Chairoj Rattanakawin

pp. 1095 - 1101

Abstract

The evolution of aggregate size distributions resulting from sweep flocculation has been investigated
using laser light scattering technique. By measuring the (volume) distributions of floc size, it is possible to
distinguish clearly among floc formation, growth and breakage. Sweep flocculation of stable kaolin suspensions with ferric chloride under conditions of the rapid/slow mixing protocol produces uni-modal size distributions. The size distribution is shifted to larger floc size especially during the rapid mixing step. The
variation of the distributions is also shown in the plot of cumulative percent finer against floc size. From this
plot, the distributions maintain the same S-shape curves over the range of the mixing intensities/times studied.
A parallel shift of the curves indicates that self-preserving size distribution occurred in this flocculation. It is
suggested that some parameters from mathematical functions derived from the curves could be used to
construct a model and predict the flocculating performance. These parameters will be useful for a water
treatment process selection, design criteria, and process control strategies. Thus the use of these parameters
should be employed in any further study.

Keywords

• aggregate size distribution
• S-shape curve
• self-preserving size distribution
• sweep flocculation