Question

BOD of polluted water is estimated by measuring the amount of ________.

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

Hint:

BOD acts as an indirect proxy: we physically measure the {demand for oxygen} (oxygen consumed) to mathematically estimate the amount of biodegradable organic matter.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept: Biochemical Oxygen Demand (BOD) is a standard environmental parameter used to quantitatively evaluate the level of organic pollution in a given water body.
Step 2: Key Formula or Approach: Analyze the definition of BOD to understand the exact physical parameter that is directly measured during the laboratory test.
Step 3: Detailed Explanation: BOD is technically defined as the amount of dissolved oxygen needed (or continuously consumed) by aerobic biological organisms to break down the organic material present in a given water sample at a specific temperature over a specific time period.
Because microorganisms actively consume oxygen as they metabolize and decompose the biodegradable organic matter, we can infer the amount of pollution indirectly.
We do not directly measure the physical mass of the organic matter itself. Instead, we measure the rate of oxygen uptake (consumption) by the microbes in the sealed water sample.
A higher rate of oxygen consumption strictly indicates a higher BOD, which in turn reflects a higher level of polluting organic matter in the water.
Step 4: Final Answer: Therefore, BOD is estimated directly by measuring the amount of oxygen consumption.