Aquabio Ltd - Dissolved Air Flotation (DAF)
DAF unit operating at a UK Dairy facility
Typical DAF chemical dosing cabinet
Aquabio provide the REDOX dissolved air flotation systems for industrial and municipal wastewater treatment.
Dissolved Air Flotation (DAF) physico-chemical systems are used for the separation and removal of suspended and colloidal solids, oils, fats and greases from industrial and municipal effluents and the thickening of aqueous primary and surplus activated sludges.
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Principle of Operation
If relative densities of water and particulate suspended solids, fats and oils are sufficiently different, separation can be achieved by simple physical and mechanical means (e.g. gravity clarifiers, tilted plate separators, mechanical oil skimmers). This is often improved with chemical dosing which initiates flocculation and precipitation of dissolved matter.
However, small and emulsified contaminants may remain in suspension for a considerable amount of time and the dissolved air flotation (DAF) process is a well established technique for improving the efficiency and speed of separation. In most applications pre-treatment with pH control and coagulating or flocculating chemicals is required to maximise the removal of contaminants.
The chemically treated effluent enters a flotation chamber where micro-bubbles of air adhere to the solid particles and decrease their apparent density so that they float to the liquor surface for removal by mechanical scrapers.
The microbubbles are created by dissolving air under pressure (>5 bar) into a portion of treated, recycled effluent. The supersaturated recycle stream is reintroduced to the low pressure incoming wastewater at the flotation tank inlet using special, 100% clog free, injection nozzles. After pressure release the resulting microbubbles (40-50 microns) rise slowly through the body of mixed liquor, attaching themselves to the "flocs" and suspended solids. The heavier rapidly settling solids fall to the hopper base for collection and the treated (clarified) wastewater flows under a baffle and over a weir outlet for discharge, further treatment or reuse.
Aquabio work with REDOX DAF systems which differ from conventional systems by achieving very high effective surface loading rates. This is enabled by the special laminar tilted plate device contained within the flotation section which ensures that the Effective Surface Area for separation is retained, in a very low "footprint" and without risk of clogging.
Further information:
Redox B.V.. "The alternative" KCL Flotation systems
This page includes some content courtesy of Redox B.V.