DAF is the workhorse for fats, oils and grease (FOG) — but emulsified oil and shock FOG loads need the right chemistry. This guide covers oil breakthrough and how to demulsify and float it reliably.
Recognise the problem fast, then work through the causes and solutions below.
What you see: Chemically or mechanically emulsified oil stays dispersed and passes through unless the emulsion is broken first.
What you see: Batch discharges (kitchens, food processing) overwhelm the cell, and oil breaks through during the peak.
What you see: Congealed FOG coats nozzles, weirs and the scraper, degrading distribution and skimming over time.
| Check | Target / Action | Typical value |
|---|---|---|
| Emulsion break | Demulsify before flotation | Jar-test confirmed |
| Coagulant/pH | Set for oil break | Ferric/alum, optimum pH |
| Equalisation | Buffer FOG slugs | Steady dosing |
| Skim frequency | Raise at peaks | Clear oily float |
| Internals | Degrease on cycle | Keep distribution even |
Set up correctly, dissolved air flotation turns this failure mode into a controllable, high-performance process.
Flotation is the natural process for buoyant oil and FOG — once emulsions are broken, DAF removes them efficiently where settling cannot.
Correct coagulant and pH break stable emulsions so even chemically emulsified oil floats and is skimmed off.
Free and broken oil is lighter than water, so it rises readily to a skimmable float — DAF's core strength.
With equalisation and flow-paced dosing, DAF absorbs FOG slug loads that would defeat a fixed-rate separator.
Diurnal swings, batch dumps, and shock loads that destabilise the cell.
Drifting sensors, dosing control loops, and SCADA alarm faults.
Material selection, coating failure, and corrosion in aggressive duty.
Wet float, poor cake solids, and downstream dewatering knock-on.
Thin or sinking float blanket — air/solids ratio, saturator, and chemistry fixes.
Cloudy effluent and solids breakthrough — hydraulic, floc, and distribution fixes.
Our process engineers diagnose and resolve complex DAF performance issues on site or remotely — from chemistry and air systems to hydraulics and sludge handling.
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