IWRA Proceedings

Sedimentation by gravity is a usual and important process in settling tanks to remove suspended solids from water and waste water in water treatment plants. In sedimentation tanks, short-circuiting enlargement of dead zones and high flow mixing problems are caused by circulation regions (dead zones), which can reduce the optimal sedimentation of particles. For proper design of such tanks, the detailed study of the hydraulic characteristics of the sedimentation tanks should be performed. Hydrodynamics of the flow field in these basins is sophisticated. Therefore a numerical simulation (CFD model) has been provided to discover such flow field. Then, Steady state incompressible flow conditions with viscous effect are generally considered in hydraulic numerical modelling. Besides, the SST k- ω turbulence model was used in the numerical calculations. In order to validate the mentioned method, a comparison was performed between the numerical results and the previous experimental data (i.e velocity distribution) which carried out by other authors.

Results depict that the numerical simulation is in good agreement with the previous experimental works and the ability of this model in predicting the velocity profiles and circulation districts. Also, we can conclude that the numerical model by using SST k- ω turbulence model can be used to predicate the hydrodynamics of the flow field inside the sedimentation tank and utilized the results for the proper design of such tanks.