Abstract: In order to reveal the essence of water conservation and emission reduction in New Food Chain ecological shed,different current water was flew through the cultivation shelves for studying the effect of water flow velocity on purification.The results showed that using Azolla to decontaminate,the concentration of dissolved oxygen(DO) in the water increased by 0.76～0.96 mg·L-1 per layer,the concentration of ammonium nitrogen(NH+4-N) decreased by 0.94～1.19mg·L-1 per layer,was 5.07～6.40 times and 1.71～2.16 times of using lettuce respectively,which indicated that the effect of Azolla on increasing DO and removing NH+4-N was much better than lettuce.Controlled the water flow at 50mL·s-1,after water flew through one layer of lettuce and three layers of Azolla,the concentration of DO increased by 2.80mg·L-1,the total content of O2 increasing of the system was 504.0mg·h-1,the concentration of NH+4-N decreased by 3.82mg·L-1,the total content of NH+4-N removal of the system was 687.6 mg·h-1.It is obvious that Azolla is the critical plant of New Food Chain ecological shed,which play a important role in water purification.Utilizing Azolla and other plants to decontaminate water body provides new ways for solving the bottlenecks of high-density intensive aquaculture,and realizes zero discharge of sewage in aquaculture in a real sense.

Key words: Food chain, Food chain, Azolla, Decontamination, Ammonium nitrogen, Dissolved oxygen