Contribution of macrophytes assimilation in constructed wetlands to nitrogen and phosphorous removal.

Macrophyte nitrogen and phosphorous assimilation and its contribution in constructed wetlands(CWs) to nitrogen and phosphorous removal were assessed in this paper.The results showed that the contents of total nitrogen(TN) and total phosphorous(TP) were significantly different among the macrophytes.TN and TP absorption of macrophytes varies from 6.1 to 94.0 g/(m~2·a) and from 0.5 to 9.0(g/(m~2·a)),respectively.Based on nutrient balance in an entire year,only 0.6%-17.3% of TN and 1.4%-41.2% TP were uptaken by macrophytes compared with TN and TP removal by CWs.However,due to a considerable portion of TN and TP which macrophytes absorbed was stored in the biomass of under-ground,only 0.3%-14.1% of TN and 0.8%-19.6% TP were removed by harvesting the macrophytes(above-ground biomass) compared with TN and TP removal by CWs.This shows that the macrophyte nitrogen and phosphorous assimilation could not play an important role for nutrient removal in CWs.More attention should be paid to the selection and utilization of macrophytes and their other ecological effects.