Dissolve Air Floatation

Dissolve Air Floatation (DAF)

Waste-activated sludge (WAS) from the bioreactors is thickened in a dissolved air flotation (DAF) tank to reduce the volume of sludge that is sent to the digesters. A smaller volume of thickened sludge will result in a higher efficiency of sludge digestion and a lower disposal cost for the digested sludge. Under the effect of air bubbles flowing upwards, the sludge solids are trapped by the bubbles, carried to the surface to form thickened waste-activated sludge (TWAS) and skimmed out of the DAF tank by a skimmer. The thickened sludge is then pumped to the sludge digesters. The subnatant, or cleaner water beneath the TWAS, is sent to the primary clarifier influent channel.