Question

When the fineness of sand increases __________

(a) The bacterial efficiency increases

(b) The rate of filtration increases

(c) The rate of filtration first decrease, then increase

(d) The bacterial efficiency remains constant

I got this question in unit test.

This interesting question is from Slow Sand Filter topic in chapter Filtration of Environmental Engineering

Answer 1

Correct choice is (a) The bacterial efficiency increases

To elaborate: When the fineness of sand increases, the bacterial efficiency increases, but rate of filtration decreases. Fine sand is preferred when high bacteria and turbidity removal efficiency is desired.