| Four lab scale constructed wetlands including three emergent macrophytes constructed wetland of Zizania latifolia Staph, Typha latifolia Linn. Phragmites communis Trin. and one submergent macrophytes of Vallisneria asiatica Miki are established to study the growth characteristics of the macrophytes and nitrogen removal efficiencies under low hydraulic load and low nitrogen load conditions. During the experiment, the nitrogen load of the Zizania latifolia Staph, Typha latifolia Linn., Vallisneria asiatica Miki and Phragmites communis Trin. are 0.126～0.252g/m~2.d, 0.141～0.34g/m~2.d, 0.142～0.249 g/ m~2.d and 0.181～0.346g/ m~2.d respectively. The hydraulic retention time is about 10～15 days. The results show that macrophytes grow very well and play an important role in the nitrogen removal. In summer, the macrophytes need a large amount of nutrient and the removal efficiency of total nitrogen, ammonia and nitrate are all over 80%. In autumn the removal efficiency of three form of nitrogen are all over 60%. The removal efficiency of the constructed wetland vary with the macrophytes. During the summer the rank of the removal efficiency are Vallisneria asiatica Miki, Phragmites communis Trin., Zizania latifolia Staph, Typha latifolia Linn., in the autumn are Phragmites communis Trin, Zizania latifolia, Vallisneria asiatica Miki and Typha latifolia Linn..During the experiment, sampled the macrophytes and analyzed the total nitrogen content. The results show that the total nitrogen content vary with different part of the macrophytes. Through estimate the biomass of the macrophytes of the start and the end of the experiment, qualitative the removal of the nitrogen by vegetation uptake. Through analyzed the total nitrogen content of the soil and estimate the removal of the nitrogen by soil retention. During the whole experiment, the removal of nitrogen by vegetation uptake are about 45.8%,25.31%, 18.76% and 46.37% respectively, by soil retention are about 29.03%,...
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