The DAF unit acts to remove the suspended solids (Biomass) from the BCR reactor effluent. The BCR reactors convert soluble nutrients into cell mass and the DAF removes the cell mass and inorganic suspended solids from the reactor effluent through dissolved air floatation. The DAF pump recirculates DAF effluent and flash mixes it with ambient air (aspirated on the suction side of the DAF pump). The air dissolves into the effluent under the pressure of the pump.

The air-water solution is then passed through a saturation tank to allow additional time for the air to dissolve and to remove any coalesced air bubbles. The solution is then expanded across diaphragm control valves leading into WSI’s proprietary diffusers inside the body of the DAF. By reducing the pressure of the solution rapidly (expanding), the dissolved air is forced out of solution in the form of micro-bubbles (90% of the bubbles formed are less than 10 µm in diameter).

The small bubbles collect under the biomass floc and float it to the surface, forming a thickened sludge blanket on the surface of the DAF that is raked directly into the aerobic digester. The DAF provides greater thickening of the sludge as well as a reduced footprint from a conventional clarifier. Settled sludge is periodically pumped to the aerobic digester via a Seepex progressive cavity pump.