A numerical model of flow in sedimentation tanks in Slovakia

Hadi, Ghawi and Kriš, Jozef (2008) A numerical model of flow in sedimentation tanks in Slovakia. Pollack Periodica, 3 (2). pp. 59-73. ISSN 1788-1994

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Abstract

This study describes the development and application of a mathematical model of the two-phase flow regime found in settling tanks. The phases present are water, the continuous medium, and solid, the dispersed phase. The performance of the model is assessed, applying it to two validation cases using solid suspensions as the working medium. These are; a settling tank measuring velocity and concentration. The calculations are presented for two different dispersed phase densities for the experimentally given density difference between the inlet and outlet. Computational Fluid Dynamics (CFD) simulations are employed to assess the effect of extended a baffle at the feed section of a full-scale sedimentation tank for the improvement of solids settling in potable water treatment in Slovakia. It is found that the baffle decreases the inlet re-circulation zone and enhances the settling of solids by directing them towards the bottom of the tank with high velocities. It is noteworthy that even small differences in the particle velocity can cause large changes in the percent of settled particles; in this work, the overall solids removal efficiency increased when using the baffle from 80% to 98% leading to a reduction of the effluent solids concentration of approximately 85%.

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