PFAS Contamination in the Environment
Per- and polyfluoroalkyl substances, such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are a large and complex class of anthropogenic compounds often referred to, collectively, as PFAS. Since the 1950s, PFAS have been widely used in industrial and residential applications. Their stability and unique chemical properties are used to produce waterproof, stain-resistant, and non-stick qualities in products. They are found in some formulations of aqueous film-forming foam (AFFF) used for firefighting, as well as metal plating baths, oil surfactants, and a variety of consumer products, such as food packaging materials.
The prevalence of PFAS contamination in the environment has been recognized globally and is now becoming more of a focus throughout the United States.
Concerns regarding PFAS center around the potential health effects; particularly, when groundwater reaches drinking water sources, as has been documented at numerous sites. The human health risks have been recognized by the U.S. Environmental Protection Agency (USEPA). The carcinogenic potential of PFOA and PFOS has been categorized as suggestive based on peer-reviewed studies of the effects of long-term, high-level exposures on laboratory animals. The key issue for remediation is that these chemicals are persistent and bioaccumulative in the environment, and they are potentially harmful even at extremely low levels (i.e. parts per trillion).
Significant efforts have been made in the United States and globally to better understand the prevalence of PFAS compounds in the environment. PFAS have been detected in a range of exposure pathways, including surface water, groundwater, drinking water, sediment, fish, and more. Identified sources include the use of AFFF at federal government and state airports, primary manufacturing plants that use PFAS in production, intermediate manufacturing facilities, and waste disposal facilities, such as landfills.
The decision to remediate PFAS should be driven by applicable regulations and an appropriate risk assessment. In addition, every site should be adequately characterized and a comprehensive conceptual site model (CSM) should be developed to guide decision making regarding where and how to control the source and transport of PFAS impacts. IRTC has compiled tables to summarize technologies, most of which have only been tested in limited applications or in laboratory bench tests.
There is a significant amount of publicly available information on products, sites, health risks, and extent of contamination present. Below is a list of links to information that may be of interest.
Interstate Technology & Regulatory Council (ITRC) PFAS Fact Sheet
National Groundwater Association (NGWA) Groundwater & PFAS: State of Knowledge and Practice
PFAS Remediation Options for Groundwater, Surface Water, and Sediments
While it is known that PFAS impacts extend beyond groundwater (drinking water) to soils and sediments, remediation efforts to date have centered almost exclusively on the drinking water issue. With regards to groundwater, most remediation activity has been centered on pump and treat systems that extract groundwater and remove contaminants on an ex-situ basis. These systems are often being employed in an effort to control a groundwater gradient that is driving a contaminant plume.
The primary challenge with any in-situ remediation effort are the unique chemical properties and very low target treatment levels, which have created the need for new technologies or innovative combinations of existing technologies. Because PFAS compounds are highly soluble in water and can be transported rapidly through surface run-off (e.g. surface water), infiltration into groundwater or from surface water contact with impacted sediments (e.g. in a basin, detention pond, lake or river), the ability to use available technology to limit the transport of PFAS is an important consideration.
In-situ vs Ex-situ Remediation
Remediation or treatment approaches can be applied to a target contaminant either after removal (ex-situ) or in place (in-situ). Options and approaches are available for conventional groundwater, soil, and sediment remediation that can be performed utilizing methods and technologies which allow for either ex-situ or in-situ options/approaches. Most available technologies only offer ex-situ approaches, generally requiring more cost that passive, in-situ approaches (where available). Although remediation approaches in-situ PFAS removal from water have not been widely implemented, AquaGate+RemBind offers a new tool for this application.
New technologies are being tested and piloted on an ongoing basis, but it is likely that combined technologies may be required to overcome limitations of any one approach and to improve performance or efficacy of a given technology. More information can be obtained here.
Using RemBind® for Treatment of Surface Runoff, Groundwater Seeps and Sediments
RemBind ® was developed in Australia by CSIRO and is manufactured by RemBind, Pty Ltd., a subsidiary of Ziltek, Pty Ltd., as an in-situ amendment for PFAS contaminated soil. RemBind ® is an adsorptive reagent for PFAS immobilization and sequestration. It is a patented material that combines activated carbon, aluminum hydroxide (amorphous) and natural kaolinite clay to create high internal surface area and mixed charges that bind PFAS compounds via electrostatic (ionic) and hydrophobic interactions, Van der Waals forces (adsorption), and physical interactions. This multilevel binding reduces the aqueous concentrations and soil leachability of PFAS, mitigating human and ecological exposure risks. RemBind ® has been successfully utilized to manage PFAS impacted soil in several large-scale Australian projects and has since been utilized in other countries including USA, Denmark, Germany, and Sweden.
Together with RemBind, AquaBlok has developed and now markets AquaGate+RemBind (described below), a composite product that is used to treat PFAS in groundwater and surface water through permeable reactive barriers (PRBs). AquaGate+RemBind can also be used to address PFAS impacted sediments, much like our other AquaGate materials.
AquaGate+RemBind Placed in Gabions for Passive Removal of PFAS from Stormwater. Read more case studies on our Downloads Page.
The AquaGate+RemBind Approach: Combining AquaGate+ Delivery and RemBind® for In-situ Treatment of Groundwater Seeps, Surface Water Runoff and PFAS Impacted Sediments
Over the last ten years, AquaBlok has successfully used and expanded the AquaGate®+ approach in a wide range of groundwater and sediment remediation applications. AquaGate+PAC has been applied at multiple U.S. Navy sites and was awarded the ESTCP Project of the Year in 2016 by the Department of Defence. AquaGate®+ enables cost-effective in-situ treatment by delivering powdered amendments in a thin coating around an inner core; thereby allowing movement of water through the matrix for treatment, while limiting the migration of contaminants. The addition of RemBind as the coating material offers a new tool for implementation of in-situ PFAS remediation. RemBind has been demonstrated to bind PFAS and prevents leaching of contaminants from water and soil in multiple lab and pilot applications. In the field, it has been effective at remediating PFAS contaminated soil by reducing leachable PFAS concentrations by 90-99%. Long term stability of this binding in soils for 100’s of years has been simulated using USEPA Method 1311, Australian ASLP Method, and European DIN Method 19529/38407-42. Soils can then be left on-site or removed and shipped to an approved landfill or other facility.
An Overview of AquaGate+RemBind is provided Below.
AquaGate+RemBind Passive Barrier Treatment System (PBTS)
PFAS impacted surface water is one exposure pathway requiring attention. This is occurring in drainage systems and surface runoff at locations that may not have an identifiable point source, or from runoff from impacted soil and sediment, or through surface seeps from impacted groundwater. For such systems active ex-situ treatment (pump and treat with ion exchange/GAC) may not be technically or economically feasible for several reasons such as intermittent/seasonal flows, restrictive access etc. The development and assessment of a technical and economic system for in-situ remediation of surface waters which will allow for a more sustainable, low-impact and lower cost approach that reduces human health and ecological risk would represent a useful tool in the remediation toolbox. AquaGate+RemBind passive barrier treatment system offers a new tool for implementation of in-situ remediation.
The graphic below illustrates several instances where AquaGate+RemBind would be applied in a PRB/PBTS and the relative advantages of this delivery at mitigating exposure risks of PFAS impacted media.
Combined with RemBind®, the AquaGate® + In-situ treatment approach provides a number of advantages:
Uniform distribution of the amendment promotes a higher contact probability for the PFAS compounds with the adsorptive materials thereby ensuring their removal.
AquaGate®+ particle system maintains high permeability during the life of the remedy thereby ensuring a high treatment efficiency.
AquaGate®+ particle system leverages the rapid kinetics and high adsorptive capacity of powdered amendments over granular amendments. This allows for rapid capture of PFAS compounds without the need for prolonged contact times.
A wide range of amendment materials have been tested and utilized for the removal of PFAS contamination from water. Typical ex-situ water treatment systems use granular activated carbon (GAC). However, in addition to rapid loss of adsorptive capacity, these materials have been shown to have limited success in removing some of the short chain components of PFAS compounds. As a result, a range of other materials (e.g. resin-based) have been developed for water treatment. Unfortunately, these materials cannot be utilized in conventional groundwater treatment approaches, such as injection or a permeable reactive barrier (PRB). Although colloidal activated carbon can be injected (one full-scale application has shown this approach to be successful), this material also cannot be utilized in a PRB configuration or in sediment remediation.
AquaBlok also offers AquaGate+PAC (powdered activated carbon) as an option to either perform pretreatment or improve the removal of PFAS from water. Other materials such as modified clays also are being developed that may provide an additional AquaGate+ delivery option in the future.
For additional literature on PFAS and AquaGate+RemBind, please visit the PFAS Section on our Downloads Page.
