| Abstract Because of influence of flow on the reciprocating baffled flocculation tank the flocculating time is prolonged, the volume of flocculation tank is increased. In order to solve these problems, reduce the reform cost and keep easy practical technological process, the present hydraulic flocculation tank must be studied. Using small and middle field tests, the arc design for the corner and baffled section of flocculation tank is presented. By the experiments of coagulative precipitation, it can be seen that for improved flocculation tank energy loss is reduced apparently, and reaction time is shortened correspondingly, and the floc properties are improved greatly, as a result water quality turbidity is decreased apparently. Because horizontal-flow sedimentation basin is a succeeding equipment which affects coagulative precipitation directly, and density flow is one of primary flow factors that will break flow field, density flow characteristics in motion is researched in the middle field test. In order to understand hydraulic flow patterns for traditional and improved flocculation tanks, the experiments are taken in the laboratory of Hydraulics. Using P1V(Particle Image Velocimetry) technology eddy motion of flow for different flocculation tanks can be studied. Meanwhile two-dimensional numerical model is set up, and flow field of the flocculation tank is simulated, finally the numerical results and the results of field tests and lab experiments are compared. Main results of the dissertation are as follows: 1. Through the small field tests of coagulative precipitation and the optimum hydraulic conditions, the mechanism and dynamic process of coagulation precipitation are studied and analyzed. 2. By means of the model experiments of reciprocating baffled flocculation tank, improved plans for the tank are presented. And using alum as coagulant, based on the results of on the optimum coagulant dose, the coagulative precipitation is researched under different conditions for two plants of the tank. 3. According to the actual inflow quantity and raw water quality of the water plant. using alum as coagulant and PAM as coagulant aids and selecting the outflow water quality turbidity of the sedimentation basin as an assessment factor for coagulative precipitation effect of improved flocculation tank, the numerical model containing several factors such as inflow volume flow rate, raw water turbidity, outflow turbidity, coagulant aid dose and coagulant dose is established. 4. The density flow in horizontal-flow sedimentation basin is discussed, and the flow field is analyzed, the coagulative precipitation effect for different plans are compared, at the same time the measures of abatement of density flow are discussed. 5. Due to narrow gallery and complex hydraulic flow pattern on the corner in the reciprocating baffled flocculation tank, it is very difficult to measure the full flow field. Therefore, using advanced PIN technology a set of system for measuring the hydraulic flow patterns of the reciprocating baffled flocculation tank can be established in the lab. 6. The eddy motion of flow on the corner of the flocculation tank is studied, and the software of the measurement system can be used, in addition the eddy motion flow is analyzed for different predict conditions. 7. In order to predict the full flow field and test the results of experiments, two-dimensional numerical model for...
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