CLARIFLOCCULATION

In the Sedimentation with flocculation the particles do not keep their individuality, but tend to agglomerate helped by some coagulants. The sludge floc size increases and, as a consequence, the sedimentation speed increases too.

SEDIMENTATION WITH FLOCCULATION
A complete process of clarification mainly consists of three subsequent stages:
1) Mixing of the inflow (waste water) with the reagents 2)Flocculation 3) Sedimentation
The waste water mixing with the reagents must be made very quickly and with a strong stirring. On the contrary, the flocculation must be slow in order to allow the flocs agglomeration and any turbulent motion must be avoided.The clarified water is then collected in the upper part through circular or radial ditches, the sludge sediments on the tank bottom and is conveyed into a drain well by some scrapers.

CLARIFLOCCULATOR WITH SLUDGE RECYCLE The clariflocculator with sludge recycle is equipped with a turbine to recycle and mix the already settled sludge with the new water to be treated which has already been conditioned with reagents. The “old” sludge flocs, usually of medium-large size, help the production of new sludge flocs. The conditioned water, when entering the clariflocculator, is mixed with the settled sludge in the reaction chamber as it is lifted by a radial-axial flow turbine.
It is fundamental that this operation occurs at the minimum speed as possible for not breaking the sludge flocs. The sludge recycle flow rate is variable and is adjusted by means of a variable-speed geared motor. The lifted sludge and the water to be treated, after having been mixed in the reaction zone, are conveyed to the flocculation zone where the flocs gather and become larger and the settling phase begins. The clarified water can be collected through radial or peripheral ditches. The radial ditches are more efficient because the water flow towards them is more homogeneous and the flow speed does not become too fast in certain zones.
According to the already mentioned Stokes’ law, the settling speed is higher for larger suspended solids.