Purification Of Nitrogen And Phosphorus By Aquatic Macrophytes Wetlands In TEDA Highly Salty Reclaimed River

With the continued development of human society and economy, the overexploitation of natural resource damaged the fragile water ecosystem. As a result of neglecting, the treatment and reuse of wastewater for a long period of time, large amounts of pollutants get into the natural water, making the freshwater polluted. Domestic and abroad practical experience indicate that making reused water as the source of urban landscape waters not only redused the discharge of pollutant, supported a natural environment ,but also abate the water-shortage in cities, advanced the utilization rate of water resources and satisfied the need of the water for the amusement in city.Tianjin attaches importance to control and improvement of water environment. In TEDA, Reused water is ranked as strategic resources for development. More efforts have been maked in sewage recycling project and the infrastructure construction whose main contents are water landscape and water ecosystem. The construction for Tianjin TEDA Landscape River, which uses reclaimed water as the only water source, not only considered the availability of local resources and the water environment conditions, but also integrated the urban water environment improvement with the reclaimed water uses and the urban landscape construction.This paper mainly focuses on the studies of the nitrogen and phosphorus removal in the TEDA high salty landscape river with reclaimed river as only water source, and the eight pilot ecological purification pools with different vegetations. The former shows the concentration changes and removal effect of the nitrogen and phosphorus,by quantitative analysis with water samples of different position in TEDA Landscape River. The latter shows the advantages and disadvantages of different pilot ecological purification technology.The experiment results show the water quality purification function of the TEDA landscape river, offer the forecasting result of the ecological rehabilitation and water purification for engineering project, and provided foundation for operation and management of the landscape river.The key testing results are summarized as follows:(1)The Aquatic Macrophytes complex wetlands, with Scirpus tabernaemontani Gmel, Canna indica, Cyperus iria L., and Typha australlis respectively, have higher nitrogen removal efficiencies than other kinds of purification pools, such as ecological gravel bed, macrophyte and purification fishing ponds. For the complex wetlands, the Typha australlis system has the best performance, and the Canna indica poorest. The influent nitrate concentration has no influence on the efficiency of nitrate removal by the Macrophyte beds.(2) In this study, the Typha australlis wetland has the highest removal efficiency to the total phosphorus and orthophosphate, with the average removal rates of 72.2% and 79.2% respectively. In contrast, the removal rates of total phosphorus and orthophosphate in the Canna indica wetland system were only 51% and 60%, which are the lowest in all of the purification pools.(3) The TEDA landscape river and the purification pools under varying influent concentrations have steady performances and similar purification characteristics, that's high removal rates of nitrate, moderate removal of total nitrogen and lower removal of ammonia nitrogen. The landscape river has a better resistance to the pollutant load change.(4)From spatial distribution, the concentration of nutrient in the TEDA river decreased gradually along the water flow. The removal rates of TN and NO₃-N increased gradually with the increase of influent TN and NO₃-N concentration. The average removal rates of TN and NO₃-N were 63.7% and 92.7%. The average removal rates of TP and PO₄³-P were 64.6% and 83.4%. The content of TN and TP in the TEDA river were directly influenced by the concentration of NO₃-N and PO₄³-P and the purification performances.(5) The nitrogen and phosphorus uptake of the aboveground parts of the plants were not obviously influenced by the growth status and locations of the aquatic plants in TEDA river. The removal of nutrient in river channel which is closely related with the growth period of plants the physiological activity of microorganisms show obvious seasonally.What's more, the paper points out some shortcomings of the research and problems for further research, make prospect to the research direction for the future.