RU2663039C2 - Method for optimizing chlorammonization of drinking water - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention can be used in water supply systems of settlements to prolong the bactericidal action of chlorine and reduce the amount of chlorinated by-products. For implementation of the method, the water is mixed with free chlorine in the first stage, followed by the introduction of a coagulant for 0.5–1.5 minutes and the total concentration of free and bound chlorine to 1.2 mg/dm. At the second stage, ammoniation is carried out with the calculated optimum amount of ammonium sulfate to total chlorine equal to or close to the mass ratio of 1.26:1.0. With multiple increase in the chlorine absorptivity of the treated water, the bound chlorine is adjusted by free chlorine to the MPC standards, and control and management of the purification process is carried out at all stages of the process.EFFECT: method ensures reduction of bacteriological contamination of water treatment facilities, an increase in the degree of water purification with simultaneous improvement of technical and economic indicators.3 cl

Description

The invention relates to methods for water purification, mainly to the field of disinfecting natural surface waters with chlorine-containing compounds for household and drinking purposes and can be used in water supply systems of settlements for prolonging the bactericidal action of chlorine and reducing the number of chlorination by-products.

Chlorination disinfection of drinking water is often used as the most economical and effective method. Apply single or double chlorination of water. Primary chlorination is carried out with the aim of preliminary disinfection and maintenance of water treatment facilities in good sanitary condition, as well as improving the coagulation process. Secondary chlorination in order to prolong the bactericidal action of chlorine during water transportation.

In the process of chlorination of water, chlorine compounds react with natural organic substances (POV). Natural amino acids (PAA) - the most extensive and reactive class of natural compounds that make up water colloids with negatively charged polar groups such as R-NH ₂ , R-OH, R-COOH , etc., which through hydrogen bonds hold a large number of water molecules in the form of hydrated shells and stabilize dispersed impurities. In the reaction of chlorine compounds with side groups of PAA, at the first limiting and transient stage, they are replaced by chlorine with the formation of oxo compounds, inactivation of microorganisms that are difficult to disinfect, located inside and on the surface of molecules, and the destruction of odorizing substances. Chlorinated amino acids decompose quickly, their fragments lose their hydration shells, are easily precipitated, and with pathogenic microorganisms can be removed from water during filtration with preliminary sedimentation.

At the second stage, chlorination of oxo compounds occurs with the formation of a trichloromethyl and chloroacetic group. The process takes time to several hours and depends on the amount of chlorine supplied and the content of total organic carbon.

The main products resulting from the disinfection of natural water with chlorine are trihalogenomethanes (THMs) and haloacetic acids (HFAs).

According to the World Health Organization (WHO), both of these classes of organochlorine compounds (ChOS) have comparable carcinogenic properties, toxic, mutagenic effects and high bio-permeability. In Russia, the control of the formation of COS is carried out by the content of four compounds from the TGM group: trichloromethane (chloroform), bromoform, dibromochloromethane, dibromodichloromethane (SanPiN 2.1.4.1074-01. "Drinking water. Hygienic requirements for the quality of water in centralized drinking water supply systems. Quality control" Moscow: Ministry of Health of Russia, 2002). The main by-product of water chlorination at water treatment plants in Russia is chloroform, the maximum permissible concentration (MPC) is 0.06 mg / dm ³ .

In order to reduce the concentration of THM formed during chlorination, as well as prolonging the action of chlorine, the method of chlorammonization is known and widely used. Translation with the help of ammonium compounds of active chlorine ( Cl ₂ , HOCl and OCl ^- ) into its hardly hydrolyzed form - monochloramine ( NH ₂ Cl ). Chlorammonization is carried out by introducing ammonia or ammonium salts into the treated water, and is carried out before primary or secondary chlorination.

However, chlorammonization significantly reduces the effectiveness of water disinfection. Compared with monochloramine, chlorine at a pH of ≤7 is 200, 20, 50, and 2.5 times more active in the inactivation of bacteria, viruses, spores, and cysts, respectively. That is why in most European countries chloramines are not used in primary disinfection. But due to the duration of their action, they are used for secondary disinfection (Technical reference for water treatment. - M .: Degremon, 2005. S. 1111-1113).

The technology of disinfecting drinking water using chlorammonization has become widely used at water treatment plants abroad and in Russia, as evidenced by many publications in the technical literature. Vodokanals share the experience of introducing chlorammonization technology: Moscow, Yaroslavl, St. Petersburg, Rostov-on-Don, Izhevsk, Kazan, Anapa, Sevastopol, Kemerovo, Yekaterinburg, Tyumen and other cities (Arutyunova I.Yu., Kalashnikova O.B. The use of the method of preliminary ammonization and chlorination in the preparation of Moskvoretsky water // Water supply and sanitary equipment. Moscow, 2012, No. 10; Troshkova EA, Zhukova V.Ya., Alekseev SE. Application of ammonium sulfate in the water treatment system of the Metelevka water treatment facilities Tyumen // Water supply and sanitation rnaya equipment. Moscow. 2014, №6, etc.).

However, in the well-known works, the doses of ammonium for chlorammonization are experimentally selected in laboratory and production conditions and at the same time unacceptable amounts of reagents are expended, for example: doses of ammonium to chlorine are selected in the intervals of 1: 5 ÷ 15 or more. In these intervals, when the ammonium ion is exhausted due to an excess of chlorine ion, the processes can be described by the following ion-molecular reaction equations:

In any of the considered areas, the system is in a nonequilibrium state and, in short periods of time, the equilibrium of reactions (1-5) can shift both left and right, the accuracy of determination of ammonium and chlorine compounds decreases, which significantly reduces the ability to control and control the process.

The guide is based on a literature review, surveys of US companies working in the field of natural water purification using chlorammonization, and research conducted in laboratory and industrial conditions (Gregory J. Kirmeyer, Mark Le Chevallier, Helene Baribeau, Kathy Martel, Gretchen Thompson , Lori Radder, Wyndi Klement, and Andrea Flores, Optimizing Chloramine Treatment. 2 ed. 2004: Awwa R Fand AWWA) describes a technology optimization strategy that describes practical approaches to selecting reagent doses to eliminate water nitrification, process control of chlorammonization, and monitoring g water quality for residual chlorine and ammonium. It is proposed to include chlorammonization as one of the main elements of water treatment in the equipment of stations at the design stage.

However, in the manual, the values of the ratios of the amounts of chlorine and ammonium are not ordered and lie within wide limits.

In addition, in the well-known publications, the pre-ammonization methods are considered as the most promising (they are carried out by introducing ammonium into the treated water before chlorination). However, to ensure comparable efficacy of bound and free chlorine, it is necessary to increase the concentration of bound chlorine by an order of magnitude or more. Thus, if the technology does not use other methods of disinfection of water, then the use of chloramines alone is associated with the risk of the development of harmful microorganisms in the treated water.

In addition, under the conditions of pre-ammonization, a deficiency of active chlorine arises, surfactants are destroyed only partially, and their increased content in water can cause the appearance of extraneous odors and lead to a deterioration of the settling and filtering processes. An additional unproductive consumption of the coagulant is required, which leads to secondary contamination of the disinfected water and an unreasonable increase in the cost of the disinfection process.

The use of chlorammonization in secondary disinfection to reduce the concentration of TGM may also not provide the necessary degree of disinfection against viruses and other microorganisms, since the interaction of chlorine with water after primary chlorination occurs throughout the water treatment process and to reduce the concentration of TGM, it is necessary to significantly reduce the dose of chlorine at the primary stage chlorination.

In addition, there are difficulties in optimizing control over the chlorammonization process and in the automatic analysis mode. So in the works of M.M. Platonova, G.A. Kochelaeva. Optimization of the process of chlorammonization of drinking water // Water supply and sanitary equipment. Moscow. 2015, No. 7 and V. B. Malkov. The choice of technological control strategy as the basis for an effective process of chlorammonization of drinking water // New affordable technologies for water supply and water treatment. Moscow. 2016, No. 4 describes aspects of this problem. The publications discuss the ratio of chlorine to nitrogen in the areas of: Cl: N <5: 1; Cl: N> 5: 1; Cl: N> 9 . However, in the region of Cl: N ratios <5: 1 , nitrification of water can occur, in the regions of Cl: N ratios > 5: 1 ; Cl: N> 9 the final reaction products are the result of a complex chain of successive transformations. In this case, Cl ⁺ with a valency of +1 can be converted into chloride with a valency of -1, passing the stage with zero valency, and in this state its loss for instrument determination is possible. Nitrogen trichloride can also make a significant contribution to this loss, since it has pronounced hydrophobic properties and a certain time is required for its reliable determination.

US Pat. No. 6,315,950 B1 describes a method for controlling chlorination of wastewater and chlorammonization of drinking water. The process is controlled in the range of the mass ratio of chlorine to ammonia nitrogen of ~ 5: 1 and is based on the spectroscopic method of analysis of samples. Another complex and multi-stage method for controlling the chlorammonization process is described in US patent No. US6881583 B2, where the required amount of monochloramine is maintained due to minimal deviations in the concentrations of ammonia and dichlorammin. A disadvantage of the known methods is the low effect of preventing the formation of THM due to the difficulty in regulating the supply of reagents, due to the high reaction rate of the interaction of ammonia with a chlorine-containing reagent, and fixing the moment of slip. In addition, automatic analysis of ammonia depends on the properties of the source water (temperature, metal ions, etc.) and requires constant adjustment of the sensors according to the results of laboratory tests.

US 7332076 B2 describes a method for disinfecting water using several simultaneous disinfectants, including the preparation of ammonia water, its subsequent mixing with purified water and previously prepared chlorine water in a separate reactor and then in a mixer of structures. The process of chloramonization is carried out with an excess of active chlorine (the weight ratio of chlorine to ammonia is approximately 3.5: 1 to 4.5: 1) to obtain dichlorammine and monochloramine. However, as was previously shown, in comparison with chloramines, chlorine is more active in the inactivation of microorganisms, and in fact, when describing the method, one of the pre-ammonization methods with the simultaneous presence of free and bound chlorine in water with all the ensuing consequences is considered.

In addition, in the listed publications and in the indicated patents, the control and management of the chlorammonization process is calculated by the following molar ratio: Cl ₂ : N or NH ₄ ⁺ or NH ₃ = 1: 1, which corresponds to a mass ratio of ~ 5: 1. However, it is known that the main part of Cl ₂ is hydrolyzed during the preparation of chlorine water (they do not directly dose chlorine gas into the purified water), then the calculation must be carried out using the main components - HOCl and OCl ^- , which is also confirmed by the authors of the publications. Hydrolysis of Cl ₂ can be described as follows: ion-molecule reaction equation:

The reaction between the hypochlorite - ion and the ammonium ion is reversible and proceeds quickly compared to the formation of chloramine. The formation of monochloramine from ammonia and hypochlorous acid can be described by the following ion-molecular reaction equation:

и при мольном соотношении HOCl:NH ₃ =1:1 их массовое соотношение соответственно составит: ~3,1:1; а не 5:1.

and with a molar ratio of HOCl: NH ₃ = 1: 1, their mass ratio, respectively, will be: ~ 3.1: 1; not 5: 1.

CN 1583591 B2 describes a method for disinfecting water in two stages, first with free chlorine for 5 to 30 minutes, and then ammonia is added to the water. The process of chlorammonization is carried out with an excess of active chlorine (the weight ratio of chlorine to ammonia is approximately 4 ÷ 5: 1).

The disadvantage of this method is that it does not prevent the formation of THM at times of high chlorine absorption of the treated water, due to the need to use high doses of chorus in the first stage. The use of the doses indicated in the method with high chlorine absorption of water will not allow reaching the MPC for bound chlorine at the outlet of the treatment plant. In addition, very low process control and management capabilities.

The patent CN 102659266 B describes a method of disinfecting water in two stages - at the first multi-point injection of free chlorine in the course of water purification at facilities with the calculation of the dose of chlorine at the end point as the sum of doses at intermediate points, taking into account the chlorine absorption of water. At the second stage, ammonia of chlorinated water is carried out in front of the tank with pure water (RCH) ammonia, the ratio of which to chlorine is selected experimentally in laboratory and production conditions and according to the test results is ~ 1: 3 ÷ 5, the closest to the essence of the alleged invention.

The first stage of this method is widely known as fractional chlorination, and is used for high chlorine absorption of water to reduce TGM. The calculated dose of chlorine is not administered immediately, but in small portions: partly before the structures of the first stage of water treatment (mixers, sumps), partly before the filters, while the contact time of chlorine with water is long and the concentration of TGM in drinking water can be reduced only by 15-30% . Ammonization in the second stage of disinfection is carried out after chlorination to prolong the bactericidal action of chlorine.

The disadvantages of this method are: a low effect of preventing the formation of TGM due to the cumulative accumulation of TGM during a long period of water purification during construction and the complexity of process control.

The technical task of the invention is to develop such a method of chloramonization of natural waters, in which it is stably and reliably achieved: preventing the formation of TGMs above the MPC, eliminating chloramines with a high degree of oxidation and nitrification, reducing by-products of chlorination and the degree of secondary pollution of treated water, respectively, improving its quality and prolongation of the bactericidal action of chlorine while improving the technical and economic indicators of purification by reducing unproductive reagent costs and simplified process control.

The technical result of the invention is a predictable and well-controlled process of chlorammonization with the prevention of the formation of TGM to MPC standards, with the exception of chloramines with a high degree of oxidation and nitrification of the treated water, a reduction in bacteriological and hydrobiological contamination of water treatment facilities and water supply networks and, accordingly, an increase in the degree of water purification while improving the technical and economic indicators.

The technical result is achieved by the fact that in the method of optimizing chlorammonization of drinking water, including primary chlorination of water with free chlorine in the first stage, in the second stage, ammonization of chlorinated water, while the chlorination of water with free chlorine in the first stage is carried out sequentially by mixing free chlorine with purified water, then mixing the resulting chlorine compounds with purified water and a coagulant solution with a total chlorination time of 0.5-1.5 minutes at the first stage. and the total concentration of free and bound chlorine up to 1.2 mg / dm ^3, then in a second step, the concentration of total chlorine and chlorinated water are ammoniation for obtaining monochloramine stoichiometrically necessary quantity of ammonium sulfate to a specific total chlorine in water, wherein the calculation of ammonium sulfate are for a commercial product and the mass ratio of ammonium sulfate to total chlorine is considered equal to or close to 1.26: 1.0; then the amount of total chlorine is determined in the pipeline after the settling tanks and filters and, at a concentration below the maximum concentration limit, the concentration of free and bound chlorine is adjusted at the first and second stages, and with a multiple increase in the chlorine absorption of the treated water in the pipeline, the concentration of bound chlorine is determined after the settling tanks and filters and, when if necessary, in the pipeline after the filters, it is additionally corrected with free chlorine to the MPC norms for total chlorine, followed by ammonization of chlorine ovannoy water stoichiometrically necessary quantity of ammonium sulfate to certain free chlorine in water, wherein the calculation of ammonium sulfate are at commercial product and the weight ratio of ammonium sulfate to free chlorine is considered at or near 1.26: 1.0; the monitoring and control of the process of formation of monochloramine is carried out in relation to the total ammonium defined in water to bound chlorine, the amount of monochloramine is maintained due to minimal deviations from the molar ratio of nitrogen to chlorine, which in monochloramine is 1: 2.54.

Distinctive features of the invention: the sequence of mixing at the first stage of disinfection of water with reagents and processing time; reagent control and stoichiometric calculation of the optimal amount of reagents, process adjustment with increasing chlorine absorption, process control and management.

At the first stage, water is chlorinated in two stages, at the first - mixing of free chlorine (prepared chlorine water) with purified water, at the second - mixing of the obtained chlorine compounds with purified water and a coagulant solution. In the process of chlorination, free chlorine reacts with the functional groups of the side chains of natural amino acids and other organic and inorganic compounds. Chlorine present in water in the form of compounds with the indicated substances separately from free is considered as bound chlorine. At the same time, the destruction and destruction of chlorinated organic compounds, including chloramines, occurs.

Mixing in the second stage allows increasing the reaction rate of oxidation and decomposition of organic impurities, as well as reducing the amount of bound chlorine by 15-20% in comparison with the simultaneous mixing of free chlorine with coagulant in one device. This is due to a decrease in the competing processes of primary and secondary adsorption of hydrated shells of amino acids with a coagulant (there is no “collapse” effect of molecules), which improves coagulation conditions at subsequent stages of water treatment.

The dose of chlorine in the first stage is determined taking into account the quality and chlorine absorption of the source water. In this case, the total concentration of free and bound chlorine after mixing in the first and second stages of the first stage should be in the range of ~ 1.2 mg / dm ³ .

Since at the first stage, the interaction of chlorine with natural amino acids and other organic compounds lasts a short period of time (0.5-1.5 min), a low concentration of THM and HAC is formed in water, since the formation of trichloromethyl and chloroacetic groups is stretched during chlorination time from a few minutes to several hours.

At the second stage, the concentration of total chlorine is determined in order to calculate the optimum amount of ammonium sulfate to obtain monochloramine, the exclusion of chloramines with a high degree of oxidation or nitrification of the treated water. The bound chlorine obtained in the first stage is not taken into account, since most organic compounds, including chloramines in the α-position from the carboxyl group, are unstable (half-life from several minutes to several hours), decompose to aldehydes, passing through structures in water treatment process, and cannot lead to nitrification of the purified water.

Ammonization of chlorinated water to produce monochloramine is carried out stoichiometrically with the required amount of ammonium sulfate to the total chlorine detected in water (calculation is carried out for the main chlorine compounds HOCl and OCl ^- ).

The ratio of the stoichiometric flow rates of hypochlorous acid and ammonium sulfate can be described by the following molecular reaction equation:

and with a molar ratio of HOCl: (NH ₄ ) ₂ SO ₄ = 1: 1, the mass ratio of ammonium sulfate in the marketable product to total chlorine, respectively, will be: 1.26: 1.

Ammonization is carried out with minimal deviations from the mass ratio of ammonium sulfate in the marketable product to the total chlorine determined in water.

With a multiple increase in the chlorine absorption of purified water in the pipeline after sedimentation tanks and filters, the concentration of bound chlorine is determined and, if necessary, in the pipeline after filters, it is additionally adjusted with free chlorine to the MPC standards for total chlorine, followed by ammonization of chlorinated water with the stoichiometrically necessary amount of ammonium sulfate to the free water defined in water chlorine, while the calculation of ammonium sulfate is based on the commercial product and the mass ratio of sulfate o ammonium to free chlorine is considered equal to or close to 1.26: 1.0.

Monitoring and control of the chlorammonization process is based on the fact that all bound chlorine is in water in the form of monochloramine, and the molar ratio of nitrogen to chlorine in monochloramine is 1: 2.54. The control is carried out in relation to the ratio of total ammonia defined in water to bound chlorine and the ratio of total ammonium to bound chlorine is considered equal or close to 1: 2.54; they also control the concentrations of free, bound and total chlorine, ammonium sulfate.

Monitoring the concentration of free, total and bound chlorine, adjusting it taking into account the quality of the water supplied to the treatment during the water treatment process, as well as calculating the doses of ammonium sulfate, allows the chlorammonization process to be carried out with a predictable and well reproducible result - preventing nitrification of the treated water and the formation of TGMs above normal MPC, and accordingly increase the degree of water purification while improving the technical and economic indicators of the process.

Tests to implement the proposed method were carried out from 2014 at the pumping and filtering station (NSF) of the municipal unitary enterprise of the city of Novosibirsk "Gorvodokanal" No. 1 with a capacity of ~ 250 thousand m ³ / day, lasting from April to October.

The main characteristics of the source river water during the tests varied within the following ranges: temperature from 1 to 22 ° C, turbidity from 2 to 60 mg / dm ³ , color from 8 to 30, chlorine absorption from 2 to 3 mg / dm ³ (in some short periods up to 11 mg / dm ³ ), ammonium from 0.1 to 0.3 mg / dm ³ , a hydrogen index (pH) from 7.5 to 8.5.

Doses of reagents depending on the season and characteristics of river water varied within: coagulant from 4 mg / dm ³ to 50 mg / dm ³ , flocculant from 0.05 mg / dm ³ to 0.1 mg / dm ³ , chlorine before mixers from 1.6 to 3.1 mg / dm ³ . The dose of ammonium sulfate was determined depending on the concentration of total chlorine found in water.

During long pilot studies, the optimal conditions for chlorammonization of drinking water were established:

- mixing of free chlorine at the first stage in two successive mixers (for example, devices for fast mixing of reagents, RF patent No. 2455055) allows to increase the reaction rate of oxidation and decomposition of organic impurities, as well as reduce the amount of bound chlorine ~ by 15-20% in comparison with simultaneous mixing of free chlorine with a coagulant in one device;

- depending on the characteristics of river water, the doses of chlorine in front of the mixers can vary from 1.5 to 3.0 mg / dm ^3, while the concentrations of chloroform, bromoform, dibromochloromethane, dibromodichloromethane vary slightly. So, for example, with an increase in the dose of chlorine in front of the mixers from 1.8 to 3.0 mg / dm ^{3, the} concentration of chloroform increases from ~ 25 to ~ 35 μg / dm ³ (MPC - 60 μg / dm ³ ). This indicates an optimally selected chlorination time at the first stage (0.5-1.5 min).

- with a multiple increase in chlorine absorption of the purified water, chloramonization is carried out in two stages. In the pipeline after the filters, additional adjustment is made with free chlorine to the MPC norms for total chlorine, followed by ammonization of the chlorinated water with the stoichiometrically necessary amount of ammonium sulfate to the free chlorine defined in the water.

- the dose of ammonium sulfate depends on the concentration of total chlorine determined in water, which at the control points before ammonization should be ~ 0.8 ÷ 1.2 mg / dm ³ , is supplied within the minimum deviations from the stoichiometrically required amount for the commercial product and the mass ratio of sulfate ammonium to free chlorine 1.26 ÷ 1.30: 1.0.

- bound chlorine obtained before ammonization in the first stage is not taken into account in calculating the dose of ammonium sulfate;

- Ammonization of chlorinated water is carried out with a 1-2% solution of ammonium sulfate in terms of a commercial product to eliminate errors in terms of nitrogen or NH ₄ ⁺ ion in the preparation and dosing of solutions.

- monitoring and control of the chlorammonization process is carried out on the basis that all bound chlorine is in water in the form of monochloramine and the ratio of total ammonium to bound chlorine is considered equal or close - 1: 2.54. According to the results of the analysis of water at control points, the technology is simply adjusted and allows you to accurately control the content of residual bound chlorine in the treated water.

Tests for the implementation of the proposed method showed that, compared with the previously existing chlorammonization technology at the secondary disinfection of water, a guaranteed effect of reducing the concentration of THM within the MPC norms in drinking water was obtained, according to microbiological and hydrobiological indicators, the water meets the regulatory requirements. Application of the developed technology allows minimizing the cost of maximizing the efficiency and reliability of the station.

A guide has been developed to monitor and control the technology of disinfecting drinking water with chlorammonization, taking into account the stoichiometric calculation of the starting and obtained compounds.

In 2016, the chlorammonization method was introduced in the full cycle of reagent purification in the entire volume of purified water of NSF No. 1 and NSF No. 5, respectively, with a capacity of ~ 250 thousand m ³ / day and 450 thousand m ³ / day.

Claims (3)

1. A method for optimizing chlorammonization of drinking water, including primary chlorination of water with free chlorine in the first stage, at the second stage ammonization of chlorinated water, characterized in that the chlorination of water with free chlorine in the first stage is carried out sequentially by mixing free chlorine with purified water, then mixing the resulting chlorine compounds with purified water and a coagulant solution with a total chlorination time in the first stage of 0.5-1.5 min and a total concentration of free and bound chlorine up to 1.2 mg / dm ³ , then in the second the stage determines the concentration of total chlorine and the ammonization of chlorinated water is carried out to obtain monochloramine stoichiometrically the required amount of ammonium sulfate to the total chlorine defined in the water, while the calculation of ammonium sulfate is carried out by the marketable product and the mass ratio of ammonium sulfate to total chlorine is considered equal to or close to 1.26: 1.0; then in the pipeline after sedimentation tanks and filters the amount of total chlorine is determined and, when its concentration is below the maximum permissible, the concentration of free and bound chlorine is adjusted at the first and second stages. 2. The method according to p. 1, characterized in that with a multiple increase in chlorine absorption of the treated water in the pipeline after sedimentation tanks and filters, the amount of bound chlorine is determined and, if necessary, in the pipeline after filters, it is additionally adjusted with free chlorine to the norms of maximum permissible concentration of total chlorine with subsequent ammonization of chlorinated water with the stoichiometrically necessary amount of ammonium sulfate to the free chlorine defined in the water, while the calculation of ammonium sulfate They are led by the marketable product and consider the mass ratio of ammonium sulfate to free chlorine equal to or close to 1.26: 1.0. 3. The method according to any one of paragraphs. 1, 2, characterized in that the monitoring and control of the process of formation of monochloramine is carried out in relation to the total ammonium defined in water to bound chlorine, the amount of monochloramine is maintained due to minimal deviations from the molar ratio of nitrogen to chlorine, which in monochloramine is 1: 2.54.