What is DAF?
Dissolved air flotation or as it is called, DAF is considered to be a water treatment process which helps to clarify the wastewater by the way of removing various suspended solids. This kind of removal is achieved by the way of dissolving air in the water or the wastewater under the pressure which is followed by releasing the air at an atmospheric pressure in a flotation tank. This released air makes tiny bubbles that adhere to the suspended matter which causes this matter to float on to the surface of water from where it is removed using a skimming device. The chemicals too are added in this treatment in order to improve the removal or solids. Dissolved air floatation in Malaysia has been adopted in the recent time to make the use of wastewater and to conserve more water for the coming generation.
Where and why are DAFs taken into use?
DAFs are mostly used in the wastewater treatment system in Malaysia in the industries and industrial wastewater effluents coming from chemical plants, oil refineries, paper mills as well as food and beverage industries. They are also used to remove the suspended oils such as fats, total suspended solids, oil and greases and various other pollutants from the wastewater so that the water becomes suitable for re-use and discharge to any facility of wastewater treatment.
How does DAF function?
The wastewater is fed into the system of DAF and the same is then hit with a stream of whitewater that is recirculated clarified water from the Dissolved air flotation which is further super saturated with the dissolved air. After these two mixtures blend among themselves, bubbles get attached to the solid particulates which gives them enough amount of buoyancy in order to surface in the tank.
Once the solids are well accumulating into the floating layer on the top of the tank, a skimmer then nudges this sludge on to the discharge hopper.
The solids which do not float sink into the V bottom of the tank. The ones that are settled are further concentrated and discharged by the way of an automatically controlled pneumatic drain valve.
The water so clarified flows out by the way of under-over weir on the either side of DAF unit. A quantity of this water is taken into use on the recirculation loop and the rest flows out of the vessel.
What are the common kinds Dissolved air flotation in Malaysia?
Open tank:
This is considered to be the best for the wastewater treatment system in Malaysia which is heavily occupied with a lot of solids. This kind of process needs a good amount of free area for the process of floatation and separation. The open tanks are mostly rectangular in appearance and the same are build longer and wider.
Plate pack:
These are tall tanks which have inclined and corrugated plate packs. The water is introduced in the plate by the way of cross-flow configuration that reduces the distance solids. Once collided with the plate, the light solids accelerate towards upward and heavy particles settle down. The water then enter the plate pack and further exists after separating from colloidal solids.