Dissolved Air Flotation

Dissolved Air Flotation (DAF) is another form of clarification process that relies on flotation of floc particles to the surface instead of gravity sedimentation. It is suited to particular quality raw water streams – generally low turbidity, coloured waters which would otherwise be more difficult to treat by sedimentation. The DAF process is also particularly suited to the treatment of nutrient-rich reservoir waters that may contain heavy algal blooms.

The DAF process may also be combined with the gravity filter process in the same structure for saving in plant cost and footprint requirement (termed Dissolved Air Flotation-Filtration, or DAFF).

In this process, air bubbles are introduced to the flocculated water, where they attach to the floc particles and then float to the surface. The resultant "float" is accumulated on the water surface and then periodically discharged as a concentrated waste stream.