By Tom Muilenberg
As of June 2024, public water treatment plants have five years to comply with legally enforceable maximum contaminant levels (MCLs) for six common per- and polyfluoroalkyl substances (PFAS). In addition to this new National Primary Drinking Water Regulation, the U.S. Environmental Protection Agency (EPA) has designated two PFAS – PFOA and PFOS – as “hazardous substances” under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA, also known as Superfund), which specifically targets companies that release additional PFAS in wastewater.
In the wake of these new regulations, U.S. water and wastewater treatment plants are collectively considering their testing and treatment response and the investments they will need to make to achieve compliance. At an EPA-estimated $1.5 billion annual cost for capital, operating and maintenance expenses, treatment plants should thoughtfully consider their next steps.
Tight Timeframe, But Still Time to Pilot
Under such a time constraint, facility managers may worry that there isn’t enough time to conduct a PFAS pilot, but this is not the case. Given the significant investment of new treatment technology, it’s critical that plants make the right decisions to avoid finding themselves with expensive equipment that cannot achieve compliance or technology that was cheap to buy but expensive to operate. A PFAS treatment pilot study is arguably the best way to design a system that is affordable, meets the specific needs of the plant and can achieve compliance by the June 2029 deadline.
GAC and IX: Remediation Media Tested During Piloting
Currently, the most common solutions for PFAS removal are granular activated carbon (GAC) and ion exchange (IX) resin.
Granular Activated Carbon (GAC) is a long-proven technology for removing a wide range of contaminants, with strong market acceptance and a low operating cost. Able to reduce PFAS to non-detectable levels, GAC works best with long-chain PFAS. Compared to IX, it is better able to remove additional organic contaminants and disinfection by-products. At 10-20 minutes, its empty bed contact time (EBCT) is longer than IX and the filtration rate (linear velocity) is lower, which means the equipment will have a larger footprint and taller tanks than IX, which increases initial capital expenses. Re-agglomerated carbon from specialty grade bituminous coal has proven to provide the optimal performance for PFAS capture.
Ion Exchange (IX) uses anionic resin media that specifically targets PFAS, as IX is negatively charged to attract the positively charged “head” of the PFAS compounds. It offers better removal of both short- and long-chain PFAS than GAC and can reduce PFAS to non-detectable levels (as much as 99.99% removal) using a very short (2-3 minutes) EBCT, allowing for a smaller installation and a reduced capital expense. This single-use media offers the longest life of its kind on the market. On the downside, IX doesn’t perform as well in environments with high total organic content (TOC), which can greatly shorten media life and drive up operating expenses.
With both IX and GAC, spent media must be removed and sent off-site for thermal destruction, which currently is the most common option for destroying PFAS.
A Safe Place to Fail
When designing systems, care is always taken to provide the best design possible. However, sometimes unforeseen issues may arise which can create unexpected performance and hence cost issues. In full-scale installations, these issues may be quite expensive. Pilots provide a golden opportunity to make mistakes on a small scale, when course correction is cheap and easy. Through piloting, plants can test various options without worrying about the cost of failure. This allows utilities to optimize a system and reduce the total cost of ownership – upfront capital expenses as well as long-term operational costs.
Piloting helps manage total costs and reduce financial risk in four big ways.
1. Providing a Clear Picture of Source Contaminants and Water Constituents
Not all public water systems deal with the constant, stable types or concentrations of PFAS. In addition, other non-PFAS contaminants may be present in the water only periodically, or at low enough concentrations to be considered “not there”. A pilot unit operating over months and through various seasons must cope with these changes and may reveal challenges not predicted through a few water quality reports or via in periodic testing. In other words, a pilot study can reveal unknown and “slow to appear” problems, allowing the design team to ensure that the full-scale system will be appropriately designed to account with those problems. In the context of short-chain vs long-chain PFAS, this aspect is especially relevant because not all technologies can remove both kinds equally well.
For example, in the southeastern United States, a water treatment plant wanted to test ion exchange resins to determine how to optimize its system for the smallest footprint. Just a few days into the pilot, the IX media started turning purple, indicating that the source water had a strong concentration of manganese. This trace mineral had not been identified among the chief concerns at the facility because manganese is more prevalent in groundwater, and the source water for the facility was surface water from a nearby lake. When the pilot revealed the presence of manganese, plant operators had an “ah-ha” moment, acknowledging that every spring when air temperatures rise and ice melts off the top of the lake, the lake inverts, churning up the manganese- and iron-rich bottom levels to the surface. This phenomenon happens only for a few weeks each spring, and therefore would have easily bypassed detection with a short pilot (or no pilot). Designing the full-scale system with a manganese pre-treatment system ready for service during the annual lake inversion was far more cost-effective than it would have been as a retrofit.
2. A Chance to Interact with the Technology
A pilot can serve as a test drive for plant staff to discern if a potential system is a match for their protocol, space constraints and other unique site and staff characteristics. Oftentimes this insight can only be gleaned through actual, hands-on interaction with equipment over a long stretch of time. This benefit is key to cost savings and can prevent facilities from selecting equipment that ends up breaking the budget due to avoidable, expensive modifications during construction.
3. An Accurate Forecast of Media Life
Media life is a major component of the total cost of ownership and is best understood by subjecting the media to local conditions over many months. How long media will last depends on several factors – levels and kinds of PFAS, TOC, competing contaminants which may be present and other water characteristics.
One valuable piece of information that a pilot can deliver is which PFAS species breaks through the media first. Some utilities are thinking proactively about their PFAS treatment strategy, designing systems that will remediate all species of PFAS in an attempt to get ahead of future regulations, rather than limit their system to currently regulated PFAS. A pilot can show the full extent of the presence of PFAS in the source water and allow a plant to make a cost-benefit decision on where they want treatment to kick in.
For every facility, fully understanding the water’s makeup over many months is critical to predicting media life and determining which media is the better fit.
4. A Low-Risk Opportunity to Test Something New
Innovations in water treatment are at an all-time high, and through piloting, facilities may discover a superior product that performs well and reduces costs. The small relative cost of piloting is a great low-risk opportunity for plants to take a chance on new technologies or creative configurations of proven technologies. For example, a plant might combine GAC and IX in a way that optimizes the benefits of both treatments – a scenario that can be tested during a pilot.
“It’s critical that plants make the right decisions to avoid finding themselves with expensive equipment that cannot achieve compliance or technology that was cheap to buy but expensive to operate.”
For the Best Results…
Ideally, a pilot should last 12 to 18 months. This is usually long enough to completely exhaust the initial media and capture a full year of changes to the water, minimizing the chance of surprise contamination spikes (such as those that happen seasonally or irregularly because of extreme weather or occasional nearby industrial activity). One key learning is a plant’s exposure to specific PFAS compounds, because there are differences in approaching short-chain vs. long-chain PFAS removal.
While a pilot of three to six months can provide some insight, data from a short pilot will need to be extrapolated. When facilities do this, the data tends to forecast media life with less accuracy, which may lead facilities to overestimate how much life they will get out of their media and be disappointed by higher-than-expected actual operation costs.
Pilots can be conducted on a very small scale or through portable 20-foot containers that are a better simulation of a full-scale installation. While both will reduce the total cost of ownership, small scale pilots cost less, while full-scale pilots provide more detailed and complete information.
Achieve Compliance and Water Quality, Minimize Costs
The costs of a pilot pale in comparison to the potential expenses resulting from poor planning and deploying treatment equipment that has not been tested by actual, localized conditions. Removing PFAS from the water supply to below MCLs while minimizing capital and operating expenses is the chief goal of running a PFAS treatment pilot.
Only about half of treatment plants consider pilots. Across the nation, utilities are racking up major financial losses through avoidable mistakes and incomplete planning. Without a pilot, an investment on this scale can end up needlessly costing the plant millions of dollars over the life of the equipment.
Tom Muilenberg is a global product manager for De Nora Water Technologies. He earned a Bachelor of Chemical Engineering Degree from the University of Minnesota in 1992 and has been working in the water treatment industry for more than 30 years. At De Nora, he focuses on filtration and contaminant removal technologies.
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