Demineralized water. Demineralized water (Aqua demineralisata)

There is a misconception that water is a neutral liquid solution in its composition. But it is not so. There are salts in water, the presence of which under special conditions makes the water electrically and chemically active. This negatively affects the operation of manufactured products and the functionality of certain types of equipment. An important link in production technical processes is a special stage - water demineralization.

The process by which all minerals are removed from water is called water demineralization. There are four ways to demineralize water: deionization, reverse osmosis, distillation and electrodialysis.

Deionization is a process that uses the ion exchange method. During deionization, water is treated in two layers of ion-exchange material. This is done so that the removal of all salts present in the water is most effective. Simultaneously or sequentially, cation exchange resin and anion exchange resin are used in deionization. All water-soluble salts consist of cations and anions. Next, a mixture of the two indicated resins in demineralized water completely replaces them with hydrogen ions H+ and hydroxyl OH-. As a result of a chemical reaction, these ions combine and a water molecule is created. With this process, virtually complete desalination of water occurs. Deionized water is very widespread in industry, the chemical, pharmaceutical industries, and in industrial leather processing. Previously, such water was used in the production of cathode ray televisions.

Electrodialysis is a method based on the ability to move ions in water under the influence of an electric field. A decrease in salt concentration occurs in a volume limited by ion-exchange membranes.

The distillation method is based on evaporation followed by concentration of steam of the treated water. This method water demineralization is not widely used because it is too energy-intensive; moreover, during the distillation process, scale forms on the walls of the evaporator.

The most common method of water demineralization is. This method water demineralization has long been recognized as highly professional. Initially, the method of water purification using reverse osmosis was proposed for desalination of sea water. However, it later became clear that the method of water demineralization using reverse osmosis, together with filtration and ion exchange, can significantly expand the possibilities of water purification.

Principle water demineralization The reverse osmosis method involves pushing water through a thin-film, semi-permeable membrane. The pores of the membrane are so small that only water and low molecular weight gases, including oxygen and carbon dioxide, can pass through them. As a result of this treatment, all impurities remain on the membrane and are subsequently drained into the drainage.

In terms of cleaning efficiency, membrane systems have no competitors. They are capable of purifying water by 97-99.99% of any type of contaminant. As a result, when using the reverse osmosis method, distilled or highly desalted water is obtained. The reverse osmosis method has its own characteristics. One of the main features is that deep cleaning on the membrane can only be carried out on water that has undergone preliminary comprehensive cleaning from sand, rust and other similar water-insoluble suspensions.

It is especially important that the water prepared for demineralization is cleared of chlorine and organochlorine compounds that can destroy the membrane material.

How do you know if water is completely demineralized? The water parameters after demineralization must correspond to the following indicators: the electrical resistivity value must be in the range of 3-18 MoM*cm at a water temperature of 20°C; pH level should be 6.5-8; silicic acid content - less than 20 µg/l; total hardness - less than 1 mmol/l.

The purpose of this article is to understand the terms: osmotic water, distilled water, deionized water, demineralized water And bidistilled water. All these terms have a common feature - it is deeply purified water with a minimum amount of impurities. Obtaining deionized water(deeply purified water) is necessary in many industries and medicine (production of electrolytes, microelectronics, electroplating, laboratories, injection solutions, pharmaceuticals, etc.).

Osmotic water

Very often osmotic water is compared with distilled. Actually this is not correct. One of the main blocks of a modern distiller is reverse osmosis Reverse osmosis membranes differ from each other in filtration quality and are available in low-pressure (low-selective) and high-pressure (high-selective) types. Water obtained by reverse osmosis is called osmotic water. There are no regulatory documents for this type of water. The quality of filtration is measured, as a rule, with a conductometer (shows the specific electrical conductivity of water). The selectivity of osmotic membranes is 85-99%. Knowing the selectivity of the membrane, it is possible to predict the quality of purified water (reverse osmosis filtrate or permeate). It is important to remember that reverse osmosis membranes have the form of a fine sieve, which retains almost all salt ions and organic impurities, but at the same time allows water molecules and all gases dissolved in the source water to pass through (since the size of a gas molecule is smaller than a water molecule). The production of deionized or osmotic water is often required in the distillery industry, the chemical industry, for denitrification of well water (nitrate removal), for boron removal, etc.

Distilled water and distillers

It is a mistaken opinion that distilled water is the most chemically pure water. Distilled water is water that is almost completely purified from mineral salts, organic and other impurities dissolved in it. The equipment used to obtain such water is called a distiller (aquadistiller). The heart of a modern distiller is a reverse osmosis membrane. As a rule, to obtain distilled water (distillate), osmotic water is subjected to additional purification by one method or another (second cascade of osmotic membranes, ion exchange, electrodeionization, etc.), and special attention is also paid to the elements of preliminary water preparation (adjustment of the pH value, ultrafiltration etc.). To obtain one cubic meter of distilled water using the membrane method, you need 2-4 kW of electrical power, depending on the required performance.

The quality of the distillate is regulated by the technical specifications GOST 6709-72 “Distilled water”. The most important indicator of the quality of distilled water is Electrical conductivity of distilled water.

Note: When searching for distilled water in World Wide Web search engines, grammatical errors are often made " distilled water», « distilled water" or " distilled water»

Demineralized and deionized water

Demineralized water ( deionized water) - water that meets all the requirements for distilled water, except for the content of organic substances oxidized by potassium permanganate KMnO4. Produced by reverse osmosis or ion exchange.

Note: When searching for demineralized or deionized water on World Wide Web search engines, there are often grammatical errors " demineralized water" or " deionized water»

Double-distilled and high-resistivity water

Judging by the above GOST standards, distilled water is not pure from a chemical point of view. Double-distilled water (bidistillate) is close to chemically pure water. A modern double-distiller consists of several filtration stages: ultrafiltration, two-stage osmosis, ion exchange (FSD mixed-action filters), EDI electrodeionization, etc.). Bi-distilled water is often called " high resistance water" It is believed that the purest water has a resistivity of 16-18 MOhm x cm. Obtaining demineralized water of this quality is a task that requires highly qualified designers of the desalting complex. Our company produces installations for producing high-purity water of any capacity using unique resource- and financial-saving technologies.

Natural water always contains various impurities, the nature and concentration of which determines its suitability for certain purposes.

Drinking water supplied by centralized domestic drinking water supply systems and water pipelines, according to GOST 2874-73, can have a total hardness of up to 10.0 mg-eq/l, and a dry residue of up to 1500 mg/l.

Naturally, such water is unsuitable for preparing titrated solutions, for performing various studies in an aqueous environment, for many preparative works involving the use of aqueous solutions, for rinsing laboratory glassware after washing, etc.

Distilled water

The method of demineralization of water by distillation (distillation) is based on the difference in the vapor pressure of water and salts dissolved in it. At not very high temperatures, it can be assumed that the salts are practically non-volatile and demineralized water can be obtained by evaporation of water and subsequent condensation of its vapor. This condensate is commonly called distilled water.

Water purified by distillation in distillation apparatuses is used in chemical laboratories in quantities greater than other substances.

According to GOST 6709-72, distilled water is a transparent, colorless, odorless liquid with pH = 5.44-6.6 and a solids content of no more than 5 mg/l.

According to the State Pharmacopoeia, the dry residue in distilled water should not exceed 1.0 mg/l, and pH = 5.0 4-6.8. In general, the requirements for the purity of distilled water according to the State Pharmacopoeia are higher than according to GOST 6709-72. Thus, the pharmacopoeia allows the content of dissolved ammonia to be no more than 0.00002%, GOST no more than 0.00005%.

Distilled water should not contain reducing substances (organic substances and inorganic reducing agents).

The clearest indicator of water purity is its electrical conductivity. According to literature data, the specific electrical conductivity of ideally pure water at 18°C ​​is 4.4*10 V minus 10 S*m-1,

If the need for distilled water is small, water distillation can be carried out at atmospheric pressure in conventional glass installations.

Once distilled water is usually contaminated with CO2, NH3 and organic matter. If water with very low conductivity is required, the CO2 must be completely removed. To do this, a strong stream of air purified from CO2 is passed through water at 80-90 °C for 20-30 hours and then the water is distilled at a very slow air flow.

For this purpose, it is recommended to use compressed air from a cylinder or suck it in from the outside, since it is very contaminated in a chemical laboratory. Before adding air to the water, it is first passed through a washing bottle with conc. H2SO4, then through two wash bottles with conc. KOH and, finally, through a bottle of distilled water. In this case, the use of long rubber tubes should be avoided.

Most of the CO2 and organic matter can be removed by adding about 3 g of NaOH and 0.5 g of KMnO4 to 1 liter of distilled water and discarding some of the condensate at the beginning of the distillation. The bottom residue should be at least 10-15% of the load. If the condensate is subjected to secondary distillation with the addition of 3 g of KHSO4, 5 ml of 20% H3PO4 and 0.1-0.2 g of KMnO4 per liter, this ensures complete removal of NH3 and organic contaminants.

Long-term storage of distilled water in glass containers always leads to its contamination with glass leaching products. Therefore, distilled water cannot be stored for a long time.

Metal distillers

Electrically heated distillers. In Fig. 59 shows the D-4 distiller (model 737). Capacity 4 ±0.3 l/h, power consumption 3.6 kW, cooling water consumption up to 160 l/h. The weight of the device without water is 13.5 kg.

In the evaporation chamber 1, the water is heated by electric heaters 3 to a boil. The resulting steam through pipe 5 enters the condensation chamber 7, built into chamber 6, through which tap water continuously flows. The distillate flows out of condenser 8 through nipple 13.

At the beginning of operation, tap water continuously flowing through nipple 12 fills the water chamber 6 and through the drain pipe 9 through the equalizer 11 fills the evaporation chamber to the set level.

In the future, as it boils away, the water will only partially enter the evaporation chamber; the main part, passing through the condenser, more precisely through its water chamber 6, will be drained through the drain tube into the equalizer and then through nipple 10 into the sewer. The hot water that flows out can be used for household needs.

The device is equipped with a level sensor 4, which protects electric heaters from burning out if the water level drops below the permissible level.

Excess steam from the evaporation chamber exits through a tube mounted in the wall of the condenser.

The device is installed on a flat horizontal surface and, using a grounding bolt 14, is connected to a common grounding circuit, to which an electrical panel is also connected.

When starting up the device for the first time, you can use distilled water for its intended purpose only after 48 hours of operation of the device.

Periodically, it is necessary to mechanically descale the electric heaters and the level sensor float.

The D-25 distiller (model 784) is designed similarly, with a capacity of 25 ±1.5 l/h and a power consumption of 18 kW.

This device has nine electric heaters - three groups of three heaters. For normal and long-term operation of the device, it is enough for six heaters to be turned on simultaneously. But this requires periodic, depending on the hardness of the feed water, mechanical descaling of the tube through which the water enters the evaporation chamber.

When initially starting up the D-25 distiller, it is recommended to use distilled water for its intended purpose after 8-10 hours of operation of the device.

Of significant interest is the apparatus for producing pyrogen-free water for injection A-10 (Fig. 60). Productivity 10 ±0.5 l/h, power consumption 7.8 kW, cooling water consumption 100-180 l/h.

In this apparatus, reagents are supplied to the evaporation chamber along with the distilled water to soften it (potassium alum Al2(SO4)3-K2SO4-24H2O) and to remove NH3 and organic contaminants (KMnO4 and Na2HPO4).

The alum solution is poured into one glass vessel of the dosing device, and the KMnO4 and Na2HPO4 solutions into another - at the rate of 0.228 g of alum, 0.152 g of KMnO4, 0.228 g of Na2HPO4 per 1 liter of pyrogen-free water.

During the initial start-up or when starting up the device after long-term preservation, the resulting pyrogen-free water can be used for laboratory needs only after 48 hours of operation of the device.

Before operating metal distillers with electric heating, you should check that all wires are connected correctly and that they are grounded. It is strictly forbidden to connect these devices to the electrical network without grounding them. In case of any malfunction, the distillers must be disconnected from the network.

The quality of distilled water depends to a certain extent on the duration of operation of the device. So, when using old distillers, the water may contain chloride ions.

The receivers must be made of neutral glass and, in order to avoid the ingress of CO2, connected to the atmosphere through calcium chloride tubes filled with soda lime granules (a mixture of NaOH and Ca(OH)2).

Fire distiller. The DT-10 distiller with a built-in firebox is designed for operation in conditions where there is no running water or electricity and allows you to obtain up to 10 liters of distilled water in 1 hour. It is a cylindrical structure made of stainless steel with a height of about 1200 mm, mounted on a base 670 mm long and 540 mm wide.

The distiller consists of a built-in firebox with combustion fittings, a 7.5-liter evaporation chamber, a 50-liter cooling chamber and a 40-liter distilled water collector.

Water is poured into the evaporation and cooling chambers manually. As water is consumed in the evaporation chamber, it is automatically replenished from the cooling chamber.

Obtaining bidistillate

Once distilled water in metal distillers always contains small amounts of foreign substances. For particularly precise work, they use re-distilled water - bidistillate. The industry mass-produces water double-distillation devices BD-2 and BD-4 with a capacity of 1.5-2.0 and 4-5 l/h, respectively.

Primary distillation occurs in the first section of the apparatus (Fig. 61). KMnO4 is added to the resulting distillate to destroy organic impurities and it is transferred to a second flask, where secondary distillation occurs, and the bidistillate is collected in a receiving flask. Heating is carried out using electric heaters; Glass water refrigerators are cooled with tap water. All glass parts are made from Pyrex glass.

Determination of quality indicators of distilled water

Determination of pH. This test is carried out by the potentiometric method with a glass electrode or, in the absence of a pH meter, by the colorimetric method.

Using a rack for colorimetry (a rack for test tubes equipped with a screen), place in four numbered identical test tubes with a diameter of about 20 mm and a capacity of 25-30 ml, clean, dry, made of colorless glass: 10 ml of test water each are placed in test tubes No. 1 and 2 , in test tube No. 3 - 10 ml of a buffer mixture corresponding to pH = 5.4, and in test tube No. 4 - 10 ml of a buffer mixture corresponding to pH = 6.6. Then 0.1 ml of a 0.04% aqueous alcohol solution of methyl red is added to test tubes No. 1 and 3 and mixed. Add 0.1 ml of a 0.04% aqueous alcohol solution of bromothymol blue to test tubes No. 2 and 4 and mix. Water is considered to comply with the standard if the contents of test tube No. 1 are not redder than the contents of test tube No. 3 (pH = 5.4), and the contents of test tube No. 2 are not bluer than the contents of test tube No. 4 (pH = 6.6).

Determination of dry residue. In a pre-calcined and weighed platinum cup, 500 ml of the test water is evaporated to dryness in a water bath. Water is added to the cup in portions as it evaporates, and the cup is protected from contamination with a safety cap. Then the cup with the dry residue is kept for 1 hour in a drying oven at 105-110 °C, cooled in a desiccator and weighed on an analytical balance.

Water is considered to comply with GOST 6709-72 if the mass of the dry residue is no more than 2.5 mg.

Determination of ammonia and ammonium salts content. 10 ml of the test water is poured into one test tube with a ground glass stopper with a capacity of about 25 ml, and 10 ml of a standard solution prepared as follows: 200 ml of distilled water is placed in a 250-300 ml conical flask, 3 ml of a 10% solution is added NaOH and boil for 30 minutes, after which the solution is cooled. Add 0.5 ml of a solution containing 0.0005 mg NH4+ to the test tube with the standard solution. Then 1 ml of ammonia reagent (see Appendix 2) is simultaneously added to both test tubes and mixed. Water is considered to comply with the standard if the color of the contents of the test tube observed after 10 minutes is no more intense than the color of the standard solution. Color comparison is made along the axis of the tubes on a white background.

Test for reducing substances. Bring 100 ml of test water to a boil, add 1 ml of 0.01 N. KMnO4 solution and 2 ml of diluted (1:5) H2SO4 and boil for 10 minutes. The pink color of the test water should be preserved.

Demineralization of fresh water by ion exchange method

During the deionization of water, the processes of H+ cationization and OH- anionization are sequentially carried out, i.e., the replacement of cations contained in water with H+ ions and anions with OH- ions. By interacting with each other, H+ and OH- ions form the H2O molecule.

The deionization method produces water with a lower salt content than conventional distillation, but does not remove non-electrolytes (organic contaminants).

The choice between distillation and deionization depends on the hardness of the source water and the costs associated with its purification. Unlike water distillation, during deionization, energy consumption is proportional to the salt content in the water being purified. Therefore, at a high concentration of salts in the source water, it is advisable to first use the distillation method, and then carry out additional purification by deionization.

Ion exchangers are solid, practically insoluble in water and organic solvents, substances of mineral or organic origin, natural and synthetic. For the purposes of water demineralization, synthetic polymer ion exchangers are of practical importance - ion exchange resins, characterized by high absorption capacity, mechanical strength and chemical resistance.

Demineralization of water can be carried out by successively passing tap water through a column of cation exchange resin in the H+ form, then through an anion exchange resin column in the OH- form. The filtrate from the cation exchanger contains acids corresponding to the salts in the source water. The completeness of removal of these acids by anion exchangers depends on their basicity. Strongly basic anion exchangers remove all acids almost completely; weakly basic anion exchangers do not remove such weak acids as carbonic, silicon and boric.

If these acidic groups are acceptable in demineralized water or their salts are absent in the source water, then it is better to use weakly basic anion exchangers, since their subsequent regeneration is easier and cheaper than the regeneration of strongly basic anion exchangers.

For demineralization of water in laboratory conditions, cation exchangers of the brands KU-1, KU-2, KU-2-8chS and anion exchangers of the brands EDE-10P, AN-1, etc. are often used. Ion exchangers supplied in dry form are crushed and grains of size 0. 2-0.4 mm using a set of sieves. They are then washed with distilled water by decantation until the washing waters become completely clear. After this, the ion exchangers are transferred to glass columns of various designs.

In Fig. 62 shows a small-sized column for water demineralization. Glass beads are placed at the bottom of the column and glass wool is placed on top of them. To prevent air bubbles from getting between the ion exchanger grains, the column is filled with a mixture of ion exchanger and water. Water is released as it accumulates, but not below the level of the ion exchanger. The ion exchangers are covered with a layer of glass wool and beads on top and left under a layer of water for 12-24 hours. After draining the water from the cation exchanger, the column is filled with 2 N. HCl solution, leave for 12-24 hours, drain the HCl and wash the cation exchanger with distilled water until the methyl orange reaction is neutral. The cation exchanger, converted to the H+ form, is stored under a layer of water. Similarly, the anion exchanger is transferred to the OH form, keeping it in the column after swelling in 1 N. NaOH solution. The anion exchanger is washed with distilled water until the phenolphthalein reaction is neutral.

Demineralization of relatively large volumes of water with separate use of ion exchange filters can be carried out in a larger installation. The material for two columns with a height of 700 and a diameter of 50 mm can be glass, quartz, or transparent plastic. 550 g of the prepared ion exchanger are placed in the columns: in one - the cation exchanger in the H+ form, in the other - the anion exchanger - in the OH- form. Tap water enters the column with a cation exchange resin at a rate of 400-450 ml/min, and then passes through the column with an anion exchange resin.

Since ion exchangers are gradually saturated, it is necessary to monitor the operation of the installation. In the first portions of the filtrate passed through the cation exchanger, the acidity is determined by titration with an alkali against phenolphthalein. After about 100 liters of water have been passed through the installation, or it has operated continuously for 3.5 hours, you should take a water sample again from the cation exchange column and determine the acidity of the filtrate. If a sharp decrease in acidity is observed, the flow of water should be stopped and the ion exchangers should be regenerated.

The cation exchanger is poured from the column into a large jar with a 5% HCl solution and left overnight. Then the acid is drained, the cation exchanger is transferred to a Buchner funnel and washed with distilled water until the reaction for the Cl- ion with AgNO3 is negative. The washed cation resin is reintroduced into the column.

The anion resin is regenerated with a 5% NaOH solution, washed with water until the phenolphthalein reaction is negative, and then the column is refilled with it.

Currently, water demineralization is mostly carried out using the mixed layer method. The source water is passed through a mixture of a cation exchanger in the H+ form and a strongly or weakly basic anion exchanger in the OH- form. This method ensures the production of water of a high degree of purity, but the subsequent regeneration of ion exchangers requires a lot of labor.

To deionize water using mixed ion exchanger filters, a mixture of KU-2-8chS cation exchanger and EDE-10P anion exchanger in a volume ratio of 1.25:1 is loaded into a column with a diameter of 50 mm and a height of 600-700 mm. Plexiglas is preferred as the material for the column, and polyethylene for the supply and waste tubes.

One kilogram of ion exchanger mixture can purify up to 1000 liters of once distilled water.

Regeneration of spent mixed ion exchangers is carried out separately. The mixture of ion exchangers from the column is transferred to a Buchner funnel and sucked off until an air-dry mass is obtained. Then the ion exchangers are placed in a separating funnel of such capacity that the ion exchanger mixture occupies 1/4 of its volume. After this, add up to 3/4 volume of a 30% NaOH solution to the funnel and mix vigorously. In this case, the mixture of ion exchangers, due to their different densities (cation exchanger 1.1, anion exchanger 1.4), is divided into layers. After this, the cation exchanger and anion exchanger are washed with water and regenerated as indicated above.

In laboratories where the need for deeply demineralized water exceeds 500-600 l/day, the commercially available device Ts 1913 can be used. The estimated capacity is 200 l/h. The throughput capacity of the deionizer during the inter-regeneration period is 4000 liters. The weight of the set is 275 kg.

The demineralizer is equipped with a system for automatically shutting off the supply of tap water when its electrical resistance drops below the permissible value and float valves that allow you to automatically remove air from the columns. Regeneration of ion exchange resins is carried out by treating them directly in columns with a solution of NaOH or HCl.

WORLD HEALTH ORGANIZATION

Nutrients in drinking water

Water, sanitation, health and environment

Geneva

2005

Information from the site: http://waterts.blogspot.com/search/label/Nutrients%20in%20drinking%20water

PREFACE

In November 2003, a group of nutrition and medical experts met in Rome (European Center for Environment and Health) to work on issues related to the composition of drinking water and its possible contribution to overall nutrient intake. The original purpose of this meeting was to contribute to the development of the Guidelines for healthy and environmentally sound desalination introduced by the WHO Eastern Mediterranean Regional Office for the preparation of the 4th edition of the WHO Drinking Water Quality Guidelines (DQQG). A total of 18 experts were invited from Canada, Chile, the Czech Republic, Germany, Ireland, Italy, Moldova, Singapore, Sweden, the United Kingdom and the USA. Additionally, reports were presented from experts who were unable to come in person. The purpose of the meeting was to assess the possible consequences for human health of long-term use of “conditioned” or “modified”, i.e. treated water, with a modified mineral composition, artificially purified, or vice versa, enriched with minerals.

In particular, the question arose about the consequences of long-term consumption of water that has undergone demineralization: sea water and brackish water subjected to desalination, fresh water processed in a membrane system, as well as the reconstruction of their mineral composition.

The following main issues were discussed at the meeting:

What is the contribution of drinking water to the total supply of nutrients to the body?

What is the average daily consumption of drinking water by a person? How does it change depending on climate, lifestyle, age and other factors?

Which substances found in water can significantly affect your health and well-being?

Under what conditions can drinking water become a significant source of some substances important for humans?

What conclusions can be drawn about the relationship between calcium, magnesium and other elements in water and mortality from cardiovascular diseases?

For what substances in treated water can mineral enrichment recommendations be developed in terms of health benefits?

What is the role of fluoride in improving dental health, as well as in the development of dental and bone fluorosis?

As a rule, before serving to the consumer, drinking water undergoes one or more types of treatment to achieve appropriate safety indicators and improve aesthetic properties. Fresh waters are usually subjected to coagulation, sedimentation, granular filtration, adsorption, ion exchange, membrane filtration, slow sand filtration, disinfection, and sometimes softening. Obtaining drinking water from highly saline waters such as sea and brackish waters through desalination is widely practiced in regions experiencing an acute shortage of water. In the context of constantly growing water consumption, such technology is becoming increasingly attractive from an economic point of view. The world produces more than 6 billion gallons of demineralized water every day. Remineralization of such water is mandatory: it is aggressive towards distribution systems. If remineralization of demineralized water is a prerequisite, a logical question arises: are there water treatment techniques that can restore the content of some important minerals?

Natural waters vary significantly in composition due to their geological and geographical origin, as well as the processing to which they have been subjected. For example, rainwater and surface water, replenished mainly by precipitation, have very low salinity and salinity, while groundwater is characterized by very high and even excessive salinity. If remineralization of treated water is needed for hygienic reasons, then another logical question arises: Are natural waters that contain the “right” amounts of important minerals healthier?

During the meeting, the experts reached the following conclusion: only some minerals in natural water are found in quantities sufficient to account for their contribution to the total supply. Magnesium and, possibly, calcium are two elements that enter the human body from water in significant quantities (subject to the consumption of hard water). This conclusion was made on the basis of 80 epidemiological studies examining the relationship between drinking hard water and reducing the incidence of cardiovascular diseases in the population. The research covers a 50-year period. Despite the fact that the studies were mainly ecological in nature and were carried out at different levels, experts recognized that the hypothesis linking hard water consumption with the incidence of cardiovascular disease is correct, and magnesium should be considered the most important beneficial component. This conclusion was confirmed by both control and clinical studies. There are other elements in water that have a positive effect on health, but the available data was not enough to discuss the issue.

The meeting also decided that the WHO should provide a more detailed assessment of the biological plausibility of the hypothesis. Only after this the Guidelines will be finalized. A follow-up symposium and meeting to discuss this recommendation are planned for 2006.

Regarding fluoride, experts have concluded that optimal fluoride intake in drinking water is an important factor in dental health. It was also noted that consumption of fluoride in amounts greater than optimal can lead to dental fluorosis, and even higher concentrations can lead to skeletal fluorosis. Fluoride dosages when enriching demineralized water with fluoride must be calculated based on the following factors: the concentration of fluoride in the source water, the volume of water consumption, risk factors for dental diseases, oral hygiene methods, the level of development of hygiene and sanitation in society, as well as the availability of alternative means of oral hygiene and availability of fluoride for the population.

“Water should be a source of macro- and microelements necessary for the human body...”

N.K.Koltsov, outstanding Russian chemist-biologist

N.K. Koltsov proposed using the concept of physiological usefulness for drinking water back in 1912, combining with this term a set of anions and cations necessary for the human body and contained in natural water. Later studies confirmed the importance of the mineral composition of drinking water and are reflected in many scientific works. In particular, the report by František Kozišek (National Institute of Public Health, Czech Republic) “Health consequences arising from the consumption of demineralized drinking water”, presented at the WHO expert meeting in 2003 states:

Artificially processed demineralized water, which was initially obtained by distillation and then by reverse osmosis, should be used for industrial, technical and laboratory purposes.

Epidemiological studies conducted in different countries over the past 50 years have shown that there is an association between the increased incidence of cardiovascular disease and subsequent death and the consumption of soft water. When comparing soft water with hard water and rich in magnesium, the pattern can be seen very clearly.

Recent studies have shown that consumption of soft water, such as those low in calcium, may lead to an increased risk of childhood fractures (16), neurodegenerative changes (17), premature birth and low birth weight in newborns (18), and some types of cancer (19,20). ). In addition to an increased risk of sudden death (21–23), drinking water low in magnesium has been associated with heart failure (24), late toxicosis of pregnancy (preeclampsia) (25), and certain types of cancer (26–29) ).

Even in developed countries, food cannot compensate for the deficiency of calcium and, especially, magnesium, if drinking water is poor in these elements.

Modern food preparation technologies do not allow most people to obtain sufficient amounts of minerals and trace elements. In case of acute deficiency of any element, even a relatively small amount of it in water can play a significant protective role. Substances in water are dissolved and are in the form of ions, which allows them to be adsorbed much more easily in the human body than from food products, where they are bound into various compounds.

Drinking water obtained through demineralization is enriched with minerals, but this does not apply to water treated at home.

Perhaps none of the methods of artificially enriching water with minerals is optimal, since saturation with all important minerals does not occur.

GRATITUDE

WHO thanks:

Hussein Abusaid, WHO Eastern Mediterranean Regional Office Coordinator - for the idea and work on creating the Guidelines for desalinated water

Roger Aertgirts, European Regional Advisor on Water and Sanitation and Helena Shkarubo, WHO Rome Center - for processing the meeting materials

Joseph Contruvo, USA and John Faewell, UK – for organizing the meeting

Professor Chun Nam Ong, Singapore - for facilitating the meeting; Gunter Crown, USA - for his contribution to the publication of documents and review of comments

WHO expresses special thanks to the experts, without whom the writing of this work would hardly have been possible: Rebecca Calderon, Gerald Comes, Jean Ekstrand, Floyd Frost, Anne Grandjian, Suzanne Harris, Frantisek Kolizek, Michael Lennon, Silvano Monarca, Manuel Olivares, Dennis O" Mullan, Soule Semalulu, Ion Salaru and Erica Sievers.

WHO also represents the sponsors who made the meeting possible. Among them: the International Institute of Life Sciences, the Division of Science and Technology of the US Environmental Protection Agency (Washington), the Division of Research and Development (Research Triangle Park, North Carolina), the American Joint Research Working Fund for Water, the Center for Human Nutrition in University of Nebraska (Omaha), and Canadian Bureau of Water Quality and Health (Ottawa, Ontario).

12. Health effects arising from the consumption of demineralized drinking water

František Kozišek

National Institute of Public Health

Chech republic

I. Introduction

The mineral composition of waters can vary widely depending on the geological conditions of the area. Neither groundwater nor surface water can be represented as a pure substance, the composition of which is expressed by the formula H2O. In addition, natural waters contain small amounts of dissolved gases, minerals and organic substances of natural origin. Total concentrations of substances dissolved in high-quality water can reach hundreds of mg/l. Thanks to continuous developments in microbiology and chemistry since the 19th century, many waterborne pathogens can be identified. Knowing that water may contain undesirable components is the starting point for creating guidelines and standards for drinking water quality. International standards regulating maximum permissible concentrations of organic and inorganic substances, as well as microorganisms, exist in many countries around the world. These standards guarantee the safety of drinking water. The possible consequences of drinking completely demineralized water are not considered, due to the fact that such water does not actually occur in nature, except, perhaps, rainwater and natural ice. However, rainwater and ice are not used in the water supply systems of developed countries, which have certain drinking water quality standards. As a rule, the use of such water is a special case. Many natural waters are not rich in minerals, have low hardness (lack of divalent ions), and hard waters are often softened artificially.

Knowledge about the importance of minerals and other components in drinking water dates back thousands of years and is already mentioned in the ancient Indian Vedas. The Rig Veda describes the properties of good drinking water as follows: Shiitham (cool), Sushihi (clean), Sivam (must be biologically valuable, contain minerals as well as trace amounts of many elements), Istham (clear), Vimalam lahu Shadgunam (indicator The pH should be within normal limits)” (1).

Artificially processed demineralized water, which was initially obtained by distillation and then by reverse osmosis, should be used for industrial, technical and laboratory purposes. Water treatment technologies began to be widely used in the 1960s in coastal and inland areas. This is due to the scarcity of natural water reserves and increasing water consumption caused by demographic growth, higher standards of quality of life, industrial development and mass tourism. Water demineralization is needed when the available water resources are highly mineralized brackish or sea water. The problem of drinking water on ocean liners and spaceships has always been relevant. The listed treatment methods were previously used to provide water exclusively to these facilities due to technical complexity and high cost.

In this chapter, demineralized water means water completely or almost completely freed from dissolved minerals by distillation, deionization, membrane filtration (reverse osmosis or nanofiltration), electrodialysis, etc. The composition of dissolved substances in such water may vary, but their total content should not be more than 1 mg/l. Electrical conductivity is less than 2 mS/m3 *and even less (<0,1 мС/м3). Начало применения таких технологий – 1960-е годы, в то время деминерализация не была широко распространена. Тем не менее, уже в то время в некоторых странах изучались гигиенические аспекты использования такой воды. В основном это касается бывшего Советского Союза, где планировалась применять обессоливание для обеспечения питьевой водой городов Средней Азии. Изначально было понятно, что обработанная вода не годна для употребления без дополнительного обогащения минеральными веществами:

Demineralized water is very aggressive and must be neutralized; otherwise, it cannot be supplied to the distribution system or passed through pipes and storage tanks. Aggressive water destroys pipes and washes metals and other materials out of them;

Distilled water has “poor” taste characteristics;

It has been proven that some substances present in drinking water are important for the human body. For example, the experience of artificially enriching water with fluoride showed that the incidence of oral diseases decreased, and epidemiological studies conducted in the 1960s showed that residents of regions with hard drinking water suffer less from cardiovascular diseases.

As a result, the researchers focused on two questions: 1) what adverse effects on human health may arise from drinking demineralized water and 2) what should be the minimum, as well as optimal, content of elements important for humans (for example, minerals) in drinking water in order to so that the water quality meets both technological and sanitary standards. The traditionally accepted methodology for assessing water quality, based on an analysis of the risks arising from high concentrations of toxic substances, has now been revised: the possible adverse consequences of a deficiency of certain components in water are also taken into account.

At one of the working meetings on the preparation of guidelines on the quality of drinking water, the World Health Organization (WHO) considered the question of what should be the optimal mineral composition of demineralized drinking water. Experts have focused on the possible adverse effects of drinking water that has been removed from certain substances that are always present in natural drinking water (2). In the late 1970s, WHO sponsored research that could provide fundamental information for the production of guidelines on demineralized water quality. This study was conducted by a group of scientists from the A.N. Institute of Public Health. Sysin and the USSR Academy of Medical Sciences under the leadership of prof. Sidorenko and Dr. med. Sciences Rakhmanin. In 1980, the final report was published as an internal working document (3). It contained the following conclusion: “Demineralized (distilled) water not only has unsatisfactory organoleptic characteristics, but also has an adverse effect on the human body and animals.” After assessing the hygienic, organoleptic properties and other information, scientists made recommendations on the composition of demineralized water:

1 min. mineralization 100 mg/l; content of bicarbonate ions 30 mg/l; calcium 30 mg/l; 2) optimal dry residue (250-500 mg/l for chloride-sulfate waters and 250-500 ml for hydrocarbonate waters); 3) maximum level of alkalinity (6.5 meq/l), sodium (200 mg/l), boron (0.5 mg/l) and bromide ion (0.01 mg/l). Some of the recommended values ​​are discussed in more detail in this chapter.

* - mS/m3 – millisiemens per cubic meter, unit of electrical conductivity

Over the past three decades, demineralization has become widespread as a method of providing drinking water. There are over 11 thousand enterprises in the world that produce demineralized water; total output of finished products - 6 billion gallons of demineralized water per day (Contruvo). In some regions, such as Middle Eastern and Western Asia, more than half of all drinking water is produced this way. As a rule, demineralized water is subjected to further processing: various salts are added to it, for example, calcium carbonate or limestone; mixed with small volumes of highly mineralized water to improve taste characteristics and reduce aggressiveness towards distribution networks and plumbing equipment. However, demineralized waters can vary greatly in their composition, for example in the minimum content of mineral salts.

Many explored water resources do not comply in composition with the unified guidelines for drinking water quality.

The potential for adverse health effects of demineralized water has attracted interest not only in countries where there is a shortage of drinking water, but also in those where home water treatment systems are popular and bottled water is consumed. Some natural drinking waters, in particular glacial ones, are not rich in minerals (less than 50 mg/l), and in a number of countries distilled drinking water is used for drinking purposes. Some brands of bottled drinking water are demineralized water, subsequently enriched with minerals to give it a favorable taste. People who drink such water may not receive enough minerals found in more highly mineralized water. Therefore, when calculating the level of mineral consumption and risks, it is necessary to analyze the situation not only at the level of society, but also at the level of the family, each person individually.

II. Health risks from drinking demineralized or low-mineralized water

Information about the effect of demineralized water on the body is based on experimental data and observations. Experiments were carried out on laboratory animals and human volunteers, observations were made on large groups of people consuming demineralized water, as well as individuals ordering water treated by reverse osmosis and children for whom baby food was prepared with distilled water. Because information from the period of these studies is limited, we must also consider the results of epidemiological studies that compared the health effects of exposure to bland (softer) and highly saline water. Demineralized water that has not been subsequently enriched with minerals is an extreme case. It contains dissolved substances such as calcium and magnesium, the main contributors to hardness, in very small quantities.

Possible consequences of consuming mineral-poor water fall into the following categories:

Direct effects on the intestinal mucosa, metabolism and homeostasis of minerals, and other body functions;

Low intake/absence of calcium and magnesium intake;

Low intake of other macro- and microelements;

Loss of calcium, magnesium and other macroelements during cooking;

Possible increase in the intake of toxic metals into the body.

1. Direct effects on the intestinal mucosa, metabolism and homeostasis of minerals, and other body functions

Distilled and low-mineralized water (total mineralization< 50 мг/л) может быть неприятной на вкус, однако с течением времени потребитель к этому привыкает. Такая вода плохо утоляет жажду (3). Конечно, эти факты еще не говорят о каком-либо влиянии на здоровье, однако их нужно учитывать, принимая решение о пригодности использования слабоминерализованной воды для нужд питьевого водоснабжения. Низкая способность утолять жажду и неприятный вкус могут повлиять на объемы употребления воды или заставить людей искать новые источники воды, зачастую не лучшего качества.

Williams (4) showed in his report that distilled water can cause pathological changes in epithelial cells in the intestines of rats, possibly due to osmotic shock. However, Schumann (5), who later conducted a 14-day experiment with rats, did not obtain such results. Histological examination did not reveal any signs of erosion, ulceration or inflammation of the esophagus, stomach and small intestine. Changes in the secretory function of animals (increased secretion and acidity of gastric juice) and changes in muscle tone of the stomach were observed; these data are presented in the WHO report (3), but the available data do not allow us to clearly prove the direct negative effect of water with low mineralization on the mucous membrane of the gastrointestinal tract.

To date, it has been proven that the consumption of water poor in minerals has a negative impact on the mechanisms of homeostasis, the metabolism of minerals and water in the body: fluid secretion (diuresis) increases. This is due to the leaching of intra- and extracellular ions from biological fluids, their negative balance. In addition, the total water content in the body and the functional activity of some hormones that are closely related to the regulation of water metabolism change. Experiments on animals (mainly rats), which lasted about a year, helped establish that drinking distilled water, or water with a total mineralization of up to 75 mg/l, leads to:

1) an increase in water consumption, diuresis, extracellular fluid volume, concentration of sodium and chloride ion in the serum and their increased excretion from the body; ultimately leading to an overall negative balance, 2) the number of red blood cells and the hematocrit index decrease; 3) a group of scientists led by Rakhmanin, studying the possible mutagenic and gonadotoxic effects of distilled water, found that distilled water does not have such an effect.

However, there was a decrease in the synthesis of the hormones triiodotyranine and aldosterone, increased secretion of cortisol, morphological changes in the kidneys, including pronounced atrophy of the glomeruli and swelling of the layer of cells lining the vessels from the inside, preventing blood flow. Insufficient skeletal ossification was found in rat fetuses whose parents drank distilled water (1-year experiment). It is obvious that the lack of mineral substances was not compensated for in the body of rats even through nutrition, when the animals received their standard diet with the necessary energy value, nutrients and salt composition.

The results of an experiment conducted by WHO scientists on human volunteers showed a similar picture (3), which made it possible to outline the main mechanism of the effect of water with mineralization up to 100 mg/l on the exchange of water and minerals:

1) increased diuresis (20% compared to normal), fluid level in the body, serum sodium concentration; 2) decreased serum potassium concentration; 3) increased excretion of sodium, potassium, chloride, calcium and magnesium ions from the body.

Presumably, water with low mineralization affects the osmotic receptors of the gastrointestinal tract, causing increased release of sodium ions into the intestine and a slight decrease in osmotic pressure in the portal vein system, followed by active release of sodium ions into the blood as a response. Such osmotic changes in the blood plasma lead to a redistribution of fluid in the body. The total volume of extracellular fluid increases, water moves from red blood cells and tissue fluid into plasma, as well as its distribution between intracellular and tissue fluids. Due to changes in plasma volume in the bloodstream, receptors sensitive to volume and pressure are activated. They interfere with the release of aldosterone and, as a result, the release of sodium increases. The response of volume receptors in blood vessels can lead to decreased release of antidiuretic hormone and increased diuresis. The German Nutrition Society came to similar conclusions and recommended avoiding drinking distilled water (7). The message was published in a response to the German publication “The Shocking Truth about Water” (8), the authors of which recommended drinking distilled water instead of regular drinking water. The Society in its report (7) explains that human body fluids always contain electrolytes (potassium and sodium), the concentration of which is under the control of the body itself. Absorption of water by the intestinal epithelium occurs with the participation of sodium ions. If a person drinks distilled water, the intestines are forced to “add” sodium ions to this water, removing them from the body. Liquid is never released from the body in the form of pure water; at the same time, a person also loses electrolytes, which is why it is necessary to replenish their supply from food and water.

Improper fluid distribution in the body can even affect the functions of vital organs. The first signals are fatigue, weakness and headache; more serious - muscle cramps and heart rhythm disturbances.

Additional information was collected through experiments with animals and clinical observations in some countries. Animals that were fed water fortified with zinc and magnesium had much higher concentrations of these elements in their blood serum than those that ate fortified feed and drank low-mineralized water. An interesting fact is that during enrichment, significantly more zinc and magnesium were added to the feed than to the water. Based on the results of experiments and clinical observations of patients with mineral deficiency, patients receiving intravenous nutrition with distilled water, Robbins and Sly (9) suggested that the consumption of low-mineralized water was the cause of increased removal of minerals from the body.

Constant consumption of low-mineralized water can cause the changes described above, but symptoms may not appear, or may take many years to appear. However, serious damage, for example, the so-called. water intoxication, or delirium, may result from intense physical activity and drinking some distilled water (10). So-called water intoxication (hyponatremic shock) can occur not only as a result of consumption of distilled water, but also drinking water in general. The risk of such “intoxication” increases with a decrease in water mineralization. Serious health problems arose among climbers who ate food cooked on melted ice. Such water does not contain anions and cations necessary for humans. Children who consumed drinks made with distilled or bland water experienced conditions such as cerebral edema, convulsions, and acidosis (11).

2. Low/no intake of calcium and magnesium

Calcium and magnesium are very important for humans. Calcium is an important component of bones and teeth. It is a regulator of neuromuscular excitability, participates in the functioning of the conduction system of the heart, contraction of the heart and muscles, and the transmission of information within the cell. Calcium is an element responsible for blood clotting. Magnesium is a cofactor and activator of more than 300 enzymatic reactions, including glycolysis, ATP synthesis, transport of minerals such as sodium, potassium and calcium across membranes, protein and nucleic acid synthesis, neuromuscular excitability and muscle contraction.

If we evaluate the percentage contribution of drinking water to the total intake of calcium and magnesium, it becomes clear that water is not their main source. However, the importance of this source of minerals cannot be overestimated. Even in developed countries, food cannot compensate for the deficiency of calcium and, especially, magnesium, if drinking water is poor in these elements.

Epidemiological studies conducted in different countries over the past 50 years have shown that there is an association between the increased incidence of cardiovascular disease and subsequent death and the consumption of soft water. When comparing soft water with hard water and rich in magnesium, the pattern can be seen very clearly. The review of research is accompanied by recently published articles (12–15), and the results are summarized in other chapters of this monograph (Calderon and Crown, Monarca). Recent studies have shown that consumption of soft water, such as those low in calcium, may lead to an increased risk of childhood fractures (16), neurodegenerative changes (17), premature birth and low birth weight in newborns (18), and some types of cancer (19,20). ). In addition to an increased risk of sudden death (21–23), drinking water low in magnesium has been associated with heart failure (24), late toxicosis of pregnancy (preeclampsia) (25), and certain types of cancer (26–29). ).

Specific information about changes in calcium metabolism in people forced to drink desalted water (for example, distilled, filtered through limestone) with low calcium content and mineralization was obtained in a Soviet city

Shevchenko (3, 30, 31). Decreased alkaline phosphatase activity and plasma calcium and phosphorus concentrations and severe decalcification of bone tissue were observed in the local population. The changes were most pronounced in women (especially pregnant women) and depended on the length of residence in the city of Shevchenko. The importance of a sufficient calcium content in water was established in the above-described experiment with rats receiving a nutritious diet, saturated with nutrients and salts, and desalted water, artificially enriched with minerals (400 mg/l) and calcium (5 mg/l, 25 mg/l, 50 mg/l) (3, 32). Animals that drank water containing 5 mg/l of calcium showed a decrease in thyroid function and a number of other body functions compared to animals in which the dose of calcium was doubled.

Sometimes the consequences of insufficient intake of certain substances into the body are visible only after many years, but the cardiovascular system, experiencing a lack of calcium and magnesium, reacts much faster. Several months of drinking water low in calcium and/or magnesium is sufficient (33). An illustrative example is the population of the Czech Republic and Slovakia in 2000-2002, when the reverse osmosis method began to be used in the centralized water supply system.

Over the course of several weeks or months, there have been many claims related to severe magnesium (and possibly calcium) deficiency (34).

Complaints from the population related to cardiovascular diseases, fatigue, weakness, muscle cramps and actually coincided with the symptoms listed in the report of the German Nutrition Society (7).

3. Low intake of other macro- and microelements

Although drinking water, with rare exceptions, is not a significant source of essential elements, its contribution is for some reasons very important. Modern food preparation technologies do not allow most people to obtain sufficient amounts of minerals and trace elements. In case of acute deficiency of any element, even a relatively small amount of it in water can play a significant protective role. Substances in water are dissolved and are in the form of ions, which allows them to be adsorbed much more easily in the human body than from food products, where they are bound into various compounds.

Experiments on animals have also shown the importance of the presence of trace amounts of certain substances in water. For example, Kondratyuk (35) reported that differences in the supply of microelements led to a sixfold difference in their concentrations in the muscle tissue of animals. The experiment was carried out over 6 months; The rats were divided into 4 groups and drank different water: a) tap water; b) weakly mineralized; c) low-mineralized, enriched with iodine, cobalt, copper, manganese, molybdenum, zinc and fluorine in normal concentrations; d) low-mineralized, enriched with the same elements, but in 10-fold larger quantities. In addition, it was found that unenriched demineralized water negatively affects hematopoietic processes. In animals that received water that was not enriched with microelements and had low mineralization, the number of red blood cells was 19% lower than in animals that received regular tap water. The difference in hemoglobin content was even greater when compared with animals receiving enriched water.

Recent studies of the environmental situation in Russia have shown that the population consuming water with low mineral content is at risk of many diseases. These are hypertension (high blood pressure) and changes in the coronary vessels, gastric and duodenal ulcers, chronic gastritis, goiter, complications in pregnant women, newborns and infants, such as jaundice, anemia, fractures and growth problems (36). However, it is not entirely clear whether all these diseases are associated precisely with a lack of calcium, magnesium and other important elements or with other factors.

Lyutai (37) conducted numerous studies in the Ust-Ilimsk region of Russia.

The subjects of the study were 7658 adults, 562 children and 1582 pregnant women and their newborns; morbidity and physical development were studied. All these people are divided into 2 groups: they live in 2 areas where the water has different mineralization. In the first of the selected areas, the water is characterized by a lower mineralization of 134 mg/l, the calcium and magnesium content is 18.7 and 4.9, respectively, and the bicarbonate ion is 86.4 mg/l. In the second region there is more highly mineralized water of 385 mg/l, the calcium and magnesium content is 29.5 and 8.3, respectively, and bicarbonate ion is 243.7 mg/l. The contents of sulfates, chlorides, sodium, potassium, copper, zinc, manganese and molybdenum were also determined in water samples from two areas. The food culture, air quality, social conditions and time of residence in this region were the same for residents of the two areas. Residents of areas with lower water mineralization more often suffered from goiter, hypertension, coronary heart disease, gastric and duodenal ulcers, chronic gastritis, cholecystitis and nephritis. Children developed more slowly and suffered from some growth abnormalities, pregnant women suffered from edema and anemia, and newborns were more likely to get sick.

A lower incidence rate was noted where the calcium content in the water was 30-90 mg/l, magnesium - 17-35 mg/l, and total mineralization - about 400 mg/l (for water containing bicarbonates). The author came to the conclusion that such water is close to the physiological norm for humans.

4. Loss of calcium, magnesium and other macroelements during cooking

It has become known that in the process of cooking in soft water, important elements are lost from foods (vegetables, meat, grains). Losses of calcium and magnesium can reach 60%, other microelements - even more (copper-66%, manganese-70%, cobalt-86%). In contrast, when cooking with hard water, mineral loss is noticeably lower, and the calcium content of the finished dish may even increase (38-41).

Although most nutrients come from food, cooking with low-mineralized water can significantly reduce the total intake of some elements. Moreover, this shortage is much more serious than when such water is used only for drinking purposes. The modern diet of most people is not able to satisfy the body's needs for all necessary substances and, therefore, any factor that contributes to the loss of minerals during cooking can play a negative role.

5. Possible increase in the intake of toxic metals into the body

The increased risk of toxic metals may be due to two reasons: 1) increased release of metals from materials in contact with water, leading to increased concentrations of metals in drinking water; 2) low protective (antitoxic) properties of water poor in calcium and magnesium.

Water with low mineralization is unstable and, as a result, exhibits high aggressiveness towards materials with which it comes into contact. This water more easily dissolves metals and some organic components of pipes, storage tanks and containers, hoses and fittings, without being able to form complex compounds with toxic metals, thereby reducing their negative impact.

In 1993-1994 In the United States, 8 outbreaks of chemical poisoning in drinking water were reported, including 3 cases of lead poisoning of infants. A blood test of these children showed

lead content is 15 µg/100 ml, 37 µg/100 ml and 42 µg/100 ml, while 10 µg/100 ml is already an unsafe level. In all three cases, lead entered the water from copper pipes and lead-soldered seams in storage tanks. All three water supplies used low-salinity water, which resulted in increased release of toxic materials (42). The first tap water samples obtained showed lead levels of 495 and 1050 μg/L lead; accordingly, children who drank this water had the highest levels of lead in their blood. In the family of the child who received the lower dose, the lead concentration in tap water was 66 μg/L (43).

Calcium and, to a lesser extent, magnesium in water and food are protective factors that neutralize the effects of toxic elements. They can prevent the absorption of some toxic elements (lead, cadmium) from the intestine into the blood, both through a direct reaction of binding toxins into insoluble complexes and through competition during absorption (44-50). Although this effect is limited, it should always be taken into account. Populations that drink water poor in minerals are always at greater risk of exposure to toxic substances than those that drink water of average hardness and mineralization.

6. Possible bacterial contamination of water with low mineralization

In general, water is prone to bacterial contamination in the absence of trace amounts of disinfectant, either at the source or due to microbial regrowth in the distribution system after treatment. Regrowth may also begin in demineralized water.

Bacterial growth in the distribution system may be facilitated by initially high water temperatures, increased temperatures due to hot climates, lack of disinfectant, and possibly greater availability of certain nutrients (water, which is aggressive in nature, easily corrodes the materials from which pipes are made).

Although an intact water treatment membrane should ideally remove all bacteria, it may not be completely effective (due to leaks). Evidence is an outbreak of typhoid fever in Saudi Arabia in 1992 caused by water treated with a reverse osmosis system (51). Nowadays, virtually all water undergoes disinfection before reaching the consumer. The regrowth of nonpathogenic microorganisms in water treated with various home treatment systems has been described in the work of the groups of Geldreich (52), Payment (53, 54) and many others. The Czech National Institute of Public Health in Prague (34) tested a number of products intended to come into contact with drinking water and found that pressurized reverse osmosis tanks are prone to bacterial regrowth: the inside of the tank contains a rubber bulb, which is a bacteria-friendly environment.

III. Optimal mineral composition of demineralized drinking water

The corrosive properties and potential health hazards of demineralized water, the spread and consumption of water with low mineralization have led to the creation of recommendations for minimum and optimal concentrations of minerals in drinking water. Additionally, some countries have developed mandatory standards included in the relevant legislative or technical documentation on drinking water quality. The organoleptic properties and ability of water to quench thirst were also taken into account in the recommendations. For example, studies in which volunteers took part have shown that water temperatures from 15 to 35 °C can be considered optimal. Water with a temperature below 15 °C or above 35 °C was consumed by the subjects in smaller volumes. Water with a dissolved salt content of 25-50 mg/l was considered tasteless (3).

1. WHO Report 1980

Drinking drinking water with low mineralization helps flush salts from the body. Changes in the water-salt balance in the body were noted not only when drinking demineralized water, but also water with mineralization from 50 to 75 mg/l. Therefore, the WHO research group, which prepared a report for 1980 (3), recommends drinking water with a salinity of at least 100 mg/l. Scientists also concluded that the optimal mineralization is 200-400 mg/l for chloride-sulfate waters and 250-500 mg/l for hydrocarbonate waters (1980, WHO). The recommendations are based on experimental data involving rats, dogs and human volunteers. Samples were taken: from the Moscow water supply network, demineralized water with a mineralization of about 10 mg/l and samples prepared in the laboratory (mineralization 50, 100, 250, 300, 500, 750, 1000 and 1500 mg/l) using the following ions: Cl- (40%), HCO3 - (32%), SO4 2- (28%), Na+ (50%), Ca2+ (38%), Mg2+ (12%).

Many indicators were studied: dynamics of body weight, basal metabolism and nitrogen metabolism, enzyme activity, salt metabolism and its regulatory function, mineral content in tissues and body fluids, hematocrit number and antidiuretic hormone activity. With an optimal content of mineral salts, no negative changes were noted in rats, dogs, or people; such water has high organoleptic properties, removes thirst well, and its corrosive activity is low.

In addition to conclusions about the optimal mineralization of water, the report (3) is supplemented with recommendations for calcium content (at least 30 mg/l). There is an explanation for this: at lower calcium concentrations, the exchange of calcium and phosphorus in the body changes and a reduced content of minerals in bone tissue is observed. Also, when the calcium concentration in water reaches 30 mg/l, its corrosiveness decreases and the water becomes more stable (3). The report (3) also recommends a concentration of 30 mg/l of bicarbonate ion to achieve acceptable organoleptic characteristics, reduce corrosivity and achieve equilibrium with calcium ion.

Modern research has provided additional information about the minimum and optimal levels of minerals that should be present in demineralized water. For example, the effect of water with different hardness on the health of women aged 20 to 49 years was the subject of 2 series of epidemiological studies (460 and 511 women) in 4 cities of Southern Siberia (55,56). Water in city A contains the lowest amounts of calcium and magnesium (3.0 mg/l calcium and 2.4 mg/l magnesium). The water in city B is slightly more saturated with salts (18.0 mg/l calcium and 5.0 mg/l magnesium). The highest water saturation with salts was observed in cities B (22.0 mg/l calcium and 11.3 mg/l magnesium) and D (45.0 mg/l calcium and 26.2 mg/l magnesium). Residents of cities A and B, compared to women from C and D, more often observed changes in the cardiovascular system (according to ECG results), high blood pressure, somatic dysfunctions, headache and dizziness, osteoporosis (X-ray absorptiometry).

These results confirm the assumption that the magnesium content in drinking water should be at least 10 mg/l, calcium - 20 mg/l, and not 30 mg/l, as indicated in the WHO report for 1980.

Based on the available data, the researchers recommended the following concentrations of calcium, magnesium, and hardness levels for drinking water:

For magnesium: minimum 10 mg/l (33.56), optimal content 20-30 mg/l (49, 57);

For calcium: minimum 20 mg/l (56), optimal content is about 50 (40-80) mg/l (57, 58);

The total hardness of the water, the total content of calcium and magnesium salts is 2-4 mmol/l (37, 50, 59, 60).

When the composition of drinking water complied with these recommendations, no or almost no negative changes in health were observed. The maximum protective effect or positive effect was observed in drinking water with presumably optimal concentrations of minerals. Observations of the state of the cardiovascular system made it possible to determine optimal levels of magnesium in drinking water, changes in calcium metabolism and ossification processes became the basis for calcium content recommendations.

The upper limit of the optimal hardness range was determined based on the fact that when drinking water with a hardness of more than 5 mmol/l, there is a risk of the formation of stones in the gall bladder, kidneys, bladder, as well as arthrosis and arthropathy in the population.

In the work to determine optimal concentrations, forecasts were based on long-term water consumption. For short-term water use, higher concentrations should be considered to develop therapeutic recommendations.

IV. Guidelines and directives on calcium, magnesium and hardness in drinking water

In the second edition of the Guidelines for Drinking Water Quality (61), WHO evaluates calcium and magnesium in terms of water hardness, but does not make separate recommendations for the minimum or maximum content of calcium, magnesium, or hardness values. The first European Directive (62) established minimum hardness requirements for softened and demineralized water (at least 60 mg/l calcium or equivalent cation). This requirement became mandatory under the national legislation of all EU member states, but this directive expired in December 2003 and was replaced by a new one (63). The new Directive does not include requirements for calcium, magnesium and hardness levels.

On the other hand, nothing prevents the introduction of such requirements into the national legislation of member countries. Only some countries that have joined the EU (for example, the Netherlands) have established requirements for the content of calcium, magnesium and water hardness at the level of mandatory state standards.

Some EU members (Austria, Germany) included these indicators in technical documentation as optional standards (techniques for reducing the corrosiveness of water). All four European countries that joined the EU in May 2004 included these requirements in the relevant regulatory documents, but the severity these requirements are different:

Czech Republic (2004): for softened water: not less than 30 mg/l calcium and not less than 1 mg/l magnesium; Manual requirements: 40-80 mg/l calcium and 20-30 mg/l magnesium (hardness as

Σ Ca + Mg = 2.0-3.5 mmol/l);

Hungary (2001): hardness 50-350 mg/l (according to CaO); the minimum required concentration for bottled water, new sources of water, softened and demineralized water is 50 mg/l;

Poland (2000): hardness 60-500 (according to CaCO3);

Slovakia (2002): calcium requirements are the same as those specified in the Guidelines

> 30 mg/l, for magnesium 10-30 mg/l.

The Russian standard for habitats in manned spacecraft - general medical and technical requirements (64) - defines the requirements for the ratio of minerals in reprocessed drinking water. Among other requirements, mineralization is indicated in the range from 100 to 1000 mg/l; The minimum levels of fluorine, calcium and magnesium are established by a special commission of each spacefleet separately. Emphasis is placed on the problem of enriching recycled water with mineral concentrates to impart physiological value to it (65).

V. Conclusions

Drinking water should contain at least minimal amounts of essential minerals (and some other components, such as carbonates). Unfortunately, over the past two decades, researchers have paid little attention to the beneficial effects of water and its protective properties, as they were preoccupied with the problem of toxic pollutants. However, attempts have been made to define minimum essential mineral content or salinity of drinking water, and some countries have incorporated component-specific Guidelines into their legislation.

This issue is relevant not only for demineralized drinking water, which has not been enriched with a complex of mineral substances, but also for water in which the content of mineral substances is reduced due to home or centralized processing, as well as for low-mineralized bottled water.

Drinking water obtained through demineralization is enriched with minerals, but this does not apply to water treated at home. Even after stabilization of the mineral composition, water may not have beneficial effects on health. Typically, water is enriched with minerals by passing through limestone or other carbonate-containing minerals. In this case, the water is saturated mainly with calcium, and the deficiency of magnesium and other microelements, for example, fluorine and potassium, is not compensated for by anything. In addition, the amount of calcium added is regulated more by technical (reducing water aggressiveness) than by hygienic considerations. Perhaps none of the methods of artificially enriching water with minerals is optimal, since saturation with all important minerals does not occur. As a rule, methods for stabilizing the mineral composition of water are developed in order to reduce the corrosive activity of demineralized water.

Unfortified demineralized water or water with low mineral content - in light of the lack or absence of important minerals in it - is far from an ideal product, and therefore its regular consumption does not adequately contribute to the total intake of some important nutrients. This chapter substantiates this claim. Confirmation of experimental data and discoveries obtained on human volunteers during the study of highly demineralized water can be found in earlier documents, which do not always meet modern methodological requirements. However, we should not neglect the data from these studies: some of them are unique. Early studies, both animal experiments and clinical observations of the health effects of demineralized water, yielded comparable results. This is confirmed by modern research.

Enough data has been collected to confirm that a deficiency of calcium and magnesium in water does not go away without consequences. There is evidence that higher levels of magnesium in water lead to a reduced risk of cardiovascular disease and sudden death. This relationship has been described in many studies independently. However, the studies were structured in different ways and concerned different regions, populations and time periods. Consistent results have been obtained from autopsy, clinical observation, and animal experiments.

The biological plausibility of the protective effect of magnesium is clear, but specificity is less clear due to the varied etiology of cardiovascular disease. In addition to an increased risk of death from cardiovascular disease, low magnesium in water is associated with possible motor nerve diseases, pregnancy complications (called preeclampsia), sudden death in young children and some types of cancer. Modern researchers suggest that drinking soft water with low calcium content can lead to fractures in children, neurodegenerative changes, premature birth, low birth weight of newborns and some types of cancer. The role of aqueous calcium in the development of cardiovascular diseases cannot be excluded.

International and national organizations responsible for drinking water quality should review guidelines for the treatment of demineralized water, making sure to define minimum values ​​for important indicators, including calcium, magnesium and salinity. Where necessary, authorized organizations have a responsibility to support and promote targeted research in this area to improve public health. If a quality manual is developed for individual substances required in demineralized water, the competent authorities must ensure that the document is applicable to consumers of home water treatment systems and bottled water.

14. Fluorine

Michael A. Lennon

School of Clinical Dentistry

University of Sheffield, United Kingdom

Helen Welton

Dennis O'Mullan

Oral Problems Research Center

University College, Cork, Republic of Ireland

Jean Ekstrand

Karolinska Institutet

Stockholm, Sweden

I. Introduction

Fluoride has both positive and negative effects on human health. From an oral health perspective, the incidence of dental disease is inversely related to fluoride concentrations in drinking water; There is also a connection between fluoride concentrations in water and fluorosis (1). From a general health perspective, in regions where fluoride concentrations are high in both water and food, cases of skeletal fluorosis and bone fractures are common. However, there are other sources of fluoride. Desalination and water treatment using membranes and anion exchange resins remove almost all fluoride from water. The use of such water for drinking purposes and the public health implications are highly dependent on specific circumstances. The main task is to enhance the positive effect of the presence of fluoride in drinking water (protection against caries), while minimizing unwanted problems of the oral cavity and health in general.

The etiology of oral diseases involves the interaction of bacteria and simple sugars (eg, sucrose) on the tooth surface. In the absence of such sugars in food and drinks, tooth decay will cease to be a significant problem. However, the problem will continue to exist with high sugar consumption until the right move is made to solve it. Removing fluoride from drinking water can potentially exacerbate existing or developing oral disease problems.

II. Fluorine intake into the human body

Fluorine is quite widespread in the lithosphere; often found as fluorspar, fluorapatite, and cryolite and is the 13th most abundant mineral on the globe. Fluorine is present in seawater at a concentration of 1.2-1.4 mg/l, in groundwater - up to 67 mg/l and in surface water - 0.1 mg/l (2). Fluoride is also found in foods, particularly fish and tea (3).

While most foods contain traces of fluoride, water and nondairy beverages are the primary sources of ingested fluoride, providing 66 to 80% of intake in U.S. adults, depending on the fluoride content of drinking water.

Additional sources of fluoride include toothpaste (especially for young children, who swallow most of the toothpaste), tea - in regions where tea drinking is an established tradition, coal (by inhalation) in some regions of China, where homes are heated with very high levels of coal. fluorine Absorption of ingested fluoride occurs in the stomach and small intestine (3).

For the most part, fluoride, whether originally present in water or added to it, is there as the free fluoride ion (3). Water hardness of 0-500 mg/l (in terms of CaCO3) affects ionic dissociation, which in turn slightly changes the bioavailability of fluoride (4). Absorption of a typical dose of fluoride varies from 100% (on an empty stomach) to 60% (with a calcium-rich breakfast).

III. The effect of fluoride from food and drinks on oral health

The effects of fluoride, naturally present in drinking water, on oral health were studied in the 1930s and 1940s by Trendley Dean and his colleagues at the US Public Health Service. A number of studies have been conducted throughout the United States; Studies have shown that with an increase in the natural fluoride content in water, the likelihood of fluorosis increased and the likelihood of caries decreased (5). In addition, based on Dean's results, it could be assumed that at a concentration of 1 mg/l, the incidence, severity and cosmetic effect of fluorosis are not a social problem, and resistance to caries increases significantly.

When analyzing these facts, a logical question arises: will artificial fluoridation of drinking water allow the effect to be repeated? The first study on this topic was conducted in Grand Rapids under the direction of the USPHS in 1945. The results obtained after 6 years of water fluoridation were published in 1953. Additional studies were conducted in 1945-46. in Illinois (USA) and Ontario (Canada).

Scientists in the Netherlands (1953), New Zealand (1954), the United Kingdom (1955-1956) and East Germany (1959) also dealt with this problem. The results were similar: a decrease in the incidence of dental caries was noted (5). Since the publication of the results, water fluoridation has become a common health promotion measure at the public level. Information about some of the countries involved in the project and the size of their population consuming artificially enriched water with fluoride is given in Table 1. The optimal concentration of fluoride, depending on climatic conditions, is 0.5-1.0 mg/l. Approximately 355 million people worldwide drink artificially fluoridated water. Additionally, about 50 million people drink water containing natural fluoride in a concentration of about

1 mg/l. Table 2 lists countries where populations of 1 million or more drink water rich in natural fluoride (1 mg/l). In some countries, particularly in parts of India, Africa and China, water may contain natural fluoride in quite high concentrations, above 1.5 mg/l, the standard established by the WHO Drinking Water Guidelines.

Many countries that have introduced artificial fluoride enrichment of water continue to monitor the incidence of dental caries and fluorosis using a cross-sectional random sample of children from 5 to 15 years of age. An excellent example of monitoring is the recently published report on children's oral health in Ireland (mainly fluoridated water) and the north of Ireland (non-fluoridated water) (7). (see table 3).

IV. Fluoride intake and health

The health effects of ingested fluoride were reviewed by Moulton in 1942, which predated the Grand Rapids study; Since then, the problem has been continually addressed by a number of organizations and individual scientists. More recently, IPCS (3) conducted a detailed review of fluoride and its effects on health. Studies and reviews have focused on bone fractures, skeletal fluorosis, cancer, and neonatal abnormalities, but have also addressed other abnormalities that may be caused or aggravated by fluoridation (1, 9, 10, 11, 12, 13, 14). No evidence or adverse effects from drinking water containing natural or added fluoride concentrations

0.5 – 1 mg/l was not detected, except for the cases of oral fluorosis described above. In addition, studies in areas of the United States where natural fluoride levels reach 8 mg/l have not shown any adverse effects from drinking such water. However, there is evidence from India and China where an increased risk of bone fractures results from long-term intake of large amounts of fluoride (cumulative intake of 14 mg/day) and suggests that the risk of fractures occurs with intakes above 6 mg/day (3).

The Institute of Medicine of the National Academy of Sciences of the United States (15) gives a recommended total dose of fluoride intake (from all sources) of 0.05 mg/kg of human body weight, arguing that taking this amount of fluoride will maximally reduce the risk of dental caries in the population, while not provoking negative side effects (for example, fluorosis). The US Environmental Protection Agency (EPA) considers the maximum permissible concentration (not causing skeletal fluorosis) to be 4 mg/l, and the value of 2 mg/l as not causing oral fluorosis. WHO drinking water quality guidelines recommend 1.5 mg/l (16). WHO emphasizes that when developing national standards, it is necessary to take into account climatic conditions, volume of consumption, and fluoride intake from other sources (water, air). WHO (16) notes that in regions with naturally high fluoride levels, it is difficult to achieve the recommended amount of fluoride consumed by the population.

Fluorine is not an element that is irreversibly bound in bone tissue. During the period of skeletal growth, a relatively large part of the fluoride entering the body accumulates in bone tissue. The “balance” of fluoride in the body, i.e. the difference between the amount entering and the amount released can be positive or negative. When fluoride is supplied from mother's and cow's milk, its content in biological fluids is very low (0.005 mg/l), and excretion in urine exceeds intake into the body, and a negative balance is observed. Fluoride enters the body of infants in very small quantities, so it is released from bone tissue into extracellular fluids and leaves the body in the urine, which leads to a negative balance. The situation with the adult population is the opposite - about 50% of fluoride entering the body is deposited in bone tissue, the remaining amount leaves the body through the excretory system. Thus, fluoride can be released from bone tissue slowly, but over a long period. This ratio is possible due to the fact that bone is not a frozen structure, but is constantly formed from nutrients entering the body (17,18).

V. Importance of desalting

Desalting removes virtually all the fluoride from seawater, so unless the outlet water is remineralized, it will contain grossly insufficient amounts of fluoride and other minerals. Many natural drinking waters are initially poor in minerals, including fluoride. The significance of this fact for public health is determined by the balance of benefits and risks.

When comparing residents of different continents and within a continent, a significant difference in incidence is visible. WHO recommended the introduction of the DMFT index, which is determined in children aged 12 years (this includes the number of affected, missing and healed teeth) as the most appropriate indicator; The WHO Oral Health Database provides expanded information (19). The etiology of caries involves the interaction of bacteria and simple sugars (for example, sucrose) coming from food. Without sugar in drinks and foods, this problem would become negligible. Under these circumstances, the public health objective is to prevent the harmful effects of excess fluoride concentrations in water.

However, when the risk of caries is high, the effect of removing fluoride from a centralized drinking water supply will be complex. In Scandinavian countries, where oral hygiene is high and alternative sources of fluoride (eg toothpaste) are widely used, the practice of permanently removing fluoride from drinking water may have little impact. On the other hand, in some developing countries, where oral hygiene is at a fairly low level, water fluoridation in an amount of 0.5-1 mg/l remains an important public concern. There are also countries where the situation is mixed. In particular, in the south of England, the incidence is under control without artificial fluoridation of water; in other regions, the north-west of England, incidence rates are higher and water fluoridation is an important measure.

VI. conclusions

The value of using demineralized water that is not subsequently enriched with fluorine depends on:

Concentrations of fluoride in drinking water from a specific source;

Climatic conditions and volume of water consumed;

Risk of caries (for example, eating sugar);

The level of knowledge about oral problems in society and the availability of alternative sources of fluoride for the population of a particular region.

However, it is necessary to address the issue of total intake from other sources and establish a reasonable lower limit for fluoride intake to prevent bone loss.

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