Nitrogen Removal Performance of Bioretention Cells Modified for Phosphorus Sorption
Betz, Carl W
Betz, Carl W
Citations
Altmetric:
License
License
DOI
Abstract
Urban stormwater runoff transports a suite of environmental pollutants that can degrade the quality of receiving waters. Bioretention cells, a type of engineered raingarden, have been shown to reduce runoff volumes and remove a variety of pollutants. The ability of conventional bioretention cells to remove nitrogen and phosphorus, however, is variable and bioretention soil media can act as a net exporter of nutrients. This is concerning as excess loading of nitrogen and phosphorus can lead to eutrophication of surface waters. Drinking water treatment residuals (DWTR), a metal (hydr)oxide rich byproduct of the drinking water treatment process, have been studied as an amendment to bioretention soil media due to their high phosphorus 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 amendment has on nitrogen removal in bioretention cells. The inflows and outflows of four roadside bioretention cells were monitored for total nitrogen, total dissolved nitrogen, nitrate, and ammonium concentrations during storm events from the 2019 and 2020 seasons. Two of the bioretention cells were amended with aluminum-based water treatment residuals and two served as experimental controls with conventional sand and gravel media. These results were compared with laboratory experiments investigating the potential of aluminum-based DTWRs to chemically adsorb or leach dissolved inorganic nitrogen to help elucidate mechanisms of nitrogen 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 nitrogen removal were observed in the field.
Description
Undergraduate
Date
2021-01-01