Settling technology is used to remove medium and large heavy particles from water and wastewater – particles that are visible to the naked eye in the form of turbidity and suspensions, have a size from a few microns to 1 millimeter and can spontaneously precipitate. The sedimentation of particles occurs under the force of gravity. The treatment of water or wastewater by this process is often referred to as clarification.

Modern designs of sedimentation tanks used for clarification of water are flow-through, since sedimentation of suspension in them occurs with the continuous movement of water from inlet to outlet. Therefore, the speeds of water movement in the settling tanks are small and are measured in tenths of a mm/s in vertical settling tanks and several mm/s in horizontal, thin-layer and radial ones.

Settler types:

Horizontal sump – a rectangular, elongated in the direction of water movement, reinforced concrete (most often) tank, in which clarified water moves in a direction close to horizontal along the sump.

Vertical settling tank – a round or square (in plan) reinforced concrete or steel tank of considerable depth, in which the treated water moves vertically from the bottom up.

Radial clarifier – a round reinforced concrete or steel tank, the height of which is small compared to its diameter. Water in such settling tanks moves from the center to the periphery in a radial direction close to horizontal.

Thin-layer settler (settler with shallow settling depth). It is one of the most efficient and promising settling tanks. Its essence lies in the laminarization of the water flow, which excludes the influence of the weighing component. Such sedimentation tanks are made of steel, plastic and other materials. Usually they are equipped with lamellas, which can significantly increase the load.

Separately, it is necessary to single out thin-layer settling tanks, in which, to intensify the settling process, an inert material (for example, microsand) is introduced into the water column, followed by the release of inert from the sludge and its return to the process again.

The sediment formed in the settling tanks is usually collected with the help of scrapers in a certain place of the settling tank and then pumped out.

Most often, the settling process is intensified by introducing coagulants and/or flocculants of various nature into the treated water or effluents.