Question

1. A city roughly the size of Lawrence is discharging an average of 10 MGD of wastewater into a nearby river, and the concentration of phosphorus (P) in the wastewater is 1.00 mg/L as P. Assume that the average flow in the river is 4,000 cubic feet per second (cfs) and that the concentration of P in the river, upstream of the point of discharge, is 0.05 mg/L.

A. How many U.S. tons of P is the city discharging into the river each year? (2000 lbs = 1 U.S. ton)

B. What is the concentration of P immediately downstream from the discharge point, assuming that the discharge is completely mixed into the stream and that no loss of P occurs, e.g., due to sedimentation, etc. (1 MGD = 1.547 cfs)

Answer 1