Webinar date: February 13, 2020
Watch the webinar recording below for an in-depth look at advanced PFAS concepts and key considerations for PFAS-free firefighting foams. This is Part 1 in Trihydro's 3-part PFAS webinar series.
For more information, contact:
Mitch Olson, PE, PhD
Hello, my name is Kara and I would like to welcome you to part 1 of Trihydro’s three-part PFAS webinar series. Today's session is titled “A Deeper Dive into the PFAS Problem” and we're excited you could join us. It's my pleasure to introduce Mitch Olson. Mitch is an environmental engineer and emerging contaminants subject matter expert at Trihydro. He's 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. Mitch with that. I will turn the presentation over to you.
Thank you for the introduction. In many ways, the unique chemistry of PFAS, their environmental persistence coupled with their ubiquitous use in industry and consumer products has placed us in uncharted territory. The PFAS problem refers to the emerging challenges that are facing us as environmental professionals.
But also as a society as we come to grips with PFAS in the environment. The objective of this webinar series is, as the name implies, to move beyond an introductory level regarding the challenge of the PFAS. There are so many PFAS-related topics of interest that one hour cannot do much more than skate across the surface of the many topics. This kickoff webinar covers conceptual-level PFAS topics including PFAS sources and how their chemistry affects what happens after release. The next two webinars will provide information on the response (site characterization, remediation) and toxicology. Many of the properties that make PFAS interesting are closely related to their chemistry. While we will avoid talking about PFAS chemistry for its own sake during this presentation.
While covering some of these concepts we will provide some chemical background. The PFAS information sheet or the handouts that Kara alluded to may be a useful resource as we go through this webinar and down the road after the webinar is complete and will refer to this a few times through this presentation. The location of the handout is shown on the screen.
And as noted a few comments about the information on this handout, this shows a subset of about 40 or so of the thousands of compounds that comprise PFAS. Some of the information that's included on this sheet includes PFAS naming and classifications, which we’ll allude to little bit more later in this webinar. These are based on ITRC and EPA documents.
The naming conventions aren't completely standardized at this point. PFAS compound names and related acronyms are shown. Chemical abstracts service numbers which are useful to look up more information about these chemicals’ molecular weights are shown and the chemical formulas are also added to aid in understanding the similarities and differences between the different families, classes, and groups of PFAS compounds. As you may know if you have the handout in front of you, the chemical formula is color-coded a common feature between the PFAS compounds is that I'll have a fluorinated tail and non-fluorinated head. These two portions are color-coded red and blue.
Also shown here are analytical method information, which we won't refer to much in this webinar, but we'll talk about in more detail in the second webinar.
PFAS is an acronym for the admittedly strange term (per…) used to describe this classification of chemical
PFAS are an emerging contaminant defined as something not completely understood but it's widespread enough in the environment to matter, which very well encompasses the PFAS problem. The classification of PFAS may include 3,000 up to 10,000 individual compounds that are part of this complete class known as PFAS. PFAS compounds are very widely used by industry and consumers. We’ll talk about a few of these uses and how they lead to environmental release.
PFAS are also very stable to an unusual extent compared to most of the other environmental contaminants that we’re used to working with. The problem with the stability is that it makes them useful for a lot of ways, but it means that they may remain in the environment long after their intended use is complete.
As the kickoff of the three-part PFAS webinar series, this webinar attempts to address these questions: why do PFAS matter, from both the scientific and a public perspective? Where do PFAS come from both in terms of production and how that leads to the release into the environment? What happens when released? We’ll look at this in terms of fate and transport then also different types of sites and how that may affect how PFAS are distributed in the environment. How PFAS are managed once they're identified
In soils or groundwater or another environmental media? And then finally, I guess the wrap-up question: how can future releases be controlled or prevented? So starting off with the question of why do PFAS matter again? There are two sides to this coin in their science and the public perspective. The science PFAS presents many unique challenges and is evolving quickly in the number of publications. It's difficult
To keep up with. There's a lot of new information coming out in terms of how they behave in the environment, analytical techniques, remediation approaches are really across the board. And something that seems, at least from my perspective, unusual about PFAS is how quickly some of these peer review publications get picked up and become headlines in the newspaper. An example shown here about a paper publishing a new analytical method that was effective in evaluating PFAS present
For materials such as food packaging was published and then shows up in a paper here. This catches a lot of public interest when PFAS shows up in new areas.
A similar example shown here. Where PFAS were identified in drinking water sources based on EPA water treatment system type of data.
This one really triggered an avalanche of headlines. One shown here from The Denver Post regarding drinking water and some Colorado area drinking water wells. To try to put the science and public perspective in a visual format, this image attempts to capture all the various aspects of PFAS that are unique and they may keep the scientist up at night. Several different factors here in this hexagon diagram when we try to look at how this appears from a public perspective. This is the image we came up with. It seems to fit best. There's a Roman battle formation known as the test.
They're tested over turtle formation. But the idea of these tightly packed shields that are impenetrable that nothing can get through and I think this captures the public image of PFAS at this stage and I think this image isn't entirely unwarranted considering the challenges.
Another reason that PFAS matter is how widely used they are. Several of the uses are shown here. One of the work common uses that has led to widespread use and distribution of PFAS in the environment is firefighting foam. They're used in Class B flammable liquid type fires such as petroleum hydrocarbon type fires. A lot of different consumer products also use PFAS, this includes leather treatment.
Consumer products including dental floss, nonstick cookware, which uses PFAS in the polymerized form, but that can be manufactured from PFAS stain-resistant fabric. So I think many people with kids can appreciate this picture. We've probably had an easier time over the years cleaning up our carpet after things like this thanks to the PFAS that's used to add the stain resistant coating to the carpet.
Non-stick food packaging – popcorns, one of the well-documented types of food packaging that's known to contain PFAS for me personally was kind of an “aha moment” about the effect of PFAS food wrappers occurred after ordering a sandwich in an airport, I sat down in one of the airport chairs and ate the sandwich. It was quite greasy; I look down and have this piece of paper in front of me after it's done and it's got a puddle of grease in the sandwich on it.
But under the paper, there's nothing soaking through getting onto my jeans. That's the effect of PFAS keeping the oil from soaking through these types of food packaging. And also water resistant fabrics are another widespread use. This really focuses on the consumer using PFAS. There's also very widespread industrial uses. We'll talk a little bit more about these in upcoming slides as well.
PFAS have been commercially produced going back to the 1940s in the early production was primarily focused on nonstick types of coatings. In the 1960s began to be produced for the purpose of these firefighting foams. In late 1960s, US military specified that the compounds must be used in their firefighting foams. In the early 2000s
We began phasing out PFAS. PFOS, one compound out of that the PFAS mixture, and related chemicals. Between 2006 and 2015, EPA implemented its stewardship program which phased out production of another one of the individual PFAS compounds, PFOA. In 2012, EPA implemented a monitoring program evaluating for a short list of PFAS compounds and drinking.
Water treatment systems. One of the key dates here. 2016 is the day that EPA issued Health Advisory Levels for PFOS/PFOA. This is again, just two of these broad class of chemicals. The health advisory levels were issued for at 70 parts per trillion, which is lower than almost all of the conventional organic contaminants that we’re used to seeing in drinking water. In 2019, EPA also began implementation of a the PFAS action plan, which included a list of items
that they were looking into making progress to control PFAS through commerce and ultimate use. Perhaps most importantly when addressing this question of why PFS matter is their health effects. This brief summary slide here focuses on the description through ATSDR, the agency for toxic substances and disease registry, which provides a good and probably on both the most thorough evaluation of these compounds. Again, it's limited to a relatively short list of the PFAS compounds that for which a substantial amount of data exists for documented human health effects. According to ATSDR, shown here in this list: hormone interference, increased cholesterol, immune system affects, increased risk of some cancers. There's a few notes regarding the cancer designation to PFAS here on the right-hand side. They've been designated as possibly carcinogenic to humans. EPA’s Health advisory documents also provided some evaluation on the carcinogenic potential.
There's a notable difference between PFOA and PFOS for the EPA document stated that epidemiology studies demonstrate an association of serum PFOA with testicular tumors among highly exposed members of the general population, whereas PFOS epidemiology studies did not find a direct correlation between PFOS exposure and the incidence of carcinogenicity.
There’s uncertainty in the future and this is again just two out of the many thousands of compounds. So a lot of uncertainty remains here and work remains to be done. I know here in the bottom left here about PFOA/PFOS vs. other PFAS these two compounds have really been the focus of much of the work that's been done to date and a lot of uncertainty remains regarding other PFAS compounds and also combined effects due to PFAS mixtures. There's also a note on the lower right regarding
Animal testing data and human health effects. A lot of the data for the basis for these health regulations is animal testing data, which involves higher doses than are often going to be the case for human exposures. These may not directly translate and more data are needed at environment friendly and environmentally relevant exposures.
The next question we'll address is what happens to PFAS upon release. We’ll address this question from two perspectives: that of PFAS chemistry and then PFAS site types. For the PFAS chemistry discussion, we’ll focus on PFAS. They are similar to but different from some of the more conventional environmental contaminants such as PCBs, hydrocarbons, chlorinated solvents.
As indicated here in this Venn diagram, they kind of occupy this lone spot in the middle where they are a unique combination of having this complex mixture, a stable molecule, and being mobile in groundwater. There really could be another dimension added to this Venn diagram – just in the widespread distribution. The fact it’s used in such a wide variety of products, industrial, and consumer goods. And then we'll talk about PFAS release sites types because there's such a useful chemical all different types of sites,
Which they may be released.
As we begin to discuss the behavior of PFAS in the environment, a little background of the chemistry is warranted. Chemistry can get very complex and I hope, to that end, that the handout may be a useful resource to help understand and sort through some of the PFAS chemistry. The PFAS family tree is shown here. This illustrates how if you look on the left-hand column of the handout, classification, family, class, and group has shown in the family tree are divided.
And so hopefully between the handout and this helps to clarify the distribution of some of these types of PFAS. The key items to note from this PFAS tree is PFAS can consist of either non polymer or polymer goods. The polymer type PFAS, that's what you might find in your nonstick cookware. Polymer PFAS are typically constructed from the non-polymer type.
But ultimately it's the non-polymer types of PFAS that were most concerned about in terms of environmental fate and transport and we'll focus mostly on the non-polymer types, which is the individual compounds not combined into polymers. The non-polymer PFAS, as indicated by the name per- and poly fluoroalkyl substances, they can be divided. A group indicates saturation, that all carbon is being bonded to fluorine or final functional group.
Poly fluorinated is only partially fluorinated. Another key concept we want to mention here is that of alkyl acids or PFAS perfluoroalkyl acids are the end products of degradation. These are the class to which the compounds such as PFOA and PFOS belong to. They’re the top couple of groups shown on the handout. If you're looking at that handout and have that now the profile classes are at the top other groups here.
We see this, the triple dot, the ellipsis, that just indicates that there's too many compounds to name. This is where there's thousands of compounds and some of these other potential categories. So again / for a local acids is a concept we’ll refer to…these are the end products of degradation. These are products that don't break down further. These can be subdivided into the peripheral carboxylic acids per flow sulphonic acid.
So we don't need to get into detail for our purposes today, but these other groups to which PFOA and PFOS, two of the most well studied and regulated compounds belong. Chemical structure of PS1 particular compound PFOA is shown here. Again, this is one of thousands of pieces compounds, but we'll talk a little bit about what this basic structure of PFOA and features of the PFAS compounds. They all have this fluorinated tail and a non-fluorinated head.
And again, these are color-coded on the handout. The fluorinated part of a compound the tail is red. The non-fluorinated head is blue. It's the combination that gives PFAS much of their unique properties and determines how they behave in the environment and we'll talk a little bit more of that in the upcoming slides.
Following this discussion of the molecular structure. What are the key ideas in PFAS chemistry? Is that a biotransformation some PFAS may biotransform but PFAS as a whole will not biodegrade and we'll explain what that means. Biotransformation describes the process through which precursors are transformed into end product (PFAAs), which are the peripheral classes. The PFAAs is a definition shown here for precursor, which is a polyfluorinated
Compound. Polychlorinated means it's not completely fluorinated. There are carbon hydrogen bonds that can be partially degraded into a perfluorinated compounds.
It has only carbon-fluorine bonds plus a functional group which cannot further degrade but we see an example here showing for precursor and an end product a precursor shown here is 8:2-FTOH, which is biotransformable again. What that means is it's probably fluorinated polyphony meaning there's carbons that are not fluorinated. These may be partially degradable. The transformable carbons are indicated here or these may be broken down to form something like PFOA as an end product, which just has this functional group just stable carbon at the end of the molecule biotransformation process.
The tail of the compound, this carbon, this fluorinated carbon tail is not touched except for under some fairly extreme circumstances. The carbon-fluorine bond is the strongest organic bond. One of the strongest bonds nature remains unbroken and that's why PFAS cannot be biodegraded. Again a precursor, may be biotransformed into perfluorooctanoic acid or an end product.
But ultimately a PFAS will remain a PFAS, it's the carbon-fluorine part of the molecule that gives them their stability. There's a few additional comments worth emphasizing regarding the biotransformation concepts related to PFAS, biotransformation can occur in several different media types. It can occur in the environment after PFAS precursors are released in the subsurface. They may be transformed into the end products within the environment if remediation is applied to a site that may help to accelerate the transformation of precursors into real class
End products. This transformation can also occur in the wastewater treatment process.
Yes, and also within biota if precursors are consumed, they may be processed within living creatures and transformed into perfluoroalkyl acids.
Biotransformation increases the relative concentration to perfluoroalkyl acids or end products in terms of environmental releases. This may increase with time after PFAS have been released with distance from the Source, the relative amount of peripheral classes relative to precursors may increase as biotransformation occurs because it is a one-way street. It's one-way reaction. Also finally worth noting some
PFAS could be transformed but none can ultimately be biodegraded.
Another key factor contributing to the complex chemistry for PFAS is chain length. A definition is shown here for long and versus short chain perfluoroalkyl acids. As with all things PFAS, this can't be extremely simple. This is a based on the ITRC document and according to the documents for our carboxylic acids
This is the group which PFOA belongs. Seven or more fluorinated carbons would be defined as Chain 4 / Flair for phonic acid. This is the group that PFOS belongs to. Five or more fluorinated carbons the chain links. You may hear reference to the challenge in terms of how it affects PFAS transport in the environment. Several of the different properties, including the firefighting foams (new versus old foams) may be produced differently and we'll talk about that here in upcoming slides.
To summarize the differences between PFAS compounds. PFAS has a large number of individual compounds. Estimates range from 3,000 up to perhaps 10,000 individual compounds. The reason that there are so many compounds within this mixture. They have some common properties but variability includes the chain length of the chain language refers to the flowing of the carbon portion of the molecule precursors, which refers to variability in the non-fluorinated
Head of the molecule and there's also other variables such as branched versus linear isomers that can add to the number of individual compounds in the mix, which can complicate management and potentially ultimately remediation in the environment. The take-home point out here is that all PFAS have some common traits, but the properties may vary significantly between PFAS families.
Another piece of property that affects behavior in the environment is that it is a surfactant. This is the combination of having this fluorinated tail and non-fluorinated head. The head of the molecule tends to be polarized, which is a way of saying that is hydrophilic. It's why it's water-loving. It's attracted to water. After releasing the environment, the tail on the other hand is both hydrophobic and oleophobic, which means it repels water and repels oil.
Basically is it's the grumpy old molecule that just repels everything.
Composition of head can vary substantially. Again precursors that can take many different sizes and shapes even ionic charge can vary the head of PFAS compound can be anionic, cationic, or zwitterionic. Zwitterionic being a combined positive and negative charge and all of which can affect how PFAS may ultimately behave upon release into the environment. Variability in the tail of the molecule as well may include the chain length. How long the fluorinated carbon portion of the chain is?
An additional variable in the tail some more recently produced PFAS compound these so-called replacement compounds, which are indicated in the in the handout, may be modified with an ether or an oxygen inserted into the chain. Even with this modification the tails are still extremely stable. A couple of cartoons
on the right show how these properties affect how they're useful for many of the different product or uses where also used for repelling water or oil in there.
They’re used in carpet, clothing, food packaging. It's the repellent tail, the water and oil repellent tail that creates this coating that everything basically runs away from and it's very effective at this use but again, very stable and then in terms of firefighting foam PFAS, the molecules align themselves, they create this barrier between the flammable oil and the air where combustion would ultimately take place.
So this raises the question then: how do these properties affect PFAS mobility in the environment?
There are two key concepts regarding PFAS attenuation processes in the environment. These include option and interface partitioning, both of which have very unique aspects as compared to some of the more conventional contaminants organic contaminants that are used to working with. The idea of organic carbon partitioning as we applied for fate and transport modeling for organic contaminants this applies to PFAS, but not very well and variably between the different compounds depending on the different structures that different head and tail structures of different molecules.
So it's a really imperfect parameter if being used alone to describe how PFAS are partitioning into organic matter and soils because of this polar head electrostatic attraction is another factor to absorption of PFAS, which adds another level of interesting complexity in terms of distribution. Because of their surfactant behavior, interface partitioning is also a very important factor for PFAS which sets them apart from hydrocarbons in chlorinated solvents. PFAS like to accumulate at these interfaces in the subsurface. Many different types of interfaces may occur. This may occur where water and air come together. If there's a non-aqueous phase liquid, different interfaces may form in these zones.
With those processes in mind as we revisit the question that what happens when PFAS are released, using this conceptual illustration as a backdrop. PFAS transport and attenuation processes that govern distribution in the environment.
All of the processes shown here may not necessarily be applicable to all the different PFAS type sites. This is probably most applicable to a firefighting foam or an AFFF type site release, but we will circle back to other site types. Primary transport processes as shown here in approximate chronological order may include surface spreading where if PFAS is released in a relatively small area or just natural spreading of foam.
Increase the footprint volatilization and atmospheric transport is another important process. This is somewhat counterintuitive in a sense that PFAS are not thought of as being volatile and they aren't in the sense that air stripping is not an effective remediation strategy, but some portion, because of the complex mixture of molecules, some portion of them are semi-volatile and they evaporate into the air they may also be released in the atmosphere as an aerosol
Or even clinging to dust particles that contribute to spreading. This can lead to measurable background concentrations on a local scale. But this also leads the global scale transport ultimately being a factor toward PFAS being detected in the blood of polar bears. So now back to our conceptual site, other factors that may be mechanisms that may lead to PFAS transport
Include surface runoff or drainage, which may lead to PFAS discharge through stormwater systems or may otherwise spread the footprint of PFAS.
Infiltration is another mechanism.
This can affect both shallow soils and the footprint of where PFAS was released if they do keep on moving down through groundwater PFAS, can then ultimately affect groundwater where some fraction potentially very significant fraction can be highly mobile and groundwater and because the combination of mobility and how stable molecules are these plumes can move groundwater plumes can extend for great distances from where they occurred. They may occur from hundreds of feet to miles. They really may continue until ultimately some discharges to surface water is encountered or some barrier to groundwater flow.
So ultimately discharged the surface water and surface water than equally equilibrium with sediments may occur.
There's several different transformation and attenuation processes that may be occurring to atmospheric transport the volatile portion of PFAS that may be susceptible to atmospheric transport can also then be precursors that may ultimately degrade to those perfluoroalkyl acids and then be deposited either on a local or regional or global scale.
The next three processes, absorption, interface partitioning, biotransformation, really would tend to occur simultaneously throughout all of the media that PFAS may be present in in the environment as we as we've noted the sorption interface partitioning.
Both of these processes will somewhat be occurring simultaneously, complicating our understanding of just how PFAS may be distributed as they move through the environment and then the biotransformation can be significant as well a lot of cursor is maybe more likely to stick in soils or solids, but then may transform into more mobile perfluoroalkyl acid products.
To illustrate how the PFAS distribution can vary. This image shows how PFAS distribution may need to be accounted for to have a really thorough understanding when conducting fate and transport modeling for PFAS.
This shows how the PFAS distribution may be affected moving from shallow surface soils directly beneath the source area through this transition into the saturated zone in this case. Where number two is shown here where some NAPL may be present within a source area, which may be the case particularly at firefighting foam training type sites were hydrocarbons may be used and then used for training purposes for firefighting.
And then three down into the saturated zone where from where a plume. And then 4 and 5 would then indicate potential PFAS distribution further down gradient and key points from these images are first that help PFAS would like to accumulate at interfaces as well as absorbing onto two solids a significant fraction of the PFAS mass may be found in desorbed and in air interface.
It's the interface accumulation that tends to be the key process in terms of potential attenuation, but accumulation and then moving down into the saturated zone where more greater fraction of PFAS may be present in the water phase moving down gradient into the plume the relative distribution between soil and water phase it may change with distance due to impart filtering out of the fraction that you have compounds that are more likely to absorb onto solid materials, these being the long-chain compounds some precursors that have an affinity to be absorbed soil materials and so forth.
Fourth and all these dots are shown to illustrate how the PFAS distribution may look at a typical site. These are mostly based on intuition and it's worth noting at this point that the degree of data collection required to really understand the PFAS distribution at this level has been done at very few sites for PFAS as composed as compared to chlorinated solvents.
Where so much higher resolution data has been collected a lot of sites every site is unique, but a person can have a fairly good perspective of what the distribution of solvents may be just based on some knowledge of site geology depth to groundwater and a few basic factors of the sort. PFAS is in a very different state of development compared to those types of sites.
It's now following that general discussion on the PFAS distribution we’ll look at which sources tend to lead to PFAS in the environment and how these sources affect PFAS distribution. Many of the most studied PFAS sites are associated with a AFFF for the firefighting foam. This is to a large extent because of the Department of Defense and Air Force response to PFAS challenge.
A large number of sites, some of the other types of sites are more in their early stages of a getting a broad understanding of the impacts of these types of sites and also worth noting AFFF was the site type the model for the fate and transport that we had just discussed previously. The primary release pathways this may be associated with AFFF type sites are first surface spreading as full moon spreads after incident response or training areas volatilization is another potential pathway. And again, it might be a relatively small fraction of the PFAS that are actually susceptible to follow association, but particularly in areas where there's repeat applications of the accumulation of PFAS can be very significant surface runoff through stormwater or direct discharge and then soil impacts and infiltration are all relevant processes shown.
AFFF type sites, they may be associated with military sites or airports, worth noting that both the Federal Aviation Administration and the Department of Defense have required use of fluorinated foams for firefighting and this has been the case for at least a few years to several decades now, so historical use of PFAS at these types of sites is expected to be widespread. In fact, it's been somewhat mandatory and the potential use of AFFF at these sites may include incident response, but there's also training areas that the training areas are the types of locations where AFFF may be applied repeatedly over several years. In addition to military and local airports, local fire departments, hydrocarbon handling facilities, several other types of sites that either would respond to our environment
business of handling or processing large quantities of flammable liquids may be susceptible to having used AFFF. For industrial sources, these can be the types of sites where PFAS was directly produced but PFAS are also used in a wide variety of tasks, maybe including a metal plating textile production or paper production. They're also used in the electronics industries, aerospace.
There's really wide use of industries where PFAS are associated. Highest concentrations may be associated with direct production types of facilities, but this may not necessarily always be the case. The types of PFAS emissions from these types of sites somewhat similar to the AFFF type sites. Although the mechanisms that formed the release may differ substantially, of course, the atmospheric discharge on both the local regional and a global scale can be associated.
With these types of sites, water discharge can take several different forms. This may include surface or storm water discharge, which may ultimately lead to water being discharged, picked up, and treated. Wastewater treatment plant may just lead to a larger footprint of AFFF that ultimately infiltrates into the ground. This could also lead to discharge the surface water industrial sources uses a PFAS may also directly.
Sometimes water may be pretreated for PFAS before discharge to a wastewater treatment plant. Unless water is being specifically treated for PFAS, treatment processes are not likely to affect PFAS concentrations. Water may also infiltrate into the ground affecting shallow soils or groundwater at these types of facilities.
PFAS may affect solid wastes in terms of direct discharge through water or footprint affecting shallow soils or solid waste materials could be discharged at landfills as an indirect source from industrial sources of PFAS.
And speaking of landfills. I know regarding landfills and wastewater treatment plants as potential environmental sources, these are different from AFFF and industrial use type sites, which may directly use PFAS as part of a process.
By comparison landfills, wastewater treatment plants typically wouldn't use PFAS as part of a process, but they’re secondary sources to the environment, but because they can be potential sources to the environment, we'll talk about pathways from these types of facilities. Potential PFAS sources to landfills are very widespread, of course landfills are really heterogeneous in terms of types of waste they accept, how they're stored, and even in climate.
Different types of sources of PFAS landfills may include PFAS production waste, carpet, and clothing and consumer goods. It's worth noting here PFAS containing material disposal in landfills is unregulated.
Even in AFFF that contains PFAS may be disposed of at a landfill. One of the primary potential sources of PFAS in landfills is carpet. It has been noted that nearly all residential nylon carpet that's been produced this century have PFAS added for stain resistance. Carpet is a very significant contribution to waste. An estimate was 2% of municipal waste being carpet to landfills.
The form of PFAS in carpet is largely unknown at this stage. It may be some combination of both the polymerize type PFAS that are relatively less mobile but could potentially break down over extended time periods. And then the non-polymer type PFAS. Let me break down more that may be more directly mobile into landfill leachate potential emission sources for PFAS.
This may include the more volatile fraction of landfill but these have been detected in landfill gas emissions leachate from landfills where leachates being collected and perhaps pretreated. Probably likely ultimately disposed of at a wastewater treatment plant.
Typically treatment technologies are not effective removal of PFAS unless they're specifically designed for removal of PFAS. For older unlined landfills, the potential for discharged plant to groundwater should also be considered.
Wastewater treatment plants may also potentially receive and transmit significant amounts of PFAS. Wastewater treatment plant processes are designed to remove pathogens and some chemicals. But unless it's been something specifically added to treat PFAS, typically not likely to treat PFAS. Potential PFAS sources into wastewater treatment plants several different types of sources because PFAS are present in so many different types of consumer products.
Industrial Waste can also be a significant contributor as well as extracted groundwater landfill leachate. Other processes where water is produced and discharged through the wastewater treatment process itself.
The short story is that PFAS are not treated through these processes that treat these other components of wastewater are not affected or are not effective for ultimately degrading PFAS.
There's a few complicating factors here, particularly the fact that it's been noted wastewater treatment plant effluent concentrations for peripheral classes may be higher than in the influent and that would be due to transformation of precursors that maybe initially present in the wastewater influence stream. According to studies, perfluoroalkyl acid concentrations increases through some steps to process potentially through activated sludge or other biologically active steps in the process are precursors may be transformed. Some steps of the process may decrease concentrations of a PFAS measured in the flow through water stream particularly are dissolved air flotation where PFAS may accumulate in in the flotation and in the flotation sludge or through air
Bubbles moving through the water. PFAS may also accumulate in the solid sledge produced through the wastewater treatment process. The key facet in the sludge would tend to lean toward the long-chain compounds or some precursors that are more likely to absorb, but the key take home message for wastewater treatment is that a PFAS in is a PFAS out.
The secondary discharge pathway from wastewater treatment plant is biosolids. They're treated through EPA-approved guidelines to meet requirements for pollutant pathogen levels, but the treatments are not designed to remove PFAS and ultimately a very unlikely to some of the treatment processes typically used are anaerobic digestion.
Things are more hydrolysis. There's a note from a study here at the bottom on 2019 about a study evaluating PFAS in in commercially available biosolid-based products that were treated and they found that the different treatment processes had either no effect or increased perfluoroalkyl acids in the finished biosolids. That increase would be then due to the potential for transformation of precursors.
So once again PFAS in equals PFAS out. Then treatment processes will be more important to remove PFAS from an influent stream from which biosolids are created then to ultimately have to treat for it at the end. Biosolids are used for several applications, including a land cover, fertilizer for crops, mine reclamation. All these different uses. There's a potential that these can lead to PFAS implications.
Another item worth noting related to wastewater treatment doesn't boil water separator and without going to into this process in process in any great detail. There can be there's a lot of uncertainty and healthy fats will be distributed through this process, but it's likely considering a lot of sites that handle hydrocarbons may have involved firefighting training or incident response that PFAS may be present and where oil going through an oil-water separator. The interface accumulation is going to be a key
Affecting how they may be distributed.
There's not a lot of information collected to date, at least to my knowledge, on how PFAS would behave to the oil water separation process, but an illustration shown here on how PFAS may accumulated interfaces and then ultimately may be affected by the effluent streams and effluent from wastewater treatment plant from an oil-water separator, which includes, of course the treated water the oil that's removed and then some solid sludge that may accumulate different types of PFAS. This question was asked and wanted to summarize some key points here overall. PFAS are persistent mobile bioaccumulative in terms of the persistency bio idea the difference between biotransformation biodegradation.
The fact that some are partially transformable and PFAS as a whole are not degradable is a key part of this persistent question. The fact that they're present in the complex mixture just leads to the need to consider a lot of different factors. A lot of different potential molecules and how they're going to behave moving through the environment. An under looked aspect of PFAS mobility is atmospheric transport. The fact that they can be present in locations that are potentially hydraulically up gradient from a release source or even very large distances from any release sites. And also the idea of accumulation interfaces implications of this are everywhere as we've noted.
After the discussion of PFAS releases, the next logical question is how to respond to PFAS in the environment. This question could be the subject of multiple hour-long presentations. In fact, the final two webinars in this series are designed around addressing this question.
For now, we'll cover this this concept briefly with more details to be provided in the subsequent webinars. What releases occur the next steps include potentially site assessment characterization and if necessary potentially remediation and risk management. As with all things PFAS, site management has its unique challenges regarding site assessment and characterization. Of a key point here is that very few
Lights have gone to a characterization stage at the side at this point in time. There's a lot of waiting and seeing where regulations are going to go. What factors are going to ultimately guide and also development of analytical methods which are still work-in-progress. The regulatory drivers for conducting site assessment and characterization are often state lead and there's significant variability between different states as well in terms of implementation sampling analysis.
PFAS uses very specific methods and we'll talk more about these in the next webinar and also the in terms of remediation the primary challenges of PFAS involves degradation the degradation challenge the fact that they are very difficult to remove and ultimately degrade in situ treatment is considered currently infeasible. Pump and treat as a primary treatment approach used at this stage for hydraulic containment of PFAS. The groundwater may be treated using activated carbon or ion exchange, which serve to compensate PFAS mass, but don't remove it. Carbon and ion exchange are also noted to be more effective for the long chain than the short chain. Nanofiltration and improvements in the carbonate ion exchange process are being developed to treat the shorter chain compounds. Another concept worth considering here is the treatment train idea.
The treatment involves coupling some of these technologies that would concentrate a PFAS waste stream and then ultimately degrade PFAS that are separated from the larger waste stream. Ultimately the fate of most PFAS is incineration at this point in time.
How future PFAS releases can be controlled or prevented with so much focus on PFAS and drinking water this idea of limiting future liabilities doing to the practices of handling storage or disposal of PFAS are becoming more important. So the remaining time we'll discuss considerations for PFAS remaining material. Lots of pieces have been released but enormous quantities remain above ground they've been widely used for decades or still be in consumer products and in terms of how to handle these.
Uncertain regulatory outlook does not help how to address these questions. We try to pull together a few considerations for decisions in terms of how to handle manage PFAS above ground in terms of AFFF. The differences between c8, c6 foams may be considered.
This is a concept that seems to be very much in its infancy. We as a society have gotten very used to using PFAS compounds and those are the conveniences that they provide. Finding substitutions…it may take some time and, regarding these society choices, we've gotten accustomed to our stain resistant materials and consumer convenience. The trade-off here, I mean, there's these questions to address such as should
a landfill stop accepting carpet because of the PFAS and if they do should all that carpet be incinerated? What problems would that cause? Measurements of CO2 footprint if that were to be the case…or the other option is that we would have to learn to live with wine stains on our carpet as opposed to having the inconvenience of PFAS in the environment. Another key concept here is understanding of waste streams.
Regarding replacement of AFFF…most firefighting foam was produced between the 1960s and 2000s where the C8, long chain based PFAS type foams. Since the early 2000s the transition has been made towards short chain PFAS compounds. There are some advantages and disadvantages shown on the slide towards the transition from the C8 long chain foams to the short chain foams…the modern foams, the C6 foams contain little to no PFOA or PFOS.
They’re less bioaccumulative, but the trade-off is that they tend to be more mobile in groundwater. Also more difficult to remediate, and less susceptible to removal using some of the standard treatment approaches. Also uncertainty regarding toxicity and there's just less data to the newer compounds. In the long run, the transition to fluorine-free foams is another factor for consideration.
There's a document here with that provides a very interesting perspective on this from the Stockholm Convention if you'd like to take a look at that, there's a link provided on this slide. The Department of Defense is also conducting a substantial amount of research into the fluorine-free foams. Several management considerations are shown here. Personally, I wish there were clearer answers. If a perfect solution exists, I have not found it yet. The IPEN document mentioned in the last slide makes a transition sound simple, but PFAS are so widely used that
It seems to be a problem for which the solution may require more effort than that was which was required to create the PFAS problem in the first place.
So questions here for consideration. I'll leave those there and I'm moving into conclusions, some final summary thoughts…PFAS are very widely used chemicals
And moving away from them may not be easy because the complex mixture and unique chemistry.
It raises some very unique challenges compared to compounds we’re used to working. It’s also worth remembering that the problem is bigger than PFOA and PFOS, that there's thousands of compounds that comprise these mixtures. Transport attenuation processes that are unique to PFAS include the idea biotransformation, the idea of interface accumulation and also the importance of atmospheric transport in addition to the more well understood groundwater transport mechanism. On top of all this there's the extremely low levels of concentrations of interest the 70 parts per trillion levels that the EPA has put forward for health advisory levels. What's on the horizon…there's federal and state level responses in the works. EPA's action plan was released about a year ago. This includes progress towards hazardous substance declaration, producing the analytical methods, producing MCLS, and also adding PFAS to the Toxic
Release Inventory. Regarding MCLS, they have apparently made some progress. There has been recent news releases in which the regulatory determination is currently in interagency review and may be up for public commenting in the near future. And the Toxic Release Inventory, which is a database on releases to the environment, which is currently out for public comment. State-level responses vary significantly as well. ITRC provides a good overview of state-specific standards. There's a link to their website on the following slide with resources for those of you to look into down the road. And then also as noted development of fluorine-free foams for firefighting.
Resources are shown here. These will be available in the downloadable version of the presentation. If you'd like to look into any of these for more information, please do…and that concludes the presentation.
Yes, thank you everybody for joining, we hope everyone had an enjoyable experience at today's webinar and we hope to see you April 2nd.
Alright yes, thank you for joining us and we hope to see you then.