Numerical Simulation In A Circular Secondary Clarifier

The sewage treatment project stresses on the environment benefit and the social efficiency. The construction environmental protection and the ecology society are more and more urgently asked in the society constructs manifests. Urban sewage and sludge processing already became the extremely important question. Sedimentation is a Very important Process in the wastewater treatment; a large number of suspended solids can be removed in this Process. The whole process will be influenced by the effect of sedimentation.Hydraulic Peculiarity has an important influence on the settling tank efficiency. In hydraulic design of settling tank, care should be taken to ensure the smaller recirculation regions and ensure steadier flow velocity on vertical section of settling tank. It is feasible and meaningful to make the numerical simulation on the settling tank or other hydraulic building in the design of wastewater treatment project.The thesis does some research on the circular settling tank, which is used in the wastewater recycle Project of Hefei economic development zone. The computational fluid mechanics principles were applied to numerical simulation and analysis of flow and concentration field of the circular settling tanks. First, an un-static mathematical model for flow and particle concentration fields in the circular settling tank is established, which is based on system Partition and model assumption. Standard k-εtwo equation model and the simplified multiphase Mixture model are used to simulate the fluid velocity distribution and sludge volume fraction in a circular clarifier. Results indicate that the mathematical model can simulate the hydrodynamic characteristics of water flow and concentration field of sludge in tanks well. Furthermore, the mathematical model is applied to calculation of the velocity field of water flow and concentration field of suspended solids in a circular tank under different locations of baffles, different flow velocities at water inlets. By analysis of the calculated results, some advices about the structural optimizations are concluded. We can determine more rational location of baffles and outlets and flow velocity at water inlets, in order to improve operational efficiency.