Which statement about chlorine dioxide residuals is true?

• A. It is a weak disinfectant that does not require monitoring.
• B. It is an effective disinfectant and a strong oxidizer, but can be hazardous to handle and requires monitoring of residuals.
• C. It cannot be used for disinfection.
• D. It is primarily used as a deodorizer and not for disinfection.

Answer: (B)

Chlorine dioxide acts as a powerful oxidizing disinfectant in water treatment. This strong oxidative action inactivates a wide range of microorganisms, making it effective for disinfection. Because it is a hazardous oxidizer, it requires strict safety controls and often on-site generation with proper handling procedures. Monitoring the residual chlorine dioxide in the treated water is essential to ensure ongoing disinfection as water moves through the system, while also preventing exposure levels that could pose safety risks. So, the statement that chlorine dioxide is an effective disinfectant and a strong oxidizer, but can be hazardous to handle and requires monitoring of residuals, is true.