In a clarifier, where does floc settle?

Floc settles in the sludge zone of a clarifier due to gravity. The design of a clarifier promotes the separation of solids from the liquid by allowing the larger aggregated particles, known as flocs, to migrate downwards through the water column. This downward movement is primarily influenced by the density of the floc, which is greater than that of the water, allowing it to settle at the bottom of the clarifier.

In the sludge zone, the settled solids accumulate and form a sludge layer. This sludge can then be removed periodically to maintain the efficiency of the clarifier. The characteristics of the sludge zone, such as pressure and the presence of accumulated solids, foster the ongoing settling process.

The other zones mentioned play different roles in the clarifier system. The scum zone is where lighter materials and oils accumulate on the surface, the flow zone refers to the area where water is actively moving and being treated, and the filtration zone is typically where finer particles may be removed, often in the subsequent processes after clarification. Therefore, the sludge zone is uniquely relevant for the settling and accumulation of floc.