Experimental Study On Growth Of Microcystis Aeruginosa Under Different Flows

In recent years, many large rivers and lakes in China are faced with varying degrees of water pollution problems and the phenomenon of eutrophication caused the algal blooms. The necessary environmental conditions for algae to grow is the rich nutrients, the slowly flow pattern the suitable climatic conditions include the temperature and light, etc. The current research about the growth of algae is forced on the impact of climatic conditions and nutrients, and there is a little study about the hydrodynamic factors affecting the growth of algae.Microcystis aeruginosa was studied to analysis the impact of flow affecting the growth of algae, with the toroidal rotation sink which is simulating the natural flow of river water. The flowing water affects the growth of algae was studied in the same light, temperature, nutrients and other conditions.The main conclusions are as follows:(1)The Computational Fluid Dynamics (CFD) is used to develop the toroidal rotation sink, the water flow conditions in the sink is changed by adjusting the motor speed. The stability and uniformity of the water flow was confirmed by the CFD simulation and the test results. To ensure the reliability of the experimental results, this equipment does not use the plug-flow device to simulate the natural flow of river water.(2)Microcystis aeruginosa grown in the laboratory and in the natural water were experimented in different flow rates (0～0.50m·s-1) to explore the growth of microcystis aeruginosa in the same light, temperature, nutrients and other conditions. The results show that: microcystis aeruginosa grown in the laboratory and in the natural water grew best with the flow velocity being 0.30m·s-1, the more advantage velocity rang of laboratory microcystis aeruginosa is 0.25～0.30m·s-1 and for the microcystis aeruginosa grown in the natural water is 0.30～0.35 m·s-1. If the flow velocity rose or fell, growth of the alga was affected to a varying extent.(3)Test the change of dissolved oxygen (DO), pH, electrical conductivity and TN, TP in the process of algae growth to preliminary analysis the impact of water flow on it. The algae grows stratified in the water and the growth of algae in different layers of flowing water is better than still water; the change range of DO in different flow rate is little and has the same trend in addition to the static group; the experimental water in different flow rate can reach to the optimum pH for algae growth and maintained at the optimum pH range over a period of time; the electrical conductivity of experimental water in different flow rate changes little and has the same trend, the growth of algae reached the maximum rate at 0.30m·s-1 and the electrical conductivity always in a low level; the changes of nitrogen and phosphorus in different water flows had a significant differences and the phosphorus was the most significant, the reductions of TN and TP were biggest and the microcystis aeruginosa has the best growth at 0.30m·s-1...