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NIRMAL Dissolved Air Flotation Scheme
What is Dissolved Air Flotation?
Conceptually, dissolved air and Dissolved Air Flotation you must have seen on several occasions.
Typical example is aerated bottle where you see dissolved gases generated making a straw to float. Same
principle is adopted to treat the waste water and it solves numerous problems as compared to other methods.
The air is dissolved in a treated clear wastewater at a higher pressure. This mixture of air and
water is called as dissolved air. The air in liquid phase in the dissolved air. The pressure drop across the
throttling valve will generate billions of microscopic air bubbles which will make the suspended solids,
precipitates, and oil to float upwards in the form of compact sludge. The smaller the air bubbles, larger is
the overall surface area which exerts larger force on the matter i.e to be floated. The dissolution of air is
done in a specialized NIRMAL Dissolved Air Preparation Scheme as per procedure
Brief Achievements of Dissolved Air Flotation :
- Dissolved Air Flotation is the only system to remove oil in more efficient way than all the other
- The presence of the suspended solids makes more difficult to remove oil as well as the
suspended solids as the suspended solids do not allow the oil to float and the oil do not allow the suspended
solids to settle. The normal oily wastewater does contain the suspended solids. The Dissolved Air Flotation
only can make the oil as well as the suspended solids to float and thus eliminated.
- The Dissolved
Air Flotation requires less retention time than any settling clarifiers/tanks and so it could be accommodated
in a short space.
- The sludge generated by Dissolved Air Flotation is thick due to compression by
- The separation process is in presence of oxygen due to air bubbles making the system
safe free from septic conditions.
- The floatable matter recovered from Dissolved Air Flotation can
be used as recovery in many cases.
Why Dissolved Air Flotation?
- Any presence of free as
well as emulsified oil in the waste-stream prevents you from meeting discharge regulations for oil and grease.
- Removal of free and dispersed oil droplets needed to protect downstream treatment equipment.
Need to reduce overall system operating cost by reducing oil pollutant load on downstream equipment.
- Smaller space requirement About 0.4 sq. m. to 0. 9 sq. m. per m3/hour of the
wastewater for single stage dissolved air flotation clarifier. The overall space could be as low as
1/25th to 1/5th the conventional method. (please note that these figures may be
different for other DAF manufacturers.)
- D. A. F. recovered solids are four to eight times thicken
than gravity sedimentation.
- Lower chemical costs due to effective removal of smaller suspended
- Overall lower energy costs due to higher reductions in the parameters.
oil in the waste stream makes the problems more complex.
- Removal of dissolved or
entrapped gasses in the wastewater like chlorine, carbon dioxide.
- The recovery of floatable matter
makes the Effluent Treatment Plant profit oriented.
Nirmal Engineers have pioneered the Dissolved Air
Flotation Systems into following categories to be useful and practical for several applications.
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Last modified: March 13, 2004
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