This webpage by the U.S. EPA gives basic information about the role of chlorine in disinfecting drinking water in the U.S., including the types of chlorine added and the formation of chlorine disinfection by-products.
EPA (2012): Basic Information about Disinfectants in Drinking Water. Chloramine, Chlorine and Chlorine Dioxide. Washington, D.C.: U.S.: Environmental Protection Agency (EPA) URL [Accessed: 22.05.2019]