5. The City of Maskeliya disposes of 2.15m3/s of treated sewagethat still has a BODu of 32.0 mg/L and 2.2 mg/L of DO into a river.Upstream from the outfall, the river has a flow rate of 6.50m3/sand a velocity of 0.45 m/s. At this point, BODu and the DO in theriver are 3.25 and 7.3 mg/L respectively. The saturation value odDO (at the temperature of the river) is 8.9 mg/L, The deoxygenationcoefficient, kd , is 0.61 day-1, and the reaeration coefficient, kr, is 0.74 day-1 . Assume complete mixing and that the velocity inthe river is the same upstream and downstream of the outfall (30points) 1. What is the oxygen deficit and the BODu just downstreamfrom the outfall (just after mixing, before any reaction canoccur?) 2. What is the DO 12 km downstream? 3. Calculate thecritical time and distance 4. What is the minimum DO
