Which of the following chemicals are used for disinfection?

• A. Muriatic acid
• B. Calcium hypochlorite (dry form of chlorine)
• C. Sodium hydroxide
• D. Sodium chloride

Answer: (B)

Disinfection in wastewater treatment relies on chemicals that kill pathogens, with chlorine-based disinfectants being a common and effective choice because they release active chlorine in the water to inactivate bacteria, viruses, and other microorganisms. Calcium hypochlorite is a dry form of chlorine that, when dissolved, releases chlorine for disinfection, making it a widely used method for treating wastewater.

Muriatic acid is hydrochloric acid used mainly to adjust pH or clean equipment; it does not disinfect. Sodium hydroxide is a strong base used for pH control and safety against corrosion, not as a disinfectant. Sodium chloride is simply salt and has no disinfectant properties in this context.

Therefore, calcium hypochlorite is the chemical used for disinfection.