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.
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.
PFAS Remediation Options
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. 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. However, more recent remediation efforts have focused on limited soil, sediment, and in-situ groundwater remediation.
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
In-Situ vs. Ex-Situ 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. However, most of these remediation approaches have not yet been performed for in-situ PFAS remediation.
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.
ITRC has compiled tables to summarize technologies, most of which have only been tested in limited applications or in laboratory bench tests. 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.
RemBind® For Remediation of Soils Contaminated with PFAS
RemBind, manufactured by Ziltek, is a powdered reagent for the immobilization of PFAS and other organic contaminants. It combines three well-understood materials, including activated carbon, aluminum hydroxide (amorphous), and other binding mechanisms.
A soil mixing approach can be utilized to immobilize contaminants in-situ. RemBind prevents leaching of contaminants from soil. Soils can then be left on-site or removed and shipped to an approved landfill or other facility. Soil mixing using RemBind is a low-cost, proven soil remediation solution that has been used at full-scale.
Since 2008, Ziltek has provided the environmental remediation market with a range of innovative products for detecting and treating organic soil contaminants, such as PFAS. Ziltek is headquartered in Adelaide, South Australia, but has delivered materials to projects worldwide, including remote locations, like Nigeria, China, Indonesia, Qatar and the Arctic Circle. Together with Ziltek, AquaBlok, Ltd. has developed and now markets RemBind and AquaGate+RemBind (described below), a composite product that is used to treat PFAS in groundwater through permeable reactive barriers (PRBs).
The AquaGate+RemBind Approach
Over the last ten years, the AquaGate®+ approach has been demonstrated to be effective on a wide range of contamination in both groundwater and sediments.
AquaGate+ essentially enables the application of a range of treatment or amendment materials in-situ. AquaBlok, Ltd. is now applying their experience and understanding of manufacturing and installation methods to the remediation of PFAS. The AquaGate+ technology is coupled with RemBind adsorptive materials to exploit chemical and physical properties to immobilize and render the targeted contaminants non-bioavailable in the environment.
Benefits Of The AquaGate+RemBind Approach
Contaminants must come into contact with any adsorptive material in order to be removed, so achieving uniform distribution of the amendment or treatment material within a permeable layer is, by far, the most critical aspect of any remedial design.
Contaminants that are transported by water must move through a treatment layer and have contact with the amendment, so any application must provide the ability to maintain and limit reduction in permeability over time.
Amendments or treatment materials must maintain contact with a contaminant for a period of time to allow for adsorption or immobilization. Particle size of the amendment will impact the speed or rate of adsorption. The use of powdered materials provides a more rapid rate of sorption over granular material.
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. An overview of AquaGate+RemBind is provided below.
AquaGate+RemBind in a Permeable Reactive Barrier (PRB) for In-Situ Immobilization of PFAS in Groundwater
AquaGate+RemBind offers a new tool for implementation of in-situ remediation. The AquaGate+ approach to PFAS remediation is intended to provide a viable and proven option to perform in-situ remediation of contamination in groundwater and sediments.
When combined with RemBind, the AquaGate+ approach provides a number of advantages in application of a PRB type in-situ treatment approach. Below is a graphic that provides a conceptual model of how AquaGate+RemBind would be applied in a PRB and the relative advantages of this delivery system for RemBind adsorptive / immobilization materials.
For additional literature on PFAS and AquaGate+RemBind, please visit the PFAS Section on our Downloads Page.