Why is disinfectant added?

• A. To clarify water by removing turbidity only
• B. To eliminate harmful microbes and maintain residual protection
• C. To flavor the water
• D. To adjust pH to neutral

Answer: (B)

Disinfection in drinking water is about killing or inactivating harmful microorganisms and keeping a residual level of disinfectant in the distribution system so protection lasts until the water reaches consumers. This residual helps prevent recontamination in pipes and storage. Other steps in treatment focus on removing particles, improving taste, or adjusting pH, but none provide the ongoing microbial protection that disinfection supplies. So the essential purpose of adding a disinfectant is to eliminate harmful microbes and maintain residual protection.