Which device is specifically used to remove floatable materials during primary treatment?

• A. Grit screen.
• B. Rectangular and Circular clarifiers.
• C. UV-VIS.
• D. DAF unit.

Answer: (D)

Removing floatable materials relies on making buoyant particles rise to the surface rather than settle. A Dissolved Air Flotation unit does this by releasing microbubbles into the wastewater, which attach to fats, oils, grease, and other floatables. The attached bubbles bring these materials to the surface as a scum layer that is skimmed off, effectively removing floatables during primary treatment. Other options focus on different tasks: grit screens remove heavier inorganic solids, clarifiers primarily settle solids, and UV-VIS is for disinfection or measurement, not floatable removal.