Dissolved Air Flotation vs Gravity Clarifier

Whether you are using a Dissolved Air Flotation (DAF) clarifier or a traditional gravity clarifier, wastewater contaminants such as suspended solids, oil and grease must be chemically flocculated in order for either system to remove them. The issue becomes: do I wait for the floc to settle to the bottom of the clarifier by gravity or do I float it to the top by injecting dissolved air in a DAF unit?

If your floc is buoyant or slow to settle there is no question that a DAF is the better choice. Of course, you can always add what is called a body feed to increase the weight of the floc particles and increase the settling rate. Bentonite clay is a common body feed, but adding a body feed can dramatically increase the sludge volume.

Overall a DAF is usually the better choice. Advantages include:

  • Smaller foot print
  • More rapid treatment
  • Ability to remove lite floc that tends to float
  • No need for a body feed