Dissolve Air Floatation

Dissolve Air Floatation

  •      Vikas Circular DAF
  •      Vikas  Rectangular DAF

Vikas  Dissolved Air Flotation Clarifier is designed for the removal of suspended solids or water immiscible liquids from process or wastewater to produce an effluent of high clarity and free of objectionable particles or liquid. Dissolved air flotation is best applied to remove materials that normally settle slowly, persist by remaining in suspension, or have a tendency to float.

  1. Algae Removal
  2. Automotive Industry
  3. Bakery Waste
  4. Ballast Water
  5. Canning
  6. Chemical Processing Plants
  7. Fiber Recovery
  8. Heavy Metal Recovery
  9. Latex
  10. Meat Packing
  11. Pharmaceutical
  12. Potato Processing
  13. Poultry Processing
  14. Prepared Foods
  15. Pulp and Paper Mills
  16. Slaughter House
  17. Tank and Truck Cleaning
  18. Tanning
  19. Textiles
  20. Vegetable Oil

How does it work?
Vikas Dissolved Air Flotation (DAF) is a process for the removal of fine suspended material from an aqueous suspension. The term "flotation" indicates something floated on or at the surface of a liquid.
The DAF provides the energy for effective flotation in the form of extremely fine air bubbles, which become attached to the suspended material to be removed. This attachment of nano  bubbles to the particle "reduces" the density of the particle resulting in increased buoyancy, thus effecting flotation. Chemical conditioning is often used to increase the effectiveness of the dissolved air flotation process.
The most reliable and positive method of producing bubbles of the proper size is to dissolve air into water under pressure and to then reduce the pressure of the solution. As the pressure is reduced, the air comes out of solution in the form of micro nano bubbles.
 dissolved air floatation
Wastewater is pretreated with chemicals.

  1. Treated influent is fed to DAF unit.
  2. Recycle is drawn off effluent line and is sent through the air dissolving system and then sent back into the DAF.
  3. Air is released from the recycle flow and the bubbles help to float solids in the DAF tank.
  4. Float is skimmed from the top of the tank.
  5. Clear effluent flows out of the unit.

How do I know if a DAF is right for my process?

Does your process involve:

  1. Clarification of a wastewater stream
  2. Reduction of TSS, COD, and BOD to meet effluent discharge limits
  3. Recovery of suspended material
  4. Reclaiming water for reuse
  5. Thickening of slurries and sludges

Are you interested in:

  1. Minimal operator attention
  2. Low maintenance time and expense
  3. A well-built machine offering long equipment life

If you can relate to these objectives, then follow these steps:

Establish influent and required effluent conditions as accurately as possible
Contact us to assist in making a preliminary selection
Perform lab and scale testing if necessary
Make final selection

Other considerations:

What is immediately upstream and downstream of the DAF?
What is most important: floated solids concentration, effluent clarity, capital or operating cost, etc.?
What have you tried before? Why did/didn't it work?
What materials of construction are acceptable? What are not?
Do you need auxiliary equipment, chemical pretreatment, for example?
Do you need any instrumentation or controls?
Do you have any standard specifications?

There are many factors affecting the operation of a clarification process. Among these are chemical pretreatment; power, water, air, or other utilities; operator attention; cleaning requirements; and maintenance needs. All of these should be considered when selecting a wastewater clarification system.

Effluent dosed with Alum/Polyelectrolyte from flocculation tank is fed into coagulation tube (feed well) situated at the centre of DAF unit. Coagulation tube is a vertical cylinder suspended in the centre of the tank where the flocculated effluent enters tangentially to ensure intimate mixing of the flocculated solids with the micro bubbles which are generated due to depressurisation of recycled effluent (which is also fed tangentially).

When  the mixture of air & solid reach top of coagulation tube, the centrifugal force tends to throw air/solids horizontally towards periphery of the tank & move upwards & outwards to form a blanket of skimming (froth). This accumulated skimming which floats on the top is continuously scraped from the surface by the scraper arm into the scum box.

DAF separation principle is based on the fact that air is soluble is liquid in direct proportion to the pressure applied. The treated effluent is recycled to the saturation vessel by means of high pressure recycle pump where plant air is injected which ensures saturation of this liquid with air. This saturated liquid is depressurised through a valve located on the discharge line of the saturation vessel. Which  is connected to the coagulation tube. When the pressure is released the air dissolved under pressure comes out of the solution in the form of minute bubbles. These minute bubbles get attached to the flocculated effluent & thus forming solids with combined specific gravity less than the effluent, which finally floats to the surface.


Micronising Pumps Or Regenerative Turbine Pump

Vikas regenerative turbine pump or Micronising Pump maximize dissolution rates of gas into liquids and easily mix difficult liquid / liquid solutions making it an ideal pump for a variety of mixing applications.

Pumps generate microbubbles / nanobubbles with an average diameter of 5 µm, much smaller and more densely packed than conventional systems. This allows a higher amount of air to be dissolved into the water flow using smaller pumps. Power consumption has been recorded as low as 1/3rd  of the power consumption of conventional pumps: a dramatic reduction in running cost and CO2 output.
Dissolved Air Flotation (or D.A.F.) is a process in which tiny air molecules bind themselves to Solids particles and then float to the surface of a holding tank, allowing the Solids to be skimmed from the surface.
Through the combination an innovative impeller design, the VIKAS  D.A.F. pump is able to create a sub-atmospheric pressure region in the seal chamber, forming compressed micro-bubbles that are then dissolved into the pumpage. This process helps eliminate the need for an air saturation tank and compressor required in many flotation systems. Vikas 's innovations enhance performance in many existing D.A.F. systems, as well as set up efficiency savings in new designs.

Immediately save on capital cost and plant space by eliminating the need for:

  1. Air compressors
  2. Large dissolving tanks
  3. Frustrating tank level control
  4. In-line static mixers
  5. Ejectors

And replace large centrifugal pumps with the smaller Vikas  microbubble pump
Vikas DAF systems require only 1/5th of the space of most conventional DAF systems. The VIKAS MOCRONISING  pumps suction in air at atmospheric pressure and do not require static mixing devices or long holding periods under pressure like conventional systems.

he Vikas Micronising dissolved air flotation (DAF) pump is a very effective way to separate suspended solids and emulsified oils from industrial waste streams. Microscopic air bubbles are produced during normal operation and mixed with waste water containing the suspended contaminates. The small bubbles attach themselves to the suspended particles, which gives them a net positive buoyancy. These buoyant clusters of particles and bubbles rise smoothly to the surface forming a float which is removed by skimming.

Air and recycled "clean" effluent is introduced to the pump suction. The proportion of air/water is controlled by the operator through simple valves. Under pump discharge pressure this air effluent mixture becomes supersaturated with air micro bubbles. This enriched stream is then recycled back into the dirty effluent and fed to the DAF unit. Up to 35% air can be achieved with 100% saturation and micro bubble size smaller than 30 micron.

In conventional DAF systems, air saturated water is brought into the flotation tank by by means of compressors, pressure tanks and a tension release valve. Due to the cost and nature of the components, typical DAF systems are a large investment that require more maintenance and service and cost more to operate. Vikas DAF system is nearly twice as efficient with lower operation costs.

DAF has become successful due to the excellent purification effect, the low consumption of chemicals and the low maintenance and investment costs. With the Vikas DAF system, Dissolved Air Flotation is taken to new levels of efficiency and performance.

DAF Design Features and Benefits

For DAF applications, Vikas Daf pumps or Micronising Pump meet the following requirements:
Long service life  because of low wear caused by the inevitable contamination of liquids with solid particles. Please remember, proper selection of materials of construction is critical.

Steady pumping characteristics even with changing points of operation.
Sufficient blending of effluent and air to obtain maximum entrainment of air micro bubbles @ 30 micron size.

Standard pumps are not able to meet these requirements. The hydraulic parts of Vikas Micronising pumps have been specially designed to cope with problems which arise when pumping effluent/air mixtures. The distinctive feature of the Vikas DAF  pump is the impeller, open on both sides, and the innovative hydraulic design of the impeller blades.
Vikas Micronising  DAF System Construction Materials
The following materials are available for construction of the Vikas DAF Pumps for the following pH levels for the wastewater stream that you will be pumping:
pH value less than 3 ......................Stainless Steel
pH value 3 to 5.9 ...........................Bronze
pH value 6 to 10 ............................Gray Cast Iron
pH value 11 to 14 ..........................Gray Cast Iron (all iron)
 It has small capacity and high head by one impeller.       
 Easy inspection of pump interior is capable with just removing a suction cover.       
 It  can be used for a wide range of liquid because of it's stainless steel materials.       
 High efficiency saves electric cost.    
Horizontal    Vertical    Wetted parts material    Shaft Seal    Impeller       
 FC    S13    S14    Special    GP    Me            
     -                                  Cascade       
Multi-Stage    High-Head    High-Temperature    Slurry    Support       
-         -    -    Bracket       
     Food & Beverage Industry.       
     Water treatment Industry.       
     Chemical Industry.       
 All other sorts of Industries.       
1.    Stainless Steel SCS13/SCS14/SCS16       
2.    Cast Iron FC200
Ductile Iron FCD450 (For HC Series Pumps)
For cast-iron material the pump model is FR.(However, the impeller is SUS304)    
 -5ºC∼80ºC in case of Cast & Ductile Iron    
Shaft Seal    
1.    Gland packing
       Self and external flushing type       
2.    Mechanical seal.       
     a.    Single mechanical seal.
            Include balanced and unbalanced types.
            Inside and outside types.       
    b.    Double Mechanical Seal.       
    c.    Additional Special Mechanical Seal may be installed on request.       
3.    The shaft seal dimensions are structured to serve as gland packing and mechanical seal.    
Ball bearing (Oil bath system).  
*Base···1 , Coupling···1 , Guard···1 , Anchor bolts/nuts···1    
        (Cascade Pumps Horizontal Type)       
 Item    Designation    Stainless Steel    Cast Iron       
 1    Casing    SCS13    SCS14    FC200       
 2    Suction Cover    SCS13    SCS14    FC200       
 5    Bracket    FC200    FC200    FC200       
 10    Bearing Cover    FC200    FC200    FC200       
 10A    Bearing Cover    FC200    FC200    FC200       
 23    Impeller    SUS304    SUS316    SUS304       
 58    Lantern Ring    PTFE    PTFE    PTFE       
 60    Gland Cover    SCS13    SCS14    FC200       
 69    Seal Cover    SUS304    SUS316    SUS304       
 71    Channel Ring    SCS13    SCS14    FC200       
 72    Channel Ring    SCS13    SCS14    FC200       
 90    Shaft    SUS304    SUS316    S45C       
 95    Bearing Nut    S45C    S45C    S45C       
 97    Key (Coupling Side)    S45C    S45C    S45C       
 97A    Key (Impeller Side)    SUS304    SUS316    SUS304       
 107    Shaft Sleeve    SUS304    SUS316    SUS304       
 116    Bearing Washer    SPC    SPC    SPC       
 122    Deflector    IIR    IIR    IIR       
 130    Ball Bearing    SUJ    SUJ    SUJ       
 131    Ball Bearing    SUJ    SUJ    SUJ       
 147    Gland Packing    
         Wide choice of materials available.    
 152    Mechanical Seal            
 153    Oil Seal    NBR    NBR    NBR       
 153A    Oil Seal    NBR    NBR    NBR       
 163    Oil Gauge    YBsC+Glass    YBsC+Glass    YBsC+Glass       
 164    O-Ring (Sleeve Side)    
          Wide choice of materials available.    
 167    Oil Cap    Acryl    Acryl    Acryl       
 229    Casing Spacer    FC200    FC200    FC200       
 502    Gasket (Casing)    
          Wide choice of materials available.    
 502B    Gasket (Bearing Cover)    Three Sheet    Three Sheet    Three Sheet       
 502C    Gasket (Bearing Cover)    Three Sheet    Three Sheet    Three Sheet       
 1.    Pump selection tables are based on pumping liquid with specific gravity of 1.0 and viscosity          of 1.0mPa·s.       
 2.    Motor output (kW) is shown with dotted lines.       
      Pump Frame and Bore Size       
      Frame No    25    30    40       
      Suction Bore
       (mmØ)    25    32    40       
      Discharge Bore
      (mmØ)    25    32    40       
Due to products improvement, please acknowledge that the above information might change   without a previous notice.       
 If you have any problems viewing our website, please report it using the following link.
 (Cascade Pumps Horizontal Type)       
1.    Pump selection tables are based on pumping liquid with specific gravity of 1.0 and viscosity         of 1.0mPa·s.       
2.    Motor output (kW) is shown with dotted lines.       
 The gas dissolution process utilizing a regenerative turbine pump provides for precise control of  input and output fluid/gas parameters. Once set, a well designed system will return to operating  duty each start-up. The goal is to enlighten wastewater technicians about this high quality gas  dissolving technology and how to apply it. And importantly, the technician may find regenerative  turbine technology has many potential uses which benefit their clients. Gas Dissolution and  Regenerative Turbines Gas is dissolved into a fluid solution through pressure. The regenerative  turbine pump applies pressure through a combined triple action force (centrifugal, axial and  friction) to the gas and fluid during a single pass through the pump head. Whether dissolving  compressed or atmospheric air, nitrogen or other gasses to the fluid, the regenerative turbine  pump achieves the highest possible saturation level at a given temperature. Gas Solubility- Air  Example A common application for this pump technology is the dissolving of air into water.

 The  amount of air that can be dissolved in water increases with the system pressure and  decreases with the temperature.
 Using air as an example, regenerative turbine pump gas dissolution can be calculated as follows:  Solubility Ratio: The solubility of air in water can be expressed as a solubility ratio. Sa = ma / mw  S where a m = solubility ratio a = mass of air (lbm m , kg) w = mass of water (lbm, kg) Solubility-  Henry’s Law Henry's Law states "the amount of air dissolved in a fluid is proportional with the p  pressure of the system”. c = pg / kH c = solubility of dissolved gas where kH p = proportionality  constant depending on the nature of the gas and the fluid g = partial pressure of the gas

 Please note that the solubility of oxygen in water is higher than the solubility of nitrogen. Air  dissolved in water contains approximately 35.6% oxygen compared to 21% in air.
 2 Solubility- Calculation Given Henry Law's constants at a system temperature of 25o C (77o F)  the amount of air dissolved in water can be calculated as: Oxygen - O2 Nitrogen - N : 756.7  atm/(mol/liter) 2 : 1600 atm/(mol/liter) Molar Weights Oxygen - O2 Nitrogen - N : 31.9988 g/mol 2 :  28.0134 g/mol Partial fraction in Air Oxygen - O2 Nitrogen - N : ~ 0.21 2 : ~ 0.79 The oxygen  dissolved in the water at atmospheric pressure can be calculated as: co = (1 atm) 0.21 / (756.7  atm/(mol/liter)) (31.9988 g/mol)= 0.0089 g/liter, ~ 0.0089 g/kg The nitrogen dissolved in the water  at atmospheric pressure can be calculated as: cn = (1 atm) 0.79 / (1600 atm/(mol/liter)) (28.0134  g/mol) = 0.0138 g/liter, ~ 0.0138 g/kg

 Since air is the sum of nitrogen and oxygen it follows: ca = (0.0089 g/liter) + (0.0138 g/liter) =  0.0227 g/liter ~ 0.023 g/kg Applying the above information to the regenerative turbine pump a  performance curve can be graphed. Note that the gas dissolution for air peaks at 10% by volume  under normal system operating conditions of temperatures of less than 100F. Thus with just 80-  85psi the regenerative turbine pump discharge pressure meets or exceeds discharge requirements  for most dissolved air flotation (DAF), membrane and oil recovery applications. Please refer to  Graph 1 at the right. Graph 1 3 Why Change? There are several older technology options to  dissolving gasses into a solution. Examining the resulting quality and efficiency with which the  regenerative turbine pump performs these duties may help convince one to take a closer look.  The pump offers a competitive alternative for achieving gas dissolution in a fluid for the following  reasons:  Generates 20-30 micron bubble release.  Uses low energy consumption.  Gas dissolved  at modest pressures.  Low wear pump fluid interface.  Simple design is easy to implement.  High  efficiency without cavitation.  Safety and control features assure reliability. Design & Applications  Typically a regenerative turbine pump is sized in saturation applications for just 20% of total  system flow. This means they are well suited for dissolved air flotation (DAF), membrane and oil  recovery systems. The wastewater technician will find these pumps useful in the Food and  Beverage, Laundry, Pulp & Paper, Brewery and Petroleum industries. With a little exploration they  will find there are many other special process applications to be found. Close coupled pump- lower  flows Flex coupled pump- higher flows Pump Features Regenerative turbine pumps have a robust  construction. The list below gives some quick reference points to look for in a quality pump  design:  Materials: Stainless steel, iron, brass  Close and flex coupled models  Can be mounted  in many locations  Capacities of 5 to 120+ GPM  Heads in excess of 200 Feet  Economical seals  4 Hydraulic

 Design Regenerative turbine pumps can be offered in single and dual impeller mechanical units.  The internal hydraulic cavity is engineered to achieve maximum capacity and pressure while  minimizing horsepower requirements. The hydraulic cavity design optimizes the fluid pumping  dynamics within the interior passageway to improve the efficiency and overall pressure achieved.  Near complete dissolution of entrained gasses are achieved to the maximum volume possible  during the pump cycle.

This is done in a single pass and equates to minimized horsepower requirements. Optimized hydraulic cavity Impeller Tuning Each regenerative turbine impeller has a profile which is uniquely performance tuned. Tuning is based on both engineered and field testing by optimizing the width and length of the impeller vanes. Significantly reduced horsepower is required by the pump to efficiently dissolve the gas into the fluid. This also has the benefit of improved off peak horsepower requirements. Performance tuned impeller Blade Efficiency Each impeller is built with a blade profile and count which has been engineered for its particular fluid passageway cross-section. The impeller blade count increases the efficiency without complex blade contours. Thus the regenerative turbine pump yields high performance characteristics exceeding those of more expensive units.

Adding It Up Looking back at the air solubility calculations and applying the regenerative turbine pump design results in the expected efficiency. This can be verified by an air rotometer indicator matching the calculated volume. The net result equals a dissolved air release with 20-30 micron bubbles.

This is often referred to as “whitewater”. DAF 20-30 micron “whitewater” 5 Setting Up Gas Dissolution Systems The wastewater technician should select a pump and the piping materials based on fluid type and temperature. It is very important to have full control of the system and build in automatic safety features. A system should be piped such that saturation time is maximized. The regenerative turbine pump should be matched to overall system flow and hydraulic capacity. There are also several system limitations under which to operate.

They are as follows: Discharge Pressure 125 psi Seal Pressure 200 psi Suction Vacuum 26” Hg Speed (Flex) 1750 rpm Speed (Close) 3450 rpm Temperature -20 F to 150 F System Components A well designed gas dissolution system will have a number of components beyond the pump itself. These items are usually either schedule 80 PVC or stainless steel as required.

The list of items are: 1. Regenerative turbine pump 2. Inlet fluid control valve 3. Fluid vacuum gauge 4. Gas flow meter with adjustment knob 5. Gas tubing 6. Injection check valve 7. Discharge pressure gauge 8. Saturation and coalescing purge tank (optional) 9. Safety relief 10. Swing check valve 11. Discharge control valve 12. All necessary connecting piping 13. Mounting frame or plate Example Setup


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