Problems 1 and 2 thank you

You are an engineer tasked with modeling the dissolved oxygen concentrations along a river that receives effluent from a wastewater treatment plant and also an additional flow from a tributary creek (a creek that flows into the river) 50 km downstream of the treatment plant. Other members of your team will use your calculations to evaluate some policy issues (comparisons to regulatory limits, potential effects on aquatic species, etc.). Your task is to determine: (1) the DO concentration 50 km downstream of the plant (just upstream of the tributary), and (2) the minimum DO concentration downstream of the plant. The river has an average velocity of 7 km/d. At your request, the wastewater treatment plant sends you the following results of lab tests they ran on the wastewater discharged to the river: Wastewater Effluent Measurements Water temperature (C) 18 BOD. (mg/L) 42.5 DO (mg/L) 3.5 Discharge flow (m/s) 3.5 Someone on your team also took some measurements of the river 10 km upstream of the treatment plant and provided you with the following data for your analysis: Upstream River Measurements (10 km above treatment plant) Water temperature (C) 18 BODU (mg/L) 1.0 DO (mg/L) 8.2 Flow (m/s) 9 You don't know the exact deoxygenation and reaeration rate coefficients in the river, but you find some reference values online for rivers with similar conditions: ka -0.22 d'' (0 - 1.135 for temperature adjustments) and kr 0,40 d '@=1.024 for temperature adjustments) at 20C. You also find some saturation concentrations for dissolved oxygen at different temperatures as shown on the next page. Oxygen Saturation Concentrations (Mines & Lackey, Environmental Engineering) Temp (C) 10 11 12 Csat (mg/L) 11.29 11.03 10.78 10.54 10.31 10.08 Temp (C) 16 17 18 Ct (mg/L) 9.87 9.67 9.47 9.28 9.09 13 14 15 19 20