Webinar date: April 2, 2020
Watch the webinar recording below for an in-depth look at PFAS site type considerations, sampling, and fate and transport with regard to contaminated site investigation and cleanup.
For more information, contact:
Mitch Olson, PE, PhD
Hi, my name is Kara and I would like to welcome you to part 2 of Trihydro’s three-part PFAS webinar series. Today's session is titled Site Characterization and Remediation Considerations. We have two speakers today. First, Mitch Olson, Trihydro’s PFAS expert will discuss site characterization. Our guest presenter, Jens Blotevogel of Colorado State University will delve into PFAS remediation. We're excited to get started.
Dr. Mitch Olson is an environmental engineer who plays a technical advisory role in a variety of projects involving soil and groundwater are impacted by petroleum hydrocarbons chlorinated solvents and emerging contaminants.
Mitch is an environmental engineer and emerging contaminants subject matter expert at Trihydro who is actively involved in various PFAS-specific research programs, including the Interstate Technology Regulatory Council PFAS team and various projects within Trihydro involving PFAS and AFFF. Mitch has a bachelor’s degree in chemical engineering from the University of Minnesota Duluth, and Master and PhD degrees in environmental engineering from Colorado State University.
I’d like to thank everyone for joining our webinar today this second webinar in the series includes site characterization and remediation considerations for PFAS impact insights. The first webinar titled A Deeper Dive into the PFAS Problem provided an overview of PFAS and aside from some of the introductory material, we will do our best not to repeat content. If you missed the first webinar but would like more information on PFAS uses, sources into the environment, chemical properties, and fate and transport, it might be good to check it out.
As with all things PFAS, many topics in this webinar could really fill an hour-long presentation in and of themselves. Please feel free to ask questions as Kara alluded to or reach out to Dr. Blotevogel or myself. If you have any questions or would like to further discuss any of these topics or email addresses are provided at the end of the presentation and these presentation slides will be available for download.
The PFAS summary sheet is also available as a handout. This is the same resource provided in the first webinar. for some of the more commonly analyzed PFAS, this sheet includes supporting info on where the chemicals fit into the PFAS family tree as well as chemical names, acronyms, and chemical structure and analytical methods that are associated with some of these PFAS compounds are also included and we will be referring to the handout occasionally during a presentation so it might be good to open it up and keep it available.
Please open the handout and keep it available as shown in your screen. The handout is available through a link on the Trihydro website or you will find a pdf on the lower right-hand corner of your screen.
To set up our discussion today on PFAS site characterization and remediation. We'll start by reiterating a few key points from the first webinar. PFAS is an acronym for this term Per (and poly-) fluoroalkyl substances. This is a blanket term that includes all of these compounds which may include an estimated 3,000 to 10,000 individual compounds, one example of which is shown here on the upper right corner of your screen. This is perfluorooctanoic acid or PFOA. This is one of thousands of PFAS compounds one of two compounds.
For which the EPA has establish health advisory levels as a few common characteristics with other members of the PFAS family, which will discuss briefly here this webinar these include both the fluorinated tail and a non-fluoridated head of the compound distinguishing features as fluorinated tail include the carbon-fluorine bond strongest bond in organic chemistry, very difficult to break. The fluorinated tail also is both hydrophobic and oleophobic it repels water and oil repels.
Basically everything it is this characteristic that gives PFAS a lot of useful properties and part of the reason why they're so widely used. Another characteristic of PFAS compounds is this non-florinated head which may be polar and hydrophilic attracted to water and this is this is the feature that may give PFAS some of their high mobility in water despite the fact that their tail is hydrophobic. PFAS are an emerging contaminants that three things are going they need to come the distinguishing the defining emerging contaminants of our generation.
PFAS are very widely used by industry and consumers some examples are shown here in the lower right portion of your screen with some of the more common uses include as a firefighting foam. AS a fire fighter foam they are used be flammable liquid form of a hydrocarbon type fires also used in the manufacture of nonstick cookware food packaging widely used in consumer products and water or stain repellent type fabric surfaces, ubiquitous use of PFAS has led to widespread environmental
facts and the scale of these impacts remains largely unknown. Once released into the environment PFAS are very difficult to remove and this is due to both their chemical stability and their potential high mobility once released into groundwater.
AS related to PFAS site characterization intermediation their unique characteristics challenges in different ways than conventional contaminants such as petroleum or chlorinated solvents. in terms of site characterization. Some of the unique challenges of PFAS include the very low levels of interest, health advisory levels in the part per trillion level. the fact that they're often released as a complex mixture and cross contamination risks due to the fact that PFAS present in so many common sampling materials lack of analytical standards is another big challenge and we'll talk more about that in this webinar. Remediation provides an additional set of challenges related to PFAS can be summed up briefly here conventional water treatment. That works. Well for TCE Benzene other conventional contaminants does not work. Well for PFAS consideration is really the only commercially available means for PFAS destruction more to follow on that later in the webinar.
We will elaborate on these concepts as we move through this agenda starting with addressing this question. What's driving the need for PFAS site action? but within the site characterization umbrella will talk about sampling and analytical considerations and following this Dr. Blotevogel will speak for the second half of this webinar and he'll address destructive versus non-destructive techniques for PFAS remediation, use of treatment trains as a means to improve treatment efficiency, and whether there's hope for biologically mediated degradation of these compounds. Factors starting PFAS site management decisions are complicated given several factors including the current state of regulatory flux, limitations and currently available analytical methods, and limited data on everything from occurrence in the environment to toxicology really for all except for a very early to these small number of this large class of compounds comprising the PFAS family. There are several considerations for whether to take proactive measures at a potentially impacted sites or whether to wait and let the dust settled.
So to speak reasons to accelerate the process shown here on the left hand side. Why take action now? federal state regulations and orders will address this in more detail in the next slide. Due diligence related to property transfers incidentally the ASTM standard for site assessment currently would not recognize PFAS as REC or recognize environmental condition since PFAS are not currently declared as a hazardous substance under CERCLA. This may vary on a state specific level where clean up levels have been established in certain States. This status is likely to change both the ASTM perspective and due to the fact that PFAS are being revisited as potentially becoming a hazardous substance under CERCLA. The number and magnitude of lawsuits associated with PFAS has also been increasing from tracking headlines associate these lawsuits some involves some very substantial dollar.
It's on the order of a billion dollars. and the idea my message control is identifying impacts and having an ability to implement a response before impacts become discovered and become publicly available information. reasons to wait may include the current state of regulatory uncertainty, the lack of approved laboratory methods for any media aside from drinking water, which is a gaping hole and the currents like your characterization process, and also the idea of ambiguity or uncertainty in PFAS data interpretation. Both of these stem from these the first two bullet points mentioned here as well as the idea that regulations that have been established on a federal or state level are only apply to a relative very small number of PFAS compounds often just PFOA and PFAS. how to interpret data for other PFAS compounds remains largely uncertain or unclear. As a driver for site action we will briefly discuss the role of regulations and I'll note that these will be covered more detail in the upcoming third webinar of the series. EPA action towards PFAS regulations has been occurring but they making slow progress. Things have been done. EPA established health advisory levels (HA) in May of 2016, these health advisory levels 70 parts per trillion (ppt) for 2 PFAS compounds - PFOA & PFAS which applies to concentrate.
The two compounds combined as well. No healthy advisory levels on a federal level to date for the remaining members of the PFAS family also worth noting these health advisory levels are not enforceable. These aren't MCL is not maximum contaminant levels that that are more significant drivers towards site action their advisory levels at their core. The PFAS action plan was initiated by the EPA were made public by the EPA in February, 2019, which included the started.
a process towards regulation of PFAS and this included the process towards establishment of an MCL hazardous substance negligent declaration under CERCLA, and also including PFAS in a toxics release inventory or TRI. Regarding establishment of the MCL just recently in February 20 20, the EPA issued preliminary determination for PFOA and PFOS to regulate them under the Safe Drinking Water Act. This initiates the process towards establishing an MCL, although there are major the process could take multiple years regarding the toxics release inventory that just because became a real thing in December of 2019. 170 PFAS compounds are now included in the TRI list of chemicals that should that need to be reported when released to the environment. State level responses have been relatively piecemeal.
There are currently 23 states with PFAS regulatory standard illustrated on this table here on the right-hand side of your screen, I understand the print this little small here, but the key idea is just to take a brief look at the layout of how different states have responded. States shown in red have adapted PFAS standards more than the EPA Health advisory levels of 70 parts per trillion. The states shown in blue here have adopted the EPA levels, green states have adopted advisory levels that are higher than those EPA standards. Some of these states have enforceable standards, but many of these states are following the EPA’s lead to this.
And using an advisory level, because state senate are evolving so quickly the interstate technology regulatory counsel ITRC has been tracking state standards. There's a link provided here to the ITRC table. It's being updated on a monthly basis. It's a very useful resource to keep an eye on how things are evolving.
When the decision is made to evaluate a site for potential PFAS impacts PFAS investigation follows a different set of rules than those that have been developed for conventional compounds of concern. Starting with consideration for sampling objectives. list of sampling objectives shown here is similar to that for other conventional compounds will really just make a few comments about considerations under these objectives specific to PFAS. the image shown here, right very briefly.
This comes from the first webinar if you'd like more information on PFAS transport the environment refer you to that to that first webinar, but to provide some context for this discussion of the different transport pathways PFAS may be susceptible to atmospheric transport on regional and global scales. other transport mechanisms may include surface spreading, stormwater discharge, as well as infiltration into shallow soils or into ground water. Once in groundwater, PFAS are known to be very mobile plumes have been observed to extend for several miles.
Moving through these sampling objectives the idea of drinking water protection stems from the idea that a lot of current PFAS sites. the objectives, the need for site characterization originates from detections in drinking water sources drink water supply wells and a lot of time this may drive an outside in approach. We're starting from the impacts downgradient moving towards trying to identify where the source may come from.
This is different from a lot of probably the conventional approach at a lot of sites that have been evaluated in times past for other types of contaminants. This is by no means always the case for PFAS.
However, but just because it's early in this process many potential PFAS impacted sites have not undergone much of these this sampling process is outlined here. Preliminary assessment at potential PFAS sites may include a basically a desktop study looking at if there are potential sources at the site and if there are those that there may be some supplementary investigation collecting some base level samples, perhaps some shallow soils and potential Source areas or groundwater type samples to identify if there's any groundwater impact ground water soil. and then moving down the list plume delineation as mentioned for PFAS can take on a different level of a challenge because PFAS are so stable.
And so mobile in the environment that plumes can extend for really extended distances perhaps longer than is typically observed for chlorinated solvents and even more so when compared to hydrocarbons. Source characterization may be conducted to identify if there's any ongoing or residual sources for PFAS that may need to be addressed. and remedial investigation sampling that may be done to support ultimate design of a remedy and it's worth noting here very few sites potentially impacted with PFAS of have made it to this stage yet.
And next we'll discuss PFAS sampling approaches and analytical methods will focus here on groundwater. But many of these considerations such as material compatibility will also apply to other media types.
List of groundwater sampling methods that apply to PFAS are shown here. For low flow type sampling, a peristaltic pump or bladder pump may be used. A peristaltic pump is generally ideal and that all the equipment that comes to contact with the sample, all the materials that the tubing, is either disposable or dedicated. A bladder pump, for instance by contrast, can be used for wells where the depth of ground water is too deep for peristaltic pump to work.
The challenge of a bladder pump is that it will need to be decontaminated between each sampling location and the decontamination procedure adds another level of rigor than what is typically needed for other types of contaminants. The bladder pump, needs to be certified as PFAS free most vendors can provide a PFAS bladder pump at this stage both the peristaltic pump and motor pump should use HDPE tubing. Within the body pump the bladder and O-rings need to be replaced within each within the pump within each location.
And between each location and to the specialty contamination concerns these include the need for a final rinse using water that's certified to be PFAS free. A jug of distilled water from the neighborhood convenience store can't be considered to be PFAS free until it's actually been tested. Bailer is another acceptable sampling method. No-Purge approaches may also work well for some PFAS sites examples may include a Hydra sleeve or snap sampler somebody advantages of
No-purge type approaches of the lack of IDW or investigation…that they would produce and the fact that all the materials that come into the contact with the sample are disposed of disposable of dedicated equipment just always preferred for PFAS sites and if there's doubt and in terms of whether and equipment is PFAS friendly and equipment blank would be recommended materials and equipment that are compatible is where we need to start getting further into the weeds. This is where things really get specialized for PFAS sampling.
As we’ve regularly noted, PFAS are in so many products that but in daily life and then it as part of the sampling routine that extra consideration needs to be given that there's not some source of contamination or cross contamination through to these materials as noted here beware of PFAS presence in common sampling materials and personal care products on the next slide. We've got a table that gives a brief overview of a PFAS considerations.
Given the emphasis on using PFAS compatible materials really worth also emphasizing that how health and safety rules should never be compromised for the purpose of collecting a PFAS specific rule if there's some discrepancy between health and safety rules for site and the PFAS materialist. It may take a little upfront effort to plan around this but health and safety rules should never be relaxed just for the purpose of collecting vs apple also noted here quality control considerations for PFAS sampling.
Extra equipment and field equipment should be planned on as part of a sampling event because there are so many potential cross contamination sources, and then also the idea of using lab surprised that supply PFAS free water for collecting these blanks.
This table provides a very brief overview of PFAS compatible sampling materials and equipment. So again, what will briefly discuss the stable but note that this table is not comprehensive more details are provided elsewhere including through links provided in this presentation that's available for download to other guidance documents that provide a more thorough list of PFAS compatible materials, but this table here shows a list of prohibited or restricted items as pertaining to PFAS.
Prohibited versus acceptable items the different categories shown in this table include field equipment clothing and PPE sample containers decontamination and even food considerations, so very briefly equipment that should be restricted includes fluorinated polymers or plastics. This includes such as Teflon, which is common in a lot of present a lot of common sampling materials including as a liner for caps and a lot of sampling bottles.
HDPE is the preferred plastic of choice for sampling materials and equipment and sampling containers as well regarding LDPE is okay to PFAS sampling site as long as it doesn't contact the sample directly LDPE isn't a source of PFAS contamination per se but PFAS do tend to stick to LDPE. So any sample media that may contain PFAS once it's contacted LDPE concentrations can be affected and that can lead to cross contamination as far as clothing.
And PPE waterproof or stain treated clothing may be treated with PFAS. Well laundry clothing defined as having been washed 6 or more times is the typical recommendation for PFAS sampling guidance. And then also haven't been watered without fabric softener. Although recent research has suggested that fabric softener isn't a source of PFAS for personal care products should be avoided on the day of sampling to the extent that that's possible practical select sunscreens and insect repellents are okay.
Health and safety considerations again come first. These are needed they should be used.
But they shouldn't be applied at the location where samples are being collected. This should be done. Well ahead of time and hands should be washed afterwards for sample containers LDPE or glass both sort tend to absorb PFAS. And so they shouldn't be used and as noted for polymer line cap should also be avoided HDPE or polypropylene are the recommended simply materials for equipment decontamination. Decon 90s on the prohibited list Alconix or Liquinox are okay as far as a water source for decontamination.
And untested water from an on-site well should be avoided it can never be assumed shouldn't be assumed that water is PFAS free just because it's clear a local water. Supply known to PFAS free really needs to be used for that final decontamination step and then food considerations as noted Professor present a lot of food wrap and materials. They should just really if possible not be present at the sampling site bottled water/ hydration drinks in the staging area are okay.
But once again, they should be kept away from the direct area where some to be collected some of the material restrictions as we talked about here. The recent research has suggested that some these material is fictions May. In fact be overly cautious to the point of being unhelpful. There's a quote here from Rodow et al in a recent publication that there are no possible scenarios for many of the prohibited materials to come into meaningful direct contact with water and that a lot of materials in this list. In fact were initially mentioned in guidance a long time ago and keep getting picked up and carried forward to recent guidance.
This idea also needs to be balanced with the idea that the cross contamination risk is very real PFAS are present in a lot of sampling materials. And these previous results are likely to be scrutinized at a different level.
So before being too overly relaxed about deciding that PFAS are present in any of the materials on the prohibited list the degree that PFAS results may be looked at too closely at close more closely and at a different level than other samples really does need to be considered and whether the pathway between the material of concern that's being used in PFAS should be considered. So there's a lot here and try to kind of summarize the key points in a best practice recommendations. This list here attempts to summarize the key points health and safety first review the product the standard operating procedures for PFAS sampling with the project team in detail. It is for this reason that that we conducted a full day sampling event.
We brought together our core past project team of about The visuals and sat down went through our internal sop in detail really on a line by line basis and did Hands-On training to make sure everybody is well up to speed and informed on all the reasoning behind the rules for PFF sapling. This is an important step when you're establishing a PFAS sampling team planning ahead and allocating sufficient time.
If you're rushed it's going to really challenge the ability to collect samples in the correct manner following protocols is of course going to be very important this planning steps may also, Consider exceptions or maybe adaptations is a better word than exceptions here for a health and safety protocols.
To the extent that the worksite area can be simplified any clutter remove just minimized the barest Necessities removes the chance that there's anything there that could cause inadvertent cross-contamination of samples. And then one of the most basic PFAS 101 sampling should rather say change gloves often.
There's some additional guidance here. These are links to additional guidance and will give a few comments about each of these the ITRC has a guidance a fact sheet on site characterization consideration sampling precautions, very good high level overview, but perhaps could be considered relatively sparse on the details in terms of how to actually collect a sample similarly with the EPA sampling Guidance the documents cited here better for high-level. Then specific details several states have published their guidance, Michigan and, California.
Are 2 that I have a particular reference regularly other states have theirs as well and I would point you to Michigan they do have a detailed protocols and detailed guidance for many different for collecting PFAS samples many different media types. And then also we've established our own PFAS sampling. SOP, standard operating procedures, that is our attempt to synthesize the key points from these other sampling item and guidance type documents.
And now onto analytical methods for chlorinated solvents the analytical method is EPA 8260 regardless of the sample media type. Unfortunately for PFAS, there is no comparable method to the EPA 8260. The EPA has promulgated these methods shown these four upper two bullets 537 and 533. But these are applicable for drinking water matrices. Only 537 is sort of the classic the standard method dates back to 2009 updated.
Recently with some with updated methods and new compounds added to the list 533 then was released just in December 2019. So it's the new kid on the block which includes a little bit more rigor in terms of how samples are quantified and includes some of the new short chain replacement compounds which are shown here the handout includes a list of PFAS compounds associated with both the 537 and 533.
Political methods for media types other than drinking water such as ground water soil sediments. There is no promulgated. There is no EPA promulgated method at this time. So essentially to deal with this each laboratory has developed its own method. There's probably a lot of similarities between methods in these methods between Laboratories, but direct comparison is challenging these laboratory independent methods are often referred to as modified.
537 that's not modified version of the EPA method 537. I've heard EPA folks State regularly and presentations that they do not refer to these methods as s 537. It's modified 537 really modified is the key. It's a laboratory independent method another method that has been that is sometimes used as the US Department of Defense has Quality Systems manual 5.1 table be 15.
This is something that the EPA or that the Defense published a few years back. I think there were tired of the variety of types of samples. They were getting and in fact, this table be 15 is not an eligible method per se but it's a list of quality control procedures for Laboratories to follow the modified method for non-drinking water type matrices is a broad term. It can really include anything. Once it's been modified.
So analyses that falls under this the umbrella of the table be 15 can really also be considered as being a modified type method although If it was modified 537 there are additional methods that are work in progress CPA put a method 8327 for public comment last summer and they got the comments and are making modifications to that method at this time. As I understand comments were significant and the rebate is taking a while a T28 is the long-awaited method as I understand. This is the method that is attempting to be the synthesis. This is going to be the standardized.
Of the laboratory independent testing that Laboratories are conducting their also ASTM methods that are used primarily in EPA region, five. All these methods that referring to these are designed to analyze for individual PFAS compounds which can be really helpful for understanding how much of these compounds are present, but they may miss a lot of what's entirely present within a sample. There are some total PFAS methods that are available and three of the primary methods are summarized here.
These are primarily used for specialized applications such as trying to determine how well our mediation system may be working as opposed to environmental type sample analysis. One of these is the TOP assay. TOP stands for total oxidizable precursor. This is a commercially available type of analysis for this analysis essentially two samples are collected one is subjected to a chemical accident which converts the cursor compounds into the end products. The end products are the perfluoroalkyl acids.
Once again, I'll refer back to the fact she gets these opportune groups on the hand out our the peripheral alkyl acids by diverting all of all precursors, which can be an almost infinite number of compounds into a finite list of compounds to be analyzed for the total amount of PFAS in a sample can be estimated by the difference the before-and-after measured concentrations additional approaches that may be used including particle induced gamma emissions…and combustion ion chromatography…is used primarily for teletype.
Although liquid samples can be used by passing them through a carbon filter and then conducting the…analysis on that filter combustion ion chromatography involves combusting the samples and then measuring for fluorine that's produced after the combustion process both of these result in just a single total fluorine analytical result.
And before I wrap up wanted to mention a laboratory survey, we recently conducted in order to clarify our understanding. We sent a 12 question survey out to laboratories. The survey included questions such as which sample matrices are most often submitted. What is the typical PFAS count how many PFAS compounds in typical sample analysis and then analytical methods that are primarily employed for different media types.
So these charts show on the y-axis is the percentage of samples that the laboratory reported in the survey that is associated with the criteria shown on the x axis the bars show the median values from our responses from the laboratories and the error bars show the minimum and maximum values. So moving through these results the sample matrix for PFAS. If you see the lion's share of the samples are split between ground water and drinking water and a pretty even distribution between those two types relatively small number of samples for the different types of sample matrices.
He's up to this point in time. As far as the PFAS count and this refers to groundwater samples. Only. We see the one thing to note here. The error bars are relatively large this indicates the range between minimum and maximum values that we saw is pretty big. So there's a wide variety of what we're seeing here. But in terms of median values, it seems to peek out in that 18 to 25 range, which is the number of analytes typically included those EPA methods.
This slide shows methods employed for different media types drinking water groundwater and soil analysis for drinking water. Most of the samples analyzed in the last 12 months have been have used the EPA method 537.1. Although as noted the EPA 533 has just recently been released. So I would expect the balance to shift more towards that in time for groundwater. We see once again large error bars indicates that there's a pretty wide variety in types of samples.
Some got water samples have been analyzed using a 537 or 537.1, which is nominally a drinking water method, but it can't be used for groundwater. I guess provided matrix is clean enough that most of the samples are split between the modified and the qsm type of analysis and also ASTM method is used occasionally for soil method. There is no EPA promulgated method that can be used as a surrogate as eight five three seven is a pair is for groundwater.
Some more samples are split between the modified and the qsm type of approach. Once again, we see large error bars indicating high degree of variability in the results that we saw.
To wrap up a few key points from the site characterization portion…drivers towards site characterization are largely state- and site-specific.
The world awaits for EPA to come out with MCLs and designate PS as hazardous substances unique aspects of PFAS sampling include the cross contamination risks because they're present in so many sampling materials this and then relatedly the specialized materials and equipment that need to be and the fact that results of people something I'd like you to be scrutinized at a different level because of the current state of public interest in PCS potential impacts PFAS analysis. The gaping hole here is the fact that a standardized methods for environmental media are currently lacking and hope this will be addressed in the next 12 to 18 months.
Now Jens Blotevogel will share insights with us regarding the state of PFAS remediation. Dr. Jens Blotevogel is a research assistant professor in the Department of Civil and Environmental Engineering at Colorado State University and co-director of CSU Center of contaminant hydrology. He holds a PhD in environmental chemistry from CSU and a diploma in environmental engineering from the Technical University of Berlin, Dr. Blotevogel’s research
revolves around the fate of emerging contaminants and conducting laboratory and field scale experiments to elucidate their degradation in both natural and engineered systems. He's developed sustainable water treatment technologies, theoretical models for contaminant degradation prediction, and various advanced and analytical methods with a focus on high resolution accurate mass spectrometry. He's currently working on solutions for managing PFAS 1 4 dioxane, nitroaromatic compounds, perchlorate and oil and gas produced water. Jens, we look forward to learning more. Thank you Kara. And so we've heard from Mitch how we detect PFAS and now we want to talk about how we get rid of them. And when we do that, we basically have to distinguish two fundamentally different approaches: nondestructive technologies and destructive technologies.
So this list of treatment processes that you're seeing here may not be complete but it shows the most applied or most thought of considerate technologies under non-destructive you see familiar processes such as sorption to activated carbon, ion exchange and then also membrane technologies, the advantage of doing non-destructive treatment is that it is much less costly.
So if you have a site where you are basically bound to treat right away, this is typically one of the first choices you would consider. The disadvantage of nondestructive technologies obviously that this very strong carbon-chlorine bond stays intact and that you have a waste stream that needs to be managed. As opposed to that, we have destructive Technologies. And those are much more expensive.
Of course, the big advantages you can sleep easy because your carbon fluorine bond is broken and they are not going to appear anywhere not going to create any liability for you or your institution. And so it's kind of peace of mind. There isn't a long list of technologies. Unfortunately, Mitch had mentioned incineration is currently really the only option you have for large waste streams. There are other technologies in development.
I would say who have made it to the pilot scale. Electrochemical oxidation, sonolysis, plasma. More that will take a look at but you can already see that those are kind of oddball technologies and not that widely applied. They are very efficient for PFAS, but they are also very costly.
So let's look at the non-destructive treatment technologies. First there is of course GAC or granular activated carbon that can be used in filters. And you may be familiar with that from other treatment water treatment technologies or sites. The big advantage this technology is available at the full-scale right away. So you have a problem, you can apply this. It is in terms of PFAS the most studiedeechnology. In most cases
It is also the most economical technology when it simply comes to the task of PFAS removal. There are preferences that have been seen for PFAS, long-chain compounds removed from water much better than short-chain compounds and there is also a preference for PFSAs. And those are the appropriate perforylalkyl
Sulfonate such as PFOS or perforylalkyl carboxylate such as PFOA. Another benefit could be that if you have mixed plumes that co-contaminants can be removed to it can also be a drawback because that may be competition for sorption. So it really depends on the mixtures that you have or on the ground water quality in general because there may be natural organic matter that competes with sorption sides.
It is also important to keep in mind that granular activated carbon products can vary greatly they can come from different sources from coal, from coconut they can be activated in different ways. So that pilot testing is very essential so you can run for instance rapid small-scale column tests such as Chris Polonas at School of Mines did. You can see the pot here on the right hand side to avoid a overshoot of poorly absorbing species. So very important is that these tests are being run. They will cost
You a little bit up front, but they will save you a lot of money later on and save you from a lot of headache and in this on the right hand side, you can see too break through curves of PFCAs at the top and PFSAs at the bottom. So normalize concentration on the left on the y axis what comes out / what goes in then as a function of that volume
You can convert this into time if you want to and if you compare colors for instance green to green those are the six carbon PF H XA at the top and PFHX at the bottom. You can see that the carboxylites breakthrough much faster.
So activated carbon works pretty well. The problem is that at the end you are left with a PFAS Laden product that needs to be managed in some point in some form and this you can either bring it to a landfill but you're really just transferring the problem to different environmental compartment and potentially creating legacy issues in future and you can also thermally regenerate activated carbon, that's widely done.
But at which temperature this is really effective for PFAS that is still a topic that is under consideration people are doing research on that. So we're not quite firm on these temperatures yet. And the final drawback also is that the app in general is less effective for C6 type replacement PFAS. So basically for the short chain compounds they don't absorb as well.
It is quite similar when you consider ion exchange. It's also a non-destructive treatment typically with a smaller footprint than GAC and about similar costs maybe slightly higher but it really depends again on the site and this is something you want to test. Ion exchange is available at the full scale and we generally see a similar preference for PFAS preference over long compounds versus short compounds preference over PFSAs over PFCAs.
Now you can mix cat ion and anion exchange resins to remove anions and cations and squid ions what I'm saying here is however because we're relying on ion exchange any uncharged precursors, telomere alcohols for instance, they don't go through completely. There are some removal because these resins as you can see on the top right in the top right corner of the slide they are organic. So there is some sort of uncharted
species but it's quite possible that they will break through. If you don't want to try them they can transform into PFCAs down the line or PFSAs and create a secondary source. So that's something you want to consider just as with activated carbon there is competition for sorption side sites.
So the water quality at the side really matters, you want to run site specific tests to avoid an overshoot of Corti adsorbing species and again, you can remove PFAS, but you are going to end up with waste stream that means management and that is both spend resin and also the highly saving regenerant solution that you're generating and just as GAC ion exchange doesn't work very well for the short chain compounds such as C6 type replacement compounds. More effective under non-destructive treatment is membrane filtration on the right-hand side you're seeing basically four realms of membrane filtration. There is microfiltration ultrafiltration. Those are not effective for PFAS, but Nano filtration and reverse osmosis are. Those pore sizes are small enough to reject most of the molecules that would otherwise go through.
So in general we see better retention of PFAS compared to GAC or ion exchange, but you're also looking at higher costs because these membranes are quite expensive and you will also spend more energy for pumping.
The treatment is based on size exclusion and electrostatic properties of the membrane. So you need to choose a good membrane. But if you do that, then you can reach about 99% rejection and reverse osmosis, which is used as a lot of a lot of residential applications as this is very effective. You can get to about the same rejection with nanofiltration and you would want to test that and if you can it would be advantageous because you can run this process.
cheaper with higher water recovery and lower pressures. Membrane filtration or these two nanofiltration and reverse osmosis, they're effective for removal of co-contaminants to but this can also lead to membrane fouling if you have a lot of organic matter in your water. So pretreatment may be necessary.
However, if you do it, right you can reach about 75 to 90% pure water recovery and you end up with a concentrated waste stream, but only of 10 to 25% that you would then have to treat. and on the right hand side you see an example from a previous calculation whether PFOS passage here is plotted as a function of time with different membranes. You can see the membranes basically that lie below 1% of PFOS passage. Those would remove 99% operator of this compound.
Among destructive treatment trains as mentioned. There aren't that many choices large scale, large waste streams, really looking at incineration. The good news is it works for all types of media and not just aqueous media.
You can do for cause soil and sediment too and it's also being used for the incineration of AFFF stockpile if there’s anything you want to get rid of it does require incinerators that run at higher temperatures than normally currently, I think a lot of the restoration plans for PFAS are running at about eleven hundred centigrade. There are some species that we know of that would require temperatures of probably up to 1400 centigrade. And again, this is a field that is currently under investigation by a lot of scientists. There are environmental concerns about the generation of incomplete combustion products that may be released through the exhaust gas and pose atmospheric problems.
And depositional problems and then there are other environmental concerns, factors that need to consider and cost in, you may not have an incinerator nearby so you can at nlongdistance trucking. If you are in the western states of this country then water recovery is a big issue every drop is important and you have very low to no water recovery when you're incinerating water, and of course you're looking at very high energy cost.
As I mentioned there are other destructive technologies some of these we are working on and a lot of our colleagues are working on just to mention them briefly sonolysis is treatment by ultrasound.
This is technology that may also become very useful for residential destructive treatment because it's quite easy and reliable to run there is electrochemical oxidation hydrothermal plasma Advanced photocatalysis with special catalysts just to name them. So again the you may not be very familiar with them. If you are in the field of remediation, you may have heard of activated persulfate and I put that here under development. There are certainly remediation of assistant organics done with activated persulfate already, but it really only tackles PFCAs, unfortunately. So the and that only under certain pH values, it doesn't really get at PFSAs. So let's consider that too.
However, no matter what kind of treatment you're looking at. There will be significant costs associated with PFAS. And of course then the big question becomes how can we lower the cost of PFAS treatment? And there is really one answer. Well, there are two and we'll get to the second. But the first one in terms of active treatment is treatment trains.
There are a lot of approaches that either remove or degrade PFAS and really the key to this is to harness the synergies that rise from combining these treatment technologies. So you see this sketch on the right hand side from a recent review paper, and in blue, you see several removal methods and green on the right top side you have deprivation methods. I would dispute the zero valent iron that should go on the removal methods and we've actually published on y0 valent iron. Unfortunately, it does not work for perfluorinated compounds, but the idea here is basically that you are generating either attend and treatment train.
Where you typically do a removal technology first generate a concentrated waste stream that you then treat destructively or you can create a parallel treatment training where you combine destructive Technologies to make the overall process more efficient.
One example, I wanted to give here that comes out of our research group. We have published on this and believe that this is a very good approach is the combination of Nano filtration with electrochemical oxidation. You can see a molecule here, this molecule. You probably know under the name Gen X and we don't like Gen X as scientists. It's a trade name. It's not very accurate. Plus I myself I am Gen X.
Generation X, so when people talk about Gen-X removal or treatment, I always feel a little bad about it. We prefer the name hexafluropropylee oxide dimer acid or HFPO-DA and the idea here is that typically you are treating very dilute solutions at the PPT level. So let's treat this first with removal for instance. Now filtration has been shown to be very effective, even for the small chain compounds and then you treat a much smaller waste stream destructively.
And discharge that, for instance to wastewater treatment.
We tried this with commercially available material so we can scale up this technology on a nano filtration site. We used a film tech and f90 membrane that doesn't need much power of pumping pressure and we achieved 80% water recovery and an infant concentration of a thousand micrograms per liter of Gen X with 99.5% HFPO-DA rejection.
So over two orders of magnitude and most of that mass was then captured in the rejectate, That's the concentrated waste stream. And then we had five micrograms per liter only in the permeate. So a factor of 200 lower, and this concentrated waste stream, then we treat it electrochemically again, I want to point out Nano filtration is likely effective for PFAS of all sizes in charges.
And what you see on the right hand side here is our electro chemical treatment with a normalized concentration on the y axis as a function of time on the x-axis and you can see that the concentrations go down over time through fluoride analysis. We proved that the carbon-chlorine bond was broken and the other effect that you see here too is actually that this concentrated waste stream, the Nano filtration rejectate, was faster to be treated than the raw water.
So there were synergies that could be harvested and we saw that when we consider operational costs and capital cost.
So in this graph you see on the left hand side the electric energy per order of Gen X removed if we had treated the raw water directly in red we had spent a lot of energy, but since we only treat it a Nano filtration rejectate, we were able to lower the operational costs by over an order of magnitude and same for the anode surface area per order of Gen X removed, we lowered the capital cost basically by over an order of magnitude through combining these two technologies. Now, if you don't intend to do Electro chemical treatment, Nano filtration could be a very good pretreatment or other destructive approaches too but really the bottom line here is that treatment processes can be combined in various ways to achieve site-specific goals and lower the cost of PFAS treatment.
So the other truth is, and here's the second solution to destructive treatment, the potential second solution. Is that over the 40 years that we have done active remediation, microorganisms have really outcompeted us in most ways and never get quite yet to the efficiencies and especially the cost efficiency of having microorganisms take care of the destruction of aqueous contaminants.
So let's think about this for a second here, our current understanding of microbial degradation on the left hand side here is that there are bacteria ubiquitous in the environment who can oxidize the non-chlorinated tail of polyfluorinated compounds, but they generate perfluorinated compounds which then become resistant to further degradation and would basically generating dead end products.
This may look a little different on the fungi side, I’m mentioning fungi here here because fungi here because fungi are typically found in the top layers of the soil. And that's exactly where PFAS are found too if they stem from atmospheric deposition. If they stem from firefighting training for instance, most of these source areas and disperse atmospheric deposition areas they have most of the mass in the top two or three feet.
Where fungi are, at least researchers have found that polychlorinated compounds can take a different route away from these performing at a dead end products whether it exactly needs to is still under investigation, but that may be a promising area to look into further.
Because there is evolving evidence that there are enzymes that fungi and other organisms process that can actually break the carbon-chlorine bond. So here is a study by Jack Wong at the University of Georgia who showed PFAS and controller degradation by laccase. You can see on the right-hand plot here. These are the normalized luring concentrations as function of time in this blue line here, that is fluoride release. That is a very strong line of evidence that the carbon
fluoride bond was broken. And so this was first line of evidence that perfluorinated compounds may actually be prone to biodegradation processes. Then last year, there was a publication by Peter Jaffe from Princeton. They showed the first microbial transformation of perfluorinated compounds. Now, this is a highly debated study.
There is very strong evidence for this process because on the top right you can see fluoride release by this microorganism. And again, this is always a very strong line of evidence that the carbon fluorine bond was broken. There are some mechanistic aspects that remain on the bottom right
You see that the researchers reported PFAS as a major intermediate of PFOS and mechanistically that's very difficult step to make so again this requires further consideration, but there are good lines of evidence. So to basically come to conclusions on the treatment side. What can you take home? First of all, if you are hard pressed to remove PFAS from contaminated water, there are non-destructive removal technologies you can apply right away. They're available and large-scale field scale, but you will generate a waste stream that needs to be managed. Among destructive technologies, there's really not much else other than incineration and all the other technologies that I showed that probably two to three years out
So you’ve got to be a little more patient, but the key really to keeping the cost somewhat reasonable will be to combine technology into treatment trains and harness the synergies that arise through this combination. And then finally, I did want to end on a positive note here. I do believe there is hope and there are certainly evolving evidence that there maybe biological processes that lead to destruction of PFAS. Keep in mind. First of all microbial evolution is much faster than human.
Evolution so all the anthropogenic contaminants that we've thrown at bacteria so far they've been able to degrade it and it maybe a matter of time. The time scales may not be very promising. We'll see what we get. But there's always a last resort we can possibly do bioengineering genetic engineering to help with the process. And so with that I wanted to thank those who sponsor the nano filtration electrochemical oxidation study. I wanted to thank SERDP for my grant 2718.
In which we are exploring destructive treatment trains and frankly a lot of the studies that I showed here. They were sponsored by SERDP too, and with that I would pass it back to Kara.
Excellent. Thank you. Thank you. Jens. We probably have time for one or two questions. Before we get started with Q&A, I just wanted to mention that the final installation of Trihydro’s PFAS webinar series is coming up next month. We're going to be discussing data analysis interpretation and risk assessment and registration is open and we'll be sure to send you a registration reminder. So as I mentioned time for one or two questions Mitch, I believe this question
is for you. Someone asks in the top assay method for estimating total PFA., what do we use for oxidizing what exactly is this test procedure. The specific details? I would have to look into a little bit more. I believe it's based on heated persulfate. It's a very aggressive oxidant. I do know that that is an intended and Jens you know more about that, you've been working on that in your laboratory, right?
Yes, so you're right. It is persulfate and the persulfate gets heat activated at 85 Centigrade. The important thing is that it gets heat activated at high pH because at low pH it generates sulfate radicals and they can actually degrade some of the PFCAs we want to quantify and high pH the sulfate radicals get scavenged by water.
They generate OH radicals and they only transform the precursors to perfluorinated compounds and that's what we quantify. I'm fine. Thank you. I'm going to squeeze one more question in here. Jens. I think this is for you. It is do bacteria attack the head or tail of the PFAS?
That's a good question. So I'm not sure, I don't believe that there has been any light shed on where exactly the bacteria attack or the enzymes attack. What a radical species. So I'll try to make this brief. They will basically attack the carbon that is sterically most accessible wherever that happens and that doesn't just depend on the electronic structure. It will depend on steric considerations, too.
So my guess would be somewhere the alpha or the beta carbon somewhere close to the functional group, but depending on the sterics that happened during certain processes. It's not impossible that it happens in other parts of the molecules as well. Thank you for that. I need more data. We do need more data. Thank you. We're reaching the end of our time. We want to thank you so much for joining.