OVIVO - Model DAF - Dissolved Air Flotation Unit
Ovivo has numerous DAF design options available, including “open end” saturation systems, which are based on sound technical grounds, skid mounted systems and submerged subnatant launder designs. The option of a shallow or tiered system is available where site constraints govern equipment layout. We offer DAF tank covers in steel, aluminum or fiber reinforced plastic (FRP) materials.
Ovivo® DAF units are used to remove suspended solids from liquids in industrial and municipal applications. They are especially effective where oils, fats, fibers, greases or colloidal solids are present. In many applications, Ovivo flotator units recover valuable by-products, partially offsetting the operating cost of the plant.
Circular and rectangular configurations are available. Basic operating principles and many advanced design features are described in the brochure.
- Sludge thickening
- Algae removal
- Membrane pre-treatment
- Backwash recovery
- Municipal sludge thickening (WAS)
- Algae removal
- Oil refinery waste
- Industrial waste including food and beverage, dairy and meat packing
- Pressurization systems generate a uniform flow of air bubbles for optimum solids floatation/removal.
- Single-stage pressurization pump and air compressor methods result in high saturation efficiency.
- Four skimmer arms ensure efficient removal of floating solids.
- Constant and variable speed drives are available to control float removal rate.
- Designs up to 50-ft diameter are standard. Custom sizes are also available.
Our pressurization units incorporate unique design features into the DAF mechanisms to provide a uniform flow of air bubbles for optimum operation and economy, with the pressurization type and flow rate specifically selected for each individual application. The recycled flow pressurization system developed by Ovivo and used exclusively on all our DAF units, generates 50 to 100 micron-sized air bubbles helping to eliminate detrimental coalescing.
A single-stage pressurization pump and air compressor are used to pressurize a portion of clarified effluent in a saturation tank. As a result of the high saturation efficiency, the cost of pumps, saturation tank, and other pressure system components is reduced. Once saturated with air, the pressurized, clean liquid is returned to the raw waste flow for injection into the flotation unit. A unique back pressure valve is specially designed to maintain the proper pressure in the pressurization tank and to aid in the formation of minute air bubbles.
Pressurized flow is released in a conical pattern inside the flotation unit, producing thorough mixing with minimal turbulence. Loss of dissolved air through external piping or distribution systems is prevented. The air-water-solids mixture is uniformly distributed across the flotation tank by action of the inlet diffusion chamber.
Dissolving efficiency of the pressurization tank provides 80 percent or greater saturation. The tank is specially designed to reduce the exit velocity of the pressurized recycle flow to ensure that all free air is removed from the liquid prior to leaving the tank. This feature ensures that turbulence caused by large bubbles is reduced and that the micron-sized bubbles form properly. In accordance with Henry’s Law, more air is dissolved into a given volume of water at increased pressures. A 65 psi system requires less recycled water and produces smaller air bubbles than those operated at lower pressures. Recycled water serves to transport dissolved air to the flotation unit. Minimum recycling reduces hydraulic loading and turbulence, increasing the amount of treatable liquid that can be introduced in a given tank, thus reducing the cost capital and operating costs.
Once air has been dissolved in the recycled liquid, the pressurized stream is released into the flotation unit to provide air bubbles to effect flotation. A shearing force occurs as the pressurized stream contacts the treated liquid. Micro-sized air bubbles form by action of the relief valve and diffuser, and then attach to floc particles in the waste stream at the point of pressure release. Maximum solids capture and high quality subnatant is assured when air bubbles form on solids particles by the three methods of air bubble attachment.