As municipal water systems across the United States confront new PFAS regulations, utilities face a complex mix of technical, financial and operational decisions. We caught up with Sarah Johnson, vice president of engineering at AqueoUS Vets® who shared some practical insights on PFAS treatment design — from the differences between groundwater and surface water projects to media selection, energy considerations and long-term maintenance. Johnson has 19 years of experience in the water treatment and infrastructure industry, specializing in municipal and industrial water and wastewater treatment systems, water infrastructure, distribution systems, and environmental water issues and well as air treatment.
Water Finance & Management: In your experience working with municipal water systems, what are some different considerations in evaluating PFAS treatment options for groundwater wells vs. surface water?
Sarah Johnson, AqueoUS Vets: The sheer scale difference between a groundwater vs. surface water project is the biggest factor to consider. Groundwater well treatment facilities in a highly populated area are typically going to be treating about 10 million gallons per day (mgd); a surface water plant can generally treat up to 50 mgd. Due to this difference, cost efficiencies of media vary greatly. Pressure vessels used for treating groundwater wells may go through 40,000 pounds of granular activated carbon (GAC) per vessel each change out, but there will typically only be 6-8 vessels onsite. Since surface water plants are typically a larger quantity of water, there is a significantly larger quantity of media required to stock requisite vessels. This difference in quantity can have a serious impact on cost efficiency or treatment methodology.
WFM: What contributes to head loss in PFAS treatment? Is this an important consideration in the planning and design phase? Why is it important to maintain optimal flow?
Johnson: Head loss is caused by the friction of the water traveling through the required piping and the distributor within a pressure vessel. Properly sizing the piping and pump for the vessel, flow rate, or pressure rating is among the most important aspects of planning and design because it determines the degree of success the vessel will have in the treatment system while also impacting the total cost of the project.
Properly analyzing all three zones of the pressure vessel – the inlet, the media bed, and the underdrain – can also make a marked difference in the design of the vessel. While the underdrain is consistently among the most focused on aspects of the design, the inlet distributor can vary greatly between equipment manufacturers and those differences can also heavily impact the utilization of the media bed.
Optimal flow conditions allow the vessel to reach plug flow, which maximizes the adsorption kinetics and grants sufficient time for contaminant migration through the adsorption surface area or mass transfer zone.
WFM: In PFAS removal, how does energy consumption compare to conventional water treatment? What are some of the planning considerations for energy costs?
Johnson: Energy consumption varies depending on the treatment methodology chosen for the given water composition. As with any treatment type, if there is a larger concentration of contamination, it will take more time and material to remove it to reach a treatment goal. PFAS removal in particular does not increase costs in comparison to other contaminants, but the consideration of more treatment requirements than may have previously been needed will increase overall costs.
In planning for these overall cost increases, paying attention to head loss and pressure drop during the design process can save time and money in the long run. Additionally, in colder climates vessels typically require housing to protect against frozen piping. Choosing a design that permits for shorter buildings or the ability to retrofit existing structures through shorter shell walls will lead to higher energy savings.
WFM: Why is total cost of ownership important to understand before committing to a PFAS treatment project? What are some benefits of piloting?
Johnson: Total cost of ownership is critical to understanding what you are really paying for when you install a new treatment system. Mechanical system design can significantly impact the overall cost to the client when given equal consideration as initial filter media costs. At AqueoUS Vets® (AV®), we recognized that knowledge gap and developed with our Four Tenets of Pressure Vessel Design to educate decision makers on why looking more closely at the overall useful lifetime can benefit the clients’ bottom line.
Piloting also offers cost efficiency by allowing an end user the chance to test their water composition against a number of different media and see which is most effective. While there may be an upfront cost to performing the pilot, the overall cost savings provided by reducing the frequency of media change outs and increasing the efficiency of meeting their treatment goals has been proven worthwhile.
WFM: What are some of the key indicators for choosing a particular filtration media? How should a municipal water system evaluate which media to use?
Johnson: Filtration media should be chosen based on the contaminants intended to be treated. GAC, IX resin, and novel media each have their own strengths against particular chemical compounds. The available space for the completed system also needs to be considered – GAC requires longer empty bed contact time than other medias and, in turn, a taller vessel to accommodate the increased quantity of media. In treatment plants located in settled neighborhoods, taller or more numerous vessels can have a greater impact on residents. Choosing the most efficient media that matches the location’s requirements, both chemical and societal, can help owners meet their constituents need for clean water with minimal intervention.
WFM: Does AqueoUS Vets provide training post-installation? Are you seeing any specific or recurring challenges with regard to training utility staff on operations, maintenance, etc.?
Johnson: Yes, AqueoUS Vets offers on-site training as needed by end users both after installation and during start-up. The consideration for long-term operation and maintenance is a cornerstone of AV’s commitment to every installation we are involved with, from concept to commission. We strive to offer a design that is simple and easy to maintain; the external ring header design allows operators to complete underdrain maintenance outside the vessel, eliminating the need for confined space entry certification for standard maintenance.
We have not experienced recurring challenges once initial training is completed. For this reason, training is very straightforward, and utility staff are quick to understand the functionality of our treatment systems.
WFM: How are tariffs impacting the availability of filtration media for the U.S. market? Do you see this being a significant challenge in the coming years as utilities ramp up PFAS compliance projects?
Johnson: There has not necessarily yet been an impact on the availability of media in the U.S., though there has been a marked impact on cost. Most IX resins and certain carbons are unable to be manufactured domestically and thus take a hit on tariffs during their import. The challenge of availability will likely be felt in the next few years when the utilities that are already struggling to procure sufficient funds to test and construct a treatment facility attempt to enter the market among well-established contracts and relationships while lacking the financial strength to maintain a similar maintenance and exchange contract.
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