chapter  11
38 Pages

Flocculation

In water treatment, the starting point is the rapid mix where ‘‘microflocs’’ form from coagulation chemicals and which may incorporate ‘‘primary’’ particles, e.g., mineral turbidity, microorganisms, and other ‘‘microscopic particulates.’’ The next step is flocculation; the objective is to cause collisions such that the microflocs grow in size to become ‘‘floc’’ particles. If the treatment train is conventional filtration, the flocculation objective is to produce large settleable flocs. In flotation, on the other hand, the objective is to form a floc of small size, e.g., 50 mm, that rises readily when small gas bubbles attach.