Which of the following is not true in case of closing the top of the vessel?

Which of these is the most efficient?

Biological action takes place in a rapid filtration unit.

For plastic type high filtration rate trickling filters what would be depth assumed while designing it?

What is the depth of washing during high-rate water backwash?

While designing a high rate filter what would be the velocity assumed?

As the compression increases, the porosity in filter bed _____

What is the surface area of the River rock (Small) packing material used in trickling filters as the packing medium?