Optimization of ZVI Technology for the In-Situ Remediation of Chlorinated Contaminants

Dane: Hello, and welcome, everyone. My name is Dane Menke. I am the digital marketing manager here at REGENESIS and Land Science. Before we get started, I have just a few administrative items to cover. If you’ve attended any of our webinars in the past, you might notice a different user interface for today’s event. Well, this new interface features the same functionality as seen in our previous webinars. It also gives us the increased capacity we need to host the growing audiences attending our webcasts. With that said, if you experience any issues with the transmission during the webcast, please email marketing@regenesis.com. Also, we would like to give a special welcome to our Canadian clients and let you know that REGENESIS has recently started to provide direct support to Canada. Since we’re trying to keep our time to under an hour, today’s presentation will be conducted with the audience audio settings on mute.

This will minimize unwanted background noise from the large number of participants joining us today. If you have a question, we encourage you to ask it using the question feature located on the webinar interface. We’ll collect your questions and do our best to answer them at the end of the presentation. We are recording this webinar and the link to the recording will be emailed to you once it is available. In order to continue to sponsor events that are of value and worthy of your time, we will be sending out a brief survey following the webinar to get your feedback. Today’s presentation will focus on the “Optimization of ZVI Technology for the In Situ Remediation of Chlorinated Contaminants.” With that, I’d like to introduce our presenters for today. We are pleased to have with us Dr. John Freim, director of material science at REGENESIS. Dr. Freim is well known throughout the environmental industry for his work in developing breakthrough in-situ chemical reduction technologies successfully employed throughout the environmental remediation industry.

Dr. Freim has over 30 years of experience in materials processing and 15 years in the environmental remediation industry and led the establishment of the first REGENESIS state-of-the-art colloidal product manufacturing facility. In his role with REGENESIS, Dr. Freim is responsible for the manufacture of colloidal materials including PlumeStop, liquid activated carbon, and S-MicroZVI. We are also pleased to have with us today James Cobb, director of health and safety at REGENESIS. James will be joining us to discuss safety procedures being implemented by REGENESIS in response to COVID-19. In his current role at REGENESIS, James ensures environmental health and safety for the global workforce at REGENESIS. He is responsible for safety training and program implementation, as well as near-miss reporting and analysis throughout the organization. All right. That concludes our introduction, so now I will hand things over to John Freim to get us started.

Dr. Freim: Thank you, Dane, for the gracious introduction. As he said, my name is John Freim and I’m going to be talking today about optimizing ZVI technology for in situ remediation with an emphasis on sulfidated ZVI use for in situ projects. Whenever we design a remediation amendment or approach, there’s really four different cornerstones that we have to address. One is obviously reactivity. The amendment that you use has to be reactive and eliminate the toxic groundwater contaminants or alternately promote an environment that facilitates their removal. But that’s not it. A reactive material by itself won’t always get the job done. There’s some other considerations that need to be looked at. These include distribution. Remediation is a contact sport. If you don’t deliver your amendments to the contaminated groundwater, your chances of success are diminished greatly.

On top of that, you need to deal with persistence or longevity. The amendments have to last a long time. If they don’t last very long, they’ll peter out, you’ll have rebound, and you’ll have to go back in another time, which costs time and money. On top of that, you want your materials to be easy to use and safe. If you can develop your material in a process that satisfies all four of these, you have a winner.

I’ll take you back a little bit of background information here, explain to you what ZVI is and how it works in remediation. ZVI is a reductant, and that means is that when it’s applied to groundwater, it oxidizes and supplies electrons, which are accepted by your contaminants and they’re converted from, in this case, PCE to an innocuous compound such as ethene. Another similar equation would be hex chrome. Here it’s chromate. You add iron to the system, you can actually form chromium hydroxide, which is a solid precipitate, which is stable and less toxic.

Another thing that’s really great about ZVI is that the reaction pathways that occur when it comes in contact with these chlorinated compounds are different than what’s generally experienced with biological degradation. Biological degradation, there’s a stepwise degradation where you remove one chlorine, add another chlorine, and it’s the top pathway here. But what happens with ZVI is that a large fraction of the reactions occur via a reaction pathway that bypasses these toxic daughter products. So if you look at the bottom pathway here, you have these coordinated acetylenes, which will eventually be converted to ethene or ethane, with the far left intermediaries produced. Typically, you get about 90% of your reaction pathway goes through this lower beta emission pathway.

So what is S-MicroZVI? Well, it was kind of an acronym for sulfidated microscale ZVI. So this is a picture on the right here, which is an artist’s depiction of the S-MicroZVI particle. And it’s got a unique configuration where you have a core material or interior that’s one substance, but your surface or your shell is a different substance. In this case, our core is zero valent iron and our shell, our surface, is reduced iron sulfide. If you see here, the yellow shell is the FeS. I will say that these particles are not yellow in nature. They’re actually grayish-black, but a lot of people associate yellow with sulfur so for illustration we’re using this color scheme. This is not a new technology. If you go back into literature, you can see that this was first reported about 1995 or so, but the commercialization efforts were very slow and the first large scale use of these materials for remediation was about 2017.

So let’s go from the artist depiction to actually using some analytical techniques to see what these particles look like. What we’ve done in conjunction with Paul Erickson at R&D in REGENESIS, we went to Caltech and they have a SIMS machine, which stands for Secondary Ion Mass Spectrometry. And what this is, it’s a microscope that actually lets you see the metallic composition or the elemental composition of your material. So right here is a SEM picture of the S-MicroZVI particles in grayscale. But when you actually use SIMS, you can use a detector to distinguish what the elemental composition of the particle is, both on the surface and on the interior. The reason why you can do this is that it’s actually a destructive process. At the beginning, you’re going to see basically what’s on the surface and as you pass through these scans, you’re going to kind of cutaway and see what’s in the interior of the particle.

This machine we have red is a sulfur-rich region and green is an iron-rich region. So what we’re going to do is do a time-lapse video here, starting at scan 1, which is the starting particles. By the time we walk through the sequence on scan 20, we’re pretty much going to have bladed through or removed all the sulfide on the surface and we’ll be able to see what the interior of the particle looks like. So let’s start the scan here. It’s red at the beginning. We’re starting to eat away at these particles and as we go through here, we’re going to see more green and green, and by scan 20, all you’ll see is red on the periphery of these particles. We’ll go through this one more time. It’s kind of showing you or confirming the fact that we do have this core-shell microstructure with sulfur on the surface and iron on the interior. And to my knowledge, this is the first data that’s showing what these things look like analytically.

So that’s what these materials are, their composition, but what we really care about is how reactive they are. They’re gonna have a unique composition, but if they don’t provide anything beneficial, they’re not of much use. So to demonstrate the reactivity, there’s been some bench studies done at REGENESIS where we’ve compared the reactivity of sulfidated MicroZVI on iron or SMZVI to bare iron, which is ZVI with a very similar particle size and composition, but without the iron sulfide shell on the surface. Pretty standard test conditions, amber bottles, relatively high amounts of TCE, 20 milligrams per liter. We used 4 grams per liter ZVI as our dose for either material, and we generally buffer these to pH7 with HEPES buffer.

So this is a plot which shows the concentration in micromolar versus time. You can see we started off with about 150 micromolar TCE and it degrades fairly rapidly down to near zero at about 15 days. You could also see the daughter products on this plot. The cis is the yellow triangles and the vinyl or the other red dots there. And if you want to create the first-rate kinetic ray consonant for this, all you have to do is plot log of the concentration versus time and the slope of that line, which is linear, and it generally has a pretty high correlation coefficient of about 0.95, you can get the observed rate constant. In this case it’s 0.227 per day. A lot of times it’s more useful to normalize this for math. So all you do there is take your observed rate constant divided by 4 grams per liter and you get 0.057 liters per gram per day. Really good first-order behavior.

Now as a comparison, the bare ZVI, if you notice the plot here, this was also done at REGENESIS, it goes out to 90 days and we might’ve had about a 20% reduction in TCE in 90 days. So, the rate constant is far, far, far lower than sulfidized iron, at least 50 times lower, and we get about a 50 times or sometimes even greater enhancement in kinetics. And this result is corroborated by other published literature from universities and other laboratories. If you look at the reaction rate with cis, we have this on the right here of a similar setup. You can see that their reactivity is considerably slower. It’s not zero, but if you do the rate constant, it’s about 40 times less than TCE. So, although you do get abiotic degradation of cis, we would generally recommend, if you want to have the best outcome, we’ll combine this with some sort of biological treatment to improve the outcome.

So, let’s try to dig into this and see why sulfidated iron works better than bare iron or conventional iron. And to explain this, I think it’s best to just divide this into kind of a four-step process, which happens when you add sulfidated iron or any type of iron to contaminate groundwater. So, the first thing that has to happen is that you have to get the contaminants out of solution and sorbed onto the surface of the particle. If you don’t have the contaminants on the particle surface, you’re not going to have reactivity. Once they’re there, you have to oxidize the iron to supply the electrons that drive the reaction. Subsequently, you have to have an electron transfer from the core of the particle, the interior, to the particle surface where the contaminants lie, followed by contaminant reduction of TCE to ethene, or other innocuous species.

Let’s dig into this here. This is a depiction of a particle with a ZVI core and a shell. The shell can be either sulfide for sulfidated iron. If it’s bare iron, it’s going to be other things such as oxides or hydroxides. So we have contaminants in solution, sorbed to the surface, then we have oxidation of the core. Electrons are transported through the shell to the sorbed contaminant where you have an electrical chemical reduction from TCE to ethene. So, understanding the four-step process that occurs in the reactivity, let’s kind of compare bare iron versus sulfidated iron and look at their different characteristics. And this information will help us to explain why we get better reactivity with sulfidated iron.

So bare iron, first of all, is the depiction on the left and it’s really not bare. All metals have some sort of oxide or hydroxide coating on the surface. They’re reactive and they will react with air or water. So you’re going to have the ZVI core with, let’s say, an iron hydroxide surface layer. It’s always there. And if you look at the chemistry of iron oxide, it’s relatively hydrophilic, which means that it attracts water and repels TCE. And since we’re trying to sorb the contaminants onto the surface, this is actually bad. We’re attracting water to the surface instead of the contaminant that we’re trying to address. Another thing that we’ve learned is that iron oxide is a semiconductor. The electrons don’t pass through it very easily. There is resistance to electrical flow.

On the right, it’s a depiction of sulfidated iron, as I said earlier, it’s got an iron sulfide surface, which is relatively hydrophobic, which is good because it attracts TCE. It’s like a sink or a magnet to the contaminants in the groundwater. At the same time, since it’s hydrophobic, it repels water, which is good because we don’t want to promote hydrolysis reactions. The other thing that’s beneficial that we believe is iron sulfide is electrically conductive, so there is very little resistance to electron transport through the surface layer.

So we’ll do our animations here with the sulfidated ZVI, talk about contaminant sorption. So the particles have more hydrophobic sites than iron oxide, which is good. So there’s our TCE molecules being attracted to the surface while the water is being repelled. Also, because of this attractiveness to the contaminants, it’s more likely that you’re going to have ISCR reactions with the contaminants than with water. I think this literally is probably the most enabling feature of sulfidated iron is that it’s our chain characteristics.

Electron transfer, there’s literature that suggests that iron sulfide is an electrical conductor. Conduction does not slow or prevent ISCR reactions from happening. So there’s our contaminants that are adsorbed to the surface, past electrons, boom, boom, boom. Metallic in nature, so there’s very little resistance to the flow or the transport of the electrons from the oxidized ZVI core to the surface. Add these things together, we get better electron efficiency. I mean there’s competing reactions, iron is a reductant, it can reduce contaminants such as TCE, but can also reduce water through hydrolysis. So there’s the reaction of the electrons going to water, which is not good. You’re wasting away your iron, it’s an expensive material you’re putting in the ground. The purpose is not to hydrolyze water, its to dechlorinate. And also, every time that you lose electrons to water, you end up with some sort of passivation, an iron hydroxide or oxide layer that accumulates on the surface.

So we go through here, the sulfide layer will decrease hydrolysis. The water is not attracted to the surface. You got more of your electrons actually go to dechlorination. There’s papers that suggest that you get 99% of electrons actually go to dechlorination versus 1% for hydrolysis, which is very, very efficient. If you have bare iron, it’s basically reversed. It might be 90-10 with hydrolysis being the primary reaction. And one thing that’s good about this is that you are going to have a longer lifespan. Instead of reacting your iron away to form molecular hydrogen and hydroxide, it’s actually going to go to a beneficial use. And there is a review paper that kind of explains some experiments that were done that showed this electron efficiency.

So let’s segue into delivery or distribution. We’ve shown that the material is very reactive, but on top of that, we’ve also had really good experience delivering this material into contaminated groundwater. And one thing that’s important to realize is that iron is dense, its specific gravity is about 8. So when you put it in water, gravity is going to act upon it and it’s going to settle, and it settles actually quite rapidly. So for conventional commodity size iron, to get around this, you have to thicken it using thickeners such as guar or maybe xanthan gum or using aggressive mixing is the only way you can keep the stuff from crashing out in suspension. But one advantage of using smaller particles, the sub-5 micron particles, the best MicroZVI, is that they’re buoyant. And if you look at Stokes’ Law, they’re going to settle far, far less slowly. There will still be some settling, but it is manageable. And on top of that, we had transferred polymers in dispersants that aid in injectability and distribution.

So let’s look at a video that we did that compares the suspension behavior of commodity iron, which is a powder right there. So we’re going to add it to our beaker, stir it up, you notice it falls like a rock. Particles are big, might be some aggregation in there. Even if you stir it up, you’re basically going to have just a clump of particles at the bottom of the beaker. When you do our colloidal iron, it’s going to behave quite differently. The settling rates via Stokes’ Law are much less. Let’s shake it up here a little bit and you’ll see that you have a nice, uniform, black colloidal suspension. Particles are settling but at a much, much slower rate. So it’s manageable in the field. On the left, you have the picture of the beaker of settled commodity iron. On the right, it’s kind of a blackish suspension of colloidal iron.

And so that’s going to help you inject things, and another beneficial feature is distribution through sand. Now, these things have a small particle size and they’re generally much smaller than the interconnected pore volume of your sand or your solid that you’re injecting into. So you get a nice, uniform, prolonged flow of distribution of your product. And this is demonstrated in the sandbox in the upper right-hand corner. There’s a colloidal iron suspension that’s being injected at relatively low pressure, and the particles are being distributed uniformly through the sand. You can compare that to what happens with a commodity material that’s thickened. These things generally have a consistency of maybe oatmeal might be a good analogy, and they have to be injected at high pressures. That picture on the lower left is actually a suspension or a goop of thickened ZVI in a ground pump. And they’re injected at high pressures, which generally result in fractures or channeling in your subsurface. It’s not impossible to apply the stuff uniformly but you have to be way more careful. And even that, you’re not generally not going to have as good of results.

So let’s move on to our third cornerstone, persistence. This is some lab data that was done at San Clemente Research Facility. This is a repetitive spiking experiment in a bottle. So all of those vertical lines, they’re indicative of spiking about 20 milligrams per liter TCE into the bottle. You can see this test runs over about a year and after each subsequent spike, you look at the red line and what it says and the yellow line at the bottom, we pretty much had immediate reactivity with no accumulation of the chlorinated compounds in the bottle over the length of the experiment. The dashed line is a control that was done without any amendments in the bottle, and you can see that the concentration of TCE continued to climb over the year.

So it works great in a bottle, but sometimes the column is more representative of what you might see in the real world. So in parallel, there’s column experiments that have been undertaken. This is 1 to 2 milligram per liter solution of TCE that’s a flowed upwards through a column into which the iron material had been pre-packed and you can see through 60 pore volumes on the bottom we had essentially zero contaminants in the affluent that were passed through the sand column with the ZVI. We actually after about 55 pore volumes got bored with this test, decided to stretch it a little bit and add higher TCE concentrations then also used aerobic water, and despite stressing it so far, the results have been similar with no breakthrough. So this demonstrates, with over a year of experiments, we’re seeing really, really good persistence with the S-MicroZVI and a lot of that’s probably attributable to the fact that we’re not getting much reactivity with water, which wastes the iron material.

Ease of use. The field guys, you know, would obviously want to have something that’s easy to work with. This material, if you look at the ladle there, it’s kind of a semi-viscous black suspension, maybe looks like black paint and how you mix it is you just pump it or pour into a mixing tank with water. And that suspension is water-like, you know, it’s got a viscosity of essentially 1. Part of it is buoyant so they do require some agitation but not a lot. And you can add this with other amendments such as the organic donors and/or the PlumeStop material that REGENESIS also sells. Easy to mix, relatively easy to inject, a highlight is that we generally try to keep the pressures below 20 PSI, which is below the subtle fracture stress, to minimizing channeling and daylighting. Simple equipment such as air pneumatic pumps, it’s flexible, you can do it via DPT, top-down, bottom-up, different types of tools and screens, or if you need to, you can use permanent screen wells where we’ve injected a lot of material, you know, very deep, for example, where DPT might not be feasible, shallow or deep, barrier or grid configurations.

So that’s kind of the fundamentals. I’ve gone through the four cornerstones and I want to try to segue here, talk about a combined technology which is using PlumeStop, a colloidal carbon, and ZVI together. It’s a really synergistic mix and they work quite well together. If you’re not familiar with PlumeStop, it’s a colloidal activated carbon that’s ground down to a particle size of about a micron. It contains dispersants and transport polymers that maintain a stable suspension, is much smaller than either PAC or GAC, which on top of the delivery characteristics that are provided by the colloidal materials, also gives you a better sorption performance as there’s more free surface area. The one thing that needs to be accentuated is that activated carbon does not directly promote degradation. So you generally have to use this with a synergistic technology that will promote degradation so you can sorb and degrade, and sorb and degrade, and kind of go on through that cycle.

So it’s kind of a three-step process. We have sorption where the colloidal carbon sorbs the contaminants, happens very rapidly for most compounds. Then you have degradation of the sorbed contaminants by the ZVI or possibly biologically. And what that does is it frees the particle surface of the carbon to open up new sites for further sorption. So if we could go through here, we have a video which shows a sand stringer in the ground. We’re injecting our mixture of PlumeStop and iron and what happens is that they sorb onto the surface of the sand particles, a very thin layer of micron-sized particles, and we’re going to flush our contaminants through the groundwater. They’re going to sorb onto the surface and react away. There could also be some back diffusion and from the clay layers, and we regenerate our sites and we can continue to do this for relatively long time.

So let’s compare using ZVI as our degradation technology to organic donors. They both work very well. They have their own places in different situations. The advantage of using ZVI is that they’re both colloidal products. They can be co-applied, generally delivered at the same rate to the same areas. So you’re going to have good intimate contact between the two materials. Very importantly, ZVI doesn’t inhibit sorption onto the carbon. There are some organic donors such as EVO that will do that, which will blind the carbon so it won’t sorb the contaminants because the oil is sorbed preferentially compared to the TCE, for example. And with ZVI, as I talked about earlier, you minimize daughter product formation. So we don’t have to worry so much about forming cis and vinyl, which due to their isotherms don’t adsorb quite as well as the parent compounds do.

Biological degradation is good in some circumstances. It’s established, it’s been used by REGENESIS for five or six years on hundreds of sites. These compounds are water-soluble and lactate, for example, relatively easy to apply. You would have to take into consideration that some amendments such as 3DME, EVO can inhibit sorption and there’s daughter products produced. So if you have a site, we can go over the data at the end and see which of these two approaches might work better for what you’re trying to do.

Here is a field case study that was done over a year ago now. It is a barrier. If you look at the map there, the groundwater flows from the upper left to the lower right through that mess of injection points which are green and red. There’s four monitoring wells, CMW-3 is in the middle of the barrier, and three downgradient monitoring wells, the mixture of PlumeStop and S-MicroZVI at relatively equal concentrations, and on top of that, we did add some organic donor and microbes upgradient as a little bit insurance to make sure that we had good results.

So if you look at the results, this is a concentration of contaminants in the barrier and CMW-3, there’s direct influence. You pull water out of this well and it looks black. The linear scale on the left, it started out, you know, maybe 10 milligrams per liter, TCE first monitoring event went down to zero. Not surprising, you know, TCE sorbs really well to carbon. But what’s more interesting here probably is the emergence of the ethene and ethane a hundred days after the application. After the contaminants were reduced to zero, we kept seeing these reaction products being produced, which is really, really strong evidence that we’re seeing active degradation, not just sorption. Because if we saw sorption alone, we would not see large spikes in these compounds. So that was really, really promising results.

Biogeochemical response in the barrier was as predicted, you know, a pretty large order of magnitude increase of organic carbon, ethene, dissolved iron, and there was a little sulfate in there that was removed pretty much immediately, which is probably mostly a biological degradation pathway. So it is really outstanding results. As expected, you know, we got non-detect for parents and daughters, we saw the reaction products as desired, and we saw ethane, which is really good from the iron perspective because ethane is generally not produced biologically, which indicates that we had abiotic degradation. And I didn’t show this on the plot that ORP was minus 250 approximately sustained over the lifetime of these monitoring periods.

So let’s segue to the downgradient wells, as I said earlier, this did not have direct influence. When we bailed water from this well, it was clear. So the influence we’re seeing here is actually water passing through the barrier, being treated within the barrier, and as it flows downgradient, we’re going to wash away the contaminants that have been removed within the barrier. This is plotted, it’s important to note, as a log scale on the left instead of a linear scale. It kind of shows what I’m trying to show here a little more clearly that way. There’s two sets of lines on this plot. There’s a solid line, which are the contaminant concentrations, and there’s a dashed line, which is a modeled a degradation behavior using the PlumeForce model that’s used internally at REGENESIS to predict degradation by a combination of sorption and biological degradation.

So we’ll start off with TCE. You notice that after about 150 days, we had no TCE at the downgradient monitoring well, which means that the contaminant, what’s between this well and the barrier, had fully washed through and everything at that time had been treated in the barrier went down to non-detect and stayed there for the next, you know, 250 days or so. What’s a little more interesting is the daughter products. The orange line on the top there is cis. And then in this, well, we actually had more cis then TCE at the beginning. If you compare it, the degradation to behavior, it’s generally below the line. So not only was TCE degradation faster than modeled, so was cis, although it was not quite as distinct as it was for the parent compounds. But if you go back a few slides, you saw that this iron reacts better with TCE. So it’s not surprising. After 400 days, about 95% of the cis had been removed compared to the initial concentrations. Vinyl was a little stickier. We did have 80% degradation. It’s continuing to decline, but it’s a little slower.

Geochemical parameters in that well, the response is positive but not nearly as much as it is within the barrier, which is to be expected. And slight increases in TOC, sorbed iron, sulfate didn’t do a whole lot, but generally as expected. So in the downgradient well, very quickly a downward trend in TCE, it’s not immediate because you have to wash out the material that’s initially downgradient to flow through the monitoring well. And I also had, you know, a good response to the cis, 95% degradation and total chlorinated compounds, you know, modest increases to ethene and ethane, a lot of that is actually going to react in the barrier so it’s not surprising that you don’t see much of a downgradient. A little bit of increase in dissolved iron, which, you know, it could be a little bit of biogeochemical degradation at work as well. And once again, we had a sustained negative ORP, although not quite at the levels that we had within the barrier itself.

So I know it’s a lot of material in a 40-minute presentation, but we had a lot of good stuff to share here. In summary, you know, ZVI is not a new technology. It’s been around since at least the 1990s. But in the last, I would say, five years or so, we’ve developed colloidal sulfidated products that have taken a good technology, overcome a lot of the limitations of the established methods, and made it great. And it’s with all the remediation products that we sell and promote here, we really try to address all four of those key cornerstones. Without all four, you’re not going to have a successful technology. So I think we’re going to switch over to James Cobb right now and he’s going to give us some highlights about our safety practices in this COVID-19 timeframe. And thank you, and I’ll stick around and I’ll take questions afterwards.

James: John, thank you very much for the introduction, and thank you for all of those that are on the call for going through this presentation. I’m going to go through a short synopsis of what we’re going to be reviewing next week over the coronavirus and how we’re working on the field. So, just a little teaser of what’s going to be covered in next week’s webinar, we’re going to be going over what the coronavirus is, how is it spreading? We’re going to go into office safety, field safety for REGENESIS, and then in general, hotel safety, travel safety, and infection control.

So here at the REGENESIS office, currently we’re limiting the amount of personnel that are in the office to only the personnel that are required to be here, for instance, the R&D team and the production teams because they need to be here for, obviously, production and ongoing experiments in the lab. However, all personnel have training on the virus and the procedures, but keep in mind that these procedures and policies are changing on a day in, day out basis due to changing conditions and government mandates.

A couple of things that we’re doing for the manufacturing safety, all manufacturing personnel are being contacted on a daily basis to keep up with policies and procedures. We’ve posted some general guidelines around the facility to make sure that everyone is staying safe and adhering to all the CDC and county regulations, for instance, like the posting that you can see on the presentation. In addition, you can see some of the postings that we have on the front door to, you know, call personnel inside the facility whenever there’s a delivery or a shipment.

So field safety, this has been a little bit challenging for us. However, some of the things that we’re doing out in the field, like, for instance, with any procedure or policy you put in place, there’s always going to be hiccups that come along with those policies and procedures, things that are unforeseen. And I’ll kind of touch on that here in a second. A couple of things that we’re using to keep our distance, one is the use of hand signals. So in this photo, you can see that Steven is tapping on the side of the water tank in order to get the operator to turn the water pump on to fill up tanks.

The next picture, you can see Ken, who is using a workbench on the outside of the trailer to clean out a flowmeter. We do have workbenches inside the trailer, but we’re trying to keep that social distancing and when a person needs to be filling up a tank and somebody needs to be working on the bench, we’re trying to spread that out as much as possible. And then in the last picture, you can see our morning tailgate. Now keep in mind that these pictures are coming from a site that we had an amendment not to wear hard hats because there were no overhead hazards. But as you can see in the picture, we’re keeping our six-foot distance, everybody’s wearing respirators on-site, face coverings on-site, and then that’s how we’re keeping things going. One other thing I wanted to talk about on the tailgate specifically is we’re not requiring signatures so that no cross-contamination from pens or handling the same tools or paperwork is going to be an issue.

So as it is right now, we’ve got lots of scheduled projects that are coming up in the next weeks. Some of the projects that we’ve completed already in the last month, month-and-a-half have been in New York, New Jersey, Arizona. We’ve got a site in California we started last week that’s going this week. We’re trying to stay busy out there, trying to keep personnel safe and follow the mandates. And like you could see from the map here, you know, working in New York City and working in New Jersey, that’s some of the strictest guidelines in place as it is right now. So we’re following those guidelines and we’re still able to work safely out in the field.

One of the things that we always do whenever a new project comes in is we determine what is the best route to make sure that this project can be completed safely? So we take into all kinds of aspects in addition to the new COVID-19, we’re keeping up with state and local directives, keeping up with, you know, where the hotspots are, how we can…you know, if we need to move some stuff around, move personnel around, can personnel drive to the site? Currently, we’re not allowing people to fly, only with CEO approval, and then is the necessary PPE available? Currently, we have good stocks of PPE. We’re still trying to get thermometers, but that’s the only PPE that we’ve had trouble. So REGENESIS is following all the critical guidance handed down by the CDC to ensure that all of our field staff and our office staff are staying safe in this COVID-19 world.

You can see on the right, this is the CDC posting that we are under mandate right now, that could change tomorrow. But like I said, we’re staying in tune with state and local governments to make sure that we’ve got the latest and greatest. This is CDC posting, it talks about avoiding close contact with others, staying home if you’re sick, I can’t stress that enough. If you feel ill, stay home. At this point, we don’t really know who’s got COVID-19 and who doesn’t. You might feel fine, you might feel just a little run down, and you could be transferring the virus. So if you feel odd at all, feel sick, call your supervisor, don’t come into the office. A couple of other things on this slide, when you’re in public, wear a face mask, disinfect surfaces as much as possible, and then wash your hands. And I’ll be talking about washing your hands quite a bit, but at the same time, you know, that is one of the biggest takeaways from the CDC right now, just general hygiene. So wash your hands and we’ll see you during the next presentation. Thanks, guys.

Dane: All right, thank you, James. That concludes the formal section of our presentation today. So at this point, we’d like to shift into the question and answer portion of the webcast. Before we do that, just a couple of quick reminders. First, you will receive a follow-up email with a brief survey. We really appreciate your feedback, so please take a minute to let us know how we did. Also, you will receive a link to the recording of this webinar as soon as it is available. All right, so let’s circle back to the questions. If we’re not able to get your question within the time allotted, someone will make an effort to follow up with you after the webinar. All right, so we have a question for you, James, and it is, “Can you talk a little bit more about what you’re doing in the field in response to COVID-19?”

James: Yeah, so we’ll be touching on this in the next webinar next week with Wilke Logan. But for the most part, you know, we’re following CDC policies, procedures, we’re sending out staff ahead of time to make sure that field crews that actually show up on-site are, you know, not ill, not around anybody ill, that has traveled in the last 14 days to any of the known hotspots or around the world. In addition to that, you know, there’s challenges that we’re coming across, for instance, like the six-foot barrier while wearing a face mask is a little difficult to hear personnel talking. And so we’re going to kind of touch on that as well.

Dane: Okay. Here’s a question for you, John. And the question is, “How do you calculate the dose of S-MicroZVI and how long does it last?”

Dr. Freim: All right, good question, Dane. Thanks for that. So when we model a site, we take into consideration the groundwater flow, the porosity, and the concentrations of electronic scepters in the water, which would include not only the contaminants such as TCE, also some other species that can be [inaudible 00:46:37] such as dissolved oxygen and nitrate. What we can do in our modeling software is calculate the electronic scepter flux through the groundwater in a time period such as a year, and what we’ll do is dose the site such as the iron is consumed to move these electronic scepters that are passing through the groundwater. A typical site is dosed for about five years and we usually have a safety factor of two to five on top of that. So it’s actually done using science to get the dosage.

Dane: Okay. Thanks very much, John. So, here is another question and that is, “Does S-MicroZVI promote biogeochemical reductive processes?”

Dr. Freim: And the answer is yes, it does. There was biogeochemical reduction, often an acronym called BRD that’s used to describe this process. It is when you have ferrous iron in your environment that is reduced to form reactive minerals. These reaction minerals could include sulfides, hydroxides, etc. that can also serve as abiotic reductants for the elimination of your compounds. For example, a common one would be to have the ferrous iron that’s produced by the oxidation of your ZVI react with native sulfate and groundwater to form reduced iron sulfides. These can also react quickly with the TCE and the other contaminants.

I will caution you, however, that if you look at the chemistry behind this reaction, reducing sulfates to sulfide is an eight-electron reaction, so we’ll consume a lot of a reductant. So to best accomplish this, it’s good to co-inject your ZVI with their organic electron donor such as 3DME so you can get a more complete reaction to form your biogeochemical reductants. On top of that, another advantage of this is they can actually extend the zone of influence for your [inaudible 00:49:23]. Since these wells are all soluble, they’ll generally move out a little bit farther downstream than the solid reductants will. And you can get a more thorough and complete productive zone in the groundwater.

Dane: All right, thank you, John. So, moving on here, here’s another question. It is, “Being that the surface given by iron sulfide is hydrophobic, can it attract also other hydrophobic compounds such as, for example, TPH in the case of a commingled plume?”

Dr. Freim: That’s a good question. I actually haven’t heard that one before. One thing that I will say is that we’ve done a lot of injections with other compounds that you think would adsorb to iron as the organic droplets that are present in 3DME or the organic droplets that would be present in the EVO, which are vegetable oil. And the presence of these species does not appear to interfere with your activity of the ZVI. And given how much the attraction these would have for the surface, I think it’s pretty unlikely that TPH compounds, for example, at typical concentrations in the groundwater would interfere with the iron. I will caution you that if you have NAPL or free-phase hydrocarbons in the groundwater, this could possibly be a problem. But for dissolved species, it’s unlikely that it’ll have any negative effect.

Dane: Okay, thanks, John. So, next question here is, “What are the chemical reactions involved in the treatment of chromium and arsenic?”

Dr. Freim: It’s another good question. You know, I’ll premise this answer with my opinion that essentially metals and mobilization is not very well understood. But from my understanding, if he went back to my presentation on the first slide, I showed the reaction of hex chrome or chromate to form a trivalent chromium compound and, in that case, chromium hydroxide. So for chromium, I think the mobilization mechanism first involves reducing the hex chrome to trichrome followed by a reaction with water to form insoluble chromium hydroxide, chromium oxyhydroxide, and possibly other insoluble minerals. So you use the iron to supply electrons to drive that reduction followed by the reaction with water that makes them immobile.

I would say that the same mechanism could apply for arsenic where the arsenic is first reduced to arsenic 3 and then precipitates as insoluble minerals. Another thing that can happen with arsenic is that arsenic atoms can actually substitute for iron within the iron sulfide lattice. So you might actually have, you know, 1% or so arsenic that precipitates out into iron sulfide that’s formed by BRD that I talked about in the last question. So this is another mechanism where you can actually reduce the sulfate in your groundwater and the iron inspire the ZVI to immobilize. We’re doing some tests in R&D right now with arsenic, which actually have been very favorable. They will publish those in the not too distant future.

Dane: Okay. Thank you, John. So here’s a question for James and it’s regarding COVID-19, “How are you keeping up with state and local mandates?”

James: So, for the most part, I’m not keeping up with all state mandates. I’m keeping up with the states that we are working in currently, but at the same time, I’m using a website that gives me access to state health departments and that’s what I’m using to see where the directives are going and see what directives are in place for our field personnel. So you typically check that a few days before the job, typically on Friday, so if we have any issues, we can deal with them before the job starts on Monday. Like I said in the presentation, these things are changing on a day-to-day basis, and keeping track of it is a process.

Dane: All right. Thank you very much, James. So here’s another question for you, John. It is, “When more than one product is applied, what order are the amendments applied?”

Dr. Freim: So for example, I showed earlier the co-injection of PlumeStop and S-MicroZVI, in that instance, they’re generally applied together. They’re put in the same mixing tank, mixed together, and co-applied as a colloidal suspension. Because of mobility, characteristics, and particle sizes are similar, they will go to the same place in the ground and react together. When you do co-injection with biological amendments such as 3DME, it’s the same thing. You could externally co-inject them. There might be a few instances where you do the injection separate. Sometimes even might add the [inaudible 00:55:12] at the end of the job, for example. Generally, we’d recommend that be done separately, but not always. If you use an HRC, which is another organic donor, it has to be applied separately from the iron for health and safety reasons.

Dane: Okay. Thank you very much, John. And speaking of health and safety, next question is also for you, John, and it is, “Are there any safety protocols with the ZVI injections?”

Dr. Freim: For the most part, we’re going to use the exact same protocols that we’d use for injecting any amendment. So you’re going to use eye protection, wear gloves, try to use common sense. You have pressures in your lines, you know, just do your normal protocols. One thing that does need to be taken into consideration is that sulfidated iron does react with strong acids such as HCL to produce the rotten egg smell gas, which is hydrogen sulfide, which is toxic at relatively low concentrations. So at the end of the day, you don’t want to clean your tanks with HCL, for example, you want to rinse them with clean water. And in the ground, if you have a particularly acidic environment, then you want to make sure that you talk to us before you inject the sulfidated iron to make sure you’re not going to form hydrogen sulfide in situ. Do you have anything else to say about that, James?

James: Yeah. In addition to that, all of our field personnel have H2S cleaners in the trailers, so we’ve been trained on this. We’re sending out a new training here in the next couple of weeks over H2S just to give a refresher on everybody. But for the most part, we’ve only seen this in the field once and then there was additional issues with something in the ground causing this, but at the well top, we were seeing two parts per million, which is underneath the OSHA PEL for H2S. But nothing anywhere close to that in the bridge itself.

Dr. Freim: And let me add to that. And at the end of the day, you want to make sure you leave all your valves open. You don’t want to have any iron within closed valves. Flush everything good with water, just use general good housekeeping practices.

Dane: All right. All right, thank you, guys. Let’s see here. We have another question. This one is for you, John, and it’s, “Where has sulfidated ZVI been applied?”

Dr. Freim: That’s a good question. It’s been applied extensively in the United States. I actually put together a map that I don’t have with me right now, but I believe we’re up to about 32 states in the U.S. where we’ve actually done the applications of sulfidated iron, and on top of that, it’s been done in Canada and Europe. To my knowledge, there hasn’t been anything done in Asia or South America yet, but Europe is ramping up and obviously, a lot in North America.

Dane: All right, well, great. Thank you so much. That is going to be the end of our chat questions. If we did not get to your question, someone will make an effort to follow up with you. If you would like to learn more about remediation solutions from REGENESIS, please visit regenesis.com. Thanks very much again to our presenters, Dr. John Freim and James Cobb, and thanks to everyone who could join us today. Have a great day.