CST Wastewater Solutions has released a new dissolved air flotation system based on the latest technology from Europe.

Applications for the DAF include dairy and cheese factories, the paper industry, food industry, oil industry, wineries, tanneries, textile industry, large laundries, chemical industry, refineries, sludge thickening, and primary and secondary clarification in municipal and industrial biological wastewater plants.

Each DAF system incorporates a CST-supplied SAT air dissolving reactor, which is the key to the dissolved air flotation process. The SAT generates the micro bubbles that separate and thicken the suspended solids. Its unique double-injector air dispersal method results in an exceptional dissolving air efficiency up to 90 per cent, higher than any other on the market.

The first stage of air dissolving, up to a theoretical maximum saturation of 50 per cent, occurs in the high turbulence, high intensity mixing zone of the central tube inside the vessel .

The second stage occurs in the larger volume of this vessel, where longer air-liquid contact provides a large exchange with very fine bubbles and a high exchange surface. The added 30-40 per cent dissolution takes places during this second stage.

The CST SAT is also capable of improving the performance of existing flotation systems that employ low efficiency micro bubble generators.

The unique part of the flotation unit is its multifunctional central column, through which the raw wastewater and saturated recycle water is fed and uniformly distributed into the flotation cell; the central column also collects the clarified water and thickened sludge .

Raw wastewater, mixed with air saturated recycle, is introduced into the main body of the flotation tank through a series of openings located around the circumference of the lower part of the central column.

Solids are rapidly carried to the surface by the micro bubbles and are evenly distributed as sludge on the surface of the flotation tank in a uniform hydrodynamic condition.

The sludge float is then removed by a rotating adjustable scroll scoop or by a surface skimmer, without disturbing the sludge blanket.

The DAF system’s designer, Aqua Engineering, has built more than 400 wastewater treatment units over a 30 year period. Key characteristics of the DAF system from CST Wastewater Solutions include:

  • high saturation efficiency > 90 per cent
  • complete dissolving of injected air
  • automatic control of the injected air
  • automatic control of the sludge blanket
  • flexible operation: recycle, partial flow or full flow

Access and maintenance are facilitated by: 

  • a low-head circular tank
  • a bottom sediment removal system
  • a continuous cleaning system for the inside wall
  • an inspection window for visual control of the flotation process
  • no requirement for purging of excess air (no purge valve)

DAF models available from CST Wastewater Solutions range in size from 1.48 – 15.40 metres in diameter and 1.00 – 2.58 metres in height.

The SAT air dissolving reactor operates automatically, requires no maintenance, and has a unique non-clogging design. It is manufactured entirely from AISI 316 stainless steel and is tested and certified to gas pressure vessel codes.

SAT models available from CST Wastewater Solutions range in diameter from 0.114 – 1.6 metres and from 1.48 – 3.84 metres in height.


With Surface Scoop


With Surface Skimmer