What does the presence of excessive chlorine in drinking water not effectively do?

The presence of excessive chlorine in drinking water is generally effective in killing bacteria, including pathogens like E. coli. Chlorine is widely used as a disinfectant in water treatment systems due to its ability to eliminate harmful microorganisms. However, when chlorine levels are excessive, it does not enhance its efficacy and can lead to negative effects such as taste and odor issues.

While chlorine can indeed remove tastes and odors associated with certain contaminants, excessive levels may actually result in undesirable tastes instead. Therefore, the most relevant choice highlights that an excessive amount of chlorine does not improve its ability to kill E. coli, as adequate concentrations in general are effective for disinfection. It's important to apply chlorine within recommended limits to ensure effectiveness without adverse effects on water quality.