Flotation

Flotation is the separation of suspended solids from a liquid. The finest air bubbles that are produced attach themselves to the solids and carry them to the water surface. Because of its high separation efficiency and extensive concentration, the flotation process has many advantages over sedimentation.

Range of applications

The use of flotation is especially advantageous if the sewage contains solids, which have poor sedimentation properties. To achieve separation of the waste water also of dissolved substances, it is also necessary to effect flocculation, or destabilization, by adding suitable chemicals. Generally the following applies: The smaller and more hydrophilic the particles are, the smaller the air bubbles must be. The effectiveness of the flotation essentially depends on the size of the air bubbles and their finest distribution in the water.

Excellent effect

Through a long series of experiments it was possible to achieve an extremely uniform and fine distribution of air in the water and waste water, to which the excellent effect of STULZ-PLANAQUA flotation can be attributed.

Technical details

The waste water is supplied to the flocculation chamber from a buffer tank. Depending on the composition of the waste water, the addition of different chemicals and with the aid of agitators their intensive mixing with the waste water before it can even get into the free intake in the inlet chamber of the flotation itself. In this area, the so-called dispersion stream is fed in, with reference to all special conditions.

Flotation cakes

The small air bubbles that form at the relaxation of the dispersion stream saturated with air settle on the waste water substances and carry them to the surface in the flotation chamber. The flotation cakes that form are removed from the surface of the water into the sludge collection container by means of a clearing device. Depending on requirements, the flotate can then be fed for further treatment.

Dispersion stream treatment

The effluent, solid-clear water flows through an adjustable weir into the discharge chamber. A partial stream of treated water is supplied from the discharge chamber via a pump and a pressure container under pressure of 5 bar saturated with air. The dispersion stream thus produced – its share is, depending on the waste water composition, 25% to 200% of the untreated water supply – is then fed into the inlet chamber and relaxed, whereby the air is released in the form of the finest air bubbles and performs its intended task.