Data associated with the manuscript by Zhang et al. The impact of strain-specific biofilm properties on the retention of microplastic in stormwater biofilters

Stormwater biofilters have variable colloidal particle removal efficiencies that may be due to different characteristics of microorganisms colonizing them during normal operation. Little is known about how naturally occurring bacteria modify the surface properties of the filtration media, or how these modifications affect colloidal microplastic removal. We used simulated infiltration through model sand columns to study the impact of colonizing microorganisms on the retention of model colloidal microplastic particles, carboxyl-modified-latex (CML) beads. Four naturally occurring stormwater bacterial strains inhibited bead retention compared to a clean bed in a cell-density independent manner, while a model biofilm forming microorganism (Pseudomonas aeruginosa) enhanced retention likely due to physical straining. Atomic force microscopy (AFM) was applied to analyze interaction energy between CML and each bacterial strain biofilm surface. We found that interaction energy between CML and each strain was significantly different, and we propose that changes in the CML bead retention behavior are related to these differences. In particular, we propose that larger repulsive energy generated by some biofilms prevents close contact of CML to surface required for adhesion. Our evidence suggests that extra-cellular polymeric substances modify media surfaces to alter both adhesion and repulsion of beads. Overall, the work demonstrates how AFM can be used to characterize colloidal-collector interactions and provide insights into mechanisms that could be exploited to improve EIS design and operation. The purpose of this collection is to make available to the public the material necessary to validate the research findings.