Dane: Hello and welcome everyone. My name is Dane Menke. I am the Digital Marketing Manager here at REGENESIS and Land Science. Before we get started, I have just a few administrative items to cover. Since we’re trying to keep this under an hour, today’s presentation will be conducted with the audience audio settings on mute. This will minimize unwanted background noise from the large number of participants joining us today. If the webinar or audio quality degrades, please try refreshing your browser. If that does not fix the issue, please disconnect and repeat the original login steps to rejoin the webcast.

If you have a question, we encourage you to ask it using the question feature located on the webinar panel. We’ll collect your questions and do our best to answer them at the end of the presentation. If we don’t address your question within the time permitting, we’ll make an effort to follow up with you after the webinar. We are recording this webinar, and a link to the recording will be emailed to you once it is available. In order to continue to sponsor events that are of value and worthy of your time, we will be sending out a brief survey following the webinar to get your feedback. Today’s presentation will look at emerging contaminants with a focus on treatability studies for PFAS and 1,4-dioxane.

With that, I’d like to introduce our presenters for today. We are pleased to have with us Dr. Ryan Thomas, associate and emerging contaminants practice leader for the Americas at GHD. Dr. Thomas is a scientist within the Innovative Technology Group at GHD. Within the Innovative Technology Group, he is leading research and development studies towards emerging contaminants treatment, including PFAS and 1,4-dioxane removal and destruction technologies to support pilot and full-scale installations. He also serves as a writing subgroup leader for the ITRC PFAS team and subcommittee co-chair for the National Groundwater Association, PFAS sampling and analysis team.

We’re also pleased to have with us today Dr. Sophia Dore, associate and director of the Innovative Technology Group at GHD. Dr. Dore has 19 years of experience in environmental remediation. She assists project managers by providing technical expertise in the areas of biology, chemistry, and remedial design. She also manages the treatability study laboratory and is responsible for designing, conducting, performing data analysis, and reporting on treatability studies, including chemical and biological treatments of contaminated soils and waters.

We’re also pleased to have with us today Dr. Kristen Thoreson, vice president of quality and process improvement at REGENESIS. Dr. Thoreson manages and evaluates the company-wide quality processes and continuous improvement activities at REGENESIS to ensure consistency, and reliability, and product quality, performance, and service. Prior to this role, Dr. Thoreson served as the vice president of Research and Development for REGENESIS and Land Science, where she led the development and implementation of numerous products and technologies. Dr. Thoreson is an inventor on several issued patents and is a frequent speaker at scientific industry events. All right, so that concludes our introduction. And now, I will hand things over to Ryan Thomas to get us started.

Ryan: Hey, thanks for the introduction, Dane. This is Ryan Thomas. I’ll be kicking off our presentation today. And our agenda is really focused on emerging contaminants, primarily for 1,4-dioxane and PFAS treatability studies. We’ll talk about, you know, what emerging contaminants are and then provide a brief overviews for 1,4-dioxane and PFAS in terms of their, you know, history and some technical considerations. We’ll then introduce treatability studies and then chat a bit about, you know, when they’re recommended for some of the projects. Finally, we’ll dive into two separate case studies with one focus primarily on 1,4-dioxane treatment evaluations, and the other on PFAS treatment evaluations. With that, let’s get started.

So what are emerging contaminants? Emerging contaminants are termed as, you know, synthetic or naturally occurring chemicals that are not commonly monitored in the environment, but really have the potential to cause known or suspected ecological or, you know, human adverse health effects. These emerging contaminants can be, you know, newly-synthesized compounds fresh out of the beaker or chemicals that are now detectable in water, soil, and even air just due to updated analytical techniques and methodologies.

Emerging contaminants can consist over really a wide range of chemicals such as pharmaceuticals and personal care products, industrial chemicals, or even byproducts of a process that are consistently showing up in groundwater, municipal wastewater, food sources, and of course, our drinking water supply. Now, one of the main issues with the emerging contaminants is that in most cases, very little information is known on these chemicals in terms of overall environmental impact or even human health impacts.

Additionally, studies to just understand treatment technologies for some of these emerging contaminants can be either limited or, in fact, non-existent just due to those compounds not being focused on or monitored in the environment. And what this really means is that it’s possible that existing technologies on our drinking water supply and wastewater treatment facilities are not effectively really addressing these compounds. Now, what we’ve observed is that when regulatory agencies are requesting the “emerging contaminants” sampling at sites, that usually translates to needing to sample for a PFAS and 1,4-dioxane at this point. And so, the focus of the next few slides will really start with 1,4-dioxane and then move into the PFAS technical guidance.

So first up, 1,4-dioxane is a synthetic chemical that is colorless liquid and completely miscible in water. This compound is a byproduct present in numerous goods such as dyes, anti-freeze, paint strippers, plastics, and even some consumer products including deodorants, shampoos, and cosmetics, traces of 1,4-dioxane may be present in food containing residuals from packaging adhesives or on food crops treated with pesticides that contain this 1,4-dioxane. But primarily, 1,4-dioxane was used as a stabilizer in chlorinated solvents, and oftentimes found at the chlorinated solvent sites. Environmental impacts include groundwater and drinking water sources, and there are some health standards and regulatory guidelines for 1,4-dioxane at this point.

So for a history and use timeline, 1,4-dioxane synthesis was first reported in 1863, but it wasn’t until 1929 that the United States commercial manufacturing began at least a small scale. In the early 1950s, production increased to large scale really as a result of 1,4-dioxane being used to stabilize chlorinated solvents such as 111 trichloroethane and trichloroethylene. By the mid-1980s, about 90% of the 1,4-dioxane produced in the U.S. was used to stabilize solvents. And in the mid-1990s, 111 TCA was designated as an ozone-depleting material and ultimately phased out.

In 2012, the U.S. EPA started their nationwide 1,4-dioxane sampling under the third unregulated contaminant monitoring rule, or UCMR3. And in that same year, the EPA published a drinking water Health Advisory at 35 micrograms per liter based on a lifetime cancer risk of 1 in 10,000. And in 2013, it was classified as a potential human carcinogen. At this point, the U.S. EPA has not adopted a maximum contaminant level for 1,-4 dioxane, but it has been identified as a chemical known to really occur in public drinking water systems that may require future regulation.

So for sampling and analysis for 1,4-dioxane in general, the conventional equipment has not demonstrated, you know, any problems with sampling for 14D and their different matrices. It’s a common impurity in detergents. We do see that some studies have detected 1,4-dioxane at elevated concentrations and leaching from a widely used decontamination to target. Because manufacturing processes can introduce 1,4-dioxane into cleaning products through chemical processes, it’s really recommended to thoroughly rinse the equipment to prevent residual detergents or, you know, surfactants that may be remaining on any sample equipment. And as always, you know, remember to collect equipment blank just so we can evaluate the presence of any residual 1,4-dioxane remaining on that sampling equipment.

For 1,4-dioxane and other emerging contaminants sampling, it’s recommended to use an ionic detergent that does not contain the 14D in it in the trace amounts. In terms of the analytical methods used for this compound and aqueous samples, they’re typically SW-846, use the method 8260 and 8270 which are common volatile and semi-volatile organic compound analysis methods for drinking water samples. Method 522 is employed that has a bit of a lower detection limit. And for, you know, the solid samples, SWA-846 method 8260 is utilized for those analysis. Some of the typical collection volumes and preservatives are mentioned in this table. But always consult the analytical lab to confirm the specifics and, you know, what’s needed for that analysis including the appropriate detection limits.

This slide has the generalized fate and transport of 1,4-dioxane that goes through the, you know, various pathways including volatilization, photodegradation, sorption, and even aerobic biodegradation. Also on this slide is general guidance on, you know, when to evaluate 1,4-dioxane in various media with corresponding conditions. So, for example, if you’re questioning if groundwater should be sampled at the site, then generally either you suspect a potential 1,4-dioxane release in a media, or, you know, chlorinated VOCs are present in the water, and/or, you know, 1,4-dioxane has been detected in other media such as the surrounding soil.

As for remediation and treatment technologies, again, 1,4-dioxane is miscible in water. It’s chemically stable, it doesn’t hydrolyze under typical conditions and does not readily adsorb to organic carbon. And it’s really these physical and chemical properties that result in large diffuse plumes of 1,4-dioxane in groundwater. And, you know, some conventional remediation and treatment approaches such as granular activated carbon and air stripping are not very effective at this point. This figure shows the technologies with their respective effectiveness towards 1,4-dioxane and is color-coded based on concentrations. And, you know, what’s shown here is that in situ technologies such as phytoremediation, chemical oxidation, and even co-metabolic bioremediation can be effective over a rather high concentration range for 1,4-dioxane. Some ex situ technologies that are fully demonstrated are UV with various oxidants such as, you know, hydrogen peroxide, ozone, and other catalysts, and the use of sorptive resins.

And with that, we’ll transition into PFAS. And, you know, at this point, most folks have heard about this class of chemicals. REGENESIS and others such as ITRC’s PFAS team have offered numerous webinars, factsheets, and even technical guidance on PFAS that go into regulations and some general considerations. So no, we won’t belabor too much on the general PFAS 101 details here. But for introduction’s sake, PFAS is the umbrella acronym for per-and polyfluoroalkyl substances. Of the per- PFAS, the PFAAS or perfluoroalkyl acids are really the most prevalent in the environment. And to this point, the two most study PFAS are perfluorooctanoic acid or PFOA and perfluorooctane sulfonic acid or PFOS. Other PFAS are being evaluated to better understand fate and transport and if regulation is needed at the federal and state levels.

Now, this timeline is full of, you know, useful information from really the production of PFOA up until where we are now in 2021. I’ll only focus on a select few here, really starting with 2016 with the U.S. EPA issuing their final drinking water advisory for PFOA and PFOS. It’s 70 parts per trillion for the single compounds and the sum of the two compounds. In 2019, the EPA announced their plans to deal with PFAS, including some proposed regulations. In 2020, the EPA issued preliminary determinations to, you know, regulate PFOA and PFOS specifically. And there has been a lot of movement at the, you know, federal and state level towards regulating these compounds in drinking water and in environmental media. And in fact, in mid-October 2021, the U.S. EPA unveiled their strategic roadmap for PFAS to confront contamination nationwide focus on research restriction and remediation of PFAS. And a previous REGENESIS webinar really went into great detail related to this roadmap, and I highly recommend it.

So this table is a compilation of really the best available PFAS sampling practices from literature. As you can see, there are specific acceptable items versus prohibited items that need to be addressed when planning for any PFAS sampling events. Some of them include acceptable items for cosmetics use during the sampling events, in addition to the actual equipment that’s used that comes in contact with the sample. Now, as more of a disclaimer, it’s not worth it to mention that the available practices for PFAS sampling often lacks the research to validate some of the, you know, certain equipment or materials’ ability to impact the samples. But as a rule of thumb, if you have questions about that equipment, it’s best to, you know, start with a chat with the manufacturers to gain more insights on the composition of that equipment.

As for analytical methods, there are a few at this point. U.S. EPA has two approved methods, but they are specifically for drinking water. Those methods are 537.1 and 533. Method 533 is a bit of a complementary method to 537.1 in that it includes an additional 11 PFAS. So, you know, when used in combination, 29 PFAS can be tested in drinking water. There are ASTM methods to help analyze for PFAS in other media besides just drinking water to include soil, sediment, and wastewater. And the EPA does have a draft method, 1633, that’s intended to eliminate the use of modified drinking water methods for other matrices. Really the point with any of these methods is that it’s important to identify the appropriate method for the actual media that you’ll be testing so that the results are meaningful.

And sampling results and the need to remediate, there are a number of treatment technologies for PFAS-impacted water at this point. Each technology has pros and cons related to removal efficiencies and, you know, considerations for these contaminants. I always recommend treatability studies or at least a pilot study before full-scale implementation, just to help reduce the overall cost of that project. There are some field-demonstrated technologies for water treatment such as granular activated carbon and, you know, ion exchange resins. For both of these technologies, the presence of co-contaminants such as petroleum hydrocarbons and, you know, total organic carbon can reduce the efficiency of the technology unless pre-treatment is implemented. There are quite a few emerging technologies that are at the bench in pilot skill level to include electrochemical, you know, oxidation and reduction, plasma destruction, as well as most recently biodegradation. But much more research is needed to understand byproducts resulting from, you know, some of these technologies.

As for soil, the options are typically excavation and incineration that aims to, you know, destroy PFAS using high temperature incinerators. Other options include stabilization with, you know, uses amendments to reduce leaching of PFAS from solid materials, and typically involves carbon and clay-based reagents to stabilize the contaminants. And, you know, finally, containment that would include an off-site landfill construction and more of a capping strategy. Stabilizations can also be used in conjunction with the containment. So there are a number of technologies that are effective to treat PFAS-impacted soil and water, with new technologies constantly being evaluated for more efficient treatment and to include more of a wider range of PFAS at this point. And with that, I’ll turn it over to my colleague, Dr. Sophia Dore, to discuss treatability studies and a 1,4-dioxane case study.

Sophia: Thanks, Ryan. So, I’m part of, and Ryan is too, of the GHD Innovative Technology Group. And we do have facilities for field and some pilot testing. But our main habitat is the lab that you see here at the top of the screen. And we’re going to talk about some work that our group has done in this lab.

So treatability studies are what we do. And a treatability study is something performed in the lab. We use site soil, sediment, groundwater, you know, media from the site and we construct small-scale microcosms which show at a smaller scale the processes that are going to be occurring in the field. These are small jars, or bottles, or beakers, we can set up a large number of these to test a whole bunch of different conditions at the same time, changing conditions kind of on the fly to optimize treatment. And, of course, we’re doing these under optimized conditions. We have ideal mixing. For the most part, we’re at room temperature unless we decide to do it at a cooler or warmer temperature. So, you know, this allows the processes, whether they’re chemical or biological, to happen faster than they would in the field. And so, you know, within a few weeks, we can have some results and some indication of what’s going to occur in, you know, a process that would probably take years in the field.

So when would we do the treatability study? Well, we do a lot of proof of concept testing. Sometimes it’s the stakeholder or a regulator that needs it, or sometimes the client just wants to have some indication that this harebrained scheme that we’re proposing is going to work. So yes, we test it in the lab to show that the concept actually is valid. And it’s good to do this for in situ treatments because, you know, there’s a lot of variability in soil, groundwater chemistry, site-specific conditions can have a huge effect on what’s going to happen in the field and how treatments are going to proceed. So, you know, even though something has worked at site A, it doesn’t necessarily mean you can implement it exactly the same way at site B and have the same results.

And then sometimes when you have a large site, if you can decrease the amount of reagent that you’re adding by, you know, 5%, 10%, for a large site that can have a large overall cost savings. So sometimes it is worth it to optimize your dose rather than just adding a little more and to be on the safe side. And then we also, in addition to treatability studies for in situ field implementations, in situ remediation, we also do some studies that would model like industrial wastewater treatment or things like that. And if you’re going to invest in a new piece of equipment for wastewater treatment, you probably want an indication that the process that you change into is going to work. So we do test that at the small scale as well.

So here’s our lab group. And see our team here, most of these pictures are pre-COVID, though there’s the one where Jennifer is wearing a mask and that’s our post-COVID work condition. So, anyway, what you can learn from treatability studies is, first of all, is this technology going to be effective? And if it is, you know, which of the many reagents that are available for treatment is the best one? How much do we add? Do we need to add, say, nutrients, or a catalyst, or something like that? And then we can also find out, you know, within the context of site-specific soil and groundwater, what are our degradation rates going to be like? And then whether there are any other issues that are going to arise, are we going to do something to the pH? Are we going to mobilize metals? Is there something about the site that means we have to use more of a reagent or amendment than is typical? So we can learn all of these things by testing stuff on the bench.

Okay, so now we’re gonna move into our case study that our lab group did, looking at groundwater that was impacted with 1,-4 dioxane. And this comes from a site in Southern California, a former commercial manufacturing site where we have… You know, as Ryan mentioned, chlorinated solvents were often packaged with 1,4-dioxane as a stabilizer. So, they often co-occur as contaminants. So that’s exactly what we have here is chlorinated solvents and 1,4-dioxane in the groundwater. So, we have PCE, TCE, 1,1,1-TCA and 1,1-DCA, as well as 1,4-dioxane.

Okay, so, 1,4-dioxane we know degrades under aerobic conditions. And so, just a little bit about the pathway. It involves monooxygenase enzymes that eventually split open that 1,4-dioxane ring and then allow the… So rings are fairly impervious to microbial attack. But once that ring is split open, then it can be broken down into smaller non-toxic compounds fairly easily by naturally occurring microorganisms in the ground. And, of course, we all know the biodegradation pathway for chlorinated solvents. Under anaerobic conditions, the reductive dechlorination pathway where a hydrogen knocks off chlorine and replaces it, and so compounds become progressively less chlorinated.

Okay. So, we have a mixture of chlorinated solvents and 1,4-dioxane. How are we going to treat this? We looked at two strategies here in this study. One was treat the burning solvents under anaerobic conditions and then switch over to aerobic conditions to degrade the 1,4-dioxane. And the other was to try to treat everything under aerobic conditions, because chlorinated solvents can degrade by a co-metabolic pathway under aerobic conditions. So we provided an additional carbon source for this co-metabolism to take place. So what we’re trying to do is find out how these strategies are going to work. Like, can we degrade the chlorinated under aerobic conditions? Can we degrade the 1,4-dioxane on these co-metabolic conditions? Is it better to do the anaerobic followed by aerobic, or can we use one set of conditions?

Okay. So, this is the sample that we started with. We had soil and groundwater from the site. So, you can see we have quite a large concentration of 1,4-dioxane on, like, the upper range of the scale that Ryan was showing. And then fairly significant amount of PCE with lower concentrations of the other chlorinated compounds. So, indicating here, of course, that not much degradation of the PCE has occurred because we have more of it and less TCE.

Okay. So this is our first strategy for doing the sequential aerobic…sorry, anaerobic followed by aerobic biodegradation. So we tested emulsified vegetable oil, EVO, with some nutrients in inoculum and started under anaerobic conditions, and then after 12 weeks we added oxygen to switch over to aerobic conditions. So we set up these tests in the anaerobic code to make sure that they were anaerobic to start with. And then once we… And we monitored for degradation of the chlorinated solvents. And once we had them down to a fairly low level, we injected oxygen into the same microcosms to turn the conditions aerobic.

Okay. So this is basically what happens. So, almost immediately we saw the concentrations of the chlorinated nosedive, except for the 1,1-DCA, which was a much slower decline. But, you know, we saw very good degradation without having large concentrations of daughter products being created. But we didn’t see a decrease in 1,4-dioxane, of course, under the anaerobic conditions. So right after the 12-week sample was taken, we added oxygen to the microcosms, and here we then started to see 1,4-dioxane decrease. I should point out we previously saw an increase in 1,4-dioxane, which I think is due to the fact that we also had 1,4-dioxane in the soil that was in the microcosm. So that started to get released and picked up in our sampling event. And then, of course, these concentrations decreased after we added the oxygen. So even bearing in mind that it increased, we still ended up 41% below the original, the first concentration of 1,4-dioxane. So that was pretty good.

Okay. So then the second strategy where we did the co-metabolic biodegradation. So we looked at a co-metabolic inoculum. And we also looked at activated sludge as a possible co-metabolic inoculum. And we had dextrose in there as a carbon source for the co-metabolic growth. Here are some graphs showing what happened here. You see that we did get reasonable degradation of the chlorinated solvents. You can see that the PCE is in like the reddish pink color. So that’s easier to see. You can see that that decreases. And then we have the 1,4-dioxane in the gray. And we see, like, a slow decline in 1,4-dioxane over time, but nothing like the kind of sharp decrease that we saw under aerobic conditions. And then, of course, the decrease in the chlorinated is also a little bit slower than what we saw under the anaerobic conditions.

And yeah, so this is the one where we added activated sludge rather than the specific co-metabolic inoculum. You know, the degradation is a little bit less, but we still see the same general trends of the decrease in the chlorinated, of course, I should point out, other than 1,1,1-DCA. Again, similar to what we saw on that anaerobic microcosm. So, overall, when we added the nutrients, the dextrose as the carbon source in the co-metabolic inoculum, we got 23% treatment of 1,4-dioxane after four weeks, and then we didn’t really see any further decrease.

When we added the activated sludge as the inoculum, we got 26% treatment of 1,4-dioxane. But again, this occurred in the first four weeks and then we didn’t see much further decrease. We did get up to 80% treatment of the chlorinated with the co-metabolic inoculum as well. We didn’t get as much treatment of the chlorinated as when we added the activated sludge but not the co-metabolic inoculum. And then without an inoculum, we didn’t get much treatment of the 1,4-dioxane but in just a little treatment of the chlorinated.

So, overall, you know, we showed that under anaerobic conditions, yes, we can remove chlorinated. So we already knew that. But we did need a microbial inoculum in this case. We didn’t have presumably a large enough indigenous population of the reductive dechlorinators to degrade the chlorinated without the microbial inoculum. So we also were able to remove chlorinated under the co-metabolic conditions. So this co-metabolic inoculum also worked for them, but we got greater treatment with anaerobic conditions using the traditional pathway, the reductive dechlorination pathway.

And so, we also were able to get some treatment of 1,-4 dioxane under the aerobic co-metabolic conditions, but we got more treatment of 1,4-dioxane when we just we did the reductive dechlorination upfront and then turned the conditions aerobic. So, overall, we concluded that it’s probably best to use the optimum conditions for each reagent, the anaerobic for the chlorinated and the aerobic for the 1,4-dioxane rather than try to do them both at once under co-metabolic conditions. So that’s what we recommended moving forward for the field study and that’s what has been implemented. And I think that brings us over to the PFAS case study. So I’ll turn this back over to Dr. Ryan Thomas.

Ryan: Hey, brilliant. Thanks, Sophia. Now I’ll take us through the PFAS case study. So, as an overview, a groundwater collection system was installed at a formal industrial site in Michigan to capture impacted groundwater. The initial target parameters focused on phosphorus, iron, and oil and grease. The permanent treatment system design was completed in 2017 with monitoring in 2018 to redefine some final design details. Final design of that treatment system was postponed to allow monitoring of the operational system discharge to the locally publicly-owned treatment works to be used to refine the influent concentrations and, you know, flow rates for the final design. But, you know, during this monitoring period, the POTW began sampling for PFAS. They detected and following that detection, the original groundwater treatment design was abandoned, and a new evaluation was initiated to identify cost-effective treatment options for PFAS, and the co-contaminants present in the groundwater.

So, we started at the bench-scale level working in our Innovative Technology Group to evaluate a number of technologies, including granular activated carbons, anion exchange resins, adsorbents, and literature review and demonstration for alkaline ozonation. So for the GAC, we see that the breakthrough curves for the column study results and, you know, shorter-chain PFAS, PFBA, and PFPeA breaking through before, you know, 1,000 bed volumes of water with PFOS breaking through after, you know, nearly 1,500 bed volumes.

Although we were mostly interested in PFOS due to the regulatory exceedances, we, you know, have to be mindful of potential future regulations that we have an understanding of the other PFAS that may require treatment. In this case, if, you know, these shorter-chain PFAS became regulated, then we know that the media usage rates estimates we will need to really account for, you know, PFBA, PFPeA, and PFHxA breaking through and, you know, driving change out frequencies of the GAC.

For the anion exchange resin results, we see that PFOS remains non-detect to nearly 8,000 bed volumes, at least in this graph. Our last sampling that’s not shown here was really at 11,000 bed volumes, still resulting in non-detect for PFOS. We do see that PFBA and PFPeA starts breaking through. You know, after 3,000 bed volumes, the detection limits were varied a bit between non-detect and elevated detection limits for the influent compared to the F1 column sample, resulting in a bit of, you know, ratio different here with this particular curve.

In comparison to the GAC column, it’s clear that, you know, the resin is more efficient at treating the PFAS in the sample. And, you know, this makes sense because then the initial characterization, you know, what we saw was that total organic carbon was around 18 milligrams per liter. GAC is not selective, meaning that the adsorption sites will be consumed by that organic carbon, truly resulting in, you know, breakthrough of PFAS sooner than expected and what we can observe here with these results as well.

So, our client is interested in evaluating innovative technologies that have the potential to destroy PFAS instead of, you know, simply moving from the water phase to adsorptive media [inaudible 00:34:29]. We reviewed the literature to identify, you know, promising technologies and came across a few, including alkaline ozonation. We performed bench scale studies in our lab to further evaluate the technology but monitoring a larger suite of PFAS and really destruction products. Our results show 75% and 97% reduction in PFAS, including PFOS in addition to some of the others within the process. And the process included ozonation pre-treatment step at low pH, followed by ozonation and peroxide addition at alkaline pH for the duration of the treatment.

And our initial studies using a, you know, 30-minute ozone pre-treatment have resulted in significant decreases in PFOS for both the ambient pH and the low pH treatments. Some of the other PFAS resulted in reduced concentrations as well. Given that, you know, more percent removal was observed for the initial low pH test, all the follow-up experiments were performed under the low pH pre-treatment conditions. These additional tests were performed to really confirm initial results, but also optimize the hydrogen peroxide to ozone molar ratio and modify pre-treatment times. With the varying hydrogen peroxide to ozone molar ratio and pre-treatment times, we saw minimum changes in the PFAS concentration distributions and their patterns. So, the results from the shortest pre-treatment time with the lowest hydrogen peroxide to ozone ratio test are shown here on the screen.

A whole bottle analysis using modified EPA Method 537 method was performed under the same experimental conditions as the previous treatments. Prior to sending the whole bottle samples for analysis, 15 milliliter alkalytes were removed from the middle of the bottle, effectively a grab sample and, you know, sent to a commercial lab for analysis using the ASTM D7979 method to, you know, determine if there were significant differences between sampling methods and analytical methods. And the results from the whole bottle analysis resulted in, you know, the similar patterns of PFAS treatment observed between the whole bottle and the grab samples at the individual time intervals that we were evaluating.

But for the EPA Method 537, we saw higher PFAS concentrations compared to the ASTM method performed at a different commercial lab. After three hours of treatment, the whole bottle analysis measured around 100 to 110 nanograms per liter for PFOS as compared to 13 nanograms per liter for the ASTM method. The initial concentration was around 330 nanograms per liter using the Method 537.1 compared to, you know, 280 nanograms per liter for the ASTM method. The observation that, you know, two different analytical methods resulted in different results for the same sample, you know, certainly highlights the importance of maintaining the same analytical lab and method for one project unsightly to have that make that overall consistency. Overall, the removal trends do suggest PFAS treatment, you know, that’s not associated with the sampling techniques.

So in total for alkaline ozonation, six rounds of testing have been performed to, you know, understand the PFAS treatment potential of this technique on PFAS impacted water including, you know, industrial groundwater from the site as well as spiked water samples. The results from Round 5 are presented here in this table and suggest that at a lower pH and/or the use of ozone can result in,, you know, greater PFOS removal.

The PFAS-impacted industrial groundwater and spiked water was subjected to, you know, air-sparging tests without ozone, and that was performed at a commercial lab. What we saw was a 23% reduction of PFOS was observed for the spiked water test with an increase in gas phase concentrations detected after, you know, 480 minutes of air sparging. Other PFAS analyzed resulted in less percent reduction and increases in the gas phase concentrations, and minimal reductions and increases in the gas phase concentrations were observed for the industrial groundwater sample.

So, in conclusion there, the results from all tested including the PFAS analysis as well as inorganic ions and total organic fluorine measurements that I didn’t show in this presentation, you know, they indicated that decreases in PFAS concentrations are due to a combination of removal and destructive mechanism with enhanced removal under the acidic pH ozonation pre-treatment conditions. What we saw was that some short-chain PFAS concentrations increased during the experiments followed by an overall decrease in concentration under that continuous alkaline ozonation conditions. After the initial 30-minute low pH pre-treatment step, we did see PFOS concentrations reduce between 36% and 50%. The pre-treatment step at low pH or ambient pH conditions prior to the addition of base or oxidant and is only ozonating conditions at that point. Therefore, it is a bit unclear if, you know, PFAS removal or destruction is taking place during that initial pre-treatment phase resulting from, you know, the alkaline ozonation test alone.

The spiked water test resulted in a decrease in total organic fluorine with increases in fluoride concentrations. Additionally, increases were observed as some PFAS degradation products such as formate, acetate, sulphate and trifluoroacetate. The initial results from the air-sparging test show, you know, increases in PFAS from the apparent gas phase that’s correlated with the increasing sparging time for the spiked water test. But the testing, as I mentioned, on the groundwater, did not result in really any appreciable amount of PFOS being stripped and just sparging with air. So a follow-up test will include, you know, the use of ozone sparging to evaluate the removal mechanism during just that low pH treatment step. It is also likely that PFOS is being removed from the solution with the organic molecules and the industrial groundwater at low pH and resulting in PFAS really not being detected and observed in that gas phase.

But overall, you know, studies combined with what previous authors suggested in the literature that, you know, alkaline ozonation might be a valuable option in combination with other technologies for PFAS treatment. Some of the other researchers have suggested that, you know, this technology conditions enhance PFAS degradation are resulting from a free-radical reaction pathway such as hydroxyl radical being the primary degradation mechanism. But, you know, our published and peer-reviewed studies here and follow on air sparging test suggests that destruction via oxidative processes might be taking place, but it’s certainly not the dominant mechanism. And, you know, this work really highlights the thought process and evaluation that needs to be carefully considered when determining if, you know, a treatment is actually destroying PFAS versus just simple physical removal or adsorbed removal.

So, in summary, we do see that, you know, some emerging contaminants such as PFAS and 1,4-dioxane are being detected in water bodies and, you know, are currently being evaluated for federal and state regulations. You know, typical sources are related to consumer products, industrial processes, and manufacturing operations. And as we’ve presented today, there are a number of treatment technologies available including, you know, chemical oxidation and biodegradation that are demonstrated for 1,4-dioxane and adsorbed technology such as activated carbon and, you know, ion exchange resins for PFAS. There are emerging technologies that are yet to be demonstrated but do show promising preliminary results. And, you know, as we’ve recommended here, treatability studies are quite valuable in providing insights on treatment technologies effectiveness, dose optimization, as well as a proof of concept for some of the more emerging technologies. And with that, I will hand it over to Dr. Kristen Thoreson with REGENESIS.

Kristen: Great. Well, thanks so much to Ryan and Sophia for joining us today and giving us some really nice examples of the use of treatability studies. And, you know, I think a good appreciation for gaining more information to help the decision-making process. So really great to see that, especially with these emerging contaminants, those that are hard to treat. And as I mentioned, those we just are still learning a lot about. So it’s great to see those kind of studies coming through.

I’m going to just spend a couple of minutes staying on the topic of PFAS. And I think staying with a similar theme, I want to focus a little bit about some of the thought process that we also go through at REGENESIS when we’re looking at a PFAS site and the approach we’re taking to address those PFAS contaminations in groundwater. The thought process being that, you know, more information, helping us understand the site a little bit better, really towards the goal of having more success, having the reagents work as expected, and getting the results we’re all after.

So my outline is kind of described here, but I’ll just jump in here. Just to briefly describe, you know, this is the process that we use at REGENESIS when we’re looking at a PFAS site. Obviously, PFAS is very challenging. The options we have in our toolbox are still limited, although expanding. As, you know, Ryan pointed out, there’s a lot of new stuff coming through. But what we’re looking at is an in situ approach. And the idea here is really to develop and to install a permeable reactive barrier. This illustration shows you what that can look like. And the idea is to really cut off a plume, prevent it from further migration, keep it out of sensitive receptors, reduce that risk that’s associated with those contaminants as they continue to move. And so, those barriers could be closer to storage farther down next to a sensitive receptor. There’s a lot of flexibility there. And I think that’s one of the benefits, I’ve listed out a few benefits of this approach.

Obviously, pump and treat is a well-established and good method that’s going to be an approach that’s used in some cases, but it is a little bit limited in flexibility. So the idea that we can install a barrier using direct push or injection models does offer a lot of flexibility. There’s no aboveground infrastructure that’s required. The O&M that’s associated with that is now not required. And so, this passive treatment can be very beneficial and still can achieve low standards. And from a single application, we estimate you can get years, decades of treatment. So this is really the approach that we’re taking and talking about here today.

And the way that we can do this, the way we can install a permeable reactive barrier is using a form of activated carbon we call PlumeStop. And it is activated carbon, the key features that we process it, mill it down to the particle size of the activated carbon, it’s quite small on the order of 1 to 2 microns. And that makes it small enough to be able to fit through the pore throats of the soil and be able to spread out. So we can install that barrier, get a good distribution, make sure there’s no gaps. There’s some additives in there that helps with that process as well, but that is really the key feature there is its ability to be installed. And then it acts like activated carbon, it can quickly absorb contaminants. It’s nice because it’s a passive treatment again, so groundwater is flowing through, you know, relatively slower, or a lot slower than in the case of pump and treat type systems where you have not as much contact time. So it does a good job of removing contaminants from the groundwater to clean up downgradient.

So this illustration shows that process as well. You can install the barrier, you have contaminated groundwater moving, in this case, from right to left. And the idea is just to have it pass through that barrier and come out the other side clean. Obviously, this is not a disruptive technology, it is sequestering, it’s removing it. But there’s a lot of benefits here too. And again, that ability to reduce the risk, remove those contaminants in place without generating waste above ground.

Now, the place I’d like to spend a bit more time on is really this process that we go through prior to an application, again, to ensure success, make sure we’re using the technology in the best possible way to get the best possible results. But before I jump into this list here, I just want to highlight the fact that everything that we are doing today is a result of the research and development we’ve done over the years, and also just the experience we have. Because some stuff we’ve had around now for over seven years since we first launched it. And we certainly have learned a lot in that timeframe as we were in the lab doing tests and understanding that. And so, I just want to highlight that, you know, we’ve learned a lot, we have a good understanding of the important questions that we need to ask and we need to know before we go into a site, again, with that goal of what considerations we need to know to successfully implement it.

And, of course, research never really stops, especially when we have these emerging contaminants that are challenging in their own way. We need to continually be thinking about them and learning how they interact with these technologies. And so, like so many companies, we have a team that is really keeping an eye on PFAS, focused on PFAS. And again, that understanding towards how it works with our technologies and what we need to know. And so, this is the team we have really focused on that right now. We’re really happy that recently we had Dr. Yen-Ling Liu join us. And she comes with a lot of PFAS experience focused on groundwater surface type contamination associated with PFAS.

And, of course, you know, we are doing some research, but we’re also partnering with a lot of groups as well. I just want to comment on that, that there’s a lot of government-funded academic type of research going on that are evaluating some stuff and having more time to spend looking at these questions and what we have time for at REGENESIS. And so, there’s a lot going on. And there’ll be a lot coming out from these different groups from both the lab and the field. And we’re supporting these as we can by providing product, providing some insight, helping with application. But we’re excited to have all these groups working and looking at PlumeStop, especially as it relates to PFAS as well.

Okay, so now, just to focus a little bit, again, on the process. This is some key steps that we go through prior to implementing PlumeStop at a site where we’re using PFAS. And again, this is focused on that specific technology and contaminant. However, we do some or many of these steps for a lot of different technologies, because really taking the time to better understand the site and how the reagent is going to work at that site is essential and very useful for any in situ application. So we’ll keep PFAS and PlumeStop in mind here, but it can be more widely applied as well.

So one of the first things that we go forward with once we know the process we’re going to go for, or the technology we’re going to use is what we call design verification testing. And I should also just point out real briefly that this list is…all these topics have a lot of detail and a lot of background to them. And we can spend quite a bit of time on each one of those, I’m just going to give a very brief version of all those. If you’re interested in any one of these, we’d be happy to get you talking to the right people who can give you more in depth description of all of these.

But the first one, design verification. Really what we’re thinking about on this is we want to verify our design parameters and assumptions. And so, obviously, there’s been a lot of site characterization that the consultant brings, and they know more about the sites. We’re really working closely with them throughout this whole process. But we’re thinking about it in the terms of how is the reagent going to get in contact with those contaminants. And those, sometimes we need a few more questions or knowledge gaps to be filled, to really understand that before we go forward with the actual injection. And so, helping to just further identify the contaminant transport zones. You know, where are they flowing? We want to make sure that we really target the treatment zone appropriately with the reagent to have a better chance of having contact, which ultimately will lead to better performance.

And so there’s a wide range of things we might do ahead of an application, but this is a kind of a shortlist. A lot of it has to do with understanding the soils vertically and throughout the treatment area, understanding those high-perm zones, low-perm zones. So sometimes just taking a couple of extra soil cores, looking at the soil type, thinking about where the contaminants are really stored versus where they’re transported. Also clear water injections can really give us a lot of information to make sure that we know we’re going to be able to inject the volumes that we plan to inject and make sure we’re not too far off on that.

And then closely aligned with design verification testing and often done concurrently with that is a… Another tool we’ve been working on it’s FluxTracer. And it’s a vertical profiling tool. So we’re going after some of the same questions that I just described. But this is a new tool that we have been working to develop so that we can use this on many sites. Because we’re really excited about this data and we know that it’s really important for the performance. And so, I’ll just start this off by saying, please, if you want to know more about this, next month’s webinar, December’s webinar is going to be talked about this in depth. And so there’ll be a lot more information there that you can learn about these.

But basically, this is a Passive flux meter tool that we’ve been working on at REGENESIS that works to vertically delineate a site by directly measuring the contaminant mass flux, and the contaminant and the groundwater velocity in order for us to really understand the vertical target treatment zone. Again, understand where the contaminants are being stored versus where they’re being transported. And that, again, helps us identify where we really want to be targeting that reagent placement to get the best possible contact. And again, there’s a lot of features here that I’d recommend tuning in next month. Because these are designed to be simple to use. There’s no infield that some of the required field personnel can be installing them. And then they’re sent from our REGENESIS lab and sent back to our REGENISIS lab for all the analysis and reporting. And again, our goal is that we want these to be used on many sites, because this data is really important. It’s a key piece of data that we use as we go forward with the design process.

And that brings us to the design process. So the DVT and the FluxTracer really culminate in, you know, putting the pen to paper to come up with actual design or a PlumeStop, where we’re going to put the points, how much we’re putting in, you know, what does it look like at this particular site, given the different contaminants? And that whole process, an additional tool that we have that has been developed over the years is a modeling tool called PlumeForce where we can use a lot of the data that has come out of the lab. So understanding how the dose response or the contaminant-specific isotherms. So, you know, how does PFOS versus PFHxS adsorb to PlumeStop? Those are all taken into consideration and can be used in this model to really help us estimate, understand what the prediction of an application will be.

There’s other features too, when you have a mix plume, like almost all these sites are, you can take into account what the expected competitive adsorption between the contaminants will be. If some of the contaminants can degrade, we can account for that as well. So it just gives us a good ability to look more closely to site and understand, again, how the performance may look over time and make sure that we’re scaling it in appropriately. And then, obviously, a lot of other things that you’re always considering for any application, the soil type, again, that mass flux, you know, what doses you’re actually putting in, those all come into play here as well.

And so, once we have that in hand, obviously, we’re going to the field and starting to do the injection. And now if we just go ahead and…you know, don’t do all this hard work upfront, but don’t think too hard when we’re doing the application, we could still miss the mark. And so, you know, at REGENESIS we have our field services crew, REGENESIS Remediation Services or RS that exclusively applies PlumeStop. And they have protocols, when they are doing an actual application, to take the time to confirm that the application is going as expected, that we’re getting that distribution, that we’re installing it correctly. It is a lot of taking, of course, groundwater samples, temporary wells, things like that.

And so an example here, this is from a site where the target treatment zone was between 15 to 27 feet. And so you can see how the chords were lined up here. But we are certainly getting some PlumeStop in that zone. However, given that this is a pretty homogenous soil type, we were expecting to see it across that entire 15, 27-foot zone. And so, we can see here that we really did not have the distribution that was anticipated here. And so, our team is in constant communication with the designers and other site personnel. And they’re making adjustments in real time in the field to ensure that we’re getting that distribution. And so, after a couple of more adjustments, they continue to go until they get this kind of distribution in the field. And then they can feel pretty confident going forward with the rest of the application. Some other samples that they’ll take are water samples from the wells, if there’s a well in the area. Again, we can monitor as PlumeStop is moving in the ground, again, to ensure that we’re getting that distribution. And so, these are just some examples of other tests that they also can do in real time.

And then finally, you know, the technical review of the performance. So we want to be looking at the data as well as data comes in from the different wells in the area. And a key aspect of that is looking to see if it’s performing as expected, if there’s any indicators that maybe there’s some patchwork that’s needed, or any other kind of, you know, just review of that data is really going to be beneficial to make sure that it’s behaving as we’d expect it to and we’re gonna get the long-term results that we’re anticipating.

So finally, I’ll just very quickly highlight a couple of long-term sites where PlumeStop has been used to address PFAS. Just a quick comment that it is being adopted. We have experience putting PlumeStop in a number of sites. This slide actually gives a nice demonstration of the variety of sites that we have used PlumeStop to address PFAS. Which is great, because we’re learning a lot. Again, there’s always gonna be different co-contaminants, different nuances, different challenges at each of these types of sites. And we’re getting a good spread of the different sites we’ve actually applied to that so far.

But, you know, I think the interesting question is certainly how is the application holding up long-term? I mentioned at the beginning that from a single application, we’re expecting years to decades of treatment. So obviously, the longer-term results are really what are interesting. That’s the ones that we want to keep an eye on. So there’s two sites, the older sites that we have running so far. You may have seen these being presented, I’m not going to go into any background of those sites at all. There are some journal articles that you can go to if you’re interested in some more information, and I recommend going there.

The only thing I’ll point out here is just the relative concentrations. So PFOA and PFOS were the only PFAS contaminants that were actually analyzed for prior to this application. So you can see that they’re in the hundreds of parts per trillion, the single digits per billion range. And this is the range the wells where PFAS was actually detected. I’ll show you the results from MW1 down here. And we’re very happy, we’ve recently, just a couple of months ago, got the 5.5 year data point, 5.5 years since PlumeStop was applied. And it’s been holding up great. We’re seeing continually non-detect results. The only, again, background baseline concentrations we know are PFOA and PFOS, but other contaminants, PFAS contaminants are being analyzed for as well and we haven’t seen those detected.

So this is our longest running site. And we’re really happy to see that kind of longevity coming forward. And then the second longest running site is Grayling Airfield in Grayling, Michigan. And so, again, I’m not going to go through these details except to point out this was, you know, commingled with PCE and is, you know, approximately 130, 150 nanograms per liter of total PFAS.

And this is the arrangement, just to give you an idea of what we’re looking at, where the results are, here’s an upgradient control well. Groundwater is moving from top to bottom in this diagram and the barriers in place here. So we’ll look at results from these downgradient nested wells. And again, the site’s about 3 years old. Recently, a couple of months ago, we got the 2.7 year data point in and we also have seen the results hold up really nicely here as well. This is the concentrations coming into the barrier. So those are staying pretty steady. And then what is, you know, downgradient has remained non-detect, and we’re certainly meeting Michigan’s MCL requirements there.

So just, you know, in summary, I just hopefully highlighted the process that we take to, again, ensure that we’re getting good results, we’re using the reagent as its intended for best possible results. So a number of steps are taken there. And we’re excited to see PlumeStop being used on these sites and seeing it as a proven technology with, you know, these longer-term results coming in from a single application.

And so with that, I think we’ll have time for questions for Ryan, Sophie, and myself. These links on the screen here will take you to our LinkedIn profiles, if you’re interested in contacting us. So thank you for your time.

Dane: All right. Thank you very much, Kristen. That concludes the formal section of our presentation. So at this point, we’d like to shift into the question and answer portion of the webcast. Before we do this, I just wanted to acknowledge we are running over the hour for this webinar. We don’t want to cut short any of this really valuable information. And we do have some great questions. So thanks to those of you who will be staying on with us. If you do have to hop off, just know we will be sending out a link to the recording right after the webinar, which will have the complete webinar and Q&A. All right, so let’s go ahead and circle back to the questions. So here is a question. The first one is for Sophia. And it is, what are the considerations when scaling up treatability study results for field implementation?

Sophia: Ah, yes. Well, certainly, you have to bear in mind that what you’re doing in the lab is under optimized conditions. We have ideal mixing, we have usually warmer temperatures. You definitely need to bear in mind that whatever is happening in the lab is going to happen much more slowly in the field. And then a key thing is that, you know, you’re only going to see results as good as what you saw in the lab, if you’re able to implement it successfully. So I would say the treatability study is half of the puzzle. And the other half is how are you going to get the material in the ground successfully so that it actually disperses into the entire area that you have to treat? And that I’m guessing is a whole other webinar or series of webinars. But that is a key consideration when thinking about moving from the lab to the field.

Dane: All right. Thank you, Sophia. So we have another question here. This one is for Ryan. And Ryan, the question is, during the PFAS portion of your talk, you mentioned that the client was interested in evaluating destructive technologies. So what were the disruptive technologies that you looked at for this site?

Ryan: Yes. So, you know, our team has engaged with, you know, quite a few vendors and academics to really evaluate PFAS treatment technologies, passive and destructive, that are, you know, at various stages of commercialization and scalability. But for the destructive technologies, we’ve looked into, you know, plasma treatment with two universities and supercritical water oxidation with a vendor. And in general, the technologies tested resulted in significant PFAS removal from the impacted water source with, you know, greater reductions observed for the long-chain PFAS as compared to the shorter-chain PFAS. The initial results suggest that disruptive technology exists, but certainly will require a careful evaluation to fully understand byproducts formed during the process, transformation pathways, as well as the overall associated costs for full-scale implementation.

Dane: All right. Thank you, Ryan. So we have another question here. This one is for Kristen. And Kristen, the question is, are the FluxTracers currently available?

Kristen: Yeah, a good question. Again, I don’t want to steal the thunder for next month. I definitely encourage people to tune in next month to get all the information on there. We are currently using them. Absolutely. And the information provided next month will have all the details on exactly what they are, how to get them, who to talk to, and all that. But yeah, we are using them currently on sites as we speak.

Dane: All right. Thanks, Kristen. So here’s another question. This one is for Sophia. Sophia, the question is, DHCR bacteria, they’re known to degrade chlorinated ethenes. So is there a type of bacteria that is responsible for the 1,4-dioxane biodegradation?

Sophia: Oh, yes. Well, actually no. So DHCR is a class of bacteria that, you know, are very important in the reductive dechlorination of chlorinated solvents. But for 1,-4 dioxane, we find those monooxygenase genes actually spread amongst a wide variety of bacteria, and even fungi as well. So if you’re going to assess the potential for 1,4-dioxane biodegradation, it wouldn’t be as simple as looking for a class of bacteria such as that the [inaudible 01:06:45], which you look for using a 16S mRNA target for the molecular biology. For 1,4-dioxane, you have to target the functional gene, the monooxygenases that break that ring. And so, although they’re spread amongst a large population of different kinds of bacteria, you can actually look for the functional gene for that process or for that enzyme. And so it’s related, but it’s not exactly the same as looking for just DHC for chlorine and solvent degradation.

Dane: All right. Thank you, Sophia. We have another question here. This one’s for Ryan. And Ryan, the question is, about how long does it take to perform a PFAS column treatability study?

Ryan: Yes. So, you know, the length of time it takes is going to, you know, depend on really a number of things, including the number of amendments that we’re testing. Also, what else is, you know, really in the water that could consume the media, in addition to PFAS, that will, you know, drive the actual, you know, break through. And, of course, you know, turnaround times at the analytical lab on all the analysis. But in general, in my experience, this can take at least three months and go up from there. I mean, running rapid, small-scale column test is a good approach if the media can be, you know, crushed, so that the columns can be operated at a bit of a higher flow rate. But it’s quite variable, and it’s really based on the influent water quality that I’ve mentioned.

Dane: All right. Thanks, Ryan. So this is another question for Kristen. And Kristen, and the question is, do you expect the sites to eventually have breakthrough of PFAS contaminants?

Kristen: Yeah, that’s a good question. Obviously, again, this is not a disruptive technology. So there’s nothing there that’s breaking it down. So there is an accumulation happening in the barriers that we’re installing. You know, the real answer, of course, is that it can be complicated. There are some things to consider on a given site. One is if the source has been dealt with or not. You know, if the source has not been dealt with, then yes, absolutely, the barrier will eventually fill up and will break through, and then we’d have to consider what might happen next. If we install another barrier downgradient, it’s probably the best thing to do.

But, you know, there’s a lot of work going on in source areas as well. And so that source has been taken care of and it’s depleting over time, then, you know, your influent in the barrier is gonna be decreasing over time. And [inaudible 01:09:32] maybe enough, covering an area to certainly extend the longevity of how long it would take to break through. And actually, it could be a very, very long time in that case. So it’s going to depend a little bit about the site, what’s there, any co-contaminants, and how it’s been dealt with in other areas of the site as well.

Dane: Okay. Thanks, Kristen. So this is another question for Ryan. Ryan, the question is from your presentation, the anion exchange resin breakthrough curve shows a peculiar trend for PFBA. Is there any idea as to what could have been going on that contributed to these results?

Ryan: Yeah, good question there. So for the data values really above that C, over C naught ratio of one, the effluent concentration was greater than the influent concentration of it. And additionally, some of the observed concentrations for the short-chain PFAS, particularly PFBA, they were right around the detection limit with that range from 40 to 70 parts per trillion, and really, you know, gave rise to that peculiarity of some of that, the breakthrough curves that we show there.

Dane: All right. Thanks, Ryan. So, this is another question. And this one’s for Kristen. The question is, Kristen, you showed a picture of samples taken from a well that are black, is it problematic that the water has PlumeStop in it?

Kristen: Right. So those samples, yeah, very well could be from a mountain well in the area, or they could be from temporary monitoring points. You know, the way we see it is that the mountain well can and should be representative of the rest of the aquifer. And our goal is to be filling up PlumeStop across that aquifer. And so seeing it in the well is actually a good indicator that we’re getting the distribution, the spread, and that’s going to be filling up as appropriate. So it’s a good thing to see that. We also know that because we’re installing under low pressures, that it’s not a representation of a sort of high-pressure application where that’s now a preferential pathway. It is just representative of the rest of the aquifer.

So it’s not a problem. Something that could happen there is just that at that moment when the water is still black, you can’t send that to the lab. But we do know that the PlumeStop will clear up typically quite quickly. And if not, we have some means to help that along. So that is the only thing is that you wouldn’t be able to send a sample that day to the lab if the water is black, because it would impact the results that you would see.

Dane: All right. Thank you very much, Kristen. So that’s 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’d like to learn more about services from GHD, you can visit ghd.com. If you’d like to learn more about remediation solutions from REGENESIS, please visit regenesis.com. Thanks again very much to Dr. Ryan Thomas, Dr. Sophia Dore, and Dr. Kristen Thoreson. And thanks to everyone who could join us. Have a great day.