Which chemical is commonly used in water treatment to kill bacteria?

Chlorine is commonly used in water treatment processes primarily due to its effectiveness as a disinfectant. It works by killing bacteria, viruses, and other pathogens present in water, thereby making it safe for human consumption. Chlorine is favored because it not only eliminates harmful microorganisms but also provides residual protection, maintaining water quality over time.

While other chemicals like ozone and hydrogen peroxide can also be used for water disinfection, they often lack the stability and residual benefits that chlorine provides. Ozone, for instance, is a powerful oxidizing agent but decomposes quickly, leaving no lasting protection. Similarly, while hydrogen peroxide can disinfect, it typically requires more complex application and may also decompose without creating a lasting effect. Fluoride, on the other hand, is primarily used to prevent tooth decay and does not function as a disinfectant for water supply. This makes chlorine the most effective and widely used chemical for killing bacteria in water treatment.