| As the eutrophication in water bodies is becoming more and more serious recently, the frequent outbreak of algae in such open water bodies as lakes and reservoirs has already become a difficult problem which is urgent to be solved in the current water environmental field. However, due to the status quo that algal bloom in our country is currently hard to be avoided in the short term, it is of great necessity and urgency to remove algae shortly after the outbreak in order to reduce the detriment of the bloom. This thesis proposes the following content: applying microbubbles(10~30 μm) floatation to eliminate the eruptible algal cells(aggresome); proving the effectiveness of algal removal by microbubble flotation method without addition of flocculants; making clear about the characterization of water-algae separation and algal slag; optimizing the technological parameters for water-algae seperation and algal slag collection, based on which the integrated microbubble floatation setting apparatus for algal removal is developed. The following conclusions have been achieved:(1) Applying the algal water as the inflow for microbubble floatation, the algal aggresome contained in the algae-ladened water are smashed by the rotating impeller of the multiphase pump, which possesses a disadvantage for the adhesion of particles and microbubbles. Consequently, the removal efficiency is only 9~48%. The efficiency proves to be better, reaching to 81% and on average 67%, if pure water is used as the inflow for floatation and the removal rate increases with the rise of the concentration of algal cells(aggresome) in the inflow, testifying the feasibility for removing the bloom of algae in water system by applying microbubble floatation method. Under the conditions of this experiment researches, the optimum operating conditions of algae water separation were as follows: the pure water as the inflow for microbubble floatation, dissolved gas rate 0.25±0.05mL/min, influent water flow rate 400L/h, and pressure was 0.67±0.02 MPa, and the ratio of dissolved air water and alage water was 1.4.⑵ In case of same-concentration inflow water and different gas water ratio, the accumulation trend of algal slag layer is consistent. The layer accumulation is basically completed after applying the floatation for 3 min and the greater the ratio of air-dissolved water to algal water is, the faster the algal layer forms. Under the condition of same gas-water ratio and different algal concentration, algal slag accumulation, thickness of layer and stabilization time rise with the increase of algal concentration. Water content in algal slag formed by microbubble floatation ranks from 96.5% ~ 98.8%. Under the condition of this experiment, the optimal floatation time is 3~6 min and the best interval for algal collection is within 14 min after the completion of floatation.⑶ To secure the inflow safety of the equipment, an inlet chest must be set up with the microbubble floatation equipment, when the flow rate is within 0.6 ~ 1.5 m~3/h, the relationship between the minimum theoretical volume of the inlet chest at the start of the pump(V) and the flow rate(Q) is: V=6.11Q~2-11.43Q+7.73; the decompression unit should be installed to reduce the length after the unit as much as possible; the optimal distribution method of release unit is the radial flow pattern. The microbubble floatation setting has the size of 60×60×60(cm),The optimal technological parameters of microbubble floatation apparatus for algal removal is: ratio of air-dissolved water to algal water 0.3, flow rate 1.2 m~3/h, rate of dissolved air 10% The optimized formula for platform moving rate of the floatation apparatus possessing a 1.5 m~3/h flow rate which aims to ensure the efficiency and the effect of algal removal is: =0.09 m/h( V: flow rate [m~3/h]; S: Service area of the equipment [m~2]). |
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