Which chemical substance is commonly used for water disinfection?

Correct option is B

Bleaching Powder (chemical name: Calcium hypochlorite) is commonly used for disinfection of drinking water. It releases chlorine when dissolved in water, which kills bacteria, viruses, and other pathogens. It is affordable, easily available, and effective for mass water purification in villages, disaster areas, and public water supplies.
Explanation of each option:
· (a) Lime: Lime is mainly used to soften water by removing hardness (calcium and magnesium salts), but it is not a disinfectant.
· (b) Bleaching Powder: Correct. Bleaching powder is extensively used for chlorination of water to kill disease-causing microbes effectively.
· (c) Potassium Permanganate: Potassium permanganate is an oxidizing agent sometimes used for iron and manganese removal, but not a primary choice for water disinfection.
· (d) Formaldehyde: Formaldehyde is used for sterilizing hospital rooms or instruments, not for disinfecting drinking water because of its toxicity.