Wastewater treatment with a dissolved air flotation (DAF) system is a purification process that uses dissolved air flotation to separate solids and oils, significantly improving the efficiency of impurity removal from wastewater. The Dissolved Air Flotation (DAF) system is used when these contaminants do not easily settle and need to be separated by flotation (rising to the surface).
Steps:
- Water pressurization: part of the already treated water is saturated with air under high pressure.
- Sudden pressure release: This pressurized water is mixed with the raw effluent stream. Upon returning to ambient pressure, the dissolved air forms microbubbles.
- Floc formation and air adhesion: With the aid of coagulants and flocculants (in many cases), the solids clump together into flocs. The microbubbles adhere to these flocs, making them lighter than water.
- Flotation: The flocs rise to the surface, forming a layer of floated sludge. Flotation is a physical process used to accelerate the separation of solid particles and/or less dense liquids present in a liquid phase, due to the introduction of microbubbles of air into the liquid phase.
- Sludge removal: Surface scrapers remove the sludge, while clarified water exits through the bottom of the tank.
The FAD (Floating Action Plan) is widely used in:
- Wastewater treatment plants (WWTP);
- Drinking water treatment plants (WWTP);
- Food, paper and pulp, petrochemical, refrigeration, and dairy industries;
- Treatment of effluents containing oils, greases, or light solids.
Main advantages:
- Excellent removal of oils and greases
- High efficiency in removing suspended solids
- Relatively fast operation
- Can reduce organic load (COD/BOD)
The Dissolved Air Flotation (DAF) system is a versatile piece of equipment used for the treatment of industrial effluents and wastewater, and also for sludge thickening. Its main function is the efficient removal of suspended solids, oils and greases, and the reduction of the organic load in terms of BOD by up to 80%, depending on the characteristics of the effluent.
The DAF system can be used solely as a physical separation system or as a physical/chemical system with the addition of chemicals that provide a clarified liquid phase with reduced values of suspended solids and turbidity. |
