Which byproduct is formed when ozone is used for disinfection and is commonly monitored for public health protection?

• A. Bromate
• B. Chloroform
• C. Chlorite
• D. Haloacetic acids

Answer: (A)

Using ozone for disinfection can generate bromate as a byproduct when ozone oxidizes bromide present in the source water. This byproduct is routinely monitored for public health protection because it has health concerns and is regulated to keep exposure low. Utilities control bromate formation by adjusting the ozone dose, contact time, and managing bromide levels in the source water. The other substances listed are typically formed with chlorine-based disinfection: chloroform and haloacetic acids come from the reaction of chlorine or chloramines with natural organic matter, while chlorite forms with chlorine dioxide. Since the scenario involves ozone, bromate is the byproduct to monitor.