Flotationprocesses are used to separate solids from a liquid. The flotation process mostcommonly used in water treatment is dissolved air flotation. The suspension tobe treated is placed in a tank. Flocculation chemicals can be added to the rawwater in order to improve the flotation of the contaminants. The diatomiteprovided is suitable as a contaminant. A pump transports the raw water, whichenters the flotation column via a vertical pipe. The height of the supply linecan be adjusted. A water circuit with pump is connected to the flotationcolumn. Two compressors supply air to the water circuit on the suction side ofthe pump. The air dissolves in the water under pressure. Part of the waterflows back to the pump via a bypass. The other part of the water enters apressure vessel filled with Pall rings. The pressure vessel ensures asufficiently long dwell time to dissolve the air and to separate undissolvedair.
The water then enters the flotation column from below via a valve. This causesa sudden drop in pressure to almost atmospheric pressure. Since the solubilityof air increases with increasing pressure, the excess air forms small bubbles.The air bubbles accumulate on the contaminants. The contaminants rise up in thecolumn together with the air bubbles. At the upper end of the flotation column,the contaminants enter a circulating channel.