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
             ...