Chlorine has been used in water purification for a very long time. For most of the 20th century chlorine contributed to improved water quality by dramatically reducing water-borne illnesses. The purifying agent - chlorine - has been responsible for the development of our present standard of living, because of the reduction of illnesses which caused better health and productivity. In countries where the water is not treated effectively the economic development of those countries has directly suffered. Sick people, stricken with stomach cramps and diarrhea, after consuming unsafe water, are not productive as they need to get well first.
However, many pathogens have become resistant to chlorine. Cryptosporidium is one such pathogen. Thanks to its size it can be filtered out with an adequately configured water filter.
Developments like these make the use of chlorine questionable, but it is still the most widely used water disinfection agent in the world. The main reason: it is the cheapest way to disinfect water. But, it also has strong residual disinfection capacity . This means that chlorine is used everywhere to keep the municipal water free from any re-contamination.
Tab water is sterilized with HCLO sodium chlorine. The first chlorine is added into the water at filtration plant, in order to disinfect the water and to eliminate organic chemicals, and then second addition of chlorine is completed so as to preserve its chlorine level in the water, prior to water supply to each household. It should be maintained to keep germs and virus away from the end user. (economically efficient in relation with its effectiveness)
Chlorine is a toxic chemical element of halogen family, which is used for production of oxidizer, bleaching agent, and sterilization-related goods. Chlorine in the tab water can also be reacted by a combination of organic elements to yield a combination of organic chlorine (i.e. environmental hormone) that harms our environment and health.