Evaluation of sorbents and matrix effects for treating heavy metals and per- and polyfluoroalkyl substances as co-contaminants in stormwater

Heavy metals and per- and polyfluoroalkyl substances (PFAS) are two classes of contaminants of environmental and toxicological concern that are found in stormwater. There are limited studies that address their treatment when they occur together as co-contaminants. The objective of this study was to evaluate four commercially available sorbents (Biochar Basic, EarthLite, RemBind (TM), and Calgon F400) for the removal of heavy metals and PFAS from stormwater. A series of synthetic and field-collected stormwaters were used to inform sorbent selection. Due to the significant differences in the chemical properties of heavy metals and PFAS, a series of sorbents (i.e., a treatment train) was selected for optimal removal. Real stormwater collected from the Oregon State University Benton County Green Stormwater Infrastructure Research (OGSIR) facility was characterized in order to determine which matrix components impact sorbent performance. Organic matter in real stormwater significantly decreased PFAS removal efficiencies by RemBind (TM) from 84-95% to 0-45%. Pretreating OGSIR stormwater with Biochar Basic removed suspended solids and resulted in significantly greater removal (20-60% increases) for eleven out of twenty-one PFAS. The final sorbents selected for stormwater treatment were Biochar Basic, which is first deployed for heavy metal removal, followed by RemBind (TM) for PFAS removal.