Chlorine:Removing Contaminates from Water MaddisonPierce Mrs.WhiteChemistry111December22, 2017 Toquote Lyle Hurd, “What a paradox, that water, the essential nutrient, the exlirof life, contains potentially toxic elements that could jeopardize the immunesystem, leaving us vulnerable to organ damage and deadly disease.” Chlorine hasdisinfected drinking water for over a hundred years (Huange, pp.1401).
It wasintroduced to create an essentially, “safer” and “healthier”, water for us todrink. It is now used every day in our drinking water to help preventepidemics. As water is the most abundant compound in the human body (Hurd, 42)it is extremely important to find ways to keep it both clean and safe for thepublic to drink. Chlorine is said to be one of the strongest advances indisinfectant history. There are many uses for chlorine and chlorination wasexperimented with in many different ways before it was decided that chlorine gasbe used to treat the water and before the chlorine dioxide that is used inpools was discovered.
Chlorine was supposedly discoveredin the thirteenth century, but was first created into a pure substance by CarlWilhelm Scheele in 1774. Scheele heated brown stone (manganese dioxide; MnO2)with hydrochloric acid (HCl). When these substances are heated the bonds arebroken, causing manganese chloride (MnCl2), water (H2O)and chlorine gas (Cl2) to form (Lenntech, Water Treatment Solutions). Chlorine gas was first introduced as amethod to clean drinking, or potable, water in 1903 in Middlekerke, Belgium. But, before then, it had only been used asa cleaning solution and a sort of precaution in places such as hospitals—as atype of ‘industrial soap’.
It was only thought to be put into drinking waterafter it was discovered that micro-organisms caused the majority of diseases. Chlorine was first used in the U.S. as a majordisinfectant in 1908 in Jersey City, New Jersey (Centers for Disease Controland Prevention, 1), specifically at the Boonton reserve. By the late1920s, the chlorination of drinking water was said to have virtually eliminated all waterborne epidemics anddiseases from the U.
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S. and LIFE magazine recently cited the filtrationof drinking water and use of chlorine as “probably the most significantpublic health advance of the millennium.” Chlorinationhas freed civilization from the constant dangers of waterborne epidemics thatonce inflicted suffering, disease and premature death (Hurd, 42). The worldcan credit the chlorination of drinking water with the responsibility for alarge part of the 50 % increase in life expectancy (Bengston, 2).
As a primarydisinfectant, chlorine is applied to disinfect and to control microbialactivity in the distribution system (EPA, Water Treatable Database). Now,Chlorine is even added to the public water supplies to kill disease-causingmicrobes (Keiley, 68). Chlorine plays an important role in medical science.
Itis not only used as a disinfectant, but it is also a constituent of variousmedicines. The majority of our medicine contains chlorine or are developedusing chlorine-containing byproducts (Lenntech, Water Treatment Solutions).Even pain relievers such as Acetaminophen or inantibiotics such as Vancomycin.Chlorine is added to the water inpublic water reserves, giving those with access to the public or ‘city water’the chlorinated water. Those with a well or private water supply have thechoice to add in their own chlorine, although this process can be dangerous ifnot done correctly with aqueous chlorine, as chlorine gas is toxic. People on private wells don’t enjoy thebenefit of having someone else monitoring contaminant levels in their water sothey must be diligent about testing it themselves and maintaining their wells(Keiley, 68). It is a long and difficult process for most as extra steps andprecautions must be followed.
Although in public water supplies,the chlorine is always added in its gas form, its solution/liquid form (NaOCl)is considered a better choice for private consumers, because when small amounts of chlorine are breathed in evenduring short time periods, this can affect the respiration system (Lenntech). “Purechlorine is very toxic, even small amounts can be deadly. During World War Ichlorine gas was used on a large scale to hurt or kill enemy soldiers”(Lenntech).Chlorine is available as compressedelemental gas, sodium hypochlorite solution (NaOCl) or solid calciumhypochlorite (Ca(OCl)2). All forms of chlorine, when applied towater, form hypochlorous acid (HOCl). Gaseous chlorine acidifies the water andreduces the alkalinity, whereas the liquid and solid forms of chlorine increasethe pH and the alkalinity at the application point (EPA).
Chlorine can be addedfor disinfection to drinking water in several different ways. When ordinarychlorination is applied, the chlorine is simply added to the water and no priortreatment is necessary. Pre- and post-chlorination is adding chlorine towater prior to and after other treatment steps. Rechlorination means theaddition of chlorine to treated water in one or more points of the distributionsystem in order to preserve disinfection (Lenntech). There is no preferredmethod out of the three, as they all do, essentially, the same thing, althoughsome consumers pre- and post-chlorination as it is the most thorough cleaningprocess.
Chlorine can also be dangerous inthe sense that it can form extremely reactive and toxic products (such ashydrogen chloride—HCl). As mentioned above when hydrogen chloride dissolvesin water it becomes hydrochloric acid. These ions react with any kind ofsubstance they come in contact with, even metals that are corrosion resistantunder normal circumstances. Concentrated hydrochloric acid can even corrodestainless steel. This is why it is stored either in glass or in plastic(Lenntech) and cannot be dealt with directly, or by consumers.
And althoughdangerous, Chlorine is used to kill bacteria—or used in our medicines asdiscussed above—for the same reasons. When chlorine reacts with organicsubstances, it often takes less than a minute to kill off the bacteria ofeveryday use (for example with E. Coli) which is faster than some syntheticallyprepared disinfectants.
It can even kill Hepatitis A in only 16 minutes, leadingconsumers to believe that it was the ‘all-powerful cleaner’. AlthoughChlorine had been the principle disinfectant of community water supplies forseveral decades (National, 4) and it was already such a big and proclaimed improvementin the water treatment industry, scientists still searched for a stronger andmore cost effective solution to treat drinking water. This led them to the useof chlorine dioxide, an easier to control cleaner. The switch from chlorine tothe even more powerful chlorine dioxide was an easy decision; Chlorine dioxidewas a stronger disinfectant, thus requiring a lesser concentrate (less of theelement needed also helped reduce costs for the government). This newalternative could also be used for the control of iron, manganese, and tasteand odor causing compounds (Volk, 323-324).
In fact, it was such an improvementthat the U.S. Government took a mere 14 days for the switch between chlorineand chlorine dioxide. Yet, not everyone was happy oreducated enough to appreciate the switch.
Chlorine dioxide has an intensegreenish yellow color with a distinctive odor (Gordon, 204). Due to this slightchange, the general public was concerned with the change in water treatment.Consumers had complaints of taste, odor, and (or) water discoloration (Volk,p.324). Most governments had to switch back to chlorine for the main-streamdrinking water treatment, but continued to use chlorine dioxide in pools likewe continue to do now, as it can battle stronger bacteria’s such as feces. In conclusion, chlorine is a powerful and useful elementin the disinfectant world.
For the past hundred years, it has protected us fromcertain-death epidemics and acted as a booster to keep our bodies in tip-topshape. From the use of the general public to private homes, the chlorination ofwater has become a large part of our lives. And although the change to chlorinedioxide was unsuccessful, it continues to clean our pools. Rick Hind, the legislative director at Greenpeace USA, once called Chlorine “the replaceable chemical” and yet the world would not be where we are today, inthe sense of clean and drinkable water, without it. Works CitedBengtson, Harlan. “The History of Water Chlorination- A Major Public Health Advance.
” Brighthub Engineering,13 July 2010, p.1-13 www.brighthubengineering.
com/structural-engineering/77511-water-chlorination-history-the-mid-1800s-through-the-early-1900s/Centers for Disease Control and Prevention.”Drinking Water.” Centers for DiseaseControl and Prevention, 22 June 2015, p.1-2, www.cdc.gov/healthywater/drinking/public/chlorine-disinfection.html.
Environmental Protection Agency, United States.”Water Treatability Database.” EPA,Environmental Protection Agency, 5 Feb. 2007, p.
1-2, https://iaspub.epa.gov/tdb/pages/treatment/treatmentOverview.
do?treatmentProcessId=-1118142891Gordon, Gilbert, Aaron A.Rosenblatt. “Chlorine Dioxide: The Current State of the Art.” Ozone: Science& Engineering, vol.
27, no. 3, 2005, pp. 203–207.
http://web.b.ebscohost.com/ehost/detail/detail?vid=7&sid=42457c10-5039-4ef9-aa51-fbbba486aa1e%40sessionmgr101&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#AN=17781549&db=aqhHuang, Miao, and Yiping Hang. “Ion Chromatography for Rapid andSensitive Determination of Total Chlorine in Water.” Analytical Letters, vol. 45, no.
11, 15 July 2012, pp. 1401–1411. http://web.b.
ebscohost.com/ehost/detail/detail?vid=9&sid=42457c10-5039-4ef9-aa51fbbba486aa1e%40sessionmgr101&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#AN=78301219&db=aqhHurd, Lyle. “Water: The Essential Nutrient.
” Total Health, vol. 25, no. 4, Aug. 2003,pp. 42–43., http://web.a.ebscohost.
com/ehost/detail/detail?vid=7&sid=6657adb0-0394-4fc7-a9a6-0e9e663899a0%40sessionmgr4010&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=hxh&AN=10992820Keiley, Lynn. “Safe Drinking Water.” Mother Earth News, no. 198, June/July2003, p. 65. http://web.b.ebscohost.
com/ehost/detail/detail?vid=14&sid=42457c10-5039-4ef9-aa51-fbbba486aa1e%40sessionmgr101&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#AN=9730745&db=rchLenntech. “Disinfectants—Chlorine” WaterTreatment Solutions. Lenntech Water Treatment & Purification, www.lenntech.com/processes/disinfection/chemical/disinfectants-chlorine.htm.
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1980, www.ncbi.nlm.nih.gov/books/NBK234591/Volk, C J, et al. “Implementationof chlorine dioxide disinfection: Effects of the treatment change on drinkingwater quality in a full-Scale distribution system.
” Journal of Environmental Engineering and Science, vol. 1, no. 5,Sept. 2002, pp. 323–330.
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