The fate of non‐conventional stormwater pollutants in bioretention systems: microplastics, benzotriazole and more

STEP Webinar Series 2021


Conventional pollutants in stormwater include total suspended solids (TSS), nutrients, and heavy metals, but increasingly, attention has been drawn to emerging pollutants such as microplastics and trace organic chemicals associated with household or industrial products, pesticides and pharmaceuticals. In this presentation, Drs. Passeport and Drake will present their findings of recent investigations of the fate of these non‐conventional pollutants in a mature bioretention cell. Dr. Drake will present the results of the first comprehensive microplastic bioretention field study. Dr. Passeport will present results from our 2018 bioretention tracer injection test, which quantified the fate of nutrients and benzotriazole. Additionally, an untargeted analysis of 84 chemicals detected in stormwater and bioretention effluent will be discussed. The results of these studies show that bioretention systems can effectively retain non‐conventional particulate pollutants like microplastics but that conventionally‐designed bioretention systems offer little treatment of dissolved pollutants, including nutrients and polar trace organic chemicals. However, our work provided direct evidence for the microbial transformation and phytotransformation (i.e., uptake and transformation in plants) of our model contaminant, benzotriazole, in‐between consecutive rain events. Ensuring proper use of the soil volume, sufficient retention time, and incorporating additives to strongly retain chemicals and sustain microbial communities are key design and operation strategies that would ensure that the full potential of bioretention cells can be harvested for efficient treatment of an extensive range of stormwater contaminants.


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This webinar is part of the STEP Water 2021 Webinar Series.

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