Prediction of Reaeration Rates in Square, Stirred Tanks
Publication: Journal of Environmental Engineering
Volume 125, Issue 3
Abstract
Experiments were conducted on the oxygen transfer coefficient, kLa20, through surface aeration in geometrically similar square tanks, with a rotor of diameter D fitted with six flat blades. An optimal geometric similarity of various linear dimensions, which produced maximum kLa20 for any rotational speed of rotor N by an earlier study, was maintained. A simulation equation uniquely correlating k = kLa20(ν/g2)1/3 (ν and g are kinematic viscosity of water and gravitational constant, respectively), and a parameter governing the theoretical power per unit volume, X = N3D2/(g4/3ν1/3), is developed. Such a simulation equation can be used to predict maximum k for any N in any size of such geometrically similar square tanks. An example illustrating the application of results is presented. Also, it has been established that neither the Reynolds criterion nor the Froude criterion is singularly valid to simulate either k or K = kLa20/N, simultaneously in all the sizes of tanks, even through they are geometrically similar. Occurrence of “scale effects” due to the Reynolds and the Froude laws of similitude on both k and K are also evaluated.
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References
1.
Banks, R. B., Sally, L. R., and Polprasert, C. (1983). “Mechanical mixing and surface reaeration.”J. Envir. Engrg., ASCE, 109(1), 232–241.
2.
Cleasby, J. L., and Baumann, R. B. ( 1968). “Oxygenation efficiency of bladed rotor.” J. Water Pollution Control Fed., 40(3), Part 1, 412–424.
3.
Connolly, J. R., and Winter, R. L. ( 1969). “Approaches to mixing operation and scale-up.” Chemical Engrg. Progress, 65(8), 70–78.
4.
Eckenfelder, Jr. ( 1956). “Process design of aeration system for biological waste treatment.” Chemical Engrg. Progress, 52(7), 286–292.
5.
Eckenfelder, Jr., and O'Conner. ( 1961). “Biological waste treatment.” Pergamon, Tarrytown, N.Y.
6.
Horvath, I. ( 1984). “Modelling in the technology of wastewater treatment.” Pergamon, Tarrytown, N.Y.
7.
“Indian standards.” (1964). No. I.S.3025, 94–95.
8.
Lewis, W. W., and Whiteman, W. G. ( 1924). “Principles of gas absorption,” Industrial and Engrg. Chemistry, 16(2), 1215–1220.
9.
Maise, G. (1970). “Scaling methods for surface aerators.”J. Sanitary Engrg. Div., ASCE, 96(5), 1079–1083.
10.
Manual of practice for water pollution control . (1988). “Aeration a waste water treatment process.” Water Environment Federation, Alexandria, Va., and ASCE, New York.
11.
Metcalf & Eddy Inc. ( 1979). “Waste water engineering: Treatment disposal and reuse.” Tata McGraw-Hill, New Delhi.
12.
Ramakrishna Rao, A., and Laxmi, U. S. ( 1996). “Optimal geometric cross-sectional shape of surface aeration tank for maximum oxygen transfer.” Proc., North Am. Water and Envir. Congr.—'96, Orange County Branch, Los Angeles Section, ASCE, New York.
13.
Schmidtke, N. W., and Horvath, T. ( 1976). “Scale-up methodology for surface aerated reactors.” Progress Water Technol., 9.
14.
Smith, J. M. ( 1979). “Physical aspects of water aeration.” Progress Water Technol., 11(3), 1–8.
15.
“Standard methods for the examination of water and waste water.” (1985). 16th Ed., American Public Health Association, AWWA, WPCA, Washington, D.C.
16.
Udaya Simha, L. ( 1991). “Experimental studies on overall oxygen transfer coefficient,” PhD thesis, Dept. of Civ. Engrg., Indian Institute of Science, Bangalore, India, 187.
17.
Udaya Simha, L., Sarma, K. V. N., and Ramakrishna Rao, A. ( 1991). “Effect of geometric parameters on overall oxygen transfer coefficient.” Proc., Symp. on Envir. Hydr.
18.
Valentin, F. H. N. ( 1967). Absorption in gas liquid dispersion . E & FN Spon, London.
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Received: Feb 23, 1998
Published online: Mar 1, 1999
Published in print: Mar 1999
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