In addition, the removal rate of NO2−-N was also very high ,which might be attributed to the high growth rate of nitrifying bacteria. However, there was little effect on removal rate ofNO3−-N, which might because the low growth rate of denitrifying bacteria. Thus, the removal rate of TN was not so high, although its removal efficiency of 11.2% by water spinach was significantly higher than 2.9% for Eichhornia crassipes found by Bramwell and Prasad (1995) and of Nyanti et al. (2011). In general, TN removal by water spinachuptake was mainly realized by increasing the tissue N content. From Fig. 4, it can be seen that the nitrogen content in root of water spinach was increased as time elapsed, but not significant increment was observed in stem and leaf, which illustrated that the nitrogen content might be transported from stem and leaf to root, and the stem of plants plays the effect of nutrient element transportation. In addition, plants adsorption might not be a main mechanism for nitrogen removal by water spinach in aquatic water.