1. ENG421 (8c) – DAF (Sedimentation)
Dissolved Air Flotation

2. General Water Treatment Technologies (Week 4)
Treatment technologies (unit operations and processes) used determined by what needs to be removed, inactivated or modified

3. Dissolved Air Flotation (1 of 5)
DAF is viable alternate clarification process to sedimentation
very effective for removal of low density particles
process :
tiny are bubbles released under pressure in flotation tank
air bubbles rise from bottom of flotation tank
air bubbles attach to (or enmesh) suspended particles or flocs
higher net buoyant force (due to air bubbles)
→ suspended particles are lifted to the water surface
flocs removed from tank as floating sludge
with appropriate amount and size of air bubbles
particles with densities much higher than water can be removed
to achieve good bubble-floc attachment
may use coagulation
if used, flocculation should be aimed at creating microflocs (or pin floc
between 5 – 30 minutes
significant advantage of DAF
DAF tank much smaller than sedimentation tank

4. Dissolved Air Flotation (2 of 5)

5. Dissolved Air Flotation (3 of 5)

6. Dissolved Air Flotation (4 of 5)

7. Dissolved Air Flotation (5 of 5)

8. References
Droste, R.L., 1997, Theory and Practice of Water and Wastewater Treatment, John Wiley and Sons, New York (TD430D ), pages 291 – 319
Hendricks, D., 2006, Water Treatment Unit Processes, CRC, New York (TD430H ) , pages 139 – 160
Kawamura, S., 2000, Integrated Design and Operation of Water Treatment Facilities, 2nd Ed., John Wiley and Sons, New York (TH4538K ), pages 139 – 194
Metcalf & Eddy Inc., 1991, Wastewater Engineering : Treatment, Disposal, and Reuse, 3rd ed., McGraw-Hill, New York
MWH, 2005, Water Treatment Principles and Design, 2nd ed., John Wiley and Sons, New York (TD430 .W ), pages 779 – 865
Viessman, W. et al, 2009, Water Supply and Pollution Control, 8th ed., Pearson, Upper Saddle River, pages 330 – 343