Term Papers on Swimming Pool Chemistry

Term Paper Title	Swimming Pool Chemistry
# of Words	858
# of Pages (250 words per page double spaced)	3.43

Swimming Pool Chemistry

            Most people still assume that swimming pools are just holes in the ground, filled with water. In reality, there are actually many chemical processes, which occurs in a swimming pool, to keep the water clean and safe. Pathogens such as adenoviruses, Hepatitis A viruses, Shigella and Escherichia coli 0157, which can cause fever, diarrhoea and vomiting, must be eradicated. [3] There are many other chemicals involved in balancing the water as well. [4]

            Chlorination is the practice of adding chlorine to pool water, to destroy disease-producing microorganisms and other contaminants. [2,4] All forms of chlorine ionise in water to form hypochlorous acid (HOCL). [1,2,4] The HOCL formed, retains the oxidising property of chlorine, and can kill microorganisms by  passing through their membranes and destroying their organelles. [1,4] However, HOCL further dissociates into hydrogen and hypochlorite ions, where the degree of dissociation depends on pH and temperature. [1,4] This makes pH control important, as hypochlorite ions are not as effective as HOCL in killing bacteria because of their negative charge. [1,4] At pH levels below six, HOCL dissociates poorly. [1,2,4] Then, between a pH of 6.0 and 8.5, there is a very sharp increase in the dissociation of HOCL to form hypochlorite ions. [1,2,4] However, acidic water is corrosive. [1,2,4] Hence, a pH level of 7.5 is perfect, having 50% of dissolved chlorine as HOCL. [4]

            Chlorine compounds, in a solid or liquid state, are added to the pool manually or by erosion feeders. [2,4] Elemental chlorine, a poisonous gas, requires special equipments though. [2,4] It is cheap but extremely acidic, requiring a lot of base to counteract it. [1,4] Using an electrolysis cell, HOCL can be generated continuously if salt is added. [1]

            Dissolved chlorine exists as “free available” chlorine if it has not bonded with another compound. [2,4] When it has combined with nitrogen compounds, creating chloramines, it loses its ability as a sanitizer. [1,2,4] This compound, which causes eye burn and strong chlorine smell in pools, is eliminated by superchlorination. [2,4] These compounds are now called combined chlorine. [4] Superchlorination is a process to oxidize and remove all ammonia compounds in a pool by raising the chlorine level. [2,4] A threshold called breakpoint chlorination is reached when chlorine levels are ten times the level of chloramines. [4] All dissolved chlorine exists as free available chlorine at this point because the additional chlorine oxidises chloramines to ...

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