Question

Decreased BOD is an indication of ______.

Options

• high CO₂ contents

• high O₂ contents

• high microbial activity

• low microbial activity

Answer 1

Decreased BOD is an indication of low microbial activity.

Explanation:

BOD (Biochemical Oxygen Demand) measures the amount of oxygen required by microorganisms to decompose organic matter in water. When BOD decreases, it means there is less organic matter (pollution) for microbes to break down. So, microbial activity becomes low because there’s not much food (organic waste) left for them. As a result, the oxygen content (O₂) in the water increases.