Total mineralization of water dry residue. General mineralization of water and methods for its elimination. Degree of bacteriological contamination of water
Total mineralization refers to the sum of particles dissolved in water. Salts that, under the influence of water molecules, break down into ions (dissociate) have maximum solubility.
The indicator of total mineralization of water reflects the content of salts in it, among which the most represented are compounds of sodium, potassium, calcium, magnesium and residues of hydrochloric, carbonic, and sulfuric acids.
Where is it used?
The value of total mineralization is used constantly and everywhere to characterize the composition of water. Its taste and physiological properties depend on the total concentration of dissolved salts. This, in particular, is the basis for the effect of healing waters at balneological resorts. In everyday practice, the indicator reflects the characteristics of the water of each region, the degree of natural purity, and cleaning efficiency.
The total mineralization of wastewater is a value that informs about the efficiency of treatment facilities at enterprises.
For packaged water of the first category, the standard value is 1000 mg/l. In bottled water of the highest category, the value of the total concentration of dissolved salts should be lower: from 200 mg/l to 500 mg/l.
In SanPiN, as well as in some other sources, the terms “total mineralization” and “dry residue” are considered synonymous. Strictly speaking, this is not entirely legal. The method for determining the dry residue is based on evaporation of the solvent. When heated, bicarbonate is destroyed with the release of carbon dioxide and turns into carbonate anion. Consequently, there is always a slight difference between the total mineralization indicators and the amount of dry residue.
Total mineralization is calculated by adding up all ion concentrations obtained in standard analyzes according to GOST standards. The method for determining this indicator is arithmetic. The resulting value will differ from the dry residue value by a small amount equal to half the concentration of carbonate anions.
Sometimes they talk about the presence of a small amount of organic substances in the total ion concentration indicator. This is not true. The mineralization indicator includes compounds of mineral origin. Organic compounds are not one of these.
Impact on human health
Most consumers like the taste of water containing about 600 mg/l of salts. People's attachments and habits differ. In regions where water has always had increased or decreased mineralization, taste adaptation occurs. The population considers it quite normal, even tasty. However, WHO considers concentrations exceeding 1000 mg/l unacceptable. Indicators equal to 1200 mg/l cause the presence of bitterness. The majority of the population does not like this water.
When discussing the physiological importance of the salt composition of water, it should be noted that no more than 7% of the required minerals enter the human body from this source. This way of saturating the body with useful elements is important, but not decisive.
Sources of pollution
Mineral components enter water from the soil, the composition of which is specific to each area. Poorly treated wastewater from industrial enterprises can make a noticeable contribution to the increase in salt concentration. To fully meet a person’s daily need for water, it makes sense to purchase bottled products with good taste.
Protect yourself from all risks and use the Aqua Market service.
Total mineralization is a total quantitative indicator of the content of substances dissolved in water. This parameter is also called the content of soluble solids or total salt content, since the substances dissolved in water are in the form of salts. The most common are inorganic salts (mainly bicarbonates, chlorides and sulfates of calcium, magnesium, potassium and sodium) and small amounts of organic substances soluble in water.
Very often the total mineralization of water is confused with dry residue. The solids are determined by evaporating a liter of water and weighing what is left. As a result, more volatile organic compounds dissolved in water are not taken into account. This leads to the fact that the total mineralization and dry residue may differ by a small amount - as a rule, no more than 10%.
Depending on the mineralization, natural waters can be divided into the following categories:
Mineralization g/dm 3 |
|
Ultra-fresh |
|
Waters with relatively high mineralization |
|
Salty |
|
High salinity waters |
|
The level of acceptability of total salinity in water varies greatly depending on local conditions and established habits. Typically, the taste of water is considered good if the total salt content is up to 600 mg/l. At values greater than 1000-1200 mg/l, water may cause complaints from consumers. Therefore, according to organoleptic indications, the WHO recommends an upper limit of water mineralization of 1000 mg/l.
The question of water with low salinity content is also open. It is believed that such water is too fresh and tasteless, although many thousands of people who drink reverse osmosis water, which has a very low salt content, on the contrary, find it more acceptable.
“Water” topics are increasingly heard in the press, and discussions are often made about the advantages or disadvantages of water from the point of view of supplying the body with minerals. Some materials published in reputable publications state quite categorically: “As you know, with water we receive up to 25% of the daily requirement of chemicals.” However, it is not possible to get to the original sources. Let's try to find an answer to the question: “How much minerals can an average person get from drinking water that meets sanitary standards?” In our reasoning we will be guided by simple everyday common sense and high school knowledge. Let's summarize the results in a table. Let us explain the contents of its columns, and at the same time the course of reasoning.
First you need to decide on several starting positions:
1. What minerals and in what quantities does a person need?
The question of the “mineral composition” of a person and, accordingly, the needs of his body is very complex. At the everyday level, we very easily juggle (unfortunately in the mass press too) with the terms “useful” elements, “harmful” or “toxic” elements, etc. Let's start with the fact that the very formulation of the question of the harmfulness and usefulness of chemical elements is relative. Even in ancient times it was known that it’s all about concentration. What is useful in minimal quantities can be a powerful poison in large quantities. A list of basic (vital) macroelements and several microelements from the Popular Medical Encyclopedia is given in the 1st column.
Data from the Popular Medical Encyclopedia were also used as the daily requirement norms (2nd column). Moreover, the minimum value for an adult man is taken as the base value (for teenagers and women, especially nursing mothers, these norms are often higher).
2. What is the mineral composition of “average” water?
It is clear that there is no “average” water and cannot be. As such, it is proposed to use hypothetical water, that is, “certain” water is accepted as consumed, in which the content of basic macro- and microelements is equal to the maximum permissible from the point of view of health safety - 3rd column of the table.
In the 4th column of the table, it is calculated how much water needs to be consumed in order to reach the daily requirement for each element. The huge assumption here is that in calculations the digestibility of minerals from water is taken as 100%, which is far from true.
3. What is the daily water consumption of the average person?
A person consumes an average of 1.2 liters of water per day directly in the form of liquid (drink and liquid food). By dividing this figure by the corresponding one from the 4th column, the percentage of intake of each element with water is calculated, which theoretically (taking into account all the above assumptions) can be received per day by the average person (5th column).
For comparison, the 6th column provides a mini-list of food sources of the same elements entering the body. A list of several products is used to illustrate the fact that the body receives one or another macro- or microelement not from one product, but, as a rule, a little from different ones.
The 7th column shows the amount of a particular product in grams, the consumption of which will give the body per day (with the same assumption of 100% digestibility as for water) the same amount of the corresponding macro- or microelement as hypothetical drinking water.
Element |
Daily requirement |
MPC in water |
Required amount of water to obtain 100% of the norm |
Theoretically possible % of min. Substances from water |
Alternative |
Quantity of product that provides macro- and microelements equal to that supplied with water |
Hard cheese |
12 g |
|||||
Phosphorus (phosphates) |
Mushrooms (dried) |
24 g |
||||
Watermelon |
27 g |
|||||
Dried apricots |
0.86 g |
|||||
Table salt |
0.6 g |
|||||
Chlorine (chlorides) |
Table salt |
0.5 g |
||||
Beef liver |
42 g |
|||||
White mushroom sushi. |
1.1 g |
|||||
Mackerel |
129 g |
|||||
Beef liver |
32 g |
|||||
Sea kale |
9 g |
From the data obtained it is clearly seen that we can theoretically obtain only 2 microelements - fluorine and iodine - from drinking water in sufficient quantities.
Of course, the data provided can in no way serve as nutritional recommendations. The whole science of dietetics deals with this. This table is intended only to illustrate the fact that it is much easier and, most importantly, more realistic to obtain all the macro- and microelements necessary for the body from food than from water.
Removing mineral salts from water
The process used to remove all minerals from water is called demineralization.
Demineralization carried out using ion exchange is called deionization. During this process, water is treated in two layers of ion exchange material to more effectively remove all dissolved salts. A cation exchange resin “charged” with hydrogen ions H + and an anion exchange resin “charged” with hydroxyl ions OH - are used simultaneously or sequentially. Since all salts soluble in water consist of cations and anions, a mixture of cation-exchange and anion-exchange resins completely replaces them in the purified water with hydrogen ions H + and hydroxyl OH -. Then, through a chemical reaction, these ions (positive and negative) combine to create water molecules. In fact, complete desalination of water occurs.
Deionized water has a wide range of industrial uses. It is used in the chemical and pharmaceutical industries, in the production of television cathode ray tubes, in industrial leather processing and in many other cases.
Distillation is based on the evaporation of the water being treated, followed by the concentration of steam. The technology is very energy-intensive; in addition, during the operation of the distiller, scale forms on the walls of the evaporator.
Electrodialysis is based on the ability of ions to move in a volume of water under the influence of an electric field. Ion-selective membranes allow either cations or anions to pass through. In the volume limited by ion-exchange membranes, the salt concentration decreases.
Reverse osmosis is a very important process that is part of highly professional water purification. Reverse osmosis was originally proposed for desalination of seawater. Together with filtration and ion exchange, reverse osmosis significantly expands the possibilities of water purification.
Its principle is extremely simple - water is forced through a semi-permeable thin-film membrane. Through the smallest pores, which have dimensions comparable to the size of a water molecule, only water molecules and low-molecular gases - oxygen, carbon dioxide - can leak under pressure, and all impurities remaining on the other side of the membrane are drained.
In terms of cleaning efficiency, membrane systems have no equal: it reaches almost 97-99.9% for any type of contaminant. The result is water that, in all its characteristics, resembles distilled or highly demineralized water.
Deep cleaning of the membrane can only be done with water that has undergone preliminary comprehensive cleaning. Removal of sand, rust and other insoluble suspended matter is carried out by a mechanical cartridge with cells up to 5 microns. A cartridge based on high-quality granulated coconut carbon absorbs compounds of iron, aluminum, heavy and radioactive metals, free chlorine and microorganisms dissolved in water. The last stage of the preliminary stage is very important, where the final purification from the smallest doses of chlorine and organochlorine compounds, which have a destructive effect on the membrane material, occurs. It is produced in a cartridge from pressed coconut charcoal.
After comprehensive pre-treatment, the water is supplied to a membrane, after which drinking water of the highest purity class is obtained. And in order to remove dissolved gases from it, which give an unpleasant odor and taste, the water at the final stage is passed through high-quality pressed activated carbon with the addition of silver. The fact that the water after purification in the membrane system is almost completely free of mineral salts has been causing lively discussions for many years. Although it is much more efficient to obtain the amount of macro- and microelements necessary for the body through food (see above), many are so accustomed to the taste that mineral salts give water that in their absence the water seems tasteless and “lifeless.” However, it turns out to be so difficult and expensive to completely remove harmful impurities while maintaining minerals in useful concentrations that usually the water is first purified as much as possible, and then additives are added if necessary.
Home reverse osmosis installations are usually equipped with storage tanks for purified water, since the rate of water filtration through the membrane is low. The storage tank, usually with a total capacity of 12 liters, is a hydraulic accumulator divided inside by an elastic silicone partition. On one side, the partition is in contact with purified water, and on the other, air is pumped under a pressure of 0.5 atm. Such a tank is capable of storing no more than 6-8 liters of purified water. This usually takes from 2 to 6 hours. To ensure the operability of the system when the pressure in the line is insufficient (less than 2.5 - 2.8 atm), a booster pump is installed.
It should be noted that if the source water is very hard and contains an excessive amount of mechanical or dissolved impurities, then before the reverse osmosis system it is recommended to install additional water treatment systems (iron remover, softener, disinfection systems, mechanical cleaning, etc.).
Theoretically, membranes remove almost all microorganisms known to us, including viruses, however, when used in domestic drinking water systems, membranes cannot provide complete protection against microorganisms. Potential gasket leaks and manufacturing defects may allow some microorganisms to enter the treated water. This is why small home reverse osmosis systems should not be used as the primary means of eliminating biological contamination.
It is very important to understand that the reverse osmosis process occurs only when the water pressure in the system is at least 2.5-2.8 atm. The fact is that on the semi-permeable membrane on the side of purified (desalted) water there is always excess osmotic pressure, which interferes with the filtration process. It is this pressure that must be overcome.
IRON (Fe)
Typically, iron is present in natural waters in various forms:
1. divalent iron ions, soluble in water (Fe 2+);
2. trivalent iron ions, soluble only in very acidic water (Fe 3+);
3. insoluble ferric hydroxide;
4. ferric oxide (Fe 2 O 3), present in the form of rust particles from pipes;
5. in combination with organic compounds or iron bacteria. Iron bacteria often live in water containing iron. As these bacteria multiply, they can form red-brown growths that can clog pipes and reduce water pressure. The decaying mass of these iron bacteria can cause water to smell, taste, and stain.
Iron is rarely found in terrestrial bodies of water. When it reaches the surface, water containing dissolved iron is usually clear and colorless, with a strong iron taste. Under the influence of air, the water acquires a kind of milky haze, which soon turns red (a precipitate of iron hydroxide appears). This water leaves marks on almost everything. Even with an iron content of 0.3 mg/l in water, it leaves rusty stains on any surface.
The presence of iron in water is extremely undesirable. Excess iron accumulates in the human body and destroys the liver, immune system, and increases the risk of heart attack.
A satisfactory method of removing small amounts of dissolved iron from water is the use of ion exchange softeners. It is impossible to immediately say how much iron can be removed. The answer to this question in each individual case depends on the design of the device, as well as on other specific conditions. Iron, present in water in undissolved form, is not removed by softeners; moreover, it spoils them. Therefore, in the case of using softeners to remove dissolved iron, for example, from a well, in no case should the well water be allowed to come into contact with air.
The most effective way to remove moderate concentrations of iron may be to use oxidizing filters. Such a filter should be installed on the water pipe in front of the water softener. Oxidizing filters typically contain a filter media coated with manganese dioxide (MnO2). This may be manganese-treated glauconitic sand, synthetic manganese material, natural manganese ore and other similar materials. Manganese oxide converts soluble ferrous ions found in water into ferric iron. In addition, manganese compounds are a powerful catalyst for the oxidation of ferrous iron with oxygen dissolved in water. Since there is very little oxygen in underground water, for a more efficient oxidation process, the water in front of the deferrization filter is saturated with oxygen (air). As insoluble ferric hydroxide forms, it is filtered out of the water by the granular material contained in the filter.
In the case of high iron concentrations, small pumps, ejectors and other devices can be used to add chemical oxidizers, such as sodium hypochlorite (household bleach "Belizna") or potassium permanganate solution, to the water. Just like manganese dioxide in iron filters, these chemical oxidizers convert dissolved ferrous iron into insoluble ferric iron.
MANGANESE (Mn)
Manganese is usually found in iron-containing water. Chemically, it can be considered related to iron, because. it is found in the same compounds. Manganese is most often present in water in the form of bicarbonate or hydroxide, much less often it is found in the form of manganese sulfate. When manganese comes into contact with anything, it leaves dark brown or black marks, even at minimal concentrations in water. Manganese sediment appears during plumbing and plumbing work, as a result of which the water often leaves a black sediment and becomes cloudy. Excess manganese is dangerous: its accumulation in the body can lead to a serious disease - Parkinson's disease.
To solve the problem of manganese removal, the same methods are suitable as for iron.
Reverse osmosis is a method that can be used to reduce the concentration of fluoride in water at home.
SODIUM (Na)
Sodium salts are present in all natural water. They do not form scale when boiled, nor a cheesy sediment when mixed with soap. Their high concentrations increase the corrosive effect of water and can give it an unpleasant taste. Large amounts of sodium ions interfere with the operation of ion exchange water softeners. Where the water is very hard and contains a lot of sodium, softened water can retain many ions that cause hardness.
An effective method for removing sodium from water at home is reverse osmosis.
NITRATES (NO 3 -)
Typically, the soil contains small amounts of natural nitrates. The presence of nitrates in water indicates that it is contaminated with organic substances. Basically, water contaminated with nitrates is found in shallow wells and wells, but sometimes such water occurs in deep wells. Even such a low concentration of nitrates, such as 10-20 mg/l, can cause serious illness in children, and cases of death are known.
Nitrates can be removed from water using reverse osmosis.
CHLORIDES AND SULPHATES (Cl - , SO4 2-)
Almost all natural water contains chloride and sulfate ions. Low to moderate concentrations of these ions give water a pleasant taste and their presence is desirable. Excessive concentrations can make the water unpleasant to drink. Both chlorides and sulfates contribute to the total mineral content of water. The total concentration of these substances can have a variety of effects - from giving water increased hardness to electrochemical corrosion. Water containing more than 250 mg/l of sulfates acquires a pronounced “medicinal taste”. In excess concentrations, sulfates can also act as a laxative.
Water can be purified from chlorides and sulfates using reverse osmosis.
HYDROGEN Sulfide (H 2 S)
Hydrogen sulfide is a gas that is sometimes found in water. The presence of this gas can be easily determined by the disgusting smell of “rotten eggs”, which appears even at low concentrations (0.5 mg/l).
There are several ways to remove hydrogen sulfide from water. Most of them come down to oxidation and conversion of gas into pure sulfur. Then, this insoluble yellow powder is removed by filtration. An activated carbon filter is sufficient to remove very low concentrations of hydrogen sulfide. In this case, the coal simply adsorbs gas onto its surface.
PHENOL (C 6 H 5 OH)
One of the most dangerous types of industrial waste is phenol. In chlorinated water, phenol enters into chemical reactions with chlorine and creates chlorophenol compounds that have an unpleasant “medicinal” taste and odor. In this case, an unpleasant odor appears at phenol concentrations equal to one part per billion. Phenol and chlorophenolic compounds are removed by passing water through activated carbon.
It has been established that the main radiation background on our planet (at least for now) is created by natural sources of radiation. According to scientists, the share of natural sources of radiation in the total dose accumulated by the average person throughout his life is 87%. The remaining 13% comes from human-made sources. Of these, 11.5% (or almost 88.5% of the “artificial” component of the radiation dose) is formed through the use of radioisotopes in medical practice. And only the remaining 1.5% are the result of the consequences of nuclear explosions, emissions from nuclear power plants, leaks from nuclear waste storage facilities, etc.
Among natural sources of radiation, radon confidently holds the palm, causing up to 32% of the total radiation dose.
Radon is a radioactive natural gas, absolutely transparent, tasteless, odorless, and much heavier than air. It is formed in the bowels of the Earth as a result of the decay of uranium, which, although in small quantities, is part of almost all types of soils and rocks. The uranium content is especially high (up to 2 mg/l) in granite rocks.
Accordingly, in areas where granite is the predominant rock-forming element, one can expect increased radon content. It is not detected by standard methods. If there is a reasonable suspicion of the presence of radon, it is necessary to use special equipment for measurements. Radon gradually seeps from the depths to the surface, where it immediately dissipates in the air, as a result of which its concentration remains negligible and does not pose a danger. Problems arise when there is not enough air exchange, for example in houses and other rooms. In this case, the radon content in a closed room can reach dangerous concentrations. Radon enters the human body through breathing and can cause harmful health effects. According to the US Public Health Service, radon is the second leading cause of lung cancer in people after smoking.
Radon dissolves very well in water, and when groundwater comes into contact with radon, it becomes saturated with it very quickly. When wells are used to supply a house with water, radon enters the house with water. Radon dissolved in water acts in two ways. On the one hand, it enters the digestive system along with water. On the other hand, when water flows from a faucet, radon is released and can accumulate in significant quantities in kitchens and bathrooms. The concentration of radon in a kitchen or bathroom can be 30-40 times higher than in other rooms, such as living rooms. Inhalation exposure to radon is considered more dangerous to health.
A measure of radioactivity is the activity of the radionuclide in the source. Activity is equal to the ratio of the number of spontaneous nuclear transformations in this source over a short time interval to the value of this interval. In the SI system it is measured in Becquerels (Bq, Bq), which corresponds to 1 decay per second. The activity content of a substance is often assessed per unit weight of the substance (Bq/kg) or its volume (Bq/l, Bq/cubic m).
In Novosibirsk, the level of radon in well water ranges from 10 to 100 Bq/l, in some areas (Nizhnyaya Eltsovka, Akademgorodok, etc.) reaching several hundred Bq/l. In the Russian Radiation Safety Standards (NRB-99), the maximum level of radon content in water at which intervention is required is set at 60 Bq/l (American standards are much stricter - 11 Bq/l).
One of the most effective methods of combating radon is water aeration (the “bubbling” of water with air bubbles, in which almost all the radon literally “flies to the wind”). Therefore, those who use municipal water have practically nothing to worry about, since aeration is part of the standard water treatment procedure at city water treatment plants. As for individual users of well water, studies conducted in the USA have shown the fairly high efficiency of activated carbon. A filter based on high-quality activated carbon is capable of removing up to 99.7% of radon. However, over time this figure drops to 79%. Using a softener in front of the carbon filter allows you to increase the latter figure to 85%.
information taken from the site http://aquafreshsystems.ru/index.htm
Drinking water must meet certain established standards and GOSTs.
There are several standards for drinking water:
- Russian standard, determined by relevant norms and GOSTs;
- WHO (World Health Organization) standard;
- US standard and European Union (EU) standard.
The quality of drinking water on the territory of the Russian Federation is determined by the norms of sanitary and epidemiological rules and standards approved by the chief state sanitary doctor of the Russian Federation. The main Russian GOST for drinking water is the Sanitary Rules and Norms (SanPiN) introduced in 2002.
In accordance with current standards and regulations, the term high quality drinking water means:
- water with appropriate organoleptic characteristics - transparent, odorless and with a pleasant taste;
- water with pH = 7-7.5 and hardness not higher than 7 mmol/l;
- water in which the total amount of useful minerals is no more than 1 g/l;
- water in which harmful chemical impurities are either tenths or hundredths of their maximum permissible concentrations, or are absent altogether (that is, their concentrations are so small that they are beyond the capabilities of modern analytical methods);
- water in which there are practically no pathogenic bacteria and viruses.
An approximate standard for water is shown in Table 1:
Table 1. Approximate water standard
Index | Meaning |
|
---|---|---|
Turbidity | up to 1.5 mg/l. |
|
Chroma | up to 20 degrees |
|
Odors and tastes at 20 °C. | none |
|
Sulfates | up to 5-30 mg/l. |
|
Hydrocarbonates | 140-300 mg/l. |
|
pH value | ||
Overall hardness | 1.5-2.5 mEq/l. |
|
*At a concentration of 2-8 mg/l, fluorosis is possible. At a concentration of 1.4-1.6 mg/l, dental caries develops. | 0.7-1.5 mg/l. |
|
Iron | up to 0.3 mg/l. |
|
Manganese | up to 0.1 mg/l. |
|
Beryllium | up to 0.0002 mg/l. |
|
Molybdenum | up to 0.05 mg/l. |
|
up to 0.05 mg/l. |
||
up to 0.1 mg/l. |
||
up to 0.001 mg/l. |
||
Strontium | ||
1.2·10(-10) Ci/l. |
||
Copper | ||
Aluminum | up to 0.5 mg/l. |
|
Zinc | ||
Hexametaphosphate | up to 3.5 mg/l. |
|
Tripolyphosphate | up to 3.5 mg/l. |
|
Polyacrylamide | ||
up to 3.3 mg/l. |
||
Nitrates | up to 45 mg/l. |
|
The total number of bacteria in 1 ml is up to 100. | ||
Coli index | ||
Coli titer | ||
Cysts of pathogenic intestinal protozoa | absence. |
|
Sum of halogen-containing compounds | up to 0.1 mg/l. |
|
Chloroform | up to 0.06 mg/l. |
|
Carbon tetrachloride | up to 0.006 mg/l. |
|
Petroleum products | up to 0.3 mg/l. |
|
Volatile phenols | up to 0.001 mg/l. |
|
up to 0.001 mg/l. |
||
up to 0.0005 mg/l. |
||
Hydrogen sulfide | no more than 0.003 |
Table 2 contains general requirements for the composition and properties of water, indicating acceptable standards. The quality of water for water intake is assessed not only by the presence of toxic and bad-smelling substances in it, but also by changes in the physical and chemical parameters and properties of water.
Table 2. Indicator of the composition and properties of reservoir water
Indicator of the composition and properties of water | Requirements and standards |
---|---|
Suspended solids | |
Floating impurities | There should be no floating films, oil stains or accumulation of other impurities on the surface of the water. |
Smells and tastes | Water should not acquire odors and tastes with an intensity of more than one point |
Should not be detected in a column of 20 centimeters |
|
Temperature | Summer water temperature as a result of wastewater discharge should not increase by more than 3 degrees compared to the average monthly temperature of the hottest month in the last 10 years |
pH value | |
Mineral composition | Should not exceed 1000 mg/l in dry residue, chlorides - 350 mg/l, sulfates - 500 mg/l |
Dissolved oxygen | Not less than 4 mg/l |
BOD at 20 deg | No more than 3 mg/l |
No more than 15 mg/l |
Note: The water sample is analyzed for the following indicators: total hardness, pH, iron content, color, odor, nitrates, nitrites, hydrogen sulfide, water microbiology, etc. In addition, the performance of water purification equipment, which depends on the peak load of water consumption, is of great importance object.
A short list of inorganic and organic substances, as well as bacteria and viruses in drinking water that have an adverse effect on the human body, is presented in Table 3.
Table 3.
The influence of inorganic and inorganic substances, bacteria and viruses on the human body
Name of the substance, bacteria or virus | Human organs and systems, |
---|---|
Inorganic substances |
|
Beryllium | Gastrointestinal tract |
Kidneys, liver |
|
Skin, blood; carcinogen |
|
Nitrates and nitrites | |
Kidneys, slow development |
|
Gastrointestinal tract, blood, kidneys, liver |
|
Nervous system |
|
Organic matter |
|
Carcinogen |
|
Pesticides (DDT, anachlor, heptachlor) | Carcinogens |
Chlorine compounds (vinyl chloride, dichloroethane) | Blood, kidneys, liver |
Liver, kidneys, metabolism |
|
Nervous system, kidneys, liver |
|
Bacteria and viruses |
|
Escherichia coli | Gastrointestinal tract |
Enteroviruses | Gastrointestinal tract |
Hepatitis virus |
Drinking water parameters are divided into three groups:
- organoleptic properties;
- indicators of bacterial and sanitary-chemical pollution;
- Chemical properties
Organoleptic characteristics of drinking water- assessments of smell, taste, color and turbidity, each person can perform independently.
Chemical properties waters are characterized by the following indicators: hardness, oxidability, pH value, general mineralization - the content of dissolved salts and elements in water.
Calcium
Calcium is an extremely important mineral. The human body contains up to 30-40 kg of calcium, 99% of which is found in bones and teeth. Calcium is involved in the formation of bones, it is necessary for the stimulation of nerves, muscle function, blood clotting and the transmission of hormonal signals. In addition, calcium regulates the activity of various enzymes and has anti-inflammatory and antiallergic properties. A lack of calcium leads to muscle dysfunction and is the cause of osteoporosis.
Magnesium
Magnesium, like potassium, is a very important element in the cell. It activates enzymes that regulate various chemical reactions in the body, takes part in the functioning of muscle and nerve cells, and plays a key role in the normal functioning of the heart and blood circulation. The body loses magnesium when drinking alcohol. The consequences may include irritability, poor concentration, muscle cramps and heart rhythm disturbances.
Sodium
Sodium is a vital mineral, the main task of which is, together with chlorides, to regulate the water and acid-base balance of the body. Together with potassium, sodium plays a significant role in the formation of a nerve impulse.
Potassium
Potassium is a mineral that plays an important role in the functioning of muscle and nerve cells. It is necessary for the muscle cells of the heart, which need sufficient potassium. A lack of potassium can be expressed by general fatigue and muscle cramps, as well as muscle weakness or heart rhythm disturbances.
Chlorides
Chlorides determine the amount of chlorine found in the body, which helps maintain the acid-base balance of fluids and plays an important role in the production of hydrochloric acid in the stomach.
Chlorine
Chlorine is used to disinfect water because... chlorine is a powerful oxidizing agent that can destroy pathogens. However, in the rivers and lakes from which water is drawn, there are many substances that got there with wastewater, and chlorine reacts with some of them. As a result, much more toxic compounds are formed than chlorine itself. For example, chlorine compounds with phenol; They give water an unpleasant odor and affect the liver and kidneys, but in small concentrations they are not very dangerous. However, it is possible to combine chlorine with benzene, toluene, gasoline, with the formation of dioxin, chloroform, chlorotoluene and other carcinogenic substances. It is not economically feasible to disinfect water without chlorine, since alternative methods of water disinfection involving the use of ozone gas, ultraviolet light and silver for this purpose are expensive.
Sulfates
Sulfates are salts of sulfuric acid, which, in combination with magnesium and sodium, activate digestion. Sulfates can also help the kidneys eliminate harmful substances and prevent the formation of urinary stones.
Fluorides
In addition to the well-known anti-caries effect of fluorine, its ability to serve as a biocatalyst for mineralization processes is noted, which is used for medicinal purposes in osteoporosis, rickets and other diseases. Natural waters with a high fluorine content in combination with calcium have a positive effect on the body’s resistance to radiation damage. Fluorine is able to reduce the concentration of strontium in bone tissue by approximately 40%, and this process is not accompanied by depletion of calcium in the skeleton.
Rigidity
The concept of water hardness is usually associated with the cations of calcium (Ca 2+), magnesium (Mg 2+) and iron (Fe 2+, Fe 3+). They interact with anions, forming compounds (hardness salts) that can precipitate. Monovalent cations (for example, sodium Na +) do not have this property. Hard water contains a lot of mineral salts, which cause scale - rock salt - to form on the walls of dishes, boilers and other units. Hard water is destructive and unsuitable for water supply systems. Tea does not brew well in such water and soap does not dissolve well. Table 4 lists the major metal cations that cause hardness and the anions with which they are associated.
Table 4.
Major metal cations causing hardness and the anions with which they are associated
In practice, strontium, iron and manganese have such a small effect on hardness that they are usually neglected. Aluminum (Al 3+ ) and ferric iron (Fe 3+ ) also contribute to hardness, but at the pH levels found in natural waters, their solubility and contribution to hardness are small.
The source of calcium and magnesium ions are natural deposits of limestone, gypsum and dolomite. Ca 2+ and Mg 2+ ions enter water as a result of the interaction of dissolved carbon dioxide with minerals and other processes of dissolution and chemical weathering of rocks.
Water from underground sources has high hardness, and water from surface sources has relatively low hardness (3-6 mEq/l). The content of hardness salts in drinking water within the range of 1 - 4 mEq/l promotes normal metabolic processes in the body. With drinking water, a person receives 1-2 g of mineral salts per day, and, due to the fact that, unlike many foods, the ions in water are in a dissolved (hydrated) state, their absorption by the body increases by an order of magnitude. Soft water should have a hardness of no more than 10 mEq/l. In recent years, it has been suggested that water with a low content of hardness salts contributes to the development of cardiovascular diseases.
pH value
The pH value can range from 0 to 14 and indicates whether a solution is acidic, neutral or alkaline. If the pH value is less than 7, then the solution is acidic, such as lemon juice, which has a pH value of 2-3. Solutions with a pH value of 7 are neutral, such as distilled water. Solutions with a pH value greater than 7 are alkaline.
Hydrocarbonates
Bicarbonates are an element necessary for the body that regulates the acid-base balance. It binds and neutralizes increased acidity, for example, gastric juice, blood, muscles, without harming them. Together with carbon dioxide, bicarbonate forms a so-called buffer system, which maintains blood pH.
General mineralization
Total mineralization is an indicator of the content of substances dissolved in water or total salt content, since substances dissolved in water are in the form of salts (bicarbonates, chlorides and sulfates of calcium, magnesium, potassium and sodium). Water from surface sources has less dense sediment than water from underground sources, i.e. contains less dissolved salts. The limit of mineralization of drinking water (dry residue) of 1000 mg/l was at one time established on an organoleptic basis. Waters with a high salt content have a brackish or bitter taste. They are allowed to be contained in water at the sensation threshold level: 350 mg/l for chlorides and 500 mg/l for sulfates. The lower limit of mineralization, at which the body's homeostasis is maintained by adaptive reactions, is a dry residue of 100 mg/l, the optimal level of mineralization is 200-400 mg/l. In this case, the minimum calcium content should be at least 25 mg/l, magnesium -10 mg/l. According to general mineralization, waters are divided into the following categories (Table 5):
Table 5. Categories of water according to the degree of total mineralization
Microelements
Microelements are a group of mineral substances vital for the body. The human body needs them in small quantities, but they are very important. Microelements are important components of proteins, hormones, enzymes, participate in many metabolic functions, activate the immune system and strengthen immune defense. These include iron, silicon, zinc, manganese, copper, selenium, chromium, molybdenum.
Water oxidability
Oxidability is determined by the content of dissolved organic substances in water and can serve as an indicator of contamination of the source with wastewater. For wells, wastewater that contains proteins, fats, carbohydrates, organic acids, ethers, alcohols, phenols, oil, etc. is especially dangerous.
Degree of bacteriological contamination of water
It is determined by the number of bacteria contained in 1 cm 3 of water and should be up to 100. Water from surface sources contains bacteria introduced by sewage and rainwater, animals, etc. Water from underground artesian springs is usually not contaminated with bacteria.
There are pathogenic (disease-causing) and saprophytic bacteria. To assess the contamination of water with pathogenic bacteria, the content of E. coli in it is determined. Bacterial contamination is measured by coli titer and coli index. Coli titer - the volume of water containing one E. coli should be less than 300. Coli index - the number of E. coli contained in 1 liter of water should be up to 3.
MPC
The maximum permissible concentration of impurities of harmful substances, which become harmful when exceeded, is as follows: EU, US and WHO standards determine that it should not exist at all. The Russian standard gives the following figures: no more than one hundred microorganisms per cubic centimeter and no more than three bacteria such as E. coli in one liter of water, which, in principle, corresponds to international standards.
Table 6 shows the MPC values for some substances in water bodies for domestic and drinking purposes.
Table 6. MPC values for some substances in water bodies for domestic and drinking purposes.
The standards for the most toxic substances in water are given in Table 7 (data taken from the book by M. Akhmanov. The Water We Drink. M.: Eksmo, 2006):
Table 7. Standards for the most toxic substances in water
Note. If the MPC is hundreds of thousands of micrograms, then the substance is not harmful. If the MPC is hundreds to thousands of micrograms, then such a substance can be dangerous. If the maximum permissible concentration is within units, tenths and hundredths of a microgram, then this substance is almost always poisonous (benzene, vinyl chloride, arsenic, mercury, lead).
Drinking water standards of the EU countries (Western Europe) and the USA, recommendations of the World Health Organization and domestic standards are shown in Table 8 (according to M. Akhmanov. The water we drink. M.: Eksmo, 2006)
Table 8. Drinking water standards in Russia and abroad*
Parameter | MPC, micrograms per liter (µg/l) |
|||
---|---|---|---|---|
Russia |
||||
Acrylamide | ||||
Polyacrylamide | ||||
Aluminum | ||||
Benzopyrene | ||||
Beryllium | ||||
Vinyl chloride | ||||
Dichloroethane | ||||
Manganese | ||||
Molybdenum | ||||
Pesticides | ||||
Strontium | ||||
Sulfates | ||||
Trichlorethyl | ||||
Chloroform | ||||
Note*. Data taken from the book by M. Akhmanov. The water we drink. M.: Eksmo, 2006
PAHs are polycyclic aromatic hydrocarbons similar to benzopyrene.
- In EU data, the abbreviation is week. (week) is marked with the average weekly dose of a substance that is guaranteed not to cause harm to the human body.
- The asterisk mark indicates those MPC values in Russian standards that are taken from scientific articles or new Sanitary rules and regulations. Other values are indicated in GOST.
- The two asterisks mark those MPC values in American standards that are called secondary: they are not included in the national standard, but can be legalized by state authorities.
- A dash in any position in the table means that there is no data for that connection.
Tables 7-8 present various groups of substances: light and heavy metals (the latter include many metals, such as aluminum, titanium, chromium, iron, nickel, copper, zinc, cadmium, lead, mercury, etc.), inorganic and organic connections. The data is generalized and most consistent with Russian and European standards. The US and WHO standards describe organic substances in more detail. Thus, the US standard lists about thirty types of hazardous organics. The most detailed are the WHO recommendations, which contain the following separate lists of substances:
- inorganic substances (mainly heavy metals, nitrates and nitrites);
- organic substances (about thirty), pesticides (more than forty);
- substances used to disinfect water (mainly various compounds of bromine and chlorine - more than twenty);
- substances that affect the taste, color and smell of water.
The standards list substances that do not adversely affect health at maximum permissible concentrations in water - these include, in particular, silver and tin. In some WHO recommendations against certain substances there is a note: There is no reliable data to establish a standard. This means that work on studying them in the body continues: hundreds of thousands of compounds are known, but only a few of them have been studied in terms of their effect on the human body.
The Russian GOST does not contain maximum permissible concentrations for a number of substances specified in foreign standards. Requirements for the quality of drinking water in the Russian Federation must comply with GOST standards and the new SanPiN. There are other regulatory documents that provide a list of more than 1,300 harmful substances and their maximum permissible concentrations. For most indicators, the Russian standard either corresponds to foreign ones, or sets standards in some cases more stringent, in others softer. If we compare a number of MPC indicators given in Russian and foreign standards, for example, for aluminum: the MPC for it is 200 μg/l according to foreign standards and 500 μg/l according to Russian standards. Despite the discrepancy of two and a half times, these values are of the same order of magnitude. For iron (200-300 µg/l), copper (1000-2000 µg/l), mercury (1-2 µg/l), lead (10-30 µg/l) - for these substances compliance with the MPC is met, then there are differences of no more than two to three times. According to the EU standard, the presence of benzopyrene is allowed within the limit of 0.01 μg/l (or 10 ng/l), for aluminum the norm is 100 μg/l (or 0.1 mg/l), and sodium, sulfate and chlorine may be present in water in quantities of 200,000-250,000 µg/l (that is, 200-250 mg/l, or 0.2-0.25 g/l). The difference in maximum permissible concentrations in the standards of the EU, USA, WHO and Russia is five to six times, and in some cases - ten, twenty, hundred. The MPC for arsenic in Russia is the same as in the USA, the standard for benzopyrene is stricter than in Europe and the USA, and only benzene can be a reason to doubt the correctness of the Russian GOST indicators.
Ph.D. O.V. Mosin
Lit. source : M. Akhmanova. The water we drink. Moscow: Eksmo, 2006
Salinity or mineralization is an indicator of the amount of dissolved substances contained in water, mainly inorganic salts. Abroad, mineralization is also called “total dissolved solids” (TDS).
Usually mineralization is calculated in milligrams per liter (mg/l), but given that the unit of measurement “liter” is not systemic, it is more correct to express mineralization in mg/dm3, at higher concentrations - in grams per liter (g/l, g/ dm3). Also, the level of mineralization can be expressed in parts per million particles of water - parts per million (ppm). The relationship between the units of measurement in mg/l and ppm is almost equal and for simplicity we can assume that 1 mg/l = 1 ppm.
Depending on the general mineralization, waters are divided into the following types: low mineralization (1–2 g/l), low mineralization (2–5 g/l), medium mineralization (5–15 g/l), high mineralization (15–30 g /l), brine mineral waters (35–150 g/l), strong brine waters (150 g/l and above).
The quality of drinking water is regulated in Russia by a number of SanPin standards, which standardize the quality of tap and bottled drinking water.
The World Health Organization (WHO) does not impose restrictions on the total salinity of water. But water with a mineralization of more than 1000–1200 mg/l can change its taste and thereby cause complaints. Therefore, WHO, based on organoleptic indications, recommends a limit of total mineralization of drinking water of 1000 mg/l, although the level may vary depending on established habits or local conditions.
In addition to bottled drinking water, which can be used for drinking every day, there are bottled mineral waters divided into three groups: table, medicinal and medicinal-table.
In accordance with hygienic requirements for the quality of drinking water, the total mineralization should not exceed 1000 mg/dm3. In agreement with the authorities of the Department of Sanitary and Epidemiological Supervision, for a water supply system supplying water without appropriate treatment (for example, from artesian wells), an increase in mineralization to 1500 mg/dm3 is allowed.
Distilled water is water that has been maximally purified from all kinds of impurities (micro- and macroelements, salts, foreign inclusions) using the distillation process. The presence of heavy metals, viruses, and bacteria in its composition is also excluded. It turns out only when certain conditions are created by man; it does not exist in nature as such, there are no microorganisms or useful minerals in it. Quality is standardized by GOST 6709–72.
There is a point of view that constantly using water with low salt content for drinking purposes leads to “washing out” of salts, including calcium, from the body.
The purpose of the work is to determine the salt content of various types of drinking water. To achieve the goal, the following tasks were identified: 1) review the literature on the research topic; 2) measure the salt content of various types of water; 3) compare the obtained salt content values with the standard ones.
Research methodology
Measurements were made using a Multitest KSL-101 conductometer. The KSL-101 conductometer is designed to measure the specific electrical conductivity of liquids and total salt content in terms of sodium chloride.
The operation of the conductometer is based on the contact method of measuring the specific electrical conductivity of liquids. The device belongs to portable semi-automatic wide-range digital measuring instruments with temperature compensation. The range is selected automatically. The indicator displays four significant decimal digits, the output resolution is equal to the least significant digit.
The conductometer provides automatic temperature compensation of measurement results using a special electrode. The appearance of the device and electrodes is shown in Fig. 1.
The salt content of five water samples was determined.
Rice. 1. Appearance of the conductivity meter Multitest KSL-101 and the measurement process
For analysis, we purchased three types of water from the supermarket: 1) Shadrinskaya medical canteen No. 319 (Ekaterinburg), according to the manufacturer, salt content from 6 to 9.1 g/l; Narzan natural carbonation (Kislovodsk), according to the manufacturer, salt content is from 2 to 3 g/l. “Lux water” (Chelyabinsk), according to the manufacturer, salt content is up to 400 mg/l.
In addition, analyzes of tap water were carried out; for this purpose, water from a cold tap was drained for 15 minutes and then taken into a clean container. The content of boiled tap water was also measured, since tap water is usually used for drinking after boiling.
We measured the electrical conductivity of distilled water, prepared in the laboratory of the Faculty of Chemistry of SUSU (National Research University) in Chelyabinsk.
To measure, the electrodes were placed in a glass of water, the “Start” button was pressed, and the value was waited for 3 minutes. We recorded the result displayed on the scoreboard.
Research results
The salt content of drinking water and distilled water was measured. The measurement results are presented in Table 1. Table 1 also shows the standard values of salt content (in accordance with accepted standards or manufacturer’s requirements).
Of the studied waters, distilled water has the lowest salt content - 3.1 mg/l, which meets the requirements of GOST 6709–72.
Three types of water purchased in stores in Chelyabinsk were studied. Lux water is characterized by the lowest salt content - 120 mg/l, this value is lower than 400 mg/l as established by the manufacturer. This water is considered table water in terms of salt content and can be used for drinking purposes every day.
The waters of Shadrinskaya medicinal and dining room No. 319 and Narzan of natural carbonation, in terms of their salt content, are classified as medicinal and canteen waters. But in both cases, the obtained salt content values were lower than the lower value declared by the manufacturer. For Shadrinskaya water - 3573 mg/l versus 6000 mg/l, for Narzan - 1709 mg/l versus 2000 mg/l. This may be due to the fact that the products are not original.
Table 1
Measurement results
№ p/p |
Name of water |
Standard, mg/l |
|
distilled |
5 (GOST 6709–72) |
||
water supply |
|||
Boiled tap |
|||
Shadrinskaya |
|||
Lux water |
Conclusion
During our research, we measured the salt content of six types of water. Tap water meets the requirements of SanPiN 2.1.4.1074–01 for salt content. After boiling, its salt content decreases slightly. The lowest salt content of the studied drinking waters purchased in city stores is characterized by Lux water - 120 mg/l. This water is considered table water in terms of salt content and can be used for drinking purposes every day.
Literature:
- Taube P. R., A. G. Baranova Chemistry and microbiology of water. - M. Higher. school, 1983. - 280 p.
- Andruz J. Introduction to Environmental Chemistry / J. Andruz, P. Brimblecombe, T. Jickels, P. Liss; Per. from English A. G. Zavarzina; Ed. G. A. Zavarzina. - M.: Mir, 1999. - 271 p.
- SanPiN 2.1.4.1074–01 Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control. Hygienic requirements for ensuring the safety of hot water supply systems. - M.: Information and Publishing Center of the Russian Ministry of Health. - 2002. http://www.narzanwater.ru/?home=1 Date of access: 09/07/2015.
- Electronic resource: http://l-w.ru/poleznoe_o_vode/o_vode/ Date of access: 09/07/2015.
According to the degree of mineralization, there are 3 categories of drinking water: table drinking water, medicinal table mineral drinking water, medicinal mineral drinking water.
Table drinking water- water with total mineralization up to 1 g/l. This water is recommended for daily consumption. Has no restrictions on use.
In fact, this is all the drinking water that we use every day, including for cooking, tea, coffee, and soft drinks. All bottled waters of 19 l and 5 l are table drinking water. Table drinking water is also produced in volumes of 1.5 l, 0.5 l, 0.33 l and 0.25 l. The container in which table drinking water is produced can be plastic or glass.
Often drinking bottled water with a volume of 1.5 liters or 0.5 liters is called “mineral water”. This is not entirely correct. Indeed, on some labels with table drinking water mineral is written, but in this case this does not mean the degree of mineralization, but the official name of the product according to the TU or SanPin classification.
Table drinking waters include brands such as Arkhyz, Akhsau, Uvinskaya Zhelzhem, Gornaya Verkhina, Salkovskaya, Pilgrimm, Dombay, Shishkin Les, Nestle, Staromytishchinskaya. The products of the famous brands AquaMinerale and BonAqua are also table drinking waters.
Medicinal table drinking water can be consumed as a refreshing drink or used for therapeutic and prophylactic purposes. This water has a consumption limit of no more than 1.5 liters. per day. If this limit is exceeded, excess salts and minerals can be deposited in soft tissues and lead to the development of diseases of varying severity.
Medicinal table mineral waters include most of the mineral water brands we know - Narzan, Borjomi, Essentuki-2, Essentuki-4, Essentuki-7, Novoterskaya Healing, Karmadon, "Jermuk", etc.
Regular consumption of medicinal drinking water will help saturate the body with the necessary non-reproducible minerals and microelements, help cope with disorders of the gastrointestinal tract, improve intestinal motility, and normalize the functioning of the gallbladder, liver, and kidneys.
Medicinal mineral drinking waters. These include waters with a total mineralization of more than 10 g/l. Medicinal waters should be consumed only after consultation with a doctor. As a rule, they are drunk in courses according to the regime, often before drinking they are heated to the desired temperature.
Due to the high degree of mineralization, these waters have a pronounced healing effect. Medicinal mineral waters have strict restrictions on consumption. This restriction is set by the doctor prescribing the course of treatment with mineral waters. You should not drink medicinal mineral waters every day uncontrollably, as this can cause severe stomach and intestinal upset.
Therapeutic mineral waters include such brands as “Uvinskaya Medicinal”, “DonatMg”, “Essentuki-17”, “Novoizhevskaya”, “Semigorodskaya”, etc.
Treatment with medicinal mineral waters is prescribed for obesity, diabetes, hypertension, gout, menopausal disorders, heartburn, respiratory diseases, gastrointestinal diseases, etc.