ABSTRACT
Many chemical alternatives exist for the disinfection of water and wastewater treatment facilities. Many events have contributed to a move away from the application of gaseous chlorine in water and wastewater treatment plants. Although chlorine dioxide was first produced in 1811, it was not until the middle 1960s when its widespread use occurred due to changes in the manufacturing process. The majority of utilities in the United States (US)transitioned from using gaseous chlorine to the bulk manufactured sodium hypochlorite. Other chemicals have been used to supplement or replace gaseous chlorine in some applications. The implementation of the Clean Air Act risk management plan for the storage of hazardous chemicals by the US Environmental Protection Agency (USEPA) and the reregistration of chlorine gas by USEPA office of pesticide programs as a pesticide have accelerated the use of liquid sodium hypochlorite in the water and wastewater treatment industry.
