浮床植物多样性及组合影响生活污水的净化效果

Plant diversity and composition of ecological floating bed affect domestic sewage purification

Ecological floating bed system has been the hotspot of research and application in the comprehensive management of polluted water environment. In order to analyze the effects of its plant diversity and composition on purification of domestic sewage, we established five species diversity levels and two composition arrangements by using Arundo donax as dominant and constructive species, and measured the plant growth, system productivity and N, P, COD removal rates. The results showed that the individual biomass and relative growth rate(RGR)of wetland plants(such as A. donax)decreased with increasing species diversity, while the survival and growth of mesophytes were promoted. Higher species diversity decreased the productivity of the system, but increased significantly the removal rates of N, P and COD. At the same level of species diversity, the combination with more mesophytes had lower system productivity than that with more wetland plant species, but the former had higher N, P and COD removal rates. Under the same species diversity and combination, P removal rate was the highest, N removal rate was followed, and COD removal rate was the lowest. Moreover, their removal rates showed a trend of slow decline after rapid increase with time. These results indicate that the species richness and combination of ecological floating bed system can affect domestic sewage purification. In the process, pollutants can be removed by direct absorption and adsorption of plants, but the role of microorganisms may be more important.