Drinking water chlorination is the addition of chlorine to drinking water systems. It is the most common type of drinking water disinfection. Disinfection kills bacteria, viruses, and other microorganisms that cause disease and immediate illness. Chlorine is effective and continues to keep the water safe as it travels from the treatment plant to the consumer's tap.
A little over 100 years ago, waterborne diseases like typhoid fever and dysentery were a common part of life in the United States —and a common cause of death, too. In the early 1900s, cities started disinfecting drinking water supplies to kill bacteria, viruses, and other microorganisms. Both the World Health Organization and the Centers for Disease Control and Prevention regard disinfection of drinking water as one of the most important advances in public health.