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 of NO3−-N, which might because the low growth rate of denitrifying bacteria. Thus, the removal rate of TN was not so high, althoughits 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)