The ultimate BOD of a river just below a sewage outfall is 50.0 mg/L, and the oxygen deficit at the outfall D0 is 2.0 mg/L. The saturation value of dissolved oxygen is 11.0 mg/L. The deoxygenation rate coefficient kd is 0.30/day, and the reaeration rate coefficient kr is 0.90/day. The river is flowing at the speed of 45.0 miles per day. The only source of BOD on this river is this single outfall.
A. Find the critical distance downstream at which DO is a minimum.
B. Find the minimum O.