Analysis of Bioretention Capability in Removing Microplastic Particles from Stormwater

In the field of stormwater management, multiple studies have been conducted on bioretention efficiency in removing common stormwater pollutants (e.g., oil and grease, heavy metals, and nutrients.) However, its application in removing microplastic pollution is still in preliminary stages. This study aims to fill a clear knowledge gap regarding the removal efficiency of microplastic particles in bioretention soil media. Laboratory experiments were designed to evaluate and analyze the effects of bioretention media characteristics with various stormwater parameters. We also try to understand the effectiveness of bioretention systems in sequestering stormwater microplastic particles in the presence/absence of co-contaminants. Experiments were done using a one-factor-at-a-time approach to evaluate individual bioretention or stormwater parameters. A wooden frame was constructed that housed a glass column, peristaltic pump, influent and effluent tanks, as well as a sonicator for thoroughly mixing synthetic stormwater with known quantities of fluorescent microplastic spheres. Water that progressed through the soil column was collected and filtered using vacuum filtration. The filter paper was then analyzed using an Echo Revolve fluorescent microscope to get accurate counts of microplastic concentrations. Multiple blank trials were executed to fine-tune and calibrate the system. Results have recently shown differences in the removal efficiency between 0.04 μm and 0.33 μm polystyrene microspheres. To evaluate the impact of co-contaminants on the effectiveness of microplastic sequestration, further trials are being conducted and analyzed.