A STUDY OF CALCIUM HYPOCHLORITE AS A DISINFECTANT OF WATER

Abstract

A number of different methods of water sterilization have been devised during the last decade or so, but few of them have proved to be commercial successes. The most successful method from a cost efficiency standpoint appears to be the hypochlorite process. Hypochlorites have long been recognized as powerful disinfectants, but it was not until the early nineties that the calcium and sodium compounds were used to any considerable extent as disinfectants of water. This method of sterilizati9n by hypochlo-rites, however, has been criticised considerably from time to time. It has been claimed that treatment with calcium hypochlorite or chlorid of lime, as it is commonly called, imparts a decided taste and odor of chlorin, and that the hypochlorite remains in the water for' a considerable time after application of the "bleach"; also that the hardness is increased; that there is considerable "after growth" of bacteria, and that this growth is objectionable in character. It was in order to obtain data in regard to these points of objection and because of frequent requests received by Dr. M. P. Ravenel, director of the State Hygienic Laboratory, for information in regard to the efficiency of calcium hypochlorite as a disinfectant of water that the experimental work, involving the treatment of waters of various qualities from different parts of the state, was undertaken. The-purpose of using disinfectants is to remove undesirable bacteria from the water, and it is obvious that any method combining the desirable qualities of efficiency and economy would prove of great value in the production of a safe water supply, either as a permanent method of disin-fection, or a temporary remedial method, or as an adjunct to filtration. The different substances which have been proposed for use as steriliing agents are heat, lime, ozone, permanganates, copper and its compounds, and chlorin and its compounds, the hypochlorites. Still other methods have been devised using hydrogen peroxide, barium peroxide, chlorin dioxide and bromin and chlorin together. These substances effect the necessary sterilization by the action of nascent oxygen, liberated in the presence of orgabic matter, and have produced very-good results; but, because of the expense involved, which is comparatively large, treatment of water with the above mentioned materials has not been extensive. HYPOCHLORITES. Hypochlorites have long been recognized as powerful and efficient dis-423