QUESTION 1.
Wastewater is to be discharged at a rate of 0.88m3/s into a river with K2-20 = 0.25day-1.
During the low water period the flow rate in the river is 10 m3/s at a temperature of 24°C and the dissolved oxygen is 8.5mg/l. Determine the maximum allowable 5-day BOD of the waste at 20°C if the dissolved oxygen content below the outfall is to be not less than 4mg/l.
Assume that the waste temperature is 24°C and that the river water above the outfall is saturated with oxygen of 8.1mg/l.
From the laboratory tests the value of K1 was found to be equal to 0.12 day-1 at 24°C.
Useful Equations
QUESTION 2. The 5-day BOD of a municipal wastewater is 280mg/l. If the ultimate BOD is reported to be 350mg/l, what is the value of the BOD reaction-rate constant?
(b) What percentage of the ultimate BOD of a wastewater has been satisfied after 3 days if the rate constant (base 10) is 0.10 day-1?
QUESTION 3.
If wastewater with dissolved oxygen content 0.8 mg/l is discharged at a rate of 0.22 m3/s into a stream saturated with oxygen (temperature 12.78°C, dissolved oxygen content of 10.6 mg/l) whose flow rate is 1.14 m3/s, determine the dissolved oxygen content of the resulting mixture.
If the stream flow had been only 0.28 m3/s with dissolved oxygen content of 8.1 mg/l and the stream temperature had been 26.67°C, what would be the dissolved oxygen content of the resulting mixture?