Swimming Pool Chemistry essays

Free Essay Database Online

Swimming Pool Chemistry essays

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 bypassing 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