No amount of air can float solids that were never coagulated into liftable flocs. This guide diagnoses chemical-pretreatment failures upstream of the flotation cell and how to restore strong, bubble-friendly flocs.
Recognise the problem fast, then work through the causes and solutions below.
What you see: Under-dosing leaves colloids uncharged; over-dosing re-stabilises and disperses them again.
What you see: Floc is weak and slow even at the right dose because metal hydrolysis is suppressed.
What you see: Either flocs never form (too little rapid mix) or they shear apart (too much, or too late).
What you see: Flocs are too small or too fragile to survive the bubble field.
| Check | Target / Action | Typical value |
|---|---|---|
| Coagulant dose | Jar-test optimum | Site-specific |
| pH | Trim to coagulant window | Alum 6.0–7.5 / Ferric 5–8 |
| Rapid-mix G | Fast dispersion | >300 s⁻¹ for seconds |
| Flocculation Gt | Grow strong floc | 20,000–60,000 |
| Polymer | Screen type & dose | 0.2–1.0 mg/L |
Set up correctly, dissolved air flotation turns this failure mode into a controllable, high-performance process.
DAF rewards good coagulation with fast, complete separation — the bubble step turns well-formed flocs into a dry, removable float.
Bench jar tests and on-site pilot DAF units lock in dose and polymer before full-scale commitment, de-risking the chemistry.
With dose-pacing on flow and turbidity, a DAF copes with swinging raw-water quality that would overwhelm a fixed-rate clarifier.
Because DAF needs only liftable (not heavy, fast-settling) flocs, coagulant and polymer demand is often lower than for sedimentation.
Thin or sinking float blanket — air/solids ratio, saturator, and chemistry fixes.
Cloudy effluent and solids breakthrough — hydraulic, floc, and distribution fixes.
Low dissolved air, oversized bubbles, and white-water faults.
Skim frequency, re-entrainment, and float-handling problems.
Overload and uneven flow that let solids escape the cell.
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.