Treatment of PFAS
PFOA and PFOS are the two most commonly encountered examples of Per- and Polyfluoroalkyl Substances (PFAS). PFOA and PFOS are abbreviations for the chemicals “perfluorooctanoic acid” (PFOA) and “perfluorooctanesulfonic acid” (PFOS). While US government regulations have been passed to eliminate the use of these contaminants in manufacturing and other business practices due to the health risks they pose, these compounds are recalcitrant – or in layperson’s terms, not readily degradable – and as a result are ubiquitous in the environment.
PFOA and PFOS are the two most commonly encountered examples of Per- and Polyfluoroalkyl Substances (PFAS). PFOA and PFOS are abbreviations for the chemicals “perfluorooctanoic acid” (PFOA) and “perfluorooctanesulfonic acid” (PFOS).
Historically, PFAS compounds were used in various industrial activities and were components in many industrial and consumer products because they exhibit many useful properties. As the United States EPA has indicated in their research findings, they are resistant to heat, water, and oil, and also resist degradation in the environment. You may be familiar with technologies such as Teflon, Goretex, and firefighting foams, which have PFAS compounds incorporated. From clothing to cooking – many have used products containing PFAS in their day-to-day activities.
These chemicals are of concern because they have now been detected in groundwater, drinking water, and soils in many of our local communities. This creates a potential exposure pathway to humans and possible health risks.
PFAS Groundwater Remediation Strategies
With PlumeStop, remediation professionals gain a solution that will provide an effective, more economical means of stopping the migration of PFAS plumes, thereby protecting sensitive receptors. There are many possible strategies for the in situ containment of PFAS using PlumeStop. Here are some examples:
Strategy #1: Simple Plume Cut-Off Barrier
In this application, a single barrier of PlumeStop can be applied to limit plume expansion. The purpose of the application is to protect a property boundary from a plume entering or exiting a site. It can also protect receptors such as a well or water body and minimize the plume in order to contain liability.
Strategy #2: Sequence of Barriers
PlumeStop can also be injected as a sequence of multiple barriers designed to progressively eliminate the PFAS plume. The benefits of this approach are that it addresses the entire plume and is particularly suited for large plumes and built up areas with restricted access.
Strategy #3: Localized Receptor Protection
Because PFAS plumes tend to be extremely large and dilute, remediation professionals will likely need to turn to interim measures like this one to protect local receptors. Acting like a “Brita®” filter in the ground, the PlumeStop can be injected around extraction wells to protect them in the event that an entire plume cannot be quickly contained.
Potential Health Effects of PFAS
Studies have indicated that PFAS poses potential threats to human health. According to the Agency for Toxic Substances and Disease Registry (ATSDR), a division of the Center for Disease Control (CDC), PFAS can have negative effects on fetal and child development, adult hormones and fertility, high cholesterol, in addition to posing other health risks.
As a result, the US EPA has now started requiring the monitoring of drinking water and set lifetime drinking water advisory levels at 70 parts per trillion (ppt) for PFOA and PFOS. The EPA has also indicated that they will set screening levels and site-specific cleanup levels at Superfund sites, which will be used to determine if long-term groundwater remediation or soil remediation is needed.
Groundwater Treatment of PFAS
To date, the use of traditional means of groundwater remediation of PFAS plumes has proven difficult. Because they are extremely robust compounds, remediation technologies such as in situ chemical oxidation (ISCO) and various forms of bioremediation have been unable to address these contaminants. The most prevalent method at this time is to use an ex situ pump and treat system with activated carbon filters. However, this process can prove very expensive and challenging due to the extremely wide-area, dilute formation of the most common PFAS plumes.
REGENESIS has developed an in situ remediation product called PlumeStop® Liquid Activated Carbon™ that has the potential to solve the challenges faced in the groundwater remediation of PFAS. This technology can be applied under low-pressure injection, which solves the problem of excessive costs incurred with pump and treat systems. Through the use of a proprietary organic polymer dispersion chemistry, the activated carbon achieves high distribution through the subsurface and removes contaminants like PFAS rapidly from groundwater.
Research Article: Breakthrough Treatment for PFAS
This article published in Wiley’s Remediation Journal reviews a site impacted with petroleum hydrocarbons, perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and other perfluoroalkyl sulfonates (PFAS). A single application of PlumeStop resulted in a significant reduction of contaminant concentrations to below standards for 18+ months since the injection. Modeling indicates that the PlumeStop application event should keep the PFAS contained within the source area for upwards of 100 years. Details of the remedial design approach are provided along with results of its implementation.
Evaluating the Longevity of a PFAS In Situ Colloidal Activated Carbon Remedy
This article published in Wiley’s Remediation Journal uses various visualization and modeling methods to evaluate the in-situ remediation of PFAS via colloidal activated carbon (CAC) at a site in Central Canada. A three-dimensional reactive transport model (ISR-MT3DMS) was used to indicate that the CAC remedy implemented at the site is likely to be effective for PFOS remediation for decades. The research article concludes that due to the relatively low cost to implement the CAC, and the ability to adapt the remedy in the future, this remediation approach may be viable at other PFAS sites.
Pilot Test Conducted to Remove PFAS Risk
This case study reviews a pilot test to remove PFAS risk via an in situ colloidal activated carbon barrier at Camp Grayling in Michigan, US – a large year-round military training center operated by the Michigan National Guard (MIARNG). Colloidal activated carbon was selected because of the expected rapid reductions of PFAS by removal from the dissolved mobile phase, as well as its expected lower total project costs when compared to operating a mechanical system over a similar time. The MIARNG decided to conduct a PlumeStop pilot test to determine if this treatment would meet their site goals prior to a possible full-scale application. The goals for this pilot project were to utilise an approach that could both protect the Grayling community from exposure and cost-effectively expand to a full-scale application.
In Situ Remedy Addresses PFAS Risk at Superfund Site
This case study reviews remedial programs undertaken at the Solvents Recovery Service of New England (SRSNE), US, where soil and groundwater were contaminated with VOCs and PFAS contaminants. In 2018, an innovative remedial approach incorporated natural attenuation with the use of PlumeStop® to work with an existing sheet pile structure to limit the mobility of the plume and effectively treat contaminant concentrations. PlumeStop quickly reduced PFOS/PFOA levels and in combination with AquaZVI® eliminated VOC contaminant concentrations. It is estimated that the PRP group involved will save $400,000 annually with the shut down of the pump and treat system on site.
Webinar Series on PFAS– Assessment, Treatment Options & Lessons Learned
REGENESIS has been working with several consultancies, problem holders and universities around the world on the challenges that PFAS poses in the environment. Together, we have completed a number of successful laboratory, pilot and full-scale applications.
In our PFAS webinar series, guest speakers explain more about these challenging contaminants, including lessons learned during site investigation, in situ remediation and modelling tools for treatment evaluation.
Additional PFAS Resources:
Interested in learning more about PlumeStop and PFAS?