Research On The Impact Of Flow Velocity On The Eutrophication In Water Body

The outbreak of water bloom is a kind of excessive algae propagation and aggregation phenomena at a certain degree of nutrition, climate, hydrological conditions and ecological environment ,and result which environmental factors combining effects form such as TN, TP, pH, flow rate and dissolved oxygen. The main problems of lake eutrophication are algal blooms make the outbreak of the water body loss the use of functions. The purpose of this paper through the indoors and outdoors to experiment with effects of flow velocity on algae growth, aggregation, to identify restriction flow when algal happened, and through gray incidence order analyzes mechanism on the impact of the flow velocity on eutrophication to provide the basis for the prevention and treatment of eutrophication.Finally,the paper comes to the following conclusions::①This paper conductes indoors and outdoors to experiment with algal growth and comes to a preliminary verification of the existence of the critical flow velocity. At a particular conditions find out the critical flow velocity of the growth of algae.From the indoors experiment, we can discover that water bloom may be take place in 1000 r / min around. From the outdoors experiment, we can find out that water bloom of critical flow velocity should be between 0.08m / s and 0.1m / s.②The change of Chla shows the same trend in different flow velocity, which increased at first, then declined. Chlorophyll a indicates the productivity of algae in water, so that the flow velocity of chlorophyll a indicates the affect to the water body.③Compared with other factors the grey incedence analysis shows that, DO and pH have close relation with algae bloom, analyzing the reasons, DO and pH may be mainly produced by algae photosynthesis, so they have close relation to the colume of the algal growth.④In static condition, the correlation of total phosphorus, total nitrogen, flow, DO, pH and Chla ,is between 0.548 and 0.680; in dynamic condition, the correlation of total phosphorus, total nitrogen, flow, DO, pH and Chla has a substantial increase between 0.656 and 0.994.⑤Through authentication, velocity, TN, TP on the impact of eutrophication uses gray relational combination forecasting model description. Dollar non-linear regression equation with the combination of gray relational model prediction error is relatively small, from the equation we can obtaine a turning point at the flow rate of 0.092m / s, that is, the critical value of velocity.⑥Finally we determine the algal growth model: [Chla] =- 57.962V2 +10.667 V-19.238ln ([TN])-21.597ln [TP] +19.787⑦The Yangtze River at natural nutritional state there is the possibility of algal happened, but did not happen water bloom, with the exception of a lower temperature, the faster the flow velocity may inhibit the growth of algae.