Research On Inhibition Of Microcystis Aeruginosa Distribution And Growth Under Stress Of Water-lifting Aeration

Recent years, eutrophication phenomenon in China’s lakes, reservoirs and other water sources has been growing, leading to overproduction of algae and frequent "algae bloom" disasters, which has been a serious threat to drinking water safety. Aiming at the algae overproduction problem because of small mobility and stratification of water quality in water source reservoir, the water-lifting aerator mixture technology was applied to the theoretical study of algae control mechanism. The water-lifting aerator was applied to mix water stratification and destroyed the original algae growth environment. The algae were mixed into the deeper water and were inhibited their growth and reproduction, which were under the common stress of low light, low temperature, high pressure. Microcystis aeruginosa is one of the most algae which cause the "algae bloom" in lakes and reservoirs in China. In this thesis, the floating/sinking motion characteristics and the growth and decay rule of microcystis aeruginosa under the stress of different water depth stress, as well as the algae distribution and the growth and decay tendency around the water-lifting aerator. The main conclusions were as follows:(1) The column-settling experimental results show that Microcystis aeruginosa had specific floating/sinking velocity regular pattern. Microcystis aeruginosa behaved the obvious floating trend between0meter (water surface) and10meter water depth conditions. Under20m water depth, the microcystis aeruginosa showed the weak floating trend. Most of the Microcystis aeruginosa suspended in the water, part of Microcystis aeruginosa floating or sinking under30m water depth. The microcystis aeruginosa showed strong performance of the settlement under40,50,60m three water depth conditions.(2) The simulation experimental results show that Microcystis aeruginosa had different growth and decay regular pattern under different water depth conditions with common stress of light, temperature and pressure. As water depth increase, the net productivity of Microcystis aeruginosa reduced. In surface water, the growth rate of Microcystis aeruginosa was0.0173mgO2/(μgChla·d), and the algae growed quickly; Between10～30m water depth, Microcystis aeruginosa net primary productivity increased slightly. Between40～50m water depth, the net productivity of Microcystis aeruginosa significantly reduced, and the greater water depth the smaller of the net productivity of Microcystis aeruginosa. (3) The mixture multiphase flow model in Fluent was applied to simulate the distribution of Microcystis aeruginosa around the water-lifting aerator. After mixing of water-lifting aerator, the initial algae distribution in0-3m water layer was mixed into the lower water column and the whirlpool area around water-lifting aerator contained fewer algae. The bigger the density of algae, the deeper the algae were mixed and parts of algae were brought into the water bottom. At a depth of60m, pumping aeration equipment spacing within50m of the flow field, the algae net primary productivity of the entire region was-7.73794e-07mgO2/(μgChl.a·d), and it indicated that the algae growth around the whole water range of the water-lifting aerator showed a decline of trend. The simulation results showed the feasibility of the water-lifting aerator to control Microcystis aeruginosa.