Exploring the effectiveness of EOx in PFAS destruction using two different leachate concentration processes, highlighting the differences and efficiencies of each.
By Louis LeBrun, PE
Leachate treatment has long been a standard practice for landfills, addressing contaminants that leach from waste. In recent years, the presence of per- and polyfluoroalkyl substances (PFAS) in leachate has become a critical issue. PFAS, often referred to as 鈥渇orever chemicals,鈥� are synthetic compounds found in various consumer products and industrial applications. These persistent chemicals, originating from diverse waste streams accumulated over decades, pose significant environmental and health risks due to their resistance to degradation and potential for bioaccumulation.
Despite ongoing efforts to reduce PFAS entry into landfills through stricter regulations and improved waste management practices, these substances are expected to persist in leachate for many years. Consequently, a permanent solution for PFAS destruction is essential for sustainable waste management. Electrochemical oxidation (EOx) technology offers a promising and cost-effective method to completely destroy PFAS from common leachate treatment processes such as Ion Exchange (IX) and Foam Fractionation (FF).
This article explores the effectiveness of EOx in PFAS destruction using two different leachate concentration processes, highlighting the differences and efficiencies of each.
Electrochemical Oxidation (EOx) Technology
Electrochemical oxidation (EOx) is an advanced water treatment process that uses electrical energy to drive chemical reactions, breaking down contaminants into non-toxic components. EOx technology involves applying a direct current to electrodes submerged in the contaminated water. This process generates reactive species, such as hydroxyl radicals, which oxidize and break down complex pollutants like PFAS into harmless molecules like carbon dioxide, water, and inorganic ions.
One of the key advantages of EOx technology is its versatility and effectiveness in treating a wide range of contaminants, including PFAS. The process is highly adaptable and can be fine-tuned to target specific pollutants by adjusting parameters such as electrode material, current density, and treatment time. Additionally, EOx systems are compact, easy to operate, and can be integrated into existing treatment infrastructure, making them a practical solution for landfill leachate treatment.
Ion Exchange (IX) Regenerate PFAS Destruction
Ion exchange (IX) systems are widely used in various water treatment applications, including leachate treatment and PFAS removal. These systems employ highly charged synthetic media capable of reversibly capturing soluble contaminants such as metals, organics, and PFAS. Once the media is exhausted, it is regenerated using a brine or solvent solution, which releases the contaminants into a much smaller volume of spent solution. This regenerate solution, often referred to as 鈥渟till bottom,鈥� is sometimes further distilled to remove volatile solvents like methanol.
Figure 1 illustrates a real-world example of IX brine treatment using EOx coming from a landfill in the U.S. The landfill implemented an IX system to treat its leachate, achieving a PFAS concentration factor of more than 1,000x. The resulting brine, rich in PFAS and other contaminants, was then treated with EOx. Lab tests and pilot studies demonstrated well over >96-99.9 percent destruction of PFAS, with both long and short-chain compounds effectively converted to their elemental building blocks, such as CO2, H2 gas, and water. In cases where laboratory testing shows destruction efficiencies for some compounds of less than 99 percent, the operating conditions for full-scale treatment can be adjusted to yield higher results. The adaptability of EOx allows for adjustments in operating conditions to meet stringent regulatory requirements, showcasing the technology鈥檚 flexibility and efficacy.
The primary advantage of IX in leachate treatment is its ability to achieve extremely high concentration factors, often exceeding 1,000x. However, IX brine also concentrates organics, salts, metals, and solvents, which can complicate disposal. Fortunately, EOx systems benefit from the higher salt concentration in IX brine, enhancing current transfer efficiency and requiring less pretreatment to initiate the EOx process.
Foam Fractionation (FF) PFAS Destruction
Foam Fractionation (FF) is a newer technology that has gained attention for PFAS removal and concentration. FF systems use the hydrophobic nature of PFAS molecules by injecting fine bubbles into the water. PFAS molecules preferentially adhere to the bubble surfaces, which are then collected and concentrated in a foam or 鈥渇oamate鈥� for destruction.
The FF process involves injecting air or another gas into the contaminated water, creating a column of fine bubbles. As the bubbles rise, hydrophobic PFAS molecules attach to their surfaces and are transported to the top of the column, where they form a stable foam. This foam, enriched with PFAS, is then collected and processed for further treatment or destruction.
A case study from a landfill in the U.S. highlights the effectiveness of FF combined with EOx. The landfill鈥檚 FF system concentrated PFAS from leachate, achieving a concentration factor of more than 500x. The collected foamate, containing high levels of PFAS and other organics, was treated with EOx. Lab tests showed more than 98.8 percent PFAS destruction, along with significant reductions in chemical oxygen demand (COD), demonstrating the technology鈥檚 capability to handle complex waste streams.
FF systems generally provide good results in highly contaminated water, such as leachate, with concentration factors ranging from the mid-100s to about 1,000. Some multi-stage technologies can achieve even higher concentration factors. Figure 2,聽 data shows that FF provided lower total PFAS and salt concentrations with a higher concentration of PFAS precursors and other organics (measured by COD).
Electrochemical oxidation lab testing demonstrates excellent performance in treating FF-derived foamate, achieving more than 98.8 percent PFAS destruction while also removing a high percentage of other organic waste products (COD). Additionally, both FF and EOx offer compact footprints and are typically delivered as containerized systems, making them suitable for quick deployment or remote locations where existing buildings may not be available.
Images courtesy of Axine Water Technologies.
Effective Solutions
Regardless of the pretreatment method used, electrochemical oxidation offers an excellent follow-on process for PFAS destruction in landfill leachate. While IX brine and FF foamate streams provide the best economic benefits due to their high concentration factors, concentrates from other conventional treatment processes, such as ultrafiltration (UF) and reverse osmosis (RO), are equally well-suited for PFAS destruction using EOx.
The flexibility, simple operation, cost-effectiveness, and rapid ability to deploy EOx systems make them an ideal choice for landfills seeking effective solutions for PFAS management. As regulatory pressures increase and the need for sustainable waste management practices grows, EOx technology stands out as a promising tool for addressing the persistent challenge of PFAS in landfill leachate | WA.
Louis LeBrun, PE, is a professional engineer with more than 25 years of experience in water and wastewater treatment, including advanced oxidation and electrochemical oxidation processes. During this time, he has been involved in delivering treatment solutions and commercializing treatment technologies throughout North America, South America, Europe, and Asia. In his current role as Vice President of Sales at Axine Water Technologies, he is responsible for the delivery of treatment solutions worldwide. Louis can be reached at (919) 996-9372, e-mail [email protected] or through LinkedIn at .
Look out for Axine Water Technologies鈥� articles on electrochemical PFAS destruction in past and future issues. For more information about Axine Water Technologies鈥� electraCLEAR庐 electrochemical oxidation process, call (604) 336-8900 or visit www.axinewater.com.