The Experimental Study On The Influences Of Flow Velocity On Algae Growth

Eutrophication and water bloom is typical environmental issues of all kinds oflakes, reservoirs, urban waters, governance eutrophication is important for improvingthe water environment, as well as an important research topic in the field of pollutioncontrol. In addition to measures to reduce pollutant emissions（main nutrient salt）,scholars from various countries are research how to control the growth of algae, reducealgae cell density, thereby preventing the breakout of water bloom. By traditionallyaccepted, algae growth rate have contact with light, water temperature, and nutrientconcentrations, also many scholars believe that flow velocity is one of the factors whatinfluence the growth of algae. Flow velocity is artificially controllable factors for themajority of waters, therefore, it is important to research the relationship between flowvelocity and the growth of algae.Related research, some algae have the critical flow velocity when algae grow best，the flow velocity will limit the growth of algae when it increased to a certain extent,flow velocity value of different algae isn’t identical under different environmentalconditions, the internal mechanism is not yet clear, most research conclusions are notthe same. The purpose of this thesis is researching the relationship between Beijingrivers flow velocity and the growth of typical algae, and the influence of water bloom.By using the comparison and statistical analysis methods, it analyze typical algaegrowth under different flow velocity through laboratory and field test, and establish thecorrelation between flow velocity and the algae cell density in the Tongzi River. Thefollowing conclusions:（1）In pure culture conditions, the critical flow velocity of Microcystis aeruginosais about1.0cm/s, when flow velocity reaches about3.0cm/s, it will grow faster than thestationary control group, a flow velocity greater than2.0cm/s significantly inhibit thegrowth of Scenedesmus obliquus. Different algae have different velocity adaptability.（2）In the test of the mixed algae in raw water, a flow velocity of7.0cm/s does notproduce inhibition, a flow velocity of1.5-2.5cm/s is conducive to the growth of algae, aflow velocity greater than2.0cm/s can significantly eliminate water bloom. For thesame type of algae, the flow velocity of eliminating water bloom and the flow velocity of inhibiting the growth of algae are different, they should be treated differently inresearch and application.（3）Flowmakers in Tongzi River show effect of oxygenating and disturbancingwater body to increase the flow velocity, and play a role for inhibiting blooms.（4）Based Tongzi River, this thesis analyzes and establish a negative correlationbetween flow velocity and algae cell density of various types, it consistent with thetheory and has a important role in the actual project.