The correct answer is D. All of the above.
A grit chamber is a sedimentation tank used to remove coarse solids from wastewater. The flow velocity in a grit chamber is kept between 0.15 and 0.3 m/s to ensure that the grit settles out of the water before it reaches the next stage of treatment. The depth of a grit chamber is kept between 0.9 and 1.2 m to provide enough space for the grit to settle out. The detention period in a grit chamber is kept at one minute to ensure that all of the grit has time to settle out of the water.
The grit that settles out of the water in a grit chamber is typically made up of sand, gravel, and small stones. This grit can be removed from the chamber and disposed of, or it can be recycled and used in other applications, such as road construction.
Grit chambers are an important part of sewage treatment plants because they help to remove coarse solids from the wastewater before it is treated further. This helps to improve the efficiency of the treatment process and to reduce the amount of sludge that is produced.