Fluid shear influences on flocculation Fluid shear influences on flocculation

The tube flocculator is used to study how fluid shear levels affect the settling properties of a flocculated alum-kaolin suspension. FReTA is employed to quantitatively compare the effects of varying fluid shear and hydraulic residence time on the sedimentation velocity distributions and the post-sedimentation residual turbidities of flocculated suspensions formed in the tube flocculator. Results from experiments showed that shear induced floc break up occurred at all velocity gradients evaluated. There is a correlation between high floc settling velocities and low residual turbidities, both of which were optimized at low fluid shear levels and long fluid residence times. This study shows that, for hydraulic flocculation systems, low turbidity water is produced when fluid shear is kept at a minimum.