Problem 9. A stream, with a flow rate of 1.0 MGD and with a BOD (a non-conservative pollutant)concentration of 20.0 mg/L, flows into a pond with 5 million gallons of

water. That pond has a single stream outlet that flows into a second pond with 3 million gallons of water and a single outlet. The rate of decay of BOD is 0.3 day-1. Assuming complete mixing within each pond, find the BOD concentration leaving the first pond, and the concentration of BOD leaving the second pond. (Assume steady state)