Question

An industry proposes to discharge a waste stream having a flow rate of 0.3 m3/s and a DO concentration of 1 mg/L to a stream with flow 3.0 m3/s and a DO concentration of 7.5 mg/L. The BOD5 of the stream is 2 mg/L. The waste stream has BOD5 of 100 mg/L and a BOD rate -1 -1 -1 constant,K,of0.2d.Thedeoxygenationandreaerationratesofthestreamare0.12d and0.3d, respectively. The DO saturation level of the stream is 8.6 mg/L. The minimum DO downstream from the outfall is mostly nearly:

a) 2.0 mg/L

b) 3.0 mg/L

c) 4.0 mg/L

d) 5.0 mg/L

Answer 1