Civil Engineering MCQJE Level Civil Engineering
BOD (Biochemical Oxygen Demand) is measured after incubation for how many days and at what temperature?
Environmental EngineeringEnvironmental EngineeringEASY
Choose the correct answer
A
3 days at 37°C
B
5 days at 20°C
C
7 days at 25°C
D
2 days at 30°C
Correct Answer
B. 5 days at 20°C
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Standard BOD test (BOD5): 5 days incubation at 20°C in darkness. Measures oxygen consumed by microorganisms decomposing organic matter aerobically. BOD5 ≈ 65–70% of ultimate BOD (BODu). Domestic sewage BOD5 ≈ 200–300 mg/L. Higher BOD → more organic pollution.
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