This standard describes chlorination materials, procedures, and requirements for disinfection of new treatment facilities and existing water treatment facilities temporarily taken out of service for cleaning, inspection, maintenance, painting,repair, or any other activity or event that might lead to contamination of water. This standard applies to treatment components, including filter basins, filter media, clearwells, pump suction wells, and associated piping and appurtenances located downstream from the filter influent or from the first point of application of disinfectant in the treatment process. The disinfection method employed is surface contact with a high-strength chlorine solution for a specific time period.

This standard defines the minimum requirements for the disinfection of water treatment plants, including facility preparation, application of chlorine to the interior surfaces of water treatment units, and sampling and testing for the presence of total coliform bacteria.The absence of total coliform bacteria in addition to the use of proper disinfection practices is confirmation that the disinfection process has been accomplished in compliance with the standard.

Major changes in this revision include the following additions:

1) A note to the user on the effect of pH and temperature on the disinfection process, as well as a note on consideration of alternative disinfectants.
2) Definitions for available chlorine, free chlorine, chlorine residual, contractor, liquid chlorine, and purchaser
3) A requirement for compliance with the Safe Drinking Water Act
4) Additional clarification and guidance on water treatment plant components requiring disinfection
5) A reference to ANSI/AWWA B301 for Liquid Chlorine and ANSI/AWWA B300 for Hypochlorites
6) An advisory note on using appropriate personal protective equipment when handling chlorine products
7) An advisory note on perchlorate formation in hypochlorites
8) Reference to ANSI/AWWA C655 for field dechlorination practices
9) An advisory note on testing a disinfected facility not immediately returned to service

Also, Appendix A on Disposal of Heavily Chlorinated Water has been removed.This information is now covered in more detail in ANSI/AWWA C655, Field Dechlorination.