The sludge stream from a sedimentation tank is flowing at 10

The sludge stream from a sedimentation tank is flowing at 100,000 gal/day and contains 1.5% solids. Assume the solids have a specific gravity close to 1.0.

a) Calculate the mass flow rate of this sludge stream as is (sludge and water) in kg/day and lb/day.

b) Calculate the mass flow rate of sludge on a dry basis.

c) If the sludge is thickened to 12% solids on a belt filter press, what is the mass flow rate of the thickened stream?

d) How much water was removed from the sludge to thicken the sludge from 1.5% solids to 12% solids?

Solution

since the sluge solids have a specific gravity close to 1.0 , then the density of the sludge stream is same as the density of water.

a) Mass flow rate of sludge as is :

= 100,000 gal/day X 8.34 lb/gal = 834,000 lb/day

b) Mass flow rate dry basis :

= 834,000 lb/day X 0.015 = 12,510 lb/day of dry solids

c) Mass flow rate at 12% solid : 12, 510 lb/day solids / 0.12 lb solids / lb sludge

= 104,250 lb/day

d) Water Removed : 834,000 - 104,250 = 729,750 lb/day