The Green Origio biological system, a two-stage, solar-powered constructed wetland mesocosm situated in Shanghai Jiao Tong University's plant park was used for nitrogen removal in the institution's landscape water. Whereas the first tank was anaerobic, the second tank containing fully grown Pontederia cordata was operated under aerobic conditions. The system was designed with an overflow by-pass pipe to prevent hydraulic overloading. Pump discharge values of 53, 74, 112, 120, 205 and 270 m3/day were recorded during the study. However, the corresponding flow rate values into the tanks were 16.25 m3/day, 29.47 m3/day, 36.79 m3/day, 50.57 m3/day, 71.38 m3/day and 80.52 m3/day, respectively. Experiments conducted between August and October, 2013 revealed a significant concentration decrease for total nitrogen (TN), ammonia (NH3-N), nitrate (NO3-N), nitrite (NO2-N) and total organic carbon (TOC). Whereas the Multi N/C 3100 Analyzer was used for simultaneous analysis of TN and TOC, the nitrogen fractions were analyzed using spectrophotometric methods. The TN, NO3-N, NH3-N, NO2-N and TOC removal rates under a flow rate of 16.25 m3/day were 55.65%, 75.19%, 74.03%, 95.43% and 29.87%, respectively. TN and NO2-N removal efficiencies of 4.92% and 83.64%, respectively, were observed under a flow rate of 80.52 m3/day. Concentration increase in the effluent caused by washout of accumulated concentrations was noted for NO3-N, NH3-N and TOC.

constructed wetlands, denitrification, hydraulic retention time Pontederia cordata, nitrification
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