Why DAF is fast — micro-bubble rise velocities allow 5–15 m/h hydraulic loading, a fraction of the footprint of gravity settling.
The Science Behind Dissolved Air Flotation
Because bubble-particle aggregates rise far faster than free particles settle, DAF operates at hydraulic loading rates of 5–15 m/h — several times a gravity clarifier — so the tank is compact. This page covers surface and solids loading, the footprint advantage and where loading limits bite.
Turning rise velocity into tank size
5–15 m/h overflow rate including recycle.
Keep below ~8 kg/m²·h to avoid blanket overload.
3–5× smaller than a clarifier for the same duty.
Pressurised recycle adds flow but delivers the air.
Inclined plates raise effective area where space is tight.
Beyond design loading, capture and float quality fall.
| Parameter | Typical | Limit |
|---|---|---|
| Surface loading | 8–12 m/h | ~15 m/h |
| Solids loading | 3–6 kg/m²·h | ~8–12 |
| Recycle ratio | 6–30% | Duty-dependent |
| Footprint | 3–5× smaller | vs gravity clarifier |
Continue across the DAF science series
The micro-bubble DAF overview and hub.
Read MoreAggregate density and Stokes rise that size the tank.
Read MoreSize a DAF and check A/S, loading and recycle.
Read MoreInclined-plate separation, often paired with DAF.
Read MoreWhat DAF removes and how well - TSS, FOG, P, metals, algae.
Read MoreOur process engineers design dissolved air flotation from first principles — separation & loading rates and the full bubble physics — for guaranteed removal at minimum lifecycle cost.
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