Evaluation of Nitrogen Removal and Fate within a Bioinfiltration SCM

A bioinfiltration stormwater control measure (SCM) on Villanova University's campus was constructed in 2001 as a parking lot median retrofit in a residential student area. This SCM effectively mitigates stormwater runoff, including nutrients, and the study described in this paper comprehensively examines nitrogen removal. Both surface and subsurface stormwater samples collected throughout the site during the past nine years have been tested for nutrients, and, in particular, nitrogen species, which is the focus of this study. This objective is achieved by analyzing water quantity and nitrogen data to determine the fate of nitrogen in the bioinfiltration system from both surface and subsurface viewpoints. Parameters of interest are total nitrogen, total kjeldahl nitrogen, nitrate-nitrite, and nitrate. Stormwater samples are analyzed from inflow to outflow on a concentration and mass basis. Discharge for the system occurs as infiltration into in situ soil; any overflow leaves as outflow from a converted storm drain. Additional samples in surrounding background lysimeters and wells were tested for nitrogen species to compare with bioinfiltration samples. Results from the research will provide further insight on long-term water quality performance for an aged bioinfiltration stormwater control measure.