Question

Calculate the head loss through a clean sand filter with a gradation as given by the sieve analysis below. The filtration rate is 2.7 L/m^2*s, and the water temperature is 10 C. The filter depth is 0.7 m with a porosity of 0.45, and the sand grains have a sphericity of 0.75.

Sieve designation number 12 16 20 30 40 50

Fraction of sand retained 0 0.05 0.22 0.51 0.20 0.02

Determine the effective size and uniformity coefficient for the particle size distribution given in problem, using log-probability paper. Determine the backwash velocity for the size distribution in problem.

Answer 1