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The aim of this paper is to discuss disinfection in water treatment using chlorination. Disinfection in watertreatment means to purify water from pathogens like viruses and bacteria. Water purification is done so as to produce water fit for a specific use. Water may be purified for drinking, pharmacology, medical or industrial application. Chlorine is one of the most used disinfectants. Its applicability and effectiveness in deactivation of pathogenic microorganisms. Chlorine destroys viruses and bacteria by breaking the chemical bonds of their molecules. Water Chlorination is the act of adding chlorine to water in order to purify it. Chlorine reacts with water to form Hypochlorous acid and Hydrochloric acid. Hypochlorousaciddissociates to hydrogen and hypochlorite ions which oxidize the water while actively killing harmful micro-organisms (Hellferich 1).
Disinfection by chlorination has some problems associated with it in some condition. Chlorine may react with some organic compounds in water to form compounds known as disinfection byproduct (DBPs). Examples of DBPs are trithalomethanes (THMs)and haloacentic acids (HAAs). Other problems include the volatile nature of Chlorine which causes it to disappear too fast from water. Chlorine also leads to the change of taste and odor of the water. DBPs pose health risks when present in drinking water.
The main challenge associated with the use of chlorine as a disinfectant forced water disinfectant organizations to control the feed rate of chlorine into water or even encouraging the use alternatives like use of chlorine compounds to disinfect water instead of the chemical itself (Nora and Diallo 2).
Feed rate controls encourage low capacity supply of chlorine passing through the proportioning pumps. Therefore, the controlled and constant head arrangement is used to supply the chlorine solution. Most of the times, a clocking device is incorporated in the pumps to control the interval at which the solution is supplied to the system. However, the type and complexity of a control system to be used is determined by the size of the water treatment facility. Complex and automated control system with recorders are used at large facilities. Signals from a chlorine residual analyzer are used to adjust the feed rate and also to maintain a present constant chlorine residual level.
One of the compounds used in disinfection of water is Hypochlorite compounds; this compound is easily portable than chlorine whose transportation, storageand handling procedure remain hazardous. The hypochlorite compounds being safer to store handle and transport is used.
Another alternative is Chloramination. Chloramination is the addition of ammonia which formscombined chlorine residual. This has been used to control certain taste and odor,growth of algae and bacteria. It is used due to its ability to maintain disinfectant residual for longer than free chlorine.
Furthermore, Chlorine dioxide is preferred to chlorine due to its ability to act faster than the elemental chlorine. Chlorine dioxide I supplied in a solution form and added to water to avoid gas handling problem. Another alternative to using chlorine is the use of ozone. Ozone molecule when added to water gives up one atom of oxygen to water which is toxic to waterborne organisms. Ozone produces less dangerous by products as compared to chlorination. However, it leaves no disinfectant in water. The last alternative to using chlorine is application of hydrogen peroxide. Hydrogen peroxide oxidizes the water which is toxic to waterborne organisms. The disadvantages being that it is slow working and decrease ph in water.
Chlorination as a method of water disinfection has many advantage and has some disadvantages. The advantages being that it is very effective and very applicable. Disadvantages being the formation of DBPs and the volatility of chlorine making it disappear fast from water. With the right controls however, it is arguably the best method of water disinfection.