Study of the Effect of Linear and Parabolic Density Region in Settling Tanks for Potable Water
Publication: Journal of Environmental Engineering
Volume 141, Issue 11
Abstract
Computational fluid dynamics (CFD) methods are employed to evaluate the influence of temperature variations on the flow field in an actual sedimentation tank for potable-water treatment. A series of experimental measurements of temperature variation has been conducted in that sedimentation tank. The mixed-convection problem caused by the density variations and the horizontal stream is considered at low temperatures (0–10°C) where the variation of water density is strongly nonlinear. Three cases have been examined: (1) one in the ascending, (2) one in the descending parabolic density region, and (3) one in the linear density region. The thermophysical properties of water have been incorporated into the CFD code. All simulations have been conducted for a transient, turbulent flow field. The momentum exchange between the primary and the secondary phase (particles) is considered. The results show that in the parabolic density region, only a few particles are trapped in the bottom, whereas many of them float near the surface and escape from the tank causing a low-tank efficiency. The opposite happens in the linear-density region where the tank efficiency is much better.
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Acknowledgments
The financial support provided by Thessaloniki Water Supply and Sewerage Company is gratefully acknowledged. The authors would like to thank K. Zampetoglou, G. Seretoudi, A. Soupila, A. Papaionannou, and E. Samara for their contribution.
References
ANSYS FLUENT 15.0 [Computer software]. Canonsburg, PA, ANSYS.
Caldewell, D. (1985). “Separation of seawater by Soret diffusion.” Deep-Sea Res., 32(8), 965–982.
Fofonoff, N. P. (1985). “Physical properties of seawater: A new salinity scale and equation of state for seawater.” J. Geophys. Res., 90(C2), 3332–3342.
Fofonoff, N. P., and Millard, R. C. (1983). “Algorithms for computation of fundamental properties of sea water.”, Division of Marine Sciences, Paris, France.
Hinze, J. O. (1975). Turbulence, Mc Graw-Hill, New York.
Kawamura, S. (1991). Integrated design of water treatment facilities, Wiley, New York.
Larsen, P. (1977). “On the hydraulics of rectangular settling basins.”, Dept. of Water Research Engineering, Lund Institute of Technology, Lund, Sweden.
Liu, B., Ma, J., Luo, L., Bai, Y., Wang, S., and Zhang, J. (2010). “Two-dimensional LDV measurement, modeling, and optimal design of rectangular primary settling tanks.” J. Environ. Eng., 501–507.
Matthaus, W. (1970). Monatsber. Dtsch. Akad. Wiss. 12 (11-12) Berlin, 850 (in German).
Pantokratoras, A. (2003). “Vertical penetration of double-diffusive water plumes discharged vertically downwards.” J. Hydraul. Eng., 541–545.
Tarpagkou, R., and Pantokratoras, A. (2013). “CFD methodology for sedimentation tanks: The effect of secondary phase on fluid phase using DPM coupled calculations.” Appl. Math. Modell., 37(5), 3478–3494.
Turcotte, B., Morse, B., Bergeron, N. E., and Roy, A. G. (2011). “Sediment transport in ice-affected rivers.” J. Hydrol., 409(1–2), 561–577.
Wang, X., Yang, L., Sun, Y., Song, L., Zhang, M., and Cao, Y. (2008). “Three-dimensional simulation on the water flow field and suspended solids concentration in the rectangular sedimentation tank.” J. Environ. Eng., 902–911.
Wells, S. A., and LaLiberte, D. M. (2008). “Winter temperature gradients in circular clarifiers.” Water Environ. Res., 70(7), 1274–1279.
Xiao, F., Ma, J., Yi, P., and Huang, J. C. (2008). “Effects of low temperature on coagulation of kaolinite suspensions.” Water Res., 42(12), 2983–2992.
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Published In
Journal of Environmental Engineering
Volume 141 • Issue 11 • November 2015
Copyright
© 2015 American Society of Civil Engineers.
History
Received: Apr 5, 2013
Accepted: Mar 10, 2015
Published online: Jun 2, 2015
Published in print: Nov 1, 2015
Discussion open until: Nov 2, 2015
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