A municipal WWTP discharges 22.5 MGD of secondary effluent containing 45 mg/L of ultimate BOD at 26.7 oC with 1.3 mg/L of dissolved oxygen. The stream flow is 237 ft3/s at a velocity of 2.1 ft/s and an average depth of 7 ft. The temperature of the stream before the wastewater enters is 16 oC. The stream is 80% saturation with oxygen and has an ultimate BOD of 2.3 mg/L. The reaeration (kr) and deoxygenation (kD) rate coefficients are 0.35 d-1 and 0.2 d-1, respectively at 20 oC. The Arrhenius temperature correction coefficients are f = 1.024 for kr and h = 1.056 for kD.
Determine the following: 1. The wastewater flow rate in ft3/s
2. The temperature of the combined wastewater and stream
3. The DO concentration of the mixture of wastewater and stream
4. The DO deficit of the mixture of wastewater and stream (will need to use linear interpolation of DO values.
5.The ultimate BOD concentration of the mixture of wastewater and stream
6. The distance downstream (xc) to the point of minimum DO concentration and
7. The minimum DO concentration in the stream