Chemical conundrum: How the petroleum industry can deal with the presence of PFAS
March 11, 2021
March 11, 2021
The most common PFAS remediation technology runs into complications when used at petroleum facilities. So, what should you do for treatment?
Petroleum industry: If you haven’t yet, it’s time to start thinking about per- and polyfluoroalkyl substances (PFAS).
While investigative efforts for PFAS have traditionally focused on aqueous film forming foam (AFFF—the kind of foam used for fighting liquid petroleum fires) releases at airports and military bases, some governments are now looking at other industries for PFAS releases. Petroleum refineries, petroleum terminals, and petrochemical production facilities have been identified as other potential PFAS sources.
When it comes to treating PFAS, here’s the thing: granular activated carbon (GAC) remains the most common remediation technology for PFAS contaminated groundwater, but the application of this technology at petroleum facilities can be complicated by other factors. Let’s consider the use of GAC, look at other viable treatment options, and analyze ways that petroleum facilities can effectively treat PFAS.
Now, before I get any further, we should define PFAS. As I’ve written before, PFAS are a class of human-made, fluorine-containing organic chemicals that were developed in the late 1930s. Due to their combined water- and oil-resistant properties, these chemicals have been widely used in industrial applications both as fluorosurfactants (like the AFFF I mentioned above) and as heat-, oil-, grease-, and stain-resistant coatings (such as on textiles and in food packaging). Out of a suite of thousands of PFAS compounds, perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) are the two most used, well-known, and understood. Both are considered toxic and persistent.
In the US, PFAS may soon be listed as a hazardous substance under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), which would change the regulatory status of PFAS and trigger the implementation of a variety of requirements associated with these compounds. In Canada, the recent establishment of Drinking Water Guidelines for the two most common PFAS—and Drinking Water Screening Values for nine additional PFAS—by Health Canada is also expected to mean a greater focus on these compounds as part of source water protection and water treatment activities.
Aside from the petroleum industry—oil and gas firms that have bulk terminals and process oils could potentially have PFAS issues—manufacturing facilities may also need to be concerned since manufacturers use PFAS in many of their processes.
It’s a vital question to ask—and there’s a good chance you might. Petroleum facilities historically include fire-suppression systems that use AFFF, and the operation and testing of these systems can release PFAS into soil, stormwater, process water, and groundwater. These facilities may also use other types of PFAS-containing products in some part of their industrial processes, which means that PFAS could be discharged in industrial wastewater. Also, if you’re buying another property, you could be acquiring a site with significant PFAS impacts.
It’s important to also look at your insurance coverage—is it sufficient to cover what remediation might be needed if there is a PFAS release? Some insurance companies are now excluding coverage for PFAS impacts. From a due diligence perspective, it’s wise to know the liabilities that exist for sites you own and whether you have coverage to address those liabilities.
From a risk-management perspective, you need to think about the risks of having PFAS releases at one of your sites. Could the release pose a threat to the drinking water of a nearby community?
If you’re buying another property, you could be acquiring a site with significant PFAS impacts.
GAC remains the most common remediation technology for PFAS contaminated groundwater. It’s a well-established treatment technology that is widely used to address a range of environmental contaminants in water. GAC is made from organic materials—like coal, coconut shells, and lignite—and is highly porous, allowing it to provide a large surface area for contaminant adsorption.
But there’s an issue if you’re trying to use GAC to treat PFAS at your petroleum site: the presence of petroleum hydrocarbons, or PHCs. PHCs are a class of contaminants, derived from fossil fuels and found in crude oil. When both PFAS and PHCs are present in contaminated water, it can be harder to remediate. The application of GAC technology could be complicated by adsorption site competition and biogrowth. Speaking plainly, the GAC adsorbs the PHCs better and thus is “gunked up” faster when PHCs are present. This makes it harder to treat and remove PFAS through this type of system.
Thankfully, there are some solutions to consider when it comes to co-mingled PHC and PFAS plumes.
I’m proud that one of my colleagues has developed a PFAS design calculator, which designs GAC-type water treatment systems. This tool, developed by Stantec’s Ken Martins, predicts GAC service life for co-mingled hydrocarbon and PFAS contaminants—avoiding “surprise” breakthroughs of PFAS.
Right in the design process, the calculator lets you account for how long the GAC will work before it needs to be switched out. That way, you’re not surprised by PFAS breaking through the treatment system months sooner than expected.
Previously, the design of treatment systems assumed you were just treating PFAS. But as we’ve discussed, PHCs complicate the process. Most PFAS are less strongly adsorbed relative to hydrocarbons of similar molecular weight. The hydrocarbons can displace the PFAS through a process known as chromatographic displacement, like chromatography used for lab analyses. If you haven’t accounted for the co-mingled contaminants, your design is wrong. And your GAC won’t last for as long as you anticipated.
The PFAS calculator accounts for this co-mingling, meaning it predicts the correct GAC loading or rate of use based on the composition of the water you’re treating. So, you can adjust the system design to provide the desired GAC service life and to precisely evaluate the benefits of additional pretreatment, such as discussed below.
In other words: The calculator lets you predict how quickly your GAC will get used up—accounting for the fact that PFAS and hydrocarbons will affect the usage of your GAC—meaning you can better design an efficient treatment system.
Another one of my colleagues, Angus McGrath, is working with suppliers to implement an alternate process that combines different remedial approaches to address high PFAS concentrations in co-mingled plumes. This treatment incorporates the use of PerflourAd, a product developed by Cornelsen and distributed in the US by their partner, TRS Group.
Here, the contaminated water goes through a pretreatment process that pulls out the worst of the contamination, removing PFAS even in the presence of other contaminants like PHCs. This results in lower PFAS—and PHC—concentrations in the pretreated water, such that GAC is much more effective at removing PFAS from the water. This pretreatment system scrubs the water before you put it through your GAC system, preserving the GAC for the final step and leading to cost savings.
AFFF use also results in soil contamination. This alternate process also includes soil treatment using thermal desorption developed by TRS Group: heating soil to boil-off the PFAS and then capturing the vapors. AFFF-contaminated soil also commonly contains PHCs, which boil-off with the PFAS. That’s where PerfluorAd comes in again, pretreating the water so that GAC treatment is cheaper and more effective. The next step is working with other vendors to safely incinerate the PerfluorAd waste and regenerate the spent GAC for reuse.
As I’ve mentioned, the implications of co-mingled PHC and PFAS plumes for the design of water treatment systems requires attention. While GAC remains the most common water treatment method for PFAS, research specific to the use of GAC to remove PFAS—and to remove PFAS from water that contains other co-solutes—is largely lacking. We also need more research to understand the effectiveness of adsorption media for treating other types of PFAS compounds.
Stantec’s Water Group Research Team, led by Joseph Jacangelo, is currently pilot testing ion exchange and combinations of ion exchange and GAC to see if these two adsorbents are more effective at treating more PFAS compounds.
We need further research to understand, and ideally minimize, impacts to PFAS removal efficiency when PHC is also present.
Still, I hope this blog makes you consider the potential impacts of PFAS releases at your petroleum facility, and that you’re aware of the limitations of solely using GAC for treatment. There are other options available, and further research will help improve treatment systems in the future.
Learn more about this fascinating topic in this webinar recording, where we provide an overview of the challenges associated with PFAS in the environment, and the implications these challenges may have for the petroleum industry.