With reference to treatment of waste water, the skimming tanks are used for:

Concept:

Aeration:
Taste and odor, both are undesirable in water. Aeration is done to remove taste and odor. Aeration is done to promote the exchange of gases between the water and the atmosphere. In the water treatment, aeration is performed for the following purposes,

• To add oxygen to water for imparting freshness, for example, water from underground sources may have lesser oxygen.
• For the expulsion of carbon dioxide, hydrogen sulfide, and other volatile substances causing taste and odor.
• To precipitating impurities like iron and manganese especially from underground water.

Grit Chamber:

• The heavy inorganic materials (specific gravity 2.4 - 2.7) like sand, ash, and others. It can be Removed by using grit chambers, this is a technique based on the process of sedimentation due to gravitational forces.

Skimming Tank:

• A skimming tank is a chamber so arranged that the floating matter like Oil, fat, grease, etc. Rise and remain on the surface of the wastewater (Sewage) until removed, while the liquid flows out continuously under partitions or baffles.

Screening:

• These are placed before grit chambers so as to trap and remove floating matter, such as pieces of cloth, paper, wood cork, hair, fiber, kitchen refuse, fecal solids, etc in the sewage.
• Those floating material if not removed will choke the pipes or adversely affect the working of the pumps.