Dissolved Air Flotation DAF

Underlying Technology & Scientific Principle

DAF dissolves air into water under pressure, then releases it at atmospheric pressure to nucleate clouds of 20–50 µm micro-bubbles. The bubbles attach to coagulated oil droplets and suspended particles, lowering their effective density so they float to the surface for skimming.

Working Mechanism

Coagulant and polymer destabilise and flocculate the emulsion; a recycle stream saturated with air in a pressure vessel is injected and flashed across the flotation cell. Rising bubble-floc aggregates form a float blanket removed by surface skimmers, while clarified water is drawn from below.

Separation / Removal Efficiency

With proper chemistry, removes 90–99% of emulsified/free oil and TSS, taking oil-in-water to 5–25 mg/L and removing fine colloids and some metals as hydroxide floc.

Operating Principle & Parameters

Saturation pressure 4–6 bar, recycle 10–30%, air-to-solids ratio 0.005–0.06. Surface loading 5–15 m/h in conventional, up to 40 m/h in high-rate packed DAF.

Flow Rates & Volumetric Capacities

Packages from 5 m³/h skids to >1,000 m³/h basins. Compact high-rate and induced-gas (IGF) variants suit offshore and modular deployment.

Fluid Media Compatibility

CS/SS or FRP cells with lamella packs in high-rate units. Handles saline, warm, surfactant-laden refinery and produced water.

System Schematic & Process Integration

Sits after primary separation and chemical conditioning, ahead of biological treatment, media or membrane polishing.

Options / Variations Available

Dissolved-air (DAF) vs. induced-gas (IGF/CFU); rectangular vs. circular; lamella high-rate packs; nitrogen blanketing for sour service.

System Complexity & Automation Level

Moderate–high — automated coagulant/polymer dosing on streaming-current or turbidity feedback, recycle and skimmer control via PLC.

Applications & Performance Delivered

Contaminant Removal Profile