3. The river downstream from the lake in the previous problems receives discharge from a nearby plant that primarily uses bioreactors. The discharge (which is primarily dead, proprietary/engineered microbes) is composed of 27 mg/L of C5H7NO2 (MW = 131.11 g/mol). It is determined that the deoxygenation rate constant of the waste at the reference temperature (i.e., 20 C) is equal to 0.33 day', and the dissolved oxygen concentration of the waste is equal to 1.4 mg/L. The river is 28 m wide and 1.2 m deep. The temperature of the river and the wastewater effluent are both 23 C. The wastewater effluent enters the river at a rate of 0.45 m3/s and has a dissolved oxygen concentration of 9 mg/L. The upstream river has an initial BOD of 6.7 mg/L, and an initial dissolved oxygen concentration of 9.9 mg/L. The saturated dissolved oxygen concentration of the river is 13.1 mg/L. Determine: (49 pts) (i) The minimum dissolved oxygen concentration after the discharge enters the river (39 pts) (ii) The dissolved oxygen deficit and the BOD used 5 km downstream of where the discharge enters the river (10 pts) Assume the upstream river does not contain any of the proprietary microbes. C5H7NO2 + 5 O25 CO2 + 2 H2O + NH3