Compared
Coagulation vs. flocculation
Coagulation and flocculation are back-to-back steps that clump tiny particles so they can settle. Coagulation adds a chemical and a fast mix to neutralize the charges that keep particles apart. Flocculation then stirs the water slowly so the tiny clumps bump together into larger, heavier floc.
Last reviewed 2026-08-04
| Coagulation | Flocculation | |
|---|---|---|
| Order | First | Second |
| Mixing | Fast, rapid mix | Slow, gentle mix |
| What happens | A chemical neutralizes particle charges | Small clumps grow into larger floc |
| Goal | Start the clumping | Grow floc big enough to settle |
The bottom line
Coagulation starts the clumping with a chemical and a fast mix; flocculation grows the clumps with a slow, gentle mix.
Common questions
- Which comes first?
- Coagulation comes first, then flocculation.
- Why is the mixing speed different?
- Fast mixing spreads the chemical; slow mixing lets floc grow without breaking apart.
- What comes after?
- Sedimentation, where the heavier floc settles out.