Study on Removal Efficiency of Nitrogen and Phosphorus from Sewage by Aquatic Macrophtes under Two Cultivation Modes

Based on the laboratory building the small aquatic ecosystem,removal efficiency of total nitrogen(TN) and total phosphorus(TP) by Acorus Calamus,Tonina Fluviatilis and Hygrophila difformis with submerged and emerged cultivation was researched.The results showed that the content of TN was 68.43-279.31 and 23.44-170.13 mg in shoots and in roots,respectively.The content of TP was 9.11-42.79 mg and 10.81-28.71 mg in shoots and in roots,respectively.The highest content of TN and TP was in Hygrophila difformis,and then Tonina Fluviatilis,the lowest in Acorus Calamus.And the content of TN and TP was higher by emerged than by submerged treatment,but it was not significated different at the same spiece aquatics plant.Compared with control,the removal efficiency of TN and TP were significated different with hydrophytes.The average removal rate to TN and TP was 52.0 %-72.4 % and 51.7 %-77.1 %,respectively.The comprehensive evaluation result indicated that,according to plant removal ability to TN and TP,the order was:Tonina Fluviatilis(emerged) Hygrophila difformis(emerged) Hygrophila difformis(subemerged) Acorus Calamus(emerged) Acorus Calamus(submerged) and Hygrophila difformis(emerged).