4. Settling

Once the floc has formed, solid-liquid separation is carried out to obtain clarified water on one side and sludge (initial colloidal particles + floc) on the other. The action of gravity on suspended particles is generally used, and the clear water is then collected in the upper part of the unit, while the sedimented sludge is drawn off in the lower part: this is the decantation process. or [9] . In certain special cases, where the floc is light, flotation can be carried out 5