrophobic end. The hydrophilic end ‘prefers’ to be dissolved in the water, but the driving force for the hydrophobic end to adhere to the surface of the bubbles is much stronger and results in the selective and efficient extraction of PFAS compounds. The main water stream is then discharged after having been treated for PFAS. Compared to alternative methods, foam fractionation has several advantages:
• Effective at removing PFAS from a wide range of industrial and municipal waste streams, including landfill leachate and groundwater.
• High capacity for PFAS removal, making it an efficient process that requires less material and energy inputs.
• Generates a low volume of foam concentrate that is more easily managed, minimizing environmental impacts.
• Foam fractionation is a simple and scalable process that can be adapted to various industrial and municipal settings.
• Can be integrated with other treatment methods to create a comprehensive treatment system.
When it comes to the daunting task of choosing the best long-term solution and investment for vital technologies (PFAS treatment in this case), it is easy to get caught up in the fervor of one’s own expertise or simply hire a broad-spectrum engineering firm. That is where we can overlook the importance of acknowledging the contributions of other technologies that may be more ideal to the site. There are experts out there to help and they should be able to provide multiple references from technologies that you are relying on for the long term.
While we may have our preferred methods of vetting solutions, it is essential to recognize that each solution has its unique advantages and drawbacks. By working strategically with this in mind, we can create a technological ecosystem that is not only efficient and effective, but also sustainable and inclusive.
In conclusion, as we continue to advance in technology, let us not forget that the true power of innovation lies in collaboration and diversity. When it comes to vital technologies, let’s strive to create a future that is not only cutting-edge, but also equitable and just for all. | WA
Innovative Fractionation System Technology in Australia
In Australia, where earlier regulations provided a head start in developing foam fractionation technology, one of the most notable examples is the Low Energy Evaporative Fractionation (LEEF) System®. In so many words, they got ahead of the curve. This is an innovative proprietary technology deployed at full scale at a leachate plant owned by the City of Darwin, in the Northern Territory, Australia. To address the problem of leachate in Darwin’s unique environment and weather .conditions, the City of Darwin awarded the Water & Carbon Group (WCG) a contract to design, construct, and operate a custom leachate treatment plant solution.
At the facility, the LEEF System® will treat 14 million gallons of leachate each year, removing PFAS contaminants using foam fractionation with minimal energy and no chemicals. In order to remove additional contaminants of concern, treated effluent from the LEEF System® is then further processed via a biological treatment plant, which uses microbes for nutrient removal, and a treatment wetland for polishing. The treated leachate is used to irrigate a vetiver grass crop, allowing for phytoremediation (a process whereby plants are used to clean up the remaining contaminates, and evapotranspiration) to provide a zero-discharge treatment plant. This is a permanent facility treating PFAS in leachate coupled with biological and ecological treatment and zero disposal—a closed loop system. In full production, the plant is processing up to 37,000 gallons of leachate a day. To date, the system is operating as designed and consistently meeting regulatory limits.
Brad Granley from Leachate Management Specialists (LMS) said two of the biggest advantages of the LEEF System® include its modular format and operational flexibility, making it easy to provide the right options to meet the complex needs of almost any leachate treatment project. “As an experienced engineer with a scientific thought process, I would not have thought the results produced by the LEEF System® were possible, But having operated the system and collected samples myself, I’m amazed at the removal of PFAS compounds down to very low ppt and non-detect levels. We were called on as professionals in this industry to develop saving solutions to this PFAS problem and this is exactly the tool our industry needs to secure disposal of leachate at wastewater treatment plants; and we can feel good about it because we’re also protecting the environment,” Granley said.
Recently, the LEEF System® further demonstrated the ability to remove PFAS compounds down to very low levels by pilot testing 12 different leachates, including RO reject, from six different landfills in the U.S. Delivered by WCG in partnership with U.S. partner LMS, the demonstrations were a huge success.
Originally published in Waste Advantage Magazine