Dissolved Air Flotation – Applications and Limitations in Wastewater Treatment

Dissolved Air Flotation is widely used in Wastewater Treatment as well as in less traditional applications such as:

•   drinking water clarification and color removal
•   Algae removal
•   By-product recovery  (i.e. metals, etc.)
•   Dissimilar solids separation

Within Wastewater Treatment, DAF application can be divided into
•   Primary Treatment
•   Secondary Treatment
•   Tertiary Treatment

In all cases, DAF (dissolved air flotation) is used to separate fine solids (any constituents that are not dissolved) by flotation, assisted by the attachment of microscopic bubbles.  Often, solids that would normally settle are forced to the surface for removal through the attachment of those fine bubbles.

DAF is used in a wide range of situations where the suspended material  can be as little as 20 mg/l (as in algae or color removal) to tens of thousands of mg/l as in rendering or some petro-chemical oil/water separation situations.  Each case must be evaluated for size, flow, and chemical requirements.

To further complicate the issue, the general term, DAF, no longer covers all the approaches to separating solids with microscopic bubbles.  Other similar technologies that are frequently referred to as DAF are:

•   CAF (cavitation air flotation)
-Bubbles produced by a spinning disk without pressure
•   BAF (bubble air flotation)
-Bubbles produced by blowing air through a micro-filter into the water
•   SAF (saponification air flotation)
-Bubbles produced with the aid of a surfactant for more aggressive attachment
•   EAF (entrained air flotation)
-Bubbles produced with relatively low pressure and high shear, entrained in the water

Dissolved Air Flotation

DAF Pumps

DAF Design