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Dissolved air flotation systems (DAF) for wastewater treatment

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Wastewater from industrial activities must be treated before being discharged into the local sanitation network, returned to its natural environment, or previously to its reuse.

The diversity of industrial wastewater implies the need for different types of treatments and systems.

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

DAF systems achieve high performance in the removal of solids, oils and fats, and associated organic matter, with the removal of more than 90%. Furthermore, DAF systems from SIGMADAF Clarifiers can be adapted to each type of water and main pollutants to be eliminated.

What are DAF systems?

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

This equipment separates solids, fats, and oils in the water generating highly concentrated sludge. In addition, they allow to substantially reduce the Chemical Oxygen Demand (COD) and the Biological Oxygen Demand (BOD)

How does this water treatment system work?

Dissolved air flotation is necessary for the effective separation of solids, oils, fats, and flocs in wastewater.

The wastewater is pumped from the coagulation-flocculation system: a system prior to a DAF unit where the dosage of coagulants, polyelectrolyte, and pH adjustment products is carried out for the effective formation of flocs.

DAF systems are specially designed to treat water with solids that need a large surface area for their flotation and separation, and that do not have enough buoyancy to float. Also, flotation air is 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 leaving 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.

Inside the DAF unit depressurization occurs, resulting in the generation of air micro-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 adhere 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 dehydration system in the upper part of the unit, where they are eliminated through a system of skimmers specially designed.

The settleable matter descends to the sediment compartment at the bottom of the DAF unit and is discharged by the sludge extraction system.

The clarified water leaves the unit through an adjustable supernatant system. Part of this stream of clarified water will be redirected by the recirculation pump to enter the compression-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 that the generation of micro-bubbles can be clearly visualized, which float from the injection system to the surface.

DAF technology, accompanied by coagulation-flocculation and pH adjustment with a suitable chemical dosage that has been correctly studied, has been shown to be highly effective in removing grease, oils, suspended solids, turbidity, color, bacteria, algae, iron, manganese, phosphorus and total organic carbon.

 

Advantages of DAF equipment

Advantages of a DAF system from SIGMADAF include:

  • High quality of the treated water.
  • Adaptability of the SIGMADAF equipment and coagulation-flocculation system and pH adjustment, exclusive for each type of water and requirements for concentrations of contaminants in the clarification.
  • Quick start-up.
  • Thicker sludge, therefore lowers sludge production and management and treatment costs.
  • Reduced footprint.
  • Easy to operate.

In the following compilation of videos, we can see several DAF systems from SIGMADAF Clarifiers in operation.

A DAF for every flow and industrial need

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:

DAF FPAC

SIGMADAF DAF FPAC for wastewater treatment of small to medium-sized water flows with very high pollutant loads.

 

DAF FPACs are ideal equipment for the treatment of water with small to medium flow rates and with very high loads of suspended solids, which require 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 FBR biological flotation reactors, sludge thickeners, rendering, meat industries and slaughterhouses (poultry, pigs, and cattle), food, mining, petrochemical, and paper industries, among others.

DAF FPBC

 

 

Rendering of the SIGMADAF DAF-FPBC for wastewater treatment in large flows with low to medium pollutant loads.

 

 

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

They are ideal for working with large flow rates and with low to medium loads of suspended solids, even those that contain low buoyancy particles.

It is applied in drinking water treatment, power plants, MBBR clarifiers, meat and slaughterhouses (poultry, pig, and cattle), fish processing industry, mining, petrochemical, and paper industries, among others.

DAF FPHF

Render of SIGMADAF's DAF-FPHG system to remove high pollutant loads in very high flows of industrial wastewater.

The DAF FPHF flotation system is a separate system that uses a combination of cross flow and counter flow to remove high loads of contaminants at very high flow rates.

These DAFs have application in the treatment of drinking water, FBR biological flotation reactors, 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 for each type of industry, wastewater, and pollutant elimination objectives.

Contact us to analyze your case and find an efficient solution for your wastewater, through the contact form on our website, writing directly through the email info@sigmadafclarifiers.com. We also invite you to follow us on Linkedin.