Introduction

Natural water, as a rule, does not meet the hygienic requirements for drinking water, so before serving it to the population it is almost always necessary to purify and disinfect it. Natural water consumed by humans for drinking, as well as used in various industries, must be safe in sanitary and epidemiological terms, harmless in its chemical composition and have favorable organoleptic properties.

It is known that none of the modern methods of water treatment ensures its 100% purification from microorganisms. But even if the water treatment system could facilitate the absolute removal of all microorganisms from water, there is always a high probability of secondary contamination of purified water during its transportation through pipes, storage in containers, contact with atmospheric air, etc.

Sanitary rules and regulations (SanPiN) do not aim to bring water according to microbiological indicators to ideal, and therefore sterile quality, in which all microorganisms will be absent from it. The task is to remove the most dangerous of them for human health.

The main documents that define hygienic quality requirements drinking water, are: SanPiN 2.1.4.1074-01 “Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control" and SanPiN 2.1.4.1175-02 "Drinking water and water supply to populated areas. Hygienic requirements for water quality in non-centralized water supply. Sanitary protection of sources."

Currently, there are many known methods of water disinfection and many devices used for their implementation. The choice of disinfection method depends on many factors: source of water supply, biological characteristics of microorganisms, economic feasibility, etc.

The main objective of this publication is to provide basic information about modern methods disinfection of water for drinking purposes, brief description each method, its hardware design and the possibility of application in the practice of centralized and individual water supply.

It is important and necessary that every water user can correctly formulate goals and objectives when choosing a disinfection method and, ultimately, obtaining high-quality drinking water.

The publication provides initial information on the main sources of water use, their characteristics and data on the suitability of the source for drinking purposes, as well as regulatory documents regulating water and sanitary legislation, a comparative overview of regulatory documents regulating the quality of drinking water in terms of disinfection, adopted in Russia and abroad. abroad.

Water purification, including its decolorization and clarification, is the first stage in the preparation of drinking water, at which suspended substances, helminth eggs and a significant part of microorganisms are removed from it. However, some pathogenic bacteria and viruses penetrate wastewater treatment plants and are contained in filtered water.

In order to create a reliable barrier to the possible transmission of intestinal infections and other equally dangerous diseases through water, disinfection is used, that is, the destruction of pathogenic microorganisms - bacteria and viruses.

It is microbiological contamination of water that leads to the maximum risk to human health. It has been proven that the danger of diseases from pathogens present in water is thousands of times higher than when water is polluted with chemical compounds of various natures.

Based on the foregoing, we can conclude that it is disinfection to the extent that meets established hygienic standards that is a prerequisite for obtaining water for drinking needs.

1. Sources of water supply, their suitability for disinfection

All sources of water intake are divided into two large classes - groundwater and surface water. Underground include: artesian, under-river, spring. Surface waters are river, lake, sea and water from reservoirs.

In accordance with the requirements of the regulatory document GOST 2761-84, the choice of water supply source is made based on the following data:

for an underground source of water supply - analyzes of water quality, hydrogeological characteristics of the aquifer used, sanitary characteristics of the area in the area of ​​water intake, existing and potential sources of soil and aquifer pollution;

with a surface source of water supply - analyzes of water quality, hydrological data, minimum and average water flow rates, compliance with their intended water intake, sanitary characteristics of the basin, industrial development, the presence and possibility of sources of domestic, industrial and agricultural pollution in the area of ​​the proposed water intake. A characteristic feature of water from surface sources is the presence of a large water surface, which is in direct contact with the atmosphere and is under the influence of the radiant energy of the sun, which creates favorable conditions for the development of aquatic flora and fauna, the active course of self-purification processes.

However, the water of open reservoirs is subject to seasonal fluctuations in composition, contains various impurities - mineral and organic substances, as well as bacteria and viruses, and near large settlements and industrial enterprises there is a high probability of its contamination with various chemicals and microorganisms.

River water is characterized by high turbidity and color, the presence of a large amount of organic substances and bacteria, low salt content and hardness. The sanitary quality of river water is low due to its contamination with wastewater from residential settlements and cities.

Lake water and water from reservoirs are characterized by a low content of suspended particles, high color and permanganate oxidation; water blooms are often observed due to the development of algae. Lake water has varying degrees of mineralization. These waters are unsafe from an epidemiological point of view.

IN surface waters In flows, water self-purification processes occur due to physical, chemical and biological reactions. Under the influence of biochemical processes with the participation of protozoa aquatic organisms, antagonist microbes, and antibiotics of biological origin, pathogenic bacteria and viruses die.

Water cycle in the global natural cycle: 1 – world ocean; 2 – soil and groundwater; 3 – land surface waters; 4 – snow and ice; 5 – transpiration; 6 – river (surface) runoff; 7 – water in the atmosphere in the form of vapor and atmospheric moisture.

As a rule, self-purification processes do not provide the quality of water necessary for domestic and drinking needs, therefore all surface water is subjected to purification processes with mandatory subsequent disinfection.

Water from underground water intake sources has a number of advantages over surface water: protection from external influences and epidemiological safety.

Sea water contains a large amount of mineral salts. It is used in industrial water supply for cooling, and in the absence of fresh water, for the purpose of domestic and drinking water supply after desalination.

The use of water from underground water intake sources for water supply has a number of advantages over surface sources. The most important of them are protection from external influences and, as a result, safety in epidemiological terms.

Accumulation and movement groundwater depends on the structure of rocks, which in relation to water are divided into waterproof (waterproof) and water permeable. Waterproof materials include: granite, clay, limestone; permeable - sand, gravel, pebbles and fractured rocks.

According to the conditions of occurrence, groundwater is divided into soil, groundwater and interstratal.

Soil waters are located closest to the surface and are not protected by any waterproof layer. And as a result, the composition of soil water experiences strong fluctuations in composition both during short periods (rain, drought, etc.) and over the seasons, for example, snow melting. Since atmospheric water can easily enter soil water, the use of soil water for water supply requires a purification system and mandatory disinfection.

Groundwater is located below soil water, depth from two to several tens of meters; they accumulate on the first waterproof layer, but do not have a top waterproof layer. Water exchange can occur between groundwater and soil water, so the quality of soil water affects the condition of the groundwater. The composition of groundwater is subject to slight fluctuations and is virtually constant. In the process of filtering through a layer of soil, water is purified from mineral impurities and partially from bacteria and microorganisms. Groundwater is the most common source of water supply in rural areas.

Underbed water is water extracted from wells whose depth corresponds to the bottom marks of a stream, river or lake. Infiltration of river water into the ground layer may occur; these waters are also called underbed water. The composition of under-channel waters is subject to various fluctuations and is not very reliable in sanitary terms; and the use of these waters for the water supply system requires purification and disinfection.

A spring is a source of water that spontaneously flows to the surface. The presence of a spring indicates the presence in the depths of an aquiferous layer supporting an impermeable layer saturated with moisture. The quality and composition of spring water is determined by the groundwater that feeds it.

Interstratal waters are located between two waterproof rocks. The top waterproof layer protects these waters from penetrating atmospheric precipitation and groundwater. Due to its deep location, fluctuations in the composition of the water are insignificant; the waters are the most favorable in sanitary terms.

Contamination of interstratal waters occurs extremely rarely: only when the integrity of aquifer layers is damaged or in the absence of supervision of old wells that have been in operation for a long time.

Interstratal waters can have a natural outlet to the surface in the form of rising springs or springs - these waters are most suitable for a drinking water supply system.

It should be noted that there is no single composition of water, since even artesian water, lying at the same depth, enters our house, passing through various rocks, thereby changing its composition.

2. Classification of disinfection methods

In water treatment technology, there are many methods of water disinfection, which can be divided into two main classes - chemical and physical, as well as their combination.

In chemical methods, disinfection is achieved by introducing biologically active compounds into water.

With physical methods, water is treated with various physical influences.

Chemical or reagent methods of water disinfection include the introduction of strong oxidizing agents, which include chlorine, chlorine dioxide, ozone, iodine, sodium and calcium hypochlorite, hydrogen peroxide, and potassium permanganate. Of the above oxidants, practical application in water disinfection systems is found: chlorine, ozone, sodium hypochlorite, chlorine dioxide. Another chemical method is oligodynamy - exposure of water to ions of noble metals.

In the case of disinfecting drinking water using a chemical method, in order to achieve a lasting disinfecting effect, it is necessary to correctly determine the dose of the administered reagent and ensure a sufficient duration of its contact with water. In this case, the dose of the reagent is calculated, or a trial disinfection is carried out on a model solution/object.

The dose of the reagent is calculated in excess (residual chlorine), which guarantees the destruction of microorganisms, even those entering the water for some time after its disinfection, which ensures a prolonged effect.

Physical methods of disinfection:

– ultraviolet irradiation;

– thermal impact;

– ultrasonic influence;

– exposure to electric discharge.

With physical methods of water disinfection, it is necessary to supply a given amount of energy to a unit of its volume, defined as the product of the intensity of exposure (radiation power) and the contact time.

The effectiveness of water disinfection by chemical and physical methods largely depends on the properties of water, as well as on the biological characteristics of microorganisms, i.e. their resistance to these influences.

The choice of method and assessment of the economic feasibility of using a particular method of water disinfection is determined by the source of water supply, the composition of the water, the type of installed equipment of the water supply plant and its location (distance from consumers), the cost of reagents and disinfection equipment.

It is important to understand that none of the disinfection methods is universal or the best. Each method has its own advantages and disadvantages.

3. Regulatory and technical documents of water and sanitary legislation

Water consumed by people living in a wide variety of environments comes from many sources. These can be rivers, lakes, swamps, reservoirs, wells, artesian wells, etc. Accordingly, water obtained from sources of different origin differs in its qualities and properties.

There is a high probability that even water from sources located close to each other will vary dramatically in quality.

Industrial enterprises, sanatoriums, commercial companies, hospitals and other medical institutions, rural residents and residents of megacities - all have their own special requirements for water quality.

That is why water purification and disinfection are necessary when the quality of water does not meet consumer requirements.

Requirements for water quality and safety are established in the following main regulatory documents listed in table. 1.

Table 1

There are also technological standards and requirements related to the design of water treatment systems (Table 2).

table 2

Epidemic water safety is determined by total number microorganisms and the number of coliform bacteria. According to microbiological indicators, water must meet the requirements given in table. 3.

Table 3

*Indicative parameters of water quality. Only for monitoring purposes, EU Member States may establish additional parameters on their territory or part thereof, but their introduction should not worsen people’s health.

**Required parameters.

4. Treatment of water with strong oxidizing agents

Water disinfection using reagent methods is carried out by adding various chemical disinfectants to the water or by taking special measures. The use of chemicals in water treatment usually results in the formation of chemical by-products. However, the health risk from their exposure is negligible compared to the risk associated with harmful microorganisms developing in water due to the lack of disinfection or its poor quality.

The Ministry of Health has authorized the use of more than 200 products for disinfection and sterilization of water.

In this section, we will consider the main disinfectants used in Russian water supply systems.

4.1. Chlorination

Chlorine was discovered by the Swedish chemist Scheele in 1774. This year marks the beginning of the history of the use of reagents containing active chlorine (for more than two centuries). Almost immediately, its bleaching effect on plant fibers - flax and cotton - was discovered. Following this discovery in 1785, French chemist Claude Louis Berthollet used chlorine to bleach fabrics and paper on an industrial scale.

But only in the 19th century. It was discovered that “chlorine water” (as the result of the interaction of chlorine with water was called at that time) also has a disinfecting effect. It can be assumed that chlorine began to be used as a disinfectant in 1846, when in one of the hospitals in Vienna the practice of rinsing hands with “chlorine water” was introduced for doctors.

In 1888, at the International Hygiene Congress in Vienna, it was recognized that many infectious diseases can be spread through drinking water, including cholera, which was so dangerous and widespread at that time. In fact, this congress served as an impetus for finding the most effective way to disinfect water. The development of the topic of chlorination for the disinfection of drinking water is associated with the construction of water pipelines in large cities. It was first used for this purpose in New York in 1895. In Russia, chlorine was first used to disinfect drinking water at the beginning of the 20th century. In Petersburg.

Currently, the most common method of water disinfection is the use of chlorine and its compounds. More than 90% of water (the vast majority) is chlorinated. The technological simplicity of the chlorination process and the availability of reagents have ensured the widespread introduction of chlorination into water supply practice.

The most important advantage of this disinfection method is the ability to ensure the microbiological safety of water at any point in the distribution network, at any time, during its transportation to the user - precisely due to the aftereffect. After introducing a chlorinating agent into water, it retains its activity against microbes for a very long time, inhibiting their enzyme systems along the entire route of water through water supply networks from the water treatment facility (water intake) to each consumer.

Due to its oxidative properties and aftereffect, chlorination prevents the growth of algae, helps remove iron and manganese from water, destroys hydrogen sulfide, decolorizes water, maintains microbiological cleanliness of filters, etc.

4.2. Chlorination technique

When choosing a chlorination method (water treatment with chlorine or other chlorine agents), it is necessary to take into account the intended purpose of the chlorination process, the nature of the contaminants present in the water, and the peculiarities of fluctuations in the composition of the water depending on the season. Particular attention should be paid specific features technological scheme for water purification and equipment included in the treatment facilities.

According to their objectives, all methods can be divided into two large classes: primary (pre-chlorination, pre-chlorination) and final (final) chlorination.

Primary chlorination - the introduction of chlorine or chlorine-containing reagents into water is carried out as close as possible to the source of water intake. According to its purposes, primary chlorination serves not only to disinfect water, but also to intensify the processes of purifying water from impurities, for example, deferrization and coagulation. In this case, large doses of chlorine are used; the dechlorination stage, as a rule, is absent, since the excess amount of chlorine is completely removed at other stages of water purification.

Final or final chlorination is a process of water disinfection, carried out as the last stage of its preparation, i.e., all contaminants have already been removed and chlorine is used only for disinfection.

Chlorination is carried out both with small doses of chlorine - normal chlorination, and with increased doses - overchlorination.

Normal chlorination is used when drawing water from sanitary sources. Doses of chlorine should provide the necessary bactericidal effect without deteriorating the organoleptic indicators of water quality. The permissible amount of residual chlorine after 30 minutes of contact of water with chlorine is not higher than 0.5 mg/l.

Rechlorination used when drawing water from sources characterized by large fluctuations in composition, especially in microbiological indicators, and in the event that normal chlorination does not provide a stable bactericidal effect. Overchlorination is also used in the presence of phenols in water, when normal chlorination only leads to a deterioration in the organoleptic indicators of water quality. Rechlorination eliminates many unpleasant tastes and odors and in some cases can be used to remove toxic substances from water. The dose of residual chlorine during rechlorination is usually set in the range of 1–10 mg/l. Excess residual chlorine is then removed by dechlorinating the water; a small excess - aeration; a larger amount - by adding a reducing reagent - dechlor (sodium thiosulfate or sulfite, sodium disulfite, ammonia, sulfur dioxide, activated carbon).

Combined chlorination methods, that is, treating water with chlorine together with other bactericidal drugs is used to enhance the effect of chlorine or fix it in water for a longer period. Combined chlorination methods are usually used to treat large quantities of water in stationary water supply systems. Combined methods include: chlorination with manganization, silver chloride and copper chloride methods, as well as chlorination with ammoniation.

Despite the fact that chlorination is still the most common method of disinfection, this method also has some limitations in its use, for example:

– as a result of chlorination, organochlorine compounds (OCCs) can form in the treated water;

– traditional methods of chlorination in some cases are not a barrier to the penetration of a number of bacteria and viruses into water;

– water chlorination, carried out on a large scale, has caused the widespread proliferation of chlorine-resistant microorganisms;

– solutions of chlorine-containing reagents are corrosive, which sometimes causes rapid wear of equipment;

Combined chlorination methods, treating water with chlorine together with other bactericidal preparations, are used to enhance the effect of chlorine or fix it in water for a longer period.

In order to ensure public health, many countries have introduced government regulations limiting the content of COCs in drinking water. In Russia, 74 indicators are standardized, for example:

– chloroform – 0.2 mg/l;

– dichlorobromomethane – 0.03 mg/l;

– carbon tetrachloride – 0.006 mg/l.

Currently, maximum permissible concentrations for substances that are by-products of chlorination are set in various developed countries in the range from 0.06 to 0.2 mg/l, which corresponds to modern scientific data on the degree of their health hazard.

The process of formation of COCs is quite complex, extends over time up to several hours and depends on many factors: the dose of chlorine, the concentration of organic substances in water, contact time, temperature, pH value of water, alkalinity, etc. The main reason for the formation of COCs in water is the presence organic humic and fulvic acids, as well as algal metabolites. To eliminate these impurities, subsequent water purification with carbon filters is required. The most intensive formation of COCs occurs during pre-chlorination, when large doses of chlorine are supplied to untreated water containing a significant amount of organic substances. Currently, there are two main methods for preventing the formation of COCs: correction of the chlorination scheme and refusal to use chlorine as the main method of water disinfection.

When adjusting the chlorination scheme, the place where the main part of chlorine is introduced is moved to the end of the water treatment process flow, which will eliminate the need to supply large doses of chlorine to untreated water. When choosing this scheme, an important requirement is the removal of organic compounds (precursors for the formation of COCs) before introducing chlorine. Refusal of pre-chlorination and transfer of the supply of the main dose of chlorine to the end of treatment facilities is usually quite sufficient to solve the problem associated with the formation of chemical waste. However, this leads to a significant decrease in the efficiency of water disinfection and a decrease in the importance of treatment facilities as a barrier.

Chlorination of water is a reliable means of preventing the spread of epidemics, since most pathogenic bacteria (typhoid fever bacilli, tuberculosis and dysentery, cholera vibrios, polio and encephalitis viruses) are very unstable in chlorine.

It is appropriate to talk about the exclusion of chlorine during primary disinfection only if there are organic compounds in the water, which, when interacting with chlorine (and hypochlorite), form trihalomethanes, which negatively affect the human body.

To chlorinate water, substances such as chlorine itself (liquid or gaseous), sodium hypochlorite, chlorine dioxide and other chlorine-containing substances are used.

4.2.1. Chlorine

Chlorine is the most common substance used to disinfect drinking water. This is explained by its high efficiency, the simplicity of the technological equipment used, the low cost of the reagent used - liquid or gaseous chlorine - and the relative ease of maintenance.

Chlorine easily dissolves in water; after mixing gaseous chlorine with water, an equilibrium is established in an aqueous solution:

HClO H + + OCl -

The presence of hypochlorous acid in aqueous solutions of chlorine and the anions resulting from its dissociation OCl - have strong bactericidal properties. Hypochlorous acid is almost 300 times more active than hypochlorite ions ClO - . This is explained by the unique ability HClO penetrate bacteria through their membranes. Hypochlorous acid is susceptible to decomposition in light:

2HClO -> 2O + 2HCl -> O 2 + 2HCl

with the formation of hydrochloric acid and atomic oxygen as an intermediate substance, which is also a strong oxidizing agent.

Treatment of water with chlorine is carried out using so-called chlorinators, in which gaseous (evaporated) chlorine is absorbed by water. The resulting chlorinated water from the chlorinator is immediately supplied to the place of its consumption. Despite the fact that this method of water treatment is the most common, it also has a number of disadvantages. First of all, it is difficult to transport and store large volumes of liquid, highly toxic chlorine. With such an organization of the process, potentially dangerous stages are inevitably present - first of all, the unloading of containers with liquid chlorine and its evaporation to convert it into a working form.

The creation of working reserves of chlorine in warehouses poses a danger not only to the plant’s operating personnel, but also to residents of nearby houses. As an alternative to chlorination, in recent years, water treatment with sodium hypochlorite (NaClO) solution has been increasingly used; this method is used both at industrial water treatment plants and at small facilities, including private homes.

4.2.2. Chlorine dioxide

Chlorine dioxide is used for water disinfection in Europe, the USA and Russia. In the USA, in 1944, one of the first drinking water disinfection systems with chlorine dioxide was put into operation - the Niagara Falls system. In Germany, chlorine dioxide has been used since 1959. World experience in the use of chlorine dioxide and numerous studies have shown its effectiveness in the preparation and disinfection of drinking, industrial and waste water.

Main methods of producing chlorine dioxide

There are three main methods for producing chlorine dioxide:

– interaction of sodium chlorite with hydrochloric acid:

5NaClO 2 + 4HCl = 4ClO 2 + 5NaCl + 2H 2 O;

– interaction of sodium chlorite with molecular chlorine (sodium hypochlorite, hypochlorous acid). The reaction is carried out by introducing chlorine gas into a solution of sodium chlorite under vacuum conditions:

2NaClO 2 + Cl 2 = 2ClO 2 + 2NaCl;

– interaction of sodium chlorate with sulfuric acid and hydrogen peroxide:

2NaClO 3 + H 2 SO 4 + 2H 2 O = 2ClO 2 + 2O 2 + Na 2 SO 4

The effective action of ClO 2 is due not only to the high content of chlorine released during the reaction, but also to the atomic oxygen formed.

Currently, there are installations that use all these methods for producing chlorine dioxide for its further use in drinking water disinfection processes. The main factor preventing the widespread use of chlorine dioxide is its increased explosiveness, which complicates production, transportation and storage. Modern technologies have eliminated this disadvantage by producing chlorine dioxide directly at the point of use in the form of an aqueous solution of a safe concentration. The processes of obtaining and dosing chlorine dioxide into the treated water are fully automated; the presence of maintenance personnel is not required. In this regard, it can be used in installations with relatively low productivity.

The use of chlorine dioxide for water disinfection has a number of advantages:

– chlorine dioxide does not form trihalomethanes when interacting with organic substances, while helping to reduce the concentrations of iron and manganese in water;

– is an effective oxidizer and disinfectant for all types of microorganisms, including cysts (Giardia, Cryptosporidium), spore forms of bacteria and viruses;

– the disinfecting effect is practically independent of the pH of the water, while the effectiveness of chlorine decreases as the pH value deviates from pH=7.4;

– deodorizes water, destroys phenols – sources of unpleasant taste and odor;

– does not form bromates and organobromine by-products of disinfection in the presence of bromides.

The main disadvantage of using chlorine dioxide is the formation of by-products - chlorates and chlorites, the content of which in drinking water must be controlled. In accordance with SanPiN, the maximum permissible concentration of chlorites is 0.2 mg/dm 3 with a sanitary-toxicological limiting indicator corresponding to the third hazard class. These standards limit the maximum dose of dioxide for water disinfection.

4.2.3. Sodium hypochlorite

As an alternative, in recent years, water treatment with sodium hypochlorite (NaClO) solution has been increasingly used, and this reagent is used both at large water treatment plants and at small facilities, including private homes.

Aqueous solutions of sodium hypochlorite are prepared chemically:

Cl 2 + 2NaOH = NaClO + NaCl + H 2 O

or electrochemical method according to the reaction:

NaCl + H 2 O = NaClO + H 2.

The substance sodium hypochlorite (NaClO) in its pure chemical form (i.e., without water) is a colorless crystalline substance that easily decomposes into sodium chloride (table salt) and oxygen:

2NaClO = 2NaCl + O 2 .

When dissolved in water, sodium hypochlorite dissociates into ions:

Hypochlorite ion OCl - undergoes hydrolysis in water, forming hypochlorous acid HOCl:

ОCl - + H 2 O = HOCl + OH - .

It is the presence of hypochlorous acid in aqueous solutions of sodium hypochlorite that explains its strong disinfecting and bleaching properties. The highest bactericidal ability of hypochlorite is manifested in a neutral environment, when the concentrations of HClO and hypochlorite anions ClO are approximately equal.

The decomposition of hypochlorite is accompanied by the formation of a number of active particles, in particular, atomic oxygen, which has a high biocidal effect. The resulting particles take part in the destruction of microorganisms, interacting with biopolymers in their structure that are capable of oxidation. Research has established that this process is similar to that which occurs naturally in all higher organisms. Some human cells (neutrophils, hepatocytes, etc.) synthesize hypochlorous acid and accompanying highly active radicals to fight microorganisms and foreign substances.

Water disinfection and oxidation of impurities using electrochemically produced sodium hypochlorite was first used in the United States in the late 1930s. XX century... Sodium hypochlorite has a number of valuable properties. Its aqueous solutions do not have suspensions and therefore do not require settling, unlike bleach. The use of sodium hypochlorite for water treatment does not cause an increase in its hardness, since it does not contain calcium and magnesium salts like bleach or calcium hypochlorite.

The bactericidal effect of a NaClO solution obtained by electrolysis is higher than that of other disinfectants whose active principle is active chlorine. In addition, the solution has an even greater oxidizing effect than solutions prepared by the chemical method, since it contains more hypochlorous acid (HClO).

The disadvantage of this method is that aqueous solutions of sodium hypochlorite are unstable and decompose over time even at room temperature.

The industry of our country produces sodium hypochlorite in the form of aqueous solutions of various concentrations.

In accordance with GOST 11086-76, sodium hypochlorite solution, obtained by the chemical method, is available in three grades. Below are the indicators for the composition of the products.

Sodium hypochlorite in the form of a solution (grades A, B or “Belizna”) is a solution of hypochlorite (16–19% NaOCl) with an admixture of sodium chloride and hydroxide (pH 12–14). Both solutions decompose over time. The rate of decomposition depends on their storage conditions.

The reagent sodium hypochlorite solution is easily dosed, which allows you to automate the process of water disinfection.

4.2.4. Chlorine-containing reagents

The use of chlorine-containing reagents (bleach, sodium and calcium hypochlorites) for water disinfection is less dangerous in maintenance than the use of chlorine and does not require complex technological solutions. True, the reagent facilities used in this case are more cumbersome, which is associated with the need to store large quantities of drugs (3–5 times more than when using chlorine). The volume of transportation increases by the same amount.

During storage, partial decomposition of the reagents occurs with a decrease in chlorine content. In this regard, it is necessary to equip a forced-exhaust ventilation system and observe safety measures for operating personnel. Solutions of chlorine-containing reagents are corrosive and require equipment and pipelines made of stainless materials or with anti-corrosion coating; they are usually not used for individual water supply.

4.2.5. Chlorination for individual water supply

Installations for the production of active chlorine-containing reagents using electrochemical methods are becoming increasingly widespread, especially at small water treatment plants.

In Russia, several enterprises offer installations such as “Saner”, “Sanator”, “Chlorel-200” for the production of sodium hypochlorite using the diaphragm electrolysis of table salt.

The simplest and most common way to solve problems of water chlorination for individual water supply is by using sodium hypochlorite; the “Belizna” solution can be used as a reagent.

Many consumers do not like the fact that the water coming from the tap may smell of chlorine, but this problem is easily solved by installing a carbon filter.

Methods of water preparation by chlorination require precise dosing of reagents into the water being treated, since the reagents are highly chemically reactive. To solve chlorination problems, it is necessary to use modern digital technology, which ensures accurate dosing of the reagent in proportion to the flow rate or volume of water being treated.

There is a wide variety of dosing pumps on the market, differing in performance.

4.3. Other halogens for water disinfection

4.3.1. Iodization

Iodine is a chemical element from the group of halogens, the “relatives” of which are fluorine, chlorine and bromine, designated by the symbol I (from the Greek iodes - purple; Lat. Iodum), has a serial number of 53, atomic number - 126.90, solid density - 4, 94 g/cm 3, melting point – 113.5 °C, boiling point – 184.35 °C. In nature, iodine is mainly concentrated in sea ​​water(on average about 0.05 mg/l). In addition, it is also found in marine sediments. This allows it to pass into groundwater, where its content can reach more than 100 mg/l. Such a high iodine content is also typical for oil field areas. At the same time, its content in surface waters is low (concentration ranges from 1 to 0.01 μg/l).

Research shows that the iodization method is effective against bacteria and viruses and is not effective enough against microbial toxins and phenolic compounds. Another limitation on the spread of the iodization method is the appearance of a specific odor when iodine is dissolved in water. Therefore, iodization of water for the purpose of disinfection does not compete with traditional chlorination, despite the fact that iodine, unlike chlorine, has such advantages as inertness towards ammonia and its derivatives, as well as resistance to solar radiation. Treatment of water with iodine for disinfection purposes is not widespread, although attempts to iodize tap water have been made several times. Currently, water treatment with iodine is used only for low flow rates or in cases where special water disinfection schemes are used. Thus, in some cases, iodine is used to disinfect water in swimming pools.

Iodine is one of the microelements whose functions in the body are very diverse. It is involved in the synthesis of thyroid hormones and affects metabolic and regenerative processes. Insufficient presence of iodine in the body leads to negative consequences. However, not only a lack of iodine poses a danger to human health, but also its excess. Thus, an increased amount of iodine in the body leads to changes in the structural and functional characteristics of the thyroid gland, liver, and kidneys.

Not long ago, bottled iodized drinks and water appeared on the market. This approach is undoubtedly justified, since only the consumer himself, guided by medical indications, can decide whether he should drink iodized water or not.

In modern practice, for the disinfection of drinking water by iodization, it is proposed to use special ion exchangers saturated with iodine. As water passes through them, iodine is gradually washed out of the ion exchanger, passing through the water. This solution is only possible for small-sized individual installations in domestic water purification systems. In such systems, water iodization is carried out through the additional installation of a special filter element in one of the purification stages. Significant disadvantages are the change in iodine concentration during operation, the impossibility of precise dosing into running water and the lack of control of its concentration.

Geyser and Clean Water installations and cartridges are presented on the Russian market.

4.3.2. Bromination

Chemical methods of water disinfection also include those used at the beginning of the 20th century. disinfection with bromine compounds, which have more pronounced bactericidal properties than chlorine, but require more complex application technology.

Bromine is a chemical element from the group of halogens, designated by the symbol Br (from the Greek bromos - stench; the name is associated with the unpleasant odor of bromine; lat. Bromum) has a serial number of 35, atomic weight - 79.90, liquid density - 3.11 g/ cm 3, boiling point – 59.2 °C.

Bromine affects microorganisms, kills viruses, bacteria, fungi, helps remove organic impurities from water, and is effective in combating algae. Compounds based on bromine are resistant to solar radiation.

However, despite all its advantages, the water bromination method is very expensive, so it is not widely used in drinking water purification and is used mainly for disinfecting water in small pools and spas.

4.4. Ozonation

4.4.1. History of ozonation

In 1840, the German scientist Sheinbein, while studying the processes of decomposition of water into hydrogen and oxygen using an electric arc, obtained a new gas with a sharp, specific odor, which he called ozone. Then there were studies by other scientists to study the properties and uses of ozone. Inventor N. Tesla patented the first ozone generator in 1896.

For the first time, ozonation processes for water purification were implemented in France, where already in 1907 the first water ozonation plant was built in Bon Voyage (France) for the needs of the city of Nice, and in 1916 there were 26 ozonation plants in operation (total in Europe – 49).

IN Soviet time ozonation was implemented at the Eastern Waterworks in Moscow; the station was equipped with ozonizers from the French company Treily-gas.

4.4.2. Ozone production

Ozone (O 3) is a bluish or pale violet gas that spontaneously decomposes in air and in aqueous solution, turning into ordinary oxygen (O 2). The rate of ozone decay increases sharply in an alkaline environment and with increasing temperature. The dose of ozone depends on the purpose of the ozonated water. If we are talking about the disinfection of water that has previously been filtered and clarified, the dose of ozone is taken to be 1–3 mg/l, for underground water – 0.75–1 mg/l. When introducing ozone to decolorize and disinfect contaminated water, its required amount can reach up to 5 g/l. The duration of contact of disinfected water with ozone is 8–12 minutes.

Ozone is formed in many processes accompanied by the release of atomic oxygen, for example, during the decomposition of peroxides, oxidation of phosphorus, etc.

The most economical industrial method for producing ozone is to expose air or oxygen to an electrical discharge of 5000–25,000 V. The ozone generator consists of two plate or tubular (concentric arrangement) electrodes installed at a short distance from each other.

O 3 liquefies more easily than O 2, and therefore it is easy to separate them. Ozone for ozone therapy in medicine is obtained only from pure oxygen. When air is irradiated with hard ultraviolet radiation, ozone is formed. The same processes occur in the upper layers of the atmosphere, where the ozone layer is formed and maintained under the influence of solar radiation.

In the laboratory, ozone can be obtained by reacting cooled concentrated sulfuric acid with barium peroxide:

3H 2 SO 4 + 3BaO 2 = 3BaSO 4 + O 3 + 3H 2 O.

4.4.3. Disinfecting effect of ozone

When there is increased bacterial contamination of the water source or when it contains pathogenic microorganisms, enteroviruses and Giardia cysts that are resistant to traditional chlorination, ozone is especially effective. The mechanism of action of ozone on bacteria has not yet been fully elucidated, but this does not prevent its widespread use.

Ozone is a much stronger oxidizing agent than chlorine (at the doses of both reagents used).

In terms of speed, ozone is more effective than chlorine: disinfection occurs 15–20 times faster. Ozone has a destructive effect on spore forms of bacteria, 300–600 times stronger than chlorine. This is confirmed by comparing their oxidation potentials: for chlorine Cl 2 - 1.35 V, for ozone O 3 - 1.95 V.

The absence of chemicals in water that quickly react with ozone allows for effective destruction of E. coli at a dissolved ozone concentration of 0.01–0.04 mg/l.

To destroy polio bacteria (Le and Mv strains), it is necessary to expose water to chlorine for 1.5–3 hours at an oxidizing dose of 0.5–1 mg/l. At the same time, ozone destroys these bacteria in 2 minutes at a concentration in water of 0.05–0.45 mg/l.

It should be noted that ozone has such an important property as its antiviral effect. Enteroviruses, in particular those excreted from the human body, enter wastewater and, therefore, can often enter surface waters used for drinking water supplies.

The result of numerous studies has established: residual ozone in an amount of 0.4–1.0 mg/l, maintained for 4–6 minutes, ensures the destruction of pathogenic viruses, and in most cases such exposure is quite sufficient to eliminate all microbial contaminants.

Compared to the use of chlorine, which increases the toxicity of purified water, determined by hydrobionts, the use of ozone helps reduce toxicity.

4.4.4. Hardware design

Since ozone is a very toxic gas (maximum permissible concentration in the air of the zone is 0.0001 g/m 3), the schemes for water ozonation processes provide for its complete use and destruction. Ozonation equipment usually includes a special ozone degasser (destructor). All ozonation installations are assembled from corrosion-resistant materials, equipped with shut-off and signal valves, equipped with automatic start-up systems (timers, pressure switches, solenoid valves, etc.) and protection.

The water ozonation method is technically complex and the most expensive among other methods of drinking water disinfection. The technological process includes successive stages of air purification, its cooling and drying, ozone synthesis, mixing of the ozone-air mixture with the treated water, removal and destruction of the residual ozone-air mixture, and its release into the atmosphere. All this limits the use of this method in everyday life.

On the Russian market, household ozonizers are represented by the following models: “AquaMama”, “Ecotronika”, “Ozone Lux” (RUIQI, consists of an ozonizer and a carbon filter), etc.

Ozonation installations are represented by the following equipment: water ozonation stations of the CD-OWSG series, SOV-M series, PVO-TOG and PVO-ZF series, Ozon-PV, etc. The installations differ in design and performance.

4.4.5. Features of ozonation

From a hygienic point of view, ozonation is one of the best ways disinfection of drinking water. With a high degree of disinfection, it ensures its best organoleptic characteristics and the absence of highly toxic and carcinogenic products in purified water.

Ozone destroys known microorganisms 300–3000 times faster than any other disinfectant. Ozonation does not change the acidity of water and does not remove substances necessary for humans from it. Residual ozone quickly turns into oxygen (O 2) and enriches the water with it.

During ozonation, harmful reaction by-products do not have time to arise, at least in noticeable quantities.

Schematic flow diagram of water ozonation: 1 – source water reservoir; 2 – pump; 3 – mass transfer devices; 4 – purified water tank; 5 – ozone generators; 6 – air preparation and drying unit; 7 – ozone destructor (degasser).

There are some disadvantages of using ozonation, which impose corresponding restrictions on its use:

1. The ozonation method is technically complex, requires high energy consumption and the use of complex equipment, which requires highly qualified maintenance.

2. The prolonged action of ozone is significantly less than that of chlorine, due to its rapid destruction, so re-contamination of water during ozonation is more likely than during chlorination.

3. Ozonation can cause (especially in highly colored waters and waters with a large amount of “organic matter”) the formation of additional sediments, so after ozonation it is necessary to provide for filtering the water through activated carbon. As a result of ozonation, by-products are formed, including: aldehydes, ketones, organic acids, bromates (in the presence of bromides), peroxides and other compounds.

When exposed to humic acids, where there are aromatic compounds of the phenolic type, phenol may appear.

Ozone can only be produced at the point of consumption, since its storage and transportation are impossible. Free oxygen gas is needed to produce ozone.

5. Oligodynamy

Oligodynamy is the effect of noble metal ions on microbiological objects. When talking about oligodynamy, as a rule, three metals are considered - gold, copper and silver. The most common method for practical purposes is the use of silver; copper-based bactericidal solutions are sometimes used. Gold has no real use in practice, since this metal is very expensive.

5.1. Silver

Silver is a chemical element, belongs to the noble metals, symbolized by the symbol Ag (from the Latin Silver - light, white, English Argentum, French Argent, German Silber). It has serial number 47, atomic weight – 107.8, valence – I. II, density – 10.5 g/cm 3, melting point – 960.5 °C, boiling point – 2210 °C.

Despite the fact that silver ores are scattered throughout the world (Australia, Peru, Japan, Canada), the main supplier of silver is Mexico. Silver is a good conductor of thermal energy.

5.1.1. Story

Silver has been known to mankind since ancient times; at one time it was mined in the form of nuggets, that is, it did not have to be smelted from ores, and many peoples considered it a sacred metal, for example in Assyria and Babylon. In Europe, the wealth of kings was judged by the amount of silver. In the Middle Ages, silver and its compounds were very popular among alchemists. Later, dishes were made from silver, coins were minted, Jewelry, are now used in the manufacture of electrical contacts and printed circuits, power supplies.

The bactericidal effect of silver has also been known since ancient times. In ancient Hindu treatises there is a description of the ritual of briefly immersing hot silver in a container of water.

The founder of the scientific study of the mechanism of action of silver on microbial cells is the Swiss scientist Karl Nagel, who in the 80s. XIX century found that the interaction of silver ions (and not the metal itself) with microbial cells causes their death. He called this phenomenon oligodynamy (from the Greek “oligos” - small, trace and “dynamos” - action, i.e. the action of traces). The German scientist Vincent, comparing the activity of some metals, found that silver has the most powerful bactericidal effect, copper and gold have less. Thus, the diphtheria bacillus died on a silver plate after three days, on a copper plate after six days, on a gold plate after eight.

5.1.2. Description of the method

Academician L. A. Kulsky made a great contribution to the study of the antimicrobial properties of “silver” water and its use for the disinfection of drinking water and food products. His experiments, and later the work of other researchers, proved that it is metal ions and their dissociated compounds (substances that can disintegrate into ions in water) that cause the death of microorganisms. It has been proven that the higher the concentration of silver ions, the greater its activity and bactericidal effect.

It has been scientifically proven that silver in ionic form has bactericidal, antiviral, pronounced antifungal and antiseptic effects and serves as a highly effective disinfectant against pathogenic microorganisms that cause acute infections. The effect of killing bacteria with silver preparations is very great. It is 1750 times stronger than concentrated carbolic acid and 3.5 times stronger than sublimate. According to Academician of the Academy of Sciences of the Ukrainian SSR L.A. Kulsky, the effect of “silver” water (at the same concentrations) is greater than the effect of chlorine, bleach, sodium hypochloride and other strong oxidizing agents. According to scientific data, only 1 mg/l. silver for 30 minutes caused complete inactivation of influenza A, B, Miter and Sendai viruses. Already at a concentration of 0.1 mg/l, silver has a pronounced fungicidal effect.

“Silver” water has bactericidal properties at sufficiently high concentrations of silver, but at low concentrations silver has only a bacteriostatic effect.

However, when choosing silver as a disinfectant, you must remember that silver is a heavy metal. Like other heavy metals, silver can accumulate in the body and cause diseases (argyrosis - silver poisoning). In accordance with SanPiN 2.1.4.1074-01 “Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control" allowed silver content in water is not more than 0.05 mg/l and SanPin 2.1.4.1116 - 02 "Drinking water. Hygienic requirements for the quality of water packaged in containers. Quality control” – no more than 0.025 mg/l.

Many consumers, in the old-fashioned way, infuse water for days in home-grown silver water filters, in containers with coins, spoons and jewelry, and indeed “silver” water can be stored for years. But what lies behind this method of purifying water from microorganisms?

“Silver” water has bactericidal properties at fairly high concentrations of silver, about 0.015 mg/l. At low concentrations (10 -4 ... 10 -6 mg/l.), silver has only a bacteriostatic effect, i.e. it stops the growth of bacteria, but does not kill them. Spore-forming varieties of microorganisms are practically insensitive to silver. Therefore, infusing water the old fashioned way in home-grown silver water filters, in containers with coins, spoons and jewelry is not a guaranteed way to disinfect it.

The facts stated above thus somewhat limit the use of silver. It may only be appropriate for the purpose of preserving initially pure water for long-term storage (for example, spaceships, while hiking or when dispensing bottled drinking water). Silver plating of activated carbon cartridges is used in household filters. This is done to prevent the filters from fouling with microorganisms, since filtered organic substances are a good breeding ground for many bacteria.

5.1.3. Mechanism of action

Today, there are numerous theories explaining the mechanism of action of silver on microorganisms. The most common is the adsorption theory, according to which the cell loses its viability as a result of the interaction of electrostatic forces that arise between negatively charged bacterial cells and positively charged silver ions when the latter are adsorbed by the bacterial cell.

Voraz and Tofern (1957) explained the antimicrobial effect of silver by disabling enzymes containing SH - and COOH - groups, and K. Tonley, H. Wilson - by a violation of osmotic balance.

According to other theories, the formation of complexes of nucleic acids with heavy metals occurs, as a result of which the stability of DNA and, accordingly, the viability of bacteria are disrupted.

There is an opposing opinion that silver does not directly affect the DNA of cells, but acts indirectly by increasing the amount of intracellular free radicals, which reduce the concentration of intracellular reactive oxygen compounds. It is also assumed that one of the reasons for the broad antimicrobial effect of silver ions is the inhibition of transmembrane transport of Na + and Ca ++.

Based on the data, the mechanism of action of silver on a microbial cell is as follows: silver ions are sorbed by the cell membrane, which performs a protective function. The cell still remains viable, but some of its functions are disrupted - for example, division (bacteriostatic effect). As soon as silver is adsorbed on the surface of a microbial cell, it penetrates inside it, inhibits the enzymes of the respiratory chain, and also uncouples oxidation processes in microbial cells, as a result of which the cell dies.

Colloidal silver is a product consisting of microscopic particles of silver suspended in demineralized and deionized water. Colloidal silver, which is obtained by the electrolytic method, is a natural antibiotic approved for use in the USA by the Federal Commission on Food and Drug Administration back in 1920. The effectiveness of the bactericidal action of colloidal silver is explained by its ability to suppress the work of the enzyme, which ensures the oxygen exchange of foreign protozoan microorganisms, therefore they die due to a disruption in the oxygen supply necessary for their life.

5.1.4. Hardware design

It is possible to prepare “silver” water at home, but it is not effective. You can infuse water in a silver vessel, immerse silver objects, jewelry, etc. in a container with water... Currently, “silver” water is produced in electrical devices - ionizers. The operating principle of the silver ionator is based on the electrolytic method. Structurally, the device consists of an electrolyzer with silver electrodes (silver CP 99.99) and a power supply connected to a DC network. When direct current is passed through silver (or silver-copper) electrodes immersed in water, the silver electrode (anode), dissolving, saturates the water with silver ions. The concentration of the resulting solution at a given current depends on the operating time of the current source and the volume of water being treated. If you choose the ionizer correctly, the residual content of silver dissolved in water will not exceed the maximum dose of 10 -4 ... 10 -5 mg/l (at the same time, in the contact layer of silvering water, concentrations can reach 0.015 mg/l), which allows for simultaneous bactericidal and bacteriostatic water treatment. In table Table 4 shows the conditions for obtaining “silver” water using the example of the “LK-41” ionizer (ionator power source - 220 V AC power supply, load current, mA 0±20%, mass of silver transferred by the ionizer into an aqueous solution in 1 minute, mg 0.4±20%, temperature of treated water from 1 to 40 °C).

Table 4

Prepared silver solutions must be stored in a dark place or in an opaque closed container, since in the light silver ions are reduced to metal, the solution darkens, and silver precipitates.

The beginning of the production of ionizers in Russia dates back to 1939, when mass production of stationary ionizers, portable and road LC series began. Production continues today.

Now on the Russian market there are ionizers of different manufacturers and designs, with electronic control and the simplest autonomous pocket ones: “Nevoton IS”, “Penguin”, “Silva”, “Dolphin”, “LK”, “Aquatay”, etc.

When the ionizer operates, atomized black silver is released on the silver plates, which does not affect the quality of the prepared solution. In a silver solution, after the ionizer is turned off, the process of destroying bacteria does not occur immediately, but during the time specified in the holding time column.

5.1.5. The use of active carbons and cation exchangers saturated with silver

Currently, activated carbon is used in many water purification processes, the food industry, and chemical technology processes. The main purpose of coal is the adsorption of organic compounds. It is the filtered organic matter that provides the ideal breeding ground for bacteria to multiply when water movement stops. Applying silver to activated carbon prevents the growth of bacteria inside the filter due to the bactericidal properties of this metal. The technology of applying silver to the surface of coal is unique in that silver is not washed off from the surface of the coal during the filtering process. Depending on the manufacturer, type of raw material, and grade of coal, 0.06–0.12% silver by weight is applied to the surface.

Activated carbons coated with silver are available on the Russian market: C-100 Ag or C-150 Ag from Purolite; AGC is produced on the basis of activated carbon 207C by Chemviron Carbon; Russian manufacturers offer UAI-1, made from BAU-A charcoal; carbons of the KAUSORB-213 Ag and KAUSORB-222 Ag brands are obtained from active carbons of the KAUSORB-212 and KAUSORB-221 brands, etc.

Despite the fairly high efficiency of oligodynamy in general, we cannot talk about the absolute universality of this method. The fact is that a number of harmful microorganisms are outside the zone of its action - many fungi, bacteria (saprophytic, spore-forming). Nevertheless, water passed through such a filter usually retains its bactericidal properties and purity for a long time.

5.2. Copper

Copper is a chemical element, designated by the symbol Cu. The name of the element comes from the name of the island of Cyprus (lat. Cuprum), where copper was originally mined. It has serial number 29, atomic weight – 63.546, valency – I, II, density – 8.92 g/cm 3, melting point – 1083.4 °C, boiling point – 2567 °C.

Copper is a soft, malleable metal of red color, has high thermal and electrical conductivity (ranks second in electrical conductivity after silver).

Copper occurs in nature both in various compounds and in native form. There are various alloys of copper, the most famous of which are brass - an alloy with zinc, bronze - an alloy with tin, cupronickel - an alloy with nickel, etc., as an additive copper is present in babbitts.

Copper is widely used in electrical engineering (due to its low resistivity) for making power cables, wires or other conductors, such as printed circuit wiring. It is widely used in various heat exchangers, which include cooling, air conditioning and heating radiators due to the very important property of copper - high thermal conductivity.

Some copper compounds can be toxic when the maximum permissible concentrations in food and water are exceeded. The copper content in drinking water is also regulated by SanPiN 2.1.4.1074-01 and should not exceed 2 mg/l. The limiting sign of the harmfulness of a substance for which a standard has been established is sanitary-toxicological.

Copper levels in drinking water are usually quite low, amounting to a few micrograms per liter. Copper ions give water a distinct “metallic taste.” The sensitivity threshold for the organoleptic determination of copper in water is approximately 2–10 mg/l.

5.2.1. Story

The antibacterial properties of copper have been known for a very long time. In ancient Rus', so-called “bell” water was used for medical purposes. It was obtained during the casting of bells, when the still hot casting was cooled in containers filled with water. The bells were cast from bronze, an alloy of copper and tin, and to improve their sound, silver was added to this alloy. During cooling, the water became enriched with ions of copper, tin and silver.

The combined effect of copper and silver ions exceeds the strength of “silver” water, even if the concentration of silver ions in the latter is several times higher. It is important to understand that even “bell” water, if used uncontrolled, can cause great harm to the body.

Copper and its alloys are sometimes used for local disinfection of water, more often for disinfection in domestic and camping conditions, enriching the water with copper ions.

Since ancient times, it was also noted that water stored or transported in copper vessels was of higher quality and did not spoil for a long time, unlike water contained or transported in vessels made of other materials (visible mucus formation did not occur in such water).

There is a huge amount research work, confirming the bactericidal properties of copper.

5.2.2. Mechanism of action

Research to elucidate the mechanism of the antibacterial action of copper was carried out in ancient times. For example, in 1973, scientists from the Columbus Battel Laboratory conducted a comprehensive scientific and patent search, which collected the entire history of research on the bacteriostatic and disinfectant properties of copper and copper alloy surfaces for the period 1892-1973.

A discovery was made, and later confirmed, that the surfaces of copper alloys have a special property - to destroy wide range microorganisms.

Over the past 10 years, intensive research has been carried out on the effects of copper on pathogens of nosocomial infections: Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), influenza A virus, adenovirus, pathogenic fungi, etc. Research conducted in America has shown that the surface of a copper alloy (depending on the brand of alloy) is capable of killing E. coli after 1-4 hours of contact, while E. coli populations are killed by 99.9%, while, for example, on a stainless steel surface, microbes can survive for a week.

Brass, which is often used to make door handles and push plates, also has a germicidal effect, but it requires a longer exposure time than pure copper.

In 2008, after extensive research, the US Federal Environmental Protection Agency (US EPA) officially designated copper and several of its alloys as a material with a bactericidal surface.

5.2.3. Hardware design

Copper and its alloys are sometimes used for local disinfection of water (if there are no other, more suitable methods and reagents that provide a guaranteed disinfecting effect). More often it is used to disinfect water in domestic and camping conditions, enriching the water with copper ions.

There are several types of ionizers on the market - devices that use the principle of a galvanic couple and electrophoresis. Gold is used as the second electrode providing the potential difference. In this case, gold is applied in a thin layer to a special electrode substrate; it makes no sense to make the electrode entirely from gold alone, so the inner part of the electrode is made of an alloy of copper and silver in a certain ratio, usually an alloy of 17/1. Structurally, it can be a simple plate made of a copper-silver alloy (17/1) interspersed with gold, or a more complex flow-type device with a microcontroller control device.

6. Ultraviolet disinfection

6.1. Description of the method

Electromagnetic radiation within wavelengths from 10 to 400 nm is called ultraviolet.

To disinfect natural and waste waters, a biologically active region of the UV radiation spectrum with a wavelength from 205 to 315 nm, called bactericidal radiation, is used. Electromagnetic radiation at a wavelength of 200–315 nm has the greatest bactericidal effect (maximum virucidal effect) and maximum manifestation in the region of 260 ± 10 nm. Modern UV devices use radiation with a wavelength of 253.7 nm.

a – curve of the bactericidal action of ultraviolet light; b – curve of the bactericidal action of ultraviolet light and absorption spectra of DNA and protein

The UV disinfection method has been known since 1910, when the first stations for treating artesian water were built in France and Germany. The bactericidal effect of ultraviolet rays is explained by the photochemical reactions occurring under their influence in the structure of the DNA and RNA molecules, which constitute the universal information basis of the mechanism of reproducibility of living organisms.

The result of these reactions is irreversible damage to DNA and RNA. In addition, the action of UV radiation causes disturbances in the structure of membranes and cell walls of microorganisms. All this ultimately leads to their death.

The mechanism of disinfection by UV irradiation is based on damage to the DNA and RNA molecules of viruses. Photochemical action involves breaking or changing the chemical bonds of an organic molecule as a result of absorbing photon energy. There are also secondary processes based on the formation of free radicals in water under the influence of UV irradiation, which enhance the virucidal effect.

The degree of inactivation or the proportion of microorganisms killed under the influence of UV radiation is proportional to the radiation intensity and exposure time.

The product of radiation intensity and time is called the radiation dose (mJ/cm 2) and is a measure of virucidal energy. Due to the varying resistance of microorganisms, the dose of ultraviolet light required to inactivate them by 99.9% varies greatly, from low doses for bacteria to very high doses for spores and protozoa.

Installation diagram for UV water disinfection

6.2. Radiation dose

The main factors influencing the efficiency of disinfection of natural and waste waters by UV irradiation are:

– sensitivity of various viruses to UV irradiation;

– lamp power;

– degree of absorption of UV irradiation by the aquatic environment;

– level of suspended substances in disinfected water.

Different types of viruses under the same irradiation conditions are distinguished by the degree of sensitivity to UV irradiation. Radiation doses required for inactivation individual species viruses by 99.0–99.9%, are given in table. 5.

Table 5

(Information is given according to MUK 43.2030-05 “Sanitary and virological control of the effectiveness of disinfection of drinking and waste water by UV irradiation”).

When passing through water, UV radiation is attenuated due to absorption and scattering effects. The degree of absorption is determined by the physical and chemical properties of the treated water, as well as the thickness of its layer. To take into account this attenuation, the water absorption coefficient is introduced

Disinfection of drinking water serves to create a reliable barrier to the transmission of infectious disease pathogens by water. Methods of water disinfection are aimed at destroying pathogenic and opportunistic microorganisms, which ensures the epidemic safety of water.

Water is disinfected at the final stage of purification after clarification and decolorization before entering clean water tanks, which simultaneously serve as contact chambers. To disinfect water, reagent (chemical) and reagent-free (physical) methods are used. Reagent methods are based on the introduction of strong oxidizing agents into water (chlorination, ozonation, manganization, treatment of water with iodine), heavy metal ions and silver ions. Reagent-free treatments include heat treatment, ultraviolet irradiation, ultrasound treatment, y-irradiation, and ultrahigh-frequency current treatment. The method is selected depending on the quantity and quality of the source water, methods of its preliminary purification, requirements for the reliability of disinfection, taking into account technical and economic indicators, conditions of supply of reagents, availability of transport, and the possibility of automating the process.

Disinfection of water with chlorine and its compounds. Today, the most common method of water disinfection at waterworks remains chlorination. Among chlorine-containing compounds, given certain hygienic and technical advantages, liquid chlorine is most often used. It is also possible to use bleach, calcium and sodium hypochlorite, chlorine dioxide, chloramines, etc.

*For use in the practice of domestic and drinking water supply, only fluorine-containing compounds are allowed that have passed hygienic testing and are included in the "List of materials and reagents approved by the Main Sanitary and Epidemiological Directorate of the Ministry of Health of the USSR for use in the practice of domestic and drinking water supply (No. 3235-85)" .*

For the first time in water treatment practice, chlorine was used long before L. Pasteur’s discovery of microbes, R. Koch’s proof of the etiological significance of pathogenic microorganisms in the development of infectious diseases, T. Escherich’s final understanding of the microbiological essence of water epidemics and the bactericidal properties of chlorine. It was used to deodorize water that had an unpleasant “septic” odor. Chlorine turned out to be a very effective deodorant and, in addition, after treating water with chlorine, people were diagnosed with intestinal infections much less often. With the beginning of water chlorination, epidemics of typhoid and cholera stopped in many European countries. It has been suggested that the diseases were caused by bad smell and taste of water, which chlorine effectively eliminated. Only over time did they prove the microbial etiology of water epidemics of intestinal infections and recognize the role of chlorine as a disinfecting agent.

To chlorinate water, liquid chlorine is used, which is stored under pressure in special containers (cylinders), or substances containing active chlorine.

Chlorination of water with liquid chlorine. Chlorine (C12) at normal atmospheric pressure is a greenish-yellow gas that is 1.5-

2.5 times heavier than air, with a pungent and unpleasant odor, dissolves well in water, and easily liquefies with increased pressure. The atomic weight of chlorine is 35.453, molecular weight is 70.906 g/mol. Chlorine can be in three states of aggregation: solid, liquid and gaseous.

Chlorine is delivered to water supply stations for water disinfection in liquid cylinders under pressure. Chlorination is carried out using chlorinators. A chlorine solution is prepared in them, which is injected directly into the pipeline through which water enters the RHF. L.A. chlorinators are used. Kulsky (Fig. 20), vacuum chlorinators LONII-100, Zh-10, LK-12, KhV-11. The schematic diagram of the LONII-100 chlorinator is shown in Fig. 21.

When the cylinder is connected to a chlorinator, liquid chlorine evaporates. Chlorine gas is purified in a cylinder and on a filter, and after reducing its pressure using a reducer to 0.001-0.02 MPa, it is mixed with water in a mixer. From the mixer, concentrated

Rice. 21. Technology system typical chlorinator at 3 kg/h: 1 - platform scales; 2 - risers with cylinders; 3 - pollution catcher; 4 - chlorinators LONII-100; 5 - ejectors

The new solution is sucked into the ejector and fed into the pipeline. Chlorinators of the LK type, whose design is simpler and whose accuracy is lower, are used for high-power stations. These chlorinators do not require preliminary purification of chlorine, are not so accurate in dosing, but can supply chlorine water to a height of 20-30 m. After the ejector from LONIA-100, the pressure is only 1-2 m. During the dissolution of chlorine in water, its hydrolysis occurs with the formation of chloride (hydrochloric) and hypochlorite (or hypochlorous) acids:

C12+ H20 ^ HCl + HC10.

Hypochlorous acid HC10 is a weak monobasic unstable acid that easily dissociates to form hypochlorite ion (HC~):

NSYU ^ N+ + SYU".

The degree of dissociation of hypochlorous acid depends on the pH of the water. At pH
In addition, hypochlorous acid decomposes to form atomic oxygen, which is also a strong oxidizing agent:

NSyu It HCl + O".

*Active chlorine is one that is capable of releasing an equivalent amount of iodine from aqueous solutions of potassium iodide at pH 4. There are free (molecular chlorine, hypochlorous acid, hypochlorite ion) and bound (chlorine, which is part of organic and inorganic mono- and dichloramines) active chlorine.*

Previously, it was believed that it was this atomic oxygen that had a bactericidal effect. Today it has been proven that the disinfecting effect of liquid chlorine, as well as bleach, calcium and sodium hypochlorites, two-tertiary calcium salt hypochlorite is due to oxidizing agents that are formed in water when chlorine-containing compounds are dissolved, primarily by the action of hypochlorite acid, and then by the hypochlorite anion and finally atomic oxygen.

Chlorination of water with hypochlorites (salts of hypochlorous acid) is carried out at low-power water supply stations. Hypochlorites are also used for long-term disinfection of water in mine wells using ceramic cartridges, for disinfection of water in the field, including using fabric-carbon filters, etc.

Calcium hypochlorite Ca(OC1)2 is used to disinfect drinking water. During its dissolution in water, hydrolysis occurs with the formation of hypochlorous acid and its further dissociation:

Ca(OC1)2 + 2H20 = Ca(OH)2 + 2HCiu,

Neyu -?. n+ + cicr.

Depending on the method of calcium production, hypochlorite can contain from 57-60% to 75-85% active chlorine. Together with pure hypochlorite, a mixture of calcium hypochlorite and other salts (NaCl, CaCl2) is used to disinfect water. Such mixtures contain up to 60-75% pure hypochlorite.

At stations with active chlorine consumption up to 50 kg/day, sodium hypochlorite (NaCIO 5H20) can be used to disinfect water. This crystalline hydrate is obtained from sodium chloride (NaCl) solution by electrolytic method.

Sodium chloride in water dissociates to form sodium cation and chlorine anion:

NaCl ^ Na+ + SG

During electrolysis, chlorine ions are discharged at the anode and molecular chlorine is formed:

2SG -» C12 + 2e.

The resulting chlorine dissolves in the electrolyte:

С12+Н2О^НС1 + НСУ,

C12+OH-^CI+HCIu.

A discharge of water molecules occurs at the cathode:

H20 + e -> OH- + H+.

Hydrogen atoms, after recombination into molecular hydrogen, are released from solution as a gas. Hydroxyl anions OH" remaining in water react with sodium cations Na+, resulting in the formation of NaOH. Sodium hydroxide reacts with hypochlorous acid to form sodium hypochlorite:

NaOH + HC10 -> NaOCI + H20.

Rice. 22. Technological diagram for the electrolytic production of sodium hypochlorite: 1 - solution tank; 2 - pump; 3 - distribution tee; 4 - working tank; 5 - dispenser; 6 - electrolyzer with graphite electrodes; 7 - sodium hypochlorite storage tank; 8 - exhaust ventilation hood

Sodium hypochlorite dissociates to a large extent with the formation of "sodium hypochlorite", which has high antimicrobial activity:

NaCIO ^ Na+ + CIO",

Xiu- + n+;^nshu.

Electrolysis plants are divided into flow-through and batch. They include electrolyzers and various types of tanks. The schematic diagram of a batch installation is shown in Fig. 22. A sodium chloride solution of 10% concentration is fed into a tank at a constant level, from where it flows out at a constant flow rate. After filling the dosing tank, the siphon is activated and drains a certain volume of solution into the electrolyzer. Under the influence of electric current, sodium hypochlorite is formed in the electrolyzer. New portions of the salt solution push sodium hypochlorite into the supply tank, from which it is dosed by a dosing pump. The storage tank must contain a volume of sodium hypochlorite for at least 12 hours.

The advantage of producing sodium hypochlorite by the electrolytic method at the point of use is that there is no need to transport and store toxic liquefied chlorine. Among the disadvantages are significant energy costs.

Water disinfection by direct electrolysis. The method consists of direct electrolysis of fresh water, in which the natural chloride content is not lower than 20 mg/l, and hardness is not higher than 7 mEq/l. Used at water supply stations with a capacity of up to 5000 m3/day. Due to direct electrolysis at the anode, the chloride ions present in the water are discharged and molecular chlorine is formed, which is hydrolyzed to form hypochlorous acid:

2СГ ^ С12 + 2е, С12 + Н2О^НС1 + НСУ.

During the electrolysis treatment of water with a pH in the range of 6-9, the main disinfection agents are hypochlorous (hypochloritic) acid HSY, hypochlorite anion C10~ and monochloramines NH2C1, which are formed as a result of the reaction between HSY and ammonium salts contained in natural water. At the same time, during the treatment of water by the electrolytic method, microorganisms are exposed to the electric field in which they are located, which enhances the bactericidal effect.

Disinfection of water with bleach is used at small waterworks (with a capacity of up to 3000 m3/day), having previously prepared a solution. Ceramic cartridges are also filled with bleach to disinfect water in mine wells or local water supply systems.

Chlorine is a white powder with a pungent odor of chlorine and strong oxidizing properties. It is a mixture of calcium hypochlorite and calcium chloride. Bleach is obtained from limestone. Calcium carbonate at a temperature of 700 °C decomposes to form quicklime (calcium oxide), which, after interaction with water, turns into slaked lime (calcium hydroxide). When chlorine reacts with slaked lime, bleach is formed:

CaCO3 ^ CaO + CO2,

CaO + H20 = Ca(OH)2,

2Ca(OH)2 + 2C12 = Ca(OC1)2 + CaC12+ 2H20 or

2Ca(OH)2 + 2C12 = 2CaOC12 + 2H20.

The main component of bleach is expressed by the formula:

The technical product contains no more than 35% active chlorine. During storage, bleach is partially decomposed. The same thing happens with calcium hypochlorite. Light, humidity and high temperature accelerate the loss of active chlorine. Bleached lime loses approximately 3-4% of active chlorine per month due to hydrolysis reactions and decomposition in light. In a damp room, bleach decomposes, forming hypochlorous acid:

2CaOC12 + C02 + H20 = CaC03 + CaC12 + 2HCiu.

Therefore, before using bleach and calcium hypochlorite, their activity is checked - the percentage of active chlorine in the chlorine-containing preparation.

The bactericidal effect of bleach, like hypochlorites, is due to the group (OCG), which forms hypochlorous acid in an aquatic environment:

2CaOC12 + 2H20 -> CaC12 + Ca(OH)2 + 2HC10.

Chlorine dioxide (ClOJ is a yellow-green gas, easily dissolves in water (at a temperature of 4 °C, 20 volumes of gaseous ClO2 are dissolved in 1 volume of water). It does not hydrolyze. It is advisable to use it if the characteristics of natural water are unfavorable for effective disinfection chlorine, for example, at high pH values ​​or in the presence of ammonia. However, the production of chlorine dioxide is a complex process that requires special equipment, qualified personnel, additional financial costs. In addition, chlorine dioxide is explosive, which requires strict adherence to safety requirements. The above is limited use of chlorine dioxide for water disinfection in domestic and drinking water supply systems.

Chlorine-containing preparations also include chloramines (inorganic and organic), which are used to a limited extent in water treatment practice, but are used as disinfecting agents during disinfection activities, in particular in medical institutions. Inorganic chloramines (monochloramines NH2C1 and dichloramines NHC12) are formed by the reaction of chlorine with ammonia or ammonium salts:

NH3 + CI2 = NH2CI + HCI,

NH2CI + CI2 = NHCI2 + HCl.

Together with inorganic chlorine compounds, organic chloramines (RNHC1, RNC12) are also used for disinfection. They are obtained by reacting bleach with amines or their salts. In this case, one or two hydrogen atoms of the amine group are replaced by chlorine. Different chloramines contain 25-30% active chlorine.

The process of water disinfection with chlorine-containing preparations occurs in several stages:

1. Hydrolysis of chlorine and chlorine-containing preparations:

C12 + H20 = HCl + HC10;

Ca(OC1)2 + 2H20 = Ca(OH)2+ 2HC10;

2CaOC12 + 2H20 = Ca(OH)2 + CaC12 + 2HC10.

2. Dissociation of hypochlorous acid.

At pH ~ 7.0 HC10 dissociates: HC10
3. Diffusion of the HC10 molecule and the CO ion into the bacterial cell.

4. Interaction of the disinfecting agent with enzymes of microorganisms that are oxidized by hypochlorous acid and hypochlorite ion.

Active chlorine (NCH and CL") first diffuses inside the bacterial cell and then reacts with enzymes. Undissociated hypochlorous acid (NCH) has the greatest bactericidal and virucidal effect. The rate of water disinfection is determined by the kinetics of chlorine diffusion inside the bacterial cell and the kinetics of cell death as a result of metabolic disorders.With an increase in the concentration of chlorine in water, its temperature and with the transition of chlorine into the undissociated form of easily diffusible hypochlorous acid, the overall speed of the disinfection process increases.

The mechanism of the bactericidal action of chlorine consists of the oxidation of organic compounds of the bacterial cell: coagulation and damage to its membrane, inhibition and denaturation of enzymes that provide metabolism and energy. The most damaged are thiol enzymes containing SH groups, which are oxidized by hypochlorous acid and hypochlorite ion. Among thiol enzymes, the most actively inhibited group is dehydrogenases, which ensure respiration and energy metabolism of the bacterial cell1. Under the influence of hypochlorous acid and hypochlorite ion, dehydrogenases of glucose, ethyl alcohol, glycerol, succinic, glutamic, lactic, pyruvic acid, formaldehyde, etc. are inhibited. Inhibition of dehydrogenases leads to inhibition of oxidation processes at the initial stages. The consequence of this is both inhibition of the processes of bacterial reproduction (bacteriostatic effect) and their death (bactericidal effect).

The mechanism of action of active chlorine on viruses consists of two phases. First, hypochlorous acid and hypochlorite ion are adsorbed on the virus shell and penetrate through it, and then they inactivate the RNA or DNA of the virus.

As the pH value increases, the bactericidal activity of chlorine in water decreases. For example, to reduce the number of bacteria in water by 99% at a dose of free chlorine of 0.1 mg/l, the contact duration increases from 6 to 180 minutes when the pH increases from 6 to 11, respectively. Therefore, it is advisable to disinfect water with chlorine at low pH values, that is before introducing alkaline reagents.

The presence in water of organic compounds capable of oxidation, inorganic reducing agents, as well as colloidal and suspended substances that envelop microorganisms, slows down the process of water disinfection.

The interaction of chlorine with water components is a complex and multi-stage process. Small doses of chlorine are completely bound by organic substances, inorganic reducing agents, suspended particles, humic substances and water microorganisms. For a reliable disinfecting effect of water after chlorination, it is necessary to determine the residual concentrations of free or combined active chlorine.

*Energy metabolism in bacteria occurs in mesosomes - analogues of mitochondria.*

Rice. 23. Graph of the dependence of the amount and type of residual chlorine on the administered dose of chlorine

In Fig. Figure 23 shows the relationship between the dose of introduced chlorine and residual chlorine in the presence of ammonia or ammonium salts in the water. When chlorinating water that does not contain ammonia or other nitrogen-containing compounds, with an increase in the amount of chlorine added to the water, the content of residual free chlorine in it increases. But the picture changes if there is ammonia, ammonium salts and other nitrogen-containing compounds in the water, which are integral part natural water or artificially introduced into it. In this case, chlorine and chlorine agents interact with ammonia, ammonium and organic salts containing amino groups present in the water. This leads to the formation of mono- and dichloramines, as well as extremely unstable trichloramines:

NH3 + H20 = NH4OH;

C12 + H20 = HC10 + HCl;

HCJ + NH4OH = NH2C1 + H20;

NSJ + NH2C1 = NHC12+ H20;

NSJ + NHC12 = NC13 + H20.

Chloramines are combined active chlorine, which has a bactericidal effect that is 25-100 times less than that of free chlorine. In addition, depending on the pH of the water, the ratio between mono- and dichloramines changes (Fig. 24). At low pH values ​​(5-6.5), dichloramines are predominantly formed, and at high pH values ​​(more than 7.5), monochloramines are formed, the bactericidal effect of which is 3-5 times weaker than that of dichloramines. The bactericidal activity of inorganic chloramines is 8-10 times higher than that of chlorinated organic amines and imines. When adding low doses of chlorine to water at a molar ratio of C12: NH*
*There is no ammonia-free water in nature. It can only be prepared in a laboratory from distilled water.*

residual chlorine associated with amines accumulates. As the dose of chlorine increases, more chloramines are formed and the concentration of residual bound chlorine increases to a maximum (point A).

With a further increase in the dose of chlorine, the molar ratio of the introduced chlorine and the NH * ion contained in the water becomes greater than one. In this case, mono-, di- and, especially, trichloramines are oxidized by excess chlorine in accordance with the following reactions:

NHC12 + NH2C1 + NSJ -> N20 + 4HC1;

NHC12 + H20 -> NH(OH)Cl + HCl;

NH(OH)Cl + 2HC10 -> HN03 + ZHC1;

NHC12 + HCIO -> NC13 + H20;

4NH2C1 + 3C12 + H20 = N2 + N20 + 10HC1;

IONCI3 + CI2 + 16H20= N2 + 8N02 + 32HCI.

When the molar ratio Cl2: NH\ is up to 2 (10 mg Cl2 per 1 mg N2 in the form of NH\), due to the oxidation of chloramines with excess chlorine, the amount of residual bound chlorine in water decreases sharply (segment III) to a minimum point (point B), which is called point fracture Graphically, it looks like a deep dip in the residual chlorine curve (see Fig. 23).

With a further increase in the dose of chlorine after the turning point, the concentration of residual chlorine in the water begins to gradually increase again (segment IV on the curve). This chlorine is not associated with chloramines, is called free residual (active) chlorine and has the highest bactericidal activity. It acts on bacteria and viruses like active chlorine in the absence of ammonia and ammonium compounds in the water.

According to research data, water can be disinfected with two doses of chlorine: before and after the turning point. However, when chlorinated with a pre-turnover dose, the water is disinfected due to the action of chloramines, and when chlorinated with a post-turnover dose, it is disinfected by free chlorine.

During water disinfection, the added chlorine is spent both on interaction with microbial cells and viruses, and on the oxidation of organic and mineral compounds (urea, uric acid, creatinine, ammonia, humic substances, ferrous iron salts, ammonium salts, carbamates, etc. ), which are contained in water in a suspended and dissolved state. The amount of chlorine absorbed by water impurities (organic substances, inorganic reducing agents, suspended particles, humic substances and microorganisms) is called the chlorine absorption capacity of water (segment I on the curve). Since natural waters have different compositions, their chlorine absorption is not the same. Thus, chlorine absorption is the amount of active chlorine that is absorbed by suspended particles and spent on the oxidation of bacteria, organic and inorganic compounds contained in 1 liter of water.

You can count on successful water disinfection only if there is a certain excess of chlorine in relation to the amount that is absorbed by bacteria and various compounds contained in the water. An effective dose of active chlorine is equal to the total amount of absorbed and residual chlorine. The presence of residual chlorine in water (or, as it is also called, excess) is associated with the idea of ​​​​the effectiveness of water disinfection.

When chlorinating water with liquid chlorine, calcium and sodium hypochlorites, and bleach, a 30-minute contact provides a reliable disinfecting effect with a residual chlorine concentration of at least 0.3 mg/l. But when chlorination with preammonization, contact should be for 1-2 hours, and the effectiveness of disinfection will be guaranteed in the presence of residual bound chlorine in a concentration of at least 0.8 mg/l.

Chlorine and chlorine-containing compounds significantly affect the organoleptic properties of drinking water (smell, taste), and in certain concentrations they irritate the mucous membranes of the oral cavity and stomach. The maximum concentration of residual chlorine at which drinking water does not acquire a chlorine smell and taste is set at 0.5 mg/l for free chlorine, and 1.2 mg/l for bound chlorine. According to toxicological characteristics, the maximum concentration of active chlorine in drinking water is 2.5 mg/l."

Therefore, to disinfect water, it is necessary to add such an amount of chlorine-containing preparation that after treatment the water contains 0.3-0.5 mg/l of residual free or 0.8-1.2 mg/l of residual bound chlorine. This excess of active chlorine does not impair the taste of water or harm health, but guarantees its reliable disinfection.

Thus, for effective disinfection, a dose of active chlorine is added to water equal to the sum of chlorine absorption and residual active chlorine. This dose is called the chlorine requirement of water.

Chlorine requirement of water is the amount of active chlorine (in milligrams) required for effective disinfection of 1 liter of water and ensuring the content of residual free chlorine within 0.3-0.5 mg/l after 30 minutes of contact with water, or the amount of residual bound chlorine within 0.8-1.2 mg after 60 minutes of contact. Residual content

*The maximum concentration of chlorine dioxide in drinking water is not higher than 0.5 mg/l, the limiting indicator of water action is organoleptic.*

Active chlorine is controlled after clean water tanks before being supplied to the water supply network. Since the chlorine absorption of water depends on its composition and is not the same for water from different sources, in each case the chlorine requirement is determined experimentally by test chlorination. Approximately, the chlorine requirement of clarified and bleached river water by coagulation, sedimentation and filtration ranges from 2-3 mg/l (sometimes up to 5 mg/l), groundwater interstratal water - within 0.7-1 mg/l.

Factors influencing the process of water chlorination are associated with: 1) biological characteristics of microorganisms; 2) bactericidal properties of chlorine-containing preparations; 3) the state of the aquatic environment; 4) with the conditions in which disinfection is carried out.

It is known that spore cultures are many times more resistant than vegetative forms to the action of disinfectants. Enteroviruses are more persistent than intestinal bacteria. Saprophytic microorganisms are more resistant than pathogenic ones. Moreover, among pathogenic microorganisms, the most sensitive to chlorine are the causative agents of typhoid fever, dysentery, and cholera. The causative agent of paratyphoid B is more resistant to chlorine. In addition, the higher the initial contamination of water by microorganisms, the lower the efficiency of disinfection under the same conditions.

The bactericidal activity of chlorine and its compounds is associated with the magnitude of its redox potential. The redox potential increases at the same concentrations in the series: chloramine -> bleach -> chlorine - chlorine dioxide.

The effectiveness of chlorination depends on the properties and composition of the aquatic environment, namely: the content of suspended solids and colloidal compounds, the concentration of dissolved organic compounds and inorganic reducing agents, the pH of the water, and its temperature.

Suspended substances and colloids prevent the action of the disinfectant on microorganisms located in the thickness of the particle and absorb active chlorine due to adsorption and chemical binding. The effect on the efficiency of chlorination of organic compounds dissolved in water depends both on their composition and on the properties of chlorine-containing preparations. Thus, nitrogen-containing compounds of animal origin (proteins, amino acids, amines, urea) actively bind chlorine. Compounds that do not contain nitrogen (fats, carbohydrates) react less strongly with chlorine. Since the presence of suspended substances, humic and other organic compounds in water reduces the effect of chlorination, for reliable disinfection, cloudy and highly colored waters are first clarified and discolored.

When the water temperature decreases to 0-4 °C, the bactericidal effect of chlorine decreases. This dependence is especially noticeable in experiments with high initial contamination of water and in the case of chlorination with low doses of chlorine. In the practice of water supply stations, if the source water contamination meets the requirements of State Standard 2761-84 “Sources of centralized household and drinking water supply. Hygienic, technical requirements and quality control", lowering the temperature does not significantly affect the effectiveness of disinfection.

The mechanism of the influence of water pH on its disinfection with chlorine is associated with the characteristics of the dissociation of hypochlorous acid: in an acidic environment, the equilibrium shifts towards the molecular form, in an alkaline environment - towards the ionic form. Hypochlorous acid in undissociated molecular form penetrates better through the membranes into the middle of the bacterial cell than hydrated hypochlorite ions. Therefore, in an acidic environment, the process of water disinfection is accelerated.

The bactericidal effect of chlorination is significantly affected by the dose of the reagent and the duration of contact: the bactericidal effect increases with increasing dose and increasing the duration of action of active chlorine.

Methods of water chlorination. There are several methods of chlorination. water treatment, taking into account the nature of residual chlorine, the choice of which is determined by the characteristics of the composition of the water being treated. Among them: 1) chlorination with post-turnover doses; 2) conventional chlorination or chlorination according to chlorine demand; 3) superchlorination; 4) chlorination with preammonization. In the first three options, water is disinfected with free active chlorine. During chlorination with preammonization, the bactericidal effect is due to the action of chloramines, i.e., bound active chlorine. In addition, they apply combined methods chlorination.

Chlorination with post-breaking doses provides that after 30 minutes of contact, free active chlorine will be present in the water. The dose of chlorine is selected so that it is slightly higher than the dose at which a break in the residual chlorine curve is formed, i.e. in range IV (see Fig. 23). The dose selected in this way causes the least amount of residual free chlorine to appear in the water. This method is characterized by careful dose selection. It provides a stable and reliable bactericidal effect and prevents the appearance of odors in water.

Conventional chlorination (chlorination according to chlorine demand) is the most common method of disinfecting drinking water with centralized domestic drinking water supply. Chlorination according to chlorine demand is carried out with a post-turnover dose that, after 30 minutes of contact, ensures the presence of residual free chlorine in the water within the range of 0.3-0.5 mg/l.

Since natural waters differ significantly in composition and therefore have different chlorine absorption, chlorine demand is determined experimentally by experimental chlorination of water to be disinfected. Besides the right choice doses of chlorine, a prerequisite for effective water disinfection is thorough mixing and exposure time, i.e., the time of contact of chlorine with water (at least 30 minutes).

As a rule, at waterworks, chlorination according to chlorine demand is carried out after clarification and decolorization of water. The chlorine requirement of such water ranges from 1-5 mg/l. The optimal dose of chlorine is introduced into the water immediately after filtration before RHF.

Based on the chlorine requirement, double chlorination can be carried out, in which chlorine is fed into the mixer for the first time before the reaction chamber, and for the second time after the filters. In this case, the experimentally determined optimal dose of chlorine is not changed. Chlorine, when introduced into the mixer in front of the reaction chamber, improves coagulation and discoloration of water, which makes it possible to reduce the dose of coagulant. In addition, it inhibits the growth of microflora that contaminates the sand in the filters. The total consumption of chlorine with double chlorination practically does not increase and remains almost the same as with single chlorination.

Double chlorination deserves widespread use. It should be used in cases where river water pollution is relatively high or subject to frequent fluctuations. Double chlorination increases the sanitary reliability of water disinfection.

Superchlorination (rechlorination) is a method of water disinfection that uses increased doses of active chlorine (5-20 mg/l). These doses are actually post-fracture doses. In addition, they significantly exceed the chlorine requirement of natural water and cause the presence of high (over 0.5 mg/l) concentrations of residual free chlorine in it. Therefore, the superchlorination method does not require preliminary determination of the chlorine requirement of water and careful selection of the dose of active chlorine, however, after disinfection it is necessary to remove excess free chlorine.

Superchlorination is used in special epidemiological situations, when it is impossible to determine the chlorine requirement of water and to ensure sufficient contact time of chlorine with water, as well as to prevent the appearance of odors in water and combat them. This method is convenient in military field conditions and in emergency situations.

Superchlorination effectively ensures reliable disinfection of even cloudy water. High doses of active chlorine kill pathogens resistant to disinfectants, such as Burnett's rickettsia, dysentery amoeba cysts, mycobacterium tuberculosis and viruses. But even such doses of chlorine cannot reliably disinfect water from anthrax spores and helminth eggs.

With superchlorination, the residual free chlorine in disinfected water significantly exceeds 0.5 mg/l, which makes the water unsuitable for consumption due to the deterioration of its organoleptic properties (the pungent odor of chlorine). Therefore, there is a need to free it from excess chlorine. This process is called dechlorination. If the excess residual chlorine is small, it can be removed by aeration. In other cases, water is purified by filtering through a layer of activated carbon or using chemical methods, such as treating sodium hyposulfite (thiosulfate), sodium bisulfite, sulfur dioxide (sulfur dioxide), iron sulfate. In practice, sodium hyposulfite (thiosulfate) is mainly used - Na2S203 5H20. Its amount is calculated depending on the amount of excess chlorine, based on the following reaction:

Na2S203 + C12+ H20 = Na2S04 + 2HCI + si.

According to the given binding reaction between active chlorine and sodium hyposulfite at a molar ratio of 1:1, 0.0035 g of sodium hyposulfite crystalline hydrate is used per 0.001 g of chlorine, or 3.5MrNa2S203-5H20 per 1 mg of chlorine.

Chlorination with preammonization. The chlorination method in preammonization is used:

1) in order to prevent the appearance of unpleasant specific odors that arise after chlorination of water containing phenol, benzene and ethylbenzene;

2) to prevent the formation of carcinogenic substances (chloroform, etc.) during chlorination of drinking water containing humic acids and methane hydrocarbons;

3) to reduce the intensity of the odor and taste of chlorine, especially noticeable in summer time;

4) to save chlorine with high chlorine absorption of water and the absence of odors, tastes and high bacterial contamination.

If natural water contains phenols (for example, due to pollution of water bodies by wastewater from industrial enterprises) even in small quantities1, then when disinfected with chlorine-containing compounds that hydrolyze to form hypochlorous acid, free active chlorine immediately reacts with phenol, forming chlorophenols, which even in small quantities concentrations give the water a birdlike taste and smell. At the same time, bound active chlorine - chloramine, having a lower redox potential, does not interact with phenol to form chlorophenols, and therefore the organoleptic properties of water do not deteriorate during disinfection. Similarly, free active chlorine is capable of interacting with methane hydrocarbons to form trihalomethanes (chloroform, dibromochloromethane, dichlorobromomethane), which are carcinogens. Their formation can be prevented by disinfecting water with bound active chlorine.

When chlorinating with preammonization, a solution of ammonia2 or its salts is first added to the water that is being disinfected, and after 1-2 minutes chlorine is introduced. As a result, chloramines (monochloramines NH2C1 and dichloramines NHC12) are formed in water, which have a bactericidal effect. Chemical reactions for the formation of chloramines are given on p. 170.

The ratio of substances formed depends on pH, temperature and the amount of reacting compounds. The effectiveness of chlorination with preammonization depends on the ratio of NH3 and C12, and doses of these reagents are used in proportions of 1:2, 1:4, 1:6, 1:8. For each water supply source, it is necessary to select the most effective ratio. The rate of water disinfection with chloramines is lower than the rate of disinfection with free chlorine, therefore the duration of water disinfection in the case of chlorination with preammonization should be at least 2 hours. The features of the bactericidal effect of chloramines, as well as their ability not to form chlorine derivatives that have specific odors, are explained by their significant

*MPC of phenol in water is 0.001 mg/l, the limiting indicator is organoleptic (smell), 4th hazard class.*

*To introduce ammonia into water, it is most convenient to use vacuum chlorinators.*

But less oxidative activity, since the redox potential of chloramines is much lower than that of chlorine.

In addition to pre-ammonization (the introduction of ammonia 1-2 minutes before the introduction of chlorine), post-ammonization is sometimes used, when ammonia is introduced after chlorine directly into tanks with clean water. Due to this, chlorine is fixed longer than the increase in the duration of its action is achieved.

Combined methods of water chlorination. In addition to the considered methods of water chlorination, a number of combined ones have been proposed, when another chemical or physical disinfectant is used together with chlorine-containing compounds, which increases the disinfection effect. Chlorination can be combined with water treatment with silver salts (chlorine-silver method), potassium permanganate (chlorination with manganization), ozone or ultraviolet light, ultrasound, etc.

Chlorination with manganization (with the addition of KMP04 solution) is used when it is necessary to enhance the oxidative and bactericidal effect of chlorine, since potassium permanganate is a stronger oxidizing agent. The method should be used if there are odors and tastes in the water that are caused by organic substances and algae. In this case, potassium permanganate is introduced before chlorination. KMP04 should be added before settling tanks in doses of 1-5 mg/l or before filters in doses of 0.08 mg/l. Reducing itself to water-insoluble Mn02, it is completely retained in settling tanks and filters.

The silver chloride method is used on river fleet vessels (on KVU-2 and UKV-0.5 installations). It provides enhanced disinfection of water and its preservation for a long period (up to 6 months) with the addition of silver ions in an amount of 0.05-0.1 mg/l.

In addition, the silver chloride method is used to disinfect water in swimming pools, where it is necessary to reduce the dose of chlorine as much as possible. This is possible because the bactericidal effect is provided within the total effect of doses of chlorine and silver.

The bactericidal, virucidal and oxidative effects of chlorine can be enhanced by simultaneous exposure to ultrasound, ultraviolet radiation, and direct electric current.

Water samples are taken after clean water reservoirs before being supplied to the water supply network. The effectiveness of chlorination by residual active chlorine is monitored hourly, that is, 24 times a day. Chlorination is considered effective if the residual free chlorine content is in the range of 0.3-0.5 mg/l after 30 minutes of contact, or the residual bound chlorine content is 0.8-1.2 mg/l after 60 minutes of contact.

According to microbiological indicators of epidemic safety, water after RHF is examined twice a day, that is, once every 12 hours. In the water after disinfection, the total microbial number and the coliform index (coli-index) are determined. Water disinfection is considered effective if the coli index does not exceed 3, and the total microbial number does not exceed 100.

Negative consequences of water chlorination for public health. As a result of the reaction of chlorine with humic compounds, waste products of aquatic organisms and some substances of industrial origin, dozens of new extremely dangerous haloform compounds are formed, including carcinogens, mutagens and highly toxic substances with maximum permissible concentrations at the level of hundredths and thousandths of a milligram per 1 liter. In table 3 and 5 (see pp. 66, 67, 101) show some halogen-containing compounds, features of their effect on the human body, and hygienic standards in drinking water. Indicators of this group are trihalomethanes: chloro- and bromoform, dibromochloromethane, bromodichloromethane. In disinfected drinking water and hot water supply, chloroform is detected most often and in higher concentrations - a group 2B carcinogen, according to the IARC classification.

Haloform compounds enter the body with water not only enterally. Some substances penetrate intact skin during contact with water, particularly when swimming in a pool. When you take a bath or shower, haloform compounds are released into the air. A similar process occurs in the process of boiling water, laundry, and cooking.

Taking into account the extreme danger of haloform compounds to human health, a set of measures has been developed to reduce their levels in water. It provides:

Protection of the water supply source from pollution by wastewater that contains precursors of haloform compounds;

Reducing eutrification of surface water bodies;

Refusal of rechlorination (primary chlorination) or its replacement with ultraviolet irradiation or the addition of copper sulfate;

Optimization of coagulation to reduce water color, that is, removal of humic substances (precursors of haloform compounds);

The use of disinfectants that have a lower ability to form haloform compounds, in particular chlorine dioxide, chloramines;

The use of chlorination with preammonization;

Aerating the water or using granular activated carbon is the most effective way to remove haloform compounds from the water.

A radical solution to the problem is to replace chlorination with ozonation and disinfection of water with UV rays.

Ozonation of water and its advantages over chlorination. Ozonation is one of the promising methods of water treatment for the purpose of its disinfection and improvement of organoleptic properties. Today, almost 1000 waterworks in Europe, mainly in France, Germany and Switzerland, use ozonation in their water treatment process. Recently, ozonation has begun to be widely implemented in the USA and Japan. In Ukraine, ozonation is used at the Dnieper water supply

Rice. 25. Technological diagram of the ozonation plant:

1 - air intake; 2 - air filter; 3 - warning valve; 4 - five supply fans; 5 - air plunger; 6 - two refrigerated dryers; 7 - four adsorption dryings; 8 - activated alumina; 9 - cooling of fan heaters; 10 - fifty ozone generators (pictured 2); 11 - dry air; 12 - cooling water inlet; 13 - cooling water outlet; 14 - ozonated air; 15 - three tanks for ozone diffusion; 16 - water level

Stations in Kyiv, in the CIS countries - at water supply stations in Moscow ( Russian Federation) and Minsk (Belarus).

Ozone (Os) is a pale violet gas with a specific odor and a strong oxidizing agent. Its molecule is very unstable, easily disintegrates (dissociates) into an atom and an oxygen molecule. Under industrial conditions, an ozone-air mixture is produced in an ozonizer using a “slow” electrical discharge at a voltage of 8000-10,000 V.

A schematic diagram of the ozonator installation is shown in Fig. 25. The compressor takes in air, cleans it from dust, cools it, dries it on adsorbers with silica gel or active aluminum oxide (which are regenerated by blowing hot air). Next, the air passes through the ozonizer, where ozone is formed, which is supplied through the distribution system to the water of the contact tank. The dose of ozone required for disinfection for most types of water is 0.5-6.0 mg/l. Most often, for underground water sources, the dose of ozone is taken in the range of 0.75-1.0 mg/l, for surface waters - 1-3 mg/l. Sometimes high doses are needed to discolor and improve the organoleptic properties of water. The duration of contact of ozone with water must be at least 4 minutes1. Indirect indicator

*In accordance with GOST 2874-82, the duration of water disinfection using ozone was at least 12 minutes. The same duration is regulated by SanPiN 2.1.4.559-96 approved by the Ministry of Health of Russia "Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control." In accordance with SanPiN "Drinking water. Hygienic requirements for the quality of water from centralized household and drinking water supply", approved by the Ministry of Health of Ukraine, the duration of ozone treatment must be at least 4 minutes.*

The effectiveness of ozonation is the presence of residual amounts of ozone at a level of 0.1-0.3 mg/l after the mixing chamber.

Ozone in water decomposes, forming atomic oxygen: 03 -> 02 + O". It has been proven that the mechanism of ozone decomposition in water is complex. In this case, a number of intermediate reactions occur with the formation of free radicals (for example, HO *), which are also oxidizing agents. More The strong oxidative and bactericidal effect of ozone compared to chlorine is explained by the fact that its oxidation potential is greater than that of chlorine.

From a hygienic point of view, ozonation is one of the best methods of water disinfection. As a result of ozonation, a reliable disinfecting effect is achieved, organic impurities are destroyed, and the organoleptic properties of water not only do not deteriorate, as with chlorination or boiling, but also improve: color decreases, unnecessary taste and smell disappear, water acquires a blue tint. Excess ozone quickly decomposes, producing oxygen.

Ozonation of water has the following specific advantages over chlorination:

1) ozone is one of the most powerful oxidizing agents, its redox potential is higher than that of chlorine and even chlorine dioxide;

2) during ozonation, nothing foreign is introduced into the water and no noticeable changes occur mineral composition water and pH;

3) excess ozone turns into oxygen after a few minutes, and therefore does not affect the body and does not impair the organoleptic properties of water;

4) ozone, interacting with compounds contained in water, does not cause the appearance of unpleasant tastes and odors;

5) ozone decolorizes and deodorizes water containing organic substances of natural and industrial origin, giving it odor, taste and color;

6) compared to chlorine, ozone more effectively disinfects water from spore forms and viruses;

7) the ozonation process is less susceptible to the influence of variable factors (pH, temperature, etc.), which facilitates the technological operation of water treatment facilities, and monitoring efficiency is no more difficult than with water chlorination;

8) ozonation of water ensures uninterrupted water treatment, eliminating the need to transport and store unsafe chlorine;

9) ozonation produces significantly fewer new toxic substances than chlorination. These are mainly aldehydes (for example, formaldehyde) and ketones, which are formed in relatively small quantities;

10) ozonation of water makes it possible to comprehensively treat water, which can simultaneously achieve disinfection and improve organoleptic properties (color, smell and taste).

Disinfection of water with silver ions. Water treated with silver at a dose of 0.1 mg/l maintains high sanitary and hygienic indicators throughout the year. Silver can be introduced directly by ensuring contact of water with the surface of the metal itself, as well as by dissolving silver salts in water electrolytically. L.A. Kulsky developed ionizers LK-27, LK-28, which provide for the anodic dissolution of silver by electric direct current.

The mechanism of action of chemical disinfectants on microorganisms. The initial stage of the action of any disinfectant on a bacterial cell is its sorption on the cell surface (O.S. Savluk, 1998). After the disinfectants diffuse through the cell wall, the targets of their action are the cytoplasmic membrane, nucleoid, cytoplasm, ribosomes, and mesosomes. The next stage is the degradation of macromolecular, including protein, structures of the bacterial cell as a result of inactivation of highly reactive functional groups (sulfhydryl, amine, phenolic, indole, thioethyl, phosphate, keto groups, endocyclic nitrogen atoms, etc.). The most sensitive are enzymes containing SH groups, i.e. thiol enzymes. Among them, dehydrogenases, which ensure the respiration of bacteria and are localized mainly in mesosomes, are most strongly inhibited.

Among the organelles of the bacterial cell, one of the most damaged by chemical disinfectants is the cytoplasmic membrane. This is due to its easy accessibility to the oxidizing agent (compared to other organelles) and the presence of a large number of active groups (including sulfhydryl groups), which are easily inactivated. Therefore, relatively small amounts of disinfectants are needed to damage the cytoplasmic membrane. Due to the importance of the functions of the cytoplasmic membrane for the life of a bacterial cell, its damage is extremely dangerous.

The nucleoid, the main part of which is the DNA molecule, despite the presence of reactive groups that are potentially capable of interacting with disinfectants, is inaccessible to their molecules and ions. This is caused, firstly, by the difficulties of transporting the disinfectant from an aqueous solution into the nucleoid through the outer and cytoplasmic membranes of the bacterial cell, and hence by the unproductive losses of disinfecting agents. Secondly, the presence of a primary hydration shell on the surface of DNA becomes an obstacle for some disinfectants. In particular, this hydration shell is impermeable to cations.

A significant amount of disinfectant is necessary to inactivate ribosomes and polysomes that contain rRNA, which is due to their high concentration in the bacterial cell (compared to DNA).

Chemical disinfectants must have the widest possible spectrum of bactericidal action and minimal toxicity to the body. Taking into account the mechanism of interaction with bacterial cells, chemical disinfectants are divided into two groups:

1. Substances that affect cellular structures due to chemical and physical effects, i.e. substances with a polar structure that contain lipophilic and hydrophilic groups (alcohols, phenols, cresols, detergents, polypeptide antibiotics). They dissolve fragments of cellular structures - membranes, violating their integrity and, accordingly, their functions. Possessing a wide spectrum of bactericidal action due to the similarity in the structure of cell membranes in various prokaryotes, this class of disinfectants is effective only in high concentrations - from 1 to 10 M.

2. Substances that damage cellular structures due to chemical interaction. They can be divided into 2 subclasses: 1) substances that only inhibit the growth of bacteria; 2) substances that cause their death. The line between them is quite arbitrary and is largely determined by concentration. Disinfectants that cause cell death include almost all heavy metals that form difficult-to-dissociate complexes with sulfhydryl groups, as well as cyan-anions, which form difficult-to-dissociate complexes with iron, thereby blocking the function of the terminal respiratory enzyme cytochrome oxidase. Disinfectants that inhibit the growth of bacteria, when interacting with functional groups of cellular compounds, either lead to their transformation (reversible under certain conditions) into other groups, or inhibit them due to the structural similarity of disinfectants with normal cellular metabolites.

The effectiveness of chemical disinfectants also depends on the possibilities of their transport through cellular structures to the target in the cell. Gracilicute (Gram-negative) and firmicute (Gram-positive) bacteria have different membrane structures, with the main difference being that Gracilicute bacteria have an additional outer layer consisting of phospholipids, lipoproteins and proteins. Both two- and three-layer shell structures provide high selectivity for the penetration of foreign substances from outside into the cell.

In addition to transport restrictions, the effectiveness of chemical disinfectants can be affected by the electrolyte composition of the water being disinfected. For example, when heavy metal cations are used for disinfection, the presence of certain anions (C1~, Br", I", SO^~, POJ", etc.) and an alkaline environment can lead to the formation of highly soluble, poorly dissociated compounds.

The interaction of disinfectants with cell metabolites and chemical compounds contained in it can also lead to changes physical and chemical properties disinfectant. So, according to L.A. Kulsky (1988), the intracellular fluid contains almost 3 mEq/L anions, up to 100 mEq/L HPOj" and almost 20 mEq/L SOj", which is quite sufficient for the conversion of many disinfectants, for example heavy cations metals into slightly dissociated compounds.

The mechanism of bactericidal action makes it possible to explain the synergistic effects that are observed experimentally when water is disinfected with combinations of chemical disinfectants or through physical influence and the action of a chemical disinfectant. From the perspective of the mechanism considered, the action of one of the combination of disinfectants neutralizes the “sacrificial defense” system of the bacterial cell, after which the other disinfectant gains almost unhindered access to the main targets and, interacting with them, inactivates the cell.

Thus, combinations of chemical disinfectants should have optimal bactericidal properties, in which one is capable of irreversibly binding sulfhydryl groups of shell proteins, and the other, having highly selective transport properties, quickly diffuses into the cytoplasm of the cell and, interacting with DNA and RNA, inactivates the bacterial cell. Such highly effective combinations disinfectants are systems C12: H202, C12: 03, C12: Ag+, I2: Ag+, etc. When a combination of physical influence and the action of a chemical disinfectant, as a result of physical impact on the bacterial cell membrane, disorganization or partial destruction of its structure occurs. This facilitates easier transportation of the chemical disinfectant to the cell targets and its further inactivation. The use of combinations of disinfectants is very effective in inactivating mutant bacterial cells, which are found in cell populations in the amount of 10-40%.

The considered mechanism of the bactericidal action of chemical disinfectants makes it possible to explain the patterns of inactivation of viruses and bacteriophages. In particular, the increased resistance of bacteriophages to chemical disinfectants compared to bacterial cells is explained by their presence in the cytoplasm of the bacterium and thus low accessibility to most chemical disinfectants. Inactivation of viruses and bacteriophages outside the bacterial cell by chemical disinfectants is possibly due to denaturation of the protein shells of the virus and interaction with its enzyme systems located under the protein shells.

Disinfection of water by ultraviolet (UV) irradiation. Disinfection of water with UV rays is a physical (reagent-free) method. Reagent-free methods have a number of advantages: when used, the composition and properties of water do not change, unpleasant tastes and odors do not appear, and there is no need for transportation and storage of reagents.

The bactericidal effect is exerted by the UV part of the optical spectrum in the wave range from 200 to 295 nm. The maximum bactericidal effect occurs at 260 nm. Such rays penetrate a 25-centimeter layer of clear and colorless water. Water is disinfected by UV rays quite quickly. After 1-2 minutes of irradiation, vegetative forms of pathogenic microorganisms die. Turbidity and especially color, color and iron salts, reducing the permeability of water to bactericidal UV rays, slow down this process. That is, a prerequisite for reliable disinfection of water with UV rays is its preliminary clarification and bleaching.

Water from underground water sources, the coli index of which is not more than 1000 CFU/l, and the iron content is not more than 0.3 mg/l, are disinfected by UV irradiation using bactericidal lamps. Bactericidal installations are installed on the suction and pressure lines of pumps of the second lift in

Rice. 26. Installation for water disinfection with UV rays (OB AKX-1):

A - section; b - diagram of the movement of water through the chamber; 1 - viewing window; 2 - body; 3 - partitions;

4 - water supply; 5 - mercury-quartz lamp PRK-7; 6 - quartz cover in individual buildings or rooms. If the productivity of a waterworks is up to 30 m3/h, installations with a non-submersible radiation source in the form of low-pressure argon-mercury lamps are used. If the productivity of the station is 30-150 m3/h, then installations with submersible high-pressure mercury-quartz lamps are used (Fig. 26).

When using low-pressure argon-mercury lamps, no toxic by-products are formed in water, whereas under the influence of high-pressure mercury-quartz lamps, the chemical composition of water can change due to photochemical transformations of substances dissolved in water.

The disinfecting effect of bactericidal UV rays is due primarily to photochemical reactions, which results in irreversible damage to the DNA of the bacterial cell. In addition to DNA, UV rays also damage other structural parts of the cell, in particular rRNA, cell membranes. The bactericidal energy yield is 11% at the optimal length of most of the emitted waves.

Thus, bactericidal rays do not denature water and do not change its organoleptic properties, and also have a wider range of abiotic effects - they have a detrimental effect on spores, viruses and helminth eggs that are resistant to chlorine. At the same time, the use of this method of water disinfection complicates the operational control of effectiveness, since the results of determining the microbial number and coli index of water can be obtained only after 24 hours of incubation of crops, and the rapid method, which is similar to the determination of residual free or combined chlorine or residual ozone, does not exist in this case.

Ultrasonic water disinfection. The bactericidal effect of ultrasound is explained mainly by the mechanical destruction of bacteria in the ultrasonic field. Electron microscopy data indicate destruction of the bacterial cell membrane. The bactericidal effect of ultrasound does not depend on turbidity (up to 50 mg/l) and color of water. It applies to both vegetative and spore forms of microorganisms and depends only on the intensity of fluctuations.

Ultrasonic vibrations, which can be used to disinfect water, are produced by piezoelectric or magnetostrictive methods. To obtain water that meets the requirements of GOST 2874-82 "Drinking water. Hygienic requirements and quality control", the ultrasound intensity should be about 2 W/cm2, the oscillation frequency should be 48 kHz per 1 s. Ultrasound with a frequency of 20-30 kHz destroys bacteria in 2-5 s.

Thermal disinfection of water. The method is used to disinfect small amounts of water in sanatoriums, hospitals, on ships, trains, etc. Complete disinfection of water and the death of pathogenic bacteria is achieved after 5-10 minutes of boiling the water. For this type of disinfection, special types of boilers are used.

Disinfection with X-ray radiation. The method involves irradiating water with short-wave X-rays with a wavelength of 60-100 nm. Short-wave radiation penetrates deeply into bacterial cells, causing their significant changes and ionization. The method has not been studied enough.

Disinfection by vacuuming. The method involves the inactivation of bacteria and viruses under reduced pressure. The full bactericidal effect is achieved within 15-20 minutes. The optimal processing mode is at a temperature of 20-60 °C and a pressure of 2.2-13.3 kPa.

Other physical methods of disinfection, such as treatment with y-irradiation, high-voltage discharges, low-power electrical discharges, alternating electric current, are used limitedly due to their high energy intensity, the complexity of the equipment, as well as due to their insufficient knowledge and lack of information about the possibility of formation harmful side compounds. Most of them are currently at the stage of scientific development.

Disinfection of water in the field. The water supply system in the field must guarantee the receipt of high-quality drinking water that does not contain pathogens of infectious diseases. Of the technical means suitable for improving water quality in the field, special attention fabric carbon filters (TCF) deserve: portable, transportable, simple and highly productive.

TUF design by M.N. Klyukanov are intended for temporary use (water supply in field conditions, rural areas,

new buildings, during expeditions). Water is purified and disinfected according to M.N. Klyukanov by simultaneous coagulation and disinfection with increased doses of chlorine (superchlorination) with further filtration through TUV (Fig. 27). Suspended particles are retained on the fabric filter layer, that is, water clarification and discoloration are achieved, and dechlorination is carried out on the carbon filter layer.

For coagulation, aluminum sulfate - A12(S04)3 is used in an amount of 100-200 mg/l. The dose of active chlorine for water disinfection (superchlorination) is at least 50 mg/l. A coagulant and bleach or DTSGK (two-thirds-basic salt of hypo-

Calcium chlorite) in doses of 150 and 50 mg/l, respectively. In this case, coagulation is not affected by the alkalinity of the water:

A) with bleach -

A12(S04)3 + 6CaOC12 + 6H20 -> -> 2A1(OH)3 + 3CaS04 + 3CaC12 + 6HOCI;

B) with DTSGK -

A12(S04)3 + 3Ca(OS1)2 2Ca(OH)2 + 2H20 -> ->2A1(OH)3 + 3CaS04 + 2Ca(OS1)2 + 2HOC1.

Typically, coagulation occurs by the reaction of aluminum sulfate with water bicarbonates, which should be at least 2 mEq/l. In other cases, the water needs to be alkalized.

15 minutes after treatment with the above reagents, the settled water is filtered through TUV. Residual chlorine and organoleptic properties are determined in purified water.

Water supply network and structures on it. The water supply network (water supply distribution system) is an underground system of pipes through which water under pressure (at least 2.5-4 atm for a five-story building) created by a pumping station of the second rise is supplied to a populated area and distributed on its territory. It consists of the main water pipelines through which water from the water supply station enters the populated area, and an extensive network of pipes through which water is supplied to water reservoirs, external water intake structures (street pumps, fire hydrants), residential and public buildings. In this case, the main water pipeline branches into several main lines, which in turn branch into street, courtyard and house lines. The latter are connected to the internal water supply pipe system of residential and public buildings.

Rice. 28. Scheme water supply network: A - dead-end circuit; B - ring circuit; A - pumping station; b - water supply; c - water tower; d - populated areas; d - distribution network

According to the configuration, the water supply network can be: 1) ring; 2) dead end; 3) mixed (Fig. 28). A dead-end network consists of separate blind lines into which water enters from one side. If such a network is damaged in any area, the water supply to all consumers who are connected to the line located behind the point of damage in the direction of water movement is stopped. At the dead-end ends of the distribution network, water can stagnate and sediment may appear, which serves as a favorable environment for the proliferation of microorganisms. As an exception, a dead-end water supply network is installed in small township and rural water supply systems.

The best from a hygienic point of view is a closed water supply network, which consists of a system of adjacent closed circuits, or rings. Damage in any area does not stop the water supply, as it can flow through other lines.

The water supply distribution system must ensure an uninterrupted supply of water to all points of its consumption and prevent water contamination along the entire path of its supply from the main water supply facilities to consumers. To do this, the water supply network must be waterproof. Water pollution in the water supply network during centralized water supply is caused by: leakage of water pipes, a significant decrease in pressure in the water supply network, which leads to the suction of pollution in leaky areas, and the presence of a source of pollution near the site of leakage of water pipes. It is unacceptable to combine household and drinking water supply networks with networks supplying non-potable water (technical water supply).

Water pipes are made of cast iron, steel, reinforced concrete, plastics, etc. Pipes made of polymer materials, as well as internal anti-corrosion coatings, are used only after they have been hygienically assessed and received permission from the Ministry of Health. Steel pipes are used in areas with internal pressure above 1.5 MPa, at intersections with railways, highways, surface reservoirs (rivers), at the intersection of drinking water supply and sewerage. They need to protect the outer and inner surfaces from corrosion. The diameter of drinking water pipes in urban settlements must be at least 100 mm, in rural areas - more than 75 mm. A hermetically sealed connection of individual pipe sections 5-10 m long is achieved using flanges, sockets or couplings (Fig. 29). Flange connections are used only when laying pipes open (on the surface of the ground), where they are accessible to external examination and leak testing.

The laying of water supply lines for domestic and drinking water supply must be preceded by a sanitary assessment of the territory by at least 40 m in both directions when the water supply is located in an undeveloped area and by 10-15 m in a built-up area. The soil on which the water supply route will be laid must be uncontaminated. The route should not be laid through swamps, landfills, cemeteries, cattle burial grounds, that is, where the soil is contaminated. It is necessary to organize a sanitary protective strip along the water pipelines (see pp. 129, 130).

Water pipes must be laid 0.5 m below the level of zero temperature in the soil (soil freezing level). Moreover, depending on the climatic region, the depth of laying pipes ranges from 3.5 to 1.5 m. In the southern regions, in order to prevent overheating of water in the summer, the depth of laying water pipes should be such that the soil layer above the pipe is at least 0.0 m thick. 5 m.

Water lines must be laid 0.5 m higher than sewer lines. If water pipes are laid at the same level as parallel sewer lines, the distance between them must be at least 1.5 m for water pipes with a diameter of up to 200 mm and at least 3 m for a diameter over 200 mm. In this case, it is necessary to use metal pipes. Metal water pipes are also used at places where they intersect with sewer lines. In this case, water pipes should be laid 0.5 m higher than sewer pipes. As an exception, at intersections, water pipes can be located below sewer pipes. In this case, it is allowed to use only steel water pipes, additionally protecting them with a special metal casing with a length of at least 5 m on both sides of the intersection in clay soils and at least 10 m in soils with high filtration capacity (for example, sandy). Sewer pipes in the specified area must be cast iron.

The following are installed on water pipelines and water supply lines: butterfly valves (bolts) to isolate repair areas; plungers - to release air during pipeline operation; valves - for the release and admission of air when emptying pipelines of water during repairs and subsequent filling; outlets - for discharging water when emptying pipelines; pressure regulators, valves to protect against water hammer, if you suddenly need to turn off or turn on pumps, etc. The length of repair sections when laying water pipelines in one line should not exceed 3 km, in two lines or more - 5 km.

Shut-off, control and security valves are installed in inspection water supply wells. Inspection wells are also installed at all joints of main, main and street water pipelines. Wells are waterproof reinforced concrete shafts located underground. To descend into the inspection well, there is a hatch with a hermetically sealed lid, which is insulated during the cold season; Cast iron or steel brackets are built into the wall. The danger of water contamination in the water supply network through inspection wells arises when the shaft is filled with water. This can occur as a result of water entering through leaky walls and bottom, storm water through a leaky lid, or water from the water supply network through leaky joints of pipes and fittings. When the pressure in the network decreases, water that has collected in the inspection well can be sucked into the pipes.

Water-pressure (spare) tanks are designed to create a water reserve that compensates for possible discrepancies between water supply and its consumption at certain hours of the day. Reservoirs are filled mainly at night, and during the day, during hours of intensive water use, water from them enters the network, normalizing the pressure.

Water tanks are installed at the highest point of the relief on towers rising above the tallest buildings in the settlement (Fig. 30). The area around the water towers is fenced off. Tanks must be waterproof, made of iron or reinforced concrete. For cleaning, repairing and disinfecting the internal surface of the tank

Rice. 30. Water tower: a - appearance; b - section: I - supply and distribution pipe; 2 - overflow pipe

Hatches with tightly closed and sealed covers are provided. For air exchange, the tanks are equipped with ventilation openings covered with meshes and protected from precipitation. Taps are installed on the pipes supplying and discharging water to take water samples in order to control its quality before and after the tank. Water tanks require periodic (1-2 times a year) disinfection.

On large water pipelines, spare tanks - clean water tanks - are installed underground. From these, water is supplied to the water supply network by pumping stations of the third lift.

Water taps. The population takes water from the water distribution system or through house inlets and taps of the intra-house water supply network, or through external water distribution facilities - standpipes.

Street water taps are the most vulnerable elements of the water supply system. There are many known cases of epidemic outbreaks of infectious diseases, which are called “single column” epidemics.

There are different designs of columns, but the most common are the Cherkunov and Moscow type systems. They are installed in building areas without introducing centralized drinking water supply pipes into the buildings. In this case, the service radius of the column should be no more than 100 m. Recently, in cities with centralized water supply with water intake from surface reservoirs, columns are widely used to organize pump room artesian water supply1.

The water standpipe of the Cherkunov system (Fig. 31) consists of above-ground and underground parts. Underground part(inspection well) has the appearance of a shaft with waterproof reinforced concrete walls and bottom. An ejector is located there (it is installed along the path of water movement from the water main to the internal water tube of the column) and a drain tank with an air tube. A hermetically sealed hatch is located in the reinforced concrete ceiling of the shaft. The ground part of the column has an outlet tube and a handle, which is connected by a rod to a valve located in front of the ejector at the water outlet from the water main. Around the column, within a radius of 1.5-2 m, a blind area is installed with an inclination from the column; under the outlet pipe there is a tray for draining water spilled during use.

When the handle is pressed, the valve opens, and water from the water main rises under pressure through the water pipe and pours out through the outlet pipe of the column. When the handle is released, the valve closes. Since the water remaining in the water pipe freezes and breaks the pipe during the cold season, it is drained into a metal tank at the bottom of the inspection well. In this case, air from the tank enters the shaft through the air tube. When the handle is pressed again and the valve is opened, water, coming out under pressure through a narrowed hole in the water main into the water pipe, activates the ejector. The ejection (suction) effect, which occurs in the first seconds after opening the valve and does not last long, sucks water from the tank into the water tube. The tank is filled with air from the shaft through an air pipe. Thus, the first portions of water coming from the column immediately after pressing the handle are a mixture of water from the water supply network and the drain tank. Due to the suction of water from the tank, the pressure in the ejector is equalized, the ejection effect disappears, after which water is supplied to the consumer exclusively from the water supply network. When the handle is released, the tank is filled again with water from the water tube of the column.

A real threat of water contamination in the dispenser can arise if the dispenser shaft fills with water. The ways in which water enters a mine can be different. Thus, precipitation and surface runoff

*Pump room water supply is provided through local water supply. Its elements are: 1) underground interstratal (preferably artesian) source of class I according to GOST 2761-84; 2) artesian well; 3) underground pumping station with a submersible centrifugal pump; 4) pressure water pipeline; 5) pump room with water dispensers (mainly Moscow type). Pump room artesian water supply is widespread in Kyiv, where centralized water supply is provided through the Dnieper and Desnyansky river and artesian water pipelines.*

Rice. 31. Water dispenser of the Cherkunov system: 1 - detail of the ejector and tank; 2 - injector; 3 - coupling; 4 - narrowed end of the water pipe; 5 - counterweight; 6 - tray; 7 - plaster; 8 - flooring made of boards; 9 - air tube; 10 - water pipe; 11 - ejector; 12 - staples; 13 - rod; 14 - sand; 15 - valve (38 mm); 16 - shut-off valve; 17 - tank

They can penetrate into the inspection well through a leaky ceiling or leaking hatch. If the integrity of the reinforced concrete walls and the bottom of the shaft is damaged, water can come from the soil (soil moisture, which is formed during the filtration of atmospheric and melt water), especially when the groundwater level is high. The mine may be flooded with water from the water supply network. This occurs when the pressure in the network drops below 1 atm. Wherein

Transparency and increased color impair the organoleptic properties of well and spring water, limit its use, and sometimes indicate water contamination as a result of errors in the equipment of water intake structures (wells or spring catchments), their improper placement relative to potential sources of pollution, or improper operation. Sometimes the reason for a decrease in transparency and an increase in color of well and spring water can be a high concentration of iron salts (over 1 mg/l).

In well water, which is epidemically safe, the coliform index usually does not exceed 10 (coli-titer is at least 100), the microbial number is no more than 400 per 1 cm3. With such sanitary and microbiological indicators, pathogens of intestinal infections that have a water transmission factor are not detected in water.

The nitrate content in well and spring water should not exceed 45 mg/l, in terms of nitrate nitrogen - 10 mg/l. Exceeding the specified concentration may cause water-nitrate methemoglobinemia (acute toxic cyanosis) in formula-fed infants due to the use of water with a high nitrate content for the preparation of nutritional formulas. A slight increase in the level of methemoglobin in the blood without threatening signs of hypoxia can also be observed in children aged 1 to 6 years, as well as in older people.

An increase in the content of ammonium salts, nitrites and nitrates in well and spring water may indicate contamination of the soil through which the supply water is filtered, as well as the fact that pathogenic microorganisms could have entered along with these substances. With fresh contamination in the water, the content of ammonium salts increases. The presence of nitrates in water in the absence of ammonia and nitrites indicates a relatively ancient intake of nitrogen-containing substances into the water. With systematic pollution in water, both ammonium salts and nitrites and nitrates are detected. Intensive use of nitrogen fertilizers in agriculture also leads to an increase in the content of nitrates in groundwater. An increase in the permanganate oxidation of groundwater above 4 mg/l indicates possible contamination with easily oxidized substances of mineral and organic origin.

One of the indicators of contamination of local water supplies is chlorides. At the same time, high concentrations (over 30-50 mg/l) of chlorides in water can be caused by their leaching from saline soils. Under such conditions, 1 liter of water can contain hundreds and thousands of milligrams of chlorides. Water with a chloride content of more than 350 mg/l has a salty taste and has a negative effect on the body. To correctly assess the origin of chlorides, one should take into account their presence in the water of neighboring water sources of the same type, as well as other indicators of pollution.

In some cases, each of these indicators may have a different nature. For example, organic substances can be of plant origin. Therefore, water from a local source can be considered polluted only under the following conditions: 1) not one, but several sanitary and chemical indicators of pollution are increased; 2) at the same time, sanitary and microbiological indicators of epidemic safety have been increased - microbial number and coli index; 3) the possibility of contamination is confirmed by data from a sanitary inspection of a well or spring capture.

Hygienic requirements for the placement and construction of mine wells. A mine well is a structure with the help of which the population collects groundwater and raises it to the surface. In local water supply conditions, it simultaneously performs the functions of water intake, water lifting and water distribution structures.

When choosing a location for a well, in addition to hydrogeological conditions, it is necessary to take into account the sanitary conditions of the area and the ease of use of the well. The distance from the well to the consumer should not exceed 100 m. Wells are placed along the slope of the area above all sources of pollution located both on the surface and in the thickness of the soil. Subject to these conditions, the distance between the well and the source of pollution (site for underground filtration, cesspool, compost, etc.) must be at least 30-50 m. If the potential source of pollution is located higher in the terrain than the well, then the distance between them is In the case of fine-grained soil, it should be at least 80-100 m, and sometimes even 120-150 m.

The magnitude of the sanitary gap between a well and a potential source of soil pollution can be scientifically substantiated using the Saltykov-Belitsky formula, which takes into account local soil and hydrogeological conditions. The calculation is based on the fact that pollution, moving along with groundwater in the direction of the well, should not reach the point of water intake, that is, there should be enough time to disinfect the pollution. The calculation is made using the formula:

Where L is the permissible distance between the source of pollution and the point of water intake (m), k is the filtration coefficient1 (m/day) determined experimentally or from tables, p, is the groundwater level in the area of ​​contamination of the aquifer, determined experimentally by a level; n2 is the water level of the aquifer at the point of water intake; t is the required time for water to move between the source of pollution and the point of water intake (this time is assumed to be 200 days for bacterial pollution, and 400 days for chemical pollution); ts - active soil porosity2.

*Filtration coefficient is the distance that water travels in the soil, moving vertically downward under the influence of gravity. Depends on the mechanical composition of the soil. For medium-grained sands it is 0.432, for fine-grained sands - 0.043, for loams - 0.0043 m/day.*

*Active porosity is the ratio of the pore volume of a water-bearing rock sample to the total volume of the sample. Depends on the mechanical composition of the soil: for coarse-grained sands - 0.15, for fine-grained sands - 0.35.*

This formula is suitable for calculations only when the water-bearing rock is fine- and medium-grained sand. If the water-bearing layer is represented by coarse-grained sands or even gravelly soils, the safety factor A should be added to the found value:

The coefficient is determined by the formula: A = ai + a2 + a3, where a! - the radius of the depression funnel1 is maximum for coarse sands 300-400 m, for medium gravel - 500-600 m; a2 is the distance over which the pollution plume spreads (depending on the power of the pollution source, it ranges from 10 to 100 m); a3 - value security zone, disrupting the hydraulic connection between the pollution plume and the peripheral end of the radius of the depression funnel (10-15 m).

A well is a vertical shaft of square or round cross-section (with an area of ​​approximately 1 m2), which reaches the aquifer (Fig. 33). The bottom is left open, and the side walls are secured with waterproof material (concrete, reinforced concrete, brick, wood, etc.). A layer of gravel 30 cm thick is poured onto the bottom of the well. The walls of the well must rise above the ground surface by at least 1 m. A clay castle and blind area are installed around the well to prevent the seepage of contaminants along the walls of the well (outside), which are washed out from the surface layers of the soil. To build a clay castle, a hole 2 m deep and 1 m wide is dug around a well and filled with rich clay. For a blind area around the ground part of the well, on top of the clay castle, within a radius of 2 m, a backfill is made with sand and filled with cement or concrete with a slope to divert atmospheric precipitation and water that spills when using the well away from the well. To drain storm water, an intercepting ditch is installed. A fence should be made within a radius of 3-5 m around public wells to restrict vehicle access.

It is advisable to lift water from the well using a pump. If this is not possible, then equip a swing with a public bucket attached to it. It is unacceptable to use your own bucket, as this poses the greatest risk of contaminating the water in the well. The frame of the well is tightly closed with a lid and a canopy is made over the frame and the frame.

Captage is a special structure for collecting spring water (Fig. 34). The water outlet must be fenced with waterproof walls and closed at the top. To prevent surface runoff from entering the spring, diversion ditches are installed. A castle made of greasy clay and a blind area are installed around the walls of the captage. Materials for captage structures can be

*A depression funnel is a zone of low pressure that forms in the water-bearing rock when water is pumped out of a well due to the resistance exerted by the rock. Depends on the mechanical composition of the rock and the speed of pumping out water.*

Rice. 33. General view of a mine well: 1 - bottom three-layer filter; 2 - reinforced concrete rings made of porous concrete; 3 - reinforced concrete rings; 4 - cover; 5 - manhole clamps; 6 - stone blind area; 7 - rotation; 8 - clay castle; 9 - canopy cover

Be concrete, reinforced concrete, brick, stone, wood. To prevent the water in the catchment from rising above a certain level, an overflow pipe is installed at this level.

Sanitation of mine wells. Sanitation of a mine well is a set of measures to repair, clean and disinfect a well in order to prevent contamination of the water in it.

For preventive purposes, the well is sanitized before putting it into operation, and then, if the epidemic situation is favorable, there is no pollution and there are no complaints from the population about the quality of water, periodically once a year after cleaning and routine repairs. It is mandatory to carry out

Rice. 34. Simple capture of a descending spring: 1 - aquifer; 2 - waterproof layer; 3 - gravel filter; 4 - receiving chamber; 5 - inspection well; 6 - inspection well hatch with cover; 7 - ventilation hatch; 8 - partition; 9 - discharge into a sewer or ditch; 10 - pipe supplying water to the consumer

Preventive disinfection after overhaul well. Preventive sanitation consists of two stages: 1) cleaning and repair; 2) disinfection.

If there are epidemiological grounds to consider a well a source of spread of acute gastrointestinal infectious diseases, and also if there is a suspicion (especially data) of water contamination with feces, animal corpses, or other foreign objects, sanitation is carried out according to epidemiological indications. Sanitation according to epidemiological indications is carried out in three stages: 1) preliminary disinfection; 2) cleaning and repair; 3) final disinfection.

Methodology for the sanitation of mine wells. Sanitation according to epidemiological indications begins with disinfection of the underwater part of the well using a volumetric method. To do this, determine the volume of water in the well and calculate the required amount of bleach or calcium hypochlorite using the formula:

Where P is the amount of bleach or calcium hypochlorite (g), E is the volume of water in the well (m3); C is the specified concentration of active chlorine in the well water (100-150 g/m3), sufficient to disinfect the walls of the log house and the gravel filter at the bottom, H is the content of active chlorine in bleach or calcium hypochlorite (%); 100 is a constant numerical coefficient. If the water in the well is very cold (+4 °C...+6 °C), the amount of chlorine-containing preparation for disinfecting the well by volumetric method is doubled. The calculated amount of disinfectant is dissolved in a small volume of water in a bucket until a uniform mixture is obtained, clarified by settling and this solution is poured into the well. The water in the well is mixed well for 15-20 minutes with poles or by frequently lowering and raising the bucket on a cable. Then the well is covered with a lid and left for 1.5-2 hours.

After preliminary disinfection, the water is completely pumped out of the well using a pump or buckets. Before a person goes down into the well, they check whether CO2 has accumulated there, for which a lit candle is lowered into a bucket at the bottom of the well. If it goes out, then you can only work in a gas mask.

Then the bottom is cleaned of silt, dirt, debris and random objects. The walls of the log house are cleaned mechanically from dirt and fouling and, if necessary, repaired. Dirt and silt selected from the well are placed in a hole at a distance of at least 20 m from the well to a depth of 0.5 m, filled with a 10% solution of bleach or 5% calcium hypochlorite solution and buried.

For final disinfection, the outer and inner surfaces of the log house are irrigated from a hydraulic console with a 5% solution of bleach or a 3% solution of calcium hypochlorite at the rate of 0.5 dm3 per 1 m2 of area. Then they wait until the well is filled with water to the usual level, after which the underwater part is disinfected using a volumetric method at the rate of 100-150 mg of active chlorine per 1 liter of water in the well for 6-8 hours. After the specified contact time, a water sample is taken from the well and check it for the presence of residual chlorine or do a smell test. If there is no smell of chlorine, add 1/4 or 1/3 of the original amount of the drug and leave for another 3-4 hours. After this, a water sample is taken and sent to the territorial SES laboratory for bacteriological and physicochemical analysis. At least 3 studies must be carried out, each 24 hours later.

Disinfection of a well for preventive purposes begins with determining the volume of water in the well. Then they pump out the water, clean and repair the well, disinfect the outer and inner parts of the log house using the irrigation method, wait until the well is filled with water, and disinfect the underwater part using the volumetric method.

Disinfection of water in a well using dosing cartridges. Among the measures to improve the local water supply important place involves continuous disinfection of water in the well using dosing cartridges. Indications for this are: 1) non-compliance of microbiological indicators of water quality in the well with sanitary requirements; 2) presence of signs of water contamination according to sanitary and chemical indicators (disinfected until the source of contamination is identified and positive results are obtained after sanitation); 3) insufficient improvement in water quality after disinfection (sanitation) of the well (coli titer below 100, coli index above 10); 4) in foci of intestinal infections in locality after disinfection of the well until the outbreak is eliminated. Only specialists from the territorial SES disinfect the water in the well using a dosing cartridge, always monitoring the quality of the water according to sanitary-chemical and microbiological indicators.

Dosing cartridges are cylindrical ceramic containers with a capacity of 250, 500 or 1000 cm3. They are made from: fireclay clay, infusor earth (Fig. 35). Bleach or calcium hypochlorite is poured into the cartridges and immersed in the well. Quantity

Rice. 35. Dosing cartridge

The chlorine-containing substances required for water disinfection depend on many factors. These include: the initial quality of groundwater, the nature, degree of contamination and volume of water in the well, the intensity and mode of water withdrawal, the rate of groundwater inflow, and the flow rate of the well. The amount of active chlorine also depends on the sanitary condition of the well: the amount of bottom sludge, the degree of contamination of the log house, etc. It is known that pathogens of intestinal infections find favorable conditions in bottom sludge and long time maintain vital activity. This is why long-term disinfection (chlorination) of water using dosing cartridges cannot be effective without first cleaning and disinfecting the well.

The amount of calcium hypochlorite with an activity of at least 52%, required for long-term disinfection of water in a well, is calculated using the formula:

X, = 0.07 X2 + 0.08 X3+ 0.02 X4 + 0.14 X5,

Where X is the amount of drug required to load the cartridge (kg), X2 is the volume of water in the well (m3), calculated as the product of the cross-sectional area of ​​the well and the height of the water column; X3 - well flow rate (m3/h), determined experimentally; X4 - water withdrawal (m3/day), determined by surveying the population; X5 - chlorine absorption of water (mg/l), determined experimentally.

The formula is given to calculate the amount of calcium hypochlorite containing 52% active chlorine. In case of disinfection with bleach (25% active chlorine), the calculated amount of the drug should be doubled. When disinfecting water in a well in winter, the calculated amount of the drug is also doubled. If the content of active chlorine in the disinfectant is lower than calculated, then recalculation is made using the formula:

Where P is the amount of bleach or calcium hypochlorite (kg); X! - the amount of calcium hypochlorite calculated using the previous formula (kg); H, is the content of active chlorine in calcium hypochlorite, taken into account (52%o); H2 is the actual content of active chlorine in the preparation - calcium hypochlorite or bleach (%). In addition, when disinfecting water in a well in winter, the calculated amount of the drug is doubled. To determine the flow rate - the amount of water (in 1 m3) that can be obtained from a well in 1 hour, it is quickly pumped out over a certain period of time.

From it, water is measured, its quantity is measured, and the time it takes to restore the original water level is recorded. Calculate the flow rate of the well using the formula:

Where D is the flow rate of the well (m3/h), V is the volume of pumped water (m3); t is the total time, consisting of the time of pumping and restoration of the water level in the well (min); 60 is a constant coefficient.

Before filling, the cartridge is first kept in water for 3-5 hours, then filled with the calculated amount of a chlorine-containing disinfectant, 100-300 cm3 of water is added and thoroughly mixed (until a uniform mixture is formed). After this, the cartridge is closed with a ceramic or rubber stopper, suspended in the well and immersed in the water column approximately 0.5 m below the upper water level (0.2-0.5 m from the bottom of the well). Due to the porosity of the cartridge walls, active chlorine enters the water.

The concentration of active residual chlorine in the well water is monitored 6 hours after immersion of the dosing cartridge. If the concentration of active residual chlorine in the water is below 0.5 mg/l, it is necessary to immerse an additional cartridge and then carry out appropriate monitoring of the effectiveness of disinfection. If the concentration of active residual chlorine in the water is significantly higher than 0.5 mg/l, remove one of the cartridges and carry out appropriate monitoring of the effectiveness of disinfection. In the future, the concentration of active residual chlorine is monitored at least once a week, also checking microbiological indicators of water quality.

The most common water treatment processes are clarification and disinfection.

In addition, there are special ways to improve water quality:
- water softening (removal of water hardness cations);
- desalting of water (reducing the overall mineralization of water);
- deferrization of water (reducing the concentration of iron salts in water);
- degassing of water (removal of gases dissolved in water);
- water neutralization (removal of toxic substances from water);
- decontamination of water (water purification from radioactive contamination).

Disinfection is the final stage of the water purification process. The goal is to suppress the vital activity of pathogenic microbes contained in water.

Based on the method of influencing microorganisms, water disinfection methods are divided into chemical or reagent; physical, or reagent-free, and combined. In the first case, the desired effect is achieved by adding biologically active chemical compounds to the water; Reagent-free disinfection methods involve treating water with physical influences, while combined ones use chemical and physical influences simultaneously.

Chemical methods of disinfecting drinking water include its treatment with oxidizing agents: chlorine, ozone, etc., as well as heavy metal ions. Physical - disinfection with ultraviolet rays, ultrasound, etc.

The most common chemical method of water disinfection is chlorination. This is due to high efficiency, simplicity of the technological equipment used, low cost of the reagent used and relative ease of maintenance.

When chlorinating, bleach, chlorine and its derivatives are used, under the influence of which bacteria and viruses in the water die as a result of oxidation of substances.

Except main function- disinfection, due to its oxidizing properties and preservative aftereffect, chlorine also serves other purposes - controlling taste and odor, preventing algae growth, keeping filters clean, removing iron and manganese, destroying hydrogen sulfide, discoloration, etc.

According to experts, the use of chlorine gas poses a potential risk to human health. This is primarily due to the possibility of the formation of trihalomethanes: chloroform, dichlorobromomethane, dibromochloromethane and bromoform. The formation of trihalomethanes is due to the interaction of active chlorine compounds with organic substances of natural origin. These methane derivatives have a pronounced carcinogenic effect, which contributes to the formation of cancer cells. When chlorinated water is boiled, it produces a powerful poison - dioxin.

Studies confirm the relationship of chlorine and its by-products with the occurrence of diseases such as cancer of the digestive tract, liver, heart disorders, atherosclerosis, hypertension, and various types of allergies. Chlorine affects the skin and hair, and also destroys protein in the body.

One of the most promising methods for disinfecting natural water is the use of sodium hypochlorite (NaClO), obtained at the point of consumption by electrolysis of 2-4% solutions of sodium chloride (table salt) or natural mineralized waters containing at least 50 mg/l chloride ions .

The oxidative and bactericidal effect of sodium hypochlorite is identical to dissolved chlorine, in addition, it has a prolonged bactericidal effect.

The main advantages of water disinfection technology with sodium hypochlorite are the safety of its use and a significant reduction in environmental impact compared to liquid chlorine.

Along with the advantages of water disinfection with sodium hypochlorite produced at the point of consumption, there are also a number of disadvantages, primarily the increased consumption of table salt due to the low degree of its conversion (up to 10-20%). In this case, the remaining 80-90% of the salt in the form of ballast is introduced with a hypochlorite solution into the treated water, increasing its salt content. Reducing the salt concentration in the solution, undertaken for the sake of economy, increases energy costs and consumption of anode materials.
Some experts believe that replacing chlorine gas with sodium or calcium hypochlorite to disinfect water instead of molecular chlorine does not reduce but significantly increases the likelihood of trihalomethanes formation. The deterioration of water quality when using hypochlorite, in their opinion, is due to the fact that the process of formation of trihalomethanes is extended over time up to several hours, and their quantity, other things being equal, the greater the pH (a value characterizing the concentration of hydrogen ions). Therefore, the most rational method of reducing chlorination by-products is to reduce the concentration of organic substances at the stages of water purification before chlorination.

Alternative methods of water disinfection using silver are too expensive. An alternative method to chlorination was proposed for disinfecting water using ozone, but it turned out that ozone also reacts with many substances in water - with phenol, and the resulting products are even more toxic than chlorophenols. In addition, ozone is very unstable and is quickly destroyed, so its bactericidal effect is short-lived.

Of the physical methods of disinfecting drinking water, the most widespread is the disinfection of water with ultraviolet rays, the bactericidal properties of which are due to their effect on cellular metabolism and, especially, on the enzyme systems of the bacterial cell. Ultraviolet rays destroy not only vegetative, but also spore forms of bacteria, and do not change the organoleptic properties of water. The main disadvantage of the method is the complete lack of aftereffect. In addition, this method requires greater capital investment than chlorination.

The material was prepared based on information from open sources

3. Water as a factor in the spread of diseases of non-infectious etiology.

4. The importance of water and conditions of water supply to the population in the spread of infectious diseases.

6. Microbiological and sanitary-chemical indicators of epidemic safety of drinking water. Standardization of water quality based on microbiological indicators.

7. Indicators characterizing the organoleptic properties of drinking water, hygienic standards.

8. Indicators characterizing the safety and harmlessness of the chemical composition and organoleptic properties of drinking water.

12. Organization of industrial and state sanitary laboratory control over the quality of drinking water.

13. Water filtration. Basic types of filters, principles of their operation.

14. Coagulation of water, its types, conditions and hygienic significance.

15. Disinfection of drinking water: methods and their characteristics.

16. Methods for disinfecting drinking water. Sanitary control over disinfection technology.

17. Factors affecting the effectiveness of chlorination. Chlorination of drinking water according to chlorine requirements.

18. Chlorine-containing preparations, their hygienic assessment. Chlorination with preammonization. Indications and conditions.

19. Disinfection of water with chlorine gas and bleach. Conditions for its implementation.

20. Types of water chlorination. Chlorination of water with post-turnover doses. Superchlorination. Double chlorination. Indications and conditions.

21. Disinfection of drinking water with ultraviolet rays. Conditions for its implementation.

22. Ozonation of drinking water. Indications and conditions.

23. Special methods for improving water quality and their hygienic importance. Desalination, the main methods of its implementation.

24. Reagent-free methods for clarification of drinking water. Types of installations, their design and principles of operation.

26. Fluoridation and defluoridation of drinking water. Indications and conditions for their implementation on water pipelines.

27. Methods and conditions for the preparation of drinking water at the Minsk water treatment plant.

32. Water supply network and its structure. Causes of water pollution and infection in the water supply network, preventive measures.

33. Hygienic characteristics of centralized water supply. Factors influencing the level of water consumption.

34. Hygienic characteristics of non-centralized water supply. Hygienic requirements for the design, equipment and operation of tube and shaft wells, spring wells.

35. Hygienic requirements for water quality for non-centralized water supply.

36. Methodology for disinfecting wells and disinfecting the water in them.

37. Preventive sanitary supervision in the field of water supply to populated areas.

38. Current sanitary supervision in the field of water supply to populated areas.

39. Hygienic characteristics of domestic wastewater. Conditions for their formation and their removal.

40. Mechanical treatment of domestic wastewater. The concept of effluent stability.

76. Methods for neutralizing solid household waste. Basic requirements for neutralization. Mechanical methods of solid waste disposal.

15. Disinfection of drinking water: methods and their characteristics.

Disinfection drinking water means freeing it from viable and virulent microorganisms - bacteria and viruses, as well as from helminth eggs and vegetative forms and protozoan cysts. When water is disinfected to established standards, enough viable saprophytic microorganisms remain in it, but the desire to free water from them has no hygienic justification and is therefore inappropriate from an economic point of view.

Reagent (chemical) methods for disinfecting drinking water:

1. Chlorination

2. Ozonation

3. Application (Ag, Cu, I)

Physical methods for disinfecting drinking water:

1. Boiling

2. Ultraviolet radiation

3. Electropulse method

Free radicals appear in water. low-voltage MER (NIER).

Disinfection efficiency NIER does not depend on the type and concentration of microorganisms, depends little on the composition of the water being treated and is determined by the technical parameters of the process (the operating voltage, the total processing energy density, etc.). The energy intensity of NIER is comparable to that of water ozonation.

Mechanism of bactericidal action NIER is determined by the combined effect of pulsed ultraviolet radiation and free radicals formed in the discharge zone on the enzyme systems of the cell. Disinfection of drinking water by the ESI method is used in autonomous life support systems.

4. Ultrasound disinfection

Most researchers explain the bactericidal effect of ultrasound by the mechanical destruction of bacteria; others, along with mechanical action, note the role chemical reactions caused by ultrasound. There is no single theory explaining the bactericidal effect of ultrasound.

The advantages of ultrasonic water treatment include a wide range of antimicrobial effects, no effect on the organoleptic properties of water, and independence of the bactericidal effect from the physicochemical properties of water. The technological basis for the use of ultrasound in water treatment has not been developed. The constraint remains the difficulty of designing installations with high productivity, sufficient technical reliability in operation and acceptable cost.

5. Radiation disinfection (gamma irradiation)

Ionizing gamma radiation has a pronounced bactericidal effect. In the 60s of the last century, it was proposed to use it to disinfect drinking water. Under the influence of gamma radiation, free radicals are formed during the radiolysis of water, which have a detrimental effect on the bacterial cell.

6. Disinfection using ion exchange resins

16. Methods for disinfecting drinking water. Sanitary control over disinfection technology.

17. Factors affecting the effectiveness of chlorination. Chlorination of drinking water according to chlorine requirements.

On chlorination efficiency influenced by a number of factors related to the biological characteristics of microorganisms (their number), the bactericidal properties of chlorine preparations (dose, exposure time), the state of the aquatic environment (higher t, lower pH, less organic matter - better effect), conditions, which are disinfected.

Clconsum=Clabs+Clost(0.3-0.5 mg/l)

Fig.1. Graph of the dependence of the amount and type of residual chlorine on the administered dose of chlorine

1. consumption of organic Cl (amines)

2. image of organochlorine compounds and chloramines

3. destruction of organochlorine compounds and amines

4. free residual Cl and bound Cl

When disinfecting water in mine wells, according to epidemiological indications, they use bleach CaClO2, which dissociates into Cl + OCl, which is the starting point in water disinfection. After increasing the dose, residual chlorine appears, a control mark for the effectiveness of water disinfection (0.3-0.5 mg/l - 100% effect). – This is a method of chlorination according to chlorine demand.

Boiling water, i.e. heating it to 100 0 C, leads to the unconditional death of all microorganisms, including pathogenic ones. In addition, boiling can destroy some heat-labile toxins (botulinum toxin) and toxic substances. Including OV. For greater guarantee against heat-resistant viruses, it is recommended to continue boiling for 10-15 minutes. The destruction of spore forms is achieved by increasing the boiling time to 2 hours. The same effect can be achieved by heating water to 110-120 o C for 5-10 minutes at excess pressure (autoclaving).

Boiling water as a method of disinfection has a number of advantages over others. These include the simplicity, accessibility and reliability of disinfection, the independence of the bactericidal effect from the composition of the water, and the absence of a noticeable effect on the physicochemical and organoleptic properties of water.

Along with the advantages, the method of water disinfection by boiling also has some significant disadvantages: it is not economically profitable, requires a large amount of fuel and is relatively cumbersome due to low-performance equipment in the form of various types of boilers. In this regard, boiling for the purpose of disinfecting large quantities of water is not used. When treating small volumes of water, it is widely used in both peace and war.

Water disinfection method ultraviolet rays has important advantages, which include a wide antibacterial spectrum of action with the exclusion of spore and viral forms, exposure lasting a few seconds, preservation of the natural properties of water, improvement of working conditions for service personnel due to the exclusion of harmful chemicals - disinfectants - from circulation, and economic profitability.

It has been established that the ultraviolet part of the spectrum has the maximum bactericidal effect, especially rays with a wavelength from 200 to 280 mm (region C).

The disadvantage of the method is the lack of a simple and quick way to control the completeness of water disinfection, as well as the great influence of the physical and chemical properties of water (color, turbidity, iron content, etc.) on the disinfection effect.

4.6.2. Chemical methods of water disinfection

Chemical methods of water disinfection are based on the use of various substances that have a bactericidal effect. These substances must meet certain requirements, namely: not make water harmful to health, not change its organoleptic properties, have a reliable bactericidal effect in small concentrations and within a short time of contact, be convenient to use and safe to handle, be stored for a long time, production they should be cheap and accessible.

Chlorine and its preparations meet these requirements to the greatest extent, which can explain their distribution in the practice of municipal and field water supply.

Other substances are also used to disinfect water - ozone, iodine, hydrogen peroxide, silver preparations, organic and inorganic acids and some others.

Along with positive properties, the chlorination method also has disadvantages. The main one is the inability of chlorine and its preparations in the doses in which they are usually used to destroy spore forms of microorganisms in water. To achieve this goal, they resort to very large doses of chlorine and prolonged contact with water. The disadvantages of chlorination also include the difficulty of dosing and the danger of handling chlorine, the instability of its preparations during storage, the unpleasant odor of chlorinated water, especially if it contains chemicals such as phenols, as well as the possibility of the formation of trihalomethanes.

The effectiveness of water chlorination is determined by the properties of the chlorine-containing preparation, the concentration of active chlorine in it, the physicochemical properties of water and the time of contact of chlorine with it, the degree of contamination of water with microorganisms and their type.

According to most researchers, contact of chlorine with water for 30 minutes is sufficient to destroy the overwhelming number of vegetative forms of microorganisms.

The most reliable way to monitor the effectiveness of water disinfection is bacteriological testing. However, such research is lengthy and complex, especially in field conditions and combat situations. Control over the completeness of disinfection is carried out using residual chlorine. Residual chlorine consists of free and bound. It has been established that if 0.3 - 0.5 mg/l of free residual chlorine remains in chlorinated water 30 minutes after adding a certain amount of chlorine, the water, as a rule, is reliably disinfected.

It is known that, along with free forms of chlorine, combined chlorine, the basis of which is chloramines and dichloramines, enters into the reaction and is taken into account. Their bactericidal effect is many times less than that of free chlorine. Therefore, it is not enough to know only the total amount of residual chlorine. In each specific case, it is necessary to establish its qualitative composition in order to make a correct conclusion about the reliability of the water disinfection carried out. According to the standard, the concentration of bound (chloramine) chlorine after exposure for at least an hour should be 0.8 - 1.2 mg/l.

In cases of epidemiological unfavorability, the value of residual chlorine can be increased to 2 mg/l without harming public health. The residual chlorine is used to determine the chlorine demand of water.

The main methods of chlorination of water are chlorination with normal doses and chlorination with increased doses (hyperchlorination).

Chlorination in normal doses most common, especially in public water supply practice. Its essence lies in choosing a working dose of active chlorine that, after 60 minutes of contact with water, ensures the presence of 0.8 - 1.2 mg/l of residual bound chlorine. The advantages of the method include a relatively small effect on the organoleptic properties of water, which allows the water to be consumed without subsequent dechlorination, and low consumption of chlorine or chlorine-containing preparations. The disadvantages of the method are the difficulty of choosing a working dose of chlorine and the possibility of the appearance of a chlorophenol odor due to the formation of chlorophenols in water containing even very small amounts of acid or its homologues.

At chlorinating water with large doses of chlorine an increased amount of active chlorine is added to it in anticipation of subsequent dechlorination. The dose of active chlorine is selected depending on the physical properties of the water (turbidity, color), the nature and degree of improvement of the water source and the epidemic situation. In most cases it is 20 - 30 mg/l with a contact time of 30 minutes.

The advantages of the method include:

Reliable disinfection effect even for cloudy, colored and ammonia-containing waters;

Simplification of chlorination techniques (no need to determine the chlorine requirement of water);

Reducing the color of water due to the oxidation of organic substances with chlorine and their conversion into uncolored compounds;

Elimination of foreign tastes and odors, especially those caused by the presence of hydrogen sulfide, as well as decomposing substances of plant and animal origin;

Absence of chlorophenol odor in the presence of phenols, since in this case not mono-, but polychlorophenols are formed, which have no odor;

Destruction of certain poisonous substances and toxins (botulinum toxin); destruction of spore forms of microorganisms at a dose of 100 - 150 mg/l of active chlorine and a contact duration of 2-5 hours, significantly improving the conditions for the water coagulation process.

The listed positive aspects of the method make it very valuable for the practice of improving water quality in the field, when the choice of water sources is limited and there is a need to use low-quality water, especially due to the danger of using bacteriological and chemical weapons.

The disadvantages of the method, as already mentioned, include the possibility of the formation of trihalomethanes, especially when chlorinating water containing household waste and humic substances, increased consumption of chlorine and the need to dechlorinate water.

Chemicals that bind excess chlorine and sorption of chlorine on activated carbon are used as dechlorination agents. Chemicals that render chlorine inactive are usually classified as reducing agents. The best of them is sodium thiosulfate (hyposulfite).

Dechlorination of water can be done with sulfur dioxide and sulfur dioxide, as well as by filtration through ordinary or activated carbon. Small amounts of water can be dechlorinated by adding charcoal powder to the water.

Used for water disinfection hydrogen peroxide (H 2 O 2) is also a strong oxidizing agent. The acceptor is atomic oxygen. Due to the difficulty of obtaining in large quantities and the high cost, hydrogen peroxide has not become widely used in water supply practice. Recently, a new, cheaper method of obtaining it has been developed, and therefore this method is gaining practical interest.

Hydrogen peroxide does not change the organoleptic properties of water and significantly (up to 50%) reduces its color, which is very valuable for the disinfection of colored waters. The disadvantages of the method include the need to introduce catalysts to accelerate the release of atomic oxygen and the liquid form of the drug, which complicates its use in field conditions.

Water disinfection silver based on the fact that ions of this metal inactivate bacterial enzymes by blocking their sulfhydryl groups. In practice, the silver disinfection method can be used with small individual and group water supplies. For this purpose, silver-plated sand, silver-plated ceramic “Raschig rings” and silver dissolved electrolytically are used, i.e. a silver electrode (anode) dissolved by passing direct current through disinfected water. In this way, you can get “silver water”, which has bactericidal properties. It is also possible to disinfect water by adding silver salts.

Disinfection of water with silver does not change its organoleptic properties and ensures a long-lasting bactericidal effect, which is especially important in cases where there is a need for long-term storage of water.

The disadvantages of the method include the difficulty of dosing, the slow and unreliable bactericidal effect, the influence of the physicochemical properties of water on the bactericidal effect, as well as the need to control residual amounts of silver in drinking water.