Home > DAF Systems from CST Wastewater Solutions Achieve Efficient Solids Separation

DAF Systems from CST Wastewater Solutions Achieve Efficient Solids Separation

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article image Sludge Float removed using a Surface Skimmer

CST Wastewater Solutions  has introduced an innovative dissolved air flotation system or DAF system designed for wastewater treatment and engineered in Europe to EU standards.  

Available in Australia for the first time, DAF systems find application in dairy and cheese factories, paper industry, food industry, oil industry, wineries, tanneries, textile industry, large laundries, chemical industry, refineries, sludge thickening as well as primary and secondary clarification in municipal and industrial biological wastewater treatments.  

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 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.  

Michael Bambridge, Managing Director of CST Wastewater Solutions says that their SAT is also capable of improving the performance of existing flotation systems that employ low efficiency micro bubble generators.  

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 systems over a 30-year period.  

Key features of the DAF system

  • 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 1.48m to 15.40m in diameter and 1.00mm - 2.58m 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 0.114m to 1.6m and from 1.48m to 3.84m in height.


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