The percentage of filtered water, which is used for backwashing in rapid sand filters, is about
A. 0.2 to 0.4
B. 0.4 to 1.0
C. 2 to 4
D. 5 to 7
Answer:C
The percentage of filtered water, which is used for backwashing in rapid sand filters, is about
A. 0.2 to 0.4 B. 0.4 to 1.0 C. 2 to 4 D. 5 to 7