Primary Treatment (Sedimentation) | Activated Sludge Process | Wastewater Treatment Plant

 Primary Treatment (Sedimentation)

Primary treatment is a physical (non-biological) treatment process that occurs in a tank and allows substances to settle or float and be separated from the treated water.

Purpose

• Prior to secondary treatment, remove all settleable and floating solids.

Process Description

• Flow is controlled (reduced) so that settleable solids sink to the tank's bottom and lighter materials rise to the water's surface.
• Primary clarifiers are another name for primary sedimentation tanks.
• The layer of solids that settles out is known as the sludge blanket.
• Solids that settle out in the primary clarifier must be removed (wasted) to digestion on a regular basis.
• A surface skimmer removes floating material and transports it to the digestion process.
• If the sludge removed is watery and insignificant, the removal rate may be too fast.

Sludge is described as settleable solids separated from liquids during processing or foreign material deposits on stream or other bodies of water's bottoms.