PFAS treatment with granular activated carbon and ion exchange resin: Comparing chain length, empty bed contact time, and cost

Per- and polyfluoroalkyl substances (PFASs) are among the most recalcitrant chemicals ever manufactured and are associated with substantial global environmental challenges. PFAS removal performance of granular activated carbon (GAC) and ion exchange resin (IX) was evaluated and compared using a segmented column system with full scale media under continuous flow conditions. Results from the PFAS breakthrough analysis established via column operation under different empty bed contact times (EBCTs) was used to characterize the mass transfer zone (MTZ) of multiple PFASs and evaluate optimum EBCTs for GAC and IX treatment. The height of the MTZ corresponded to PFAS chain length and functional group, where the poorly removed short chain perfluorocarboxylic acids exhibited the longest MTZ. Elongated PFAS MTZs justified longer EBCTs required for treatment of short chain PFAAs compared to long chain PFAAs for GAC and IX. In addition, a cost sensitivity analysis was employed to demonstrate how unit media cost, changeout frequency, and treatment goal feasibility dictated annual operation and maintenance (O&M) costs associated with GAC and IX installations. IX was found to the most cost-effective adsorbent for the removal of long and short chain PFASs compared to GAC. Results from the cost analysis indicated that adsorbent selection was the most critical factor dictating treatment cost with marginal impact from unit media cost or expected changeout frequency.

Automated summary

Per- and polyfluoroalkyl substances (PFASs) are highly persistent chemicals with significant global environmental challenges. A study comparing the removal performance of granular activated carbon (GAC) and ion exchange resin (IX) for PFASs found that the length of PFAS chains and functional groups determine the mass transfer zone (MTZ) height and optimal empty bed contact times (EBCTs). Cost sensitivity analysis showed that IX was the most cost-effective adsorbent for removing both long and short chain PFASs compared to GAC.