Water Treatment "Part 19": Chlorination of Drinking Water.
To destroy parasites, viruses, and other microorganisms in water that can be consumed, chlorine is added as part of the disinfection process. The disinfecting effect is effective well when the chlorine content in the water is between 0.1 and 0.2 mg/l and the contact period is higher than 30 minutes.
Despite the disinfection method with chlorine is successful, the molecules produced when chlorine reacts with the organic components in water resulting in harmful by-products known as trihalomethanes (THMs) are of particular concern. Nevertheless, chlorine is still employed in many water treatment plants around the world to disinfect drinking water.
Cylindrical bottles or stainless steel pressurised tanks are used to sell liquid chlorine. In a unique apparatus, chlorine gas is combined with a certain amount of water (1 g/L) to create chlorine water. Then, the chlorine water is added directly to the distribution network pipes, or to the filtered water tank.
In areas close to the treatment plant, an unpalatable odour and taste appear in drinking water when large amounts of chlorine are added during treatment, and when small quantities are added, the chlorine disappears from the network before it reaches the consumer, and this leads to biological pollution again. Therefore, the best option is to gradually add a certain amount of chlorine to the water at various locations along the distribution system.
After determining the critical point, the quantities of chlorine that must be added to the water are calculated. A graph may be generated by treating water samples with increasing quantities of chlorine. After two hours, the leftover chlorine is measured.
References:
- [Introduction to Water Chemistry (Pollution- Treatment- Analysis). Dr. Nasser Al-Hayek. Publication of the Higher Institute for Applied Sciences and Technology (HIAST). Syrian Arab Republic, 2017.]
- Taparhudee, Wara (2002). "Applications of Paddle Wheel Aerators and Diffused-Air System in Closed Cycle Shrimp Farm System" (PDF). Witthayasan Kasetsart (Sakha Witthayasat). 36: 408–419. Retrieved 26 April 2020.
- Unsafe water kills more people than war, Ban says on World Day". UN News. 22 March 2010. Retrieved 10 May 2018
- Raymond Desjardins- Livre: Le traitement des eaux- 2éme edition- Ecole Polytechnique de Montréal- 1997- ISBN 2-553-00643-8
- Drinking Water Treatment- EDX- Delft University of Technology.
- Book- Drinking Water: Principles and Practices- by Hans J C Van Dijk (Author), Jasper Q J C Verberk (Author), Peter J De Moel.
There are people who claim treating water through chlorination method can contaminate the water and cause adverse effect on the health
Certainly, when chlorine is added to water, harmful trihalomethanes compounds are formed, in addition to causing skin irritation, hair loss and gastrointestinal diseases if large amounts of it are added. Therefore, some countries have stopped using it in drinking water treatment plants, such as the Netherlands. But it remains very effective in eliminating microbes and viruses.
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