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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 keep this under 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 the webinar or audio quality degrades, please disconnect and repeat the original login steps to rejoin the webcast. 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 don’t address your question within the time permitting, 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, we’ll focus on a case study on the successful In-Situ remediation of PFOA and PFOS using PlumeStop Liquid Activated Carbon. With that, I’d like to introduce our presenters for today. We are pleased to have with us Rick McGregor, president of InSitu Remediation Services Limited. Rick has over 26 years experience in groundwater and soil assessment and remediation, has worked in over 30 countries, and has authored numerous papers on groundwater assessment and remediation.
He holds a Master of Science degree from the University of Waterloo in Hydrogeology and Geochemistry, and is a certified groundwater professional in Canada and the United States. We’re also pleased to have with us today Maureen Dooley. Director of strategic projects at REGENESIS. Maureen has more than 25 years of experience in the remediation industry. In her current role at REGENESIS, she provides technical leadership for complex soil and groundwater remediation projects throughout North America as well as remediation design, strategy, and business development in the Northeastern United States and Eastern Canada. All right. That concludes our introduction. So, now, I’ll hand things over to Maureen to get us started.Click here to Read Full Transcription
Maureen: Well, thank you, Dane, and I wanna welcome everyone from beautiful Toronto. It’s a lovely blue sky and a crisp, crisp cold day, but we are ready to get started, and I am really delighted to have Rick McGregor here as our webinar speaker and he will be speaking on the topic of a field study for the treatment of PFOA and PFOS. Now, I’ve had the privilege of working with Rick for many years and Rick and his team at IRS cell have worked on many, many REGENESIS sites, and they really are our go-to company when we have complicated site applications, and they are our premier PlumeStop applicator in Canada. And I’m very much looking forward to this presentation that’s been prepared, is I believe this is the first full-scale application of an institute remedy to address PFOA and PFOS compounds. And I know this talk is full of technical detail that relates to reagent injection as well as the application to address the PFOS compounds.
But before I turn this over to Rick, I just want to briefly describe the reagents that will be referred to in today’s presentation. Now REGENESIS, as you’re familiar with, are involved with the research development commercialization of environmental technologies, and we specialize in developing these solutions for, you know, they say this wide range of contaminants. And you can see by the different product lines that we have that we address bioremediation is in institute chemical oxidation and vapor mitigation. In today’s presentation, we’ll be focused on two and that’ll be the PlumeStop Liquid Activated Carbon and oxygen releasing compound.
Now the PlumeStop, what is this? The PlumeStop Liquid Activated Carbon is a sorbent, and it’s designed to remove and promote degradation of groundwater contaminants. The PlumeStop itself is composed of fine particles of the activated carbon that are suspended in water through the use of unique polymer and dispersion chemistry. Now the PlumeStop is gonna behave like a colloid, it’s gonna bind to the aquifer material and ultimately rapidly sorb any contaminant. And that contamination is then in turn biodegraded. So in essence, we’re going to paint the subsurface with this liquid activated carbon, and then enhance biological degradation. Now I’m going to show you this visual that compares liquid activated carbon with powdered activated carbon. And this is a column study that’s been conducted in our laboratory and we’ve shown this many, many times, but I think it’s just really important to understand about distribution. When you’re trying to apply any reagent, it’s necessary to be able to have it delivered to the locations in the flux zones where most of the contamination resides. And this is something that Rick is going to talk a little bit about in his presentation and some of the field application of the PlumeStop Liquid Activated Carbon. And again, just to reemphasize that some of the challenges that we are confronted with, is our ability to achieve, you know, low cleanup standards and part of that is due in part to the idea of back diffusion or matrix diffusion where contamination may be hung up in your finer grain materials, but your contamination is also present in your more permeable zones.
And when you’re injecting reagents, they’re gonna follow those more permeable zones. And one of the advantages of the PlumeStop and the sorbent is to be able to address and manage the back diffusion that sometimes may occur at some of our sites. So, once you have a contaminant that’s been sorbed you know, what’s next? So, the idea of the PlumeStop is you’re going to sorb this contaminant but you want to be able to promote a biological or even an, you know, an sort of reaction.
So, the PlumeStop itself or the surface of that is gonna act as a matrix to promote the growth of the microbial communities. Quite often, we’re going to co-apply an electron acceptor or an electron donor. In this case that will be presented, oxygen-releasing compound was applied with a PlumeStop to help promote aerobic biodegradation. Now with the PFOA, PFOS compounds, there’s no biodegradation associated with that and that’s sorbent only, but I’ll let Rick discuss the details of the presentation and get into that further. So, anyway, without any further ado, I’ll pass this over to Rick and the person that you’re here to listen to.
Rick: Thank you, Maureen. And I’d like to thank REGENESIS for allowing me to do this presentation today. So today, we’re going to concentrate on a field study that we did in Central Canada. It was done in the spring of 2016, and there’s been monitoring since then. So we’ve been about a year and a half into the monitoring events. We’re not going to spend a heck a lot of detail on the background information as most of you probably are very familiar with PFOS and PFOA, and what they can do in the environment and the causes and how they’re put into the environment. So we’re going to try to concentrate any essence of time just on the study itself.
My email is on there or people at REGENESIS can also pass you on if you have any questions after the seminar. So, a brief background is obviously we’re dealing with per and polyfluorinated alkaline substance or PFOS for short. Two of the more common ones or more familiar ones are the PFOS and PFOA, which are probably the most two discussed and most two studied of the compounds out there. But that said, they’re just two of probably thousands of compounds that exist in the environment or are being manufactured. Why are they of a concern? They’ve been shown to bioaccumulate and that has raised all sorts of issues in the last 10 or 15 years in concerns. From an environmental point of view, we have really serious challenges with trying to detect these compounds in the environment due to the low detection rates and limits needed. For example, the EPA is part of the health advisory limit of 70 parts per trillion or 70n nanograms per liter which is extremely low.
Other challenges with these compounds are is at fate and transport within the subsurface not really well understood in which studies just really coming out in the last two or three years. I’ve listed here three of the more what I could say more the intensive studies done and they’re excellent studies with Dr. Weber at Harvard, I did some work at Cape Cod, as well as Anderson and the people at Colorado School of Mines as well as people out in Minnesota. So these are three excellent papers that discuss fate and transport in various environments of the PFOS compounds.
So, the EPA kind of estimated there’s about 6,000 Americans exposed to PFOS compounds in the U.S. due to groundwater issues. Where does PFOS come from? Well, it turns out it’s based to the…we found it in repellents for fabrics of those coating reagents as well as a firefighting foam used at airports and military bases. So it potentially is quite well widespread and due to its low toxicity levels, it could be a serious issue for us to address.
So typically, we look at PFOS right now, and how is it treated? It’s usually done by pump and treat where the plume is being controlled by pump and treat. As most of us know, pump and treat generally can be effective for the containment of groundwater plumes. It’s not effective for the remediation of groundwater. When we do pump, bring it to the surface, it’s generally treated of activated carbon and that’s most common it’s generally that these expensive option available but the carbon itself does require disposal or regeneration once it’s a consumed.
This is the complete list of things but other things are on an exchange productions which are very effective especially at low concentrations where you have to do plumes but it can be very expensive. Now, it can be regenerated, but once again, that’s expensive and timely process. There are membrane filtrations, which once again, are very energy intensive and thus can be very expensive. Those are three of the more common treatment trains. There are others out there that are being done but once again, they’re relying on bringing the groundwater to the surface, which can be very expensive and generally will not result in remediation of the plume but instead just capture in containment of the plume.
So we’ll talk about the InSitu treatment. There’s a variety of reasons why InSitu really hasn’t been used for PFOS. One is is there’s very limited demonstrated options especially in the field for using the treatment of PFOS, and one of those is is one of the more common methods for InSitu treatments is chemical oxidation. Chemical oxidation can be quite challenging for PFOS compounds just because the carbon fluoride bond which is very resistant to chemical oxidation and thus very stable. That makes the compounds great for its uses but unfortunately doesn’t make it great for derogation both chemically or biologically. Also, we are required to get to very low concentrations usually sub 100 parts per trillion, which anybody’s done remediation knows that’s very hard to do. And one of the reasons it’s very difficult to do is and due to the back or matrix diffusion problems that we have over time.
Some of the technologies that are being done in the lab or even limited field are some of these technologies are addressed to here where a chemical oxidation process being tested by ARCADIS and things called ScisoR. There’s been some work on Nano Palladium and zero-valent iron, activated persulfate using heat or base activation. There are some vitamin B12 work being done as well as activated carbon. And by activated carbon, I mean, the injection of activated carbon in subsurface.
So activate carbon which we’re gonna concentrate on today as we discussed before, it’s very well demonstrated for aboveground treatment, but for the InSitu use is it’s just recently, probably within the last four or five years, we’ve been able to actually effectively inject it into the ground. So, the challenges, of course, for the InSitu is we are still learning about fate and transport of the compounds themselves. So we’re really not quite sure how they behave in the subsurface. So, unless we really understand how they behave in the subsurface, it’s very hard for us to remediate them if we don’t really know where they are. And there’s a term here I call injectability, and that’s just my term for how easy is it for us to get the reagent that we’re trying to inject into the ground. This is a practical thing is that an applicator, this is one of the most important things we look at. There are some great chemicals or reagents out there, but they’re very hard to get into the ground. So they’re what I call injectability is not great. That falls into the distribution as anybody’s done InSitu remediation knows the distribution of your reagent in the subsurface is probably the hardest thing we deal with.
And that’s do the heterogeneity of the subsurface is health of the aquifer as well as things like the injectability of the compound itself as well as its persistence in the ground. I’ll concentrate on that parameter quite a bit in this talk because I think it’s one of the key reasons why InSitu programs succeed or fail in the field is because of this distribution challenge. The other thing with activated carbon is its lifespan. And by lifespan I mean, it’s got a limited capacity. It has only absorbent sites. Now those number absorbents in the sites depends on the type of the activated carbon you’re using as well as the grain size which affects the surface area. There’s a variety of different parameters that affect that, but that capacity differs for different compounds and especially for PFOS compounds.
There’s nearly thousands of PFOS compound, so the absorption isotherms for each of those compounds is gonna vary with time. One of PFOS is one of the more readily absorbed compounds versus the shorter chain PFOS compounds which tend not to absorb as well. That said, they still will absorb, they’re just they will break through your carbons sooner than later. If you have commingled plumes like such as I said we’re gonna talk about today, where you have other petroleum hydrocarbons or chlorinated hydrocarbons present, you will have competition for those absorption sites. So, that makes it very difficult to estimate timelines for your lifespan of your carbon because you have lots of competition for those absorption sites.
And then the other factor that we’d like to look at is is we’re not really destroying the PFOS compounds when we absorb it onto carbon, we’re just making them unavailable and by that I mean, we remove them from the groundwater and putting them into the salt phase or absorb phase. From a risk point of view, usually, our risk are involved with your vapor or groundwater. So, this can be very effective for cutting off that transport pathway. However, at the end of the day, we are not looking we’re not destroying the compounds themselves. And finally, and one thing that really has no work done on, Dr. Carey got into it a bit a couple months ago when he did a previous webinar about back diffusion of these compounds. Especially, at these low detection as well as regulatory advisory, then it’s back diffusion could play a very big role in how successful we are in the remediation of these compounds.
So, I’m gonna talk about a bit about diffusion. I’m sorry distribution. This is not from this field site this is in our field site that we had the opportunity of looking at what I’ll say the injectability and distribution of two types of activated carbon. We’re looking at liquid activated carbon which in this case is PlumeStop. And then we also injected a powdered activated carbon, and now this powder was very fine-grained but it is still a powder. I mean, what we did was take this plume and now this is not this site, this is a different site but we took the two types of activated carbon and we injected it literally, split the plume in half and on one half we injected the liquid activated carbon on the other half we injected powdered activated carbon. And then we went back and set off a certain distance from the point of injection, and we looked at the distribution of the activated carbon within the soil itself.
So we wanted to see two things. One is we wanted to make sure that the carbon was going where we want it to and I call that the target zone. So on these graphs, you’ll see dash lines basically at about 1.7 meters and 2.1 meters. That was our target zone. This site, we had petroleum hydrocarbons that were within that area. So we wanted our activated carbon to go into that zone. The second thing we wanted to do is, is what was our radius of influence? That is, of course, we all have to assume a radius of influence when we do a design, and, you know, the most common we see is about 5 to 10 feet radius influence. So we wanted to confirm that radius influence was a valid assumption.
So, what we did was we did the injection, and then the same day we went back and actually took course. Two feet, 5 feet, 10 feet, etc. from the point of injection, and then took samples every 6 inches in those coarse, and we submitted them for analysis, to see if we could actually determine the content of activated carbon as well as just look at it is. As you can see from these plots which are depth on the y-axis and concentration along the top, I didn’t put units in but we’re talking about 0.1 to 0.3 weight percent of the coarse itself being activated carbon. You can see here for the liquid activated carbon, we were very…we had very good distribution within our target zone, and we actually did detect a slight hit of activated carbon approximately 7 meters which would be about 22-23 feet from the point of injection. The reality is is we’ve probably seen at about 5 meters away which is about 15-16 feet.
So we had the excellent distribution and we had excellent radius of influence on this for the liquid activated carbon at this site. For the powdered, what we seen was a very basically a spike where we seen very…we got it within the target zone but we seen basically one very high concentration. It was about two to three times higher than what we seen for the liquid activated carbon. But for the powdered, we only seen it really within one sample within the core and that was very consistent right out to seven meters. The picture on the right just shows a bend that’s about a two-inch bend, that you’ve got a picture there of, and you can see the actually the activated carbon within the sand itself.
What we think here is when we went back and did a detailed hydraulic conductivity measurements of the sand, we actually have a zone of approximately one and a half others remained to higher hydraulic connectivity within that sand scene. And so what happened when we injected the activated carbon and the powdered form here is the activated carbon found the preferential pathway and went into that sand scene. Whereupon, for the same site, when we did the liquid activated carbon, it appears to be…it nailed better distribution in that sand scene even though you do see the spikes where that sand scene is, you don’t see as pronounced distribution within that sand scene for the liquid activated carbon. So, distribution in this case, you know, it’s a very important parameter and you can see the effects on it here. The lifespan, so this is the area important part with the activated carbon is this, will absorb and will stay on?
This is a batch test that at REGENESIS was generous enough to provide me when they were doing some isotherm testing for various people at PFOS compounds. And what they found was just that all the compounds they tested did absorb quite well even the PFBS which is a four-chain PFOS compound. Well, it didn’t absorb as well as the PFOA, the C8 chain, it did sorb well and they did see basically 99.8% absorption. Going from a very high concentration approximately about a 100,000 nanograms per year down to approximately 190,000 nanograms per year. So they did see very good absorption. However, it does show that you do get better absorption which would be predicted by the isotherm, predictions of the heavier chain or higher chain PFOS compounds versus the lower chain.
So this is another thing that you need to keep in mind when you’re doing it. A lot of times when you see on this day, the compounds we actually analyzed for the first year which is PFOS and PFOA. The last sampling we did at 18 months we did increase the number of compounds we were analyzing for to try to address this. The other thing is very important when you’re injecting activated carbon is the particle size which directly affects the number of absorption sites the surface area of the activated carbon. This is extremely important than the activated carbon, because the main process you’re relying on is absorption onto these sites. So the more sites you have, the better or the more you can absorb on.
So this is taken from Tom Higgins and his colleagues at Colorado School of Mines, a paper just recently published where they looked at basically different types of carbon in different types of grain size. In essence, without looking at it and they looked at PFOA versus PFOS absorption. As you would guess, PFOS does absorb better than the PFOA, which we would expect, but you also see a very drastic, you know, in the graph on the right, you see a very drastic difference between coarse grain material which at the grass near the top versus the finer grain activated carbon down in the red circle dots. On this case, you see about 30 times more absorption. It’s note here that the fine grain carbon they used here was about less than 53 micron, the PlumeStop itself is about one to two micron.
So, once again, we just stepped down in there or remain to grain size which you would expect would correspond to a greater surface area and thus more absorption capacity when we talk about the PlumeStop. This scanning electron microscope photograph is courtesy of REGENESIS once again. It’s a simple photograph or two photographs but it’s very, very informative. The photograph on the left is saying grains without prior to injection of the PlumeStop, and the photograph on the right is same grains with PlumeStop after injection. First of all, you can see how fine grain the PlumeStop is itself and how it coats the sand grain. So this is how it would work in an aquifer.
So, once you inject in the aquifer, you would see it distribute under the pressures that you would inject in under but then fairly shortly within days to a few weeks you will see a drop out of solution and start coating the aquifer particles themselves, which is what wanna do. So now, we’ll get into the site here. I’m gonna take credit for this site but the reality was it was a bit of an accident when it comes to the PFOS remediation. So it was a petroleum hydrocarbon spill and that’s why we were contracted to go in and remediate the residue petroleum hydrocarbons in the groundwater and there were some still in the soil. The main source of the spill was excavated. The residue concentrations in the groundwater were, you know, BTEX was about 300 parts per billion, F1 which is kind of equivalent to the gasoline range here in Canada was about 2 milligrams per liter where the F2 which is equivalent to the diesel range would be about 3.5 milligrams per liter. So now, Walker concentrations but well above the regulatory guidelines here at this site.
Just prior to us so we had to design the program to address these petroleum hydrocarbons. On the day we arrived at the site to do the injection, the consultant on site happened to mention that there was an old fire training pit basically they had used over the in the ’70s and ’80s, and the buildings cells have been used for fabric coating once upon in its history, and that kind of triggered something in myself. So we quickly went out and grabbed some samples and we submitted them for PFOA and PFOS prior to us doing the injection of the PlumeStop, and in this case PlumeStop and ORC.
Low and behold, when we got the results back, and we did find some PFOS, PFOA. They weren’t dreadful on lead concentrations but still well above the advisory limits here. You see about the PFOS, we had about 1,500 part per trillion whereupon the PFOA we had about 3,200 to 3,300 part per trillion. So not dreadful concentrations but not low concentrations either.
So if anybody who’s done this type of work you know that it’s very tricky how you do the sampling, you have to be very careful, but so I thought I put this in to hopefully answering by who would have these questions later on. But we were looking at…we followed the U.S. Air Force protocols for the sampling. We only used high-density polyethylene bottles and tubings to do these things. We obviously didn’t filtrate the samples and we tried to minimize a headspace and we, you know, biodegradation is sort of important. In case of PFOS, we try to minimize the holding time to less than five days.
Analytically, I’m not an analytical chemist so I will just glance here but the chemistry was analyzed using liquid chromatography-mass spectrometry, and that’s a very good method for low detection and complicated matrices. If anybody’s done this, one of the challenges with these compounds is the analytical. The samples themselves can be quite expensive to do and to get these low detection limits that you require can be quite a challenge for laboratory. So these are some contour plots of the concentration of PFOS on your left and the PFOA on your right for before remediation was started.
We put on the nettle square hatch box there where we thought the fire training area was. It’s a very small area. Here you’re seeing a size of the plume itself was about 25 to 30 meters, which is about 100 feet by about 10 meters which is about 25-30 feet. So not a big plume, the axis here correspond to a property boundary, but of course, nothing flowed off the property boundary. Everything stayed on site in this case. But these are the concentration, so you can see the plume itself fairly well defined. The big black dots represent wells, and the reason we had wells to the north or on the top of the page was is where we’re dealing with both a hydrocarbon plume in this case. That was our main concern here.
So the geology of the site was a glacial fluvial deposit i.e., it was a sand to silty sand quite typical of this area in Central Canada. It did have some sand lenses in here about two centimeters thick. So those were our major concern when we’re doing the injection. But when we did the injection, we used just special tools to try to overcome those type of heterogeneities within the aquifer itself. Hydrogeology, a very shallow water table which causes us some concern as applicators because you get too shallow, you don’t have much confining pressure, and then you can have a lot of day lighting which you can lose a lot of reagent to the surface. It was obviously unconfined aquifer, hydraulic connectivity about 2.6 meters per day with a gradient of quite a high gradient of 0.6 which worked out to a velocity about two feet per day which is a fairly high velocity.
For our calculations that we use the effect of porosity about 0.2. So we had a fairly high groundwater flow at this site in a very shallow. For the geochemistry, for you to geochemist out there, we have a fairly high alkalinity, so it’s a fairly hard aquifer from a water point of view with about 300 to 400 milligrams per liter calcium carbonate. Within the groundwater, the aquifer itself, the plume itself is very anaerobic. It was nitrate oxygen depleted with iron-sulfate reducing conditions. So we did see some iron, most of the sulfate had been depleted but there was some ferrous iron present within the aquifer itself.
The site was located near a major roadway so we did have some salt contamination, and that was once again, one of the concerns. With that effect, the performance of the activated carbon itself or the PlumeStop was this higher concentration of sodium chloride within the groundwater. So as I said earlier, the source was excavated. Dr. Carey in an earlier presentation did some numerical modeling for the site and had estimated the source mass flux to be about 1.8 grams per year. So not a very big mass flux at all, but that’s for the PFOS but still significant enough to be well above the regulatory guidance number for our area.
So when it came to the remediation options evaluated, now, we have to put this in context is we were looking at the petroleum hydrocarbons as being the main contaminant here. The PFOS were basically I don’t wanna say a research-y type topic but it was our main focus was petroleum hydrocarbon. So, we looked at pump and treat. We ruled pump and treat out just because the client wanted the site cleaned up and we just did not think pump and treat was gonna get us there anytime soon. We’ve looked at air sparging SVE. We ruled the air sparging out just because we did have diesel range fuel hydrocarbons present which would not the air sparge is not ideal for those. We did look at chemical oxidation. And once again, though, we have a very low that this site had a very low regulatory limit for the F2 value of about 150 parts per million. So, we did not use chemical oxidation just because we thought it’d be a very challenging site to get that low in the timeframe that they wanted.
We did look seriously at enhanced aerobic bio using your chemical reagents such as ORC, as well as I had oxygen versus injection using oxygen or using something like the Waterloo Emitters that would put oxygen in the ground. We also looked at sulfate reduction but we didn’t think that would get us there in time. We looked at thermal, the cost for thermal are just too much. Then we looked at activated carbon or absorption. We also looked at the zeolite for this site as well.
So, in the end, we chose liquid activated carbon. Why did we do that? Well, a couple of things I don’t wanna say we’re working against us was it’s still 30 in its infancy. There’s about 100 sites worldwide that it’s being applied at. We’ve been fortunate in Canada to apply it about 20 sites so we had very good experience with it, and it’s performed excellent for us when we’ve used it. So, we’re very comfortable with it. We’ve been applying it for a couple years. So we’re very comfortable with it. And the reasons we’re very comfortable with it, it has what I call excellent injection properties. So this goes back to the injectability of the product. It behaves once you dilute it to your injection concentrations, it basically behaves very much like water. It’s like injecting water. So, it doesn’t have the suspended particles in it, it doesn’t have viscosity or density issues, like things like permanganate or percarbonate these things that are harder, they inject very easy. Once again, it has a very high surface area with the activated carbon, so that has a very high potential to absorb things.
The other things our client liked was this potentially in most time we designed for a one-time application which means it would be very quick and remediation could be done very quickly. It’s very less disruptive because we used a direct push. So we’re in and out the site to say it’s an active site. So we’re in and out in two or three days and then we’re done. And of course, what most clients care about, the cost. So we were able to do this cost for about $75,000 Canadian which is about, what, $75 American. No. It’s about $60,000 American. But still, fairly reasonable for this remediation. The injection methodology we’re was we used based on pore volume. So we went for about 0.3 pore volume. We did it in one event, as I said earlier, direct push. We used geology-specific tools, and that just means we used tools that we have designed that minimizes the effect of heterogeneity while trying to maximize how we get things.
We used a very dense injection network about 3-meter or 10-foot grid. We do multiple intervals so we did two vertical intervals to make sure we maximize vertical and lateral distribution. We went in a fairly low pressure about less than 25 psi. And at each interval, we inject about 100 to 200 liters per location which is approximately 20 to 50 gallons per location. So we did a lot of points, small volume points.
So we were going after both plumes and this is just a symbol on the bottom showing the plume. So, we’re gonna concentrate on the bottom part, the PFOA and PFOS plume. We’re not gonna look at the hydrocarbon plume. But for both plumes, we put in about 725 kilograms of the PlumeStop itself, the liquid activated carbon, and enhance that with 440 kilograms of oxygen-releasing compound. That oxygen-releasing compound as Maureen pointed out earlier was not to address the PFOA and PFOS, it was to address the petroleum hydrocarbons. That was mixed in 7,800 liters of water and we injected 50 locations.
For the PFOS plume itself, of that total we did about one-third of it is 290 kilograms of the PlumeStop went into that plume. It also, because we did have petroleum hydrocarbons in there, we did put on 176 kilograms of oxygen-releasing compound, which was in about 3,000 liters of water. So we went in about 10% for the PlumeStop, which is a fairly common concentration. And within the PFOS plume itself, we had 20 injection points.
So, evaluation criteria was budget, which is always input distribution short-term and long-term results. So the budget, we did 50 locations, took us 3 days. We didn’t have very minimal day lighting, so that just means we didn’t waste product in areas we didn’t want. And as I said earlier, about $75,000 Canadian or $60,000 American. And that was done on time and on budget, so, from that point of view, we were very successful. Of course, that’s the easy part.
Distribution which I always considered the most important. So I’ve blown up the plume here. So what we did was we looked at really three things. We took course to look at the radius of influence, and we looked at did we get it where we wanted to get it? And did we get overall coverage i.e., there the goal in areas where we weren’t injecting? So we took a variety of coarse in the various areas. So, this just shows vertical profiles of overall coverage. So you can see the orange dots that we took between injection points, which is about we used a 10-foot grid here. So these are about five feet from any other injection point. And you can see once again the dotted lines represent the target zone we wanted to inject and we took five coarse.
As you can see here, we were very happy with the PlumeStop went where we wanted it to go within the core itself, and we did see excellent distribution throughout the plume itself. Wherever we took a core, we’ve seen the PlumeStop and we were able to verify it was there. So, from that point of view, we seemed to get good overall coverage. When we looked at the radius of influence, once again, similar thing but as you can see down in the plume map on the bottom of your screen, we basically did what I saw a similar study we did before is we just take course and we work it from a point of injection, and then we once again, we look at vertically. Did the PlumeStop go where we want it to and how far out too?
So we did see it approximately 15 feet from there, well, we actually did see a 15 feet from the point of injection, and we’ve seen the concentration is up to about point 0.4 grams per kilogram, which is very good. Detection limit for this type of analysis, which I won’t get into, it’s very difficult. This type of analysis took a long time to figure out how to analyze for this, but was about 0.1 grams per kilogram. So we’re about four times the detection limit.
Which brings me this curve is, how do we know we’re actually detecting activated carbon within our core? So we worked with a lab up here in Canada and we did some standards and the standard curve there is on the right and you actually can see, we actually…So we basically spiked sand samples, Ottawa quartz sand and sand with PlumeStop that no amount of PlumeStop, then we had to lab analyze those sort spikes if you want to look at it that way. And then we went back and we did. So, you can see here we got a very good standard curve. So we’re pretty confident we could detect what we’re injecting.
The other question is is what was the FOC of the site versus the basically the total organic carbon from the PlumeStop? As you can see from the two graphs here, those graphs have taken similar samples and we analyzed the samples for FOC before the PlumeStop was injected, then afterwards, we analyzed for the total carbon which had the PlumeStop in it.
And you can see that where, well, we’re over order magnitude greater about 30 times higher concentration once the PlumeStop is in the core than natural FOC at the core. So and this just shows some of the statistics for you mathematicians, statisticians out there but you can basically at the end of the day, we took 45 samples for each and we did it within the target zone and without the target zone. And you can see there’s a basically almost two and a half times for higher concentration within the target zone than outside the target zone for the total organic carbon.
For the FOC once again, basically, the FOC throughout the core was fairly uniform. So we took 10 samples, and you can see it really didn’t vary that much throughout the vertical. And overall, the total organic carbon after PlumeStop injection was about 35 times the FOC concentration. So the short and then what most people are probably here is the short and long-term chemistry. So, what we did was we took samples 3, 6, 9, 12, and 18 months after the injections. So I’m gonna call short-term anything less than a year, long-term anything after one year. So, we only have one sample event from 18 months which we just collected earlier late last month. For the first four monitoring events, we just analyzed for PFOS and PFOA. The last sampling event we analyzed for some extra PFOS compounds as you can see them listed there. I won’t go through with all the letters for an essence of time, but anybody like to do alphabets you can name these off later. We’ve also did a fair bit of detail in organic chemistry and we’ve actually did some biological sampling using next-generation sequencing.
I won’t talk about those right now but those become very interesting, those results too. So these are courtesy of REGENESIS. This is just the pre-injection concentrations at six wells within the plume. And you can see that the concentrations vary but this is the pre-injection. Post-injection, what we see is after 3 to 12 months, we haven’t detected any PFOS or PFOA for the first year after injection. They’re all non-detect sub which just means our detection now would journey about 20 to 30 parts per trillion at this site. At 12 months, we did get some detections for the BTEX and F1 compounds, but they were still well below the standards that we we’re shooting for.
The graphs on the right, if anybody who has attended Dr. Carey’s seminar in October, would recognize those. Dr. Carey did some very interesting modeling to show that once that PlumeStop is injected that all the PFOS, PFOA would basically sorb onto the activated carbon versus being in the dissolved phase or sorbed organic matter within the aquifer itself. I highly recommend you download his presentation as it’s excellent and it helps us predict what’s gonna happen in the future.
So after one year, this graph is kind of boring because after one year we had no detections of PFOS or PFOA after one year at any of the wells. So, they’re all less than 20 parts per trillion. So that was all great news. So long-term results and these results just came in basically last week. So there was 18 months after injections and they’re very encouraging. So, we did have, of all the wells we sample, we did have 1 hit for PFOS of 40 nanograms per liter which is still just above the detection limit but well below the regulatory guidelines number.
So, that was in one well and we did for all the other compounds that we analyzed, we did see a hit for the PFUnA acid just at the detection limit itself at 20 parts per trillion. So, the aquifer itself is, the remediation seems to be performing quite well. We’re 18 months in and really we haven’t seen, well, I guess I can’t say we haven’t seen any evidence of PFOS, but we’ve seen one well that has a bit of a hit, just a very moderate hit in itself. So far so good.
So, what’s gonna happen in the future? That’s always the million-dollar question, and once again, I refer you to Dr. Carey’s modeling. So what he’s did is taking the results from the thing, from our field studies and tried to predict and model the future. And the results, I’ll let you go through his presentations himself but they’re very, very interesting. What he’s basically found is based on some very conservative assumptions, we should not see anything we believe the source zone or migrate down gradient for well over 100 years. He predicted the PFOA, the concentrations after 100 years would be one-time six parts per trillion, so non detect. And the PFOS, we might just start to see it after 100 years at 24 parts per trillion. So, the modeling suggests that we shouldn’t…remediation should be successful here.
So, preliminary conclusions for the site is that the liquid activated carbon or PlumeStop, in this case, was very effective over the short-term, and by short-term I mean 18 months and counting for the removal PFOS and PFOA as well as for some of the other PFOS compounds that we’ve now analyzed for.
One of the things that we’ll be working on is, okay, it is absorbed, but it’s not destroyed. So, will it stay on the activated carbon? So that’s leading us to some of the work that we’ll be doing in the future is, we’ll be looking at will it stay on the activated carbon? It should, it has a very strong affinity but maybe some of the shorter chain PFOS compounds might be a thing. Dr. Carey is looking at some of the longer-term behavior including the back diffusion issues. And well, what’s been reported that biodegradation of the PFOS compounds doesn’t occur. One of the things we’re looking at is was the activated carbon, does that promote increased microbiological activity near the activated carbon itself? So, we started to look at that itself.
So that basically wraps up the presentation today. This has been now part of the PFOS Remediation, remediation group that we have started up here in Canada which has couple academic members right now. University of Toronto and Carleton University as well as couple industrial members like ourselves and Dr. Carey’s Porewater Solutions. So, we are trying to actively do some remediation and hopefully it leads to interesting things. And finally, I just like to acknowledge a couple people I stole a lot of figures from was Dr. Carey himself and Jeremy from REGENESIS. So, with that, I think we’re probably ready for some questions.
Dane: Okay. Great. Thank you very much, Rick. That concludes the formal section of our presentation. So at this point, we’d like to shift into the question and answer portion of the webcast. Before we do this, just a couple reminders. First, you will receive a follow-up email with a brief survey. We really appreciate your feedback. So please take a minute to let us know how we did. Also, after the webinar, you’ll receive a link to the recording as soon as it is available.
All right. So, let’s circle back to the questions. First question here. This one has a lot of acronyms, so please bear with me. It is, “Does PlumeStop retard PFBA, PFBS, PFPEA, PFP…sorry, I’m getting here, PFHXA commonly found in AFFPFAS signatures. Do these PFAS compounds require additional management compared to the longer-chain PFAS compounds?” That’s the question.
Rick: Well, I can’t answer all those compounds. I showed a slide near the start some of the isotherms that REGENESIS have been working on, that showed some of those shorter-chain PFAS compounds which show that they are absorbed. They obviously do breakthrough faster than the longer-chains but they are absorbed, and I think some of the shorter-chain ones, I think they’re absorbed at 98% at very high concentration. So, yes. You would expect them to be absorbed. It’s just a question of how long they will be absorbed for? So they will have breakthrough sooner than some of the longer-chains, but you would expect them to be absorbed. So I can’t go through every compound but some of the people at REGENESIS might have done some more experiments with some of those specific compounds that be able to or there might be some papers out there. But one of the challenges here and sort of your question outlines it quite clearly, is there’s a lot of compounds out there and every site has its specific ones that we’re of concern. So, unfortunately, we cannot analyze for everything right now. I know there are some analytical methods out there. One is called a top method which tries to get a grasp about how many overall view of the compounds available. But, hopefully, that kind of answers your question, but I know I can’t answer it totally directly within this hour.
Maureen: Hey, this is Maureen. I’ll just add a little on that. You know, with the isotherms, we do have some software internally that we can have a multi-component. We can we can look at, you know, many different components and different isotherms to try to get an idea of how much sorption capacity we would have so we can try at least model, you know, a particular site to be able to achieve and then adjust the application rates as needed to try to meet the objectives of the specific site.
Dane: Okay, great. All right. So, let’s see. Next question here, and this question is about that first example that you showed, Rick, comparing distribution of a PlumeStop Liquid Activated Carbon versus the powdered activated carbon, that’s what this questions about. And the question is, “How was the reagent injected specifically, pump and pressure flow rates in each case?”
Rick: So, in that case, is we try to keep it from an experimental point of view. We try to keep everything uniform i.e. the pump pressures, the pump flow rates, and the method of injection were all kept…so they’re all injected by direct push using a low pressure about 25 psi with a flow rate of less than 20 liters per minute. That is just to try to keep everything the same. I do know that for a powdered activated carbon, some of the manufacturers out there recommend it injected at higher pressures and at higher flow rates to keep it suspended. But in this case, in order to look at, keep the parameters similar, that’s the way it was applied in this case. So, yes. Personally, I would think if you gonna higher pressure, higher flow rates, the heterogeneity may, may or may not be overcome, and I mean, that’s gonna be a very specific question. But in this case, at this site, we kept all the parameters the same as best as we could.
Dane: Okay, great. Thank you very much. Next question here is, “How do you explain the 40 parts per trillion PFOS concentration after 18 months?”
Rick: That’s a tricky question. You know, we’re dealing with such low concentrations here, parts per trillion, that is it a laboratory artifact, or is it a sampling artifact, or is it real?
Yeah. And it was just in one well of all the well samples. So, you know, we’re treating it as a real number. So it might just be, you know, if you wanna think positively, it just might be a one-off and hopefully next sampling event it disappears, or it maybe it could be the start of a trend. Right now with one data point, it’s kind of hard to guess. You know, the laboratory numbers look fine so I don’t think it’s a laboratory error. It may be a sampling byproduct but, you know, once again, we were very careful how we’re sampling. So, I think right now, we’re treating it as a real number but for one data point, we’ll see what the next data point comes in. If it goes up, then we may have a trend, if it goes down, then that might just be an artifact type thing. Unfortunately, I don’t wanna go too far out online right now based on one data point at one well of on the site for five sampling events. But sorry, I can’t really answer your question, that would be a crystal ball raising on that one.
Dane: All right. Thank you very much, Rick. Let’s see here. Next question is, what is the estimated plume size limitations on controlling the injection to get effective treatment in a fine to coarse sand aquifer?
Rick: I’m not quite sure I understand the question, but if you, you know, heterogeneity, this is in general. This just isn’t what PlumeStop or any…this isn’t what reagent. It’s heterogeneity always controls the success usually of an injection. And there are some things we can do to overcome heterogeneity but in a lot of cases, heterogeneity is something we have to deal with. And that comes down to pressures, flow rates, number of injection points as well as…by that I mean vertically and laterally. A lot of times, vertical injection points are overlooked. We see a lot of times where people are trying to inject over 10 feet and use one injection point to cover a 10-foot vertical.
In our opinion, we like to break that down. The most we like to inject over vertically is two to three feet and use multiple points vertically. Once again, you can get in discussions both top-down versus bottoms-up versus different types of tools. It gets quite complex. At the end of the day, your applicator should be able to help you, advise you on which best way of doing that. And of course, that comes down to detailed site assessment is a lot of times this one to two-inch sand seems coarser and they may be just one or two orders made to a higher hydraulic connectivity. They will control where things go in the sub-sources. So those are the things that really we find when we have better characterization of sites by the consultants, we get better treatment. It really comes down to that.
Dane: Okay, great. Thank you very much, Rick. Let’s see here. Next question is, “When you collect groundwater samples from monitoring wells in the midst of the PlumeStop injection area, what do you see in the water? Do you see any of the black PlumeStop carbon suspended in the water?”
Rick: Yes. Definitely after the short-term, if we try to sample two or three weeks after, we’ll definitely see. We did try to sample I think about three weeks after we did the injection. And we just had PlumeStop was definitely suspended in some of the wells. Discussing with the lab, that was gonna be a major issue. So, we decided not to submit those samples and we waited till three months, and by then, all the PlumeStop had basically been removed from the groundwater and that groundwater was basically back to its natural turbidity, for lack of a better word. So, in this case, we’ve never tried to analyze any of the samples immediately after or shortly after the PlumeStop is because the water itself can sometimes be quite gray or in some cases black. In which case, that causes some issues with the laboratory.
Dane: Okay, great. All right. Thanks very much. Let’s see. We still have some time for some more questions here. So, next question is, “What other types of sites has PlumeStop been used on? Have they all been PFAS-contaminated?”
Rick: Just speaking for us up here in Canada for InSitu, this is the first site that we know of that’s being had PFAS. So that’s the only one up there…I think we’ve did about 23 sites now. The other sites have been a mixture of chlorinated solvents and petroleum hydrocarbons. I would say maybe 60% petroleum hydrocarbons, 40% chlorinated solvents. The geologies we’ve injected PlumeStop in is anything from a glacial till to glacial fluvial deposits and that sort of thing and even fractured limestone and metamorphic rocks. So, we’ve got quite a bit experience and it’s worked quite well in quite a wide variety of geology. So, you know, the nice thing and I don’t like to keep going back to it, but what I call the injectability of this product is it’s a very easy product to inject. So, I mean, from that point of view, I don’t mean to make it sound simple, but that is one of our biggest challenges injecting products is how well does it go into the ground? And then once it goes in the ground, how well does it distribute? And in this case, I hope we find this product actually distributes very well in the ground and injects very well easily into a variety of geologies.
Maureen: Just one comment I wanna add and it’s a question that came up and it was when you’re talking about the PlumeStop getting into the wells. It is a common practice say after the application to flush the wells and to remove some of the carbon in the wells. I don’t know if you wanna comment on that, Rick, but I know that’s a common practice that we utilize.
Rick: Yeah. At this site, we did do a small flush afterwards, and that’s one reason why we left it for three months. The flush we find also for the ORC because it also can…I don’t wanna say clog up the wells but it can clog up the wells if it gets in the well. So we try to flush it right afterwards but we’re not talking, in this case, we usually talk maybe two to three gallons at most, and we put a tracer. Before anybody asks, we put a tracer into our water that we flush out the well so that when we sample, we analyze for that tracer to make sure we’re just not sampling water that we injected to flush out the well. So we know the water we sample is aquifer formation water. So, to answer that question before it gets asked.
Dane: All right. Well, thank you very much, Rick, and thank you, Maureen. That’s gonna be the end of the chat questions. We’re out of time. So, if we did not get to your question, someone will make an effort to follow up with you. If you would like more information about environmental remediation services from IRSL, please visit irsl.ca. And if you need immediate assistance with the remediation solution from REGENESIS, please visit regenesis.com to find your local technical representative and they will be happy to speak with you. Thanks again to Rick McGregor and Maureen Dooley. And thanks to everyone who could join us. Have a great day.