From Big Medical Encyclopedia

DISINFECTING OF WATER — ways of processing of water for ensuring its epidemic safety. There are reagentless (physical) and reagent (chemical) methods O. of century.

Efficiency of methods O. of century depends: from biol, properties of microbes, their resistance to the operating factor (e.g., causative agents of intestinal infections are, as a rule, less steady, than nonpathogenic colibacilli); from activity of the used factor, its dose and duration of action; from quality of the disinfected water, and, the more in water of the weighed and dissolved organic matters, the disinfecting effect is less reliable; from conditions of use of the disinfecting factor.

From reagent methods the method of chlorination is most widely applied (see. Chlorination of drinking water ). For chlorination use chlorine or its various connections, to-rye shall contain not less than 25 — 30% of active chlorine. Normal at O. the dose of chlorine, edge at time of contact with water is accepted by century not less than 30 min. provides the content of residual free chlorine in number of 0,3 — 0,5 mg/l. On epid, to indications when it is impossible to provide minimum (30 min.) contact, apply hyper chlorination of water — use the doses exceeding normal. Excess of residual chlorine is eliminated by dechlorination (see. Dechlorination of water ).

Ozonization of water (see) it is most widely used in France. In the USSR ozonization of water is applied in a number of the cities. Advantage of ozonization of water is that the possibility of complex processing of water is at the same time provided (disinfecting, decolouration and elimination of smells).

Long ago bactericidal oligodynamic action of ions of silver is known, however it did not find practical application on utility water supply systems, and is used only for conservation of a deposit of moisture on the sea and river fleet, by spaceships.

In rural settlements well water supply still is widely used. If quality of water in wells does not answer a dignity. to requirements, it is necessary to disinfect it in special tanks and chlorination of water directly in a well is only in exceptional cases allowed. More reliable effect is reached by use of the special porous ceramic boss filled by hypochlorite and suspended in a well. The hypochlorite which is dissolved in water passes through a wall of the boss and comes to water of a well. Change of hypochlorite in the boss is usually made in 1,5 — 2 months.

From reagentless methods O. of century in practical conditions only uv radiation is used. At use of this method formation of off-flavors and smacks of water is excluded, there are no difficulties with transportation and storage of reagents, contact tanks are not necessary. Disinfecting of drinking water ultraviolet rays is performed in special installations by impact on microorganisms of biologically active part of an ultraviolet spectrum (see. Ultraviolet radiation ). Sources of radiation are served by quartz lamps. Installations both with submersible, and with lamps, not submersible in water, can provide high bactericidal effect. However O. century ultraviolet rays has essential restrictions. According to technical specifications (productivity of one section apprx. 50 m 3 / hour) the method is applicable on water supply systems in small settlements with a small water discharge and for O. century of underground water sources if it is unreliable on a bacterial indicator, but is rather transparent and contains not enough iron.

Action ultrasound (see) explain with stress rupture of bacteria in the ultrasonic field. The bactericidal effect of ultrasound does not depend on a turbidity and color of water, and its action equally extends to vegetative and sporous forms of microorganisms.

The possibility of use for O. of century of gamma radiation is investigated (Co 60 ). This method has all advantages of reagentless methods of disinfecting and can be used for processing of large volumes of water, however the possibility of broad practical application of this method depends on further improvement of technology. The Lake of century

is important in field conditions.

DISINFECTING of WATER in field conditions

On large points of water supply of O. of century is made by the special divisions of engineering troops equipped with the appropriate technical means under control of medical service. The most widespread ways O. of century are boiling and chlorination.

Boiling is made on battalion food points in mobile kitchens and boilers, and also an individual way in kettles and other ware.

Boiling belongs to individual and group ways O. of century, the way is reliable, does not demand difficult hardware and special control methods of efficiency of disinfecting. At boiling along with death of microorganisms nek-ry thermolabile toxic agents collapse and easily flying are removed. At chlorination of water in field conditions use the normal and raised doses of chlorine (hyper chlorination). For carrying out chlorination carry out pilot chlorination by means of hydrochemical set, choose a dose and calculate amount of lime chloride, give it, dissolve in a small amount of water, bring at intensive hashing, wait for 30 min. and define residual chlorine. If the quantity it is within 0,3 — 0,5 mg/l, then allow use of water; if it is less than 0,3 mg/l, then carry out additional chlorination; if more than 1,5 — 2 mg/l — dechlorinate solution of hyposulphite or dilute with not chlorinated water with the subsequent endurance to 30 — 60 min. and definition of residual chlorine.

In the absence of hydrochemical set and necessary reactants chlorination is carried out by the elementary way. For this purpose 4 — 5 teaspoons of lime chloride pour out in a mug, flow a little water, pound, pour contents in a liter bottle, add water and shake up. The received solution of lime chloride is used for the choice of a dose and chlorination of water. The dose is chosen by pilot chlorination of the water poured in three buckets where consistently add depending on chromaticity and a turbidity of water 1,2, 4 or 3,6, 9 of teaspoons of the prepared solution of lime chloride mix and in 30 — 60 min. determine residual chlorine by a smell (water of that bucket where there is a slight smell of chlorine, is considered disinfected and suitable for drink). Having established by such way a necessary dose of lime chloride, calculate what number of 1% of its solution will be required on this or that water volume, intended for chlorination.

At chlorination by the raised doses bring obviously excess amount of chlorine providing reliable disinfecting and existence of a large amount of residual chlorine in water. Except reliability of disinfecting, this method allows to reduce time of contact of water with chlorine, not to carry out pilot chlorination for the choice of a dose, to disinfect the muddy and color waters containing organic matters and phenols. The last give to water at chlorination by usual doses off-flavor of an iodoform due to formation of mo-nokhlorfenol. At chlorination high doses form the poly-chlorphenols which do not have such smell.

The dose of chlorine is chosen depending on chromaticity and a turbidity of water, a dignity. reliability of a water source and epidemiol, dangers. Usually apply 15, 20, 25 mg/l of chlorine at time of contact of 15 — 20 min. then define residual chlorine and make dechlorination of water by filtering via coal filters or by means of sodium hyposulphite, to-ry bring at the rate of 3.5 mg on 1 mg of residual chlorine.

In case of impossibility of definition of active chlorine in lime chloride and residual chlorine in water (absence necessary a lab. the equipment and time) bring 120 g of dry lime chloride on 1 m3 of water that provides concentration of 30 mg/l of active chlorine. In 15 — 20 min. in the presence of a pungent smell of chlorine water is filtered via the coal filter or add hyposulphite in half quantity from the weight of lime chloride. In the absence of a pungent smell of chlorine add still half amount of lime chloride and in 10 — 15 min. determine residual chlorine by a smell again and then dechlorinate. Lime chloride is measured a teaspoon, edges level with edges are contained by 2.5 g of drug, and hyposulphite — the handle of a teaspoon, on a cut 0,7 g of drug are located.

In field conditions chlorination of water quite often combine it with coagulating. In these cases apply a method of standard doses. Bring in the conditioned water at first 50 mg/l of lime chloride (1 ml of 5% of solution), mix and add 100 mg/l of a coagulant, most often Al aluminum sulphate 2 (SO 4 ) 3 - 18H 2 O (1 ml of 10% of solution). Mix within 3 — 5 min. and in 15 — 20 min. filter via the fabric-coal filter (TUF-200).

In case of need destructions of sporous forms of microorganisms increase amount of active chlorine to 100 — 150 mg/l, and time of contact — till 1,5 — 2 o'clock.

In the absence of a container in field conditions chlorination of water directly in mine wells is allowed. For this purpose determine water volume in it and on each 1 m3 give (measure a teaspoon) depending on quality of water from 6 to 12 g of lime chloride, pound it with a small amount of water, pour in a bucket with water, stir and pour out in a well. Water in a well is carefully mixed a pole or a bucket and leave for contact with chlorine not less as on 1 — 2 hour. After this time water in a well shall have a slight smell of chlorine.

For disinfecting of an individual deposit of moisture (in flasks, in kettles, etc.) apply the tableted forms of drugs. Among them chlorine tablets (the mix of lime chloride with sodium chloride containing 2 — 3 mg of active chlorine), the tablets «Hypochlorite» (the mix of calcium hypochlorite with a carbonate or hydrosodium carbonate containing 3 mg of active chlorine), the tablets «Pantocidum» (the paradichlorsulfamidebenzoic are the most widespread to - that), Akvatsid, an effective agent to-rogo is monosodium salt dichlorisocyanuric to - you with the content of active chlorine to 4 mg. All of them are counted on chlorination of 1 flask (750 ml) of water on exposure within 30 min.

In some cases in field conditions O. by means of potassium permanganate or hydrogen peroxide is admissible century. To liter of transparent water add 3 drops of 3% of solution of hydrogen peroxide, to muddy water — 10 drops, and in strongly contaminated — 15 drops. At O. century by means of potassium permanganate on 1 liter of water add several crystals before receiving light pink coloring of solution.

See also Neutralization of water .

Bibliography: Marks G. P. and Novikov Yu. V. Modern methods of cleaning and disinfecting of drinking water, M., 1976; The Intensification of processes of disinfecting of water, under the editorship of L. A. Kul-sky, etc., Kiev, 1978, bibliogr.; The guide to hygiene of water supply, under the editorship of G. N. Cherkinsky, M., 1975; V. F Falcons. Disinfecting of water bactericidal beams, M., 1964; Chiang Sh. Water viral infections and their prevention, Bulletin WHO, t. 38, No. 3, page 398, 1968; Sh t and N of N and to about in E. V., etc. Hygienic aspects of design, construction and operation of group systems of agricultural water supply, Gigabyte. and dignity., No. 5, page 7, 1979.

In field conditions - Koshelev N. F., Logatkin M. N. and Mikhaylov V. P. Sanitary and hygienic control of food, water supply and accommodation of troops, page 272, L., 1977; ‘Krotkov F. G. Water supply of troops in a field situation, Voyen. - a dignity. business, No. 3, page 41, 1942; The General and military hygiene, under the editorship of N. F. Koshelev, page 168, JI., 1978; The Guide to hygiene of the water transport, under the editorship of E. P. Sergeyev, M., 1974; Elpiner L. I. Water supply of sea vessels, M., 1975.

S. N. Cherkineky, N. F. Koshelev.