Capturing Contaminants of Emerging Concern (CECs) with Biofiltration

Biofiltration practices are an urban stormwater treatment practice designed to
capture pollutants such as sediment, nutrients, and polycyclic aromatic hydrocarbons (PAHs), among others (LeFevre et al., 2015, Erickson et al., 2021). The mixed media within biofiltration practices, such as biochar, have the potential to also capture contaminants of emerging concern (CECs) (Ulrich et al., 2015 & 2017), but the effectiveness and best mix design have yet to be determined. This project proposes to measure the effectiveness of media components (e.g., compost, biochar, peat, iron, spent lime, etc.) at common mix ratios to capture CECs using outdoor mesocosm experiments (Question 1). These experiments will optimize the components to balance cost and CEC removal to produce the most cost-effective shovel-ready design.

In addition, existing biofiltration practices will be monitored by the USGS personnel to measure CECs in paired inflow (untreated) and outflow (treated by biofiltration media) stormwater samples (Questions 2 & 3). Results from the outdoor mesocosms will be compared to field-monitored CECs (Question 4) to demonstrate how outdoor experiments can be extrapolated to field installation performance. This project expands upon nearly $296,000 invested by the MSRC and the UMN WRC Stormwater Research Program on biofiltration mesocosm experiments and complements approximately $646,000 that has
been requested from ENRTF (CEC removal by biofiltration). Through this combined outdoor experiment-scale and field pilot-scale study, guidance will be developed to empower water resource planners and managers with a treatment practice design to remove harmful CECs from stormwater runoff and protect Minnesota’s water resources.

Projected outcomes

The objectives of this projects are to answer the following research questions:

  • Which biofiltration media mix ratios of compost, biochar, peat, and iron-sand are optimal for removing CECs from stormwater runoff?
  • Which CECs are present in urban runoff to biofiltration practices and at what concentrations?
  • Which CECs are captured by one or more existing field-installed biofiltration practices, and at what efficiency?
  • Does CEC performance in mesocosm experiments correlate with field-measured capture in existing biofiltration practices?