Fine air bubbles (20-50 microns) that attach to suspended particles, creating a buoyant sludge blanket that rises to the surface for removal.
Free interactive DAF sizing calculator. Calculate dissolved air flotation surface area, recycle flow, saturator volume, and power.
FOG removal food industry DAF systems for fat oil grease recovery food processing.
DAF systems for oil and gas produced water and refinery wastewater treatment.
Design DAF systems for correct hydraulic loading. Surface area, rise rate and detention time calculations for your flow.
Micro-bubbles measuring 20-50 microns provide optimal surface area-to-volume ratio, maximising contact with suspended particles for efficient attachment.
As bubbles rise through the wastewater, they collide with and attach to suspended particles, oils, and grease, forming bubble-particle aggregates.
The combined density of the bubble-particle aggregate is less than water, causing it to rise rapidly to the surface as a float layer.
The float layer is continuously skimmed from the surface, removing the separated solids for further processing or disposal.
Removes up to 99% of suspended solids and oils, achieving superior effluent quality compared to conventional separation methods.
Fast rise velocities enable high hydraulic loading rates, reducing equipment footprint and capital costs.
Works effectively with or without chemical coagulants, adapting to various wastewater characteristics.
Concentrated float can be processed to recover valuable materials like oils and proteins.
Dissolved Air Flotation is a physico-chemical separation process that removes suspended solids, oils, greases, and colloidal matter from wastewater. Pressurised water saturated with air is released into the flotation zone, generating microbubbles that attach to flocculated particles and float them to the surface as a concentrated sludge blanket. The clarified water exits below the floating sludge layer.
Recycle stream pressurised to 4-6 bar in a saturation vessel with optimised retention time.
Pressure release through proprietary nozzles generates 20-80 µm bubbles with high attachment efficiency.
Rising velocity of bubble-particle agglomerates exceeds settling velocity, forcing separation.
Mechanical scrapers or hydraulic suction systems continuously remove concentrated float.
| Hydraulic Loading | 5 – 15 m³/m²/h |
| Solids Loading | Up to 15 kg SS/m²/h |
| Air-to-Solids Ratio | 0.02 – 0.1 kg air/kg SS |
| Recycle Ratio | 10 – 50% of influent flow |
| Flotation Zone Depth | 1.5 – 3.0 metres |
| Retention Time | 10 – 30 minutes |
| Drive Power | 0.37 – 2.2 kW (scraper mechanism) |
| Construction | SS304, SS316L, or carbon steel with epoxy coating |
95 – 99% suspended solids reduction depending on flocculant selection and upstream conditioning.
>98% oil and grease removal for emulsified and free-floating hydrocarbons.
40 – 70% COD removal depending on solids fraction and coagulant optimisation.
Complete dissolved air flotation systems for industrial and municipal applications.
View PageDAF performance ultimately depends on producing bubbles small enough to attach to colloidal flocs and lift them efficiently.
20–80 μm for industrial DAF. Smaller bubbles have higher surface area per volume and slower rise velocity, allowing longer contact. Bubbles <20 μm have insufficient buoyancy.
At saturator pressure (5 bar), water holds 150–200 mg/L dissolved air. Sudden pressure release supersaturates the water; dissolved gas nucleates on surface roughness and existing micro-particles.
Saturator at 5 bar → release into atmospheric flotation cell creates ΔP = 5 bar across orifice. Higher ΔP + sharper orifice = smaller bubbles.
Cold water holds more dissolved air (12–15°C ideal). Hot effluent (>35°C) needs pre-cooling or higher saturator pressure for equivalent A/S.
Hydrophobic surfaces (oils, polymer-conditioned flocs) attach 5–20x more efficiently than hydrophilic. Coagulant/polymer dose tuned to optimise hydrophobicity.
Uniform bubble distribution across the contact zone is critical. CFD modelling identifies maldistribution before fabrication, saving pilot rework.
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