ABSTRACT
Gravity settling is a commonly used process for separating insoluble particles of solids or liquids from a liquid or gaseous carrier fluid. It uses as a driving force for separation the effect of gravity on the difference in density between the dispersed particles and the carrier fluid in which the particles are dispersed. If the particles are denser than the carrier fluid, they sink to the bottom of the settling chamber. If they are less dense, they rise to the surface of a liquid carrier. Gravity settling is a subcategory of the more general field of sedimentation, which includes the slower processes of hindered settling, flocculation, coagulation, clarification, and thickening. These latter processes are discussed in Chapter 8 along with chemical precipitation. Furthermore, the enhancement of gravity separation by the use of centrifuges and cyclones is discussed in Chapter 7. The present chapter discusses only the relatively simple separations by gravity used for removal of suspended particles from wastewaters and separation of dusts and mists from gas streams. These are free-settling cases for dilute suspensions where the particles do not interfere with each other during settling.
