Consider the following statements in respect of aerated grit chamber: 1. The grit accumulates at the bottom in advancing spiral-flow aeration tanks location ally preceded by grit chambers, led to the eventual development of aerate grit chambers. 2. The excessive wear on grit handling equipment is a major factor for the popularity of aerated grit chambers. 3. Aerated grit chambers are designed to provide detention period of 1 minute at maximum rate of flow. 4. Diffusers are located at 0.45 m to 0.6 m above the bottom of the chamber. Which of the above statements are correct?

Option 3 : 1, 2 and 4 only

The Grit chambers are like sedimentation tank designed to remove inorganic particles by sedimentation process due to gravitational forces and to pass forward the lighter organic matter.

These are aerated by providing outside air through compressors. This diffused air creates spiral current within the grit and helps in sedimentation, called aerate grit chambers. They are widely used because they reduce the wear and tear of the machinery.

The following are some design parameters related to aerated grit chamber:

1.  Detention time:  About 3 minutes.

2.  Air diffusers are located at 0.45m to 0.6 m from bottom of tank.

3. Roll Velocity (velocity of spiral flow) – 0.15 to 0.45 m³/min.

4. Length/Width = 2.5 to 7.

5. Width /Depth = 1 to 5.