Research On The Seasonal Variation Of Algae And The Effect Of Algae Control With Water-lifting Aerator In Lijiahe Reservoir

In order to explore the changes and main influencing factors of the algae community structure in the drinking water reservoir-Lijiahe Reservoir during the artificially induced natural mixing period,artificially induced natural stratification period and artificially induced forced mixing period,this study was conducted from September 2018 to 2019 In August,stratified sampling was performed on the deepest point in front of the dam of Lijiahe Reservoir.Through continuous monitoring of the algae community and water quality indicators of the reservoir for one year,explored the characteristics of the succession of the algae population structure and the evolution of environmental factors such as water quality in the reservoir at each period after the operation of the water-lifting aerator in the drinking water reservoir,the main influencing factors of the succession of algae community structure were clarified,and the necessity of controlling algae with the water-lifting aerator in the drinking water reservoir.The main research contents include:1)Characteristics of reservoir water quality evolution and water quality evaluation under artificial induction state;2)Seasonal variation law of reservoir algae community structure under artificial induction state;3)Research on the effect of algae control of the water-lifting aerator.The main results and conclusions of this article are as follows:(1)During the artificially induced natural mixing period,the water body of Lijiahe Reservoir continues to mix,the water quality continues to improve,and the water temperature and light intensity decrease.The changes of the above environmental factors promote the succession of the algae population structure;artificially induced natural stratification period,the water body is stable Layer formation,during which the algae is easy to explode,the thermocline layer is anaerobic due to the accumulation of deposited algae,and the presence of the thermocline layer blocks the transfer of dissolved oxygen and nutrients,the bottom is anaerobic,the release of pollutants,nutrients Increased concentration;during the artificially induced forced mixing period,the anaerobic state of the bottom water body is improved due to the operation of the water-lifting aerator,and the dissolved oxygen concentration is greatly increased,inhibiting the release of pollutants in the bottom sediment.(2)The algae density of Lijiahe Reservoir has been at a low level during the artificially induced natural mixing period,with a minimum of 70×10~4cells/L.Cyanobacteria of the Chlorella and Cyclotella are the main dominant algae during this period,accounting for more than 80%.During the artificially induced natural stratification period,the algae density in the Lijiahe Reservoir continued to increase,and then reached a peak of 3200×10~4 cells/L.The main dominant algae species during this period were Navicula and Synedra,which accounts for more than 80%,is mainly distributed in the surface water body;during the artificially induced forced mixing period,with the continuous mixing of the water body,the algae density continues to decline,and the dominant algae species become chlorella during this period.(3)During the artificially induced forced mixing period,the water-lifting aerator can directly aerate the anaerobic zone of the water body,thereby eliminating the anaerobic environment at the bottom of the water body,and achieving the effect of inhibiting the release of pollutants in the sediment.On the other hand,the water-lifting aerator can promote the mixing of water,so that the algae in the high-density surface area can be transferred to the low-temperature area in the bottom layer to achieve the effect of inhibiting the reproduction of algae.Reduction,the algal density decreased from the highest 3200×10~4 cells/L to about 56×10~4 cells/L,and the reduction rate of algae reached 98%.At the same time,the structure of the algae community changed significantly.The proportion of Navicula and Synedra has been greatly reduced,and Chlorella has replaced it as the main dominant algae species.