Question

A mass balance is performed for a treatment process consisting of a sedimentation tank followed by a mixing tank. First, 25080 m3/d of raw wastewater with solids concentration of 180 mg/1 flows into the sedimentation tank. 80% of the incoming solids end up in the sludge. The effluent flows at a rate of 1040 m3/hr. Next, the effluent of the sedimentation tank enters the mixing tank where it is mixed with pure filtered water.

Assume that the density is the same for all streams.

Calculate the following:

a) Flow (m3/d) of the sludge in the sedimentation tank.

b) Solids concentration (mg/1) of the effluent in the sedimentation tank

c) Flow (m3/d) of the pure filtered water, knowing that that the final effluent of the mixing tank will be used in irrigation with a maximum solids concentration of 80 mgl.

Answer 1