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2. A town discharges 18,000m3/d of treated wastewater into a stream. The treated wastewater has a BOD-5 of 12mg/L and a deoxygenation constant of 0.12/d at 20C. The stream has a flow rate of 0.4m3/s and an ultimate BOD of 5mg/L. The DO of the stream is 6.5mg/L and that of the wastewater is 1.0mg/L. Determine the DO and ultimate BOD after mixing. 3. Refer to the previous problem. Determine the DO concentration 5km downstream from the city discharge. Use a stream temperature and a wastewater temperature of 10C. The reoxygenation constant is 0.06/d