What is the size of paicle is rapid sand filter?: (A) 0.1 mm, (B) 0.2, (C) 0.5, (D) 0.4 to 0.7 mm
Answer is D. The effective size of the sand paicle is 0.4-0.7 mm in case of the rapid sand filter and 0.2-0.3 mm in case of the slow sand filter. (PARK TB 25th edition pg 774)