Many DAF upsets happen in the first minutes after a start or around a stop. This guide covers priming, sequencing, and stagnation issues so transitions are clean and repeatable.
Recognise the problem fast, then work through the causes and solutions below.
What you see: Feeding the cell before air and chemistry are established gives a slug of poorly treated water and a slow recovery.
What you see: On start, the recycle pump struggles to prime or gas-binds, so the saturator never reaches pressure.
What you see: Standing water and float go septic during stops, so the first water after restart is poor and odorous.
| Step | Action | Note |
|---|---|---|
| 1. Recycle & air | Establish first | Milky white-water before feed |
| 2. Chemistry | Confirm floc | Dose lined up before flotation |
| 3. Ramp feed | Bring up gradually | Avoid slugs |
| Shutdown | Skim blanket down | Prevent septic float |
| Stops | Drain/circulate lines | Avoid stagnation |
Set up correctly, dissolved air flotation turns this failure mode into a controllable, high-performance process.
With a clear sequence, DAF starts and stops cleanly — valuable for plants with intermittent or batch operation.
Once recycle, air and chemistry are established, a DAF reaches stable flotation within one to two retention times.
Start/stop steps are readily encoded in PLC/SCADA, removing operator-to-operator variability at transitions.
Skimming the blanket down before a stop leaves the cell aerobic, so restarts are clean and odour-free.
Emulsified oil, FOG breakthrough, and demulsification chemistry.
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.
Our process engineers diagnose and resolve complex DAF performance issues on site or remotely — from chemistry and air systems to hydraulics and sludge handling.
Our expertise spans multiple industries with sector-specific water treatment solutions.