Explain Dissolved Air Flotation (DAF) and its applications.

DAF removes suspended solids, oils, and grease by dissolving air in water under pressure (3-6 bar) then releasing into flotation tank. Microbubbles (30-100 microns) attach to particles, making them buoyant. Float is skimmed off surface while clarified water exits bottom. Design parameters: air-to-solids ratio (0.01-0.06), hydraulic loading (5-15 m3/m2/hr), and pressure. Applications: pre-treatment for high-solids water, algae removal, oil-water separation, and sludge thickening. Often combined with coagulation.