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Chlorine in Drinking-Water

Categories: ChemistryWater

Chlorine is added to drinking water, as a disinfectant, to get rid of harmful bacteria, which are usually present in areas from where the water is obtained. The controversy of this issue is that chlorination can work as an advantage or as a disadvantage to those consuming it. Chlorine is currently the most effective water treatment when compared with other alternatives. However, it also reacts with natural organic compounds present in the water to produce harmful chemicals that on a long-term basis are very dangerous.

The most well known adverse effects of contaminated water is shown in the Walkerton crisis in May 2000, where an outbreak of E. Coli contamination occurred in the water system of Walkerton, Ontario. Seven people died, and a further 2300 fell ill after consuming water that was contaminated by farm manure (Walkerton Report, CBC 2008). This could have been prevented if proper chlorination had taken place. Examples of contaminants that chlorine eliminates are microbes such as E. Coli, Salmonella typhi and Shigella.

E. Coli grows when the water is contaminated with human and animal waste products. Upon consuming E. Coli contaminated water, an individual suffers from diarrhea, cramps, nausea, renal failure and sometimes even death. Consuming water contaminated with Salmonella typhi causes typhoid fever. Shigella causes severe abdominal cramping with blood and mucus in the stool. Chlorine’s major advantage is that the water remains disinfected until it reaches the point of consuming, unlike other disinfectants such as ozone or ultraviolet light.

Chlorine not only purifies water, it also prevents bacterial growth, nitrogenous contaminants and such from growing in water pipes and storage tanks.

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It also gets rid of odors, unpleasant taste and organisms known as nuisance organisms. Slime bacteria, iron and sulfate reducing bacteria give the water a very unpleasant look and smell. These bacteria do not cause disease but chlorination gets rid of these organisms. Not only is chlorine easy to use, it is also widely available and of low cost.

However, chlorine is also associated with producing harmful byproducts as it reacts with chemicals already present in water. These products are known as disinfection by-products. They include chloroform and are known as trihalomethanes or THMs for short. Studies conducted have shown that tested animals that are exposed to high amounts of THM are at a much greater risk for cancer. Even with humans, long-term exposure to chlorination can greatly increase risks of cancer (LaPure Water Inc, 2000).

Also, chlorination does not get rid of all nitrate products. It only prevents the nitrates from reaching a toxic form. These nitrates are from manure products that have not been absorbed by plants. This is not particularly dangerous to adults, but with excess levels can cause “blue baby” disease (methemoglobinemia) in young infants (Nitrate: Health Effects in Drinking Water, McCasland). Chlorinated water also affects its taste and smell. Using chlorinated water to make coffee, tea, soups, etc changes its taste and smell.

Even with these disadvantages, it is evident that the benefits of chlorination outweigh the risks. With proper treatment – making sure that chlorine is not added in excess and proper water testing, drinking water would be much healthier. The only major disadvantage of chlorinated water is the long-term effects of THMs. It is known that using a carbon filter actually gets rid of THMs and other chlorination by-products. People should be made aware of this and encouraged to use carbon filters to filter the water out instead of consuming straight from the tap.

There are alternatives to chlorination as well, such as ozonation, which is a method of disinfection by adding ozone gas to water and applying an electric current. It is very effective against microbes and only forms by products, which can be removed with further treatment. Another method of disinfectant is by Ultraviolet light treatment. This method is effective against even more microbes than chlorine is but it is also costly. However, these methods can only be used as primary disinfectants, chlorine is required as a secondary disinfectant in order to disinfect water as much as possible.

Also, these methods are temporary – the water does not remain disinfected until it reaches point of being consumed. In conclusion, chlorination is the most effective method of disinfecting water from drinking purposes. It’s the only method that keeps the water clean from the point of treatment to the point of consuming it. It is also the only disinfectant that is capable of minimizing all possible health risks caused by contaminated water. The adverse effects of chlorine such as its harmful by-products can be eliminated or reduced with the use of carbon filters.

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Chlorine in Drinking-Water. (2018, Sep 18). Retrieved from

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