Water Supply Vol 6 No 1 pp 11–19 © IWA Publishing 2006
Hydrodynamic conditioning of aluminium-bentonite flocs
C. Coufort* and A. Liné**
*Laboratoire d'Ingénierie des Procédés de l'Environnement, INSA Toulouse, 135 Avenue de Rangueil 31077 Toulouse, Cedex 4 France, (E-mail: carole.coufort@insa-toulouse.fr; alain.line@insa-toulouse.fr
**Laboratoire d'Ingénierie des Procédés de l'Environnement, INSA Toulouse, 135 Avenue de Rangueil 31077 Toulouse, Cedex 4 France, (E-mail: carole.coufort@insa-toulouse.fr; alain.line@insa-toulouse.fr
ABSTRACT
The aim of this paper is to analyse the role of hydrodynamics in flocculation. The effects of a hydrodynamic sequencing (flocculation-break-up-reflocculation-break-up-reflocculation) on the evolution of aluminium-bentonite floc size distributions and structure are investigated by image analysis in a Taylor-Couette reactor. The flocculation phenomena analysed in this study mainly occur in the viscous subrange, with floc size below the Kolmogorov micro-scale. The high sensitivity of steady-state floc size distribution to initial floc size distribution (elementary particles or flocs formed issuing break-up stages) is highlighted. Reversibility or irreversibility of agglomeration and break-up phenomena are discussed in terms of floc history and hydrodynamic stress. Finally, the hydrodynamic conditioning for aluminium-bentonite flocs is examined.
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