The Navy is ramping up plans to inject a state-of-the-art powdered charcoal product into PFAS-contaminated groundwater at Alameda Point, according to an October 13, 2022, cleanup document posted on the California Department of Toxic Substances Control website. The project will take place at a small area where Navy firefighters trained with PFAS-containing fire suppression foam next to the Oakland Estuary. The goal is to prevent the migration of PFAS into the Oakland Estuary.
Until recently, the only effective method of preventing PFAS chemicals from entering a drinking water aquifer or surface water was pumping the water out through a charcoal filter system and releasing the treated water back underground. This is a costly energy-intensive method that must operate around the clock. And it generates a waste stream of filtered-out PFAS that must be disposed of in a landfill where it could leach out into groundwater in the future.
How new PFAS remediation method works
The newest alternative to the pump-and-filter method is to turn the soil itself into a carbon filter. Here’s how it works. Carbon molecules the size of dust particles are injected into the ground in a special water solution. The microscopic size allows the carbon to coat every particle of soil, such as sand. When the contaminated ground water moves through the carbon-coated soil, the PFAS becomes stuck to the carbon, thereby locking it in place, also known as sequestration.
The carbon molecules in this system are especially effective because of a manufacturing process that turns simple charcoal into so-called activated charcoal, or activated carbon. This “activation” means that the charcoal is subjected to a chemical or steam process that makes the charcoal extremely porous and thereby very effective at trapping contaminants. A typical source material for activated carbon is coconut shells. Activated charcoal is also the filter medium used in water filter packets for coffee makers.
In recent field applications of this in-ground carbon-filter method, it has proven 100 percent effective. The product that the Navy contractor Aptim will use is called PlumeStop®. The proprietary product was developed by Regenesis, maker of environmental remediation products. Regenesis is also known for employing ingredients in other common household products for environmental remediation, such as those found in laundry products used for the cleanup of jet fuel at Alameda Point.
While the in-ground carbon filter concept is elegantly simple, Regenesis had to address two important challenges before implementing the system. First, the carbon molecules had to be ground extremely fine – to the size of red blood cells at 1 to 2 microns – so that they will disburse evenly through openings between soil particles and will coat the soil particles like a blanket. A similar form of charcoal, called granulated activated charcoal, is used for such applications as large-scale municipal water treatment systems, aquariums, and coffee water filters, but the grain size of up to 300 microns makes it unworkable for injecting into soil for contamination treatment.
The second challenge was that simply mixing superfine charcoal dust with water and pumping it into the ground led to clumping of the product. To allow for uniform dispersion and no clumping, Regenesis developed a special biodegradable polymer that the powdered charcoal is mixed with. This proprietary mixture is called a colloid, in which one substance is suspended in another, hence the name colloidal activated carbon. The PlumeStop® is mixed with hydrant water at the treatment site for injection into the ground.
Science fun fact: The process of trapping the PFAS in a carbon matrix is called adsorption, which means it’s locked together like Velcro® and won’t come loose. It sounds like a similar process called absorption, which is what a cleaning sponge will do. But dirt absorbed into a sponge can be rinsed out.
Current PFAS cleanup status at Alameda Point
The current status of the project is that the contractor has taken soil core samples and 10 gallons of groundwater, packed them on ice, and sent them overnight to Aptim’s Treatability Laboratory in Lawrenceville, New Jersey, where they will conduct testing to fine tune the formula for local conditions and to validate the workplan design.
Additionally, the contractor has inserted special bags of activated carbon with tracers, called passive flux meters, into six monitoring wells at the site in order to evaluate water flow and PFAS movement. The bags are custom-made by EnviroFlux. After about three weeks, they will be removed and sent to the EnviroFlux lab where they will be analyzed and the data forwarded to Aptim to incorporate into the workplan design.
The final design is expected to be approved by regulators in August 2023 and work commenced soon after. Aptim’s plan proposes to install a PlumeStop® treatment barrier in a double row along the waterfront of the impacted area.
Once the carbon filter system is in place and is performing as expected, the Navy will most likely utilize this method at other PFAS sites at Alameda Point.
Field applications prove activated charcoal works
The first known in-ground treatment of PFAS using colloidal activated charcoal was completed in 2016 at a manufacturing plant and former firefighter training area in Ontario, Canada. Within three months after the Regenesis PlumeStop® product was injected into the ground, water monitoring around the site perimeter showed PFAS was not detectable. And six years later it is performing as designed, according to the Regenesis website. An independent consultant predicted that PlumeStop® will halt PFAS migration out of the treatment zone for more than 60 years. If the treatment zone were to become saturated with PFAS, it could be refreshed by injecting more of the activated carbon.
Science PFAS fact: “PFAS molecules are made up of a chain of carbon and fluorine atoms linked together. Because the carbon-fluorine bond is one of the strongest ever created, these chemicals do not degrade in the environment. In fact, PFAS products remain in the environment for so long that scientists are unable to estimate an environmental half-life, or the amount of time it takes for 50 percent of the chemical to disappear.” Source: National Institute of Environmental Health Sciences, National Institutes of Health information bulletin, March 2019.
EPA was lax in issuing stringent PFAS regulations
PFAS in groundwater can be present at extremely low levels – in the parts per trillion range. But even at those low levels, prolonged exposure, such as in drinking water, can create serious health and environmental risks. This is because the PFAS class of chemicals are considered “forever chemicals” that don’t break down and cannot be neutralized in the body.
PFAS cleanup at Alameda Point was not dealt with until now because it was not mandated by the U.S. Environmental Protection Agency (EPA) under the Superfund cleanup rules. It wasn’t until October 2021 that the EPA rolled out an action plan to deal with PFAS. Up until the August 2022 proposed rule change, the EPA classified PFAS chemicals only as “pollutants,” but not as “hazardous.” A classification of “hazardous” would have required a remediation plan long ago.
The Department of Defense (DOD) started taking action at military bases to limit PFAS exposure and investigate contamination back in 2016, well before the EPA got serious about PFAS. The DOD timeline of actions is in a presentation on its website. DOD’s initial steps were to limit land-based releases of PFAS-containing firefighting foam, and ordered all military bases that supply their own water to test for PFAS. Eventually all military bases underwent PFAS investigations.
A basewide preliminary assessment of PFAS at Alameda Point was completed in May 2021, which identified 11 contamination sites. The firefighter training area has been singled out for immediate action, with lessons learned to be applied at the other sites.
Ironically, PFAS-containing firefighting foam was first created and patented by the U.S. Navy in 1963, according to the Environmental Working Group. PFAS have been used in hundreds of products, ranging from stain resistant fabric coatings to non-stick skillet coatings.
In a related PFAS story, on Thursday, November 10, 2022, California Attorney General Rob Bonta filed suit in Alameda County Superior Court against 3M, DuPont, and several other companies to recoup the costs for cleaning up PFAS contamination.
“As a result of a decades-long campaign of deception, PFAS are in our waters, our clothing, our houses, and even our bodies,” said Attorney General Bonta. “The damage caused by 3M, DuPont, and other manufacturers of PFAS is nothing short of staggering, and without drastic action, California will be dealing with the harms of these toxic chemicals for generations. Today’s lawsuit is the result of a years-long investigation that found that the manufacturers of PFAS knowingly violated state consumer protection and environmental laws,” Bonta said.
Originally published in the Alameda Post.
More information about PFAS and activated carbon is in this video.
Understanding the In Situ Treatment of PFAS Using PlumeStop Colloidal Activated Carbon
2 thoughts on “Navy to lock down PFAS in groundwater with carbon”
Excellent report Richard. Very informative and hopefully.