Purification of Irrigation Return Flow by Cultivating Rice on Water Surface in Ningxia Irrigation Area

MA Ke-xing1,WU Hai-qing1,ZHU Dong-hai1,MU Xin2(1.Farmland Irrigation Research Institute,Xinxiang 453003,China;2.North China University of Water Resources and Electric Power,Zhengzhou 450011,China)

cultivate rice on surface of water;irrigation return flow;purification

With biological floating-beds,rice can be transplanted on the surface of irrigation return flow and grew in the water without soil.During the experiment,some rice was grown in pools with irrigation return flow and some was planted in the river.Rice growing in farmland was the control group.The studies on their growth status and the purification effect on NH+4-N,NO-3-N,TN were in time.Nitrogen contents and heavy metal contents were examined.The result indicated that:①The removal efficiency of rice cultivated on surface of water by floating-beds was very good.The removal rate of TN in the cultivate pools respectively reached 90.33%.In waterway,the irrigation return flow had a high concentration of TN,so rice grown better,more nitrogen can be bring out from the water.②The heavy metal contents of rice cultivated on surface of water were less than their corresponding heavy metal pollution limits.③Purification of irrigation return flow by plants growing in floating-beds is a comprehensive effect of rice,floating-beds and irrigation return flow.The effect of purification and production can be improved by changing factors properly.