Alum Residual Floc Interactions with an Advancing Ice/Water Interface
Publication: Journal of Environmental Engineering
Volume 124, Issue 3
Abstract
Freezing and thawing transform alum sludge flocs into granular particles that rapidly settle. One objective of this paper is to help modelers and designers of the freeze/thaw conditioning process visualize the process at a microscopic scale. A second objective is to report a phenomenon occurring at the ice/water interface, namely, the fragmentation of flocs by the advancing freezing front. To meet these objectives, directional freezing of alum sludge was observed using a microscope at 40× power. A Bridgman growth apparatus was designed to allow various rates of directional freezing to be observed. The interface interacted with the flocs in various ways, depending on the freezing rate. At high freezing rates, dendrites either pierced the flocs or bypassed them, effectively confining the flocs and fragmenting them. At low rates, the interface was smooth and planar. Rather than being incorporated in the ice, flocs were rejected by the planar interface. At intermediate freezing rates, the interface was rough, and flocs were fragmented as they were rejected. The fragmentation of the flocs helps explain why some researchers have noted a decrease in floc size following freeze/thaw conditioning.
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References
1.
Asthana, R., and Tewari, S. N.(1993). “Review: the engulfment of foreign particles by a freezing interface.”J. Mat. Sci., 28(20), 5414–5425.
2.
Beckmann, J., Korber, C., Rau, G., Hubel, A., and Cravalho, E. G.(1990). “Redefining cooling rate in terms of ice front velocity and thermal gradient: first evidence of relevance to freezing injury of lymphocytes.”Cryobiology, 27(3), 279–287.
3.
Brown, G. N. (1993). “Proof-of-concept pilot study for mechanical freeze/thaw conditioning of water treatment residuals.”Clean Water Solutions Conf., Charlotte, N.C.
4.
Dempsey, B. A., DeWolfe, J., Lunetta, M., and Elias, S. (1995). “Freeze/thaw dewatering of water treatment residuals—chemical effects.”Joint Residuals Mgmt. Conf., Water Environment Federation, Alexandria, Va., and American Water Works Association, Denver, Colo.
5.
Hung, W. T., Chang, I. L., Lin, W. W., and Lee, D. J.(1996). “Unidirectional freezing of waste-activated sludges: effects of freezing speed.”Envir. Sci. and Technol., 30(7), 2391–2396.
6.
Kawasaki, K., Matsuda, A., and Mizukawa, Y.(1991). “Compression characteristics of excess activated sludges treated by freezing-and-thawing process.”J. Chemical Engrg. of Japan, 24(6), 743–748.
7.
Knocke, W. R., and Trahern, P.(1989). “Freeze-thaw conditioning of chemical and biological sludges.”Water Res., 23(1), 35–42.
8.
Lee, D. J., and Hsu, Y. H.(1994). “Fast freeze/thaw treatment on excess activated sludges: floc structure and sludge dewaterability.”Envir. Sci. and Technol., 28(8), 1444–1449.
9.
Lipp, G., and Körber, C.(1993). “On the engulfment of spherical particles by a moving ice-liquid interface.”J. Crystal Growth, 130(314), 475–489.
10.
Logsdon, G. S., and Edgerley, E.(1971). “Sludge dewatering by freezing.”J. AWWA, 63(11), 734–740.
11.
Matsuda, A., Kawasaki, K., and Mizukawa, Y.(1992). “Measurement of bound water in excess activated sludges and effect of freezing and thawing process on it.”J. Chemical Engrg. of Japan, 25(1), 100–103.
12.
Parker, P. J., Collins, A. G., and Dempsey, J. P. (1996). “Incorporation and rejection of alum sludge flocs by an advancing freezing front.”Proc., 8th Int. Conf. on Cold Regions Engrg., ASCE, 757–767.
13.
Vesilind, P. A.(1994). “The role of water in sludge dewatering.”Water Envir. Res., 66(1), 4–11.
14.
Vesilind, P. A., and Martel, C. J.(1990). “Freezing of water and wastewater sludges.”J. Envir. Engrg., ASCE, 116(5), 854–862.
15.
Vol'khin, V. V., and Zolotavin, V. L.(1961). “The effect of freezing on the properties of metal hydroxide coagulates. Part 2: Effect of electrolytes on changes of the volume of ferric hydroxide coagulate as a result of freezing.”Colloid J. USSR, Moscow, Russia, 23(2), 113–117.
16.
Vol'khin, V. V., and Ponomarev, E. I.(1965). “Effect of freezing on the properties of coagulated metal hydroxides. 5: Mechanism of the process.”Colloid J. USSR, Moscow, Russia, 27(1), 10–13.
17.
Vol'khin, V. V., Zolotavin, V. L., and Tipikin, S. A.(1961). “The effect of freezing on the properties of metal hydroxide coagulates. Part 4: Manganese dioxide coagulate.”Colloid J. USSR, Moscow, Russia, 23(4), 339–341.
18.
Zolotavin, V. L., and Vol'khin, V. V.(1961). “The effect of freezing on the properties of metal hydroxide coagulates. 3: The effect of electrolytes on the change in particle size of iron hydroxide and on the rate of filtration.”Colloid J. USSR, Moscow, Russia, 23(3), 276–280.
19.
Zolotavin, V. L., Vol'khin, V. V., and Rezvushkin, V. V.(1960). “Effect of freezing on the properties of coagulated metal hydroxides of coagulated ferric hydroxide. Part 1: Influence of freezing and thawing conditions on the properties of coagulated ferric hydroxide.”Colloid J. USSR, Moscow, Russia, 22(3), 317–324.
Information & Authors
Information
Published In
Journal of Environmental Engineering
Volume 124 • Issue 3 • March 1998
Pages: 249 - 253
Copyright
Copyright © 1998 American Society of Civil Engineers.
History
Published online: Mar 1, 1998
Published in print: Mar 1998
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