In the U.S. - 1945. However, a lot of cities have naturally fluoridated water. In the U.S., there are a lot of news articles about adding fluoride to water. But for the rest of the world, too much fluoride in the water is a concern and there are lots of programs to remove it down to safe levels.
it was added in 1967
chlorine
Bacteria (usually) can be killed with ordinary soap or diluted cholrine bleach.
Chlorination.
All sorts of things are added to water, from whiskey to orange juice. If you mean added by the public water supply company, the common ones are chlorine to kill bacteria and fluoride to reduce tooth decay.
Most bleaches contain oxygen; drinking water contains oxygen and hydrogen.However, the element probably meant is chlorine, which is in the most common kind of household bleach (so is oxygen) and in polyvinylchloride, the material that makes PVC pipes. It's not really "used in" drinking water, though small quantities of chlorine compounds may be added to drinking water to "purify" it (really to sterilize it; chlorine is pretty toxic to microorganisms).
The gaseous element chlorine has a greenish tint. Chlorine bleach is an aqueous solution of sodium hypochlorite. Chlorine solutions are used to disinfect water in public water systems, and calcium hypochlorite powder is added to swimming pools to control bacteria.
ratio of chlorine to drinking water ?
chlorine is used every day, in everything from pools and our drinking water.
Chlorine is added to water to kill pathogens.
beacause chlorine is a chemical used to clean water
Tap water contains chlorine to ensure no bacteria in the available drinking water source. Chlorine is also used in pools for the same reason. The disadvantage of having chlorine in our drinking water is that if we use it to water plants, it does about as much harm as good. The same rule applies to drinking that same water, as chlorine in the stomach causes acid reflux and erosive esophigitis as the chlorine becomes chlorine gas and is unhealthy. The best thing you can do is filter tap water by way of a charcoal filtering system.
If too much chlorine is added Sulphurdioxide is used