Description

Sedimentation is a process used widely in the clarification of water and waste water. Particles settle from suspension in different ways, depending on the concentration of the suspension and the characteristics of the particles.

The simplest type of sedimentation is the settling of a dilute suspension of particles that have little or no tendency to flocculate. In these circumstances, the prediction of clarification rates and their scaleup to plant design is relatively straightforward.

For higher concentrations where inter-particle effects become significant and where agglomeration may take place, different regimes of settling rate occur, known as ‘zone’ settling (fig 1).

Information from batch tests for such systems forms a vital part of the search for the optimum design and operation of industrial sedimentation tanks.

fig2 Sedimentation curves from sample data