Study on Purification Effect of Aquatic Plants in Complex Level Flow Constructed Wetland

Used the two plots of complex level flow constructed wetland which had the same structure and selected different combinations of plant dealing with eutrophic water in rural areas,the purifying effects were analyzed.The results showed that the differences of purification effects of the two plots of complex level flow constructed wetland for TN and NH3-N were significant but not significant for COD and TP.The removal rates of COD,NH3-N,TN and TP were 29.4%,35.7%,43.6% and 65.9% respectively in the No.1 complex wetland which planted rush-Acorus calamus and Canna indica-windmill grass.In the No.2 complex wetland which planted Typha latifolia-Canna indica and Canna indica-windmill grass,the removal rates of COD,NH3-N,TN and TP were 30.6%,49.2%,58.1% and 64.5% respectively.The two plots of wetland stored nitrogen accounted for only 8.13% and 10.72% of the total nitrogen removal in wetlands by plants absorb.However,the presence of plants indirectly affected microbial nitrification/ denitrification which played an important role to improve wetland nitrogen removal rate.The wetland stored phosphorus accounted for only 7.59% and 10.25% of the total phosphorus removal in wetlands by plants absorb.The main contributions of wetlands dephosphorization was from the substrate,and smaller form the plants.