Necessity:-

• The grit chamber is used to remove the inorganic grit such as sand, gravel, and other mineral matter that has a minimal diameter of 0.15 - 0.2 mm or more.
• Grit chamber also become necessary when sewage include smaller mineral particles that may settle.

Working:-

1. In the horizontal flow type the flow passes through the channel in a horizontal direction.
2. The chamber is designed to give a horizontal straight line flow velocity which is kept constant over varying discharge.
3. The constant velocity to achieve by providing velocity control section such as proportional flow weir at the effluent end of a rectangular channel or parabolic over v shaped channel having varying width with depth.
4. The aerated type of grit chamber consists of spiral flow aeration tank, where the spiral velocity is controlled by dimension , shape of the chamber and quality of air supplied to the unit.