| In this thesis, the purification effect of wastewater in ecological engineering of constructed wetland, which sits at Hangzhou, subtropical coastal weather, the role of plant on nutrient removal and the sustainability of system were studied. Results showed:(1) The influent of constructed wetland was worse than V grade of standard of surface water of China, that of the effluent achieved L II grade almost. The purification efficiency varied in line with seasons, hydraulic loading rate and the growth of plants. The total removal rate were 40-50%TN, COD, BOD5, 60-70% TP, KN and above 90% NH/-N.(2) The plants in ecological engineering could remove some of N- P from wastewater. This role could be improved by reaping and it was related to plant species, harvest time and harvest intensity. The proportion of N> P removed by plant was up to 4.5%, 4.8% (Lolium perenne Linn.) and 13.8%> 31% (Coix lacryma Linn.) . Considered from purification and crop yield, Lolium perenne Linn, and Coix lacryma Linn, should be harvested completely from the middle of April to the beginning of May or from the end of July to the beginning of August, respectively. The harvest intensity should keep 2-3 times.(3 ) The organic matter (OM) in wastewater and plant litter led to the accumulation of OM in the substratum . The total accumulation of OM was up to 0.658kg/m2, about 60% of the OM occurred in 0-1 Ocm. It didn't affect the operating ability of constructed wetland and the hydraulic conductivity of system always kept well. Reaping plant and eliminating litter periodically could keep the sustainable ability of constructed wetland.Constructed wetland can be used widely in treating eutrophication, domestic wastewater, sewage dewatering, and Landfill leachate. |
