Study On The Regulation Of Establishment And Optimization Of Radial Flow Secondary Sedimentation Tank Model Based On CFD In Cold Area

Songhua River comprehensive treatment is to restore the important means of the Songhua River water environment, and the coastal sewage processing plant design and construction bear important point source pollution reduction work. The secondary sedimentation tank as a sewage treatment plant of a important structures. It restricts the final effect. Poor depth in light of this, this topic in the "Twelve-five" National Science and technology major special project "Majiagou urban sewage emission reduction technology integration and demonstration project" support to carry out based on CFD cold radial flow sedimentation pool research work, the cold regions research radial flow sedimentation tank mathematical model is established and the simulation of structural parameter optimization and actual operation parameters change on precipitation, improve the secondary clarifier flow, in order for the demonstration project to provide efficient and reliable technical parameters to solve the secondary sedimentation pool covers an area of large, the flow is not uniform in the solid-liquid separation effect, so as to guarantee the actual sewage treatment plant secondary sedimentation tank operation effect.Secondary clarifier is an important structures in sewage treatment process. Its main function is removal of large amounts of suspended solids through solid-liquid separation, the settlement process is, directly affects the efficiency of wastewater treatment process. Secondary settling pool hydraulic properties on pool suspended solids sedimentation has great influence, in the secondary settling tank design should be through optimization of various structure parameters, as far as possible to reduce secondary sedimentation pool recirculation zone area, the pool in the vertical section on flow pattern uniform.In this paper, in Harbin City in a wastewater treatment plant in radial flow type secondary sedimentation tank as the simulation object, using computational fluid dynamics of the velocity field and concentration field of mathematical modeling. Through the analysis of the RNG K-e two equation turbulent model and mixture multiphase model, respectively on pool flow velocity field and concentration of suspended substance field was simulated, the wells in sedimentation tank test on the actual running results based, compared to verify the accuracy of modeling in the model and rationality, to determine the simulated velocity field and concentration field with the actual situation with and carries on the analysis, it is found that the second sedimentation tank exist obvious density current and the backflow phenomenon, pool water flow distribution is not uniform.Modeling method have been determined by use of the secondary sedimentation tank structure parameters under different working conditions are simulated, the main structure parameters include inlet guide tube, a water outlet and the proposed a spoiler form. After analysis of the proposed secondary sedimentation tank structure design parameters optimization scheme, determine the draft tube submerged depth and secondary sedimentation pool center height ratio should be controlled in the 0.50~0.58 and draft tube radius and second sink pool radius than control in 0.065~0.069 effluent settings for the built-in bilateral weir, position control at a distance of pool wall 2.0m. Determines the level of spoiler to reduce water density current phenomenon and recirculation zone area as a means, to determine the distance of the draft tube optimal vertical distance control in 1m spoiler.Use the modeling method which have been identified in of the form and structure optimization is completed secondary settling tanks with different operation parameters under different working conditions are simulated, the main operating parameters include inlet velocity, suspended particle concentrations and suspended solid particles size and density. Determine the inlet velocity 0.10m/s for the secondary sedimentation tank optimum operating conditions to determine can be realized within the scope of the concentration of suspended matter in the smaller, suspended solid particles particle size, density is, the sedimentation effect more favorable in the proposed by way of adding flocculant to artificially increase the suspended solid particles size and density to improve the secondary sedimentation tank running efficiency.Through the local engineering economic analysis and comparison, Research Institute of technology parameter save area of 33.3%, saving secondary sedimentation tank with a total investment of 29.5% can reduce cold region radiation flow secondary clarifier influent density current in a pool of backflow phenomenon, improve secondary sedimentation tank operation efficiency, improved for the efficient operation of the sewage treatment plant, the water quality of Songhua River to provide technical support, both of wastewater compliance emissions, sewage treatment plant to achieve energy-saving emission reduction requirements is of great significance, and with the life of the residents close contact, have far-reaching significance to our construction of environment friendly society.