Which of the following is NOT a common disinfectant used in drinking water treatment?

• A. Chlorine-based compounds
• B. Ozone
• C. Soap
• D. UV

Answer: (C)

Disinfection in drinking water treatment relies on agents that actively inactivate or kill microorganisms and, for chemical disinfectants, leave a residual to protect water in the distribution system. Chlorine-based compounds are widely used because they reliably inactivate a broad range of pathogens and provide ongoing residual disinfection. Ozone is a powerful oxidant that rapidly inactivates many microbes. UV light inactivates microorganisms by damaging their DNA as water passes by the UV lamp. Soap, however, is a cleaning agent, not a disinfectant, and it does not provide reliable disinfection for drinking water or leave a protective residual. It can introduce residues and isn’t used for disinfection in water treatment. So soap is not a common disinfectant used in drinking water treatment.