Wastewater System: Dissolved Air Flotation (DAF)

Waterworks’ Dissolved Air Flotation (DAF) clarifier is designed for treatment of waste streams that:

Are high in oil and grease (including petroleum products)
Contain suspended or colloidal solids that do not settle in gravity clarifiers

In addition to significant FOG (fat, oil and grease) and TSS removals, most insoluble BOD, COD and metals are also removed in a Waterworks DAF system.

Conventional primary solids removal is recommended prior to DAF treatment. Typically, this involves screening or settling and flow equalization (to balance peak flow and strength). By achieving a more consistent wastewater, the DAF can operate at maximum efficiency.

Wastewater is pumped from the equalization tank to the DAF clarifier at a constant rate. In many applications, coagulants and polymers are added to assist in particulate removal.

The DAF system operates by generating micro air bubbles through the release of high pressure air-saturated water into a non-pressurized clarifier. The pressure release causes pin point bubbles to form throughout the mixed wastewater. Oil and grease and small particulates preferentially attach to the bubbles causing a decrease in apparent specific gravity, thus the solids rise to the surface of the clarifier, rather than sink. The pressurized stream is actually recycled DAF product effluent that is passed through an air saturation vessel prior to injection back into the clarifier.

The surface of the Waterworks’ DAF is referred to as “White Water” due to the action of the very small rising bubbles (individual bubbles are too small to see). A DAF with large visible bubbles will not effectively separate FOG and TSS. A surface skimmer removes the froth containing the oils and solids to a hopper where the bubbles burst leaving only the waste products (sludge). Most of the collected waste can be further treated in sludge digesters as part of the entire process.

Waterworks has commissioned Dissolved Air Flotation systems on project sites such as:

  • Latex manufacturer Mapa
  • Abita Brewing Company
  • White House textile process (India)
  • The Bard and Rusch catheter manufacturers
  • EPA Superfund sites
  • Nestle Foods
  • Premium Vegetable Oils

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