Numerical Investigation of baffle effect on sedimentation anf flow field in sedimentation tank

Document Type : Original Article

Authors

1 . M.Sc. of Hydraulic Structure, Tarbiat Modares University, Tehran, Iran

2 Hakim Sabzevari University, Civil Engineering

3 Professor, Water engineering department, Tarbiat Modares University, Iran,

Abstract

Sedimentation by gravity is a common, highly applicable separation method for the suspended solid particles of water and wastewater. Sedimentation basin is an important component of every water treatment process. Due to high maintenance costs of these basins, up to about 30% of all costs in a water treatment plant, optimum performance of settling basin is very significant. In order to improve the efficiency of the basin, engineers have proposed various methods, among which, “changing the geometry along with installation of baffle in the basin” is economic and has attracted the attention of researchers. In the present paper, numerical simulation was made by using Flow3D software and RNG k-ε turbulence model for a flow consisting of settlement particles in the rectangular settlement basin by a finite volume method (FVM). This study aims at numerical simulation of the hydraulic flow in settling basins with various baffle configurations, and finally, obtaining the best geometry for the baffle. Considering the relative consistency of the numerical model results and the experimental data, the numerical simulation results were validated using the Flow3D model. The results showed that the flow in the settling basin is severely affected by the baffle. According to the studied models, it is clear that the baffles installed with lower height and closer to the basin inlet and baffles with high height and far away from the basin inlet have the most effective case on the settlement efficiency.

Keywords


خادمی، م . امید، م ح . و هورفر، ع .1385 "مطالعه آزمایشگاهی اثر تیغه هدایت کننده بر راندمان تله اندازی حوضچه رسوبگیر." هفتمین کنگره بین المللی مهندسی عمران( ICCE )، تهران، اردیبهشت 22-24.
Asgharzadeh, H., Firoozabadi, B. and Afshin, H., 2012. Experimental and numerical simulation of the effect of particles on flow structures in secondary sedimentation tanks. Journal of Applied Fluid Mechanics, 5(2), pp.15-23.
Celik, I., Rodi, W. and Stamou, A.I., 1985. Prediction of hydrodynamic characteristics of rectangular settling tanks. International Symposium of Refined Flow Modeling and Turbulence Measurements.
Ekama, G.A. and Marais, P., 2004. Assessing the applicability of the 1D flux theory to full-scale secondary settling tank design with a 2D hydrodynamic model. Water research, 38(3), pp.495-506.
Gharagozian, A., 1998. Circular secondary clarifier investigations using a numerical model, Doctoral dissertation, University of California, Los Angeles.
Goula, A.M., Kostoglou, M., Karapantsios, T.D. and Zouboulis, A.I., 2008. A CFD methodology for the design of sedimentation tanks in potable water treatment: Case study: The influence of a feed flow control baffle. Chemical Engineering Journal, 140(1), pp.110-121.
Hirt, C.W. and Nichols, B., 1988. Flow-3D User’s Manual. Flow Science Inc.
Imam, E. and McCorquodale, J.A., 1983. Simulation of flow in rectangular clarifiers. Journal of Environmental Engineering, 109(3), pp.713-730.
Krebs, P., Vischer, D. and Gujer, W., 1995. Inlet-structure design for final clarifiers. Journal of Environmental Engineering, 121(8), pp.558-564.
Mazzolani, G., Pirozzi, F. and d’Antonoi, G., 1998. A generalized settling approach in the numerical modeling of sedimentation tanks. Water Science and Technology, 38(3), pp.95-102.
McCorquodale, J.A., Moursi, A.M. and El-Sebakhy, I.S., 1988. Experimental study of flow in settling tanks. Journal of Environmental Engineering, 114(5), pp.1160-1174.
Mccorquodale, J.A. and Zhou, S., 1993. Effects of hydraulic and solids loading on clarifier performance. Journal of Hydraulic Research, 31(4), pp.461-478.
Naser, G., Karney, B.W. and Salehi, A.A., 2005. Two-dimensional simulation model of sediment removal and flow in rectangular sedimentation basin. Journal of Environmental Engineering, 131(12), pp.1740-1749.
Razmi, A.M., Bakhtyar, R., Firoozabadi, B. and Barry, D.A., 2013. Experimental and numerical modeling of baffle configuration effects on the performance of sedimentation tanks. Canadian Journal of Civil Engineering, 40(2), pp.140-150.
Razmi, A., Firoozabadi, B. and Ahmadi, G., 2009. Experimental and numerical approach to enlargement of performance of primary settling tanks. Journal of Applied Fluid Mechanics, 2(1).
Shahrokhi, M., Rostami, F., Said, M.A.M., Sabbagh-Yazdi, S.R., Syafalni, S. and Abdullah, R., 2012. The effect of baffle angle on primary sedimentation tank efficiency. Canadian Journal of Civil Engineering, 39(3), pp.293-303.
Stamou, A.I., 2008. Improving the hydraulic efficiency of water process tanks using CFD models. Chemical Engineering and Processing: Process Intensification, 47(8), pp.1179-1189.
Taebi-Harandy, A. and Schroeder, E.D., 2000. Formation of density currents in secondary clarifier. Water Research, 34(4), pp.1225-1232.
Tamayol, A. and Firoozabadi, B., 2006. Effects of turbulent models and baffle position on hydrodynamics of settling tanks. Scientia Iranica J, 13(3), pp.255-260.
Tamayol, A., Firoozabadi, B. and Ahmadi, G., 2008. Effects of inlet position and baffle configuration on hydraulic performance of primary settling tanks. Journal of Hydraulic Engineering, 134(7), pp.1004-1009.
Tarpagkou, R. and Pantokratoras, A., 2014. The influence of lamellar settler in sedimentation tanks for potable water treatment—a computational fluid dynamic study. Powder Technology, 268, pp.139-149.
Zhou, S. and McCorquodale, J.A., 1992. Modeling of rectangular settling tanks. Journal of Hydraulic Engineering, 118(10), pp.1391-1405.