| Due to the characters of small covering, low energy consumption, low construction costs and convenient operation and management, circular vortex grit chamber has been applied more widely in the sewage treatment process. While the hydro cyclone has been paid more and more attention in abroad wastewater treatment engineering because of its simple structure,no transmission parts, large treatment capacity of per unit volume,high separation precision, low cost, small covering and convenient maintenance. Based on foreign circular grit chamber and hydro cyclone, combining with scientific and technological project of Anhui Province (07010202091), this paper designed and made the Cross Flow Swirl Solid-Liquid Separate equipment with High Efficiency which combined the advantages of the first two sets, also it was the equipment conformed to China's development trend and requirements of sewage treatment technical equipments.According to hydrodynamic theory, the prototype of Cross Flow Swirl Solid-Liquid Separate equipment with High Efficiency was designed and put into use in municipal wastewater treatment plant, while, turbidity, SS and COD removal efficiency of sewage in different flow were tested, which were compared with the separation of the fine screen and grit chamber in municipal sewage treatment plant. It was got the optimal flow of 20m3/h and hydraulic retention time of 30s of the Cross Flow Swirl Solid-Liquid Separate equipment with High Efficiency. The results showed that the turbidity and COD removal efficiency of sewage was slightly higher than the sewage treatment plant, the removal efficiency of SS was about the same to the sewage treatment plant and the minimum particle size of sands that can be removed by the device was 0.075mm.The geometric model of Cross Flow Swirl Solid-Liquid Separate equipment with High Efficiency and mesh generation strategies were built with GAMBIT software. A mathematical and physical model was established in the FLUENT solver according to the flow law of motion in Cross Flow Swirl Solid-Liquid Separate equipment with High Efficiency, then the flow field distribution of liquid phase in Cross Flow Swirl Solid-Liquid Separate equipment with High Efficiency was simulated by RNG k-εturbulence model. The process proved to be stable calculation and excellent convergence and the speed simulation values with different distances from the center of some level in the device were got. The results presented the asymmetrical velocity distribution and vortex, meanwhile the flow field distribution conformed to theory .On the Basis of Convergence of the calculation of liquid phase flow field, the particle phase of sands was simulated and the balance forces of sands in Cross Flow Swirl Solid-Liquid Separate equipment with High Efficiency was analyzed based on the model of discrete phase and primarily considering the impact of gravity, drag and rotating centrifugal force and turbulent diffusion on sands. The distribution of sands with different particle size was defined by using Rosin-Rammler distribution function then the removal efficiency and removal efficiency grade of sands on the optimum condition were successfully simulated and the minimum size could be removed by the device is 0.05mm which is close to the test results. Additionally, the motion trail of sands in the device was simulated, otherwise, the movement of sands was analyzed in this paper.The best running conditions of the device was acquired through experiments in the municipal wastewater treatment plant and the removal efficiency of sands on the optimal experimental condition was effectively simulated by using FLUENT. In order to get a higher removal efficiency, a optimization proposal to the hydraulic structures of Cross Flow Swirl Solid-Liquid Separate equipment with High Efficiency was proposed then comparing with the simulation results, it could be seen that the efficiency of dealing with sands of small particle size and floating objects increased after optimization. Following, it was attempted to apply to practice with the original pilot-plant and flow changes were observed, the optimization effect proved to be obvious.
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