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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?

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.

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?

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.

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.

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.

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?

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.

So, what concentration envelope is AquaZVI best suited for?

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.

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?

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.

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…?

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.

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?

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.

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?

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.

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?

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.

Are there any things that you wanna kind of add in terms of cost estimating, range of magnitude of cost, things like that?

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.

Video Transcription

Dane: Hello and welcome everyone. My name is Dane Menke. I am the digital marketing manager here at REGENESIS and Land Science. Today’s presentation will focus on “Cost-Effective Approaches Using Colloidal Zero Valent Iron for In Situ Groundwater Remediation.” With that, I’d like to introduce our first speaker for today. We are pleased to have with us, Mr. Rick Gillespie. Mr. Gillespie serves as senior vice president North America for REGENESIS, directing a team of technical sales consultants and engineers across North America, providing industry-leading support to REGENESIS customers. He has over 20 years experience in the environmental remediation industry. All right, that concludes our introduction, so now I’ll hand things over to Rick to get us started.

Rick: Thanks, Dane. I’d like to personally welcome each of you to today’s webinar. I know how valuable your day is and we wanna say, thank you, for making time in your busy schedule. Our entire team is pleased to bring you today’s webinar on “Colloidal Iron for In Situ Groundwater Remediation.” Our purpose today is to train on the power and efficacy of utilizing zero valent iron to promote in situ chemical reduction, often referred to as ISCR. Our goal will be to provide details on how best to harness this remediation technology to achieve results to your contaminated sites.

Today’s webinar comes at one of the most exciting times in our company’s history. We are experiencing significant breakthroughs in the use of colloidal remediation materials like PlumeStop, our liquid activated carbon, and now colloidal zero valent iron. These remediation approaches are changing the way we treat groundwater. They’re being used to achieve permanent reductions and contaminate concentrations to gain regulatory closures at significant cost savings over traditional technologies like pump and treat.

Now, let me to pause there and introduce today’s speaker, John Freim. John brings a distinguished track record to his new role as director of material science at REGENESIS. With over 30 years of experience in materials processing, John and his colleague, James Harvey, will lead our effort to build our first state-of-the-art colloidal manufacturing facility right here in Southern California. John will be responsible for leading our milling and manufacturing, for not only colloidal iron products but also our other groundbreaking colloidal product lines like PlumeStop.