Spotlight on Polyfluoroalkyl Substances in the environment
In this article we will dive into the impact of polyfluoroalkyl substances (PFAS) on our lives and the environment. We will discuss what these compounds are, where they came from, why they are in the spotlight, and most importantly how to remove them from our environment. While the significant health effects will be discussed, the primary focus will be on the effects to the drinking water, biosolid, and wastewater treatment industries from PFASs.
What are PFOS and PFOA & Why Do They Matter?
PFOS (Perfluorooctane Sulfonate) and PFOA (Perfluorooctanoic Acid) are part of a class of fully fluorinated, man-made, organic compounds called polyfluoroalkyl substances (PFAS). They are persistent, mobile, bioaccumulating, and can be found in the air, soil, water systems, and groundwater. Complicating matters is that these compounds are also very resistant to conventional chemical and biological treatment technologies to remove them. Their extreme persistence and mobility, along with the ineffectiveness of standard treatment technologies, have allowed PFASs to spread throughout the world. These compounds have been found in all oceans and every continent, including Antarctica. Due to the major health issues associated with exposure to these compounds, this is a big problem. PFASs have been linked to developmental, reproductive, and systemic issues including: high cholesterol, increased liver enzymes, decreased vaccination response, thyroid disorders, pregnancy-induced hypertension and preeclampsia, and various cancers. PFASs are typically absorbed through oral exposure via inhalation or ingestion.
Where Did PFOS and PFOA Come From?
Due to their excellent ability to repel water and oil, PFASs have been used in a variety of applications and markets including: non-stick cookware, thread seal tape, and as a surface protector on various clothing, carpets, furniture, paper products (including food containers), and cardboard packaging. Another major source is aqueous film forming foam used to extinguish liquid hydrocarbon fires. With the realization of the potential environmental and health impacts, very few new products use PFASs. However, there are many existing products still in circulation as well as existing stocks of aqueous film forming foams that allow exposure of these compounds to persist.
Why Are PFASs in the Spotlight?
While the potential impact on the health and environment was already known, the spotlight has been focused on these compounds because the EPA recently announced that it has started maximum contaminant level proceedings for PFOA and PFOS in accordance with the Safe Drinking Water Act. Also, research indicates that biosolids can contain these compounds in significant amounts (even if there is no industrial loading), and the compounds are mobile through biosolids to the groundwater when land applied. Finally, while biosolids do retain some of the PFASs, results indicate that pass-through in wastewater facilities is also occurring. This means that regulation of PFASs is likely in the works for drinking water, biosolids, and wastewater.
How are PFASs Currently Treated?
There are five primary approaches to removing PFASs:
- chemical degradation and precipitation
- activated carbon
- ion exchange resins
- nanofiltration
- reverse osmosis.
Activated carbon and ion exchange both can work well but require very specific types of carbon / resin to remove all types of PFASs (particularly PFOA and PFOS). These approaches are also subject to various interferences for activated carbon this would include Dissolved Organic Matter (DOM) and for ion exchange resins this would include bicarbonate, chloride, sulfate, and nitrate.
Nanofiltration and reverse osmosis are both very good options for removing PFASs. Both approaches remove all forms of PFASs to negligible levels. However, the capital expenses involved can be prohibitive, particularly for large water and wastewater systems.
Conventional oxidation, coagulation, and sedimentation techniques are the most amenable to large scale water/biosolid treatment. However, such techniques are ineffective in removing PFASs. As a result, Independence Solutions began working on a solution that allows removal of PFASs via conventional approaches. In a collaborative effort, we reached out to Dr. Benjamin Harrison chief chemist of Mainland Solutions, LLC about possible solutions. Mainland Solutions develops custom chemical solutions for challenging remediation projects. According to Dr. Harrison, one of the best ways to deal with PFASs would be reactive degradation via the Fenton reaction. This reaction generates a superoxide molecular species that reacts with PFOA/PFOS to deactivate them (Mitchell, et. al. Environ. Sci. Technol. Lett., 2014, 1 (1), pp 117 – 121). Dr. Harrison went on to say, “Unfortunately, high reagent concentrations and/or high temperatures are usually needed to do this efficiently and thus not suitable for large water or wastewater treatment systems”. His company has developed a product which allows the Fenton Reaction to work at normal temperatures and also at relatively low dose rates. Their product produces a more potent Fenton-like reaction, irreversibly entrapping PFASs for removal via precipitation. This approach is appealing because it can be implemented with most traditional water and wastewater treatment equipment and requires relatively low chemical feed rates. Independence Solutions provides all required chemistry, service, and expertise to execute this program effectively and efficiently.
While there are treatment options available, it is important to understand each approach’s unique requirements and limitations. Among other considerations; capital costs, operating expenses, equipment footprint, and current processes should all be examined before moving forward. Independence Solutions can help you find the approach that is most suitable for your treatment needs. We treat every project with a unique approach and fresh thinking. Feel free to contact us anytime via our website independencewater.net