1　Introduction

Ecological floating bed technology is a kind of biological treatment technology in situ used for water environment management and ecological restoration.Initially,aquatic plants are cultivated on the water surface of rivers and lakes by soilless culture where plant assimilation and transformation,degradation and plant root adsorption of contaminants are utilized.Pollutions are then taken away from water by harvest of the plants and thus achieving the double result of water purification and landscaping.Recently,researchers have made some structural reforms on the ecological floating bed system.There have been various floating bed systems with a layered structure,such as upper and lower layer floating beds,and three layer floating beds(2007)which include lower,middle and upper.Biofilm and fillers,etc,were added to the system that only composed of aquatic plants,to strengthen the interaction between plants,microbes and the contaminants.

Based on successful experiences at home and abroad of wastewater treatment by using plants,the influences of controllable factors,which include structure technology including hydraulic loading,inflow configuration,planting pattern and plant application and so on,vegetation management,and artificial media,on the purifying effect of the ecological floating bed system are discussed in combination with the application and study of the ecological floating bed technology in China.This paper is an attempt to provide a scientific and comprehensive basis for the use of the ecological floating bed technology for water purification.