Question

There is a dual-media filter with 0.5m of anthracite coal and 0.3m of sand. Other data for Anthracite: Specific gravity is 1.67, Porosity is 0.5, d90grain size is 1.5 mm. Other data for sand: specific gravity is 2.65, porosity 0.4, d90grain size is 0.9 mm. The water temperature is 20°C, so the mass density of water (ρ)is 998.2 kg/m3and the absolute viscosity is 1.002 x 10-3kg/ms. Assuming a 30% margin of safety for backwash, calculate the following:

a) The recommended backwash rate for the filter (gpm/sf)

b) The pressure drop through the filter during fluidization (psi)

Note: Multiply (L/m2s)by 1.473 to get gpm/sf. Multiply (N/m2)by 0.000145 to get psi.

Answer 1

ANSWER :