| The Integrated Oxidation Ditch with Vertical Circle(IODVC)is a new generation of oxidation ditch technology with upper and lower structure.Its reaction zone and solid-liquid separation zone are integrated.Compared with traditional oxidation ditch process,it further reduces the area and operating power consumption.The three-dimensional circulating flow of mixed liquor in oxidation ditch is a unique flow characteristic,which avoids the phenomenon of curve circulation in traditional planar oxidation ditch and has a very good engineering application prospect.According to the structure characteristics of IODVC and the flow characteristics of fluid in the flow field,this paper uses GAMBIT to perform 2D geometric modeling and meshing for IODVC,and uses FLUENT solver to establish the numerical model.A two-dimensional single-phase flow model was established to study the flow field characteristics of the reaction zone and to optimize its structure.Firstly,the feasibility of the model is verified by comparing the simulated and measured values.Secondly,the influence of the offset distance of the IODVC middle baffle on the flow field is explored,and the entropy weight-analytic hierarchy process is introduced to comprehensively evaluate the flow field operating conditions of IODVC.Finally,the influence of rotating condition of aeration rotary brush on flow field was studied by orthogonal experiment.At the same time,the precipitation separator of IODVC plays an important role in wastewater treatment.In this paper,the sewage is simplified into solid-liquid two-phase flow and the sludge particles are regarded as spherical particles of equal diameter.The Mixture model is used to simulate the precipitation separator.The effect of inclined plate and length of diversion plate on the solid-liquid separation efficiency of the precipitation separator is studied.The results show that:(1)Under the evaluation system of entropy weight-analytic hierarchy process,IODVC has the optimal operating conditions when the spacer plate is offset downward by 140mm from the reference point.(2)The fact,distance from the aeration brush to the inlet and the diameter of the brush,have significant effects on the flow pattern in the reaction zone of IODVC.Within the test range,the comprehensive evaluation value of the flow field in the main channel of IODVC is proportional to the two influencing factors.(3)The sediment separator with upper inlet has more efficient solid-liquid separation efficiency,and the average density of mixed liquids at the outlet cross section is reduced to 109.82 kg/m~3.(4)An inclined plate with an angle of 60 degrees is installed,which reduces the average density of the mixture at the outlet cross section by 0.91 kg/m~3.The sludge at the bottom of the precipitation separator can flow more smoothly and automatically.(5)When there is no diversion plate at the intake,the water quality of the outlet is poor.In this study,when the length of the inlet guide plate is 200mm,the hydraulic impact of the inlet fluid on the bottom sediment sludge is the smallest,and the effluent quality is the best. |
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