Research On Characteristic Variations And The Controll Of Contaminants From Accumulative Blue-green Algae In Lakeshore

It’s a typical disastrous phenomenon in our country that blue-green algae accumulate in Lakeshore of large shallow lake in the lower reaches of the Yangtze River. Contaminants derived from algae accumulation have caused serious water pollution. And it is extremely urgent to master characteristic variation of contaminants from accumulated algae and take effective measures to control them. Aiming at different traits of accumulative cyanobacteria in summer and autumn season, these paper took Chaohu Lakeshore as the research object, adopted indoor culture and in-situ enclosure experiment respectively to study the law of characteristic variation of pollutants and their responses to the controll. Then on this basis, the controlling effect of pollutants by means of the Large bionic equipment for cyanobacteria removal were studied. What’s more, proposed an idea to control the pollution with a new kind pumping equipment. The main results were as follows:（1） A in-door culture experiment was carried out to simulate high density cyanobacteria aggregation(about 1.3×10¹¹cells/L) in summer. With the condition of 35℃, 6000 lux, accumulative cyanobacteria brought about waterbody with an anaerobic condition, which caused an excess of cyanobacteria decayed and chlorophyll a（chl.a） declined gradually. During cyanobacteria death, ammonia nitrogen（NH₄⁺）, phosphate(PO₄^3-) were the main forms of dissolved total nitrogen and total phosphorus（DTN 、 DTP）. Algae-derived nitrogen and phosphorus nutrients,algogenic organic matter（AOM） released fastly before 5～8d. when the release process was ended, The peak concentration of pollutants added several times, even tens times compared with the beginning of the experiment. Pollutants caused by accumulative cyanobacteria dropped and entered into endogenous circulation resulted from Microbes after 5～8d. Therefore before the fifth day was the ―window period‖ to harvest. It is effective to control contaminants via harvesting during the period. Harvesting could cut down contaminants effectively and slow down the release rate of contaminants. Moreover, the larger the harvesting intensity, the more obvious the control effect.The middle intension（Removal of algal biomass about 88.49%） were the necessary intensity to control AOM effectively.（2） An in-situ enclosure experiment was conducted to simulate a relatively lower density cyanobacteria aggregation（about 4.0×10⁸cells/L） in autumn. Under the condition of fall（the water temperature was 21.62℃～25.57℃）, the alage tended to wither and the chl.a fell gradually. With the decline and the deposition of alage, total nitrogen and total phosphorus began to dropped down after 8d and 3d respectively. Algogenic organic matter became a major source of dissolved organic matter in the enclosures, and fluorescent dissolved organic matter was dominated by proteinoid materials. Harvesting reduced the cyanobacterial biomass by 41.7%, which relieved the ―density dependence of growth‖ of cyanobacteria, which resulted in an increase of in-situ growth rates of cyaobacteria. However chl.a fell gradually which testified harvesting in autumn would not cause a second outbreak of algal bloom. Primary productivity, nitrogen and phosphorus nutrients, Potassium permanganate index were under controll in the harvesting enclosures due to the reduction of cyanobacterial biomass. What’s more harvesting could control the release of algogenic organic matters.（3） In allusion to the current situation of algae accumulation in Chaohu lake shore, the effect to control contaminant by the gill type filter and the thickening properties of vibrating screen in Large bionic equipment for cyanobacteria removal were studied. Through the removal of cyanobacterial biomass, the gill type filter could control nitrogen and phosphorus nutrients、COD_Mn、suspended particulate matter（SS） efficiently. Through the condensation of vibrating screen, the volume of algae suspension could reduce 55.09%～88.98%.（4） Aim at the defect of traditional pumping algae platform, this paper proposed a idea about a newfashioned pumping algae equipment—Floating and gill type pumping algae platform, which can move, condense and adapt to changes in water level. Using simulative device to study the interception property thickening property of the device after laid two kind of isopycnic laid filter material（bristles and wool）. The results showed that the wool could intercept alage entirely, however the bristles slightly low. The thickening property performance test showed that the device which laid wool had a better thickening property than that laid wool. All these laid a foundation for the further research.