Tank Aeration & mixing with Venturi Aerators


Principle of Operation

Transvac Venturi Aerators are a mass momentum exchange device which uses the energy of pressurised liquid to entrain, mix and pump air into a secondary liquid.

The Transvac Venturi Aerator uses this principle to entrain air or oxygen (atmospheric or blown) and mix it with liquid for the purpose of aerating and mixing in a process vessel or pipeline. Essentially, recirculated liquid is pumped from the process vessel and into the venturi where it is accelerated through a unique vortexing jet. This results in an area of low pressure and high velocity into which air is drawn and intimately mixed with the liquid under conditions of high shear. The mixture is then forced through the venturi recieving a pressure boost sufficient to overcomethe backpressure created by the head of liquid in the process vessel . The high energy turbulent plume is freely discharged with a velocity capable of entraining the surrounding liquid, following which, the plume changes to a buoyant low density mixture rising to the liquid surface to complete the aeration and mixing process.

Twin barreled, self aspirating, through-wall mounted Venturi Aerator installed in an activated sludge plant

Twin barreled, self aspirating, through-wall mounted Venturi Aerator installed in an activated sludge plant.


Aeration Performance

Recirculating pumps provide the liquid motive power and are chosen to suit the characteristics of the fluid and the venturi. Pumps are normally centrifugal type and are either submersible or drywell mounted. The standard motor power for the self entraining single venturi option is 7.5kW, but will depend upon the application. Multi-venturi systems with single larger pumps are also available.

The ability of the standard Transvac Venturi Aerator to self entrain air at liquid depths up to 6.5m ensures flexibility over the vast majority of applications. At greater liquid depths efficient operation is still achieved by employing higher pressure pumps or blown air. To accomodate deep process vessels (or unusually high oxygen demands) a Transvac 'Forced Air Aerator' has been developed utilising a mechanical blower. High energy efficient aeration and mixing can be achieved in the deepest of vessels (a particular advantage when space is at a premuim).

Standard self aspirating units can operate at tank depths of up to 7 metres and offer typical efficiencies between 1.2 and 1.8 kg02/kWh at standard conditions. High alpha factors, simplicity, reliability and low cost make the Transvac Venturi Aerator very competitive with other forms of aeration equipment on the market.

Twin barreled, self aspirating, through-wall mounted Venturi Aerator installed in an activated sludge plant.

Through-wall twin venturi aerator.

The action of the Venturi Aerator makes it particularly suited to processes that require directional mixing, such as in 'race-track' type oxidation ditches or in-line aeration packaged sewage treatment plants.



Operating Advantages

High shear at the gas/liquid interface, increased surface area as a result of the unique Transvac vortexing action and extended gas/liquid contact times result in superior oxygen transfer rates over other aerator types and greatly improved performance over standard venturi's. Mixing is of fundamental importance to the overall aeration process efficiency.
The Transvac Venturi Aerator requires less air for oxygen transfer than other aerator types because the recirculated liquid provides significant energy to enhance the mixing process. This results in lower operating costs and beneficial process considerations such as reduced off-gas volumes.

Advantages

  • No moving aerator parts
  • High oxygen transfer
  • High alpha factors
  • Minimal maintenance
  • Virtually silent operation
  • No aerosol spray
  • Simple to install and retrofit
  • Materials to suit the process
There are four standard configurations of Transvac self aspirating units:
Free standing self aspirating Venturi Aerator installed in an oxidation ditch
  • Free standing
  • Floating
  • Through-wall
  • Guide rail mounted


Materials of construction

Standard Venturi Aerator materials include stainless steel, carbon steel, PVCu and Polypropylene. Pumps and ancillary equipment materials are selected to suit the process conditions.

Venturi Mixer / Aerators

Free standing, self aspirating, Venturi Mixer / Aerator installed to mix and aerate industrial effluent

Free standing, self aspirating, Venturi Mixer / Aerator installed to mix and aerate industrial effluent


Transvac Mixer / Aerators are a mass momentum exchange device which uses the energy of pressurised liquid to entrain, mix and pump air into a secondary liquid.

The action of the Venturi Mixer / Aerator is ideal for mixing balance tank effluent on industrial plants. The unit not only provides effective liquid / liquid mixing, but it also entrain atmospheric air to further enhance mixing and transfer oxygen into effluent.

The system works successfully with varying liquor depths and for keeping solids in suspension. A connection into the tank from the air stack also enables the unit to operate as a liquid / liquid mixer with no air entrainment.

With no parts within the tank requiring maintenance and with corrosion resistant materials of construction available the Transvac Mixer / Aerator is an ideal mixing device for plants handling aggressive hazardous effluent.

The oxygen transfer feature of the Transvac Mixer / Aerator is used to it's full on food waste balance tank mixing because it can keep the effluent 'fresh', avoiding unpleasant odours.

Mixer / Aerator installed at a food plant for mixing and aerating effluent in a balance tank

Mixer / Aerator installed at a food plant for mixing and aerating effluent in a balance tank


Advantages

  • No moving parts
  • No splashing or aerosol created
  • Operates at variable depths
  • No bridges or bearings used
  • No in-tank maintenance needed
  • Controllable mixing
  • Simple, reliable and robust
  • Virtually silent operation
  • No aerosol spray
  • Materials to suit the process
  • Principle of operation

In operation, recirculated liquid is pumped from the process tank into the aerator where it is accelerated through the patented vortexing nozzle. This results in an area of low pressure and high velocity into which air is drawn. The two streams intimately mix before discharging as a turbulent plume creating horizontal and vertical mixing patterns across the process tank.

Materials of construction

Standard Venturi Aerator materials include stainless steel, carbon steel, PVCu and polypropylene. Pumps and ancillary equipment materials are selected to suit the process conditions.