DAF systems for wastewater treatment

August 14, 2022 (Read 5 mins)
Jordi Fabregas

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

Wastewater treatment by dissolved air flotation (DAF) systems is one of the most widely used processes due to its efficiency and versatility, as it has applications in industrial and municipal wastewater treatment, desalination plants and water reuse systems.

DAF systems offer high performance in the removal of solids, oils, grease and associated organic matter, with a removal of more than 90%. In addition, SIGMADAF Clarifiers DAF equipment can be adapted to treat all types of water and pollutants.

What are DAF systems?

DAF systems are equipment for the separation of solid particles, grease and oils, designed to clarify wastewater (industrial and municipal). They are also used in the pretreatment of surface and marine waters for subsequent treatment and reuse.

Dissolved air flotation equipment separates solids, fats, oils and grease present in the water, generating highly concentrated sludge. In addition, they allow a substantial reduction in Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD).

How does a DAF system system works?

Dissolved air flotation is an excellent technology for effective separation of solids, oils, grease and flocs from wastewater.

The wastewater is pumped from the coagulation-flocculation system, which is a system upstream of 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 wastewater containing non-floating solids that require a large surface area for flotation and separation. Flotation air is necessary to enhance particle flotation when particle specific gravity is affected by a mixture of emulsions, oils and solids.

A recirculation pump redirects part of the clarified water to the outlet of the DAF unit, where a pressurization/saturation system is located. 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 or 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. On the other hand, the floated particles are redirected directly to the dewatering system, located at the top of the unit, where they are removed by a system of skimmers.

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

The clarified water leaves the DAF 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 this video we can see the tests of a DAF system with clean water free of solids, which allows us to 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 appropriate chemical dosing, is highly effective in removing grease, oil, suspended solids, turbidity, color, bacteria, algae, iron, manganese, phosphorus and total organic carbon.

Advantages of DAF systems

These are some of the advantages of our dissolved air flotation systems:

  • High quality of treated water.
  • Adaptability of DAF equipment and coagulation-flocculation and pH adjustment systems. Each unit is manufactured taking into account the type of water to be treated and the requirements of pollutant concentrations in the clarified water.
  • Fast start-up.
  • Thicker sludge, therefore lower sludge production and reduced sludge management costs.
  • Footprint reduced.
  • Easy to operate.

In the following video compilation, we can see several of our DAF equipment in operation.

 
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A DAF system for every flow rate and industrial need

At Sigmadaf we have different models of DAF systems that have been designed for the clarification of wastewater in all types of industries.

DAF FPAC

The DAF FPAC are ideal for the treatment of small to medium flows with very high suspended solids loads, which require a large flotation surface to ensure good flotation and separation of solids. These units are capable of treating up to 40kg of dry matter per m².

They can be installed together with biological flotation reactors FBR, can act as sludge thickeners, and are high performance equipment in rendering, meat industries and slaughterhouses (poultry, pork and beef), food, mining, petrochemical and paper industries, among others.

DAF FPBC

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

They are ideal for high flow rates and low to medium suspended solids loads, including low buoyancy particles.

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.

DAF FPHF

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

These DAF units have applications in drinking water treatment using biological flotation reactors FBR, sludge clarifiers, or MBBR moving bed biofilm reactors, and offer high performance in the textile industry, oil refineries, dairy industry and paper industry, among others.

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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