Advantages And Disadvantages Of Chlorine

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Chlorine, whether in the form of pure chlorine gas from a cylinder, sodium hypochlorite or calcium hypochlorite, dissolves in water to form hypochlorous acid (HOCl) and hypochlorite ion (OCl–). Hypochlorous acid is a weak acid which undergoes partial dissociation to produce a hydrogen ion (H+) and a hypochlorite ion (OCl–): The total concentration of chlorine, hypochlorous acid and hypochlorite ions is referred to as the free available chlorine. If ammonia is present in the raw water, the hypochlorous acid can react to produce chloramines. The total concentration of the chloramines and any organic nitrogen chlorine-containing compounds is referred to as the combined available chlorine. Combined available chlorine is a less powerful disinfectant…show more content…
Storage may take the form of a small covered reservoir, providing sufficient head to supply more than one property, or may be a suitably positioned storage tank (e.g. in the roof space of the property), from which water flows under gravity to the taps. The tank or reservoir should hold a volume sufficient to accommodate the peak demand and the maximum period of interruption of supply. The storage tank, and other parts of the water supply system, may be contaminated during construction and should therefore be disinfected before use. This may be achieved by filling the system with a strong (20 mg/l) solution of chlorine and leaving to stand for several hours, preferably overnight. The chlorine solution should be drained off and the system rinsed thoroughly using treated water. The tank must be fitted with a lockable, well-fitting (but not airtight) lid to exclude light and pollutants. It is especially important to guard against the ingress of insects and animals and all openings must be protected using a fine mesh screen. The storage tank must be inspected regularly; at least annually and preferably every six months. If necessary, any accumulated silt can be flushed or siphoned out and the system disinfected as described

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