Water disinfection methods include: E

Under the concepts of disinfection and disinfection of drinking water, it is customary to understand a number of complex measures that are aimed at the destruction of various viruses, bacteria, as well as the complete or partial removal of chemical impurities and other substances hazardous to the health of the body from the liquid. Water disinfection can be carried out both at special engineering and technical facilities on an industrial scale, and for local disinfection for quick consumption. In this article, we will consider the main methods of disinfecting drinking water and briefly describe their features.

Before disinfecting water, when choosing a means for disinfecting water, it should be understood that complete purification of water from all bacteria and minerals will make it unsuitable for human consumption. Therefore, choosing a method for disinfecting water, you need to be careful. There are several ways to influence microorganisms harmful to humans:

• Chemical methods of water disinfection (reagent);
• Physical methods (reagentless);
• Combined methods of exposure to microorganisms.

The chemical method includes the use of various coagulant reagents added to water for disinfection. And also this method includes: chlorination, ozonation, the use of silver, silicon, sodium hypochlorite and other substances that can at least stop the reproduction of bacteria, and maximum - completely get rid of them.

Physical, reagent-free impact is made with the use of UV disinfection of water, electropulse and other methods.

Combined methods include both chemical and physical effects alternately. These methods are considered the most effective in disinfecting and cleaning from various impurities contained in water.

Disinfection of water by chemical methods

When using a chemical method of disinfection, it is extremely important to be able to determine or know the exact dosage, as well as the required time of exposure of the substance to water.

The required dose is determined both by trial disinfection and by calculation methods. Both an excess and a lack of a substance can make water unusable.

An example of incorrect dosage: A too small dose of ozone can kill only a part of the bacteria and, by forming special chemical compounds, will create an ideal environment for the reproduction of previously dormant bacteria.

To create a long-term effect of the destruction of microorganisms after disinfection, as a rule, the dose of the reagent is taken in excess. However, such an excess should not be dangerous to humans, since most reagents are quite toxic.

Water chlorination

Chlorine and its derivatives are still used in our country for water disinfection, despite the presence of many modern cleaning methods. This reagent shows good characteristics in terms of disinfection, even with minimal excess. So, at a residual chlorine concentration of 0.5 mg / l, the growth of pathogenic microorganisms in soda does not occur.

However, this reagent has a number of significant disadvantages: a high degree of toxicity, mutagenicity, and carcinogenicity. And even the subsequent purification of water with activated carbon is not able to completely remove the formed chlorine compounds. And if such waters go into the drain and enter the ground or river waters downstream, then the degree of adverse impact on nature is quite large.

The use of chlorine is largely due to the cheapness and availability of this reagent, and a high degree of effectiveness against pathogenic flora, algae growth, and a number of fungi. Under its influence, hydrogen sulfide is destroyed, iron and manganese are removed. It has the ability to bleach, making chlorine the main ingredient in most bleaches.

Chlorine dioxide has a greater effect on viruses and bacteria than ordinary chlorine, but pollutes the environment much less. But, this reagent is quite expensive and requires preparation directly at the place of use.

Chlorine forms so-called trihalomethanes (methane derivatives), which have a strong carcinogenic effect on the human body, leading to the growth of cancer cells. And when boiling water, under the influence high temperatures, dioxin is formed - a very strong poison.

As a result of research by scientists from different countries showed that chlorine itself and its derivatives can cause all sorts of disorders and diseases of the internal organs of people from the side: the gastrointestinal tract, the cardiovascular system, the liver, and the kidneys. Destroy protein in the body, cause atherosclerosis, hypertension, all kinds of allergic manifestations. Detrimental to skin and hair.

Water ozonation

Ozonation, by decomposing ozone particles in water, forms atomic oxygen. As a result, the enzyme system of the microbial cell is destroyed. In addition, some of the compounds are oxidized, which causes a rather unpleasant odor, metal corrosion is accelerated (including kitchen utensils, plumbing systems, etc.). Therefore, when applying ozone, an accurate dosage is needed.

At the same time, this method is considered the best of the chemical ones, providing the fastest and safest water disinfection for the environment and humans.

This method requires special expensive equipment, high power consumption, as well as highly qualified service. All this makes this expensive method of disinfection applicable mainly in centralized water supply.

This is due to the fact that ozone is dangerous in the production process, explosive and toxic. Therefore, high-quality professional maintenance of such equipment or installations is extremely important.

In addition, recent studies have shown that ozonation alone is not enough for high-quality disinfection of water, since after its exposure, the decomposition of phenolic groups of humic substances begins. These substances contribute to the activation of previously "sleeping" microorganisms.

Water treated with ozone is transported in special containers made of certain types of plastic, asbestos cement, concrete, etc. Before putting such water through pipes and other metal containers, it is necessary to wait for the period of ozone decay.

Antiseptics, polymer reagents

Disinfection with polymeric reagents related to polymeric antiseptics is a separate method of water purification. Biolag is the best known of this class of reagents. Compared to ozone and chlorine, Biolag has a number of advantages:

• Does not harm health;
• Does not cause local irritation to the skin and mucous membranes;
• Does not cause allergic reactions;
• After purification, the water has no taste, smell and color;
• Does not spoil the fabric (swimming suits);
• Does not have a corrosive effect on metal surfaces;
• It has a long-term disinfection effect.

Other reagents

Disinfection with the help of reagents requires certain specific knowledge, since in this method the dosage tone and other calculations are important. A variety of heavy metal compounds are used, such as iodine, bromine, etc. This method is isolated separately as oligodynamic water disinfection.

When noble metals are used to purify water, for example, with the help of silver, there is not complete disinfection, but a temporary inhibition of the growth of the number of bacteria. In addition, with this method, it is extremely important to observe the dosage, since silver tends to accumulate in the human body and is very slowly and difficult to remove.

Other, more rare reagents, such as strong oxidizing agents (sodium hypochlorite), are used in cases where water values ​​change frequently and are highly unstable. An example of the instability of water is the presence in it of organic substances, plankton. In terms of chemical and bactericidal properties, sodium hypochlorite is similar to chlorine, but it is not so harmful to the human body and the environment, it has a long bactericidal effect. This reagent is obtained by electrolysis of a 2-4% solution of sodium chloride (common salt) or mineralized waters.

disadvantage this method It is believed that the removal of salt from water takes much more energy than chlorination. However, the undeniable advantage can be called safety for humans and the environment.

Disinfection of water by physical methods

Physical methods include exposure to ultrasound, disinfection of water with ultraviolet light and other methods. At the same time, preliminary filtration, coagulation of water is carried out in order to remove suspensions, helminth eggs and various microorganisms.

UV cleaning

For UV disinfection of water, the volume of liquid is calculated in order to calculate the required energy costs. To ensure efficiency, it is necessary to calculate the radiation power and exposure time, as well as take into account the degree of infection with bioorganisms (the number of microbes per 1 ml of water).

Determine the presence of BGKP (indicator bacteria belonging to the group of Escherichia coli). These bacteria are present in water contaminated with faecal matter and are extremely resistant to any disinfection processes. According to SanPiN 2.1.4.1074-01, the maximum allowable number of colipoma bacteria should not exceed 50 per 100 ml of liquid.

Ultraviolet disinfection has a more effective effect on various bioorganisms than chlorine. And with the ozonation method, in terms of cleaning efficiency, UV disinfection is approximately equal in efficiency.

Ultraviolet rays affect the enzyme systems of bacterial cells and cell metabolism. UV rays are able to destroy vegetative and spore bacteria, in the fight against which other methods are not very effective. At the same time, the taste, color and smell of water do not change, toxic substances, an overdose of exposure is not possible.

However, this method has its drawback - the lack of aftereffect. At the same time, there is an indisputable plus - small installations for individual use at the cost of the process are on a par with chlorination, and are cheaper than ozonation. What makes this method applicable for use in private homes.

In order for this disinfecting method to remain effective, it is necessary to monitor the cleanliness of quartz lamps, which can accumulate mineral salt deposits. To solve this problem, food acid (vinegar, citric acid) is added to the water, and this solution is circulated through the system. In particular, vinegar copes very well with the problem of salt deposits. You can also apply mechanical cleaning of the surface of the lamps.

It should be noted that water treatment with ultraviolet radiation is carried out only after preliminary purification of water from substances capable of shielding the rays. The wavelength of radiation can vary from 200 to 295 nm, but the most commonly used optimal value is 260 nm, at which the cytoplasm of cells is actively destroyed. The service life of one UV lamp is about several thousand hours of continuous operation.

To date, ultraviolet radiation is the most effective method of disinfecting water.

Ultrasonic water treatment

Ultrasonic water treatment is based on physical phenomenon- cavitation, that is, the ability to form voids that create a difference in pressure. Such dissonance leads to the death of bacteria as a result of rupture of cell membranes. This effect depends on the degree of intensity of sound vibrations. Ultrasonic cleaning units require qualified maintenance and are quite expensive.

Magnetostrictive or piezoelectric devices create a sound frequency of 48,000 Hz. At lower frequencies, the growth of bacteria not only does not stop, but also intensifies, so the accuracy of tuning and high-quality maintenance of such equipment is mandatory. Boiling water

Disinfection of water by boiling

Boiling is the most popular and widespread household method of water disinfection, during which (depending on the duration of the process) a huge number of pathogens die: bacteria, bacteriophages, viruses, etc. Gases dissolved in water are also eliminated, hardness (pH) decreases, while taste qualities practically do not change.

Integrated water purification methods

An integrated approach to cleaning includes both reagent methods and non-reagent methods. Water can be disinfected, for example, first with UV rays, and then, the disinfected volume of liquid, treated with chlorine. As a result, harmful microorganisms are eliminated, and secondary infection is excluded.

Combined methods save money on reagents and improve water quality.

Similarly, water can be disinfected first with ozone, and then chlorinated. In this case, the content of toxic compounds containing chlorine in the water is sharply reduced.

Filtration shows good results only when the disinfected volume of water passes through cells smaller than microorganisms. And given that most bacteria are about 1 micron in size, and viruses are even smaller in size, then in order to disinfect water, filter elements must have pores of 0.1-0.2 microns.

Purifier-type systems include several water purification systems at once with a fairly effective filtration system. Such equipment has a wide range of applications and is popular both at home and in office premises.

New water disinfection systems

Relatively new means of water disinfection: electropulse and electrochemical method. The bottom line is that water is passed through a diaphragm electrochemical reactor, which is separated by a metal-ceramic membrane. This membrane is capable of ultrafiltration to the cathode and anode region. After applying current to the anode and cathode chambers, alkaline and acidic solutions are formed, and, as a result, electrolytic formation, the so-called active chlorine. Such a water disinfectant can ensure the rapid death of almost all harmful microorganisms.

The electropulse method is capable of disinfecting electric charge, after which there is a shock wave of ultrahigh pressure and light radiation. As a result, ozone is formed, which has a detrimental effect on microorganisms.

New cleaning methods are quite expensive and are not applicable in domestic household conditions due to the complexity of the ongoing processes and the need for constant qualified maintenance.

Note! Sanitary standards do not imply the complete destruction of all microorganisms contained in the water. It is required to remove and neutralize only bacteria, viruses and other inclusions that are dangerous to humans and can cause health problems. Completely sterile water is just as harmful to humans as contaminated with bacteria.

Before carrying out disinfection and making a choice of one or another cleaning method, it is necessary to first analyze the degree of water pollution: mineral, biological compounds and microorganisms. Based on the results of the analysis, the best option for high-quality disinfection and water purification is selected.

Water disinfection methods are classified into physical (non-reagent) and chemical (reagent).

Non-reagent disinfection methods water: boiling, treatment with ultraviolet (UV) radiation, gamma rays, ultrasound, high frequency electric current, etc. Non-reactive methods have advantages because they do not lead to the formation of residual harmful substances in the water.

Boiling within 30 min. applied at local water supply causes not only the death of vegetative forms, which occurs already at 80 0 C for 30 seconds, but also the spores of microorganisms.

Water disinfection shortwave UV radiation(l=250-260 nm) due to photochemical cleavage of the protein components of the membranes of bacterial cells, vibrios and helminth eggs causes rapid death of vegetative forms and spores of microorganisms, viruses and helminth eggs resistant to chlorine. Limitation - the method is not used for water with high turbidity, color and containing iron salts.

Reagent disinfection methods water: treatment with silver ions, ozonation, chlorination.

Silver ion treatment leads to inactivation of enzymes of the protoplasm of bacterial cells, loss of the ability to reproduce and gradual death. Silvering of water can be carried out different ways: filtering water through sand treated with silver salts; electrolysis of water with a silver anode for 2 hours, which leads to the transition of silver cations into water. The advantage of the method is the long-term storage of silvered water. Limitation - the method is not used for water with a high content of suspended organic matter and chlorine ions.

Ozonation based on the oxidation of organic substances and other water pollution by ozone O 3 - an allotropic modification of oxygen, which has a higher oxidizing potential and 15 times greater solubility. Ozone is spent to a greater extent on the oxidation of organic and easily oxidized inorganic substances than on disinfection. The time required for disinfection with ozone is 1-2 minutes. The applied dose of ozone is 0.5-0.6 mg/l. A prerequisite for ozonation is the creation of a residual amount of ozone in water (0.1-0.3 mg/l) to prevent the growth and reproduction of pathogenic microorganisms. The advantage of the method is the absence of residual substances, deodorization of water, removal of color, a short time reactions and destruction of viruses. However, the method requires cheap sources of electricity, since the ozone-air mixture is obtained using an energy-intensive process - a "silent" electric discharge on an ozonizer.

Chlorination- the most affordable and cheapest method of disinfection. Chlorinating agents are divided into 2 classes: 1) anion Cl - (gaseous Cl 2 , chloramine, chloramines B and T, dichloramines B or T); 2) so-called. "active chlorine" - hypochlorite ion = anion ClO - [calcium hypochlorite Ca(OCl) 2 , sodium hypochlorite NaOCl, bleach - a mixture of calcium hypochlorite, calcium chloride, calcium hydroxide and water]. The bactericidal effect is explained by the action of hypochlorous acid, which is formed by the reaction Cl 2 + H 2 O ® HOCl + HCl; active chlorine: HOCl ® OCl - + H + and hydrochloric acid HclO 2. The disinfection mechanism is associated with the interaction of active substances with SH-proteins of the bacterial cell wall. Disadvantages of the method: when chlorinated, anthrax spores, tuberculosis pathogens, eggs and larvae of helminths, amoeba cysts and Burnet's rickettsia remain viable.

Disinfection of water by chlorination requires prior experimental definition the concentration of active chlorine in the chlorinating preparation (normally 25-35%) and the chlorine absorption of water, which depends on the degree of water pollution by organic substances and microorganisms, for the oxidation and disinfection of which chlorine is consumed.

The conditions for effective chlorination are the observance of the duration of contact of the chlorine agent with water and its components (30 minutes in the warm and hot season, 60 minutes in the cold); creation of residual chlorine 0.3-0.5 mg/l. The chlorine absorption of water and the concentration of residual chlorine in the sum are chlorine demand water.

Limitation of the use of water disinfection with preparations containing "active chlorine" applies to water contaminated with industrial wastewater containing phenol and other aromatic compounds, which requires "post-fracture" chlorination, leading to the formation of chlordioxins - substances that are highly toxic and cumulative in the human body. A sign of their formation is a strong "pharmacy" smell of water. Chlorine gas is used to prevent the formation of chlorine dioxide during chlorination of water polluted by industrial effluents. Withpre-ammonization(pretreatment of water with ammonia).

If it is impossible to experimentally determine the chlorine absorption of water, use rechlorination method. Rechlorination is carried out with excess doses of a chlorinating agent (usually in still water of limited volume). When choosing the dose of active chlorine, the type and degree of water pollution in the water supply source and the epidemic situation in the territory where water is collected in the source used are taken into account (usually the dose ranges from 10-20 mg of active chlorine per 1 liter of water).

Introduction

Natural water, as a rule, does not meet the hygienic requirements for drinking water, therefore, before being supplied to the population, it almost always needs to be purified and disinfected. Consumed by a person for drinking, as well as used in various industries, natural water 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 provides its 100% purification from microorganisms. But even if the water treatment system could contribute to the absolute removal of all microorganisms from the 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 norms (SanPiN) do not aim to bring water to an ideal microbiological level, and therefore sterile quality, in which all microorganisms will be absent in it. The task is to remove the most dangerous ones for human health.

The main documents that define the hygienic requirements for the quality of 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 of populated areas. Hygienic requirements for the quality of non-centralized water supply. Sanitary protection of sources.

Currently, there are many methods of water disinfection and many devices used to implement them. The choice of disinfection method depends on many factors: the source of water supply, the biological characteristics of microorganisms, economic feasibility, etc.

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

It is important and necessary that each water user can correctly formulate goals and objectives when choosing a method for disinfecting 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 review of regulatory documents regulating the quality of drinking water in terms of disinfection, adopted in Russia and abroad. abroad.

Water purification, including its discoloration and clarification, is the first stage in the preparation of drinking water, at which suspended solids, helminth eggs and a significant part of microorganisms are removed from it. However, some pathogenic bacteria and viruses enter through sewage 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, its 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 risk of diseases from pathogenic microorganisms present in water is thousands of times higher than when water is contaminated with chemical compounds of various nature.

Based on the foregoing, we can conclude that it is disinfection to the limits that meet the 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-channel, spring. Surface water is river, lake, sea and water from reservoirs.

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

with an underground source of water supply - analyzes of water quality, hydrogeological characteristics of the aquifer used, sanitary characteristics of the area in the water intake area, 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 discharges, compliance with their intended water intake, sanitary characteristics of the basin, industrial development, the presence and possibility of occurrence 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 flow of self-purification processes.

However, the water of open reservoirs is subject to seasonal fluctuations in composition, contains various impurities - mineral and organic matter, 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 matter and bacteria, low salinity and hardness. The sanitary quality of river water is low due to its pollution with sewage from residential towns and cities.

Lake water and water from reservoirs are characterized by a low content of suspended particles, high color and permanganate oxidizability; water bloom is often observed due to the development of algae. Lake water has a different degree of mineralization. These waters are not safe in epidemiological terms.

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

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

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

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

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 purposes of domestic and drinking water supply after desalination.

The use of water from underground sources of water intake 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.

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

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

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

Ground waters are located below soil waters, the depth of occurrence is 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 ground and soil waters, so the quality of soil waters affects the state of groundwater. The composition of groundwater is subject to slight fluctuations and is virtually constant. In the process of filtering through the soil layer, the water is purified from mineral impurities and partially from bacteria and microorganisms. Groundwater is the most common source of water supply in rural areas.

Understream water is water extracted from wells, the depth of which corresponds to the marks of the bottom of a stream, river or lake. Infiltration of river water into the ground layer can occur, these waters are also called underflow. The composition of understream waters is subject to various fluctuations, and is not very reliable in terms of sanitary conditions; and the use of these waters for the water supply system requires purification and disinfection.

A spring is a source of water that flows to the surface on its own. The presence of a spring indicates the presence of a water-resistant layer in the depths, supporting a water-resistant 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 impermeable rocks. The upper waterproof layer protects these waters from the penetration of precipitation and groundwater. Due to the deep occurrence, fluctuations in the composition of the water are insignificant, the waters are the most sanitary in terms of health.

Pollution of interstratal waters occurs extremely rarely: only when the integrity of water-resistant layers is violated 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 ascending 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, while changing its composition.

2. Classification of disinfection methods

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

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

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 are used as chlorine, chlorine dioxide, ozone, iodine, sodium and calcium hypochlorite, hydrogen peroxide, potassium permanganate. Of the above oxidizers practical use in water disinfection systems they find: chlorine, ozone, sodium hypochlorite, chlorine dioxide. Another chemical method - oligodynamia - the impact on water of noble metal ions.

In the case of disinfection of drinking water by a chemical method, in order to achieve a stable disinfecting effect, it is necessary to correctly determine the dose of the injected 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 with an excess (residual chlorine), which guarantees the destruction of microorganisms, even if they enter the water for some time after its disinfection, which ensures a prolonged effect.

Physical disinfection methods:

– ultraviolet irradiation;

– thermal impact;

– ultrasonic influence;

- exposure to electrical discharge.

With physical methods of water disinfection, it is necessary to bring a given amount of energy to a unit of its volume, defined as the product of the exposure intensity (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, that is, their resistance to these effects.

The choice of method, the 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 waterworks and its location (remoteness from consumers), the cost of reagents and disinfection equipment.

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

3. Normative and technical documents of water and sanitary legislation

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

There is a strong possibility that even water from closely spaced sources will vary greatly 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 is necessary when the water quality does not meet the requirements of consumers.

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

Table 1

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

table 2

The safety of water in an epidemic sense is determined by the total number of microorganisms and the number of bacteria of the Escherichia coli group. According to microbiological indicators, water must meet the requirements given in Table. 3.

Table 3

*Indicative parameters of water quality. For monitoring purposes only, Member States may establish additional parameters on their territory or part of it, but their introduction must not impair human health.

**Required parameters.

4. Water treatment with strong oxidizers

Disinfection of water by reagent methods is carried out by adding various chemical disinfectants to the water or by carrying out special events. Application chemical substances in water treatment usually results in the formation of chemical by-products. However, the health risk from their impact is negligible compared to the risk associated with harmful microorganisms that develop in water due to the lack of its disinfection or its poor quality.

The Ministry of Health has authorized the use of more than 200 disinfectants and water sterilizers.

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

4.1. Chlorination

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

But only in the XIX century. it was found that "chlorine water" (as the result of the interaction of chlorine with water was called at that time) also had a disinfecting effect. It can be assumed that chlorine has been used as a disinfectant since 1846, when the practice of rinsing hands with “chlorine water” was introduced for doctors in one of the hospitals in Vienna.

In 1888, at the International Hygiene Congress in Vienna, it was recognized that many contagious diseases can be spread through drinking water, including such a dangerous and widespread one at that time as cholera. In fact, this congress served as an impetus for the search for 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 big cities. For the first time, it was used for this purpose in New York in 1895. In Russia, chlorine was first used for the disinfection of 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) undergoes chlorination. The technological simplicity of the chlorination process and the availability of reagents ensured the widespread introduction of chlorination into the practice of water supply.

The most important advantage of this method of disinfection 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 the introduction of a chlorinating agent into water, it retains its activity against microbes for a very long time, inhibits their enzyme systems along the entire route of water through the water supply networks from the water treatment facility (water intake) to each consumer.

Due to its oxidizing properties and aftereffect, chlorination prevents the growth of algae, promotes the removal of iron and manganese from water, the destruction of hydrogen sulfide, discoloration of water, maintaining the microbiological purity of filters, etc.

4.2. Chlorination Method

When choosing a chlorination method (treatment of water 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 water depending on the season. Special attention should be given to the specific features of the technological scheme of water treatment and equipment that is part of the treatment facilities.

According to the goals, all methods can be divided into two large classes: primary (pre-chlorination, pre-chlorination) and finish (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 goals, primary chlorination serves not only to disinfect water, but also to intensify the processes of water purification from impurities, for example, iron removal, 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.

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

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

Normal chlorination is used when water is taken from sources that are reliable in sanitary terms. Doses of chlorine should provide the necessary bactericidal effect without deteriorating the organoleptic indicators of water quality. Permissible amount of residual chlorine after 30-minute contact of water with chlorine is not higher than 0.5 mg/l.

Rechlorination It is used when taking water from sources characterized by large fluctuations in composition, especially in terms of microbiological indicators, and in the event that normal chlorination does not give a stable bactericidal effect. Also, rechlorination is used in the presence of phenols in the 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 purify water from toxic substances. 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 agent - dechlor (thiosulfate or sodium sulfite, sodium disulfite, ammonia, sulfur dioxide, activated carbon).

Combined methods of chlorination, i.e. water treatment with chlorine together with other bactericidal preparations is used to enhance the action 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 pipes. Combined methods include: chlorination with manganation, 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 application, for example:

- as a result of chlorination in the treated water, organochlorine compounds (OCs) can be formed;

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

- chlorination of water, carried out on a large scale, has caused a wide spread of microorganisms resistant to chlorine;

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

Combined methods of chlorination, water treatment 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 state regulations that limit the content of COS 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, the maximum allowable 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 COS formation is rather complicated, 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 COS in water is the presence organic humic and fulvic acids, as well as algal metabolites. To eliminate these impurities, additional purification of water with carbon filters is subsequently required. The most intensive formation of COS occurs during preliminary chlorination, when large doses of chlorine are fed into untreated water containing a significant amount of organic substances. Currently, there are two main methods for preventing the formation of COS: correction of the chlorination scheme and refusal to use chlorine as the main method of water disinfection.

When correcting the chlorination scheme, the place of input of the main part of chlorine is transferred to the end of the technological scheme of water treatment, which will make it possible to refuse to supply large doses of chlorine to untreated water. When choosing this scheme, an important requirement is the removal organic compounds(precursors of the formation of HOS) before the introduction of chlorine. Avoiding pre-chlorination and moving the main dose of chlorine to the end of the treatment plant is usually enough to solve the problem associated with the formation of COS. However, this leads to a significant decrease in the effectiveness of water disinfection and a decrease in the value of treatment facilities as a barrier.

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

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

For water chlorination, 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 due to 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 is easily soluble in water, after mixing gaseous chlorine with water, an equilibrium is established in an aqueous solution:

HClO H + + OSl -

The presence of hypochlorous acid in aqueous solutions of chlorine and the anions resulting from its dissociation OSl - 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 the light:

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

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

Water treatment 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, the complex transportation and storage of large volumes of highly toxic liquid 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 for conversion into a working form.

The creation of working stocks 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 a solution of sodium hypochlorite (NaClO) 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 United States in 1944, one of the first systems for disinfecting drinking water with chlorine dioxide, the Niagara Falls system, was put into operation. Chlorine dioxide has been used in Germany 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.

The main methods for 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 sodium chlorite solution under vacuum:

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 \u003d 2ClO 2 + 2O 2 + Na 2 SO 4

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

Currently, there are installations that use all these methods for producing chlorine dioxide for its further use in the processes of drinking water disinfection. The main factor hindering the widespread use of chlorine dioxide is its increased explosiveness, which complicates production, transportation and storage. Modern technologies eliminated this drawback 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, and the presence of maintenance personnel is not required. In this regard, it is possible to use it in installations of relatively small productivity.

The use of chlorine dioxide for water disinfection has several 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 with the deviation of the pH value from pH=7.4;

- deodorizes water, destroys phenols - sources of unpleasant taste and smell;

– 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 allowable concentration of chlorites is 0.2 mg / dm 3 with a sanitary and 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 a solution of sodium hypochlorite (NaClO) 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 obtained chemically:

Cl 2 + 2NaOH \u003d NaClO + NaCl + H 2 O

or electrochemical method according to the reaction:

NaCl + H 2 O \u003d 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 \u003d 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 \u003d 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 associated 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 need to be settled, in contrast to 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 the NaClO solution obtained by electrolysis is higher than that of other disinfectants, the active principle of which 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, the sodium hypochlorite solution obtained by the chemical method is produced in the form of three grades. Below are the indicators for the composition of the products.

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

A solution of sodium hypochlorite reagent 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 management used in this case is more cumbersome, which is associated with the need to store large quantities of preparations (3–5 times more than when using chlorine). The volume of traffic increases by the same amount.

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

4.2.5. Chlorination for individual water supply

Plants for the production of active chlorine-containing reagents by electrochemical methods are becoming more 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 by the diaphragm electrolysis of common salt.

The most simple and often the issues of chlorination of water for individual water supply are solved by using sodium hypochlorite, it is possible to use the Whiteness solution as a reagent.

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

Methods of water treatment by chlorination require accurate dosing of reagents into the treated water, since the reagents are characterized by a high chemical activity. To solve the problems of chlorination, it is necessary to use modern digital technology that provides accurate dosing of the reagent in proportion to the flow rate or volume of treated water.

There is a wide variety of dosing pumps on the market with different capacities.

4.3. Other halogens for water disinfection

4.3.1. iodination

Iodine - chemical element from the group of halogens, whose “relatives” are fluorine, chlorine and bromine, is denoted by the symbol I (from the Greek iodes - purple; lat Iodum), has serial number 53, atomic - 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 (about 0.05 mg/l on average). In addition, it is also found in marine sediments. This allows it to pass into groundwater, in which its content can reach more than 100 mg/l. Such a high content of iodine is also typical for areas of oil fields. At the same time, its content in surface waters is low (concentration ranges from 1 to 0.01 µg/l).

Studies show that the iodination method is effective against bacteria and viruses and is not effective enough when exposed to 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 its disinfection cannot compete with traditional chlorination, despite the fact that iodine, unlike chlorine, has such advantages as inertness with respect to ammonia and its derivatives, as well as resistance to solar radiation. Treatment of water with iodine for the purpose of disinfection has not found wide distribution, although attempts have been made repeatedly to iodize tap water. Currently, water treatment with iodine is used only at low flow rates or in cases where special water disinfection schemes are used. So, in some cases, iodine is used to disinfect water in swimming pools.

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

Not so long ago, iodized drinks and bottled water appeared on the market. This approach is undoubtedly justified, since only the consumer, 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. When water passes through them, iodine is gradually washed out of the ion exchanger, passing water. Such a solution is possible only for small-sized individual installations in domestic water purification systems. In such systems, water iodization is carried out due to the additional installation of a special filter element in one of the purification stages. Significant disadvantages are the change in the concentration of iodine during operation, the impossibility of accurate dosing into running water and the lack of control of its concentration.

On the Russian market there are installations and cartridges "Geyser" and "Pure Water".

4.3.2. Bromination

The 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, denoted by the symbol Br (from Greek bromos - stench; the name is associated with the unpleasant smell of bromine; lat. Bromum) has serial number 35, atomic weight - 79.90, liquid density - 3.11 g / cm 3, boiling - 59.2 ° С.

Bromine acts on microorganisms, kills viruses, bacteria, fungi, helps to 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 treatment and is mainly used for water disinfection in small pools and spas.

4.4. Ozonation

4.4.1. History of ozonation

In 1840, the German scientist Sheinbein, investigating 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 applications 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 Nice, and in 1916 there were 26 ozonation plants (total in Europe – 49).

In Soviet times, ozonation was implemented at the Eastern Waterworks in Moscow, the station was equipped with ozonizers from the French company Trailley Gas.

4.4.2. Getting ozone

Ozone (O 3) is a bluish or pale purple gas that spontaneously decomposes in air and in aqueous solution, turning into ordinary oxygen (O 2). The rate of ozone decay sharply increases 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 ozone dose is taken equal to 1-3 mg / l, for underground water– 0.75–1 mg/l. With the introduction of ozone for decolorization and disinfection of polluted 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, the oxidation of phosphorus, etc.

The most economical industrial method for producing ozone is exposure to air or oxygen with an electric 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 is therefore easy to separate. 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 take place in upper layers atmosphere, where the ozone layer is formed and maintained by the action of solar radiation.

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

3H 2 SO 4 + 3BaO 2 \u003d 3BaSO 4 + O 3 + 3H 2 O.

4.4.3. The disinfecting effect of ozone

With increased bacterial contamination of the water source or in the presence of pathogenic microorganisms, enteroviruses and lamblia cysts resistant to the action of 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 applied doses of both reagents).

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

The absence of chemical substances in the water that quickly react with ozone allows efficient destruction of E. coli at a concentration of dissolved ozone of 0.01–0.04 mg/l.

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

It should be noted such an important property of ozone as an antiviral effect. Enteroviruses, in particular those excreted from the human body, end up in wastewater and therefore can often end up in surface waters used for drinking water supply.

As a result of numerous studies, it has been established that residual ozone in the amount of 0.4-1.0 mg / l, stored for 4-6 minutes, ensures the destruction of pathogenic viruses, and in most cases such an effect is quite enough to eliminate all microbial contamination.

Compared to the use of chlorine, which increases the toxicity of treated water, determined by aquatic organisms, the use of ozone helps to reduce toxicity.

4.4.4. hardware design

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

The method of water ozonation 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 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.

In the Russian market, household ozonizers are represented by models: AquaMama, Ecotronics, Ozone Lux (RUIQI, consists of an ozonator and a carbon filter), etc.

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

4.4.5. Features of ozonation

From a hygienic point of view, ozonation is one of the better ways disinfection of drinking water. With a high degree of disinfection, it provides 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 a person from it. Residual ozone quickly turns into oxygen (O 2) and enriches the water with it.

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

Principal technological scheme of water ozonation: 1 – source water reservoir; 2 - pump; 3 - mass transfer apparatuses; 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 appropriate restrictions on its use:

1. The ozonation method is technically complex, requires large amounts of electricity and the use of sophisticated equipment, which requires highly qualified maintenance.

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

3. Ozonation can cause (especially in high-color waters and waters with a large amount of "organics") the formation of additional precipitation, so after ozonation it is necessary to provide water filtration through active 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 also appear.

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

5. Oligodynamia

Oligodynamia is the effect of noble metal ions on microbiological objects. Speaking of oligodynamia, as a rule, three metals are considered - gold, copper and silver. The most common method for practical purposes is the use of silver, sometimes copper-based bactericidal solutions are used. Gold does not find real use in practice, since this metal is very expensive.

5.1. Silver

Silver is a chemical element, belongs to the noble metals, denoted by the symbol Ag (from 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 ° С, boiling point - 2210 ° С.

Despite the fact that silver ores are scattered all over 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 state of kings was judged by the amount of silver. In the Middle Ages, silver and its compounds were very popular among alchemists. Later, silver is used to make dishes, mint coins, make jewelry, and is now used in the manufacture of electrical contacts and printed circuits, power supplies.

The bactericidal action of silver has also been known since ancient times. In ancient Hindu treatises, there is a description of the rite of short-term immersion of red-hot silver in a container of water.

The founder of the scientific study of the mechanism of action of silver on the microbial cell is the Swiss scientist Karl Negel, who in the 80s. 19th century found that the interaction of silver ions (and not the metal itself) with the cells of microorganisms causes their death. He called this phenomenon oligodynamia (from the Greek "oligos" - small, trace and "dynamos" - action, that is, the action of traces). The German scientist Vincent, comparing the activity of some metals, found that silver has the strongest bactericidal effect, copper and gold have less. So, the diphtheria bacillus died on a silver plate after three days, on a copper one - after six days, on a gold one - after eight.

5.1.2. Description of the method

A great contribution to the study of the antimicrobial properties of "silver" water, its use for the disinfection of drinking water and food products was made by Academician L. A. Kulsky. His experiments, and later the work of other researchers, proved that it is metal ions and their dissociated compounds (substances that can decompose 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 a bactericidal, antiviral, pronounced antifungal and antiseptic effect and serves as a highly effective disinfectant against pathogenic microorganisms that cause acute infections. The effect of destroying bacteria with silver preparations is very high. It is 1750 times stronger than concentrated carbolic acid and 3.5 times stronger than sublimate. According to the academician of the Academy of Sciences of the Ukrainian SSR L. A. Kulsky, the effect of "silver" water (at the same concentrations) is more significant than the effect of chlorine, bleach, sodium hypochlorite and other strong oxidizing agents. According to scientific data, only 1 mg / l. silver within 30 minutes caused complete inactivation of influenza viruses A, B, Miter and Sendai. 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, be sure to 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”, the content of silver 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 insist 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 water purification from microorganisms?

"Silver" water has bactericidal properties, at sufficiently high concentrations of silver, about 0.015 mg/l. At low concentrations (10 -4 ... 10 -6 mg / l.), silver has only a bacteriostatic effect, that is, it stops the growth of bacteria, but does not kill them. Spore-forming varieties of microorganisms are practically insensitive to silver. Therefore, old-fashioned infusion of water 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, therefore, somewhat limit the use of silver. It may be appropriate only for the purpose of preserving the original clean water for long term storage (eg. spaceships, hiking, or bottling bottled drinking water). Silver plating of cartridges based on activated carbon is used in household filters. This is done to prevent microbial fouling of the filters, as filtered organic matter is a good breeding ground for many bacteria.

5.1.3. Mechanism of influence

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 bacterial cells that have a negative charge and positively charged silver ions during the adsorption of the latter by a bacterial cell.

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

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

There is an opposite opinion that silver does not have a direct effect on cell DNA, but indirectly, increasing the amount of intracellular free radicals, which reduce the concentration of intracellular active oxygen compounds. It is also assumed that one of the reasons for the broad antimicrobial action of silver ions is the inhibition of the transmembrane transport of Na + and Ca ++ .

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

Colloidal silver is a product consisting of microscopic silver particles suspended in demineralized and deionized water. Colloidal silver, which is obtained by the electrolytic method, is a natural antibiotic approved for use in the United States by the Federal Commission on Food and Drugs back in 1920. The effectiveness of the bactericidal action of colloidal silver is explained by its ability to inhibit the work of the enzyme, which ensures the oxygen exchange of foreign protozoa, therefore they die due to a disruption in the supply of oxygen 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 appliances - ionators. The principle of operation of the silver ionizer is based on the electrolytic method. Structurally, the device consists of an electrolytic cell with silver electrodes (silver Ср 99.99) and a power supply unit connected to the direct current 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 strength depends on the operating time of the power source and the volume of treated water. If you correctly select an ionizer, then the residual content of silver dissolved in water will not exceed the limiting dose of 10 -4 ... bacteriostatic water treatment. In table. 4 shows the conditions for obtaining "silver" water using the example of the LK-41 ionator (the ionator power source is an AC power supply with a voltage of 220 V, load current, mA 0 ± 20%, mass of silver transferred by the ionator into an aqueous solution in 1 minute, mg 0.4±20%, treated water temperature from 1 to 40 °С).

Table 4

Ready-made solutions of silver must be stored in a dark place or in an opaque sealed container, since in the light silver ions are reduced to metal, the solution darkens, and silver precipitates.

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

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

During the operation of the ionizer, 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 destruction of bacteria does not occur immediately, but during the time indicated 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, food industry, and chemical technology processes. The main purpose of coal is the adsorption of organic compounds. It is the filtered organic matter that is the ideal breeding ground for bacteria to multiply when the movement of water stops. Applying silver to activated carbon inhibits the growth of bacteria inside the filter due to the bactericidal properties of this metal. The technology of applying silver to the surface of the coal is unique in that silver is not washed off the surface of the coal during the filtration process. Depending on the manufacturer, type of feedstock, coal grade, 0.06–0.12 wt % silver is applied to the surface.

On the Russian market there are activated carbons coated with silver from manufacturers: 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; coal grades KAUSORB-213 Ag and KAUSORB-222 Ag are obtained from active carbons grades KAUSORB-212 and KAUSORB-221, etc.

Despite the rather high efficiency of oligodynamia in general, one cannot speak of 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, passed through such a filter, the water usually retains its bactericidal properties and purity for a long time.

5.2. Copper

Copper is a chemical element, denoted 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, valence - I, II, density - 8.92 g / cm 3, melting point - 1083.4 ° C, boiling point - 2567 ° C.

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

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

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

Some copper compounds can be toxic when the maximum allowable concentrations in food and water are exceeded. The content of copper 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 the substance for which the standard is established is sanitary-toxicological.

The level of copper in drinking water is usually quite low at a few micrograms per litre. Copper ions give the water a distinct "metallic taste". The threshold of sensitivity 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. V ancient Russia for medical purposes, the so-called "bell" water was used. They received it during the casting of bells, when the hot casting was still cooled in containers filled with water. 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 was enriched with copper, tin and silver ions.

The combined action 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 uncontrollably, 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 outdoor conditions, enriching the water with copper ions.

From ancient times it was also noticed that the water stored or transported in copper vessels was of a higher quality and did not deteriorate for a long time, in contrast to the water contained or transported in vessels made of other materials (visible formation of mucus did not occur in such water).

There are a huge number of research papers confirming the bactericidal properties of copper.

5.2.2. Mechanism of influence

Studies to elucidate the mechanism of the antibacterial action of copper were carried out in ancient times. For example, in 1973, scientists from the Columbus Battell 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.

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

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

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

In 2008 after lengthy research federal agency The United States Environmental Protection Agency (US EPA) officially awarded copper and several of its alloys the status of 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 for water disinfection in household and field conditions, enriching water with copper ions.

There are several types of ionators 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. At the same time, gold is applied in a thin layer on a special electrode substrate; it makes no sense to make an electrode entirely from gold alone, therefore the inner part of the electrode is made of an alloy of copper and silver in a certain ratio, as a rule, alloy 17/1. Structurally, this can be a simple copper-silver alloy plate (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 in the range of wavelengths from 10 to 400 nm is called ultraviolet.

For the disinfection of natural and waste water, a biologically active region of the UV radiation spectrum with a wavelength of 205 to 315 nm, called bactericidal radiation, is used. The greatest bactericidal action (maximum virucidal action) has electromagnetic radiation at a wavelength of 200–315 nm and a maximum manifestation in the region of 260 ± 10 nm. Modern UV devices use radiation with a wavelength of 253.7 nm.

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

The UV disinfection method has been known since 1910, when the first artesian water treatment stations were built in France and Germany. The bactericidal action of ultraviolet rays is explained by the photochemical reactions occurring under their influence in the structure of the DNA and RNA molecules, which form the universal information basis of the reproducibility mechanism 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 eventually leads to their death.

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

The degree of inactivation or the percentage of microorganisms killed by UV radiation is proportional to the intensity of the radiation and the time of exposure.

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

Scheme of installation for UV disinfection of water

6.2. Radiation dose

The main factors affecting the effectiveness of natural and waste water disinfection by UV irradiation are:

- the sensitivity of various viruses to the action of UV radiation;

- lamp power;

- the degree of absorption of UV radiation by the aquatic environment;

- the level of suspended solids in the disinfected water.

Different types of viruses under the same irradiation conditions are distinguished by the degree of sensitivity to UV radiation. The radiation doses required to inactivate certain types of 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 physicochemical properties of the treated water, as well as the thickness of its layer. To take into account this weakening, the water absorption coefficient is introduced

Disinfection of drinking water is understood as measures to destroy bacteria and viruses in water that cause infectious diseases. According to the method of impact on microorganisms, methods of water disinfection are divided into chemical, or reagent; physical, or reagentless, and combined. In the first case, the proper effect is achieved by introducing biologically active chemical compounds into the water; non-reagent methods of disinfection involve the treatment of water by physical influences, and in combined methods chemical and physical influences are used simultaneously.

Chemical methods of disinfecting drinking water include its treatment with oxidizing agents: chlorine, ozone, etc., as well as heavy metal ions. For physical - disinfection with ultraviolet rays, ultrasound, etc. Before disinfection, water is usually purified by filtration and (or) coagulation, which removes suspended solids, helminth eggs and a significant part of microorganisms.

The method of water ozonation is technically complex and the most expensive. The technological process includes successive stages of air purification, its cooling and drying, ozone synthesis, mixing of the ozone-air mixture with treated water, removal and destruction of the residual ozone-air mixture, and its release into the atmosphere. All this also requires additional auxiliary equipment (ozonizers, compressors, air dryers, refrigeration units, etc.), bulk construction and installation works.

Ozone is toxic. The maximum allowable content of this gas in the air of industrial premises is 0.1 g/m 3 . In addition, there is a danger of an explosion of the ozone-air mixture.

It should be noted that, although a number of foreign companies offer autonomous ozonation units for organizing water supply to an individual cottage or water purification in a pool, in addition to the very high cost of such devices, it is required to ensure their high-quality service. The use of an installation offered by one of the domestic companies for autonomous water supply without any systems for monitoring the ozone content in air and water can end sadly for its owners. Under these conditions, it is possible to use the dosing of hypochlorite into water, obtained in a small-sized electrolyzer of the Sanator type, although qualified maintenance is also required here.

The use of heavy metals (copper, silver, etc.) for the disinfection of drinking water is based on the use of their "oligodynamic" properties - the ability to have a bactericidal effect in low concentrations. These metals can be introduced in the form of salt solutions or by electrochemical dissolution. In both these cases, indirect control of their content in water is possible. It should be noted that MPCs of silver and copper ions in drinking water are quite strict, and the requirements for water discharged into fishery reservoirs are even higher.

Chemical methods for the disinfection of drinking water also include widely used in the early 20th century. o disinfection with bromine and iodine compounds, which have more pronounced bactericidal properties than chlorine, but require more sophisticated technology. In modern practice, for the disinfection of drinking water by iodization, it is proposed to use special ion exchangers saturated with iodine. When water is passed through them, iodine is gradually washed out of the ion exchanger, providing the required dose in water. This solution is acceptable for small-sized individual installations. A significant disadvantage is the change in the concentration of iodine during operation and the lack of constant monitoring of its concentration.

The use of active carbons and cation exchangers saturated with silver, for example, C-100 Ag or C-150 Ag from Purolite, does not aim to “silver” the water, but to prevent the development of microorganisms when the flow of water stops. When stopping, ideal conditions are created for their reproduction - a large amount of organic matter retained on the surface of the particles, their huge area and fever. The presence of silver in the structure of these particles dramatically reduces the likelihood of contamination of the loading layer. Silver-containing cation exchangers developed by OAO NIIPM - KU-23SM and KU-23SP - contain a much larger amount of silver and are designed for water disinfection in small-capacity installations.

From physical methods of disinfectiondrinking water the most widespread disinfection of water ultraviolet rays, the bactericidal properties of which are due to the 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. It is important to note that since UV irradiation does not form toxic products, there is no upper dose threshold. By increasing the dose of UV radiation, the desired level of disinfection can almost always be achieved.

The main disadvantage of the method is the complete absence of aftereffect.

The organization of the process of UV disinfection requires more capital investments than chlorination, but less than ozonation. Lower operating costs make UV disinfection and chlorination comparable in economic terms. Energy consumption is negligible, and the cost of annual lamp replacement is no more than 10% of the installation price. For individual water supply, UV installations are the most attractive.

A factor that reduces the efficiency of UV disinfection units during long-term operation is the contamination of quartz lamp covers with deposits of organic and mineral composition. Large installations are equipped with an automatic cleaning system that performs washing by circulating water through the installation with the addition of food acids. In other cases, mechanical cleaning is used.

Ultrasonic disinfection of drinking water based on the ability to cause the so-called. cavitation - the formation of voids that create a large pressure difference, which leads to rupture of the cell membrane and death of the bacterial cell. The bactericidal effect of ultrasound of different frequencies is very significant and depends on the intensity of sound vibrations.

Of the physical methods of individual water disinfection, the most common and reliable is boiling, in which, in addition to destroying bacteria, viruses, bacteriophages, antibiotics, and other biological objects often found in open water sources, gases dissolved in water are removed and water hardness is reduced. The taste qualities of water during boiling change little.

In many cases, the most effective complex application of reagent and non-reagent methods of water disinfection. The combination of UV disinfection with subsequent chlorination in small doses provides both the highest degree of purification and the absence of secondary biocontamination of water. Thus, the treatment of pool water with UV irradiation in combination with chlorination achieves not only a high degree of disinfection, a decrease in the threshold concentration of chlorine in water, but also, as a result, significant savings in chlorine consumption and an improvement in the situation in the pool itself.

Similarly, the use of ozonation is spreading, in which the microflora and part of the organic pollution are destroyed, followed by gentle chlorination, which ensures the absence of secondary biocontamination of water. At the same time, the formation of toxic organochlorine substances is sharply reduced.

Since all microorganisms are characterized by a certain size, passing water through a filter partition with pore sizes smaller than microorganisms can completely purify water from them. So, filter elements having a pore size of less than 1 micron, according to the current
TI 10-5031536-73-10 for non-alcoholic products are considered sterilizing, i.e. sterilizing. Although only bacteria are removed from the water, not viruses. For more “fine” processes, when the presence of any microorganisms is unacceptable, for example, in microelectronics, filters with pores no larger than 0.1–0.2 μm are used.

Sufficiently new methods of water disinfection are electrochemical and electropulse. The Emerald, Sapphire, Aquamin, etc. units are serially produced. Their operation is based on passing water through an electrochemical diaphragm reactor, divided by an ultrafiltration ceramic-metal membrane into the cathode and anode regions. When applying direct current in the cathode and anode chambers, the formation of alkaline and acidic solutions, the electrolytic formation of active chlorine occurs. In these environments, almost all microorganisms perish and partial destruction of organic contaminants occurs. The design of a flow-through electrochemical element is well developed, and a set of a different number of such elements is used to obtain installations of a given capacity. In addition, they are used to obtain disinfectant solutions - catholyte and anolyte, used in medical practice. As for the developers' statements about changing the structure of water and its miraculous properties, let's leave it without comment.

With an electrical impulse, an electric discharge is produced in water - an electro-hydraulic shock, the so-called. effect of L. A. Yutkin. When discharged, a shock wave of superhigh pressure occurs, light radiation and ozone is formed. These factors have a detrimental effect on biological objects in water.

Disinfection and disinfection of water is one and the same process. It is aimed at the complete or partial destruction of viruses, bacteria contained in the liquid, cleaning it from dust, debris, etc. The purpose of the event is to protect people from viral and infectious diseases, food poisoning, and helminthic invasion. In the article, we will introduce you to several methods of water disinfection - traditional and innovative, industrial and suitable for use in the field.

Cleaning methods

First of all, we note the fact that the complete purification of all the elements contained in it (including bacteria) will make the liquid completely unsuitable for drinking and cooking. That is why it is necessary to properly choose the method of water disinfection, to be sure of its high-quality implementation.

Disinfection should always be preceded by a chemical and biological examination of the liquid. Based on its results, one of the disinfection methods is chosen:

• Chemical, reagent.
• Combined.
• Reagentless, physical.

Each of them is a way of disinfecting water, but according to its own specific method. For example, chemical is exposure with the help of coagulant reagents, physical methods are non-reagent exposure. There are also innovative ones, which we will definitely analyze throughout the material.

It is interesting to use combined methods - this is the use of both physical and chemical cleansing alternately. It is considered today the most effective in disinfection - not only allows you to get rid of bacteria, but also helps to prevent their repeated visit. The use of several methods of water disinfection is also a guarantee of its purification from the maximum amount of pollutants.

Chemical methods

In particular, this is the treatment of a liquid with various substances - chemical coagulants. The most common:

• chlorine;
• ozone;
• sodium hypochlorite;
• metal ions, etc.

The effectiveness of these methods of drinking water disinfection depends on the most accurately determined dose of the acting reagent, on the proper time of its contact with the treated liquid.

The appropriate dosage is determined both by the calculation system and by the trial disinfection, after which the water is taken for analysis. It is important not to miscalculate in the sense that a small dose of chemical reagents is not only powerless against viruses and infections, but can also help increase their activity. For example, the same ozone in small quantities kills only part of the bacteria, releasing special compounds that awaken dormant microorganisms, stimulating them to accelerate reproduction.

Hence, the dose is always calculated in excess. But one thing - ways and another thing - drinking. The excess must, in the latter case, be such as not to cause poisoning of disinfectants in people who consume the liquid.

We invite you to learn more about the chemical method.

Chlorination

If you ask the townsfolk: "Indicate the easiest way to disinfect water," many will immediately note chlorination. And for good reason - as a method of disinfection, it is very common in Russia. This is explained by the undoubted advantages of chlorination:

• Easy to use and maintain.
• Low price of the active ingredient.
• High efficiency.
• The subsequent effect after application - the secondary growth of microorganisms does not occur even with a minimal excess dose of chlorine.
• Control over the smell, taste of water.
• Keeping filters clean.
• Prevention of algae formation.
• Destruction of hydrogen sulfide, removal of iron and manganese.

However, the tool also has its drawbacks:

• When oxidized, it has a high degree of toxicity, mutagenicity, and carcinogenicity.
• The subsequent purification of the liquid with activated carbon after chlorine does not completely save it from the compounds formed by chlorination. Highly resistant, they can make drinking water undrinkable, litter rivers and other natural waterways downstream.
• The formation of trihalomethanes, which have a carcinogenic effect on the human body. They are what promote the growth of cancer cells. And boiling, the easiest way to disinfect water, exacerbates the situation. Dioxin, a dangerous toxic substance, is formed in the chlorinated liquid after it.
• Studies show that chlorinated water also contributes to the development of diseases of the vessels, gastrointestinal tract, liver, heart, hypertension, and atherosclerosis. Negatively affects the condition of the skin, hair and nails. Breaks down protein in the body.

Today, a modern replacement is more effective in disinfection. But a significant disadvantage is that it must be applied immediately at the place of production.

Ozonation

Many consider ozonation to be the most reliable way to disinfect water. Ozone gas is able to destroy the enzyme system of microbial, viral cells, oxidize some compounds that give the liquid an unpleasant odor.

The advantages of the method are as follows:

• Fast disinfection.
• The most safe disinfection for humans and the environment.

At the same time, ozonation has a number of disadvantages:

• If the dosage is incorrect, the water has an unpleasant odor.
• Excess ozone contributes to increased corrosion of the metal. This also applies to water pipes, and household appliances, dishes. It is necessary to wait for the period of gas decay before letting water through the pipes.
• A rather expensive method to use - it requires large waste of electricity, sophisticated equipment, highly qualified service personnel.
• The gas in the production process is toxic and explosive. Belongs to the first class of danger.
• After ozonation, bacteria can re-grow. There is no guarantee of 100% water purification.

Polymer antiseptics

Another popular chemical method is the use of polymeric reagents. The most famous today is Biopag. Most often it is used in public pools, water parks.

Advantages of this method of purification and disinfection of water:

• Does not harm human and animal health.
• Does not impart a particular odor, taste, or color to water.
• Pretty easy to use.
• Does not corrode metal.
• Does not cause allergic reactions.

Disadvantages - may irritate the skin, mucous membranes.

Other chemical methods

What methods of water disinfection can be called in this case? These are several options:

• Disinfection with heavy metal ions, iodine, bromine.
• Disinfection with noble metal ions. The most commonly used is silver.
• Use of strong oxidizing agents. A common example here would be sodium hypochlorite.

Physical methods

This will include non-chemical methods of influencing microorganisms in the liquid. Their use is most often preceded by filtration and This removes suspended particles, worm eggs, and an impressive part of the microbes in the liquid.

The most common ways:

• Exposure to ultraviolet radiation.
• The impact of ultrasound.
• Boiling. An effective way to disinfect water in natural conditions.

Let's take a look at each of them in more detail.

UV irradiation

It is important to calculate the necessary share of the acting energy for a certain volume of water. To do this, multiply the radiation power and the time of contact with the liquid. It is important to first determine the concentration of microorganisms in 1 ml of water, the number of indicator bacteria (in particular, Escherichia coli).

Note that UV rays will adversely affect microorganisms better than chlorine. Ozone, according to the results of purification, will be equal in efficiency to irradiation. UV rays affect both enzyme metabolism and the cell structures of bacteria and viruses. What is important, destroy vegetative, spore forms.

The advantages of the method are:

• There is no upper dose threshold, since such irradiation does not form toxic compounds in water. By increasing it, you can gradually achieve the best results.
• Great for personal use.
• Long service life of the UV lamp - several thousand hours.

But there are also disadvantages:

• No consequences of the event - in order to prevent the return of microorganisms, the water should be disinfected periodically and systematically, without turning off the installation.
• Quartz lamps are sometimes contaminated with deposits of mineral salts. However, this can be easily prevented with the help of ordinary food acid.
• Preliminary purification of water from particles suspended in it is obligatory - by screening the rays, they nullify the whole process.

The method of water disinfection in the field using UV radiation is shown in the picture.

Ultrasound

The action here is based on cavitation. This is the name of the ability of a number of sound frequencies to form voids that create a large difference in pressure. This dissonance leads to a rupture of the cell membranes of viruses, bacteria, which leads to the death of microorganisms. The efficiency depends on the intensity of the vibrations of the sound.

This method is not widely used primarily because of its high cost. Certain equipment and specially trained personnel are required. It is important to remember that ultrasound is dangerous for bacteria only at certain frequencies. Low waves, on the contrary, can cause an acceleration in the growth of the number of microorganisms in water.

Boiling

The simplest and most common way to disinfect water in the field is, of course, boiling. Its popularity and recognition is based on many factors:

• Destruction in the liquid of almost all harmful microorganisms - viruses, bacteria and bacteriophages, antibiotics, etc.
• Availability - you need a heat source capable of heating water to 100 degrees Celsius, and a heat-resistant container.
• Does not affect the taste of the liquid, its color and smell.
• Eliminates gases dissolved in water.
• Perfectly fights with the rigidity of the liquid, softens it.

Complex cleaning methods

From simple ways water disinfection, we will move on to complex ones, which are the most effective in a number of cases. For example, this is a combination of UV irradiation and chlorination, ozonation and chlorination (prevention of secondary infection), reagentless and reagent methods.

Filtering is often included in this category. But with the peculiarity that each filter cell should be smaller in size than the microorganisms to be screened out. This means that its diameter should not exceed 1 micron. But in this way you can only fight bacteria. Against viruses, more microscopic pores are used - with a diameter of less than 0.1-0.2 microns.

In the modern market, a filtration system called "Purifier" is popular. The device differs in that it uses several water filtration systems, its disinfection. Some models can additionally cool water up to 4 degrees and heat up to 95 degrees.

Installation is applicable both in industrial, and in office, house scales. It is enough to simply connect it to the water pipe with a plastic adapter. Manufacturers claim that the purchase, connection and operation of the Purifier will cost the owner less than the delivery of bottled water.

Innovative disinfection methods

The newest methods of water disinfection today will be electrochemical and electropulse. In the domestic market, they are used in such devices as "Emerald", "Sapphire", "Aquamarine".

Their functioning is based on the operation of a special electrochemical diaphragm reactor, through which water is passed. It, in turn, is separated by a metal-ceramic membrane, which is capable of producing ultrafiltration into the cathode and anode zones.

At the moment when current is supplied to the anode and cathode chambers, solutions begin to form in them - alkaline and acidic. Then - electrolytic formation (its other name is active chlorine). This whole environment is distinguished by the fact that the overwhelming number of species of harmful microorganisms actively die in it. It is also capable of destroying some compounds dissolved in the liquid.

The performance of the presented devices mainly depends on two factors: the number of working elements and their design. In some units, catholytes and anolytes are used (mainly in the medical field). Such disinfection is called ECA technology.

By the way, many misconceptions are associated with it. Some device manufacturers claim that the water treated in their unit becomes healing and even miraculous. However, in reality, it is only cleaned and disinfected.

Electric impulse cleaning is the transmission of an electric discharge through the water column. Ultra-high pressure shock wave, light radiation, ozone formation - a consequence of exposure. All this together is detrimental to microorganisms suspended in the liquid.

We got acquainted with different methods of water disinfection - simple and complex, traditional and innovative, effective and safe for humans. Each of them has its own advantages and disadvantages. However, the leading factor is harmlessness to the human body and the environment.