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Pilot-scale evaluation of adsorbents for removal of per- and polyfluoroalkyl substances and co-contaminants: comparison of removal performance and costs
Marron, Brian
Marron, Brian
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2024
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Per- and polyfluoroalkyl substances (PFAS) are a class of fluorinated synthetic chemicals that have contaminated water resources including groundwater and surface water. Because of PFAS’ persistence, toxicity, and potential to bioaccumulate, strict PFAS drinking water standards are being promulgated worldwide necessitating treatment. Commercial adsorption-based technologies, including granular activated carbon (GAC) and anion-exchange resins (IX) are becoming widely used for PFAS removal but face challenges including diminished effectiveness in the presence of competing adsorbates, relatively low adsorption capacity for perfluoroalkyl acids, and high cost. This study evaluated the performance of three adsorbent medias including granular activated carbon (GAC), ion-exchange (IX), and a surface-modified clay, Fluoro-Sorb 200 (FS), at the pilot-scale in both single media column configuration and three multi-media lead-lag series configurations (GAC-IX, FS-IX, and GAC-FS). PFAS-impacted groundwater with high levels of PFAS, total dissolved solids, organic carbon, and volatile organic compounds was chosen to characterize media performance under challenging conditions. The system was operated to determine contaminant removal performance and calculate media usage rate (MUR), and costs over multiple treatment scenarios including a full-scale treatment application. All multi-media lead-lag series had greater bed volumes (BV) to breakthrough, lower MUR, and lower media costs per unit treated volume as compared to single media columns. Additionally, GAC led lead-lag series and single media GAC columns performed better for treatment goals that also considered co-contaminants and short-chain PFAS, demonstrating the importance of including GAC in adsorptive PFAS removal systems. The selective properties of IX make it one of the higher performing medias for long-chain PFAS removal, however, high concentrations of competitive adsorbates in the groundwater diminished its effectiveness, and for several treatment goals, GAC and FS performed better than IX in single column configuration based on breakthrough curves, media usage rates, and costs. A full-scale treatment scenario (2.2 MGD capacity) suggests that multi-media lead-lag series have a higher total capital cost, but long-term media costs make them a cost-effective option as compared to single media columns, particularly IX.
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