In helping our clients respond to the increasing concern about liabilities from use and impacts by Per-and Polyfluoroalkyl Substances (PFAS) to soil, sediment, water and air, we find a multidisciplinary approach including geology, hydrogeology, toxicology, risk assessment and remediation provides the breadth of knowledge and experience needed to practically address the emerging issues with these substances and provide a basis for implementing effective solutions.
The issues surrounding PFAS are complex, as shown in a case in which we were called upon to assess the unintended consequences of a fire response at an oil storage depot nearly two decades ago, when PFAS were still unknown to many. Fighting the fire had involved use of aqueous film forming foams comprised of a mixture of chemicals that included PFAS. The depot was located over an aquifer used as a drinking water source. A year after the fire, PFAS were detected in a sentinel well near the depot, we were called in to determine the extent of the contamination and perform assessments of risks to groundwater. Two years later, we were retained as an expert witness in a trial regarding the fire and its aftermath.
In projects such as this, we draw on experience dealing with a wide range of materials including asbestos, PCBs and chlorinated solvents -- all of which entered the market as innovations. In time, however, they were eventually found to have the potential for unintended environmental or human health impacts. This has led to legislation to curtail or stop the use of these substances, and to mandate the investigation, risk evaluation and remediation of sites affected by chemicals of concern.
In a similar vein, PFAS compounds were first developed over 50 years ago and became popular due to their resistance to oil, heat and water. Thousands of different PFAS have been manufactured over the years and incorporated into a host of industrial processes and products – non-stick cookware, paints, cosmetics, electronics, construction materials, breathable waterproof outerwear and firefighting foam, to name just a few.
Then, researchers began to associate certain PFAS with a range of potential health and environmental effects, bringing increased pressure to stop the production and use of some types of PFAS (starting with Perfluorooctanesulfonate (PFOS) and Perfluorooctanoate (PFOA)), and to clean up PFAS-contaminated soil and water. Regulatory environmental criteria for some PFAS are now in effect in several jurisdictions around the world and are often orders of magnitude lower than those for chlorinated solvents. While current criteria generally target a small number of PFAS and are typically limited to soil and drinking water, governments are working on environmental criteria for a larger number of individual PFAS and maximum concentrations for the sum of certain PFAS, environmental media and exposure pathways.
To assess and manage their environmental liability, our clients are coming to us with questions about how best to assess and treat PFAS in soil, water and other matrices, and why dealing with PFAS can be so challenging. There are several reasons why including their widespread use and persistent nature, which may result in migration over long distances. Consequently, it’s extremely important to differentiate impacts from multiple PFAS sources or background concentrations. To assist with this, we have developed rigorous, but practical Standard Operating Procedures (SOPs) to collect representative samples for a variety of media and limit the high potential for cross-contamination. We have also assisted clients with the development of specific SOPs for their sites portfolio and helped them with the prioritization of sites for PFAS investigation based on potential environmental liability.
When it comes to PFAS investigations, the approach is unique in view of their different properties compared to most conventional contaminants and considering the large number of compounds, precursors and breakdown products, the evolving regulatory environment, complex source compositions, fate and transport as well as the potential effect of historical site remediation. To efficiently tackle these complexities, we have developed a flexible site investigation framework that sequentially leads the assessor through site identification, conceptual site model development, identification of PFAS of concern, site investigation methods and data interpretation. By using a novel visualization tool to analyze PFAS signatures in the context of a multiple lines of evidence approach, we can efficiently differentiate multiple PFAS sources or background concentrations within the same site and across sites, illustrate how mixtures of PFAS can vary as a result of fate and transport, and assess PFAS partitioning between different environmental media (e.g., surface water vs. sediment vs. fish tissue concentrations).
Due to the strength of the carbon-fluorine bond, the large number of PFAS and their varying properties, and the very low regulatory criteria, remediation of PFAS is facing several challenges. Landfills are becoming more concerned about the migration of PFAS from impacted soil or other materials to leachate. Also, in some jurisdictions legislation regulates what levels of PFAS-contaminated soil the landfills can accept. The same is happening with PFAS-impacted water where only specialized wastewater facilities and a few industrial liquid waste contractors are able to accept and effectively deal with water contaminated with PFAS.
Treatment effectiveness and costs vary depending on regulatory criteria that must be achieved and PFAS contamination levels. Granulated activated carbon (GAC) is one of the most frequently used options for treating PFAS-impacted water. However, treatment involves the use of large amounts of GAC, meaning costs are higher than for more conventional contaminants. Furthermore, this technology is not always effective for all types of PFAS and requires costly regeneration or disposal of the spent carbon. Ion exchange resins can be effective for water treatment in some cases, but produce a PFAS reject stream and also require regeneration or disposal of the spent resin. Incineration for both liquid and solid PFAS-impacted material requires temperatures of over 1,000 degrees C to break down the compounds, making it generally suitable for small volumes only. Furthermore, evaluations are still being conducted to confirm full destruction of PFAS and prevent the formation of by-products associated with incomplete destruction.
Other solutions have been tested, but there is a lack of sustainable solutions that destroy PFAS.
Innovative solutions are needed to effectively remediate PFAS impacted soil and water. Beyond optimizing currently available technologies, we are collaborating with universities and research groups in North America, Europe and Asia-Pacific to develop new, cost-effective solutions and to advance science and knowledge on PFAS.
We find that while PFAS management presents specific challenges and each site demands consideration of its unique aspects, the innovative tools and experience we have developed are yielding positive results for our clients.
ABOUT THE AUTHOR
Stefano Marconetto, is a Global PFAS SME and Senior Principal Environmental Engineer at WSP*, working out of Ottawa, Ontario. Stefano has provided strategic and technical direction on PFAS projects for government and private clients across all market sectors globally for over a decade. He is a technical advisor for several PFAS research projects in collaboration with academia and industrial partners.
* The research and development of this technology was initially conducted by Golder professionals who joined WSP in an acquisition completed in 2021.
