Research On Early Warning Method And In-situ Control Technology Of Diatom Bloom In Tiegang Reservoir

A systematic study was made on diatom bloom in Tiegang reservoir in this thesis. The time and space distribution of algae in Tiegang reservoir were investigated with on-site sampling and in a full year. Synedra was chosen as a representative diatom species. Laboratory tests were conducted to evaluate both the diatom growth rhythm and UV-C irradiation technology, as well as the early warning indexes.A small lake was selected to test the effect of hydrodynamic method for aeration and algae inhibition.The results showed that diatom has strong adaptability to low temperature. It dominates during the winter. It is easy to form water bloom with 106 cells/L in the march of spring when the temperature begins to rise. Long hydraulic retention time is an important impact factor for diatom blooming in Tiegang reservoir.The growth of chlorophyll a is lagging behind the growth of photosynthetic activity obviously. The chlorophyll a grows up quickly when the photosynthetic activity increases to 0.65. Photosynthetic activity and chlorophyll a should be chosen as important biological indexes in early warning of diatom bloom. When the photosynthetic activity of diatom is 0.65, the chlorophyll a of diatom at 1.0 ?g/L and the Synedra cell density at 106 cells/L were suggested as early warning threshold values.UV-C irradiation technology can significantly inhibit the growth of diatom. UV-C irradiation at 50~350 mJ/cm2 has the ability to inhibit the growth of diatom when the initial cell density is 3×107 cells/L. UV-C irradiation at 100 mJ/cm2 is recommeded when the inhibition effectiveness lasts as long as 7 days. If it is required to enhance the inhibition effect, UV-C irradiation at 200~350 mJ/cm2 is preferred.Hydraulic mthod tested in this thesis can obviously promote the circulating and interchanging between surface water and bottom water within the scope of certain waters, enhance the level of dissolved oxygen and algal inhibition effect.This thesis identified the major factors influencing diatom blooming, early warning parameter and its threshold value, in situ control technologis which have practical significance to the prevention and control of diatom bloom in Tiegang reservoir.