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

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

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

Dissolved Air Flotation (2 of 5)

Dissolved Air Flotation (3 of 5)

Dissolved Air Flotation (4 of 5)

Dissolved Air Flotation (5 of 5)

References Droste, R.L., 1997, Theory and Practice of Water and Wastewater Treatment, John Wiley and Sons, New York (TD430D76 1997), pages 291 – 319 Hendricks, D., 2006, Water Treatment Unit Processes, CRC, New York (TD430H46 2006) , pages 139 – 160 Kawamura, S., 2000, Integrated Design and Operation of Water Treatment Facilities, 2nd Ed., John Wiley and Sons, New York (TH4538K38 2000), 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 .W375 2005), pages 779 – 865 Viessman, W. et al, 2009, Water Supply and Pollution Control, 8th ed., Pearson, Upper Saddle River, pages 330 – 343