Question

A water sample shows high COD but relatively low BOD. This indicates the presence of

• A. Easily biodegradable organic matter
• B. Non-biodegradable organic pollutants
• C. Inorganic salts only
• D. Pathogenic microorganisms

Hint:

Remember: \[ \boxed{ \begin{aligned} \text{High BOD} &\rightarrow \text{Biodegradable organics}\\ \text{High COD with low BOD} &\rightarrow \text{Non-biodegradable organics} \end{aligned} } \]

Answer 1

The Correct Option is B

Step 1: Recall what COD and BOD each measure.
COD measures the oxygen needed to chemically oxidize all organic matter, biodegradable and non-biodegradable alike, while BOD measures only the oxygen microorganisms use to break down the biodegradable fraction.
Step 2: Read the clue in the question.
A high COD paired with a low BOD means the total oxidizable organic load is large, but very little of it is being consumed by microbes.
Step 3: Draw the conclusion.
That gap between COD and BOD points to organic matter that microbes cannot easily break down, that is, non-biodegradable organic pollutants.
\[ \boxed{\text{Non-biodegradable organic pollutants}} \]