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•Taking A New Look At Dry Chlorine

By James P. Brennan
Arch Chemicals Inc.

Many water and wastewater treatment facility managers are searching for an alternative to gas or liquid chlorine to further enhance the efficiency, reliability, safety and performance of their disinfection systems. They need to consider calcium hypochlorite briquettes.

Chlorination has long been the conventional method for disinfection of municipal water and wastewater, due to its low chemical cost and consistent performance. Chlorination is used for two basic purposes in public water and wastewater treatment: substantial reduction of pathogens in source water and discharge effluent, or maintenance of low bacterial counts in drinking water distribution systems.

Disinfection History
The initiation and growth of chlorine disinfection for water and wastewater applications in the United States occurred almost simultaneously. In 1908, Chicago and Jersey City became the first cities to treat drinking water with chlorine routinely. The first major city to install chlorination to disinfect wastewater, according to the EPA, was most likely Philadelphia, in 1910.

Four years later, the first set of standards was enacted requiring the use of disinfection for drinking water, prompting a substantial increase in the use of chlorine. In 1925, drinking water standards were further strengthened, reducing by half the maximum permissible limit of coliforms. These new standards, together with the enactment of strict new wastewater discharge requirements, quickly made chlorination the standard disinfection method in the U.S. for water and wastewater treatment.

At that time, gaseous chlorine, liquid chlorine, and so-called bleaching powder (generally chlorinated lime), were the primary disinfecting agents used, with calcium hypochlorite compounds beginning to appear on the market in 1927. About the time the compound loop principle of chlorinator control first began to be implemented in the early 1960s, most municipal water and wastewater systems had initiated gaseous chlorine use to meet new and evolving disinfection standards.

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Downloads:
•Taking A New Look At Dry Chlorine