System Optimization Of Water-lifting Aeration In Deep-water Reservoirs

Water-lifting aeration technology is an effective way for in-situ algal inhibitiontechnology in source water reservoirs.In terms of the water quality project in Jinpenreservoir,the submerged aerator running has face the problems of equipment loss, pooroxidation effect in the bottom. Under the constantly impact of water-gas column, It’sdifficult for the aerator to maintain vertical in deep water.To settle the mentionedproblems in operation, the typical operational conditions was adopted as the simulationconditions, of the water-lifting aeration system in Jinpen Reservoir, the algalconcentration field and the flow field outside the water-lifting aerator were simulatedwith FLUEUNT software,the algal inhibition effect and the algae decrease wascompared between two types of aerators during strong strafication season and weakstrafication season, with3typical water depth.in order to determine the appropriateinterval between two water-lifting aerators and prethe aerator type were optimalselected.two-phase flow VOF model was adopted to simulate the flow field under thetypical aeration intensity,the average water velocity at the bottom was analyzed of thereservoir, the installation height of aerator was prefered. The main conclusions can bedrawn as follows:(1) The flow field outside the water-lifting aerator changed periodically as thevelocity of the outflow of the water-lifting aerator changed periodically. Taking the ratioof the algal inhibition zone to the whole flow domain as a target, the worst moment ofthe algal-growth inhibition in one period was determined and the research method ofalgal-growth inhibition using water-lifing aeration technology was established.(2) During the strong strafication season,with the temperature gradient of0.7333°C/m and the aeroelastic cycle of170s,under the water depth of77.25m,87.25m and97.25m, in both typed case, the outside flow field were both characterized by a clockwise circulation on the left and a counterclockwise circulation on the right side.Insubmerged case,the circulation on the right was developted greater.(3) During the strong strafication season, under the water depth of77.25m,87.25mand97.25m, the core algal growth inhibition zone in submerged case was respectively5.88%,3.68%and1.15%higher than that of the non-submerged case.In each waterdepth condition, the surface algae with an initial average concentration of726×104cells/L was all finally reduced by86.8%、88.2%、90.6%respectively.The algae decreasein submerged case was higher than that of non-submerged case,submerged aeratorsbehaved better in algae inhibition.(4) During both strong strafication season and weak strafication season,under eachwater depth,submerged case always showed a better algea control effect, with theadvantages of lower investment cost and easier operation and maintenance,and isrecommended for in-situ algae inhibition in stratified reservoirs.(5) With the VOF model, two operating conditions in Shibianyu Reservior weretaken as the actual reservoir simulation conditions, the regulation of outlet velocitychanging over time was obtained under different aeration. In a velocity cycle, theoutflow velocity peaked in a short time, then declined slowly, the period forDeceleration and increase varied by the aeration amount.The result obtained bynumerical simulation method was more accurate than than by cong ’s analytical solutionmethod.(6) It can be concluded that,the greater the areation amount,the shorter the velocityperiod.The simulated period matched well with the measurement, the air quantity wasrequired to meet certain conditions in order to form a gas bomb,the critical speed wasbetween4-5cm/s.(7) Under the Typical aeration amount of25m3/h in Jinpen Reservoir, withthe installation height of1m or2m, operation aerator would not cause sedimentfloating;when the installation height is0.5m,it may cause sediment floating.Thus it isrecommended that the optimal Installation height of the aerator should be1m.