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Nitrogen reduction by fill-and-drain wetland receiving high pollution stormwater from impervious road generated by the initial precipitation

Various chemical forms’ nitrogen from impervious road stormwater results in challenging nutrient management. This study was performed to monitor and analyze for total nitrogen (TN), organic nitrogen (Org.-N), ammonium nitrogen (NH4–N) and nitrate–nitrogen (NO3–N) in stormwater and the effluent a fill-and-drain (FaD) wetland system designed to treat the runoff, generated by the initial 5 mm precipitation, from the impervious road. The wetland system consisted of a sedimentation tank, stormwater collection and coarse particles separation unit, and a FaD wetland, further reduction for dissolved pollutants. It was operated with moderate mass load elimination for TN (67%), Org.-N (49%), NH4–N (95%) and NO3–N (99%), respectively. The outflow nitrogen was dominated by Org.-N (94.5%) with an averaged concentration of 3.97 mg/L. Meanwhile, the reduction of nitrogen was limited by the conversion of Org.-N inside FaD wetland. Therefore, it is critical to creating effective ammonification conditions for Org.-N reduction through the FaD system treating stormwater.