Which of the given options is NOT a commonly used minor method of disinfection of water during its treatment process?
- ABoiling of water
- BTreatment with silicaCorrect
- CTreatment with ozone
- DTreatment with iodine and bromine
Solution
Concept
Chlorination is the main method of disinfection. Boiling, ozone, iodine, bromine, excess lime, UV rays, KMnO4 and silver ions are minor methods.
Step-by-step solution
1. List the minor methods of disinfection: boiling, excess lime, ozone, iodine and bromine, UV rays, potassium permanganate, and silver (electro-katadyn). 2. Check each option against this list. 3. Silica is not a disinfectant and does not kill germs. 4. So the answer is (B).
Explanation
Silica is an inert material, like sand. It does not kill bacteria, so it is not used for disinfection. Boiling, ozone, and iodine or bromine are all known minor methods of disinfection.
Why the other options are wrong
A: Boiling kills germs and is a minor method. C: Ozone is a strong oxidant and a known minor method. D: Iodine and bromine are used in small supplies, such as for the army and swimming pools.
Shortcut
Silica is inert sand material, so it cannot kill germs.
Common mistake
Some students think ozone is a major method. In standard textbooks, ozone is listed under minor methods because it is costly and leaves no residual.
Correct answer: B) Treatment with silica