For a dual-media filter with 0.5 m of anthracite coal and 0.3 ofsand. Other data for anthracite: specific gravity is 1.67, porosityis 0.5, d90 grain size is 1.5 mm. Other data for sand:specific gravity is 2.65, porosity is 0.4, d90 grainsize is 0.9 mm. The water temperature is 20C, so the mass densityof water (Ï) is 998.2 kg/m3 , density of sand is 1650kg/m3 , density of anthracite coal is 1506kg/m3, the absolute viscosity is 1.002 x 10-3kg/m-s. Assuming a 30% margin of safety for backwash, calculate thefollowing:
a) the recommended backwash rate for the filter (gpm/sf)
b) the pressure drop through the filter during fluidization(psi)
Note: multiply (L/m2-s) by 1.473 to get gpm/sf.Multiply (N/m2) by 0.000145 to get psi.
