Sedimentation is a physical water treatment process using gravity to remove suspended solids from water. Wikipedia

The act or process of forming or accumulating sediment in layers, including such processes as the separation of rock particles from the material from which the sediment is derived, the transportation of these particles to the site of deposition, the actual deposition or settling of the particles, the chemical and other changes occurring in the sediment, and the ultimate consolidation of the sediment into solid rock. OmegaWiki

The separation of a suspension of solid particles into a concentrated slurry and a supernatant liquid, either to concentrate the solid or to clarify the liquid. Wiktionary

Separation of a suspension of solid particles into a slurry. Wiktionary (translation)