Changes in particle size distributions in batch flocculation

Batch flocculation experiments were performed to test a previously developed model for the changes in particle size distribution. Within each experiment, time was the only independent variable; between experiments, the velocity gradient, particle concentration, and chemical conditions were varied independently. Detailed measurements of the particle size distribution were made, and the extent of change caused by each variable was quantified. The effect of time, concentration, and chemical conditions were reasonably well explained if partial sedimentation was allowed in the model. The effect of the velocity gradient was greatly overestimated by the model, suggesting that current understanding of particle collisions caused by fluid motion is weak.