Because bromine is not as stable as chlorine, if it were used to treat public water supplies, how much more would be needed?

Because bromine is not as stable as chlorine, if it were used to treat public water supplies, how much more would be needed?

• A. Three to four times more
• B. Four to five times more
• C. Five to eight times more
• D. Two to three times more

Answer: (D)

The main idea is how stability of a disinfectant in water affects how much you need to dose to achieve the same disinfection and to maintain a residual throughout the system. Chlorine forms a relatively persistent disinfectant in distribution systems, so a given dose can provide ongoing protection. Bromine, on the other hand, is not as stable in water and is consumed more quickly as it reacts with organic matter and bromide ions. To reach the same level of microbial inactivation and to keep a usable residual, you’d have to add more bromine—about two to three times as much as chlorine. Context helps: the exact factor depends on water quality, pH, and temperature, but the practical takeaway is that a less stable disinfectant requires a noticeably higher dose to match chlorine’s effectiveness and residual. The ranges of four to five times or more, or five to eight times, would overstate the amount needed for typical conditions, while two to three times is the reasonable estimate.

The main idea is how stability of a disinfectant in water affects how much you need to dose to achieve the same disinfection and to maintain a residual throughout the system. Chlorine forms a relatively persistent disinfectant in distribution systems, so a given dose can provide ongoing protection. Bromine, on the other hand, is not as stable in water and is consumed more quickly as it reacts with organic matter and bromide ions. To reach the same level of microbial inactivation and to keep a usable residual, you’d have to add more bromine—about two to three times as much as chlorine.

Context helps: the exact factor depends on water quality, pH, and temperature, but the practical takeaway is that a less stable disinfectant requires a noticeably higher dose to match chlorine’s effectiveness and residual. The ranges of four to five times or more, or five to eight times, would overstate the amount needed for typical conditions, while two to three times is the reasonable estimate.