Development, Evaluation, and Technology Transfer of BMPs for Optimizing Removal of PAHs, PCBs, PFAS, and Metals from Stormwater at DoD Sites

SERDP project number ER18-1230 was designed to create and evaluate a novel bioswale design, utilizing a treatment train of sand, plants, and sorbents, for the removal of polycyclic aromatic hydrocarbons (PAHs) (and their toxic degradation products), polychlorinated biphenyls (PCBs), per- and polyfluoroalkyl substances (PFASs), and heavy metals (Cu2 and Zn2 ) from contaminated stormwater at relevant DoD sites. Of the five sorbents tested (bioswale soil, granulated activated carbon, Biochar Basic, EarthLite and RemBind), Biochar Basic demonstrated superior removal of heavy metals and RemBind demonstrated superior removal of PFASs under clean synthetic stormwater conditions. Under real stormwater conditions, all supports demonstrated significant decreases in removal capabilities and suggested that a pretreatment stage may be necessary. Additional experiments were conducted to determine which water quality constituents were key to remove during pretreatment. Ten plant species located in our research bioswale (both grasses and broad leafed) were evaluated for their ability to remove heavy metals. In general, broad-leafed plants showed superior Zn2 removal (especially checker mallow, yarrow, and salal) while grasses showed superior Cu2 removal (especially slough sedge and dense sedge). A pilot-scale implementation utilizing sorbent column studies generated new protocols to characterize the capture and movement of sediments through the bioswale using silt sized (~20 mm diameter) fluorescent-magnetic tracers and fluorescent probes. These findings were integrated in the stormwater management model (SWMM) for the design of a pilot treatment train and further implementation of SWMM model.