1. An industry discharges 0.5 m3/s of a waste with a 5-day CBOD of 500 mg/L to a river with a flow of 2 m3/s and a 5-day CBOD of 2 mg/L Calculate the 5-day CBOD of the river after mixing with the waste.
2. A waste having an ultimate CBOD of 1,000 mg/L is discharged to a river at a rate of 2 m3/s. The river has an ultimate CBOD of 10 mg/L and is flowing at a rate of 8 m3/s. Assuming a reaction-rate coefficient of 0.1/day, calculate the ultimate and 5-day CBOD of the waste at the point of dis-charge (0 km) and 20 km downstream. The river is flowing at a velocity of 10 km/day.