Before you set out to treat a problem you must first define the problem. Since PFAS comes in many forms, identification of the particular PFAS species can help define the treatment required.
By Phil Farina BS, BA, MS, MBA
Polyfluoroalkyl substances are a group of manmade chemicals, meaning they are not known to occur in nature. These chemicals are different in that they are based on fluorine rather than carbon. Carbon chemistry is the building block of life and, as such, will easily break down naturally in the environment or within our living system. Fluorinated chemicals, unfortunately, are much more difficult to decompose or digest, hence they have been given the moniker, “The Forever Chemical”. PFAS-related chemicals have been around since the 1940s and have found use in a myriad of consumer products from waterproofing of wood, canvas, leather, and fabrics, to food packaging and household products, to cosmetics, including toothpaste. This class of chemicals is ubiquitous, and we find that PFAS chemicals and their sister compound number in the thousands. The sheer number of different species of PFAS chemicals makes it more difficult to control exposure to these contaminants of concern.
Chances of Exposure
Exposure to these chemicals comes from any number of day-to-day activities. PFAS species have been found in drinking water, dairy products such as cheese and milk, soils and groundwaters near waste sites or manufacturing facilities, foods such as fish and meats, and the list goes on and on. The most common source of groundwater contamination is from the use of Aqueous Fire Fighting Foams (AFFF), which were used by the military and municipal fire departments to combat high-intensity fires. These were especially used at airports and at training centers where they practiced fighting fires with AFFF.
One of the main problems with PFAS chemicals is that, unlike carbon-based materials, fluorine-based chemicals do not naturally break down in the environment. The half-life of these chemicals in the environment may be as long as three to five years while recent studies have shown that the human body may retain PFAS chemicals for seven years or longer. These extended periods allow for a continued build-up of PFAS concentration in either the environment or our body.
Recent studies by the CDC have confirmed that 97 percent of the U.S. population has some level of PFAS in their blood, kidney, and/or liver. Most known exposures are relatively low, but some can be high, particularly when people are exposed to a concentrated source over long periods.
PFAS exposure can come from any number of activities. However, the most common are:
• Working in occupations such as firefighting or chemicals manufacturing and processing
• Drinking water contaminated with PFAS
• Eating certain foods that may contain PFAS, including fish
• Swallowing contaminated soil or dust
• Breathing air containing PFAS
• Using products made with PFAS or that are packaged in materials containing PFAS
PFAS chemicals are easily transported in water, both in the vapor phase and fluid forms, allowing them to travel great distances undetected. Rain, groundwater, rivers, streams, etc. are all sources of, and transport mechanisms for, PFAS distribution. One study conducted in the 1980s showed PFAS from the DuPont facility in Deepwater, DE traveled more than 250 miles since the 1940s when production of the fluorinated chemical was the mainstay of the plant.
Current scientific research suggests that exposure to high levels of certain PFAS may lead to adverse health outcomes. However, research is still ongoing to determine how different levels of exposure to different PFAS species can lead to a variety of health effects. Research is also underway to better understand the health effects associated with low levels of exposure to PFAS over long periods, especially in children.
Tackling the Problem
So, how do we tackle this sometimes confusing and often complex problem? How do we remove this material from the environment and safely dispose of it now and into the future? Fortunately, there are positive answers to these questions.
The first step is understanding. Before you set out to treat the problem you must first define the problem. Since PFAS comes in many forms, such as long or short chain, branched or highly branched, and other complex species, identification of the particular PFAS species can help define the treatment required. Some species react better to carbon treatment for example, while other species are more effectively removed via resin or organoclays, each designed for specific PFAS management. It is also critical to understand the extent of the contamination.
Low level contamination, such as you might find with a remediation or construction dewatering project may have PFAS levels under 200 PPT. High level contamination, such as may be found at firefighting training sites, may have PFAS levels over 1,000 PPT. Each of these conditions will require different treatment trains.
Therefore, analysis of the source water is a critical first step in understanding the problem and, thus, developing the most effective solution. Dollars spent on defining the problem, identifying the PFAS species and contamination level, are well spent and can save thousands in the long run when it comes to system design.
Characterization of the Water
Once you know what PFAS species and level of contamination you are dealing with, the next step is the characterization of the water. Since the predominant method of PFAS removal involves reaction with media, it is important to make sure the water is properly pretreated to remove TSS and competing constituents such as oils, VOCs, etc. Adjusting the pH to that near neutral will allow the media to work better and maintain a longer life before exhaustion. Pretreatment may include polymer enhanced filtration, simple settling, use of other media to remove cross contaminations, etc. Knowing the characteristics of the water beforehand will save you grief later. It is very easy to reduce the life expectancy of a media by loading it up with a high level of TSS, where a simple filtration system could have been added earlier to prolong media life.
Define Your End Goal
The next step in the decision process is to define the end goal. Is this drinking water where the target is to remove PFAS to non-detect? Is this a landfill leachate or manufacturing process that only has to remove PFAS to levels low enough to allow for treatment by the local POTW? Is this stormwater that only has to be treated to specified levels then sent to the sewer system for further processing? Is this a permanent system or a temporary remediation project designed to last a year or less? Answers to these and other questions will help create a specific, and cost-effective system design to meet your goals.
It is also important to understand the amount of water to be treated. The flow rate and whether the system is permanent or temporary will help the stakeholder be better prepared to design the right system. Granular Activated Carbon (GAC) requires an Empty Bed Contact Time (EBCT) of twenty minutes. Organoclay requires from five to ten minutes EBCT while resins may require three minutes or less to achieve the desired result. The size of the system will, therefore, vary according to the flow rate. The higher the flow rate, the larger the vessels, and the higher the cost.
Considering Other Media
It should also be understood that under certain circumstances, one media alone may prove insufficient to meet your treatment goals. In this case, a treatment train such as pretreatment followed by carbon media in a lead/lag configuration, followed by organoclay or resin may be required. You may also need a media ahead of the carbon if VOCs or other contaminants will compete with the PFAS in the GAC media. There is no simple black box solution. Every project has a specific need so working collaboratively with your system designer will give you the best outcome. Building the system right the first time will go a long way to securing a positive outcome.
Now that we have defined the initial stages of treatment design, what are the options? We know that carbon is the workhorse media in water treatment. Organoclay, a naturally mined and chemically modified media has grown to be more important in PFAS management. New resins are being designed to manage specific types of PFAS species and have found favor in combination with carbon and or organoclay, or in some cases can be used alone; it is all dependent on the level and type of contamination and the desired outcome. | WA
Phil Farina BS, BA, MS, MBA, is Midwest Business Development Manager for Clear Creek Systems, Inc. Phil has more than 35 years of experience in the design and implementation of
water treatment systems. Phil has extensive knowledge in managing PFAS contamination, remediation of groundwater, and Coal Combustion Residual projects. He manages new market development and market growth strategies in the Midwest. Phil’s technical expertise includes media technology, solids removal, mechanical solids separation technology, and water treatment in all industries especially industrial, power, landfill, and construction. Phil can be reached at (419) 346-8848 or e-mail [email protected].