Enhanced removal of trace-level per- and polyfluoroalkyl substances (PFAS) from drinking water using granular activated carbon (GAC): the role of ozonation

Granular activated carbon (GAC) is a promising approach for removing per- and polyfluoroalkyl substances (PFAS) from drinking water. However, GAC filters usually suffer early PFAS breakthroughs due to the competition between PFAS and natural organic matter (NOM) during sorption. The present study investigated the possibility of using ozonation to enhance the GAC performance for PFAS removal. Rapid-small-scale-column tests were performed for three GACs using filtered or filtered and ozonated water. NOM was fractionated using liquid chromatography-organic carbon detection (LC-OCD), and 76 ambient PFAS were quantified using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS). Although ozonation did not remove either NOM or PFAS, it altered their composition in water. Ozonation reduced the hydrophobicity and the molecular size of natural organic matter (NOM). On the other hand, ozonation oxidized some PFAS precursors, leading to a higher total detected PFAS concentration in the filtered and ozonated water than in filtered water (10.2 ± 0.7 ng/L vs. 9.5 ± 0.7 ng/L). The impact of ozonation on GAC performance for NOM and PFAS removal mainly depended on GAC properties. GAC with a lower micropore volume showed an improvement in NOM and PFAS removal when ozonation was applied, approaching the performance of GACs with higher micropore volumes.