Using CFD in the Study of Mixing in Coagulation and Flocculation
Mixing has always been acknowledged to be one of the key issues in producing a good quality treated water in the chemical water treatment process. In the rapid mixing stage, where the inorganic coagulant is first mixed into the raw water, the charge neutralization step occurs in less than a second. This being the case, charge neutralization and adsorption are very mixing-sensitive processes. A lack of effective mixing when using inorganic coagulants results in chemical overdosing and decreased efficiency as sweep coagulation becomes the dominant mechanism for floe formation. On the other hand, in the flocculation stage excess velocity gradients should be avoided in designing a flocculator. This work highlights the possible use of computational fluid dynamics, CFD, in numerical modeling of mixing in water treatment processes.
KeywordsComputational Fluid Dynamic Particle Image Velocimetry Turbulence Kinetic Energy Eddy Viscosity Drinking Water Treatment Plant
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- 1.CFX-4.2: Solver, AEA Technology pic, 1997Google Scholar
- 2.Launder, B.E., Spalding, D.B.: Lectures in Mathematical Models of Turbulence. Academic Press, London, England (1972)Google Scholar
- 3.Camp, T.R., P.C. Stein: Velocity Gradients and Internal Work in Fluid Motion. Jour. Boston Soc. Civil Engrg. 30 (10) (1943) 217Google Scholar
- 4.Luo, C.: Distribution of Velocities and Velocity Gradients in Mixing and Flocculation vessels: Comparison between LDV data and CFD prediction. Ann Arbor, Mich. UMI Dissertation Services (1997)Google Scholar
- 5.Korpijärvi, J., Ahlstedt, H., Saarenrinne, P., Reunanen, J.: Modelling of flow field in the Mini-flocculator. In: Fluid Mixing 6, H. Benkreira (Ed) IChemE 146, UK, (1999) 361–372Google Scholar
- 6.Amirtharajah A., Tambo, N.: Mixing in Water Treatment. In: Mixing in Coagulation and Flocculation, Amirtharajah A., Clark, M.M., Trussel, R.R. (Eds) American Water Works Research Foundation (1990) 3 - 34Google Scholar