Dissolved Air Flotation (DAF) is used for the removal of suspended solids from wastewater and for separation and concentration of sludge.
High pressure air is added to a portion of the clarified effluent. This stream is combined with the flow into the DAF. When this pressurized air-liquid mixture is released to atmospheric pressure in the flotation unit, minute air bubbles are released from solution. These minute air bubbles attach themselves to the flocs and they float to the top. The flocs are skimmed of into a sludge holding tank for further treatment. The clarified liquid is discharged from the bottom part of the DAF.
The primary variables for the dissolved air flotation are applied pressure, recirculation rate, solids concentration in the wastewater, surface area of the DAF and retention period.