For a given discharge, the efficiency of sedimentation tank can be increased by :

Explanation:

The efficiency of the Sedimentation Tank:

• The efficiency of the sedimentation tank indicates the overall percentage removal of suspended matter at a given overflow rate or surface loading rate.
• The efficiency of the sedimentation tank increases if the overflow rate reduces (more time available to particles for settle).

overflow rate, 

From the equation, it is clear that if the surface area (B × L) of the tank increases, the overflow rate reduces, and efficiency increases for a given discharge.

Efficiency depends on the following parameter during sedimentation:

• The velocity of flow: Efficiency increases if the velocity of flow reduces
• Viscosity: Efficiency increases if viscosity reduces (Viscosity changes but we can not do)
• Size of particle: Efficiency increases if the size of particle increases.