Dr. Jeremy Birnstingl, VP of Environmental Technology at REGENESIS, provides an overview of PlumeStop® Liquid Activated Carbon™, a new in situ groundwater remediation technology that rapidly reduces contaminant concentrations (in days) and accelerates biodegradation. This is part 2 in our webinar series about PlumeStop. Dr. Birnstingl covers the basic theory behind the technology and relevance to the field of bioremediation. The majority of presentation, however, relates the latest data from the lab and field regarding PlumeStop’s ability to secure contaminant sorption and biodegradation.
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Today’s webinar will discuss reducing groundwater contaminants in days with PlumeStop Liquid Activated Carbon. With that, I’d like to introduce our presenter for today. We are pleased to have with us Dr. Jeremy Birnstingl, Vice President of Environmental Technology here at REGENESIS. Dr. Birnstingl holds a PhD in bioremediation, with 25 years professional experience in the remediation sector. He directs the worldwide technology development, and acquisition efforts of REGENESIS, overseeing new product commercialization efforts and operating as a senior technical director on key remediation projects involving advanced institute technologies. Before taking on his present global role, Dr. Birnstingl served as the Founding Managing Director of REGENESIS in Europe, responsible for establishing technical and administrative teams across the continent within multiple legislative regimes and operating currencies. And that concludes our introduction, so now I will hand things over to Jeremy to get us started.
Jeremy: Thanks very much, Dane, and thank you, everybody for joining us.
So this is the second webinar that we’ve put out on PlumeStop, PlumeStop being a technology that we brought to market just over a year ago after about five years development in-house. The first webinar is still available online, and we’ll deal with more of this theory and some of the background science, which is also in the white paper on the technology. This webinar will deal with some of the theory as a quick overview, but is going to segue from some more sections on additional lab information, through to what’s being going on in the field over the last year or so, which is the principal part of the webinar.Click Here To Read Full Transcript
So the first thing I’d like to say about PlumeStop is what was it for? Well, really, REGENESIS has worked with bioremediation for 20, 21 years or more. And we were looking at what we could actually do to take bio up to the next step. There’s plenty of electoral donors on the market now and acceptors, and our own offerings have been refined and developed over the years, and that wasn’t really necessary. The question now about bio is what was really necessary to take it the next step? And if you think bio, there are probably two perennial challenges that it’s had, and I’m saying this as a long-term fan of bioremediation as my principal specialty. Its challenges are time, it’s still slow technology, despite all of its benefits. And to some extent, end point uncertainty. It’s not always clear exactly what level it’s gonna be possible to get to with bio before things start to slow down. So PlumeStop was really developed as a way of overcoming both of these challenges. And with that, it gives us up-front orders of magnitude reduction and accelerates bio-destruction. So enough of the intro.
What are the principal features of PlumeStop technology? Well, this is really what it brings to the party. It will provide a rapid reduction of ground water concentrations, which are typically multiple orders of magnitude. And these can be achieved in days or weeks. I’m saying days or weeks, because the first sampling intervals are normally in days or weeks, but the actual immediate reduction in ground water concentration is very, very fast.
It will accelerate the degradation of contaminants. This will eliminate low concentration performance tailing that can sometimes take place, asymptotes that can follow initially good degradation. And it will provide an ability to secure very stringent clean-up targets. These will be clean-up targets in the low part per billion, the low microgram per liter range. Not relevant on every site, but on the sites where it’s relevant, these could be tough targets to reach.
The material can be dispersed widely in the subsurface for injection. The wide dispersion allows for efficient fieldwork. This is dispersion at low pressure rather than fracture emplacement, wide dispersive application. This would provide efficient fieldwork, and also enable the technology to reach areas of restricted access such as buildings or in deep plumes with a minimum number of drilling points, etc, etc. And interestingly, the reagent itself is not consumed, it regenerates in situ. So it’s there, essentially, like a catalyst. So it would help take the reactions forward, but without actually taking part in the reaction itself in a manner in which it would be consumed. It’s not consumed, it regenerates in situ.
So the basis of PlumeStop is this, what it actually comprises in qualitative terms is a highly dispersive, injectable solvent in microbial growth matrix. The solvent and growth matrix is the same thing. These are two aspects of the same material rather than two different materials. The solvent is what achieves the rapid drop in dissolved-phase concentrations, and through that, immediate risk reduction. There’s no contaminant destruction going on here. This is simply at this stage, taking the contaminants out of the mobile phase, out of the groundwater, and hence, actually dropping vapor concentrations as well through Henry’s law, and taking them onto material itself, on the material which then acts as a microbial growth matrix. There is an accelerated bio-destruction of the mass which is sorbed, and an ability secured to get to much lower clean-up targets. So this isn’t quite strong assertions. The sorption can easily understood, but accelerated bio-destruction and much lower targets, well, how do these work? Well, I’ll spend a couple of minutes going through the core theory of that before I get into some more of the performance information.
So a few basics on bio-availability and threshold concentrations for any folks listening who are not microbiologists by training. So microbiology 101 is this, bacteria live on surfaces, they live in biofilms, at least the ones which do the degradation work do. So think plughole slime or dental plaque rather than little tadpoles swimming around in the ground water. The bacteria grow in films, the micrograph is dental plaque for those who are interested and a very good reason to clean our teeth in the morning.
Because they’re sessile, because they don’t move, they have to wait for their growth substrate, their food, to come to them. They don’t go out hunting. So this means they either have to sit on or in their food sources, as they would with rotting vegetables, for example, or they have to wait for their food, the contaminant that we want destroyed, to dissolve and come to them in solution. This is what happens with bio-remediation.
So following this through, what this really means is that as the plume is progressively cleaned up, the contaminant concentration drops. That’s what remediation is. And because the contamination concentration is dropping, the rate that the food, the substrate that’s coming to the bacteria also reduces. And so the rate they can degrade at also reduces. This is the mathematical principle of first order kinetics, so the half‐life degradations that we often see. And in principle, it applies to anything that involves the collision between reacting species, whether it’s a bacterium in its food, or it’s an oxidant and something that’s being oxidized. The same principles apply. As the concentrations drop, the instantaneous disruption rate slows.
It goes further, however, at least it does in microbiology. Below a certain concentration, the rate can slow dramatically. There are threshold concentrations, the for microbial growth. This is the concentration where there will be sufficient energy for the bacterium to become active, and for its enzymes to be actually induced, below which there’ll be a starvation boundary of which the substrates are just not degrading anymore. The bacterium is not active with that contaminant. This threshold is variable, but would typically be in the low microgram per liter range, so not relevant for every site, but certainly relevant on the ones which are chasing the numbers down to very low levels. And this step change slowdown is in addition to the first-order diminishing returns that I described previously.
So to put a fairly complex slide into an easier illustration, here’s a hypothetical contaminant which is degrading with a half-life of seven days. So this is the typical destruction curve that we might see in rougher forms on various projects. And what this really means is that with a half-life of seven days, up to one week, half of it is gone. So in this case 6,000 micrograms per liter is removed in the first week, way to go. In the next week, half of it is gone, but now it’s only 3,000 micrograms per liter. Week three, half of it is gone, 1,500. Week four, half of it is gone. Now only 750 micrograms per liter. So now, this is something like 12 and a half percent of the initial weekly mass removal.
So here in concept, what would it be like if the linear rate that we can get at the top end could continue at the lower concentration? What would it be like if we could get the mass destruction that we can see in the early stages to continue at the same rate at the later stages essentially extrapolating the line down? This would be the general idea, we get to the clean-up to much lower clean-up targets faster, although in practice, the top end would also be accelerated. I’m gonna come back to this slide perhaps a little bit later.
So to achieve this, what the reagents, the PlumeStop reagent actually is is a colloidal activated carbon. The particles are one to two microns in size, so about the size of a blood cellar or bacterium. They suspend easily as a liquid. It’s, I think, one of the reasons that bacteria…it’s no coincidence that bacteria and blood cells are about one micron. Mathematically, this is an ideal size for colloidal distribution. At this type of particle size, not only is the activated carbon, well, activate with a high surface area, but because the particle sizes are very small, there is a huge exposed surface areas, the absorption can be very quick.
This isn’t the point, however. The real key to creating the PlumeStop technology is the proprietary anti-clumping and distribution supporting surface treatment that we worked on for years to secure. This is the core innovation in PlumeStop that enables its dispersion without requiring fracture emplacement, and to move freely at low pressure and coat the formation. This enables wide area, low pressure distribution without clogging. That’s the very core of the technology. We’ll see the difference it makes in a few slide’s time. It also contains some low solubility and controlled availability matrix nutrients which help support the in-matrix contaminant biodegradation so aren’t released into the groundwater itself. So they don’t add to eutrophication, greening of the water bodies etc, etc.
The basic concept then is this. Here is an injection rod, a direct push rod on the right that’s been pushed into the formation, and PlumeStop is being injected dispersively out. And it’s important that it moves dispersively. This image, for example, is an image of fracture-emplaced powdered activated carbon. And if you look at it carefully, you can see how this pure carbon here, it has forced the sand or forced the solo particles apart. The carbon is still in its own discrete layer, and it’s relatively thin. If you look at the scale of the fingers of the person holding it, then we’re at a quarter of an inch, maybe an eighth of an inch or so there.
This is not what we’re trying to do with PlumeStop. The dispersive treatment that we secure with PlumeStop is qualitatively different. Here is some dispersively-emplaced PlumeStop, and if you look carefully at this image you can see that the PlumeStop has moved around the sand particles rather than forcing them apart. So you can see the sand particles here with the PlumeStop around them. There’s a qualitatively difference from the factory-emplaced material. And the reason this is important is that the monitoring world that we’ve got here is monitoring the full body of impacted formation. If we had a fracture that had been moving out from this injection point and hitting the well, then the well itself might have filled with carbon and showing some great results. The fracture contact of the formation would have been relatively low, and the total body of water actually contacted in the subsurface would be lower. So dispersion emplacement makes a qualitative difference here.
Zooming in on the soil particles, what we can see here are the coatings of PlumeStop, and this cutting schematic, and growing on in-between the PlumeStop particles are the bacteria that would colonize, which is the growth matrix. The particles in real life or at least with electro micrograph would look something like this. You can see the sand particles, which is the larger boulders and the coating on the surface of the particles of PlumeStop roundabout one to two microns in size.
Then the concept behind its use then is fairly simple. It’s injected into the ground, it provides a wide distribution. Contaminants are then absorbed onto its surface. Biofilms would grow as it’s colonized. The degradation will be accelerated. We showed the concept earlier, I’ll show you some data in a little while. And because the contaminants are being degraded on the surface of the material, the sorption sites can become regenerated so that as more contaminant flows into contact with the material, it can be captured either from influx, the migrating plume treatment or from back diffusion as it’s coming out of the secondary porosity, it can get captured on the PlumeStop that’s dispersed through the primary process here. And so we can go around the wheel multiple times.
An example I’ve used then. Here’s a mixed solvent site in the Midwest. It’s a former electronics facility. And this was one of the early beta tests when we took PlumeStop out of the lab and started to test it in the field. It’s an electronics facility. We’ve got modest concentrations of chlorinated ethenes and ethanes. We’re in a sand to a silty-sand, fairly forgiving formation. Depths of groundwater is about 10 to 13 feet, about 12 feet seepage velocity a year. And the application was PlumeStop and electron donor HRC, which is very compatible for use with PlumeStop.
This is what the data looked like heading up to the application. We can see the TCA as the blue line at the top, and the TCE is the next line down in the middle. And then we can see a number of daughter products below showing that there was some type of attenuation going on before. When we applied the PlumeStop, concentrations dropped something like this. Now, to put numbers to that, in a general sense, we got one order of magnitude reduction by the first sampling interval, it’s two weeks, two orders of magnitude reduction by the second sampling interval, three orders of magnitude reduction by the third sampling interval. And at six months, we were at non-detect, which I think is about five micrograms per liter on this site. I think it was something like that. A lot lower than the numbers that you can see here.
What’s particularly interesting though is that with the microbial diagnostics that we were following this with, we saw a proliferation of the VOC-degrading microflora even at this point. So once the concentrations are at or close to non-detect, so they’re in a very low microgram per liter range, we’re still seeing dehalococcoides growing actively. Something like an 800% growth, we were still seeing with the groundwater concentrations below detection limits. Now, considering that dehalococcoides is an obligate solvent degrader or a chlorinated ethane degrader, it’s growing on something. It must be growing on solvent, and there’s no solvent in the groundwater. So this really provides a reasonable line of evidence, one line of evidence at least that the destruction and the degradation is still taking place, even though it’s not taking place in the groundwater, but on the PlumeStop itself.
What adds further lines of evidence is that after about 250 days, we reached a point where the influx with the flow rates and the concentrations that we were seeing over here would have reached the equilibrium saturation with the PlumeStop. We would have started to see the concentrations beginning to climb again. We didn’t. And after one year, we still didn’t. And after 18 months and counting, we still haven’t. So the amount of mass that’s flowing into the zone based on the background trends and what’s happening upgrading is greater than the sorptive capacity of the PlumeStop, yet we’re still seeing nothing in the solution. But we are seeing a proliferation of VOC-degrading bacteria in the groundwater. The inference is that the degradation and the regeneration is going on on the material itself. We’ll show some lab data too, on this.
Now, I mentioned earlier that distribution of the material was key, so let me show some illustrations of what the movement of the material is actually like. The first site I’d like to show are a comparison of distribution of powdered activated carbon and PlumeStop through some of the column. So the difference here is principally the dispersive treatments that we put on the materials with PlumeStop. And it looks something like this. PlumeStop on one side, activated carbon on the other. This is gravity feed, equal volumes of water, equal volumes of carbon. I’m gonna run that through, again. Equal volumes of PlumeStop, equal volumes of carbon. This is slightly accelerated. The total run time was about 12 minutes, as I recall. And surrounded by gravity feed were three pore volumes of water that went through that. You can see that the PlumeStop has moved dispersively through between the sand particles. The activated carbon on the right has just clamped up and clogged at the top.
Looking at the sand particles, the difference is also reasonably evident. These are the sand particles without PlumeStop. The scale bar at the bottom is about 50 microns. And this is what the sand particles look like with PlumeStop coating. The scale bar is now about 20 microns, so you can see the actual PlumeStop particles coat in the surface are about one to two microns in size. Here’s another illustration from another micrograph. There were quite a lot of micrographs in this. This is an illustration of what a biofilm might look like. These aren’t biofilms growing on PlumeStop but that’s a given idea, conceptually of what we would start to get growing between and on the particles here. The scale bars here are about half a micron.
So all very well, if we’re pushing PlumeStop or allowing PlumeStop to gravity feeds for a two-foot column, what about some field practical distances? Well, this is a setup in our lab in Southern California, again. The column is 16 feet in length, we’ve got a fine to medium sand, core volume of perhaps half a gallon, and we’re looking at this. It’s a retained breakthrough dynamics and retained carbon mass balance. It’s an outflow column, we’re pumping the water up through the column and it gets collected in the second vessel here.
It looks something like this. Let me see if I can make this animation run. I’m gonna pull it up. Here we go. Here’s some material going up. Depending on your screen refresh rate, you may or may not see it. Hit’s the top, should really ring a bell. And now we can see the material passing through the column into the next. There’s a third pore volume going through. Fourth pore volume now switching to clean water, and the clean water soon starts to break through. Fifth pore volume, there we go, it’s coming out clean.
Now, in case you couldn’t see that on your screen, it looks something like this. We could see the front progressing through dispersive flow. There’s no fracture or fingering here, it’s moving up very smoothly through dispersive flow. About 80 minutes, it’s filling the column. And when it’s water flushed, there’s a slight residual coating but still visibly apparent. In the field, whether or not we will water flush would depend on the type of PlumeStop delivery to the formation that we want, and how soon the coating should be, or whether we want to put more material in the formation. There’s different ways we can control.
The breakthrough dynamics looked something like this. This is the effluent concentration divided by the influent concentration. What we can see here in the PlumesStop application period is that we got breakthrough at about 1.2 pore volume, so over 16 feet, the PlumeStop was about 20% water front. So it’s moving through very freely. And what’s also important is that the material that’s coming through at the top would have traveled through 16 feet of column and it’s still going. So if it could go 16 feet, it could probably go 17, 18, 19, 20. Here’s the clean chase-water dropping the effluent concentration back to the original.
What was also interesting though is that back pressure was pretty much the same before and after the flow had been…the PlumeStop had been pushed through, which suggests that we’re getting a nice thin coating, and we’re not actually blocking the formation. This is important for any type of barrier application where we don’t want to interrupt groundwater flow and push it around the barrier. We want the groundwater flow to go through the barrier and leave the PlumeStop behind.
What about wash-out? If it moves so freely, isn’t it gonna wash out as well? Well, we put nine pore volumes of chase-water initially…immediately behind the PlumeStop through this column. Dispersive treatment was still reactive through this phase, it’ll be active for about one to three months from the time of application. So the PlumeStop would readily move.
This would be an equivalent seepage velocity of about 22 miles a year, which is completely unfeasible for natural groundwater conditions. But it gives an idea of just how aggressive this chase-water flush was. We then broke the column into lengths, and we analyzed it for elemental carbon, correcting against the clean sand pre-application baseline. What we saw was something like this, reasonable amount of carbon. The different heights of the column reasonably evenly placed. Total less retained was in the column, is less than 1% of the pore volume. This is the one to two micron coatings of the same particles as we’ve seen before.
So even on a low surface charged material like the sand, the PlumeStop will pass freely, but will leave a coating that is very strongly retained. And this is an important placement feature. The wash-out flux was much greater than we typically see in field work conditions. And in the field, there are a whole range of opportunities for the way that the quantity at which we place the material and the formation. We can change volume, flow rate, dilution, chase-water use, chase-water volume, injection spacing. But we can also adjust the dispersion treatment by using counter reagents. And that’s one of the reasons why at the present time, we apply the material ourselves as REGENESIS as its own key package so that we can carefully control the application work directly and ensure that the placements is where we need it.
A few slides, landslides on bio-regeneration, then I’m gonna move through to case studies. So the principle bio-regeneration concept is this. We will have the contaminants sorbing onto the sites, which are available of the PlumeStop particle. The bacteria then degrades the soil contaminants, and the sorption sites become available for additional contaminants. So to give an illustration of the proof of concept here, this is a microcosm study. We’ve got some vials. In these, we have water, lactate, soil and PlumeStop plus an Inoculum. In the control, it’s the same except they’re still sterilized and, of course, we don’t bother to put the Inoculum in and then kill it. We have equal volumes, no headspace, 27 reps and about 10 milligrams per liter of PCE that we had every two weeks. Study period is 10 weeks, and we look at the dissolved phase analysis and the total system analysis with water and the soil combined.
This is what we see in the dissolved phase. Let me make it a little bit clearer. The blue line is the control system where we have PCE concentrations in water, and it’s sterile, and so the concentrations climb pretty much on each injection. In the PlumeStop treatment, the PCE that’s added is captured each time the aqueous space is essentially protected, and the concentrations do not climb. Now, to clarify this a little further, this green line would be the theoretical aqueous space concentrations if there’d been no sorption whatsoever. So this is just the spikes 10 PPM, spike mass to get 10 PPM in solution each time. So what this is really showing us is that this would be the sorption onto the soil, and this would be the sorption onto the soil in the PlumeStop.
Now, the amount of PlumeStop that was put in was very small. We’re exploring boundary conditions here rather than putting enormous amounts of PlumeStop with a lot of sorpted headroom. And so theoretically, we would have been saturating the PlumeStop pretty much at the first injection so that after each injection, we’d be getting the concentrations starting to mount up. They didn’t. And so bottom end here, this is the first illustrations of the bio-regenerated capacity, but this is just the dissolved phase.
If we look at sorbed phase here, so this scale is now in milligrams, there’s nowhere for the contaminant to hide at all. So what we put in is what we see. And we can see that the total mass in the sterile system climbs with each injection. Within the PlumeStop system, it drops back to baseline between each spike. And as I said, there’s nowhere for the PCE that we put in to hide. What’s happening is it’s being put into the system, and then by the time the next spike comes round, it’s degraded to or close to zero. Then it grows again and degrades again, grows again and degrades again. As we are at the sorptive capacity, we’re not just sorbing some more available sites. There has to be a regeneration of the sites for this to occur with the amount of carbon that we’ve actually got in the system. So there is a reasonable illustration of sorptive bio-regeneration.
I think in the interest of time, I’m gonna skip through to the case studies rather than talking about the bio-acceleration. Bio-acceleration, we dealt with in the previous webinar, and it’s there to be listened to. There are also some tech bulletins and information in the white paper. So in the interest of time, I’m gonna move forward to some case studies.
So this is another indication of bio from the field. This is also one of our beta tests, so we got a reasonably good body of data and lines of evidence on this. We’re looking at post-sorptive degradation in the field and lines of evidence for this. So to put this in context, biodegradation is typically monitored in the dissolved phase. Lines of evidence approach might be used to minimize but provides a very good background in this from a number of years ago. And many of us, of course, would be familiar with these principles.
With PlumeStop, sorption precedes degradation, so contaminants and daughter products often drop below detection limits. And so what verification lines of evidence remain open to confirm the degradation is proceeding? So this is a case study example of some of the geotechnical and microbial diagnostics that can give us some indication of what might be happening. It’s a California site, nice blue sky. It’s a pilot test around a single well. It’s a former drycleaners, and we’re in modest microgram per liter levels of the PCE residue.
Here’s the well. We’re in a dune sand formation. About 30 feet a year seepage velocity, high redox conditions, it’s aerobic and no attenuation evidence at all. We have PCE at about half a milligram per liter, we have no daughter products, we’re applying PlumeStop and electron donor and bacteria. Here’s the test well and a very simple grid around it. This would not be a typical remediation project, this is a beta test, so it’s lab essentially going into the field to test principles. Groundwater seepage is 33 feet a year in this direction, and these are the materials that we’re applying. Historic data looks something like this, going back for more than a decade. And what you’ll notice is a steady increase if anything in PCE and no daughter products present. The conditions are aerobic so…in fact there’s no degradation. It’s not a surprise.
This is what the same data look plotted out. Look like plotted out. The application was in early 2014, and by the first sampling interval, we’re down detection limits. So we’ve got three nines reduction in the field from this. So all well and good for sorption. How do we know it’s degrading? Well, here’s a graph. Let me just explain that the second axis for the geochem parameters is zero, it’s up in the middle. So if the lines look like they’re not going down below a certain point, they are. They’re hitting zero or going below. What we can see here is the PlumeStop application at time zero, and we can see the redox sweet spot establishing here roundabout -150 millivolts. Great for dehalorespiration, not good for methanogenesis. And we’re seeing the competing terminal electron acceptors like sulfate, dissolved oxygen etc., slowly declining to quantities that wouldn’t interfere with the solvent degradation. So we’re in a good place for the biodegradation here.
When we look at the contaminant concentrations, and the microbial counts, here’s the application. We can see that the PCE, the red line immediately drops down to detection limits. Five micrograms per liter for the first two sampling rounds, and then after 30 days, I think it drops down to half a microgram per liter and still won’t detect. What’s interesting though is what’s happening with the microbial trends. Dehalococcoides immediately shot up on application. Not surprising, we’re inoculated, so that’s how Inoculum going into the ground. But also, post-inoculation, it increases significantly and continue to rise and more than double over the next two months. So we’ve got something like 225% increase in dehalococcoides post-application. This is suggestive that we’re getting some type of growth, at least based on this data.
Also interesting is that the tceA reductase and dehalococcoides and the vinyl chloride reductase, these are both dehalococcoides enzymes, the solvent degradation increasing in activity post-application by some six, seven-fold. So not only is the microbial growing…the micro growing, but the number of active genes is increasing significantly. Also of note, the dehalobacter, which was originally non-detect, has shot up over time. And interestingly so, dehalogenimonas increased. So these weren’t in the inoculum, these were growing purely through biostimulation. The methanogens meanwhile, this line along the bottom did stay, basically at background. Redox wasn’t low enough for them to start to grow, but it was perfect for the dechlorinators to flourish. We carried on monitoring. We’re now at some 451 days, 15 months. We’ve been below detection limits through seven consecutive sampling rounds, about half a microgram per liter and below. I don’t want to dwell too much on this, because I’ve mentioned most of it. So in fact, let me just go back a slide and use one of my shortcuts, go to some more case studies.
Okay. So here are a few quick-fire commercial projects before we go onto Q&A. These don’t typically have the same data that we would have in the pilot studies, because, well, it’s not always necessary to have so much data. This is a pilot study for PAH treatment in Richmond, Indiana. It’s an old gas work site. We’ve got a silty clay loam transitioning to sand and grovel, globules of oil-like material in the pore space, injection 12 to 18 feet, something like that. PlumeStop and ORC-Advanced applied on this one. This is what the data looked like prior to PlumeStop application. Low concentrations in this particular test well. Post-application, they’re not right down. These are showing…the grafts values are shown there, or the reporting limits rather than the actual, because they’re below reporting limits. So the average reduction in dissolved phase by the first sampling application was on average 95%, so they’re more than an order of magnitude. And all of the post-treatment concentrations were below the risc default residential, and/or below half a microgram per liter.
Another quick fire one. This is in North Carolina. It’s a migrating solvent plume, it’s a barrier application. Former industrial drycleaner, PCE residues, pilot barriers for a complex formation. We’re looking at multiple targeted zones between about 9 and 41 feet below grade. We’re in a silty sand, seepage velocity about 73 feet a year. And to this treatment, we’ve applied HRC, and inoculum. So electron donor and inoculum and PlumeStop. This is what the data have looked like post-application. We had something like 99.7% reduction and 94.2% reduction in the application zone. What I think is interesting here, and I’m showing you an insight from a completely different site. This is a German site, it’s not the North Carolina site.
What is interesting to see is that given that these are the typical bio-trends that we would normally see with PCE dropping down, TCE increasing then dropping down, [inaudible 00;39:54] increasing more significantly and dropping down, and then maybe a bit of a final climbing period and dropping down, we’re seeing exactly the same patterns going on when we’re at the boundary of the sorption conditions. The qualitative balance of compounds has changed significantly here, and yet this is principally taking place active solution. This is one of those interesting sites where the boundary of sorption is in this particular area, and we can see a little bit of what’s going on with the bio under the bonnet.
This is the down gradients of the PlumeStop injection. We’re right on the lateral periphery, so there’s probably some flow coming round the treatment zone. The reductions are not significant here, but there would be some flow time we expect, you know, things to change. The reason I’m showing this slide is because it’s showing the…despite the mobility of the PlumeStop, it’s not as if we’re capturing a lot of contaminant and then flooding it down to other wells and mobilizing it. Neither are we actually displacing the plume. So here we’re very close to the application lateral periphery, but the concentrations are still going down. There’s no displacement.
When we’re getting closer to the center line, this is 30 foot down gradient and this is one of the deeper intermediate formations. There is the PlumeStop application which was up gradient and down gradient. Possibly over the next few months, we’re seeing some of the reduction and the flow. This is not material that would have gone through the barrier, because they’re not within the right type of seepage time. This is the material that was already behind the barrier, but now the barrier is in place, there’s already some type of drop going on. And, again, this is 30 feet down gradient in the shallow formation as the PlumeStop application, and down gradient to the barriers, the material that’s already passed I already starting to drop down that’s not being replenished from up gradient.
Deep plume treatment up in Wisconsin. Former drycleaners, PCE residues. The shallow material was done through soil mixing using institute chemical oxidation and RegenOx concentrations down. The deep plume was treated with PlumeStop, where the concentrations were much lower, and, again, we got some quite striking reductions through some modest concentrations. So 98, 99, 99 point something percent reduction from the first applications.
Running short of time. This one is in Pennsylvania, It’s a filling station with BTEX residues. This isn’t the actual filling station, it’s just an old filling station. We have BTEX residues. It’s a pilot application. It’s a very tight formation. We’re applying between about 9 and 15 feet below grade. The material was locked as a clay with some sand in. So the hydraulic conductivity would have been something like 10 to the -7 centimeters per second. That would normally preclude PlumeStop treatments. We won’t to be able to dispersively move the material. But REGENESIS field services went right onto the site to do some feasibility tests and found that there were sand lenses which were able to take a majority of the flow, and probably the contaminant was moving through. It’s into these that the PlumeStop was principally pushed as I understand it. In those spaces, they would also be able to capture any back-diffusing material coming out of the lower [inaudible 00:43:32] zones. ORC was applied with PlumeStop.
Background concentrations are showing for the first three lines. The post-application concentrations are showing thereafter. We’ve got something like 98.3% reduction in total BTEX with the TEX components all less than half a microgram per liter. Benzene is there at four micrograms per liter in this particular one. This is relatively recent data.
And last one I wanna show you in this quick-fire is in downtown Chicago. This is one of the larger applications, and I think is a particularly interesting one because it’s a case where a bio-project supported by PlumeStop was selected over chemical oxidation, partly on the interest of time and getting faster results. I think that’s probably one of the first examples of bio being selected over ISCO on time.
It’s an inner-city development, it’s in the neighborhood of McCormick Place in Central Chicago near the lake. There’s a new sports stadium, a new hotel complex going in. Now, for anyone who’s been involved in development projects, there’s always time pressure, but for sports stadia, you have to book the sports teams into them and want people in them about the time they open. You’ve gotta book way ahead and do so for hotels, so slippage on the timeline is not welcome. We know about this in the UK from building on the Olympic site on brownfield land and having to make the date. Happily, some of our products were used on that project as well.
There are solvent residues, a very tight time window and high cost implications of delay. So the key requirement is fast. Now, this was as I mentioned, being considered for sulfate project. All well and good, we’re very happy with that, we the sulfate materials too. But one of the concerns was that if…not only do chemical oxidation projects tend to rebound more than bio-projects reference, Travis McGuire work on all of that, but the degradation, the destruction will still take some time, and any dewaterings, or any excavations are likely gonna be finding chemical oxidation residues and chemical oxidation products there. And any dewatering activities are gonna have to deal with this. With PlumeStop, the chemical…the contaminant removal is fast, it’s right up front, but secondly, the water is now gonna be clean to extract and requirement for additional treatments and the risk of worker exposure in [inaudible 00:46:20] water excavations is gonna be much lower. So we’ve got time and we’ve got safety benefits in here that are coming through.
So why the tight time window? Weren’t the solvent residues known? Well, there were access restrictions through historic buildings. These precluded an early start. A number of them could be demolished, other ones couldn’t. And some of the ones which couldn’t be demolished were simply moved aside. So if that’s something you’re considering for your project where buildings are on the way, the price tag on that was something like 6 million, according to the Chicago Tribune.
So we had PCE and TCE residues up to about seven and a half milligrams per kilogram, sand over clay, about 1,000 times 1,600 foot treatment area, and we were treating between 10 to 22 feet between ground surface. We were putting in enough electron donor and inoculum to deal with all of the contamination in its own right. So this is…under the bonnet, this is a bio-project. Incidentally, the image that we can see there would have the Chicago skyline in the background if those buildings weren’t in the way. Too bad. The famous Chicago skyline. That of course is Chicago skyline too.
PlumeStop was added though to provide a rapid risk reduction upfront and to accelerate the bio process as well. So essentially, what we’re doing here in situ is taking the bio process out of the groundwater phase so the immediate risk reduction is gone. We’ve got the clean-up and any excavations or dewaterings are going to be that much safer. The project was done with about 19 days fieldwork on site through the Chicago winter, and last year’s was a doozy, as you all know, so well done team for that. About 138 direct push injections, no resident equipment on site.
Results look something like this. Here’s the application. We had more than an order of magnitude reduction from the first sampling interval, 96.9. These gaps are really where there were access restrictions and site works were ongoing. If we drill more deeply into this data, this is just an expanded graph. What’s interesting is that we can see the compositional changes and the boundary conditions moving forward. So we have principally parent product with a little bit of daughter. Almost equal parent and daughter, and then much more daughter than parent. Tiny bit of vynyl chloride showing close to the protection limits here, both indications of the bio proceeding under the bonnet. And these were the clean-up levels. These were secured by the third sampling round.
Now, further over on the site, let’s choose one of the wells that didn’t perform as well, to give an indication. These concentrations are much lower. Again, we can see the changes in composition as the degradation proceeds shifting from parent compound dominance to daughter compound dominance, and then that’s slowly disappearing, too. The bars look high up because the scale is much lower. We’re still comfortably below the clean-up targets, so total VOC clean-up target is up here at about half a milligram per liter, and the TCE target is down 242. So we’re comfortably below those by May.
Status, my last update. Well, this is as it stood from June. Was a rapid reduction in groundwater concentrations, 80 to 97% from the first sampling interval. We’ve got bio conditions established for good degradation, and we’re seeing parent/daughter compound ratio shifts. Targets were met by the third sampling interval across the site, and the sites being positions for closure as of June 2015.
Usage indicators, a few seconds before I move to close. Typically, then, when would we recommend the use of PlumeStop? Clients come to us with particular contamination scenarios. Well, one of the indicators would be when time is critical, and another would be when the clean-up targets that need to be secured are very low. The more PlumeStop we can put in, the easier it is to get to lower targets very quickly. It can be used for the passive control of migrating contamination. For this one, the clue is in the name, Plume and Stop. It can also be used as a long-term means of addressing matrix back-diffusion, which I think is a particularly interesting feature, and I’m just gonna dwell on that one. This would also be diffusion-driven rebound.
So in simple terms, the way that this would work is that PlumeStop would maintain a concentration gradient out of the immobile porosity because it would have dropped the concentration in the primary porosity, the mobile porosity. So the mobile porosity contamination remains low due to the culture of PlumeStop. Sorption sites become regenerated due to the accelerated in-matrix degradation. And because the product isn’t consumed, and it can remain functional, then it’s gonna be there to…ongoing to capture ongoing back-diffusion.
It would look something like this. Once it’s applied groundwater contaminants would partition into the PlumeStop, mobile porosity concentrations would then decline, or if they’ve already gone down, they remain low. The back-diffusion gradient would be created and sustained. Contamination would continue to diffuse at the mobile porosity where it would get captured in the PlumeStop. Meanwhile, bacteria and the substrate are concentrated together on the PlumeStop surface, biodegradation gets accelerated within the matrix, sorption sites regenerated, which means that more groundwater contaminants can partition into the PlumeStop. And here we have a nice little infinity loop which could continue for as long as the sites are regenerated, which we predict would be for years, perhaps decades.
So PlumeStop, we typically use to increase bioremediation performance, and reduce treatment times, and to achieve very low target concentrations. It would typically be applied with electron donor or electron acceptor technologies as it’s still bio under the bonnet, and the donor or accept or requirements would still be there. But on certain sites, it can be used as a standalone treatment. For example, where the natural donor or acceptor supply is adequate for management of migrating plumes, for back-diffusion management, etc., it’s very interesting to put different parameters to PlumeStop into freight and transport models, and, you know, just what a difference the carbon alone can do when dispersed through the formation.
So we have more information available, a dedicated website plumestop.com, and, of course, regenesis.com. There’s a whitepaper, which provides a lot of the detail of the underlying technology and some of the supporting science. We also have tech bulletins, which drill into various aspects of the materials used. They’ll provide things like isotherms, for example, and the basis of these typical [inaudible 00:53:58] parameters for PlumeStop, and descriptions of how this can be significant in remediation, and different forms of how it may be used, including the back-diffusion management that I mentioned.
I think that is enough for webinar, so with a few minutes left, I am very happy to move to questions. Thank you very much for your attention.
Dane: All right. Thank you, Jeremy. So 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 will 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 will 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, so if we run out of time before we get to your question, someone from REGENESIS will follow up with you after the webinar. Okay, first question, how does the use of PlumeStop affect porosity?
Jeremy: Okay. This would be…another way of us asking this question might be does PlumeStop block or clog the formation? The answer is that it depends how we choose to apply the Plumestop. And it also depends on how fine, and how permeable the formation is. As we saw in the column studies, then if we push chase-water through out of the PlumeStop, we need a coating. And there’s negligible change to the permeability or to the porosity. We’ve got less than 0.1% of the porosity actually occupied. That’s great for a barrier application, for example, or when we don’t wanna change how the PlumeStop’s placed.
If we’re in zones where we actually, like source zones which may have been back to diffusing after a previous treatment and we wanna reduce the flux, then there are different ways that we can load up the concentration and the porosity and potentially reduce the flux through these zones so that there’s no wash-out or contamination. And we can do that with…by varying the concentration, the material that we put in. And we can do that by actually making the material that’s being pushed through these zones drop out of the dispersive form and lock into place using application of counter reagents. There’s a lot of different tunes that we can play with PlumeStop depending on what we’re trying to do. And that’s one of the reasons that at the present time, we’re applying it using REGENESIS remediation services. Long answer to a short question.
Dane: Okay, thank you, Jeremy. Next question is how far does PlumeStop distribute once pumping is stopped?
Jeremy: That will really depend on the seepage velocity and how fast the ground water is moving. The dispersive treatment of PlumeStop declines within a short period of time after application, so over a period of about one to three months, it’ll disappear and be gone. And after that, the material will just be locked into place like colloidal carbon and won’t be moving. So the distance it may move would be the type of seepage distance that you might get in one to three months. If that is…if there’s a concern, if you’re up against a sensitive receptor or a site boundary, then it is possible to use counter reagents that affect the distribution so that we can stop it going past certain points, reusing those as I mentioned in the previous question.
Dane: Okay. All right, thank you, Jeremy. Next question, can PlumeStop work if free product is present, even in small amounts?
Jeremy: The answer is yes, but we would not recommend it because it’s a bit like if you’re dealing with an abstraction system. Yes, you could use an activated carbon filter, but you would probably put an old water interceptor up ahead of that for efficiency grounds. So if there is residual free product, then there are normally better ways of reducing that fast to concentrations where it’s more economical to use the PlumeStop thereafter. So just like you could use a gag filter for capturing free product, you probably wouldn’t want to. You’d use a treatment-trained approach, and use a combination of technologies, or approaches, to get to the clean-up targets with much greater efficiency. So REGENESIS products and technologies are designed to hook together like cabooses, where you can go from free product down to very, very low concentrations with appropriate integration of our technologies. I’ve given a lot of nods towards our remediation services, I’m sort of giving another one here. But the thinking is integrated design rather than magic bullets.
Dane: All right, thanks very much, Jeremy. And that would be the end of our chat questions. If we did not get to your question, a representative from REGENESIS will be contacting you directly via email within the next few days to help you out. If you need immediate assistance, please visit regenesis.com to find your local technical representative, and they will be happy to speak with you. Thanks, again, to our presenter Dr. Birnstingl, and thanks to everyone who could join us. Have a great day.