HOW DOES A DAF (Dissolved Air Flotation) SYSTEM WORK?
How does a DAF system work? Wastewater is pumped into a DAF (Dissolved air flotation) system and mixed with a stream of “whitewater”, which is recirculated clarified water from the DAF that is super saturated with dissolved air. As these two stream mix together, microscopic bubbles attach to solid particulates, giving them enough buoyancy to go to the surface of the DAF tank.
As solids accumulate in a floating layer of sludge on the top of the DAF tank, a skimmer gently pushes the sludge toward a discharge tank or hopper.
Any solids that don’t float will sink to the “V” bottom of the DAF tank. Settled solids are concentrated and discharged by an automatically controlled pneumatic drain valve.
The clarified water flows out via an under-over weir on either side of the DAF unit. Some of this water is used in the recirculation loop while the rest flows out of the vessel for discharge or further treatment.
Typically, with the use of chemical coagulation prior the DAF, up to 95% reduction of TSS, BOD, FOG can be achieved or up to 75% reductions without chemicals. DAF is can be used a first step prior to biological wastewater treatment as it will be remove a good portion of the nutrient load and therefore reduce the size of the biological treatment system, along with providing an even quality of effluent.