A wastewater treatment plant discharges 1.35m3/s of untreated effluent having an ultimate BOD of 190mg/L and DO of 2.5mg/L into a stream flowing at 14 m2/s. Just upstream from the discharge point, the stream has an ultimate BOD of 4.2mg/L and DO of 6.5mg/L. The deoxygenation constant kd is estimated at 0.25/day at 20C. The river has a constant cross-sectional area of 80m2 and an average depth of 3.5m. The temperature of wastewater and river are both 15C. (a) Assuming complete and instantaneous miving, find the ultimate BOD of the mixture of waste and river just downstream from the outfall. (b) Calculate, tabulate, and plot the ultimate BOD vs, distance for a reach (c) Downstream to 500,000m below the discharge. (d) Find the initial oxygen deficit of the mixture just downstream from the discharge point. (e) Estimate the reaeration coefficient, k, using the O'Connor and Dobbins relationship. You need to use the combined flow rate and make the (f) necessary temperature adjustment to obtain the k, for field temperature. (f) Calculate, tabulate, and plot DO vs. distance (the oxygen sag curve) for a reach downstream to 500,000m below the discharge. You must use MS Office Excel for calculation, tabulating. and ploting. Plot (b) \& (e) on the (g) Find the critical distance to reach the minimum DO, and the minimum DO value. You may check your answers with equations 5.32 and 5.28 to double check your answers. A wastewater treatment plant discharges 1.35m3/s of untreated effluent having an ultimate BOD of 190mg/L and DO of 2.5mg/L into a stream flowing at 14 m2/s. Just upstream from the discharge point, the stream has an ultimate BOD of 4.2mg/L and DO of 6.5mg/L. The deoxygenation constant kd is estimated at 0.25/day at 20C. The river has a constant cross-sectional area of 80m2 and an average depth of 3.5m. The temperature of wastewater and river are both 15C. (a) Assuming complete and instantaneous miving, find the ultimate BOD of the mixture of waste and river just downstream from the outfall. (b) Calculate, tabulate, and plot the ultimate BOD vs, distance for a reach (c) Downstream to 500,000m below the discharge. (d) Find the initial oxygen deficit of the mixture just downstream from the discharge point. (e) Estimate the reaeration coefficient, k, using the O'Connor and Dobbins relationship. You need to use the combined flow rate and make the (f) necessary temperature adjustment to obtain the k, for field temperature. (f) Calculate, tabulate, and plot DO vs. distance (the oxygen sag curve) for a reach downstream to 500,000m below the discharge. You must use MS Office Excel for calculation, tabulating. and ploting. Plot (b) \& (e) on the (g) Find the critical distance to reach the minimum DO, and the minimum DO value. You may check your answers with equations 5.32 and 5.28 to double check your answers
