SusChem: Collaborative Research: Role of Biofilms in Engineered Infiltration Systems in the Removal of Bacteria in Urban Stormwater

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1511915(Chen) & 1511941(Li)Urbanization has resulted in a significant increase in surfaces which prevent stormwater from infiltrating the subsurface and recharging the groundwater. Instead, stormwater accumulates as surface runoff that can result in streambed erosion and flooding events. The runoff can also pick up contaminants (e.g., pathogens) from the surfaces, which eventually enter and contaminate natural aquatic systems. An important component of this research is to investigate the influence of variation in stormwater chemistry and length of drying periods on the chemical properties and microbial diversity of the biofilms and the efficiency of biofilm-modified engineered infiltration systems to remove bacteria during a storm event.This research is the first to systematically study the effects of biofilms grown under environmentally relevant conditions in engineered infiltration systems on the removal of bacteria from stormwater. The changes in the structure, distribution, and microbial diversity of biofilms in porous media grown under a variety of environmental conditions will be revealed for the first time through confocal laser scanning microscopy and high throughput sequencing. The use of atomic force microscopy for the measurements of interfacial forces between a bacterial colloid probe and biofilms will shed light on how a variety of biofilm structures will influence the interfacial interactions between bacteria and biofilm-modified surfaces and the propensity for bacteria to adhere to biofilms. By coupling pore scale and continuous scale modeling, this work will quantitatively link the influence of biofilms on pore scale hydrodynamics with the rate of bacteria transport and attachment at continuum scale. This research will provide new insights on the mechanisms for bacterial retention during filtration, as well as the remobilization of bacteria during draining in biofilm-modified engineered infiltration systems. This research is transformative because it reveals the intricate relationship between environmental conditions, physicochemical properties and microbial diversity of biofilms, and bacteria-biofilm interactions, which will be relevant to the fields of environmental, chemical, and biomedical engineering. The specific tasks include: 1) characterization of biofilms grown under environmentally relevant conditions in microfluidic cells; 2) probing bacterium-biofilm interactions using atomic force microscopy; 3) column filtration experiments including biofilms grown under environmentally relevant conditions; and 4) pore- and continuum-scale modeling of hydrodynamics and bacterial removal in engineered infiltration systems. Research findings will also be incorporated into undergraduate and graduate course materials and further augmented by the involvement of the PIs and their graduate students in organizing scientific activities for third through fifth-grade students in predominantly African American elementary/middle schools in inner-city Baltimore. Short courses on stormwater reuse-related topics will also be developed for the Nebraska EPSCoR's Young Nebraska Scientists summer camps which are attended by K-12 students, a large fraction of them to be underrepresented minorities.