Dissolved air flotation DAF systems for wastewater treatment

August 14, 2022 (Read 5 mins)
Laura Castanares
AguaSigma Technology Development Department

Wastewater from industrial activities must be treated before being discharged into the local sewage system, returned to its natural environment, or as a prior step to recycling and reuse.

Dissolved Air Flotation(DAF) wastewater treatment systems are one of the most widely used and one of the most versatile processes, as they can be applied in industrial and urban wastewater treatment, desalination and reuse.

DAF systems achieve a high removal performance of solids, oils and greases and associated organic matter, with a removal of more than 90%. In addition, SIGMADAF Clarifiers DAF equipment can be adapted to each type of water and main pollutants to be removed.

What are DAF systems?

DAF systems are equipment for the separation of solid particles, grease and oils, designed to clarify wastewater (industrial and urban) or to condition surface or marine water for subsequent treatment and reuse.

This equipment separates solids, fats, oils and grease in the water, generating highly concentrated sludge and substantially reducing Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD).

How does this water treatment equipment work?

Dissolved air flotation (DAF) is necessary for effective separation of solids, oils, grease and flocs generated in a wastewater.

The wastewater is pumped from the coagulation-flocculation system: upstream system to a DAF unit where the dosing of coagulants, polyelectrolytes and pH adjustment products is carried out for effective floc formation.

DAF systems are specially designed to treat waters with solids that need a large surface area for flotation and separation, and do not have sufficient elevator force to float. Flotation air is also necessary to improve flotation when the presence of a mixture of emulsions, oils and solids affects the specific gravity of the particles.

A recirculation pump redirects part of the clarified water at the outlet of the DAF unit to a pressurization/saturation system. The recirculated water is pressurized by the pump to approximately 6 bar and mixed with pressurized air. Under these pressure conditions, the air is dissolved in the water.

Depressurization occurs inside the DAF unit, resulting in the generation of micro air bubbles.

Dissolved air micro bubbles allow the removal of solids and flocs that do not have sufficient buoyancy. The bubbles are between 30-50 microns in diameter, essential dimensions for efficient flotation. The bubbles quickly attach to particles of similar and larger dimensions and rise to the surface.

This mixture of water and bubbles is homogeneously distributed in the inlet compartment of the DAF unit under laminar conditions and the floated particles are redirected directly to the dewatering system at the top of the unit, where they are removed by a specially designed skimmer system.

The settleable matter flows down to the sediment compartment at the bottom of the DAF unit and is discharged through the sludge extraction system.

The clarified water leaves the unit through an adjustable supernatant system. Part of this clarified water stream will be redirected by the recirculation pump to enter the compression and saturation system described above.

In the video below, we can see the tests of a DAF system with clean water free of solids extracted from the well, so you can clearly visualize the generation of micro bubbles, which float from the injection system to the surface.

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DAF technology, coupled with coagulation-flocculation and pH adjustment with carefully studied dosing of appropriate chemicals, has been shown to be highly effective in removing grease, oil, suspended solids, turbidity, color, bacteria, algae, iron, manganese, phosphorus and total organic carbon.

Advantages of DAF equipment

The advantages of a SIGMADAF DAF dissolved air flotation flotation equipment include:

  • High quality of treated water.
  • Adaptability of the SIGMADAF equipment and coagulation-flocculation and pH adjustment system, exclusive for each type of water and requirements of contaminant concentrations in the clarified water.
  • Fast start-up.
  • Thicker sludge, therefore less sludge production and lower management and treatment costs.
  • Footprint reduced.
  • Easy to operate.

In the following video compilation, we can observe several SIGMADAF Clarifiers DAFs in operation.

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A DAF for every flow rate and industrial requirement

The DAF technology for water purification that SIGMADAF designs and manufactures according to the needs of each industry and type of water to be treated, can be:


The DAF FPAC is ideal for the treatment of water with small to medium flow rates and very high loads of suspended solids, which requires a large flotation surface to ensure good flotation and separation of solids, being able to treat up to 40kg of dry matter per m².

It has diverse applications in biological flotation reactors FBR, sludge thickeners, rendering, meat industries and slaughterhouses (poultry, pork and beef), food, mining, petrochemical and paper industries, among others.


The DAF FPBC system exerts maximum efficiency in contaminant separation, due to its parallel plate technology.

They are ideal for large flow rates and for measuring low to medium suspended solids loads, even those containing particles of low buoyancy.

It has applications in drinking water treatment, power plants, MBBR clarifiers, meat industries and slaughterhouses (poultry, pork and beef), fish processing industry, mining, petrochemical and paper industries, among others.


The DAF FPHF flotation system is a separation system that uses a combination of cross-flow and countercurrent flow to remove high contaminant loads at very high flow rates.

These DAFs have applications in drinking water treatment, biological flotation reactors FBR, sludge clarifiers, MBBR moving bed biofilm reactors, textile industries, oil refineries, dairy industry and paper industry, among others.

The design of SIGMADAF equipment is specific to each type of industry, wastewater and pollutant removal targets.

Contact us to analyze your case and find an efficient solution for your wastewater, through the contact form on our website, or by writing directly to us at info@sigmadafclarifiers.com.

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