Hydrodynamic conditioning of aluminium-bentonite flocs

The aim of this paper is to analyse the role of hydrodynamics in flocculation. The effects of a hydrodynamic sequencing (flocculation-break-upreflocculation-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.