Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7d. Ex Situ PFAS Water Treatment Technologies

Formatted Title:

Meeting the Challenge: Ex Situ PFAS Water Treatment Technologies at Sites with Complex Groundwater Chemistry

Background/Objectives:

Per- and polyfluoroalkyl substances (PFAS) have emerged as a significant concern in water sources worldwide due to their persistence, bioaccumulation, and health risks. The need for effective ex situ water treatment technologies to remove PFAS from contaminated groundwater continues to grow, including at sites with complex and challenging groundwater chemistry. In addition to PFAS, other contaminants such as volatile organic carbon (VOCs), total organic carbon (TOC), metals, naturally occurring organic material (NOM), competing ions, and pH variations can also play a significant role in groundwater treatment system design and operation. Remediation engineers must consider the complex interplay between these constituents to deliver a successful remedy with a system that operates smoothly. This presentation will review the impacts of groundwater chemistry on the technologies and processes involved in removing PFAS from contaminated groundwater.

Approach/Activities:

While engineers strive to standardize groundwater treatment system design, each site presents unique challenges that require careful attention. Various PFAS treatment technologies, including granular activated carbon (GAC), ion exchange (IX), reverse osmosis (RO), and fractionation are commonly employed in groundwater treatment systems. However, successful implementation of these technologies requires a thorough understanding of their attributes, such as pretreatment requirements, changeout frequencies, and waste disposal considerations. With the high capital investment cost for PFAS cleanup, project teams must make informed technology selections that reliably achieve remediation endpoints and remain adaptable to variable geochemistry and changing regulations.

Results/Lessons Learned:

This presentation sheds light on the significant challenges faced in ex situ PFAS water treatment technologies, particularly at sites with complex groundwater chemistry. Installing an RO system without consideration given to constituents that may foul or damage membranes, are present near their solubility limit, or impact waste management when concentrated into a waste stream, could result in the need for major system modifications and cost overruns. Similarly, installing an IX system without consideration for NOM or competing ions could significantly impact treatment, cost, and waste disposal. Furthermore, it is not enough to understand how each groundwater constituent could negatively impact specific treatment technologies. Engineers must identify complimentary technologies that remove constituents at appropriate steps in the treatment process to achieve efficient and reliable system operation. Waste streams from each additional process must also be accounted for, including opportunities for beneficial use. By sharing different approaches to address these challenges, we aim to provide valuable insights and lessons learned. With the appropriate tools and knowledge, it is possible to enhance the effectiveness and efficiency of PFAS removal from contaminated groundwater, leading to improved water quality and protecting people and the environment.

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Kelly Kindgren