Operator terms · Water
What is sedimentation in water treatment?
Sedimentation is letting water sit still enough that heavier particles and floc settle to the bottom by gravity, before filtration. It removes most of the suspended load so the filters are not overwhelmed. It happens in a basin or clarifier, and the settled material is removed as sludge.
Last reviewed 2026-08-03
Where it fits
Sedimentation follows coagulation and flocculation and comes before filtration. By dropping out most of the floc first, it lets the filters do the fine polishing.
What settles out
The floc built during flocculation, along with heavier grit and particles. The settled material is drawn off the bottom as sludge.
Common questions
- What drives sedimentation?
- Gravity, once the water is slow and still enough.
- What comes after it?
- Filtration, then disinfection.
- What is removed?
- Settled floc and heavier particles, drawn off as sludge.