In order to evaluate the impact of a waste on a receiving water, we must calculate the concentration of the waste as it mixes with the stream and how that concentration changes as the waste moves downstream, degrading as it travels. The first step involves a mixing basin analysis, and the second applies first-order kinetics in a plug flow reactor. A steel mill waste is dis-charged at a rate of 0.75 m3/s; the waste has a dissolved oxygen (DO) concentration of 3 mg/L, a CBOD equal to 229 mg/L and an NBOD equal to 114 mg/L. The river receiving the waste has a.flow of 6 m3/s and travels at a velocity of 9 km/day. The river has an ammonia-nitrogen concentra-tion of 0.5 mg NH3-N/L, a CBOD of 2 mg/L, and a dissolved-oxygen (DO) concentration of 6 mg/L upstream of the discharge. Calculate the DO, NBOD, and CBOD in the river immediately after it becomes mixed with the waste and the NBOD, NH3-N, CBOD, and CBOD518 km downstream of the point of discharge. Assume a rate constant for ammonia oxidation (kA,) of 0.15 day" and a rate constant for CBOD exertion of 0.1 day".