ABSTRACT
Not all suspended particles will be removed in this process, even under very long detention times. Buoyancy and drag (friction) affect the settling rate, as do water temperature and viscosity. Very small particles (including colloids, bacteria, color particles, and turbidity) will not settle out of suspension without some help. The coagulation process provides that help. By rapidly mixing coagulant chemicals with the water, then slowly and gently stirring the mixture before sedimentation, these particles form žoc in the ¡occulation process. The larger, heavier žoc particles settle, and can then be removed by subsequent settling and ›ltration. In fact, colloidal particles must be chemically coagulated to be removed (see Figure 5.2).
