A town discharges 27360m3/d of treated wastewater into a nearby creek. The treated wastewater has a BOD5 of 10mg/L and a k value of 0.12d1 at 20C. The creek has a flowrate of 0.43m3/s and an ultimate BOD of 5mg/L. The DO of the river and the wastewater is 6.5 mg/L and 1.5mg/L, respectively. a) Calculate the initial deficit of the creek after mixing with wastewater. The temperature of the stream and wastewater is 10C. The saturation concentration of the dissolved oxygen is 11.33mg/L at 10C. b) Determine the reaeration constant (kr) and the deoxygenation constant (kd) for the rest of the creek after the wastewater discharge. The average depth of the creek is 5m, the bed activity coefficient is 0.35 and the speed of the stream flow is 0.03m/s. c) Calculate the critical DO and the distance downstream at which it occurs