ABSTRACT
The objective of flocculation, as a unit process in water treatment, is to cause collisions between small particles. After colliding, the premise is that the particles will stick to each other and thus agglomerate, growing to some desired size and becoming a floc (thus fulfilling the process goal). The process of agglomeration is called flocculation. (Note that the term coagulation refers to the creation of microflocs through charge neutralization of negatively charged microscopic particles, and that flocculation is the agglomeration of microflocs to flocs. Flocculation is not restricted to the agglomeration of chemical microflocs; bacteria may agglomerate also, as in settling of activated sludge.)
In principle, flocculation is a special case of mixing (as in Chapter 10). At the risk of some redundancy, flocculation is considered here as a separate topic in order to impute to it its own identity. This was motivated, in part, by the need to distinguish between coagulation and flocculation (which are sometimes not distinguished in the literature) and, in part, by the fact that in practice flocculation is considered a distinct unit process.
