Mathematical Model Of Inclined Plate(Pipe)sedimentation Tank Applied To Secondary Sedimentation Tank

Inclined plate(pipe)sedimentation tank is widely used in water treatment technology at home and abroad,with the advantages of high removal rate,short residence time,small footprint,is a mature,excellent method to improve sludge sedimentation efficiency,has an important position in the field of water treatment.However,the flow field and fluid flow pattern in the inclined plate(pipe)sedimentation tank are very complex during operation,so it is difficult to fully understand the internal parameters of the flow field in the actual operation test.This research adopts the sewage treatment plant secondary sedimentation tank as the research object,on the basis of horizontal sedimentation basin adding inclined plate(pipe),explores the horizontal sedimentation tank(not inclined plate),inclined pipe sedimentation tank,side-flow lamella tank,the horizontal-side-flow lamella tank in different surface loading,sludge return ratio of mud separation effect.In addition,this study based on the computational fluid dynamics theory,using the commercial computational fluid dynamics software FLUENT to numerical simulation of the above four kinds of sedimentation tank with RNG6)-turbulence model to explore the hydraulic characteristics,and support each other with the test results,the surface,can better explain the test results,the numerical simulation of secondary sedimentation tank,flow pattern of inquiry has a certain guiding significance.In the operation of sedimentation tank,sludge return is a very important factor,especially in the process of continuous sludge discharge,the flow state of the fluid is often greatly disturbed.However,in many numerical simulation of sedimentation tank,sludge return is often neglected.In this paper,FLUENT software was used to simulate the flow state of the fluid in the secondary sedimentation tank under different calculated surface loads and different sludge return ratios.The research results are as follows:(1)on the whole,sludge return ratio has almost no effect on the treatment effect of the sedimentation tank.Only the advection flow-lateral flow inclined plate sedimentation tank has less ability to discharge mud than the mud surface to the bottom row perforation of the outlet flower-wall under the conditions of q=3.0 m~3/(m~2·h)and R=50%,resulting in the rise of effluent SS;(2)when q=1.0 m~3/(m~2·h),all sedimentation tanks showed good treatment effect.When q was raised to 2.0 and 2.5,the water outlet SS of the countercurrent sedimentation tank and the level and side flow inclined plate sedimentation tank still showed good water outlet SS,while the water outlet SS of the horizontal flow sedimentation tank and the side flow inverted v-shaped inclined plate sedimentation tank was the first to rise.When q is raised to 3.0 m~3/(m~2·h),the effluent SS of all sedimentation tanks is raised,but it is still within the level A of sewage discharge level 1;When q reached 4.0 m~3/(m~2·h),the effluent SS of all sedimentation tanks exceeded the standard,and the water quality deteriorated more seriously due to the fact that the sludge interface of the horizontal-sideflow lamella tank exceeded the bottom row perforation of the effluent flower-wall.(3)using ICEM mesh,FLUENT on four kinds of tank under the working condition of the numerical simulation of the calculated for each tank under different surface load of streamline-velocity contours and turbulent kinetic energy contours,the results of numerical simulation and field test results will be FLUENT in combined with the research,the results of numerical simulation results show that the FLUENT field test effluent SS can well explain the cause of the change,and the results of numerical simulation of the flow-flow velocity in the flow pattern and the field test of cloud free surface backflow phenomenon and the"dead zones"have good consistency.