9. A treated wastewater (with a flow of 0.535m3/s, an ultimate BOD of 40mg/L and the DO of 1.3mg/L ) is discharged into a stream flowing at 0.935m3/s. Just upstream from the discharge point, the stream itself has an ultimate BOD of 1.8mg/L and the DO of 6.8mg/L. The deoxygenation constant Kd is 0.23 /day and the reaction rate constant Kr is 0.32/ day. The saturated value of DO in river is 8.38mg/L. a. Find whether the wastewater discharge into the river will reduce the dissolved oxygen below the state standard of 5.00mg/L at any point downstream b. Find the DO at 12km from the discharge if the velocity is 0.7m/s