PFAS Remedial Methods: Potable Water, Groundwater & Soils.
August 8, 2024
In the world of PFAS.
This is our 4th blog regarding current happenings in the world of PFAS. If you’ve missed the first three: A PFAS Primer, A summary of the PFAS litigation Landscape, and A Summary of Regulatory Standards, they can be accessed at the bottom of this page.
These blogs led us to this latest post: how do you 'fix' the PFAS problem in the real world.
Avoiding contact with PFAS.
There are two primary ways to avoid contact with PFAS:
Remove it from the beginning of the line — namely, during the manufacturing of the consumer products we use every day; or
Remove it from the end of the line, after it has already entered the environment.
Our third blog touched on the removal of PFAS from the manufacturing process (i.e., the beginning of the line) — that is ultimately the only sustainable solution. However, PFAS compounds have been in commercial use for 80+ years, and contamination has reached the far corners of the globe. Therefore, even if PFAS use ended today, which it won't, there will be residual chemicals in the environment for decades to come.
Therefore, we need to find ways to address these 'forever chemicals' that have either already made their way into the environment, and which resist breaking down naturally, due to very strong chemical bonds between the carbon and fluorine atoms that make up the long chains in the numerous types of PFAS. This dilemma has been studied for years by trade groups, non-profits, governmental agencies, and the private sector. The monetary worth of discovering a pragmatic, economically viable solution to breaking down PFAS is incalculable — given the breadth of the problem, a marketable solution is considered a holy grail in the environmental field.
That being said, let's explore where various PFAS remedial solutions currently stand.
Media to be treated.
The best method of addressing PFAS depends upon the media being treated; in this blog we will focus on three media: Potable Water, Groundwater and Soil. Each is discussed in greater detail below.
1. Potable Water.
Potable water simply means 'drinking' water. The source of this water is derived from either a public/community water supply (which can source from groundwater or a surface water/reservoir body) or a private well on your property (which is usually from a groundwater source, but, on rarer occasions, can also derive from a private surface water source).
The methods of treating a public/community water supply are similar to a private well treatment system, but, as you can imagine, given the size of public water supplies, the treatment systems are much larger and usually are more complicated to operate/monitor. Most of the large litigation settlements with 3M, DuPont and others to date have focused on supplying potable water treatment systems to the public to remove PFAS levels, since this is the most immediate and consequential method for PFAS to enter your body. It is really the tip of the litigation iceberg, but an important tip, hence the lion's share of the initial litigation dollars have chased designing, installing, and operating these systems for public water supply utility concerns.
The method of removing PFAS from the water supply falls into two broad categories:
Removing the PFAS from the water by physically transferring the toxic molecules from the water to another medium —such as charcoal. This method does not 'solve' the problem, per se — it simply transfers it from one location to another, kind of like scraping off gum that is stuck to your shoe — it hasn't 'gone away', it is now simply stuck to something else; or
Removing the PFAS from the water by chemically changing the makeup of the PFAS molecules from something toxic, to something non-toxic.
The first method is easier, but isn't a viable long-term solution. The second method is preferable, since the PFAS are destroyed — but the process is much harder, especially since those carbon-fluorine atom bonds are so strong and hard to break.
The most common physical and chemical methods are presented below.
Physical Remediation of Water.
Granular Activated Carbon (GAC)
The most common and proven technology to remove PFAS from water is by using GAC, which is exactly what the name says, small granules/pieces of carbon. When PFAS-contaminated water is passed over/through a column or bed of GAC, the PFAS (and other impurities in the water) will adsorb (i.e., 'stick') to the surfaces of the GAC and the water will pass along, 'stripped' of the PFAS. The actual granular material can be bituminous coal (the most common), lignite coal, wood, or even ground-up coconut shells. The GAC will keep working until the granules are literally saturated with PFAS, in which case there are no more 'surfaces' available to stick to, and the PFAS will simply pass through. This process is called 'breakthrough'.
Usually, the GAC is set in a cylinder, and several cylinders are placed in a series/row (usually a minimum of three, but there can be more on larger-scale systems), with water flowing through one, then onto the next, then onto the next; contact time of the water to the GAC typically ranges from 10 to 20 minutes. Sampling between the cylinders and analyzing the results at a laboratory can tell when the first cylinder is 'full' or has reached breakthrough (usually defined as being half the concentration of the incoming, untreated water), in which case the cylinders are shuffled, with the first one being discarded (being 'spent/full of PFAS') and the middle and last ones moving up in the line, with a new clean GAC cylinder placed at the end. Depending on the gallons of flow-through water, these GAC cylinders can be replaced as often as monthly/quarterly — but for lower PFAS concentrations, or lower gallonage systems, the switchout can be delayed as long as 1 to 2 years. If other types of contaminants are also fouling the water, the GAC will get 'clogged' sooner, and switchout will have to occur more frequently.
This constant rotation of the GAC cylinders continues forever, as long as there is still PFAS in the 'raw' water coming into that first cylinder. These GAC systems are designed to run for decades, which results in the extremely large dollar amounts it takes to run these systems, because you have to build in decades of future GAC system operations and maintenance (O&M) costs. By way of example, in Penn's Grove, New Jersey, the annual O&M costs for a PFOA-removal system for a community water supply serving 10,900 customers (which is a generally smaller-sized system) is $80,000, not including the initial GAC system design, pilot/bench scale testing (this determines the sizing and number of GAC units needed to treat the incoming contaminated water) and installation of $12.2 million. The system treats 3 million gallons of water a day.
And remember, this 'remediation' method does not solve the PFAS problem, it simply takes the contaminant out of the water and sticks it to the GAC. You still have to do something with the 'gum' stuck to the GAC cylinder. That can either be put in a landfill (which really just throws it back into the environment) or incinerated, which will destroy some of the PFAS, but a portion is vaporized and enters the atmosphere (which now becomes an air pollutant that we may breathe in), or the PFAS may settle as dust (which exposes us all over again in another way). This is the 'gum on the shoe' solution, which isn't really a viable long-term solution at all. But in the short-term, it does remove the PFAS from the water supply. So it creates a long-term PFAS problem by solving a short-term PFAS exposure issue.
Some GAC can be reused (it is called 'rechargeable') after it is heated up and the contaminants 'burned off'; but again, this process still transfers a portion of the PFAS to the air.
GAC systems have been used for decades, and are the go-to source for large public water supply systems; there have been numerous scientific studies on using GAC for removing water impurities (PFAS and a whole host of other contaminants) — so the process is well-known and trusted. A properly designed GAC system will remove over 90% of the PFAS, which is usually enough to meet drinking water standards (depending upon the influent PFAS concentrations).
Reverse Osmosis (RO)
RO is also a proven, effective water treatment technique (for PFAS and many other types of contaminants — it is also the primary desalination technique used to convert salt water to fresh water) — but again, it simply is a contaminant transfer mechanism.
Essentially the contaminated water passes through a treated membrane of some sort (think of passing through a screen/filter, usually spiral-wound, in a tube-shape), with the contaminants remaining in the 'screen' and the 'stripped' water passing through. RO can be used alone, but is commonly used in conjunction with other treatment methods, like GAC, in a 'train' format. This is commonly used on residential/household single-user systems (in the United States, and around the world) since it is easy to install/operate and is reliable; the typical cost is about a quarter-cent per gallon.
Membrane fouling (especially by compounds in the water stream that are not PFAS) is a real concern with RO, since it will quickly reduce the treatment capacity of the membrane, so water pretreatment is typically required. If fouling can be avoided, this method consistently removes greater than 90% of PFAS.
The filters are usually single use, and then landfilled or incinerated, with the same inherent limitations of the GAC systems described above.
Resin Filters/Ion Exchange (IE)
The positively charged resin filters are usually single-use and then landfilled or incinerated once the resin is spent, with the same inherent limitations of the GAC and RO systems described above. The 'resin' consists of small, plastic porous beads, with a fixed 'charge'. IE systems have been used since the 1930s for all sorts of water treatment; they are simple to use and effective on a wide variety of compounds (the water filter contact time is usually less than 5 minutes). For PFAS remediation, the IE efficiency is more of a mixed bag; the efficiency is greater than 90% for PFOS removal but is highly variable for PFOA removal (as much as 90%, or as low as 10%), and upwards of 67% for PFNA removal.
These systems are used on many single-point residential water supplies; popular brands include Clearly Filtered, Epic Water, ZeroWater, and Travel Berkey, among others.
Chemical Remediation of Water.
Although the most common methods of PFAS removal from water are physical in nature (namely contaminant transfer from the water to some other medium), that is a 'kick of the can' approach, as noted above. The preferable, and long-term, viable solution is to break down the chemical bonds of the PFAS molecule, rendering the compound inert and harmless. But that task is easier said than done.
The remedial industry has been searching for years for an economic, scalable method to chemically destruct/neutralize PFAS — this is the holy grail.
There are a few innovative chemical methods that have shown promise during bench-scale/pilot-scale testing; they are listed below. None of these has reportedly been successfully implemented in full-scale, commercial use, as of yet.
Supercritical Water Oxidation (SCWO)
SCWO, also known as hydrothermal oxidation, is a destructive chemical technology that has shown some early promise; it has been developed by an Ohio non-profit research firm Battelle Memorial Institute (BMO). SCWO is not a new technology per se (it has been around for decades), but its use in PFAS remediation is a new application, mostly being subject to pilot and bench scale studies at this juncture.
Essentially, this method, in a high temperature (374 to 575+ degrees) and pressure (3,200 pounds per square inch [psi]) environment, has the ability to break the carbon atoms at the end of a long chain PFAS molecule, weakening and disassembling the chains, with inert salts and fluoride as the by-product. Contact times can be as little as a minute to achieve destruction. A private firm, Revive, has reportedly licensed this BMO technology and is looking to scale it to commercial applications. Temperature, pressure and liquid contact times are the variables that need to be optimized for practical PFAS destruction, and the balancing act can be quite complex.
DiMethyl Sulfoxide (DMSO) Method
Other even more promising methods are currently in the bench scale/pilot study stage. In one instance, the PFAS-contaminated water is brought to a low boil (i.e., 175 to 225 degrees) and mixed with an inexpensive solvent (such as DMSO) or a caustic soda, such as common lye (i.e., sodium hydroxide). The contact time using this method is much longer than the SCWO method described above (i.e., from a few hours to a few days), but the solvent/soda essentially 'pops off' the carbon at the end of the long molecule chains and the PFAS 'chain' falls apart. If this method can be replicated on a commercial scale, it could materially alter the PFAS destructive remediation playing field.
2. Groundwater:
Treating groundwater contaminated with PFAS is a different process than treating point of entry treatment (POET) systems for potable water users, as described above.
Groundwater cleanup for PFAS usually involves addressing a large aquifer, which contains hundreds of thousands of gallons of water underground, that many times is not used for drinking water purposes, but needs to be remediated all the same, under a variety of Federal and State-specific statutes. That is because the groundwater is a natural resource of the State and, even if the groundwater is not being used for potable purposes presently, it may be used in the future, and, therefore, must be remediated. The aquifer may also feed surface water bodies (wetlands, creeks, streams, and the like) and affect both flora and fauna that use those surface ecosystems.
The most common methods of addressing groundwater are as follows.
Delineation and Long-Term Monitoring.
By far the most oft-used method of 'addressing' PFAS contamination in groundwater is to quantify the three-dimensional size of the contaminant plume (i.e., delineate the horizontal and vertical limits — this is done by installing and sampling a series of monitoring wells), and, once you have determined the physical location and size of the PFAS plume, you simply 'monitor', or watch, it, to ensure it doesn't impact any water supply wells or 'sensitive receptors', such as surface water bodies, wetlands or the like.
It is not a very proactive remedial measure; in fact, it is not remedial at all. It simply 'parks' the PFAS contamination and watches it, to ensure it doesn't move in such a way that someone, or something, gets impacted. It is a watch-and-wait solution. Not surprisingly, it is also the least expensive and most often used method to address a large PFAS plume in groundwater. But that doesn't mean that once you delineate it you can simply 'walk away with no further action required' and the future cost is zero; far from it. Even in such a wait-and-watch monitoring program, there is a continuous, future cost of sampling (many times for a period of years), forever analyzing and assessing monitoring wells to ensure the plume is not harming anyone or anything, since groundwater flows, just like a stream, but usually very slow (i.e., on the order of inches or feet per year — but sometimes much faster). This monitoring process may include sampling nearby, downstream potable wells and environmental features (such as surface water bodies). Even so, it is likely the least intrusive, and least costly attempt to address PFAS in an aquifer. Ultimately, this PFAS groundwater plume may be cleaned up in the future, if an economic method of the same is discovered, or if the plume moves and threatens a drinking water supply (i.e., a well or surface water body) or some sensitive ecological receptor (e.g., a wetland, a surface water body, threatened/endangered habitat, or the like). More on that below.
Plume Containment/Cut-Off.
Under the scenario described above, sometimes the plume that has been delineated cannot be simply left alone, because it might move/flow and ultimately impact potable wells or some other sensitive environmental receptor downstream (like a surface water body, wetlands, or the like). In those situations, you would need to put an underground 'barricade' between the plume and whatever it is that needs to be protected.
Those barricades are usually physical of some sort and can take one or more of the following forms.
Interlocking Sheet-Piling
These are narrow (up to a foot wide, typically) sheets that are driven into the ground to act as a 'fence'. Sometimes these sheet-pile walls can extend 50 or feet below grade, constructed of steel or even heavy-duty plastics. As can be imagined, the longer the sheets/the deeper the wall, the more expensive the cost to install. This process tends to be very expensive, with extensive permitting, engineering design, and ongoing monitoring via sampling compliance wells on both sides of the wall periodically, to ensure the 'wall' is working and PFAS contamination is not slipping through.
Slurry Wall
Similar to the sheet-pile wall, except that the wall is essentially a deep trench filled with an impermeable material (e.g., grout, flowable clay, concrete, or the like) that serves the same purpose as sheet-piling.
GAC or Powdered Activated Carbon (PAC)
Usually, PAC (a powdered carbon), which is a much finer ground powder than GAC, is used in conjunction with sheet-piling or slurry walls, by injecting PAC directly into the groundwater either via wells, injection points or injection trenches. This PAC injection process typically occurs directly in front of a slurry wall or a sheet-pile wall, to adsorb PFAS prior to it coming up against the barrier. In other situations, the PFAS plume is surrounded by injection wells (like a corral) that receive PAC or GAC treatments on a periodic basis as a solo-control mechanism. PAC has a much higher adsorption rate than GAC, along with a >90% PFAS reduction factor — both positives; however, the downside is that you usually need fairly high concentrations of PAC, which will likely increase the number of applications and the associated carbon purchase and delivery costs.
Pump & Treat Systems
When groundwater containment is simply not sufficient, and a more proactive method of aquifer treatment is required, a groundwater pump and treatment (P&T) system is always an available option. However, this time-tested, proven technique is usually avoided/used as a later resort, simply due to the tremendous cost of designing, permitting, installing, and operating a long-term P&T system.
The typical P&T design includes a series of wells to both extract PFAS-impacted groundwater and to monitor the plume, to ensure the extraction process and associated drawdown are preventing the PFAS-contaminated groundwater from impacting nearby potable wells, ecological receptors, or both. The extracted PFAS-contaminated water is then treated, typically using the same methods for the potable water above (e.g., GAC, reverse osmosis, resin filters, or the like), with the treated water discharged back into the aquifer, to a surface water body, or to the sanitary sewer system (depending on volumes and the proximity of discharge locations).
Deep Well Reinjection
A potential PFAS solution being discussed in the remedial arena is called deep well reinjection, whereby PFAS-contaminated water (either untreated, or mildly treated) is subsequently injected into very deep wells (designated by the EPA as Class 1 wells), set much deeper than any potable well sources (either at the subject site, or trucked to a third-party commercial injection site). This is a novel and expensive approach (drilling and constructing such deep wells is costly, as is the permitting and monitoring process), and primarily in the conceptual stage at this juncture. And, of course, this is not a destruction method, but rather simply a media transfer method — it does not destroy the PFAS — it simply 'buries' it, by discharging it deep underground.
Biodegradation
Biodegradation techniques have been successfully used in the environmental remedial field for a variety of contaminants — but not PFAS. The moniker 'forever chemicals' has been branded to PFAS largely because the chemical molecular bonds are hard to break in nature. To that end, the idea of PFAS being remediated via biodegradation seems antithetical. And to date, research has shown that presumption to be true.
However, given the potential to profit from viable, environmentally friendly PFAS destruction techniques, there are still various groups looking at biodegradation options, both microbial and fungal-based. Limited pilot and bench scale studies to date have had conflicting results; to that end, this arena appears to be still very much in the developmental stage.
3. Soils
PFAS can also find its way into soils above the water table, via air dispersion, chemical discharges to the ground surface or through effluent flowing into septic systems, dry wells or seepage pits. PFAS in soils can act as a continuing ‘source’ of PFAS groundwater contamination, so you may want to remove them, as some states have PFAS clean-up standards for soils as well as water.
To that end, there are several methods to address PFAS in soils, detailed below.
Capping
Similar to the groundwater delineation/monitoring method, soil capping is usually the least expensive and quickest method to address PFAS in soils. Essentially, the capping process simply puts an impervious cover over the affected soils area, and leaves the contamination in place — effectively 'putting a lid on it'. Usually, such methods require mapping of the impacted area, with restrictions (sometimes recorded with the deed at the local county clerk’s office) on 'disturbing' this soil in the future.
It is not a destructive technique, it simply is a way to monitor the contamination, ensure it isn’t disturbed in the future and is not able to be directly touched by humans. This is not necessarily an inexpensive technique, depending on the size of the impacted area and the cost of installing the impervious cap (e.g., asphalt, concrete, geomembrane material, or the like), but it is usually the first remedial method considered on any given project.
Excavation & Disposal
This tried and true method pretty much everyone is familiar with - dig up the PFAS-impacted soil and get rid of it. The process requires collecting soil samples after the excavation work is complete, to ensure all the PFAS has been removed, and backfilling the excavation with clean soil, and trucking the soil offsite... somewhere else.
Again, for smaller areas, or for a total 'site' solution, excavation makes sense. But this process doesn't destroy the PFAS, it simply moves it from Site A to Site B. Hopefully Site B is a secure location (such as a landfill), whereby the soil is subject to proper, long-term monitoring. If the soil is incinerated, then the PFAS may be removed from the soil, and partially destroyed, but a portion will be transferred to the air, to be discharged into the atmosphere (or captured in air filters, to again, be landfilled, or incinerated at some future date).
The whole process is a bit 'sticky', with PFAS fully or partially sticking around, just in different shapes and forms.
Solidification
Again, this process is not a destruction technique, but rather a PFAS stabilization technique.
Namely, the contaminated soil is rendered inert (or largely inert) via solidification (i.e., turned into concrete blocks, for example), with the PFAS trapped in the end-product, which will eliminate, or largely abate, any leaching. But the blocks need to be stored somewhere and monitored to ensure the PFAS does not leach out over time (or proven initially that the PFAS is unlikely to leach). This process usually requires pilot or bench-scale testing of trial blocks, and several levels of regulatory permitting/approval; however, in certain situations, the process may be the most cost-effective option to employ.
Soil Washing
This is an ex-situ process, usually employed at the contaminated site, whereby soils are excavated and temporarily stockpiled on the property, subject to 'washing' with an aqueous agent of water and chemical desorption compounds (i.e., a mixture of surfactants and extraction solvents).
The soil washing process is simply to reduce the volume of contaminated soil. It works by disengaging the PFAS from the larger-grained soils (i.e., sands and gravels) and leaves them attached to the finer-grained soils (i.e., silts and clays), where the PFAS has a greater affinity to attach. This is essentially a contaminated soil reduction process, whereby the 'cleaned' sands and gravels can be reused, and the PFAS-contaminated silts and clays remain, to be dealt with in some other manner (but at a lower soil volume). And the resulting liquid produced by the 'washing' process, which now contains PFAS residuals, must be treated by one of the aforementioned aqueous methods.
Blending
There is an old saying in the environmental field (especially in New Jersey) that dilution is not the solution to pollution, meaning that the NJDEP (and other regulatory agencies, federal and state) tend to not look kindly on 'fixing' a contamination issue by simply taking dirty soil and mixing it with clean material until the resulting 'mixture' is below regulatory standards. This usually frowned-upon process is called 'blending'.
However, even in skeptical states, like New Jersey, such blending is permitted in certain situations (e.g., many times the NJDEP will allow pesticide and herbicide-contaminated shallow farm soils to be tilled/mixed with deeper soils to 'blend' the contamination away).
To that end, when confronted with a PFAS contamination matter in soils, and other solutions are elusive, blending may be an alternative to pursue. Again, this is not a destruction technique, but rather simply a 'dilution' technique — the PFAS still exist.
Incineration
Incineration is commonly used for potable water PFAS collection products; namely, the spent GAC and resin canisters, cylinders, and membranes that collect PFAS via mechanical means.
As previously noted above, PFAS-contaminated soils/sediments may also be incinerated as an ultimate destruction technique. However, burning is not 100% efficient and there will be residual PFAS air discharges, which is simply another way of redistributing and redirecting the PFAS from one medium to another.
That being said, there are certain parties (some of whom are PFAS responsible parties) that have opined that incineration destruction rates of greater than 99% are achievable for certain PFAS, but it does not appear this conclusion is shared across the industry, and the results seem to be compound-specific and have not been employed on a wide scale basis. To that end, the long-term viability of this technique appears to be in flux.
Adding to the complication of incineration is that a variety of States are moving to ban the procedure output, for the simple reason that they do not want new PFAS air issues to further complicate existing PFAS water or soil issues. Filters placed on the incinerator air exhausts simply capture the PFAS particles back into a collection medium. It is clear to see the merry-go-round nature of physical capture — it simply transfers PFAS from one phase to another, which is why chemical destruction of the carbon-fluorine molecule into harmless by-products is the true remedial goal in the long term.
A look at some of our past FPAS articles.
We penned other articles on this emerging group of contaminants, per- and polyfluoroalkyl substances, better known by the umbrella name PFAS. You can access them below:
PFAS Regulatory Standards: Water, Soils, Consumer Products, June 2024
PFAS Litigation: Where it’s Gone & Where it’s Going, May 2024
A PFAS Update: The Forever Chemicals, April 2024
PFAS Update: Now Coming to Your Tap, July 2020
New Bane of the Real Estate World: PFAS, April 2020
As the litigation, regulatory, and treatment arenas mature, we will revisit the PFAS issues — stay tuned.
As always, feel free to contact us if you have any questions about the information presented herein.
Please note, the information provided in this newsletter relating to PFAS and associated compounds is strictly for informational purposes only and should not be construed as recommendations or advice on how to treat, remediate or handle PFAS in any manner; our firm assumes no liability of any kind regarding same.