The discharge per unit plan area of a sedimentation tank, is generally called A. Over flow rate B. Surface loading C. Over flow velocity D. All the above

The correct answer is: D. All the above

• Over flow rate is the discharge per unit plan area of a sedimentation tank. It is the volume of liquid that flows over the weir per unit time.
• Surface loading is the ratio of the over flow rate to the surface area of the tank. It is a measure of the intensity of sedimentation.
• Over flow velocity is the velocity of the liquid flowing over the weir. It is a measure of the energy of the liquid.

The over flow rate, surface loading, and over flow velocity are all important parameters in the design and operation of sedimentation tanks. They affect the efficiency of the tank in removing suspended solids from the liquid.