The deformation of restrained flocs has been studied in a vertically-oriented flow chamber in an effort to quantify the response of aggregate structures exposed to hydrodynamic stress. These results have been used in turn as part of the analysis of an expulsion process occurring when large kaolin-polymer flocs are discharged from a micropipette tip under the influence of increasing upstream pressure. The deformation experiments complement breakage trials in which changes in the floc size distribution were monitored in a stirred, baffled tank. By measuring the power input (mean dissipation rate) and the average size of fragments produced by an increase in stirring rate, it is possible to estimate the strength with which fragments were bound to the parent structure. These data show that the ratio of fragment size to mean floc size decreases as the power input increases; they also show fragment size decreases (with stirring rate) much more sharply than the Kolmogorov microscale. This study has provided quantitative data regarding both floc deformation and breakage that can be used for the improved design and operation of flocculation processes. References: 17
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