Cost-Effective Approaches Using Colloidal Zero Valent Iron for In Situ Groundwater Remediation

This fully integrated production facility, combined with John’s deep technical expertise, will fuel our continued growth in bringing the best technologies to the environmental industry. Our partnership with John started several years ago where we worked together on the utilization of micron dispersible iron with our current product lines, including PlumeStop and 3D Microemulsion. Prior to REGENESIS, John served as the president of OnMaterials. His firm specialized in the manufacturing of ZVI products that were used at several hundred product applications across the U.S.

John has a Ph.D. in Materials Science from UC San Diego, and a B.S. in Chemical Engineering from the University of Illinois at Urbana Champaign. He has been awarded several research grants from the U.S. EPA, Department of Energy, and the U.S. Air Force. John currently serves on review panels at the National Institutes of Health that’s responsible for reviewing new environmental technologies. With that as an introduction, John, let me hand the webinar over to you.

John: Okay. Thank you, Rick. I’m honored to be here today at REGENESIS. I’m gonna talk about using colloidal zero iron to accomplish in situ remediation of chlorinated contaminants. So, we’ve been doing this at OnMaterials for about 17 years, and in the last 17 years, I’ve been working with colloidal iron in many forms to try to optimize the material and take it from what was originally commodity material and make it an engineered material for remediation.

So, let’s give you a bit of background here. This might be review for a lot of people, but you know, where did the chlorinated solvents come from in the industry? A common thing is dry cleaners. PCE is used as a cleaning agent in dry cleaners and there’s a lot of spills, unintentional and intentional that have occurred. If you talk about people that do sites investigation, you ask them where the most common place for a PCE spill is at a site is at the back door where people throw stuff out the back door in the past.

That’s just one source of contamination. You know, there’s industrial facilities that use PCE, TCE, 1,1,1-TCA, degreasing in cleaning adhesives, etc. These sites number in the thousands across the country and across the world. There’s also a lot of chlorinated contamination at aerospace and defense installations where they were used to clean planes, weapons, missile silos, etc. So, if you if you look at the universe of chlorinated solvent contamination, you know, there’s several thousands, if not tens of thousand sites across the U.S. and the world.

So, how do we get rid of these chlorinated contaminants? And as you well know, most of these are pretty recalcitrant, the natural attenuation is generally pretty slow, so if you wanna bring your site to closure, you generally have to be aggressive and work on securing a remedial option. There is, you know, more or less three or four general classifications that we can use. One is direct push injection where you use temporary injection points, inject your remediation amendments to the subsurface

You can also use permanent wells, which would be similar to your monitoring wells, which will have a screen section somewhere down in the aquifer that’s contaminated. And, of course, there’s mechanical options, which would be something as simple as excavation or something a little more elegant such as soil mixing where you bring your remediation amendments into contact with your contaminants.

So, why use zero valent iron? You know, what does it have to bring to the table that other approaches don’t have? One thing that’s really interesting about iron is that you can address the contamination through a couple of different mechanisms, and I’ll talk about these more as we go forward, but one of them is chemical reduction, which is actually the direct reaction of the iron with your contaminants in the ground. It’s also called a biotic reaction. Additionally, you can also have enhanced bioremediation. You can also have these things in parallel. And we’ll step through these as we go for forward in the webinar.

One thing that’s really important with ZVI is that when you engineer it and you make it an advanced material, you can use it in a manner which satisfies all the requirements for a successful in situ remediation. And I call these the for cornerstones, and we’ll walk through these as we go forward. In general, with in situ techniques, you’re not gonna have to use excavation, you know, permanent system installs such as favor and extraction systems. Everything happens in the ground, you inject the stop once and the remediation occurs.

So, this is, kind of, the premise of what we try to do when we design remediation amendments. I call these four cornerstones. When we design our project, when we design our materials, you really have to take all four of these in consideration, and if you don’t have success or consider all four of these individually, there’s a pretty good chance that you’re not gonna have success. The first one is reactivity, and that’s what most people consider about when they talk about remedial amendments. Obviously, the material has to react with the TCE or whatever your target contaminant is, but that’s really only one step of the process.

On top of that, if you go down to the bottom, there’s the green little circle there, it’s distribution. And those of you who’ve been in the industry for a while have heard the terminology, “it’s a contact sport.” And that’s really true. You can have the most reactive material in the world, but if it’s not brought into contact with the contaminants, there’s a pretty good chance you’re not gonna have a successful outcome. So when you design your injection event and your materials, you need to take into consideration distribution.

The third cornerstone is in blue there, it’s called persistence or it might be also the called longevity. If you have a reactive material but it doesn’t last very long, it’s not gonna do you a lot of good. You can end up with rebound, etc., and an example might be, you know, hydrogen peroxide, really, really reactive in a bottle, but the half-life might be minutes or hours, and it’s generally not gonna do you a whole lot of good in the long run. And don’t forget about ease of use. You want something that’s easy to use and safe.

So what I’m gonna do now is kind of step through each of the four cornerstones and talk about them a little bit more in particular. So, let’s start off with reactivity. This right here is a little stick diagram showing the chemical formulations of PCE and it’s daughter products all the way down through ethane. Those of you that are familiar with bioremediation know that it’s a sequential process. PCE is reduced to TCE, subsequently reduced to DCE, vinyl, and to ethane. And then, in this case, you basically take one chlorine atom off your molecule and then replace it with a hydrogen molecule.

The one thing that’s really great about iron is that you can actually use a different reduction mechanism that bypasses, or at least largely bypasses, these daughter products. So, what ends up happening is that your parent compounds, which are typically PCE and TCE, are reduced directly to ethane through these chloroacetylene intermediates that you see down here in the bottom. So, for example, PCE is reduced. It’s a two-electron process, just like the bioprocess, to dichloroacetylene, which is the short-lived intermediary. You go to the right, you get chloroacetylene, once again, another short-lived intermediary, and acetylene. But what’s really, really nice here is that you’ve bypassed, you know, vinyl. And vinyl, often, is more toxic with lower MCLs than your parent compounds. So, that’s a really good feature of iron that you can get, that you don’t necessarily get in bioremediation.

So, let’s talk about some other reactions that occur in the subsurface. Sorry if this seems like chemistry class, but sometimes it’s unavoidable to have these formulas up here. This top equation that starts with 5FeO, which stands for zero valent iron, is a balanced chemical reaction for iron with PCE, C2Cl4. And you can see when you have a forward reduction you get, you know, oxidized iron C2H6, which is ethane and your chlorites are reduced. And that’s what you really wanna happen. When you put your iron in the ground, you wanna reduce your PCE to something that’s innocuous, in this case, ethane.

But there is another reaction that also can happen, and there’s actually several, but the primary one that we need to consider is the reaction of ZVI with water. ZVI is a very, very powerful reductant and it’s capable of reacting with water to form molecular hydrogen, and that’s the bottom equation there. And all the molecular hydrogen can be beneficial, it can be used by the microbes that assist in doing the biological degradation of the contaminants. It’s not a direct reductant and you don’t get a reaction with molecular hydrogen in your contaminant to form innocuous by-products. And even in a highly contaminated site, there’s a lot more water around than there is PCE, for example. So, every molecule of iron that reacts with water is, I consider it to be, kind of wasted.

So, our objective, and what we try to do when we engineer our remedial products is to maximize the reaction with PCE relative to the reaction with water. So, how do we do this? Well, there’s been a lot of research in the last few years on how to optimize ZVI for the reaction with chlorinated contaminants. This actually isn’t new. This work actually began in 1995, approximately, and what people did was actually sulfidated the surface of the iron, and what they found is that when you sulfidated the surface of the iron you formed a core shell structure where you have iron, which is still the bulk of your material, in the middle of your particle, and when you deposit an iron sulfide layer on top of it, a lot of good things happen.

If you look here on the right, this is a graph which was taken from an “ES&T” article that was published about a year ago by Fan et al., and it’s really striking. If you look at these bar plots, the left is bare iron, bare ZVI. And what these researchers did was they measured the relative amount of the electrons or the iron which went to reduction of water and compared it to the amount of iron that went to the reduction of the TCE. And if you look at it, you know, the upper 90% of the stuff actually is kind of wasted in producing hydrogen, and very, very little of the of the iron went to reducing TCE.

What has been discovered is, on the right side of this bar graph, you can see that sulfidated iron and it’s exact opposite. Sulfidated iron really doesn’t react with water, so what that allows you do is have all your electron efficiency go to the TCE, you get much, much faster reaction rates, much better efficiency in reactive capacity. And it’s really been a groundbreaking revelation that we’ve learned and really come to recognize in the last couple of years. Another thing that it does allows us to make an aqueous phase ZVI product where the reaction with water is passivated so we can actually make colloidal iron in water.

So, this is treatability study that we did here in the last few months, and what I’m trying to do here is verify the results that have been published by Dr. Fan, Dr. Tratnyek, etc. at the other research areas. There’s people at Texas Tech that do this as well. And I compared carbonyl iron, which is unmodified, it’s dry iron straight out of a can, and I doused it in a bottle with about six milligrams per liter of PCE and compared it to our AquaZVI product, which is the sulfuidated colloidal iron, of about the same size, it’s a little bit smaller than the carbon iron, but for comparison, they’re relatively close, and compared the reactivities.

Now, one thing that’s different about these two studies, I learned that to get a good reduction, in a month or so with carbonyl iron I had to add 50 grams per liter, with AquaZVI I only had to add 2 grams per liter. And if you look at that the reaction progress over time, and you run through the kinetic analysis, you can see that the that the sulfidated iron has got about, on a mass basis, about a 30 times enhancement in reactivity with PCE. And this data that we did in-house is corroborated by stuff that’s done by other researchers. So, it’s really revolutionary how much faster by adding just, you know, a couple mole percent of iron sulfide to the surface of the iron can enhance the reactivity.

So, I’m gonna change course here, a little bit, and talk about the reactivity in regards to biodegradation. And instead of having your beta elimination pathway that bypassed the sis in vinyl, when you do metal-assisted bioremediation, at least one of the pathways that occurs is more traditional. You have this stepwise, sequential reduction of your contaminants. And this is instead of just injecting iron into the ground it’s a little more of a complicated potion, per se. Step back here. Excuse me.

There’s a mixture, you add iron, with the purpose of the iron is to make the groundwater reducing. You usually get an ORP of minus 200 or less, almost immediately, and also dexygenated, and also promote some abiotic degradation. You add organic donors, which provide a long-term source of molecular hydrogen, water, it’s an aqueous-based process. We generally recommend adding commercial dechlorinating cultures. Sometimes you have to have pH modifiers, this process works better at a neutral pH. And when you add all these things together you get a really, really fertile environment for biodegradation. If you look on the right there, there’s a portable ORP meter, in the concoction, a little bit everything put together with ORP of minus 400. And look, I’ll talk about a site where we applied this in a little bit here.

So that’s, kind of, you know, the first cornerstone that we’ve considered in our process reactivity. So, and now I’m gonna try to segue a little bit here into delivery. You know, how we engineer our materials so they can be delivered to the contaminants. And like I said earlier, you know, it’s a contact sport, you can have a really, really reactive material, but if you can’t get it into the ground and bring it into contact, you’re not gonna have a successful remediation program.

So the key feature of small particles, you know, iron is dense, its specific gravity is about eight, and if you pour that in water, you know, gravity is gonna take control and the stuff is gonna sink. But one thing we have, you know, on our side is that smaller particles are buoyant, they still settle, gravity still acts on them, but they settle at a much slower rate than a larger particle size. Well, you know, for example, if you increase the particle size by a factor of 10 the settling is gonna decrease by a factor of 100, there’s a square relationship there.

So, what we try to demonstrate here, in this slide, is that there’s AquaZVI in water, two to three microns, and we just literally pour the stuff in a bottle, shake it up, and you can see it suspends. On the right, there is coarser iron, 40 microns, approximately. Put that stuff in a bottle, shake it up, and you can actually, physically watch the stuff settle with your eyes. This demonstration is done better in-person than on a slide, but this still illustrates the problem that you have with these larger irons. And they’re really not all that big. If you look at them, they kind of look like flour or sand. You can’t really even see the individual grains, but since iron is so dense, the stuff does settle and it gives you problems.

So, if you wanna inject the smaller stuff, the colloidal stuff, it’s really easy. You just pour the stuff in water, put it in your mix tote, you can inject it right into the ground without, generally, having to add any sort of additives, organic additives. When people do conventional microscale iron, generally have to add thickeners, you know, Guar is a typical one that’s used, end up with a thick suspension that artificially keeps the larger particles in suspension, and there’s problems with that as we’ll see here on the next slide.

So, staying on the topic of delivery, what I’m trying to do here is compare the characteristics of the suspension and the delivery of a colloidal iron system compared to a microscale iron system. So on top, that’s AquaZVI that’s being poured into a fish tank, and we removed the fish beforehand, so don’t get PETA on me here. Fish went into another bowl before we did this test. But, anyway, you can see how this stuff blooms, very little agitation. If you’ve seen the PlumeStop demonstration, or marking literature, actually behaves quite similarly, it looks the same.

And you go to the right of that, there’s a sandbox demonstration where, you know, at a low pressure we’re injecting this suspension into a sandbox, and you can see there’s a nice uniform front. The particles are small enough, they can fit within the grains of sand in the interconnected pore space, and you get a nice uniform distribution of the material. Compare that to a thickened microscale slurry on the bottom, that’s a picture of thickened iron, actually in a grout pump, which is the really inelegant way to inject iron, but when you have something thick you actually have to use high pressures because the stuff is not gonna go on the ground unless you really, really force it mechanically.

And if you look at the right, there’s a depiction of an injection well on the ground where thickened microscale irons are being injected, and you see that you have, you know, a homogenous distribution. You get channeling, you get fracturing, and the problem with that is that you actually have areas, right here, if you look at the pointer in between the areas where the amendment has been delivered, where you don’t get anything delivered. And the problem with that is that, you know, the stuff that’s in there is not gonna get in contact with your iron or your other amendment, is not gonna achieve your remedial goals.

Now, sometimes what happens when you have this sort of situation is you intersect the screen on the monitoring well and the iron or your other amendment, you know, goes into the monitoring well and sinks to the bottom, and they test it, and everything comes back, you know, peachy keen, and then you might do a confirmation well by DPT a few feet away and you, more or less, have unaffected treatment. So, that’s delivery. Don’t take this for granted, delivery is every bit as important as reactivity, and if you don’t have both of them together, you’re not gonna have a successful project.

All right, the third cornerstone is persistence. As I said earlier, you want something that’s gonna last. You don’t want something that’s gonna, you know, be around for a few hours, and maybe a day or a week, and be reacted away, and then you’re gonna have rebound and a lot of other problems. And this is, you know, for those of you that are familiar with NZVI, or nanocrystalline zero valent iron, some people have called this stuff champagne powder. If you put NZVI in water, it actually bubbles like, you know, champagne. And that’s actually the iron reacting with the water to form hydrogen, and it literally just boils away in front of your eyes. So, what we try to do is, through using slightly larger particles, instead of using nano, which is, you know, .2 microns, we’re using 2 microns, it gives you persistence, and also sulfidating the material also reduces the reaction with water.

This plot here is a repetitive spiking test that was done at REGENESIS. Taking AquaZVI and doing repetitive spikes over, it looks like about a five-month period, and this test is still ongoing. Each of these spikes is about 10 milligrams per liter and, you know, a half-year into this, you can see that there is continued degradation with very, very little reduction in the reactivity. The orange plot is a control, you can see, has kind of taken off. So that’s persistence.

We’ll get to the fourth cornerstone of our remediation goals, for lack of a better term, is ease of use. You know, iron, traditionally, has been delivered dry. It’s in super sacks or cans, and because of that, it’s not easy to work with. You know, you have to use forklifts or, you know, expensive or intricate powder-handling equipment. You have dust, you have inhalation hazards, which is common when using in any sort of dry powder. And what we try to do is by making the materials instead of in a liquid suspension form is to alleviate those problems that are associated with the handling of dry powders.

And there’s, on the right, is a picture of a ladle of aqua metal, or AquaZVI, which, you know, it’s a couple thousand centipoise, really, really easy to handle, if you’ve ever been in a pail you can just dump it into your mix tank, or it can be pumped using double diaphragm pumps or other similar equipment. And, more or less, you just have to use, you know, your standard PPE such as, you know, safety glasses, etc., but you’re not gonna have to use, you know, full on respirators or whatever because it’s not issues with dust. It’s also not issues with using, you know, heavy equipment to move the stuff around. Really, really, really simple to use, just add the material to water, pump it in the ground, and you’re on your way.

All right. So, what I’m gonna try to do this is tie everything together here. I’ve talked about reactivity, persistence, delivery, etc. You know what, this is a neat little plot here that shows the functions of iron as a function of particle size. So we’ll start off here on the left and go to the right. The left are smaller materials. I’ll start with soluble iron, which would be ferrous iron solutions, such as CRS that’s sold by REGENESIS. We’ll go up a little bit larger to NanoZVI, which is typically about .2 microns, and we’ll scroll across to the near microscale, which would be the REGENESIS products, AquaZVI and MicroZVI. And as we go to the right we get to the larger materials. So this red plot here talks about the ease of injection, and I’ll get back to that here in a minute.

Let’s talk about kinetics first. Generally, stuff that’s smaller has more surface area, so it’s more powerful kinetically. It reacts more rapidly. So, you know, NanoZVI here on the left, a lot of surface area, reacts really, really quickly. And as you go across this plot to the right and you use, you know, the powdered ZVI or the millimeter, you know, the cast iron, the scrap iron, not very reactive.

The next thing I’m talking about is persistence. This is kind of the yellow line here, and it’s the inverse relationship with reactivity. Stuff that’s small is short-lived, and stuff that’s large last a longer time. And if you look right here in the middle, you kind of got a sweet spot. It’s right here where my cursor is right now. What we found for ZVI, and actually other remediation amendments as well, is that you get down to the near microscale area, you know, a micron or two, you kind of get the best of both worlds. You can get good reactivity, but you can also get persistence.

The red plots, not quite so simple. This talks about the ease of injection. So, we’ll start off here on the left. Soluble materials, easy to inject, you can get water in the ground, you can get these in the ground as well. But you have a little bump here when you talk about NanoZVI, and this has been one of the problems that people that did NZVI, you know, 10, 15 years ago when it was kind of en vogue is that they couldn’t inject the stuff.

And people that are involved in material science that have done ceramics, like me, for, you know, 30 years or whatever, you know, the answer to that’s actually pretty simple and it’s agglomeration. Small particles tend to clump. There’s a lot of surface area, there’s inner particle forces, so instead of injecting discrete nanoparticles that are .2 microns, which theoretically should be easy to inject, you end up injecting much, much larger clumps or aggregates. Kind of, the analogy I like to give is instead of injecting a single grape into the ground, you inject a bunch of grapes. And because of that, people have really, really suffered on getting good distribution.

But you go back to our sweet spot, to our near microscale regime, you know, one to two microns, the particles are actually large enough where the agglomeration issues become much, much more manageable. You can use dispersants, etc. to keep these things from agglomerating, and because of that you get much, much better distribution and material that’s easy to inject. You do have to do a little bit of mixing in recirculation because of the effect of gravity, but it’s very, very gentle. You get up to, you know, powdered ZVI, 30, 40 microns, for example, gravity starts to really become a big issue, and the other issue is that the particles are allegedly larger than the pore space in the sand particles where you’re trying to inject it into.

So, more or less to apply the powdered ZVI via injection wells or in situ, you’re gonna have to use some sort of high-pressure technique or possibly soil mixing as well. And if you’re using the really, really big stuff, soil mixing or trenching is the only way to make it happen. But in the key takeaway here, I’m trying to combine the four cornerstones on one plot here. If you look right here in the middle, one to four microns is really where you wanna be, it provides the best of all worlds.

Let’s talk about the different types of iron that are available on the markets today. I will start off on the larger stuff in the bottom and we’ll work our way up. You know, cast or scrap iron is big stuff. You can actually see the stuff with your eyes. You know, it comes from a crushed car, for example. And I’m sure some of you have had a car that’s broke down on the side of the road and, you know, you realize it’s gonna cost more to fix than it’s worth, so you call the towing guy, he goes, “All right, title for 300 bucks.” You say, “Okay.” Hand it off to him and it ends up in the crusher, and it’s very possible that that car, which was my ’97 Windstar, by the way, ended up in a PRB someplace.

So, you know, it can work but that’s more for your mechanical applications. You go up to what I consider to be more engineered irons, you know, it’s several vendors of commodity iron somewhere in the range, you know, of 40 to 100 microns, stuff is powder, kind of looks like flour. Smaller side of commodity iron would be there are specialty grades that are, say, 3 to 10 microns, which is starting to be where it’s easier to work with. It’s still about three times the size of our colloidal products, but they start to behave more like a small particle size material. NZVI is .2 microns. There’s a TM micrograph of an NZVI material right up on the right. And just for comparison, soluble materials, which, you know, aren’t solids.

So how do we inject these different types of materials, how do we use them for remediation? The smaller materials, soluble amendments, NZVI, colloidal iron, can be done through either screen wells, which is really a good feature if you wanna do multiple injections, you wanna use the existing infrastructure. The material is small enough where it can actually be injected through the slots of PVC or wells or sometimes there’s other ways to do it using sampler screens. You can also use direct push. There’s many different types of tooling involved where you can get the stuff distributed into the ground. If you go a little bit bigger to the commodity irons, you know, you have to use fracking, you can use soil mixing, etc.

Gonna run through a couple of examples of the applications of colloidal iron in the field. This is a site in Florida, which was a 1,1-DCE site, which is somewhat unusual. That’s the parent compound. The contractor decided to do this straight abiotically, didn’t add any bioremediation amendments or microbes. The middle skid there is actually calcium carbonate. We did buffer this site. The native pH was about five, we wanted to get that above six where the reactivity is optimized.

So, the red areas are where the contaminants are. And monitoring results were very, very positive. There is like eight or nine sites, eight or nine mining wells on this project, and all of them, you know, we’re in the green area where we had environmental compliance with the state, and on this left well, you know, the results are pretty striking. We started off, 200 PPB, at the end it was more or less non-detect. So, this is an example of an abiotic degradation, no daughter products, it goes straight to either FTE or ethane.

The next slide here is a little more interesting. This is a metal-assisted bioremediation project in Texas. If you’ve seen my webinars before or seen me give this talk in person, you’ve probably seen this before. That machine there that says GOFF is a vapor degreaser. This site, they were rebuilding alternators and the degreasing was part of the process. And these guys at the plant, they went home on a Friday, came back on a Sunday, and this thing had ruptured, and there was about 200 gallons of TCE that spilled onto the floor, and they came back on Monday, the paint was peeling from the walls. You know, now, you’d bring in full HAZMAT, have the fire department there, you know, EMTs there, probably. Well, back in the day, they didn’t know any better, they just had like the janitors come with squeegees and squeegee this stuff into a trench and they just started working again.

So, you had 200 gallons of TCE, and there’s the aquitard about 10 to 12 feet down, and it had been sitting there for 20 years with little or no natural attenuation. This picture, we actually got this from the wall of this plant. They had closed it. They moved the manufacturing overseas. I guess it was cheaper to make new alternators overseas than it was to remanufacture them. And the people that left the building, their parting shot was to take a picture of this and post it on the wall, so a little bit of a legacy there. We used metal-assisted bioremediation, colloidal iron, organic donor, pH modifier, it was slightly acidic so we wanted to get the pH up, nutrients dechlorinating microbes, kind of hit this with the kitchen sink.

So this is the monitoring results in one well near the source zone. What’s really important to realize here is that, you know, initially, in 2008, before this program was done, TCE was 4300 micromolars, which is about 400 milligrams per liter. So you’re talking about really, really contaminated groundwater. You know, obviously, DNAPL still present. The initial program, there is maybe about 60 injection wells, I’d say, screen wells, where the injection was done. We had a colloidal iron organic donor, and really, really good result of getting rid of the TCE. You can see it went from, you know, 400 milligrams per liter down to less than 5, probably. But the problem is that we converted most of it to sis. On a molar basis, it was more or less a one-to-one conversion to sis.

So, we talked to the customer, talked to some of the consultants that were involved in bioremediation, did some tests. Did a much smaller program a couple years later where the focus was to get the pH up, you know, it was in the fives, we wanted to get it, you know, above six where bioremediation happens the most effectively, and we also added dehalococcoides. And sure enough, it worked really, really well, and within, you know, about a year after the program the sis was gone. There was a nice little neat spike in ethene, which you rarely see in the field, an ethene spike this large. It almost looks like a bottle test. And we have data out to, say, 2016, and 5 years later, everything was below MCL. So, you know, metal-assisted bioremediation is really powerful. If you do it properly and add all the components that you need to make things work, you can have a successful outcome.

I’m gonna segue to the REGENESIS product suite. Right now there’s three iron products that are available. AquaZVI is a water-based amendment, which is engineered pretty much strictly for in situ chemical reduction or abiotic degradation. It’s 40% iron sulfidated, two to three microns in water. And what’s really neat about this is it can be co-applied with PlumeStop. We’ve done several bench studies and it actually is very, very synergistic and does not affect the absorption properties of the PlumeStop.

If you wanna do a metal-assisted bioremediation project instead, you can use MicroZVI, which instead of being suspended in water the material is suspended in glycerol. This will give you a mixture of ISCR and anaerobic bioremediation. Iron is basically the same, you know, about two to three microns, and this stuff can be co-applied with organic amendments such as 3DME or whatever you wanna use for your project and dechlorinating microbes. On top of that, there’s the legacy product, which is the CRS, which is a soluble ferrous iron solution, which does promote ISCR, and that’s a process called BIRD or biogeochemical reductive dechlorination. And if you have any questions about that you can give me a call.

So, as Rick said earlier, REGENESIS is invested into a state of the art colloidal manufacturing facility in San Diego County, and right now, we’re setting up to manufacture the colloidal zero valent metal products. We should have full-scale kick production, you know, within a couple weeks. And, on top of that, we’re gonna make PlumeStop there and other colloidal products that are in the pipeline. We’re also gonna do R&D there, you know, we’re not gonna rest on our laurels and try to improve the products, come up with new things and try to stay on top of the state-of-the-art.

So, we’re getting down to the end of the talk here. There’s a summary. There’s a picture of me up there on the right, by the way, you know, doing my best field impression. I’ve been called Bob the Builder more than once on sites, by the way. So, I guess the yellow vest and the hardhat makes me look like Bob the Builder. I haven’t had kids that age in a while, so I’m not really familiar with that show, but I’ll take their word for it. And, by the way, that’s James Harvey with the injection trailer, you know, showing how the stuff is mixed and applied.

So, in summary, you know, ZVI has been around since probably the ’80s, actually, but in the last, you know, several years, we’ve really tried to take the base technology and engineer it that to make it good technology and make it great. And that’s by reducing the particle size, sulfidating it, you know, adding the organic additives that make this stuff suspend well. And you can never, you know, go back to these four cornerstones enough: reactivity, delivery, persistence, and ease of use. What we really try to do is provide a product and a technology which will take into consideration each of these four, so at the end of the day, you’re gonna have a successful project outcome. And that is it for my part of the webinar.

Rick: So thanks, John. Let me just start off with an apology, we had some audio issues up front, we wanna make sure that those were addressed. If it makes you feel any better, they were probably twice as bad for me as they were for you, so we all experienced the feedback. We’re gonna move into the question and answer period. If you’re not familiar, within the app itself there is a place for you to ask questions. We have several that have come in so far, but I would encourage you to submit those questions now. Every question that is submitted we will answer, so if we don’t get to your question, just rest assured that we will respond to you directly within 24 to 48 hours.

So, we’ve got a great group of folks from end-users to regulators to consultants, we’ll get a broad range of questions. I’ll start with one of my own. You showed a couple of different examples, some sites where ZVI was standalone, some sites where it was metals-assisted bioremediation in conjunction with donors and bioaugmentation. Could you maybe speak to the decision making process on where you might use one standalone and where you’d use it in combination with other approaches?

John: Absolutely, Rick, that’s a really good question. As we talked about earlier, ZVI is a really, really reactive with the parent compounds. So, if you have a site that’s mostly PCE or TCE, with maybe a limited amount of natural attenuation or degradation, that’s really, kind of, a prime candidate for using straight abiotic reduction or chemical reduction.

If you look at the reactivity with iron with vinyl chloride, for example, it’s actually not as reactive So, in those cases, we found that the microbes, if they’re applied properly and have a good fertile environment, they’re actually more or better capable of reducing vinyl to ethene. So, if you have a site with a mixture of daughter products, it’s probably better, in that case, to use metal-assisted bioremediation. There’s also a few contaminants that don’t react very well directly with iron, DCM, 1,2-DCA, trichloropropane, for example. In those cases, it’s better to use bioremediation.

Rick: So, getting a few questions related to distribution, which we both agree is key to any remediation technology. Could you maybe speak to what type of radius of influence you can expect? They’ve given an example here of 10-3 centimeters per second in a fine sand. I know it would rage on the different types of pathologies you’re injecting into, but what are typical radius of influences for this material?

John: Kind of our default well spacing is somewhere about 15 feet, typically, which translates to a radius of influence of 7 to 8 feet. We found that, over the years, if we, you know, keep our well spacing 15, 20 feet, there’s a really good chance that we’re gonna get a uniform subsurface distribution. There are cases where it’s physically impossible to have walls that close together, it might be infrastructure involved etc., and if needed you can use larger spacing, even if you have to put more material into each well.

Rick: Kind of a distribution, application question. Are there any special handling requirements for ZVI? Are they stable under atmosphere conditions? Do they need to be stored under anaerobic conditions? Kind of walk us through that process of delivery, meaning to the site, and the application at that field site.

John: The materials are engineered to be easy to use, so it’s shipped in pails, it’s not shipped under a nitrogen blanket, for example. The AquaZVI, you probably wanna avoid freezing if possible. If you have an application where you actually might experience cold weather, probably be better to use the glycerol-based material. And it’s also probably better not to store the stuff, you know, above 100 degrees Fahrenheit for an extended period of time. But at ambient conditions, you should be able to have a shelf life of, you know, months if not even longer, up to a year. As far as handling, just use common sense, you know, standard PPE. And there’s really nothing out of the ordinary that you have to do to be safe. The fact that the materials already starts in liquid makes it a lot easier to use and user-friendly.

Rick: So, I wanna go back to, kind of, your discussion of different types of iron products. We have a question here related agglomeration, and you’d talked about NanoscaleZVI. Specific to the colloidal irons, is agglomeration an issue? If so, do you apply stabilizing agents? How do you prevent agglomeration of even one to three micron-sized particles?

John: All right. Thanks, Rick. Well, in our manufacturing process, we add organic additives to the material that aid in the suspension and the delivery of the material. So, it’s more or less a one-shot product, you don’t have to add anything in the field. If you look at the iron under a microscope, or conceptually more likely, there actually are dispersants and other organic additives that reside on the surface of the particles that prevent inner particle approach and agglomeration. So, it’s actually very easy to use. And talking about nano iron, I mean, there have been advances in the nano iron technology where it does suspend better than it used to, but due to the large surface area and the small particle size, you’d have to add a lot more organic additives to make it work, and you’d also have to use much more aggressive mixing and agitation to get the stuff suspended.

Rick: Great. So, we’ve got a question from one of our best clients here. So, what concentration envelope is AquaZVI best suited for?

John: AquaZVI can be used for anything from DNAPL down to low PPBs. That’s the great thing about abiotic reactions is that they’ll, more or less, work at any concentration. Now, I will premise that with the fact that it’s not gonna react directly with DNAPL. It’s and aqueous phase reaction process so you do have to get the DNAPL into the dissolve phase for the stuff to react. And if there are ways to do that and if you have questions you can give me a call and we could talk about that off-site.

Rick: Good. Here’s another unique question, a good one. So, for, you know iron PRBs that have already been installed, can this technology be used in combination with an existing PRB to either regenerate it, or in the event that groundwater is moving around it, basically optimizing an existing PRB?

John: That’s another great question, and then answer is yes. There’s a couple ways that could be done is that one is that you could actually install another PRB, upgrading it from the existing one where you have smaller, more reactive materials that give you a better distribution than what’s often encountered in PRBs. They could act as a sentry, for lack of a better term, a downgradient.

Another thing with PRBs is that you could consider doing a mixture of the colloidal iron with PlumeStop. You know, PlumeStop is good at promoting biodegradation inside a PRB, but if you add ZVI you can actually give it an extra kick and get some abiotic degradation as well, and possibly lessen your daughter products that could come off from the PRB eventually.

Rick: So, we’re getting quite a few questions related to DNAPLs. Kind of wanna go back to that treatment envelope. You know, there’s an upper limit, obviously, where this technology can be applied. Could you maybe give some guidance to those folks who are either dealing with residual NAPL…you know, it’s pretty rare we see free phase DNAPL. But are you designing PRB slightly downgradient of those? Are you using in combination? Have there been sites where you use these with…?

John: Yeah, thanks, Rick. As I said earlier, NAPL requires, you know, getting the undissolved phase into the aqueous phase. Iron is not gonna react directly with NAPL. And, you know, going back to your freshman chemistry, you come to the point where like dissolves like, and NAPL is generally a non-polar material such as PCE, and the approach that we’ve tried to do when we had cases like that is actually apply a non-polar substance into the ground that actually will suck the NAPL into the organic droplets and then it will be released slowly into the aqueous phase where the reactions occur. That’s what happened at the Texas site. I truly believe that when we added the organic, it acted as a sink for the NAPL and sucked it up, and we had the aqueous phase reactions that occurred.

There was a project called the Saber Project that was done maybe 10 years ago, I believe somewhere in Great Britain, where they used bioremediation to address NAPL, and that was more or less a promise. You have to solubilize the NAPL and do a partition into a non-polar phase and then get it into the water where the reactions occur. So it’s a little bit trickier, but it can be done.

Rick: So, we’ve got another delivery question here related to…we’ve several, kind of, fractured rock, fractured limestone, basalt, any special application instructions or guidance when it comes to fractured rock environments?

John: When we’ve done work in fractured rock, we’ve generally gone more or less in the straight boreholes that have been drilled to the ground, and what’s important is you have to isolate your vertical intervals. If you just pop the material into an open borehole, it’s gonna find the path of least resistance, and most likely, you’re gonna find most of the material going into the largest fracture in the ground. So, it’s not that difficult to use packer assemblies where you isolate safe, you know, three to five-feet vertical interval, inject it into the fractured rock, which isn’t that difficult to do because the stuff suspends. If you’re using large iron, the material is gonna sink and end up in the bottom of the column. But the colloidal material is gonna flow right into the fractures and distribute that way. So, I guess that the key is verticle isolation for something like that.

Rick: Couple of questions that I’m gonna combine. Can you talk to maybe some of the potential water quality impacts related to ZVI injection? Are there any regulatory considerations that would be unique to this material?

John: Oh, every jurisdiction is obviously different, and every regulator has different opinions as to, you know, what’s good or what’s bad. But, you know, with a straight abiotic application of iron, really, the only reaction products that you’re gonna see are our ferrous iron, which typically is present natively and is subsequently gonna oxidize to iron hydroxide, iron oxyhydroxide, for example, you know, rust, essentially. And maybe a slight increase in pH.

If you do metal-assisted bioremediation, you know, the biodegradation products are gonna be the same as if you added the donors by themselves. You might get, you know, a little bit of acetone, which subsequently degrades, etc. So, and that could be anything specific to iron as far as doing the metal-assisted approach.

Rick: Good. So we just have a couple minutes left. We have a hard stop at 11:00. Keep your questions coming because we will respond to those. We’ve got several that I haven’t gotten to. You know, I wanted to go back to, kind of, the fundamentals. And, you know, one of the powers of ZVI is multiple pathways for degradation including the abiotic pathway. It’s been my experience that you’re gonna see multiple pathways, right, so you mentioned the lack of daughter products or the potential for lack of daughter products. Any guidance to the participants, I mean, we’re not suggesting you won’t see daughter products, you’re just gonna minimize them, correct?

John: Yes, that’s correct. There’s always gonna be a parallel pathway that involves daughter products. The key is to try to minimize that relative to the more direct pathway. You know, the thing about putting iron in the ground is that it will promote bioremediation using the native microbes, sulfate reducers, etc. that will take TCE, that’s just for example. So that’s gonna happen in parallel, then the keys try to minimize that in relation to your more direct reduction pathway. So, you know, you generally will see a little bit of sis, but the idea is to minimize that.

Rick: So, we’ve gotten several questions related to cost. I’m gonna try to answer it, and then I’m gonna kind of throw it to you to give us some idea or a magnitude cost. Many of these questions are just, you know, what are the range of costs, how does it compare to other types of iron, other types of technologies? But from my experience, it’s so site-specific, it’s difficult to answer that question because it depends on the site conditions, the types of contaminants, the goals of the project. And our advice has always been let’s put a design together, let’s figure out what the lowest cost alternative is that has the highest chance of success compared to all the other remedial alternatives that are appropriate to that site. So, with that as a primer, are there any things that you wanna kind of add in terms of cost estimating, range of magnitude of cost, things like that?

John: One thing that differentiates colloidal products versus microscale products is that you generally dose differently. What we dose is a pore volume basis. We calculate the amount of pore volume that’s in the aquifer that’s to be treated and dose, you know, maybe five grams per liter of pore volume. If you’re using conventional amendments, they often do it on a soil mass basis. If you run those side by side, our designs typically use about one-tenth the amount of material, as like a microscale iron, for example. So, the cost, at the end of the day, even though you’re using a more expensive material, your overall product cost is less. On top of that, since the stuff is easy to use, your application costs could be considerably lower as well.

Rick: …that we didn’t get to a promise that we will. I just wanna build, kind of, on the introduction since we had a little bit of trouble. Just really wanna welcome you and James to the team, we’re really excited. One of the things we are most excited about is our in-house manufacturing. Not only of the colloidal iron, but of PlumeStop. And you touched on the innovation that’s gonna come from that. You outlined, kind of, the schedule and timeframe for production in April of this year. If there are folks on the line that want additional information you can always contact your local sales managers of a slide in a moment that has John’s contact information, my contact information. We’ll be happy to answer any questions that we can. At this point, I’d like to throw it back to Dane, and you’re gonna discuss the survey options, correct?

Dane: That’s right, yeah, thank you, Rick. That does conclude our presentation for today. If we did not get your question, as Rick said, someone will make an effort to follow up with you. Just a couple of quick reminders, as Rick mentioned. First, you’re gonna receive a follow-up email with a very brief survey, so we really appreciate your feedback. So, if you could, please take a minute to let us know how we did. Also, you will receive a link to the recording of this webinar as soon as it is available. If you need immediate assistance with a remediation solution from REGENESIS, please visit regenesis.com to find your local technical representative and they’ll be happy to speak with you. Thanks again very much to our presenters, Rick Gillespie and John Freim, and thanks to everyone who could join us. Have a great day.