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Learn the Following in This Free Webinar:

  • In situ remediation with colloidal activated carbon eliminates risk of PFAS at a low cost
  • Colloidal carbon isotherm data and sorption test data for PFAS indicate excellent sorption capability and increased performance with decreasing carbon particle size
  • A single application of colloidal activated carbon at an actual field case site resulted in orders of magnitude reduction in PFAS groundwater concentrations to below USEPA health advisory levels

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  • If you need assistance with a current project and would like to get a design and cost, please visit our Request a Design page.
  • To get in contact with a REGENESIS Technical Solutions Manager use our Contact Us form.

Video Transcription

Dane: Hello and welcome everyone. My name is Dane Menke. I am the digital marketing manager here at REGENESIS and Land Science. Before we get started, I have just a few administrative items to cover. Since we’re trying to limit our time to an hour, today’s presentation will be conducted with the audience audio settings on mute. This will minimize unwanted background noise from the large number of participants joining us today. If you have a question, we encourage you to ask it using the question feature located on the webinar panel. We’ll collect your questions and do our best to answer them at the end of the presentation. If we do not address your question, we’ll make an effort to follow up with you after the webinar. We are recording this webinar and a link to the recording will be emailed to you once it is available. In order to continue to sponsor events that are of value and worthy of your time, we will be sending out a brief survey following the webinar to get your feedback.

Today’s presentation will focus on eliminating risk from PFAS contamination via low cost, In-Situ remediation with colloidal activated carbon. With that, I’d like to introduce our presenter for today. We are pleased to have with us Scott Wilson, President, and CEO of REGENESIS. Scott has extensive experience in the development and application of advanced technologies for groundwater and soil restoration. He’s a widely published expert with over 30 years’ experience designing, installing, and operating a broad range of remediation technologies. He has expertise in project management and has directed the successful completion of large industrial remediation programs under state and federal regulatory frameworks. At REGENESIS, on specific projects, he plays an active role in technical oversight and program management to ensure conformance with customer expectations. All right, that concludes our introduction. So, now I will hand things over to Scott to get us started.

Scott: Well thanks very much, Dane. I really appreciate it. And thanks to everybody for joining us here. What I’d really like to go over and impart today in this one-hour time slot is an introduction to colloidal activated carbon and an introduction to environmental risk, and then a focus on the use of colloidal activated carbon to eliminate that environmental risk. This is actually a sort of an extended version of a talk that was given just last week at the National Groundwater Association workshop which was an actual meeting of sort of top regulators and consultants to focus on solutions to the PFAS problem that we’re seeing around the world. So, I hope to get through this and leave a little bit of time for questions. And with that, we’ll move right into it. I want to acknowledge Jeremy Birnstingl and Kristen Thoreson who were both instrumental in the development of colloidal activated carbon technology and who actually did a lot of the experimentation and development of what we’ll talk about today.

So, first off, what is colloidal activated carbon? Well, first of all, it’s not your grandfather’s activated carbon. It’s actually what we take is we take granular activated carbon, which you’re used to seeing in carbon canisters on pump and treat systems, and we actually mill it down to the one to two microns. And most colloidal or most granular activated carbon is 1,000 microns in size. There is some that’s only half that, it’s 500 microns. We take it and we mill it down to one to two micrometers. And that’s two to three orders of magnitude smaller than granular activated carbon. It’s actually milled down to the size of a red blood cell and we then suspend it in water. And first of all, carbon itself has a huge surface area, but when you take granular activated carbon and mill it to the size of a red blood cell, what you’ve done is you’ve been imparted a huge amount of wedded surface area to the outside. In other words, if you have a lot more surface exposed directly to the contaminant in the aqueous medium. As a result, you get extremely fast sorption.

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So, how do we do this? And if you just had activated carbon milled to the size of a red blood cell, it would re-agglomerate into bigger chunks. So what we’ve done is we’ve figured out additives that we can add that allow for the suspension of these particles without clumping. And really what we do is we wrap the particles in a polymer that has negative charges all over the polymer. And so the net charge of the particle is negative. And as a result, all these negatively charged particles are bouncing around in suspension repelling each other, so it actually stays in suspension. It looks like fountain pen ink. If you’re familiar with fountain pen ink, it looks just like black water. And the result is it just flows into the aquifer. You can actually just pour it down, monitor it or not monitoring wells. But you can pour it down wells. You can pour it into the subsurface and it will just go in by gravity or you can, under low-pressure, push it into the subsurface.

Most of the subsurface has pore throats that are lower than 10 micrometers in size. In other words, if you’re trying to inject or flow material through sand or silts, most of the pore throats between those particles, which are much smaller than the pores themselves, require that the particle be smaller than five microns to move through there. And that’s why we chose to get down to one to two microns so that it’ll actually flow in the aquifer matrix flux zones. Once it goes down into the aquifer matrix flux zones, the negatively charged particles actually attach onto the surface wherever there’s a positive charge. And realistically, we don’t have time to go into it now, but what we’re actually referring to is the zeta potential of the subsurface. The zeta potential of the aquifer matrix itself where there’s a negatively charged or where there’s a net positive charge rather, the negative charges will adhere. And once these particles adhere that basically coating the subsurface, they don’t move. They attach and over time the polymer will degrade. But we do not see the carbon rereleased. It actually becomes part of the aquifer matrix and stays in place.

The other thing that’s been very interesting is that when we load the colloidal activated carbon into the subsurface, as it coats these pores, you can do multiple coatings and we’ve seen no impedance of groundwater flow. In controlled column studies with sand with a considerable amount of silts and clays, we can continue to flow PlumeStop through, wash it, put colloidal activated carbon, what we call PlumeStop, through, wash it, and see multiple times with no impedance of groundwater. As I mentioned, when we put our additives into the carbon that’s been milled down to the size of a red blood, we have what we call PlumeStop. And PlumeStop is really our brand of colloidal activated carbon with the additives.

And after a project was successfully completed, it was a regulator who’s reviewing the data and he said something that really resonated. And he said, “You’ve converted the polluted aquifer into a purifying filter.” And that’s really what we do. By putting colloidal activated carbon into the flux zones and coating those flux zones, we’ve turned that flux zone into a purifying filter, very much like a Brita filter in fact. It’s both… The aquifer, once it’s treated, serves both as a multimedia filter as well as a carbon filter. So, it’s a very, very unique and disruptive technology within groundwater cleanup.

So, here’s an example. Colloidal activated carbon, our PlumeStop is on the left. And on the right is another product that’s on the market which is a powdered activated carbon product that people are fracking into the subsurface. You’ll see that as you load the carbon on… What we’re doing, by the way, is we’re pouring water through here and this is a 12-minute lapse. This is a 12-minute video here. What you saw was the colloidal activated carbon on the left actually loading on and flowing through the column just with head pressure of water. Again, and this sand has 11% silt and clay, it’s a one-inch column and 12 minutes elapsed time. You saw it float right through.

The powdered activated carbon on the right is too large to move through the pore throats. If this doesn’t work, you have to fracture the subsurface to get it to go into the subsurface and it’s really not applicable. What I wanna also mention here on the left, when you saw that PlumeStop move through it was black as night. And then as you flowed pure water through, clean water, you saw that that black turned to gray and it has not changed. What happened is the PlumeStop moved through leaving a paint or a coating of one to two microns on the sand itself turning the column gray. That will not wash off. We’ve done columns, large 16-foot columns where we’ve washed, I forget, it was something like 90 pore volumes through at high shear, and you cannot remove the carbon. It’s now part of the aquifer matrix itself.

So, this is PlumeStop. And as you see it’s very easy to move through the subsurface, unlike powdered activated carbon. That’s a filter by the way. It’s just not moving through the filter. Sorry about that. But on the left, you see that the colloidal activated carbon does, in fact, move right through the sand and silts with no problem at all.

So, here’s what sand looks like. That sand column before the PlumeStop went through you can see the clean faces there. These actual surfaces are very clean and shiny if you will. Notice the scale at the bottom here. The scale is a 50-micron scale. Now we’re gonna move into 20 microns. And here this is after the PlumeStop moved through, you can see that you have all of this coating of carbon now on the sand. The sand has now been turned into a purifying filter. We’re gonna move in to a 10-micron scanning electron micrograph. And here you have… You’ll see these are all one to two-micron particles coating the surface and that’s PlumeStop in place.

So, smaller particles equal much faster sorption. I mentioned earlier that it’s much faster sorption. Well, I just wanna be clear here that intraparticle diffusion is the same. So, regardless… If you have a large carbon particle, once the contaminant is moved inside of that carbon, it doesn’t matter whether it’s a small particle or a big particle. The kinetics are pretty much the same once it’s inside the particle. However, the smaller particles provide more exterior surface and shorter distance to all the sorption sites. So, by having more of the outer surface facing the challenge concentration of contaminant in solution, there’s more opportunity for it to move into the particle. And because it’s a smaller particle, all of the sorption sites within that particle can sorb contaminant in a much shorter period of time than waiting for the contaminant to move into the center of a large particle.

This is actually some data generated by Xiao. The paper is actually Xiao, Ulrich, Chen, and Higgins. This is out of researcher Chris Higgins’s laboratory at Colorado School of Mines. It was actually published in ESNT, and what’s important here is that they took greater than 500-micrometer particle, that’s the light pink line. And they took that and they milled it. And they milled it into one, two, three different…the four difference other cohorts of size particle. And they took these different sized particles, and they put them in separate beakers, and they then added the same challenge concentration of PFOS to them in solution. And over time they measured what the concentration of PFOS was in the aqueous solution in contact with this carbon. And you’ll see here on the bottom, the X-axis is time and on the left is the concentration at the time of measurement over the initial concentration. It’s the log.

What you see is the large particle which is the pink line over time sorbed very little contaminant out of the aqueous solution. You still see a lot in solution over time. This is 30 days. It’s still has a lot of contaminant solution. The smaller particles though as they get continually smaller, they sorbed much, much more the contaminant out of solution. What you see is the 53-micrometer particle down here in the red was dramatically more efficient at sorbing the contaminant from the solution. And this is all, by the way, the same amount of carbon just in different sized particles. So the amount of carbon in a smaller particle was much, much more efficient at sorbing contaminants out of the water than the larger particle, even though the same total amount of carbon was used in each case.

In fact, if you look at the red line, this reached equilibrium meaning it was totally sorbed all the contaminant it could sorb out a solution within less than a day. You’ll see the larger particle which is equivalent to the smallest of granular activated carbon available on the market, I think it’s about 500, you’ll see that in 30 days, it didn’t even…it sorbed very little. In order to get to equilibrium in the same point as the red line it would take about 90 days. So the smaller the particle, much, much faster absorption. And just an illustration of why this is one more time. If you had a pound of carbon that was 500 micron particle size, let’s say this particle on the left is one of the particles in that pound of carbon, and you subjected it to PFAS, within a day, the out…you see that little red band of PFAS would have been sorbed onto that carbon.

Let’s say it’s one micrometer, maybe two micrometers into that 500-micrometer particle within a day. Well, if you had taken that same amount of carbon, ground it up into colloidal activated carbon with one to two-micrometer size, within that one day period if you had a distance moved and diffused of one to two microns, you would have accessed all of the absorption sites within one to two-micron particle size. So there’s the power of size. The smaller the size, the faster you reach all the absorption sites. So, it’s much more efficient in terms of the absorption to have a smaller particle than a granular activated type particle.

So, how do we apply PlumeStop or colloidal activated carbon to treat sites? How do we utilize this material? Well, if you have a project site and the red represents the flux zones, the contaminant moving in the flux zones, by a flux zone, I mean a zone of higher permeability relative to the surrounding strata. So, up here it would be a clay or a silt zone, in the middle it would be a clay or silt zone, but here are sandy silt zones that are actually taking most of the contaminant towards this monitoring well. What we do is just go into the subsurface, map the high flux zones, go into the subsurface with either geo-probe or a well, and simply pour or under low pressure inject the black PlumeStop. And it goes and moves through these flux zones, coating the flux zones and prohibiting back diffusion.

And here’s an actual core. And to give you an idea of how this relates, here’s an actual core from the subsurface clearly documenting that we turned the high flux zones black and whereas most of the clay, granted it’s not treated by the PlumeStop, but when the contaminant back diffuses out of that clay into the high flux zones, it will, in fact, be sorbed onto the carbon itself and prohibited from entering the monitoring well.

There was… We actually undertook a study at Colorado State University at Professor Tom Sale’s laboratory. His former graduate student, Dr. Kevin Salar, who’s now with CDN Smith undertook a study for us. We actually paid for an extension of an ESTCP funded study where they went into dual-porosity sand tanks where there was sand and silts inter-bedded and they actually contaminated the strata within the sand tanks with TCE and then flushed it for a period of time to mimic a pump and treat system. And in the actual ESTCP study, they then put in lactate to see if bioremediation would stop the back diffusion, permanganate, CVI, all sorts of different mediation of injectable techniques. None of the techniques did anything more than prohibit the appearance of the back diffusion for a short period of time before rebound overtook the treatment and it went back to where you’d expect the back diffusion to be coming into the flux zone. So, it went back to the typical level of concentration.

When we actually undertook the same study with the same soil, the same people and the same sand tanks with PlumeStop, when the PlumeStop was floated into those flux zones within the dual-porosity sand tanks, it prohibited the back diffusion from exiting the tank. And actually we got biodegradation, in that case, it was coordinated solvents. We got bio-degradation. So, the point here is that colloidal activated carbon, when applied to these flux zones, will actually treat the flux zone and prohibit the impact of back diffusion coming from the immobile porosity in the lower-permeable zones. So, this is the way we apply PlumeStop, treating the flux zones and turning these flux zones into purifying filters.

In terms of performance of colloidal activated carbon, this is an example. Now, this is with chlorinated solvents, but just to give you an example of a typical treatment, within one to two months generally you don’t see any contamination showing up or very low contamination showing up within the flux zones. In your monitoring wells, you just don’t see contamination if you’ve appropriately applied colloidal activated carbon into the subsurface in the area of that well. It’s just simply sorbed and taken out of the dissolved phase and in the case of chlorinated solvents, it’s biodegraded. So in terms of how many projects sites have been applied or where colloidal activity carbon has been applied, over 200 projects around the world have been successfully treated with PlumeStop in Europe as well as in the U.S. and Puerto Rico.

So, with that, that’s the intro to… That’s actually the intro to colloidal activated carbon. Let’s move now to a little bit about fluorinated compounds and then we’ll move into risk. So, perfluorinated compounds. In this case, we have PFOS and PFOA on your screen. The PFOA, of course, is the carboxylic acid and the PFOS represents acid. And here the intersection of these lines are the carbons and you’ll see these are perfluorinated. These are the two largest groups of compounds but they are, by no means, the only compounds, and we’ll get to that in a little bit. But in terms of how PlumeStop and PFOA and PFOS interact, this goes to what are called isotherms.

So, in order to show how it performs, in other words how colloidal activated carbon performs on PFOA and PFOS, it’s the same as with any carbon. You generate what’s known as an isotherm. And an isotherm is a series of measurements where you have a challenge concentration of contaminant and you subject it to an increasing amount of carbon. And you wait for that to come to equilibrium at each point and you measure what the concentration of the contaminant is in the aqueous phase, which is the long here on the X-axis, versus what’s sorbed to the carbon on the Y-axis at equilibrium. And as you have more and more carbon, you’ll see…as you have the higher amount of carbon to contaminant which is down in this area, you have much more efficient removal of the contaminant… Sorry, contaminant from the aqueous phase. As you measure each one of these carbon contaminant loadings, you plot it. And you’ll see that the plot is not a straight line. If it were, I think it’s called a Langmuir isotherm. This is a Freundlich isotherm because it has a bend in it, okay? It has a curve to it. And why they’re called isotherms is that each one of these measurements are taken at the same temperature. And so you generate this curve.

And again, I just wanna stress that you have a much higher efficiency at lower concentrations of challenge contaminant compared to carbon. So, the more carbon you have relative to the contaminant concentration, the more efficiently it removes at equilibrium the contaminant from the aqueous solution. Okay? So, what’s important on this is what’s known as the Freundlich constant. The Freundlich constant is a constant generated in the equation for the curve. And depending on how the isotherm is generated where there’s higher up or lower down, you’ll have a different Kf.

So, for PFOA, it turns out that the Kf is 52. Okay? And for PFOS the Kf is 135. And what this means is if you take a five-part per million concentration of PFOA, you would need 224 milligrams per liter of PlumeStop to take it from five parts per million to 0.005 points parts per million, which is not much PlumeStop required. And you need even less for PFOS. Relatively speaking you need a lot more for chlorinated solvents like PCE, so it’s pretty efficient. PlumeStop is pretty efficient for PFOA and PFAS, but in reality, this isn’t very relevant because these concentrations of PFOA and PFOS are exceptionally high. If you move down to more reasonable challenge concentrations of PFOA and PFOS, you’ll see such as 100 micrograms per liter. You only need 8.4 milligrams per liter of PFOA to take 100 down to 0.1 parts per billion. And even le… And for PFOS should be 9.8. So, it’s very efficient. And again, the lower the starting concentration of your contaminant, the more effective PlumeStop is. And again, these are pretty high. I mean, we’re talking 100 to 0.1 micrograms per liter here.

So, how does this relate to what we’re really trying to do? The question. So, what happens over time? Isn’t your carbon gonna fill up? Won’t the barrier… If you have a barrier or an injected area where PlumeStop has been injected into the subsurface a flux zone that’s filled, for instance, with PlumeStop sorbed onto the aquifer matrix, won’t it fill up over time and breakthrough? The answer is, as PFAS do not degrade, the answer is, yes, it will break through eventually. Remember the chlorinated solvents and petroleum hydrocarbons once they’re sorbed under the PlumeStop will degrade and you won’t see them show back up in the aqueous phase. But with PFAS, eventually, the PlumeStop will fill up. So, the question is, how long will this take?

So, this is all about retardation factors. And a retardation factor is often used in contaminant transport. Whenever we talk about modeling complete and transport of contaminants in the subsurface, we talk about retardation factors. And retardation factors are calculated directly from the Kf, that Freundlich constant. Again, it comes back to the Freundlich isotherm and how much sorption you will have on to the subsurface either fraction of organic carbon or in our case, how much PlumeStop you have there. And there’s an algorithm that’s used to convert Freundlich isotherms into retardation factors. And in this case, it’s equation 16 out of empty 3D which is a very commonly used contaminant fit and transport model that converts the Freundlich constants into retardation factors.

A retardation factor, and this is what’s important, is defined as… A retardation factor of one means that the contaminant was moving the same pace as groundwater through the subsurface. A retardation factor of 10 means that the contaminant is moving at one-tenth the speed of groundwater. Okay? So, with PFOA, if you have a mid-range dose of PlumeStop in the subsurface, say, 2,000 parts per million, you have a retardation factor of 80 if you have a starting concentration of 1,000 micrograms per liter of PFOA. If you start with 100 micrograms, again, these are exceedingly high, you have a retardation factor of 570. Now we’re getting into reality. If you have a 10-part per billion plume of PFOA, you have a retardation factor of 4,000. That means that the contaminant is only moving at one four-thousandth that of water. For PFOS, it’s even better. For PFOS, at 10 micrograms per liter, you have a retardation factor of 10,000. What that means is the contaminant is only moving at one ten-thousandth the speed of groundwater. So, in order to move through a zone of PlumeStop, if it takes water a year to get across, it’s gonna take 10,000 years for the PFOS to get across.

So, let’s translate this into an example site. Let’s say we have a barrier of 16 feet. Now what I mean by a barrier is… What I mean is, if we’ve gone into the subsurface and either gravity fed or under low injection pressure flowed PlumeStop through an aquifer where it painted the aquifer flux zone with a two-micron layer of PlumeStop, and that zone was 16 feet wide so that a unit volume of water impacting that zone has to flow 16 feet before it gets on the other side, and we use a single application of PlumeStop at a mid-range dose of let’s say 2,000 parts per million, and the seepage velocity is 160 feet per year, that means… Oh, I’m sorry, 160 feet a year. And let’s say our challenge concentration is very high. It’s 100 parts per billion of PFOS. Well, the groundwater transit time then would be one-tenth of a year which is 36.5 days. In other words, a unit volume of water with the PFOS in it would take 36 and a half days to get through that zone of PlumeStop in the subsurface. The PFOA transit time is 57 years. That PlumeStop is gonna retard that PFOA for 57 years. And PFOS it’s 200 years. So, that’s the power of painting that aquifer flux zone with PlumeStop, converting it from a polluted aquifer into a purifying filter.

So, with regard to PlumeStop, we’ve tested it on all sorts of PFOS contaminants. And by the way, what you saw here was at 100 micrograms per liter, which is a very high concentration. And again, because our isotherm data is a Freundlich isotherm, we have much, much higher efficiency at lower concentrations. So, lower starting concentrations perform at a much higher efficiency. So, we’d expect to see much longer retardation with lower starting concentrations. But let’s talk about other contaminants for just a minute. PlumeStop doesn’t work just on PFOA and PFOS. In fact, this is actual site water that was from a site in the southern hemisphere was send up to us from down under for evaluation. And I just wanted to give you a look at what else we can treat.

Here’s the baseline. This is time zero data. It just gives you an idea of the concentration starting. Here’s the control which shows you what we had, what types of concentrations in the control with no PlumeStop. And then here we have PlumeStop. This is after, I believe a 14-day contract, so we just wanted to make sure that we were fully at equilibrium. And you can see everything was below limited quantitation with the exception acid which is below regulatory limits, but above method detection limits. And this is just a simple batch test which really has little bearing on how it would actually perform in a quote barrier application because this is showing the full brunt of the competitive sorption between the more hydrophobic contaminants and the more hydrophilic contaminants.

When I say that, I mean hydrophobic is water hating which means those that don’t go into water very well but they go into PlumeStop really well. That’s the longer chain PFAS compounds. The shorter chain more soluble like perfluoro-butanoic acid which is carbon telomere on it, that compound wants to stay more in water than on the PlumeStop. And so in here you see it showing up and that’s because there’s more competitive contaminants in this mix. But if this was flowing into a zone treated with this whole mixture, you would see the more hydrophobic compounds stripped out early on and moving through the barrier and that would leave sort of the virgin PlumeStop to sorb tightly the perfluoro-butanoic acid series.

So, a little bit more about this. In red, you see what are known as precursors. And by the way, this analysis is actually the method 537, it was developed by the unregulated contaminant monitoring rule under the Office of Water at the U.S. EPA. This is what most people use at different state levels to monitor PFAS. And in this case, you see three precursors in here as well. Precursors, if you’re not familiar with them, they’re actually compounds that were used in the manufacturing of the PFOA and PFOS and are often co-contaminants. And they will actually oxidize in the subsurface. They can be bio-degraded and oxidized.

The end result of the oxidation, however, and these are precursors here, are the carboxylic and sulphonic acids which you see at the bottom. And so if you’re familiar with the Top Assay, we’re seeing many people now performing these total or precursor Assays, and the reason for that is that they can then simply use the equivalent of method 537 and it will catch all of these precursors once they’ve been converted to the sulphonic and carboxylic acids. The reason I bring this up is that the precursors are generally much more hydrophobic than their final endpoint when they’re oxidized at the Top Assay. So, we actually expect very high-efficiency adsorption with PlumeStop on these precursors probably much more than the oxidized end product. So, we will be catching most all of these precursors very effectively with PlumeStop.

So, one other thing I wanna mention is, we actually… Dr. Jeremy Birnstingl on our team has spent the last three years developing a competitive sorption model which actually shows this…that actually shows the competitive sorption among challenge species against PlumeStop. And this is actually a center line down a plume from the head of the plume to a toe of a plume down a single transact cut right through it from top to bottom. And it shows a quote barrier, a 16-foot zone of PlumeStop being in placed, and what the results and sorption is with the competitive species.

Remember, anytime you sorb the carbon whether it’s in a canister, whether it’s PlumeStop sorbed on an aquifer matrix, you have this competitive sorption. It’s actually a dynamic equilibrium where a contaminant sorbs but it’s only retarded and it’s gonna come back off eventually. And whether it’s PCBs or whether it’s alcohols, they all are in a competitive sorption dynamic. So, the question is what is the interaction and how long will it take before the more hydrophilic least species leave the barrier zone? And we now have a very effective model that we can run on sites to show this anticipated competitive sorption before we move forward with an application in the subsurface. So, that’s available to you through us as well.

So, let’s talk for a minute about environmental risk and then we’ll move into an actual case study. So, environmental risk. Back in 1987, there was a gentleman named Dr. Frank Lawrence. He has since passed away, but Dr. Lawrence was a medical doctor who had a practice in Portland, Maine. He left his practice in Portland, Maine to start the world’s first environmental risk assessment business. And Frank was very, very, very influential on the entire groundwater and soil treatment industry. He would go around the nation speaking to regulators and speaking to PRPs and talking about the actual impact of contaminants in groundwater and how that relates to clean up goals. And he made the case that we need to have contaminant cleanup levels that are commensurate with the use of the land. And Frank… Dr. Lawrence was really the first one that came forward and expressed that environmental risk is equal to hazard times exposure. And you can have a hazard out there but if there’s no potential for exposure there’s no environmental risk.

And I remember Frank speaking to a room where you could hear a pin drop and he asked the question of a group of regulators. He said, “Would you ever allow a 3-year-old child to stand within 10 feet of a man-eating tiger?” And I remember it was silent. And Frank then said, “It happens thousands of times a day in zoos throughout the world.” It’s just that there’s a six-inch-thick sheet of safety glass between the child who’s tapping on the glass and the man-eating tiger. The hazard exists there, it’s a living, breathing flesh-eating tiger. It’s just that there’s no potential for exposure. So, the three-year-old child jumps back in his stroller and his mom pushes him off to the seal exhibit. So what we’ve done is we’ve actually just limited the route of exposure to that hazard. And that example resonated with me.

When we talk about elimination of risk today, well, risk-based corrective action, Rebecca, is now commonplace throughout the world. I mean, people realize if you put up the sheet glass, the tiger is not gonna be attacking people. They realize that we can grant no further action letters if the plume is not expanding and if there’s no receptor impacted. If that supply well or that surface water body isn’t gonna be impacted, if there’s no route of exposure, we can grant it no further action. And examples are commonplace, there’s no further actions. I mean, gas stations throughout the world are now closed all the time with regulatory closure even though they have benzene on them and PIH which are known carcinogens and toxins. I mean, these things are known carcinogens.

There’s still some debate about the toxicity PFAS, but we’re allowing benzene and PIHs to be left on gas stations because we can show there’s no route of exposure. Now some people argue well, that benzene’s gonna biodegrade over time. Well, chromium plumes don’t biodegrade over time. And yet all throughout the U.S. and overseas, sites are being closed or allowed no further action after we’ve treated these chrome plumes from hex to. Now, if conditions change in the aquifer, if there’s an EH or pH shift, there’s a potential for a chrome to be formed again. But we trust because we monitor once a year that water downgradient that people are safe because that trivalent chrome isn’t converting and it’s not mobile, so no further action is granted. And we can say the same with PCBs and treated activated carbon.

So, how does this relate to PFAS? Well, environmental risk, in this case, is equal to PFAS times exposure. Well, with injection of colloidal activated carbon into the subsurface, you bound up that PFAS, you bound it up onto the aquifer matrix itself. And once it’s bound to the aquifer matrix itself, there’s no route of exposure. It’s swerved out, it’s downgradient, there’s no potential for exposure because it’s retarded. And when there’s no exposure and no pathway for exposure, there’s no environmental risk. So, colloidal activated carbon can be used to eliminate the risk from PFAS.

Strategies are simply cutting off a plume next to a surface water body. This is a no-brainer. I mean, trying to pump and treat next to a surface water body, it’s generally a fool’s errand. So to put in a barrier, this would be the PlumeStop here along the edge of the surface water body. And simply covering over or excavating out the source, over time what you’ll have is the plume will migrate into the PlumeStop, it will be sorbed there and you will eliminate the route of exposure to that surface water body. You can also cut the time to a fraction of the time it takes for that by having multiple areas of PlumeStop. You’ll see that that’s much faster to treat the entire plume. If you have a potential source zone, you can actually contain that prophylactically with PlumeStop. And over time, you’ll see that the contaminant will just sorb outward into the…or move outward and sorb onto the PlumeStop. And a very interesting idea is to surround a production well or a domestic supply well with PlumeStop and that way you don’t have to treat it above ground. The contaminant will just go into the PlumeStop.

So, let’s move into a case study. This is a case study of a furniture facility in Canada. And the background here… The initial drivers was hydrocarbons. We had hydrocarbons at 100 to 5,000 micrograms per liter and the formation was a silty sand. We had a water table at three to five feet below grade. It was… And Rick McGregor was actually the person that actually applied this. And Rick is a very technically trained. He was a Waterloo masters trained hydro-geologist who runs a company out of Canada, and he was going to treat this hydrocarbons site with PlumeStop when he realized that there was a fire training area nearby. And he asked the question, “I wonder if there’s PFAS here.” So, there was sampling for PFAS conducted and Rick McGregor at In-Situ actually found PFAS on the site. So, this is a diagram. Here in the upper part is the actual hydrocarbon plume area and here is where he recognized that there was PFAS. The fire training area was right in here. And I want you to focus on these lower wells or these blue dots.

Here’s the same blue dots down here and you’ll see here’s the fire training area and here’s the PFOA plume, here’s the PFAS plume. And here you’ll see that the red represents 3,400 nanograms per liter. So, fairly high concentrations in this area. They took the PlumeStop that was actually planned for the petroleum hydrocarbon plume and spread it out across the entire area including this PFAS area. The squares are actually the injection sites. The results… Here’s the actual PFAS and PFOA concentrations in the key monitoring wells before the colloidal activated carbon treatment with PlumeStop. And here’s of the highest concentration was the PFOA, pre-injection at the, in this case, I guess it’s 3,300, 3,400. Okay, and this is before treatment. After treatment, here’s the final. You can’t see it because it’s too small. It’s less than 20 nanograms per liter, so it’s below detection for both PFOA and PFAS on all wells.

I do want to mention that… Well, the hydrocarbons all went to non-detect, the PFAS to non-detect. We’re at two years of data and counting. There was a hit at 18 months of PFOS and I believe that was a 20 nanograms per liter and also PFUNA which is the 11 carbon long perfluorinated compound. And they were just both above the level of connotation but well below the standard. They’re very suspect. Both of these compounds are very hydrophobic. They would be tightly bound to PlumeStop. If you were gonna see something come off, it would be one of the hydrophilic species like the butanoic series, butanoic acid. So, we were verily suspect of that data and it turned out all data taken since then has shown that those compounds are below detection. So it’s most likely a laboratory or sampling error. So at any rate, two years and counting all non-detect.

So, another gentleman in Canada, unbeknownst to us, Dr. Grant Keri, he’s an internationally recognized hydro-geologist on contaminant and transport expert. Independent of us, he got with Rick McGregor and studied the data. And on his own, he ran his models using the Freundlich constants that we had given him for PlumeStop and he performed sensitivity analysis, giving the estimate of longevity, how long will this barrier last. And here’s what he showed. Here’s, again, the area where the PFAS was treated in the monitoring wells. He took a point here, a well there and calculated the breakthrough time, I’m sorry, the time to contaminant breakthrough. When would you expect to see contaminants show up in that well?

Based on the Freundlich isotherm that we gave him for PlumeStop, he estimated a longevity in excess of 100 years. You would not see PFAS show up at the level of regulatory level for over 100 years. He then said, “Well, what if we’re wrong? What if the Kf is an order of magnitude lower than that, like 10 times? Let’s say we’re off by tenfold?” Well, then you’d only have an 80 to 90-year longevity. Let’s say it’s off by, again, twice as much and let’s say it’s only 2,000 instead of 50,000. You’d still have 30 years of longevity of treating this site with what was injected. So again, PlumeStop is a very, very effective answer.

So, we then… Just to give you an idea of the cost comparison. The total cost of implementing this was $73,000 to design the product and the application was $73,000. This is not including any monitoring that the regulatory agency requires. Let’s say that it didn’t last 30 years. Let’s say we’re wrong and it only lasted 20 years. $73,000 is lasting 20 years. If you were to put in a pump and treat system and you use the most efficient gack, granular activated carbon, it would take at least $150,000 to implement CapEx. And if we’re doing a 20-year comparison, let’s say it only cost $60,000 a year which by anyone’s measure is low. But anyone that’s skilled in the field, that’s a low comparison. In today’s dollars, that’s $1.3 million versus 73,000. So, there’s really no comparison. It’s much, much, much more cost effective to treat In-Situ with PlumeStop.

This case was actually published in the journal “Remediation”, volume 28, number 2. It was last month it was published, so you’re welcome to grab that. If you want to, I think that’s available from us on our website. You can contact us on our website and download that. So, in summary, colloidal activated carbon is a proven technology. It’s been used on over 200 sites around the world. It eliminates the risk of PFAS in groundwater. There’s no doubt about it. If the site has been injected, it’s now been proven. Experts have run sensitivity analysis, etc. It’s a passive plume management approach. If you ran the sustainability calculations on the carbon footprint of pump and treat versus colloidal activated carbon, you’d be amazed at how efficient it is and how much more of cost savings there is in terms of carbon footprint to the environment. It’s very cost effective, low CapEx upfront, and very low operating expense.

And one last slide here to give you an idea of what’s going on in 2018. In July, a major U.S. EPA Superfund site was injected full scale with PlumeStop and the project manager just told us last week that saving them hundreds of thousands of dollars a year in operating cost over pump and treat. A petroleum company in Saudi Arabia has a PFAS plume. That’s being injected, I believe, it’s this week or next week. I know that the shipment was on its way, so it’ll be going, if not last week, this week. There’s a large industrial project site in Western Michigan that the consulting group is working with us on and they plan to go into the ground to protect surface water bodies from foaming PFOS in October.

There’s a national interest site in Italy. It’s like their Superfund site, that will be going in Q3. There’s a military, U.S. military base in Germany where PlumeStop is specified full scale to protect a domestic residence area downgrading of a fire training pit and airfield. And there are several demonstration projects and smaller demonstration projects that will be going on in Q3 and Q4, including a DOD facility in Michigan.

So, we’re moving forward on many PFAS sites. And just in terms of PlumeStop in general, there’s over 450 projects that are in the queue in the next year and a half to be injected. So it’s moving forward at a fast pace, and it’s a true solution for PFAS. So with that, I wanna thank everybody for attending. It was very great of you to give us an hour of your time. And if you have any questions, I think we can turn it over to Dane to take questions. It’s over to you, Dane.

Dane: All right. Thank you, Scott. That concludes the formal section of our presentation. And at this point, we’d like to shift into the question and answer portion of the webcast. Before we do this, just a few reminders. First, you’ll receive a follow-up email with a brief survey. We do appreciate your feedback, so please take a minute to let us know how we did. You’ll also receive a link to the webinar recording as soon as it is available. All right, so let’s circle back to the questions. We have a lot of questions today. First question is, this person says, “A concern in my state,” and that is Michigan, “Is that once PlumeStop is applied, it may need to be monitored for many years. The concern is that after a few years, there may be contaminant breakthrough which makes it hard for no further action reports to rely on PlumeStop indefinitely. Can you speak to whether contaminant breakthroughs are an unfounded fear and why?”

Scott: Okay. Well, a really good question. It goes back to what I was showing you from Dr. Grant Keri’s work. We’ve done the sensitivity analyses on the length of time we expect to have the retardation. And it’s in the order of decades and decades. I do think, though, that if we’re gonna do a no-further-action that I think it should be contingent upon there being an annual groundwater sample taken from a sentinel well downgradient just to assure that the public, in fact, is protected and that there is, in fact, a break in the pathway to exposure.

So I think all the data shows that we should have decades and decades of retardation, but I think that there probably should be a requirement for a monitoring well downgradient but periodically sampled. And if indeed it does show up that there is contaminant breaking through, let’s say, in 20 years, you can simply just put in another, in this case, $73,000 of PlumeStop and you get another 20 years. We’ve done a lot of testing in the laboratory and shown that you can load PlumeStop on PlumeStop and there’s no impact on the amount of effectiveness of PlumeStop. Once you layer on another layer you have another 20 years or 50 years or 100 years. So, hope I answered that.

Dane: Okay, great. Thank you, Scott. Here’s another question. This person says, “I actually have a 10 ppm plume of PFOA and need to get it down to 10 ppt. Will PlumeStop work for that?”

Scott: Yikes, 10 ppm. Holy smokes. Okay. So, that’s a high concentration. I think that we’d be happy to look at that and see what type of impact we think we could have on it. We just would run it through the competitive sorption model and show you how much longevity we think we would have. I will say though that one of the places that’s a limitation for the effectiveness of PlumeStop would be if it’s in a fire training area where these high concentrations of PFAS might be co-mingled with diesel fuel that they were burning and they would go and… Diesel fuel they often put it out with a foam. If you have diesel fuel mixed with your PFOA, the diesel fuel, unfortunately, will competitively sorb on to the carbon and bump the PFOA off. So we’d have to look at that and we just ran it through the models and do some testing on it. But we’d love to do that, in fact, so please contact us.

Dane: Okay, great. Probably have time for one more question. This question is, “How given the fact that the contaminant is not degraded and only bound up onto the PlumeStop in the subsurface, how has this been received by regulators?”

Scott: Extremely well. I mean, regulators are aware that no further action is given in all the types of settings that I’ve mentioned. And if we can show that we bind it up and if there’s an adequate monitoring downgradient, there’s no reason that this shouldn’t be applied. If you look at pump and treat systems, when you put in a pump and treat system downgradient, remember, you’re drawing higher concentrations of these contaminants from upgradient downgradient. And as you’re doing that, you’re filling the flux zones with high concentrations, relatively high concentrations, of these contaminants which are forward diffusing into the lower permeable zones. Well, over time, though, that’s gonna have to come back out and back-diffuse.

So if you start pumping and treating as a solution, you’re actually gonna be retracting the entire problem if you’re pumping downgradient. And also if you’re collecting the PFOA or PFAS on activated carbon or IX brines, what are you gonna do with those? Are you gonna go take them off to another place and dispose of them? There’s risk anytime you transport this stuff or dispose of it someplace else. So, I think a lot of regulators are now saying, “Why not just lock it up and do a reasonable job of monitoring downgradient to make sure that, in fact, it’s captured and that there’s no exposure to the public?”

Dane: All right. Thanks very much, Scott. We are out of time, so that’s gonna be the end of our chat questions. If we did not get to your question, someone will make an effort to follow-up with you. If you need immediate assistance with a remediation solution from REGENESIS, please visit for regenesis.com to find your local technical representative and they will be happy to speak with you. Thanks again to our presenter, Scott Wilson, and thanks to everyone who could join us. Have a great day.[/read]