Page 16 - Curriculum Visions Dynamic Book

Chlorine as a disinfectant
Disinfecting is the process of killing bacteria
and microorganisms. Chlorine, often in the form of calcium chlorate powder, is an effective way of disinfecting water supplies, swimming pools and sewage systems.
The use of chlorine dates back to the last century, when most large cities had developed sewage systems that simply fed raw sewage
into rivers. The same rivers were also used for drinking water. Even in places where water
was obtained from wells, it was not safe to drink because of sewage seeping from nearby cess pits into the underground water supplies.
An infamous cholera epidemic occurred in London in 1848 that revolutionised the way people thought about disinfecting water supplies. Cholera caused over 25,000 deaths
in the following decade. Nothing could be done about it because of the lack of sewage treatment. The nearby River Thames received most of the raw sewage and produced a foul smell. In 1855, as a result of the research done into the epidemic and the smell (which proved to have the same cause), London became the first city in the world to have a sewage treatment system based on the use of chlorine.
The disinfectant properties of chlorine were also needed in hospitals. When surgeons began to disinfect their hands before each operation, the number of fatalities decreased rapidly.
The introduction of such disinfectants is closely connected with the efforts of the famous nurse Florence Nightingale.
Water supplies
Clean water supplies are essential for healthy living. The water entering a treatment plant contains chemical pollutants, small particles of solids, and biological material such as bacteria and algae.
The first stages of treatment involve filtering out the solid particles. The remaining chemicals are neutralised and precipitated. The water is then treated with chlorine, which is used as a disinfectant. Chlorine also oxidises any remaining organic materials.
 Swimming pools that get intensive use, such as at tropical resorts, often smell strongly of the chlorine that has been added as disinfectant. The chlorine can irritate sensitive tissues such as those in the nose and eyes.
16
16