THE ADVANTAGES AND DIS ADVANATGES OF CHLORINE AS A DISINFECTANT IN WATER TREATMENT
Chlorine reactions depend on the type of chlorine added to the water (Water Treatment by Chlorine) as well as on the pH of the water itself. Each of the reactions uses up the chlorine in the water and produces either chloride ions or hydrochloric acid, which have no disinfecting properties. The total amount of chlorine which is used up in reactions with compounds and destroying pathogens in the water is known as the chlorine demand. A sufficient quantity of chlorine must be added to the water so that, after the chlorine demand is met, there is still some chlorine left as free residual chlorine to take care of any further contamination. Reactions of Chlorine with Water
When chlorine gas enters the water, the following reaction occurs:
The chlorine reacts with water and breaks down into hypochlorous acid and hydrochloric acid.
Chlorine + Water Hypochlorous Acid + Hydrochloric Acid
Cl2 + H2O –> HOCl + HCl
Hypochlorous acid may further break down, depending on pH:
Hypochlorous Acid Hydrogen Ion + Hypochlorite Ion
HOCI H+ + OCl-
The double-sided arrows in the equations mean that the reaction is reversible. Hypochlorous (HOCL) acid may break down into a hydrogen ion and a hypochlorite (OCL) ion, or a hydrogen ion and a hypochlorite ion may join together to form hypochlorous acid.Advantages and Disadvantages of Chlorine
Advantages of Chlorine as disinfectant are:
1. It can be easily stored for long time without any risks of it getting deteriorated.
2. It is highly soluble in water.
3. It is quite inexpensive compared with other chemicals, and easily available.
4. The chlorine dose to be added can be easily measured and controlled, and hence chances of overdosing or under-dosing are minimized.
5. It is a very powerful disinfectant, and may