Dissolved Organic Matter and Pretreatment Effects on PFAS Removal by Granular Activated Carbon

ABSTRACT Granular activated carbon (GAC) adsorption is commonly used to remove per‐ and polyfluoroalkyl substances (PFAS) from water. In this study, we evaluated the impact of dissolved organic matter (DOM) concentration and pretreatment on GAC use rates for PFAS removal. Rapid small‐scale column tests (RSSCTs) were conducted using a surface water source with a dissolved organic carbon (DOC) concentration of 4.7 mg/L that was subjected to DOM pretreatment methods and groundwater sources with DOC concentrations ranging from < 0.25–4.6 mg/L. DOM pretreatment methods included three full‐scale treatment processes—coagulation‐flocculation‐sedimentation (CFS), CFS followed by ozonation (CFS‐O 3 ), and CFS‐O 3 followed by biological activated carbon (CFS‐O 3 ‐BAC)—as well as five bench‐scale jar test pretreatments: CFS (Jar‐CFS), powdered activated carbon (PAC) adsorption, magnetic ion exchange (MIEX), and combinations of PAC or MIEX with CFS (PAC‐CFS and MIEX‐CFS). GAC use rates decreased dramatically with decreasing DOC concentration. Also, all pretreatment methods lowered GAC use rates, with MIEX‐CFS, PAC‐CFS, and CFS‐O 3 ‐BAC being the most effective. Both DOM removal (MIEX‐CFS, PAC‐CFS) and DOM transformation during ozonation and BAC treatment enhanced GAC performance. GAC use rates to meet U.S. national drinking water standards for PFAS were estimated for a surface water (DOC: 4.7 mg/L) containing six PFAS at concentrations corresponding to the median and 90th percentile values reported by public water systems with detectable PFAS levels in the Fifth Unregulated Contaminant Monitoring Rule (UCMR 5). GAC use rates ranged from 0.01 to 0.34 kg GAC/m 3 (0.10–2.8 lb. GAC/1000 gal), depending on the employed DOM pretreatment and initial PFAS concentrations. These findings highlight the importance of DOM concentration and pretreatment on GAC performance for PFAS removal.