A slurry containing 40% solids by volume is delivered to a rotary drum filter that is 4 ft in diameter and 6 ft long and operates at a vacuum of 25 in.Hg. A lab test is run with a 50 cm2 sample of the...

A slurry containing 40% solids by volume is delivered to a rotary drum filter that is 4 ft in diameter and 6 ft long and operates at a vacuum of 25 in.Hg. A lab test is run with a 50 cm2 sample of the filter medium and the slurry, at a constant flow rate of 200 cm3 /min. After 1 min the pressure across the lab filter is 6 psi, and after 3 min it is 16 psi. If 40% of the rotary drum is submerged in the slurry, how fast should it be rotated (rpm) in order to filter the slurry at an average rate of 250 gpm?