Question

\(\underline{\hspace{2cm}}\) has the highest Biological Oxygen Demand (BOD).

• A. Corn starch
• B. British gum
• C. C. M. C.
• D. Polyvinyl alcohol

Hint:

In textile sizing, there is a trade-off between biodegradability and pollution: - Natural Sizes (Starch): Highly biodegradable, but this leads to very high BOD in effluent. - Synthetic Sizes (PVA, CMC): Less biodegradable, leading to lower BOD, but they can persist in the environment as chemical pollution (measured by COD - Chemical Oxygen Demand).

Answer 1

The Correct Option is A

Step 1: Define Biological Oxygen Demand (BOD). BOD is a measure of the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample. A high BOD indicates a large amount of biodegradable organic pollution. Sizing agents are a major source of BOD in textile effluent.

Step 2: Analyze the biodegradability of the options.
- (A) Corn starch: A natural polymer made of glucose. It is readily broken down by microorganisms, and this process consumes a large amount of oxygen. Therefore, it has a very high BOD.
- (B) British gum: This is a type of dextrin, which is a modified starch. It is also highly biodegradable and has a high BOD, similar to starch.
- (C) C. M. C. (Carboxymethyl cellulose): A chemically modified cellulose. It is much more resistant to biological degradation than natural starch. It has a significantly lower BOD.
- (D) Polyvinyl alcohol (PVA): A synthetic polymer. While some grades are biodegradable, it is generally much slower to break down than starch and has a lower BOD.

Step 3: Compare the options. Of the choices given, natural, unmodified starch is the most readily and completely biodegradable material, and thus exerts the highest Biological Oxygen Demand.