Formatted Title
Mitigation System Adaptations for Effective PFAS Removal and Water Resource Sustainability
Background/Objectives
Per- and polyfluoroalkyl substances (PFAS) impacts were identified in surface water runoff that was collected and used for irrigation. Migration of potential impacts became a concern as water from irrigation infiltrated from the surface. Without risk mitigation, use of the collected runoff for irrigation caused potential risk to drinking water sources. A treatment system utilized an adaptive approach to adjust to site conditions and treat PFAS-impacted water, which was then used for irrigation purposes, resulting in infiltrating water replenishing shallow aquifers without introducing risk to downgradient communities. Within four years a problem of migration mitigation became a success story of resource management. While mitigation was the primary objective, sustainability and resource utilization were also important: this project collected, treated, and recycled PFAS-impacted runoff, reusing the treated effluent instead of potable water for irrigation.
Approach/Activities
A technology demonstration project was implemented to treat water and reduce PFAS concentrations in water used for irrigation. The project found bacterial blooms in the surface water required alterations to the original system design and concluded that further improvements were needed to optimize treatment. During the subsequent adaptive approach multiple configurations were tested on site. To optimize the system design, a floating pump intake was installed, which decreased the sediment and biological load on the treatment system and increased treatment efficiency. Percent removals of PFOS/PFOA were evaluated based on influent, midfluent, and effluent PFOS/PFOA concentrations.
Results/Lessons Learned
The initial system configuration was successful in preventing PFOS/PFOA breakthrough for a full year; however, breakthrough in granular activated carbon (GAC) occurred within weeks, resulting in more reliance on treatment by ion exchange (IX) resin. To improve efficiency and reduce costs, an adaptive approach resulted in multiple revisions to the system. Pre-treatment with GAC was determined to be a key step and, when paired with system design modifications, the system became effective at removing PFOS/PFOA with 95 to 100% removal calculated from IX resin effluent. The adaptive approach was able to: decrease biofouling, meet client requirements, treat collected runoff, and divert treated water for irrigation utilization and subsequent infiltration to the aquifer. What once posed a potential risk to downgradient drinking water wells became a responsible use of an unexpected water source, benefiting the site, surrounding communities, and the environment.