Dissolved Organic Carbon Source Impact on Perfluoroalkyl Substances Removal from Stormwater Using Activated Carbon and Ion Exchange Resin

The capture and recharge of urban stormwater can augment water supplies in dry regions. To safely use urban runoff, it is necessary to remove harmful trace organic contaminants, especially perfluoroalkyl substances (PFASs). This study assesses the removal of six PFASs from synthetic stormwater with dissolved organic carbon (DOC) derived from straw and compost, which are representative materials observed in stormwater catch basins. Activated carbon (AC) and ion-exchange resin (IX) alone or in tandem are used to assess the impact of DOC on the sorbent performance and lifetime. PFAS breakthrough profiles in column studies are used to model contaminant removal via a 1-D intraparticle pore diffusion model, which is then used to predict contaminant removal under varying environmental conditions. Experimental results show PFAS removal is worst when biodegradable straw DOC is present, indicating larger kinetic limitations to sorption than nonbiodegradable compost DOC. The use of AC and IX in combination shows additive improvements over using the sorbents individually. Modeled parameters from replicate tests show consistency in the predicted breakthrough. With 3 mg/L compost DOC and 80 cm/h face velocity, models show that 50-100 cm AC followed by 12.5-50 cm IX provides long-term PFAS removal, ca. 10 years or 90,000 empty bed volumes.