Study On The Water Environment And Effectiveness Of Fountain Aeration For Landscape Lake-bay

Lake is an important part of the terrestrial hydrosphere, is the material storage basin. The water quality of lakes in C hina is not optimistic, The number of eutrophication lakes is about 43.7% of the total number of lakes. In summer, water temperature stratification would appear in deep lake, the DO of bottom water body is low which lead to the endogenous release and provide conditions for the eutrophication. In order to improve the anoxic condition of the bottom water under the temperature stratification, many aeration methods has been developed but it is not suitable for landscape water body.Hydraulic force is poor in fountain Lake Bay, thermal stratification will appear in summer which lead to the decline of DO and nutrients release from sediments, provide conditions for the eutrophication. Considering water quality characteristics and the design requirements of the Landscape Garden Expo, fountain aeration systems were desinge which height and suction depth can change accoding to requirement.The current research on fountain just at a preliminary stage and have not been studied extensively. The key point of this research is: installation and operation mode, mechanism of fountain reoxygenation.The contents and conclusions are as follows:① Research of interannual Variations of water quality,results show that:In spring and summer, the SD was low and the TLI was high.The eutrophic state in the bay area achived light eutropher; The SD was high and TLI was low in fall and winter. The eutrophic state in the bay area was oesotropher or oligotropher.There is a singnificance negative colleration between SD and TLI(R=-0.91,R2=0.80).② Research of interannual Variations of dissolved oxygen saturation,results show that: Dissolved oxygen saturation showed obvious seasonal variations, high in summer and low in winter.The DO saturation achived supersaturated(the max level reached 220%)of surface water in summer,meanwhile the DO was subsaturated in winter hovering around 50%. Viewed from the vertical of water,the DO saturation of surface layer was high and the bottom layer was low and there is a significance difference between the surface and bottom in summer. Obvious stratification existed in summer and disappears in winter, the surface layer is insignificant from the bottom layer in winter. The relationship between water temperature stratification and dissolved oxygen stratification, results show that:Temprature stratification could lead to the stratification of dissolved oxygen, but the temperature gradient is smaller than the dissolved oxygen. The critical temperature of the water temperature stratification is 25℃ and the critical temperature of the dissolved oxygen is 24℃.③ Correlation analysis of water environment factors, results show that: Dissolved oxygen showed a significant exponential relationship with the conductivity, dissolved oxygen was significantly positively related to the oxidation reduction potential and p H. Research on the nutrients found a strong positive link between total nitrogen and total phosphorus of different water layers. But the correlation between total nitrogen and chlorophyll-a, total phosphorus and chlorophylla were not significant which showed that the total nitrogen and total phosphorus were not the limiting factor of lake eutrophication and the eutrophication of water is affected by many other environmental factors.④ Study on the installation and operation mode combine with the preliminary achivements, results show that,In summer, fountain height should choose 1m(DC nozzle) in line with the minimum requirements to landscape;The suction depth should choose 5~7m, the suction mouth should be in the lower body of water but not too deep to contact the sediments. Nozzle can be selected on demand and the suggest operation time should be: 9:00~11:00 in the morning and 13:00~17:00 in the afternoon. During operation we can also stop the reoxygenation according to the need. In winter, fountain height should choose 5m(DC nozzle), excessive height would lead to the energy consumption and the effect of reaeration did not increase significantly. The suction depth changes do not affect the reaeration significantly and the recommend suction depth is 1m. Fireworks sprinklers are the best choice as its reoxygenation effect is good. Suggest operation time should be: 9:00~11:30 in the morning and 15:00~18:00 in the afternoon. In this period of time, fountain could be turn off according to the actual situation.⑤ Analysis of water quality of Lake Bay-the effect of reoxygen, the fountain length is 40 m and designed by line, results show that, Service area of fountain can cover substantially the entire Bay, the service area is 70m×120m. The DO in the fountain is 1mg/L hinger than the DO off the fountain area and improve 40%.But there was another question the uneven of reaeration effect. Since the decline of the dissolved oxygen at the position of 40 m distance from the end nozzle of fountain the service aera decline accordingly.All this lead to the uneven of the effect of reoxygen. Ammonia nitrogen, total phosphorus, potassium permanganate index are in line with or better than surface water standardsⅣ. Total nitrogen will exceed the standard in winter, but would not cause eutrophication of water body.Through the experimental and study on the fountain installation and operation mode, get a set of reoxygenation technical guidance suitable for the similar landscape bay water and provide guidance and basis for the fountain reoxygenation technology.Research and analysis on the water environmental factors and the effect of improving water quality provides a theoretical basis for the further exploration of the mechanism of fountain aeration, the release of nutients from sedime nts and the prevention of eutrophication of water bodies.