For a dual-media filter with 0.5 m of anthracite coal and 0.3 of
sand. Other data for anthracite: specific gravity is 1.67, porosity
is 0.5, d90 grain size is 1.5 mm. Other data for sand:
specific gravity is 2.65, porosity is 0.4, d90 grain
size is 0.9 mm. The water temperature is 20C, so the mass density
of water (ρ) is 998.2 kg/m3 , density of sand is 1650
kg/m3 , density of anthracite coal is 1506
kg/m3, the absolute...