| In recent years,cyanobacteria blooms in lakes and reservoirs such as Tai Lake,Chao Lake and the Dian Lake,which are harmful to people's drinking water health.In order to solve the problem of water environment caused by the flooding of cyanobacteria,a new method of mobile pressurized algae control is proposed.It can be contained in the initial stage of cyanobacterial water formation,which is energy saving,environmental protection and efficient,and has a good application prospect.In this experiment,the growth activity,sedimentation stability and algae control effect of pressurized cyanobacteria were mainly studied,which provided theoretical basis for the model of mobile pressurized algae control It mainly includes the following contents.(1)The growth activity of pressurized cyanobacteria under different pressure and illuminance was studied by laboratory experiment,and compared with KMnO4,NaClO and CuSO4.The results showed that the pressure treatment only destroyed the air sac of cyanobacteria,but not the other structure of cyanobacteria cells.After the pressure treatment,the instantaneous activity of cyanobacteria cells did not change,and they still had the ability of growth and reproduction under the appropriate light,but the growth activity was weakened.Under no or weak illuminance(less than 500Lux),cyanobacteria gradually decayed,and the activity of pressurized cyanobacteria decreased faster than that of natural cyanobacteria;under suitable illuminance(500?12500Lux),the activity of cyanobacteria will gradually increase,and the growth rate of pressurized cyanobacteria activity is slightly lower than that of natural cyanobacteria;under high illuminance(more than 12500Lux),the activity of pressurized cyanobacteria will decline faster than that of natural cyanobacteria due to the effect of light inhibition.It was found that the effect of NaClO and CuSO4 on killing cyanobacteria was significant,but KMnO4 was not.However,NaClO can kill algae for a short period of time,which will also lead to concentrated leakage of microcystins in cyanobacteria cells,and kill other aquatic organisms while killing algae.Copper is a heavy metal,which will threaten human health.However,the pressure cyanobacteria sink at the bottom of the water body,and the process of pollution release is relatively slow,which has little impact on aquatic organisms.In comparison,pressure treatment of cyanobacteria is more efficient and more environmentally friendly(2)The resuspension of pressurized cyanobacteria in Tai Lake was studied by field experiment,and the movement speed and anti wind and wave precipitation stability of pressurized cyanobacteria were studied in laboratory experiment,which proved the precipitation stability of pressurized cyanobacteria in large-scale water.The results showed that the proportion of re floating of precipitated cyanobacteria in the depth of 1.0m,1.5m and 2.0m of Tai Lake was only 5.05%,2.29%and 1.89%in 24 hours in sunny days,and less than 3%in rainy days and deep water.When the wind speed is 1.02m/s,2.65m/s and 4.24m/s respectively,93.35%,73.26%and 45.66%of cyanobacteria in the depth of 2.0m water in Tai Lake are in the stable state of precipitation.The proportion of natural cyanobacteria with the floating speed greater than 0.1 cm/min,1.0 cm/min and 3.0cm/min was 82.2%,48.3%and 15.8%respectively,while the proportion of pressurized cyanobacteria with the sinking speed greater than 0.1 cm/min,1.0 cm/min and 2.5cm/min was 73.9%,38.4%and 16.7%respectively.Artificial wave making was carried out in a water tank with a depth of 0.75m Under the condition of waves with a height of 8cm,the precipitation of pressurized cyanobacteria was relatively stable,and the cyanobacteria mainly precipitates at the bottom of the tank.The concentration of cyanobacteria in the surface water is only 20.57%of the average concentration;under the condition of 15cm wave height,the pressurized cyanobacteria are still mainly distributed in the lower layer of the water body,the concentration of cyanobacteria in the surface water body is only 20.13%of the average concentration,and there is no precipitated cyanobacteria to be swept up to the surface of the water body by the wind and waves;under the condition of 25cm wave height,the pressurized cyanobacteria are strongly mixed in the vertical direction,and tend to a linear distribution with less in the upper part and more in the lower part.The concentration of cyanobacteria in the surface water is only 22.54%of the average concentration,and only a few precipitated cyanobacteria are swept up to the surface by wind and waves(3)By monitoring the concentration of chlorophyll a and the number of algae cells in the pressurized enclosure and the control enclosure for 15 consecutive days,the algae control effect of the pressurized treatment was proved.Through the measurement of the photosynthetic productivity of cyanobacteria,the control mechanism of the pressurized treatment on the growth of cyanobacteria was revealed,and the decay rate of the pressurized cyanobacteria at the bottom of Tai Lake was also measured.The results showed that the average concentration of chlorophyll a and the average number of algae cells in the control enclosure increased slowly,reaching the peak value on the 11th day,43.44%and 42.80%higher than that at the beginning of the experiment,respectively.On the third day of the experiment,the average concentration of chlorophyll a and the average number of algae cells in the pressurized enclosure decreased by more than 80%compared with the control enclosure,and reached more than 98%on the 11th day.The concentration of cyanobacteria in the pressurized enclosure showed a vertical distribution of less in the upper part and more in the lower part,and tended to be balanced in the later period of the experiment,and was at a lower level.Under the conditions of small wind wave,medium wind wave and large wind wave,the compensation depth of water body is 1.1m,0.95m and 0.8m respectively.The net growth of cyanobacteria is above the compensation depth,and the net decay of cyanobacteria is below.The net production of algae in the pressurized water column is more than 97%lower than that in the control water.After pressure treatment,the cyanobacteria in the depth of 2.0m in Tai Lake decayed rapidly within 24 hours,and the activity of cyanobacteria decreased by 63.1%,and completely decayed after 120 hours. |
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