Charge Reversal Effect on Blanket in Full-Scale Floc Blanket Clarifier
Publication: Journal of Environmental Engineering
Volume 132, Issue 11
Abstract
Operators at waterworks in which flat-bottom floc blanket clarifiers are used, are advised to increase coagulant dose when the turbidity of clarified water is high, to stabilize the blanket and yield quality drinking water. This work showed that, even when the raw water is sufficiently alkaline, the blanket responded anomalously to the increased dose of polyaluminum chloride (PACl), which was used herein as a coagulant. Restated, rather than being stabilized, the blanket was destabilized by the high dose of PACl. This “anomalous” behavior of the blanket is caused by a temporary drop in local pH at the injection port at the bottom of the blanket, which is caused by poor PACl dispersion, and the subsequent charge reversal of the constituent particles and the decline in the blanket stability. A step increase in PACl dose may result in complete blanket loss.
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Acknowledgments
National Science Council, Taiwan financially supported this work.NSCT
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Information
Published In
Journal of Environmental Engineering
Volume 132 • Issue 11 • November 2006
Pages: 1523 - 1526
Copyright
© 2006 ASCE.
History
Received: Apr 4, 2005
Accepted: Apr 13, 2006
Published online: Nov 1, 2006
Published in print: Nov 2006
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