Civil Engineering MCQJE Level Civil Engineering
COD (Chemical Oxygen Demand) is determined using which oxidising agent?
Environmental EngineeringEnvironmental EngineeringMEDIUM
Choose the correct answer
A
KMnO4
B
K2Cr2O7 (potassium dichromate in acid)
C
NaOH
D
Cl2 gas
Correct Answer
B. K2Cr2O7 (potassium dichromate in acid)
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COD test: K2Cr2O7 (potassium dichromate) in acidic medium (H2SO4) is used to oxidise ALL organic matter chemically at high temperature (~150°C, 2 hrs). COD ≥ BOD always (COD includes non-biodegradable organics). COD/BOD ratio: fresh domestic sewage ≈ 1.5–2; industrial effluent can be much higher.
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