Numerical Simulation And Optimization Of Orbal Oxidation Ditch Flow Field

Belong to a kind of deformation process of active sludge treatment process, oxidation ditch process develops rapidly in recent decades with the advantages of low cost,easy maintenance,fine water quality,running stability and easy management. However, the oxidation ditch exists the problems of even velocity distribution and sludge sedimentation. CFD has the advantages of simpleness, shortcut and accuracy at the aspect of hydromechanics characteristics of reactor study, and increasingly applied in flow field simulation of domestic and overseas oxidation ditch reactor.On the basis of previous studies, this text utilizes commercial software FLUENT of CFD to conduct numerical simulation on flow field and sludge distribution of Orbal oxidation ditch mixed fluid of the urban sewage treatment plant, and discusses the optimization measures of the oxidation ditch, finally proposes the optimal tank shape of Orbal oxidation ditch, and provides reference for oxidation ditch flow field simulation and design optimization. The main achievements are as follows:Firstly, numerical simulation is conducted on one Orbal oxidation ditch flow field in Chongqing, the oxidation ditch adopts RNG k-ε two-equation turbulence model and mixture two-phase flow model in the process of analog computation, and the MRF model is adopted for the rotation area of the aeration turntable. The simulated results are compared with the measured data of the oxidation ditch, to verify the feasibility of the simulation method used in this paper.Secondly,the simulation method verified is used in another aeration rotary table and underwater propeller driven Orbal oxidation ditch sewage plant flow field numerical simulation analysis, the results show that there is energy waste phenomenon in oxidation ditch, and it is necessary to optimize and improve the flow field of oxidation ditch.Changing the inclination angle of the aeration turntable downstream baffle plate to simulate and analyze flow field of the oxidation ditch to gain baffle plate optimum tilt angle. Changing the number, power and position of underwater propulsion to simulate and analyze flow field and the distribution of the sludge concentration to gain underwater propulsion optimal configuration.Then, analyzing separately optimized oxidation ditch straight section and bend section flow field.Finally, when the total volume, ditch width and ditch depth of the oxidation ditch are not changed, and the length of the oxidation ditch is only changed, determine the size of each kind of tank-shaped oxidation ditch. The aeration turntable parameters are all the same, underwater propellers are both not disposed,and the flow field and the sludge field of the Orbal oxidation ditch are simulated and calculated to determine the optimal pool shape, to provide a reference for future new Orbal oxidation ditch pool shape selection.