Discuss the principles of operation of a primary settlement tank at a sewage treatment works

Question 1

Theory

Answer 1

Only if all particles have sufficient time to reach the floor of the sedimentation basin, will 100% removal be achievable.

Hydraulically, this can be expressed as VP being of the same magnitude as the surface loading rate Vc. If VP is less, then the ratio describes the fraction of particles that will settle.

This could also be expressed in the diagram as the “depth”[%] under the point of entry (on the vertical axis) of a particle that would just reach the floor