Dissolved Air Flotation (DAF) is a unit process used to separate
solid particles or dissimilar liquid droplets from a liquid
phase. Separation is brought about by introducing fine gas (in
this case air) bubbles into the liquid phase. The bubbles become
attached to the particles and the buoyant force of the attached
air bubbles is great enough to cause the particle to rise to the
surface. Particles that have a higher density than a liquid can
be made to rise. The flotation of lower density particles can
also be facilitated (such as oily wastes). Once on the surface
the particles are collected by a skimming operation.In
SAMCO's DAF equipment air is dissolved under pressure and is
then released into the unit. The flow is held in a tank under
pressure for several minutes to allow for the air to dissolve.
The flow is then admitted to the flotation tank through a
pressure reducing valve. The air is released in the main tank
and the material of concern is floated. A portion of the
effluent is often recycled to enhance the overall process.
DAF efficiency can be greatly enhanced through pre-treatment.
SAMCO reactor and flash floc systems are often used for this
purpose.
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