Question:
Wastewater is to be discharged at a rate of 0.88m3/s into a river with K2-20 = 0.25day-1. During the low water period the flow rate in the river is 10 m3/s at a temperature of 24°C and the dissolved oxygen is 8.5mg/l. Determine the maximum allowable 5-day BOD of the waste at 20°C if the dissolved oxygen content below the outfall is to be not less than 4mg/l.
Assume that the waste temperature is 24°C and that the river water above the outfall is saturated with oxygen of 8.1mg/l.
From the laboratory tests the value of K1 was found to be equal to 0.12 day-1 at 24°C.