Question

Which of the following is true for a water sample with BOD value of more than 50 ppm?

• A. The DO content would be less than 6 ppm
• B. The water is clean
• C. The amount of organic matter is very less
• D. The aquatic life will be thriving

Hint:

• High BOD → High pollution
• High BOD → Low DO → Poor aquatic life

Answer 1

The Correct Option is A

Concept: Biochemical Oxygen Demand (BOD) indicates the amount of oxygen required by microorganisms to decompose organic matter.
• High BOD → High organic pollution
• High BOD → Low dissolved oxygen (DO)

Step 1: Understanding the implication of high BOD ($>$50 ppm).

• Indicates heavily polluted water
• Microorganisms consume large amounts of oxygen
• Leads to reduction in DO levels

Step 2: Analyzing options.

• DO less than 6 ppm: True for polluted water → Correct.
• Water is clean: False → High BOD indicates pollution.
• Organic matter very less: False → High BOD means high organic load.
• Aquatic life thriving: False → Low DO harms aquatic life.

Step 3: Selecting the correct answer.
Thus, high BOD implies low dissolved oxygen.