Study on the influence of suspension layer on treatment effect of vertical flow sedimentation

Abstract

Vertical flow sedimentation relies on natural sedimentation of flocs and hindered sedimentation of the suspension layer to achieve solid-liquid separation. Moderate flocculation could completely leverage the synergistic effect, reduce the dosage while also improve the sedimentation effect. For the purpose of clarifying the significance of the suspension layer, this paper conducted a continuous vertical flow sedimentation experiment to observe and test the changes in the morphology of flocs, suspension layer state, and sedimentation effect under different operating conditions. The analysis was focused on three typical operating conditions: mild flocculation, moderate flocculation, and heavy flocculation. The results suggested that the natural settling efficiency of flocs and suspension interception effect under mild flocculation were inferior. Although the natural settling effect of heavy flocculation was outstanding, the interception effect in the suspension layer was not satisfied. Only moderate flocculation could effectively balance the synergistic effect of natural sedimentation and suspension layer interception, with the best sedimentation effect, corresponding to a floc fractal dimension of 1.83, density of 1.391 g/cm3 and suspension layer height of 2.2 m.

Keywords

• vertical flow sedimentation
• suspension layer
• hindered sedimentation
• fractal dimension