WHY CHLORINATION OF WATER IS ESSENTIAL AND HOW IT MAY BE USED FOR REMOVAL OF BACTERIA PRESENT IN THE WATER

CHLORINATION OF WATER :--The requirements of chlorine depends upon the type of bacteria and the amount present in the water ,and can be determined by the orthotolidin  test .The provision of a reliable testing apparatus is very essential.The bacterial efficiency of chlorine is effected by the acidity or alkalinity of the water and it's temperature,which also effects the necessary contact period, frequent testing must be done at least six times a day .For disinfection alone a dosage of 0.1to 0.2 ppm may be required for good underground water and it will destroy most of the germs .In the case of highly polluted water the requirements of chlorine may be as 3 ppm giving a residual of 1ppm in 20 minutes .It is very effective against the bacteria commonly associated with water borne diseases and control of other plant life . Chlorine eliminates tastes and odours , improves coagulation,oxidises iron and manganese and removes colour. Chlorine contents if sufficient may kill all typhoid, cholera and gastroenteritis germs ,but flue ,colds and hepatitis germs are killed only by boiling the water .It may be given in three forms ,in case of very small supplies as bleaching powder or chloride of lime , for small town or village sodium hypochlorite solution containing 10 to 15 percent by weight of chlorine and the liquid form can be readily mixed with the water and in case of medium and large size of water works as chlorine gas by gaseous chlorinatior. Chlorine is easiest to apply in the form of a solution.