The recycle pump feeds the saturator; if it cavitates or loses flow, dissolved air collapses and flotation fails. This guide covers NPSH, air ingress, and wear that destabilise the recycle stream.
Recognise the problem fast, then work through the causes and solutions below.
What you see: Suction pressure falls below the pump's NPSH requirement; vapour bubbles collapse, eroding the impeller and starving the saturator.
What you see: Dissolved or entrained air in the suction line makes the pump gas-bind and the saturator pressure hunt.
What you see: Worn impeller or seals reduce developed head, so recycle flow and saturator pressure drift down over time.
| Check | Target / Action | Typical value |
|---|---|---|
| NPSH margin | Suction > NPSHr | >0.5 m margin |
| Suction strainer | Clean on ΔP | Clean if >0.2 bar |
| Submergence | No vortex / air | Fully submerged |
| Pump curve | Verify head/flow | Vs manufacturer |
| Recycle flow | Restore set-point | 8–12% of forward flow |
Set up correctly, dissolved air flotation turns this failure mode into a controllable, high-performance process.
A healthy recycle pump is what lets a DAF supply exactly the air the process needs — restoring it restores flotation directly.
Pressurising only the clean recycle (not the whole flow) keeps pump energy low and the duty point easy to maintain.
Strainers, deaerator pots, and standard centrifugal pumps make NPSH and air-ingress faults routine, planned maintenance.
Recycle flow, saturator pressure, and bearing temperature give clear, trendable indicators of pump condition.
Cutting saturator, recycle, and air-system energy without losing performance.
Viscosity, gas solubility, and freezing effects on winter flotation.
Safe sequencing, priming, and stagnation control around stop/start.
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.
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.