From Big Medical Encyclopedia

CHLORINATION of DRINKING WATER — a way of disinfecting of water the chemicals containing chlorine.

Russia began to apply chlorination of water since 1908, and it became the most widespread way of disinfecting of drinking water. It is explained by its reliability, profitability and a possibility of use in various conditions of water supply. For X. items of century use gaseous chlorine (see), the dioxides of chlorine or reagents containing chlorine in an active form, possessing oxidizing and bactericidal action. Other hypochlorites, chloroamines belong to similar reagents lime chloride (see), (see). Possess bactericidal action formed in water at hydrolysis of chlorine or chlorine-containing reagents hypochloric to - that (HOC1) and in a little smaller measure hypochlorite ion

(OC1+). The sum of C12 + HOC1 +

call OS1-in water free active chlorine; the chlorine which is in water in the form of chloroamines — the connected active chlorine. The mechanism of bactericidal action hypochloric to - you consist that, getting into a bacterial cell, it oxidizes SH groups of enzymes, inhibits them, breaks a metabolism and processes of reproduction. Oxidation potential and bacterial action increase among: chloroamines —> hypochlorites —» chlorine —» dioxide of chlorine. At chlorination water is reliably disinfected, being exempted from causative agents of intestinal and viral infections, tularemias, a brucellosis, leptospirosis.

A number of ways X is developed. item of century: usual chlorination on chlorsweat-rebnosti, double chlorination, rechlorination, chlorination with with a preammonization, chlorination by «postcritical» doses of chlorine, chloramine tablets (see Pantocidum), etc. For specific conditions choose an optimum way X. item of century. Most often apply usual chlorination of the water on chlorine requirement calculated by amount of active chlorine (in miles-grams), 1 l of water, necessary for disinfecting. As natural waters differ on mineral composition, pH, the maintenance of microorganisms, suspended matters, organic and other impurity, and chlorrequirement at them different. Chlorrequirement is determined by trial chlorination of water by different doses of chlorine or chlorine-containing reagent. The reliable bactericidal effect is reached if after 30 — 60 min. chlorination in water there are 0,3 — 0,5 mg/l of free active chlorine or 0,8 — 1,2 mg/l of the connected active chlorine. The Viruli-tsidny effect is reached by exposure of 60 min. in the presence of not less than 0,5 mg/l of free active chlorine. Excess of residual chlorine gives to water a chloric smell.

Existence in water of suspended particles, humic and other organic impurity reduces bactericidal effect of chlorine. For reliable disinfecting muddy and color waters are recommended to be clarified and decoloured previously, and to add chlorine to water after filtering. If water is strongly contaminated, then it is possible to apply double chlorination, adding chlorine to the untreated water in the beginning, and then after filtering. Chlorination with a preammonization is applied when at usual chlorination water gets unpleasant (pharmaceutical) began to smell also smack. Rechlorination (hyper chlorination) — processing of water by 5 — 20 times high doses, than at usual chlorination. It is applied to reliable disinfecting of the water dangerous in epidemiol. from-shenii, and also muddy and strongly contaminated by organic matters (see Disinfecting of water). After such disinfecting water needs to be dechlorinated (see Dechlorination of water), i.e. to delete from it excess of chlorine.

On water supply systems gaseous chlorine is added to a flow of the disinfected water by means of the special dosing devices called by chlorinators. On small (e.g., settlement or rural) water supply systems water is disinfected by

1 — 1,5% solution of lime chloride, to-ry also dose by means of special installations. At chlorination of a certain water volume (in a flank, a tank) add the corresponding amount of water solution of chlorine-containing reagent to it (e.g., lime chloride), mix water and leave for disinfecting in the summer not less than for 30 min., in cold season — not less than on 1 hour

San. control of X. the item of century on a water supply system consists in hourly determination of content of residual chlorine in the water coming to a water supply system (there have to be not less than 0,3 mg/l of free or

0,8 mg/l of the connected active chlorine). At least once a day select test of water for bacterial. researches. At the same time no more than 3 colibacilli in 1 l at total quantity of bacteria are admissible detection no more than 100 in 1 ml of a decontaminated water.

Bibliography: G. P. marks and But

centuries Yu. V. Modern methods of cleaning and disinfecting of drinking water, M., 1976; Kulsky JI. A. Theoretical bases and technology of conditioning of water, Kiev, 1983; The Guide to hygiene of water supply, under the editorship of S. N. Cherkinsky, M., 1975; Sergeyev E. P., Elakhovskaya N. P. and Skvortsov A. F. Hygienic value of transformation of chemicals with formation of chloroform in the course of disinfecting of drinking waters, the Gigabyte. and dignity., No. 6, page 56, 1981.

R. D. Gabovich.