Debojit S. Tanmoy^ab and Gregory H. LeFevre^ab 

^a Department of Civil and Environmental Engineering, University of Iowa, 4105 Seamans Center, Iowa City, Iowa 52242, USA. 

^b IIHR—Hydroscience and Engineering, 100 C. Maxwell Stanley Hydraulics Laboratory, University of Iowa, Iowa City, Iowa 52242, USA

Urban areas generate high volumes of contaminated stormwater runoff during rain events or when snow melts. Urban stormwater frequently contains complex mixtures of various hydrophilic trace organic contaminants (TOrCs), including many PFAS. Tire wear particles, brake dust, asphalt sealants, waterproof building materials, paints, personal care products, microplastics, cleaning products, firefighting activities, etc. can leach PFAS into urban stormwater. Because urban runoff comes from various non-point sources, passive treatment technologies are generally considered a practical and cost-effective mitigation approach. Green stormwater infrastructure (GSI) such as bioretention cells or rain gardens are now being adopted as a nature-based approach for improving stormwater runoff quality and increasing groundwater recharge. Even though traditional GSI systems can effectively capture various particle-associated contaminants (e.g., suspended solids, pathogens, some nutrients, some heavy metals), polar trace organics like PFAS can pass through the systems and potentially contaminate groundwater and receiving surface water bodies. One viable mitigation strategy to solve this problem could be to use engineered sorptive geomedia that would capture these polar organic contaminants in GSI systems. We recently developed “BioSorp Bead” geomedia by encapsulating powdered activated carbon [PAC] (sorbent), iron-based water treatment residual [FeWTR] (density, sorbent), and wood flour [WF] (growth substrate) in cation-alginate matrices (Ca2+, Fe3+). To investigate the sorption removal performance of the beads, we conducted sorption kinetics experiments with three representative PFAS. Long-chain PFAS removal in the beads (13.1 mg PFOA per g) was greater than short-chain PFAS removal capacity (5.2 mg PFBA per g, 5.1 mg PFBS per g). We also encapsulated two types of white rot fungi (Trametes versicolor or Pleurotus ostreatus) in our beads and demonstrated coupled sorption and biodegradation of acetanilide (a type of tire wear compound). Similarly, encapsulating PFAS-degrading organisms and sorptive materials in BioSorp Beads might also lead to enhanced PFAS removal from stormwater runoff. PFOS degradation was recently reported in lab-scale conditions via an aerobic bacteria (Labrys portucalensis F11). In the future, we are planning to encapsulate Labrys portucalensis F11 in our beads and conduct coupled PFAS sorption and biodegradation experiments. We acknowledge that decreasing PFAS contamination in the environment will have the most positive effect on the environment. Nevertheless, coupled PFAS sorption and biodegradation in GSI systems could induce a significant positive impact on PFAS mitigation strategies and the overall environment.