Algae Monitoring And Algae Depressing Of Water-lifting And Aeration In Shibianyu Reservoir

With the quick development of the national economy in recent dedicates, thecitizens’ living standard has been improving greatly than ever before. However, thehigher demands have caused worse damages to our environment. The quality of thewater in reservoirs keeps falling down–from nurition to eutrophication and there aremore algae appearing, and all of these facts can directly negatively affect the techniqueof water treatment and the qualityof water. Xi’anShibianyu Reservoir is the reservingsource of drinking water for the city of Xi`an, but recent years the water quality keepsbeing worse, which shows the peek value of the density of algae cells per liter morethan100million. Therefore, this study on the characteristics of algae and the effect ofthe water-lifting is very meaningful and necessary. Through the locale monitoring andsample tests in the laboratory, the main analytical conclusions are as follows:（1）The peek value for the densityofalgae cells in ShibianyuReservoir happensin summer between August and September, which reaches60million units per liter.Additionally, this value of density goes down with the increasing of the depth of water.In spring and autumn, the values are between2million units to5million units per liter.It was found in Shibianyu Reservoir that the algae divided into the4categories41kinds. In April, the main kind is Baeillaophyta; in June, it is Ehiorophyta; in August, itchanges into Cyanophyta which is the main kind of algae causing the algae bloom. Theresult shows that the algae depressing should be taken in the August. Therefore thedepressing also should be taken in the upside of water and mainly used for theCyanophyta.（2）When the water temperature went down from25℃to20℃, the density of algae cells also reduced from20million units per liter to10million units per literrapidly. Thus, it shows that with the increasing of the depth of water the density ofalgae decreases, and at the bottom of water, the density of alga almost reaches thevalue of zero. The density value raised from2million per liter10million per literdramatically as the average sunshine level raise from2000Lx to7000Lx. As aconclusion, it can be said that the density of algae depends on sunshine level andtemperature. In addition, when the number of algae come to a high level，the density ofdissolved oxygen loses to8mg/L, ORP increases slowly to350mV, and electronicconductivity decreases from170to150.（3）The density value of Chlorophyta always reaches the peek value at the timebetween14:00to18:00. At night, the density value decreases rapidly, and theminimum value appears at4:00. Otherwise, the algae could rise and dive alternately byadjusting the buoyancy of itself. The data shows that the max density of algae happensunder the water surface4m to6m, and with the increase of depth the density decreases.According to the effect we could see that the algae could be taken into the bottom ofwater reservoir by water-lifting. Then we can kill them under the low temperature andlack of light.（4）After three days’ operation of Water-lifting aerator, in the center ofWater-lifting aerator, the density has reduced74%than before. While20meters awayform the center of water-lifting the density has reduced68%. Therefore the number ofthe algae only decreased26%in the area50meters away. After9days of operation, inthe center of Water-lifting aerator, the density has reduced96%than before. While20meters away form the center of water-lifting the density has reduced92%. Thereforethe number of the algae only decreased97%in the area60meters away. Thus the ratioof Cyanophyta reduced form91%in the zone without water-lifting to16%after waterlifting. In conclusion, the Water-lifting aerator could effectively depress theCyanophyta.