Removal of rubber, bitumen and other microplastic particles from stormwater by a gross pollutant trap - bioretention treatment train

Microplastic particles in stormwater pose significant threats to the environment. This study investigated howeffective a stormwater treatment train was at removing rubber, bitumen and other microplastics (incl. fibers,fragments, and paint particles) in the 100–300 μm and >300 μm size fractions from highway runoff. The twotreatment trains comprise a gross pollutant trap (GPT) followed by either a vegetated bioretention cell or nonvegetatedsand filter. Flow-proportional composite samples were taken from the highway runoff, GPT outflowand the outflow from the two parallel filters during nine rain events to determine overall treatment performance,as well as the performance of individual system components.

The identified rubber, bitumen and other microplasticparticles mainly represented the 100–300 μm fraction and included high ratios of rubber (30%) andbitumen (60%). Overall, the treatment train efficiently removed rubber, bitumen and other microplastic particlesin the 100–300 μm size fraction from the stormwater. The filter cells accounted for a major share of this removal,as the GPT did not reduce microplastic particle concentrations. This observation is likely explained by the factthat the rubber, bitumen and other microplastic particles have a density close to the density of water and thusremoval by sedimentation is decreased. This identified an inherent weakness of the system; more specifically, thehigh microplastic concentrations in the surface water of the GPT means there can be a risk of microplastic releasethrough overflow pits when inflows surpass the system capacity. Despite some differences, both the vegetatedbioretention cell and the non-vegetated sand filter removed rubber, bitumen and other microplastic particles tosimilar extent.

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Last updated: 2021-12-06

IVL Swedish Environmental Research Institute

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