Question

BOD of waste water is estimated by measuring the amount of:

• A. Total organic matter
• B. Biodegradable organic matter
• C. Oxygen evolution
• D. Oxygen consumption

Hint:

Remember: \[ \boxed{\text{BOD = Oxygen consumed by microbes}} \] BOD is used as an indicator of water pollution. \[ \text{High BOD} \rightarrow \text{Highly polluted water} \] \[ \text{Low BOD} \rightarrow \text{Cleaner water} \] This is one of the most frequently asked NCERT facts from Microbes in Human Welfare.

Answer 1

The Correct Option is D

Step 1: Recall the meaning of BOD. BOD stands for: \[ \boxed{\text{Biochemical Oxygen Demand}} \] It is a measure of the amount of oxygen required by microorganisms to decompose organic matter present in water.

Step 2: Understand how BOD is measured. When microorganisms degrade organic pollutants, they consume dissolved oxygen. Therefore, BOD is determined by measuring: \[ \boxed{\text{The amount of oxygen consumed}} \] during microbial decomposition.

Step 3: Interpret the significance of BOD. \[ \text{Higher BOD} \Rightarrow \text{More organic pollution} \] \[ \text{Lower BOD} \Rightarrow \text{Cleaner water} \] Thus BOD directly reflects oxygen consumption by microbes. Therefore, \[ \boxed{\text{Oxygen consumption}} \] is the correct answer. Hence, \[ \boxed{\text{(D)}} \]