Which of the following chemical means of disinfection is commonly used?

Chlorine is a widely recognized and commonly used chemical disinfectant in water treatment. Its efficacy in killing bacteria, viruses, and other microorganisms makes it a preferred choice for disinfecting drinking water and wastewater. Chlorine can be introduced into the water in various forms, such as chlorine gas, sodium hypochlorite, or calcium hypochlorite, providing flexibility in its application.

One of the primary reasons for its prevalence is not only its effectiveness but also its residual qualities; chlorine remains active in the water distribution system, ensuring continued protection against pathogens as water travels to consumers. The establishment of a residual chlorine level helps in maintaining water safety until it reaches the end user.

While other options like ozone and hydrogen peroxide are also used for disinfection, they are not as commonly employed in routine potable water supply. Ozone, for instance, requires specialized equipment and can be more expensive and complex to implement on a large scale. Similarly, hydrogen peroxide is less common and often used in specific applications rather than as a primary disinfectant in general water supply systems. Ultraviolet light, while effective, does not provide a residual disinfectant, making it unsuitable as a standalone method for maintaining long-term water safety in distribution systems.