Which chemical is most often used to disinfect public water supplies?

Which chemical is most often used to disinfect public water supplies?

• A. Bromine
• B. Chlorine or chlorine compounds
• C. Iodine
• D. Ozone

Answer: (B)

Disinfecting public water supplies relies on choosing a chemical that reliably kills a broad range of microbes and stays active as water moves through pipes. Chlorine and chlorine compounds are most often used because they are inexpensive, highly effective against bacteria and viruses, and crucially, they leave a residual disinfectant in the water as it travels through the distribution system. That residual protection helps prevent recontamination from the treatment plant all the way to taps. Chlorine can be applied in various forms, such as sodium hypochlorite or calcium hypochlorite, and it forms hypochlorous acid in water to rapidly inactivate many pathogens. Other options exist, like bromine, iodine, or ozone, but they have drawbacks for widespread municipal use. Bromine and iodine are less practical for large-scale systems due to cost, taste, or odor concerns, while ozone is powerful but does not leave a lasting residual in the distribution system, which means additional steps would be needed to maintain safety across the entire network. So, chlorine is the standard choice for disinfecting public water supplies because of its effectiveness, cost, and the critical residual it provides throughout distribution.

Disinfecting public water supplies relies on choosing a chemical that reliably kills a broad range of microbes and stays active as water moves through pipes. Chlorine and chlorine compounds are most often used because they are inexpensive, highly effective against bacteria and viruses, and crucially, they leave a residual disinfectant in the water as it travels through the distribution system. That residual protection helps prevent recontamination from the treatment plant all the way to taps. Chlorine can be applied in various forms, such as sodium hypochlorite or calcium hypochlorite, and it forms hypochlorous acid in water to rapidly inactivate many pathogens.

Other options exist, like bromine, iodine, or ozone, but they have drawbacks for widespread municipal use. Bromine and iodine are less practical for large-scale systems due to cost, taste, or odor concerns, while ozone is powerful but does not leave a lasting residual in the distribution system, which means additional steps would be needed to maintain safety across the entire network.

So, chlorine is the standard choice for disinfecting public water supplies because of its effectiveness, cost, and the critical residual it provides throughout distribution.