ABL Environmental Consultants Ltd

- Model DAF - Dissolved Air Flotation


ABL has designed a Dissolved Air Flotation (DAF) system for use in water and wastewater treatment, marketed through Rawdon Technologies Limited in Nova Scotia. ABL's early experiences in DAF, troubleshooting various manufacturers' products and applications, led to the design and construction of the Rawdon Pilot Trailer. This trailer is equipped with a DAF clarifier nominally rated at 50 GPM and filter capacities to 30 GPM, and is used to evaluate the effectiveness of the DAF process for specific applications.


DAF is a clarification process whereby the removal of suspended solids is achieved by the introduction of tiny air bubbles, which adhere to the suspended floc and float it to the surface, forming a layer which can be removed by a skimmer. ABL has applied DAF to the treatment of oily wastewater, ship bilge water, lagoon effluent, activated sludge effluents, aquaculture water, firefighting wastewater, power plant water and in municipal potable water treatment, with capacities exceeding 288,000 GPD.


DAF is generally more effective than gravity settling for water treatment. DAF is particularly applicable to highly coloured, low alkalinity, low turbidity water, typical of many surface water supplies. DAF treatment operates on smaller sized floc than gravity settling, which reduces the use of chemical coagulants and flocculants. DAF also achieves very low effluent turbidities, conducive to long filter runs. The froth or float from the DAF is more highly concentrated than the sludge from settling, thereby reducing the cost of sludge management and disposal.


For potable water treatment the process train consists of a rapid mix of coagulants, flocculation, DAF clarification, and multimedia gravity filtration. ABL has designed and successfully implemented several water treatment plants using this principle. In many cases the cost savings have enabled the projects to proceed where conventional technology was considered to be cost prohibitive. Representative projects were completed in Sherbrooke, Stewiacke and Orangedale. Pilot studies proving the applicability of DAF technology were conducted at these and many additional sites. For an example of wastewater treatment with DAF, the Rawdon Pilot Trailer was used to successfully treat the accumulated firefighting wastewater from a tire fire at a major tire recycling depot.

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