Nitrogen Removal Performance of Bioretention Cells Designed for Phosphorus Control

Poster 216 – Click on poster below to view presentation from author.

Click on poster to view presentation from author.

Carl Betz

The University of Vermont

Co-Authors: Michael Ament, Eric Roy, Stephanie Hurley

Urban stormwater runoff transports a suite of environmental pollutants that can degrade the quality of receiving waters. Bioretention systems, a type of green stormwater infrastructure, have been shown to reduce runoff volumes and remove a variety of pollutants from stormwater. The ability of conventional bioretention media to remove nitrogen (N) and phosphorus (P), however, is variable and bioretention systems can act as a net source of nutrients. This is concerning as excess loading of N and P can lead to eutrophication of surface waters. Drinking water treatment residuals (DWTR) are a byproduct of the drinking water treatment process and have been studied as an amendment for bioretention soil media due to their high metal (hydr)oxide content and associated P sorption capacity. However, very few studies have explicitly addressed the effects that DWTRs may have on nitrogen cycling within bioretention cells. This research investigates any potential benefits or tradeoffs that DWTR amendments have on N removal in bioretention cells. The inflows and outflows of four roadside bioretention cells were monitored for total N, particulate N, dissolved organic N, nitrate, and ammonium concentrations during storm events from the 2019 and 2020 monitoring seasons. Two of the bioretention cells were amended with aluminum-based DWTRs and two served as experimental controls that contained a sand and compost-based media. Field results were compared with laboratory experiments investigating the potential of aluminum-based DTWRs to chemically adsorb or leach dissolved inorganic N to help elucidate mechanisms of N transformations in the bioretention cells. The initial laboratory results suggest that DWTRs have a small potential to leach dissolved inorganic nitrogen but no significant correlations between DWTR amendment and N dynamics were observed in the field.

Post comments and questions for author below.

All posts are publicly visible after review by site administrator. Students’ responses to posted questions is factored into scoring for the poster competition. Finalists announced May 25 and awards presented May 26, 2021.


One thought on “Nitrogen Removal Performance of Bioretention Cells Designed for Phosphorus Control

  1. Nice presentation and very interesting project. Could you comment on dissolved oxygen and redox conditions in your bioretention cell and if you think they were conducive for denitrification to occur? Also, how did your system perform in regards to P remediation?


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