IWRA Proceedings

Sedimentation is a physical water treatment process using gravity to remove suspended solids from water. Clarifiers are tanks built with mechanical means for continuous removal of solids being deposited by sedimentation. Many factors influence the performance and capacity of settling tanks, Such as, Physico-Chemical, Geometrical and hydraulic influences.

To account for them in terms of process operation and design, mathematical models may be utilised. In this respect, Computational Fluid Dynamics (CFD) model enables the investigation of internal processes, such as local velocities and solids concentrations, to identify process inefficiencies. A general CFD-based simulation strategy is developed based on the specific features and conditions met in practice for potable water treatment. Then, using 2D CFD and SST K-ω model with DPM method, a numerical simulation of flow in the tank was developed by Fluent Software to study and investigate the flow field and performance of the sedimentation tank at the existing water treatment at Armant, Qena, Egypt. It is found that the removal efficiency for the sedimentation at particle size of 20µm to 200 µm was approximately 28.61% to 98.20% respectively and the all particles size more than 200 µm will be trapped. The results of this work give an insight, which can be used to investigate novel designs for production-scale tanks. Of course, because of the complexity of the processes taking place, CFD will not completely replace experimental testing and the partly empirical nature of the design process. Traditional techniques will continue to be used for routine design, but CFD is invaluable for backing up this work and for investigating novel tank designs.