Samantha Black is a Water Treatment Engineer with HDR in West Palm Beach, FL. She is HDR's Internal PFAS Practice Group Co-Chair. Samantha works primarily on emerging contaminant, water quality and applied research projects involving PFAS, 1,4-dioxane, and harmful algal blooms.

Per- and poly-fluoroalkyl substances (PFAS) are compounds of emerging concern in the water industry. PFAS are persistent and stable in the environment due to the strong chemical bond between carbon and fluorine. This utility case study detected PFAS in finished drinking water during the Third Unregulated Contaminant Monitoring Rule with perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) sometimes exceeding 100 nanograms per liter. With the inevitable PFOS and PFOA regulations and recently lowered lifetime Health Advisory Levels, the utility desires the design and construction of a full-scale process to treat PFAS.

To identify an optimal PFAS treatment process technologies should be evaluated using site-specific conditions. Research has shown PFAS treatment effectiveness varies depending on the water source, pretreatment processes, and operations. Therefore, a technology that works for one utility may not work for another. Additionally, treatment effectiveness depends on feed water quality. Testing under site-specific conditions prior to full-scale design of PFAS treatment systems is crucial.

A year-long pilot study evaluating PFAS removal from surface water using granular activated carbon (GAC), ion exchange (IX), nanofiltration (NF) membranes will conclude in September of 2022. Pilot testing GAC and IX involved evaluating multiple media types and operating conditions and observing PFAS breakthrough through the media bed. The NF pilot simulated full-scale design and operated under various recoveries ranging from 80% to 90% while tracking PFAS at sample locations throughout the unit. Additionally, a pilot unit has been in operation to evaluate PFAS treatment from membrane pilot concentrate using multiple GAC and IX under varying empty bed contact times. In addition to PFAS treatability, these pilots have explored full-scale treatment feasibility, treatment of secondary water quality parameters (e.g. 1,4-dioxane, manganese, organics), and operational requirements.

This presentation will provide a background of the PFAS challenges the utility has faced and is addressing, the set up and operation of three pilots, and PFAS treatability from surface water using GAC, IX, and NF. Additionally, this presentation will review the set up and results of pilot testing membrane concentrate with GAC and IX. A year’s worth of piloting lessons learned will be shared.