Tap water. Tap water

Even, it would seem, quite recently, the process of turning tap water into drinking water did not cause much thought among the city dweller. Not everyone considered obligatory even such a simple preparatory procedure as boiling tap water for drinking. And cooking with tap water seemed so natural that there was no thought that it could be somehow different.

Now about 80% of the population is provided with centralized water supply in Ukraine. However, few residents of large and not very large cities consider tap water to be high-quality and safe drinking water, and in any case, the use of tap water as drinking water is not included in the idea of ​​a healthy lifestyle.

Why has the attitude of the consumer to tap water changed? There are several global and specific local reasons, in particular:

• natural waters, which are sources of water supply, have become dirtier; the reserves of clean water on the planet are catastrophically reduced;
• the quality of water treatment at domestic utilities that are in disastrous economic conditions is highly questionable (no matter how we feel about water chlorination, but sometimes chlorine is not enough to disinfect the water supplied to the city water supply);
• consumers learned more about the composition of tap and natural waters, about the presence of pollutants of various nature in them. New, more sensitive and selective methods of analytical control have appeared that make it possible to determine such impurities and at such a level of concentration, which it was not possible to control before;
• both information about home water purification products and the products themselves have become more accessible - household filters, water purifiers, as well as all kinds of improving and cleaning additives;
• the public now knows better how the problem of drinking water is solved abroad.

For the mass domestic consumer, the main source of knowledge about drinking water is, of course, advertising. Household water treatment systems or water purifying additives are distributed primarily through various marketing networks, and each network accompanies its product with persuasive leaflets, booklets, and videotapes. The very principle of network marketing - distribution from hand to hand - gives the perception of advertising information personal shades, and, apparently, increases its significance for the consumer compared to impersonal advertising in the media.

Regardless of the type of product and the level of literacy of the arguments, the general meaning of this kind of information is the same: the good quality of drinking water is the concern of the one who drinks this water. Without disputing this conclusion, let us consider some aspects of water quality from the point of view of a chemist.

World water reserves

The mass of water on the surface of the Earth is 1.39 * 1018 tons, most of it is contained in the seas and oceans. About a sixtieth of the total reserve is made up of glaciers in Antarctica, Antarctica and high mountain regions (2.4 * 1016 tons), about the same amount of groundwater is available, but only a small part of it is fresh. Only one ten thousandth of the total is made up of fresh water available for use in rivers, lakes, swamps and reservoirs - 2 * 1014 tons. Another one hundred thousandth part is in the atmosphere - 1.3 * 1013 tons.

Fresh water resources are unevenly distributed. Nine countries, including Russia, Canada and the US, but excluding Western Europe, account for 60% of the world's fresh water. According to the definition of the United Nations Economic Commission for Europe, a state is considered to be not provided with water, the water resources of which do not exceed 1.5 thousand cubic meters. m per inhabitant. In Ukraine, in dry years, 0.67 thousand cubic meters per inhabitant. m of river flow. It is the river runoff that makes up the bulk of the total water fund. Even taking into account natural reservoirs, reservoirs and groundwater, Ukraine is among the low-income countries in terms of the reserves of water available for use.

What is in natural water?

Water, nature's best solvent, is never completely pure. Water dissolves the solids it comes into contact with - soils, rocks, minerals, salts. Atmospheric gases and gases coming from the depths of the earth, for example, hydrogen sulfide, carbon monoxide, hydrogen, methane, dissolve in water. Natural waters, especially surface waters, also contain significant amounts of organic substances - products of vital activity and decomposition of aquatic organisms. To impurities of natural origin are added substances of anthropogenic origin, the range of which covers almost all classes of inorganic and organic compounds.

The qualitative and quantitative chemical composition of natural waters is very diverse and is determined by physical and geographical conditions. The content of dissolved substances in water is usually expressed in mg / l. Other units are also used in foreign literature:

Ppm (part per million, parts per million) - corresponds to 1 mg / l;
ppb (part per billion, parts per billion) - corresponds to 1 μg / l or 0.001 mg / l;
ppt (part per trillion, parts per trillion) - corresponds to 0.001 µg / l.

1. Dissolved gases - oxygen, nitrogen, carbon dioxide, hydrogen sulfide, methane, etc.
2. The main ions (salt components) are anions of carbonate, bicarbonate, chloride, sulfate; cations of potassium and sodium, magnesium, calcium. In surface waters, their content is expressed in tens and hundreds of mg/l. The combination of these components creates the mineralization of water, measured in g / l. For fresh waters, mineralization is 0.2-0.5 g/l, for slightly mineralized waters - 0.5-1.0 g/l, for brackish waters - 1-3 g/l. Next come the salt waters; waters with mineralization more than 50 g/l are called brines.

   The presence of calcium and magnesium cations gives water a set of properties called water hardness. In our country, water hardness is measured in mmol equiv / l: 1 mmol equiv / l corresponds to 20.04 mg / l of calcium or 12.16 mg / l of magnesium. In other countries, the so-called degrees of hardness are used: German (10 mg of calcium oxide in 1 liter of water, corresponds to 0.357 mmol eq / l); English (1 g of calcium carbonate in 1 gallon, i.e., in 4.546 liters of water, corresponds to 0.285 mmol equiv / l). The “smallest” degree is American, it corresponds to 0.020 mmol equiv / l.

3. Biogenic elements - nitrogen (in the form of ammonia, ammonium, nitrite, nitrate and nitrogen of organic compounds); phosphorus (in the form of phosphates and organic compounds), silicon (in the form of orthosilicates), iron (II and III). These elements are necessary for the nutrition and development of living organisms. However, some of the compounds at high concentrations have a toxic effect, for example, inorganic nitrogen compounds, especially ammonium nitrogen. For fishery waters, the maximum allowable concentration (MPC) of ammonia is 0.08 mg/l, ammonium - 2 mg/l.
4. Trace elements are metals and some non-metals (bromine, iodine, boron), the content of which in waters is within a few tens or less mcg/l. Part of the metals - manganese, zinc, molybdenum and cobalt belong to the so-called biometals that participate in the biochemical processes of living organisms and without which living beings cannot develop. Other microelements, such as cadmium, lead, mercury, chromium, are anthropogenic pollutants and exhibit strong toxicity, which is what they mean when talking about heavy metal pollution. Microconcentrations of radionuclides of strontium, cesium, plutonium are of particular danger to life. However, biometals in excess of MPC also have a toxic effect on living organisms. In addition, the toxicity of trace elements depends on the chemical forms they are in. Organometallic compounds, such as diethylmercury, are most toxic.
5. organic substances. Their content is sometimes characterized by the total content of bound organic carbon. However, such an indicator means little in assessing the degree of pollution of natural waters. Organic substances contained in natural waters should be divided into two groups. The first includes organic compounds of natural origin, mainly humic and fulvic acids, carboxylic and amino acids, carbonyl compounds, esters (carbon bound in them is 1.5-30 mg / l) and some other compounds with a fixed carbon content of 0.2- 12 mg/l. The second group of organic components of natural waters consists of numerous compounds of anthropogenic origin, the content of which depends on the intensity of water pollution and varies over a very wide range, up to several mg/l. These are aromatic hydrocarbons (benzene, toluene, phenols, naphthalene), halogen-containing compounds (chloroform, dichloroethane, dichlorvos), nitrogen-containing compounds (amines, pyridine, polyacrylamide, urea), methanol, benzyl alcohol, oils, petroleum products, dyes, synthetic surfactants substances (surfactants).

The components of natural waters can be in various states of aggregation: in solution in the form of molecules and ions; in the colloidal state - in the form of particles ranging in size from 0.001 microns to 1 microns, invisible during normal observation; in the form of suspensions - larger particles that give water turbidity. A significant proportion of microelements is found in colloidal and suspended particles. Microparticles also include various microorganisms.

Like all environmental objects, natural water is polluted in the process of human economic activity. On December 18, 1962, at the 27th session of the UN General Assembly, the resolution “Economic Development and Nature Protection” was adopted, which marked the beginning of the environmental movement. Estimates made at the time indicated that the planet's clean water and clean air supplies would last three decades. They have already passed, and an analysis of the state of water sources leads to a disappointing conclusion that this forecast was justified.

It is customary to divide water from water supply sources into categories depending on the degree of pollution - from clean water (quality class I) to polluted (class IV) and dirty (class V). In the 1950s and 1960s, when the currently used water purification technologies were being developed, surface sources were classified as quality class I.

Now, out of 50 water bodies in Ukraine, where hydrobiological and chemical studies were carried out, there was not a single one that corresponds to the concept of “clean water”.

Despite the decline in production, which led to some reduction in industrial wastewater, in the basins of the Danube, the Dniester, the Western and Southern Bug and the Seversky Donets, an increased content of nitrogen compounds, phenols, oil products, and heavy metals is observed. The water of these sources is classified as polluted and dirty (IV and V quality classes).

The state of small rivers and natural reservoirs is assessed as catastrophic; groundwater quality is constantly deteriorating. And the technology of water treatment and water purification has remained practically unchanged.

Xenobiotics and supertoxicants. Environmental pollution is the other side of progress in the field of chemical synthesis. Now the number of chemical compounds created by man reaches 7 million. About 70 thousand chemical products are used in daily practical activities, and their range is expanding by 500-1000 units per year.

Substances of anthropogenic origin are distinguished by the fact that in relation to them the human body (and not only humans) does not have the genetic memory of expedient counteraction. These are substances alien to living nature - xenobiotics, for them in living organisms nature does not provide for ways of processing and excretion. Therefore, xenobiotics tend to accumulate in organisms and distort natural biochemical processes.

The impact of pollutants on the body can be actually toxic and organoleptic. The latter are manifested in the form of an unpleasant odor or taste. Toxic effects can be general environmental, carcinogenic, mutagenic, cause occupational or specific diseases.

Among the many pollutants, supertoxicants stand out - substances that, even in minimal amounts, have a direct or indirect effect on human health. The World Health Organization (WHO) has defined a list of such supertoxicants. This includes, first of all, those substances that were synthesized and produced precisely as poisonous - insecticides, pesticides, zoocides, etc. Another group consists of substances formed as by-products in various processes - fuel combustion, decomposition or synthesis of organic substances, operation of automobile engines, etc. Of particular danger are:

• aromatic hydrocarbons (AH) - substances containing a benzene ring;
• polyaromatic hydrocarbons (PAH) - substances containing condensed benzene rings:

Benzene

• polychlorinated biphenyls (PCDF).

What happens to water during water treatment?

Before water is supplied to centralized water supply systems, it is preliminarily brought to the condition stipulated by regulatory documents. In water treatment, special chemicals are added to the water.

1. Clarification is the removal of coarse and colloidal impurities that cause color and turbidity of water. To do this, coagulants (aluminum or iron sulfates, ferric chloride) and flocculants (polyacrylamide, finely dispersed silicic acid, etc.) are added to the water and the falling flakes are separated.
2. Water disinfection is necessary to kill pathogens and viruses, as well as certain types of microorganisms (eg, filamentous, zoogley, sulfate-reducing bacteria, iron bacteria) that cause biological fouling and corrosion of pipelines. Water chlorination is the most common. Other methods of disinfection are the use of ozone or ultraviolet radiation.
3. Stabilization. Stable water is water that does not release or dissolve scale, which consists mainly of calcium carbonate. Scale-dissolving water causes corrosion of steel and other metals. To stabilize such water, it is treated with alkaline reagents: slaked lime, soda ash. Water prone to scaling is stabilized by the addition of acids, polyphosphates, and treated with carbon dioxide.
4. Water softening is the removal of hardness salts formed by calcium and magnesium cations. In reagent softening, the slaked lime and soda ash mentioned above are used. Another method of softening is associated with passing water through a layer of granular cation exchanger, while calcium and magnesium cations are absorbed by the cation exchanger, exchanging for sodium, hydrogen or ammonium ions.

Some types of water require additional operations - iron removal, desiliconization, also associated with the use of chemical reagents.

Some of the reagents used for water treatment (soda, lime, iron compounds) consist of components that were also present in the source water. But in general, it is obvious that at water treatment plants, the qualitative composition of water is replenished with new chemical components. Here are the impurities contained in the reagents, and what was formed in the side reactions that accompany water treatment.

Many of the by-products of chlorination and ozonation are included in the WHO list of priority toxicants. Toxicological studies have shown that they are carcinogenic and/or adversely affect the reproduction or development of laboratory animals.

Regulation of water quality, or what kind of water is called drinking?

Providing the population with high-quality and safe drinking water is a matter of national importance. On January 10, 2002, the Verkhovna Rada of Ukraine adopted the Law "On Drinking Water and Drinking Water Supply". It applies to all drinking water suppliers that provide settlements and individual facilities with drinking water through centralized water supply or through water bottling points, including mobile ones (remember tank trucks?).

According to the Law, drinking water is water that, in terms of organoleptic properties, chemical and microbiological composition and radiological indicators, meets state standards and sanitary legislation. In Ukraine, the state standard that existed in the USSR (GOST) 2874-82 “Drinking water. Hygienic requirements and quality control”. The standard normalizes microbiological, toxicological and organoleptic indicators of drinking water at a safe level. The indicators of the last two groups relate to the chemical composition and include standards for substances:

• found in natural waters;
• added to water during processing in the form of reagents;
• appearing as a result of industrial, domestic, agricultural pollution of water supply sources.

The harmlessness of the chemical composition of water is characterized by toxicological indicators. Limits of a number of toxicants in drinking water (mg/l) have been established, for example:

The concentrations of substances that affect the organoleptic properties of water are also normalized, for example, according to GOST 2874-82, they should not exceed the following standards:

Dry residue, characterizing the presence of mineral salts and non-volatile substances in water, should not exceed 1 g/l; therefore, drinking water that meets the standards can be classified as low-mineralized.

The organoleptic properties of water are expressed by indicators of smell, taste, color and turbidity, which are also normalized by GOST.

How do these standards relate to the actual quality and safety of tap water? Three types of situations can be distinguished here.

Situation 1. The water supplied by Vodokanals does not meet the standards. According to the chief state sanitary doctor of the Russian Federation G. G. Onishchenko ("Ecology and Life", 1999, 4), in Russia as a whole, 20.6% of samples taken from the water supply system do not meet the hygienic requirements for drinking water in terms of sanitary and chemical indicators and 10.6% - on microbiological. In Ukraine in 2000, in samples taken from the water supply, the deviation of the composition of water from the current standards was on average about 12%. At the same time, in some regions, for example, Lugansk, only 10% of drinking water sources meet the standards.

Situation 2. The water supplied to the centralized water supply systems complies with the standards, but the water that has reached the consumer does not. Water pipes are an additional source of pollution. Most often, the poor quality of tap water is associated with an increased content of iron and manganese in it. The concentration of iron increases due to corrosion of steel and cast iron water pipes. Corrosion is promoted by soft water. According to the regional bodies of the Sanitary and Epidemiological Service of Russia, about 50 million people, that is, a third of the country's population, drink water with a high iron content.

During operation, water pipes are covered inside with plaque, sediment, consisting mainly of mineral salts. This sediment serves as a kind of "accumulator" of all kinds of impurities: it absorbs them when contaminated water flows through the pipes, and releases them when cleaner water is supplied to the pipes. Those who had to be present at the replacement of water pipes could see a slimy layer similar to silt on the surface of such sediment. It contains microorganisms - algae, bacteria, viruses that multiply in the closed space of water pipes. The presence of some of them in tap water, as well as the pathogenic effect of others, has become known relatively recently. The US Environmental Protection Agency, increasing the requirements for the safety of drinking water, intends to supplement the new standards with rules for the control of 36 pollutants, divided into three lists. List 3 are contaminants recently identified in drinking water: algae and toxins; echoviruses; Coxsackieviruses; Helicobacter pylori; microsporidia; Caliciviruses; adenoviruses. Of course, it is advisable to control them not at the water treatment plant, but at the place of consumption. Analytical methods for them are still at an early stage of development.

Situation 3. Both the tap water supplied by Vodokanal and the tap water that reaches the consumer complies with GOST standards. Does this mean that it is really pure enough to drink and harmless to health? The current GOST provides for the control of 10 toxicological and 9 organoleptic indicators, but among the normalized indicators of toxicity, the content of only one organic substance is mentioned - residual polyacrylamide, used to clarify water during water treatment. GOST does not provide for the definition of other organic substances related to toxicants and supertoxicants. Even the control of by-products of water chlorination is not provided. But for drinking water, MPCs for oil products, surfactants, phenols, 6 aliphatic and 23 cyclic hydrocarbons (this class includes the supertoxicant benz (a) pyrene), 78 halogen-containing compounds and MPCs for more than six hundred different organic substances.

A "transitional period" from 2000 to 2005 has been allocated for the introduction of the new standard. State control over water quality is entrusted to the laboratories of the Sanitary and Epidemiological Service. However, neither they nor Vodokanals currently have the material base to work in accordance with SanPiN, and its formation in the current economic conditions is very problematic. The fact is that water analysis according to the GOST 2874-82 standards was carried out using the most affordable devices - photocolorimeters, pH meters, or chemical methods that do not require special equipment at all. Organic pollutants are either impossible or very difficult to determine by these methods. For modern control of water composition, more sensitive and selective methods of analysis are needed, which distinguish substances of a similar structure, but of different toxicity and allow determining low and very low concentrations of pollutants - at the MPC level. One method that satisfies these requirements is chromatography. Unfortunately, both the chromatographic instruments themselves and their maintenance during operation are very expensive.

Only when funds are found in Ukraine to equip all laboratories that perform the current mass water analysis with such equipment, more objective information will appear about what flows from the water tap. This information is needed not only by the consumer; any projects in the field of ecology, improvement of water resources, modernization of water supply enterprises should be based on reliable data on the chemical composition of water.

What kind of water do they drink in Western Europe and North America?

In Western Europe and North America, a different culture of drinking water consumption has developed.

Residents of Western Europe were the first to replace tap water with bottles of natural water, the first to use home water purification systems on a massive scale.

Then these products appeared in the USA, about ten years ago - in Russia and Ukraine.

According to foreign data, in Europe the consumption of bottled water is 100 liters per person per year, in the USA - 43 liters, in Canada - 20 liters, in Russia it is still less than 1 liter, but the consumption growth rate is one of the highest in the world.

Why Western Europe was the first to stop counting drinking tap water? In densely populated Western Europe, fresh water supplies are limited (as in Ukraine). Here, rivers and lakes, earlier and stronger than in North America, experienced the consequences of intensive economic activity and lost their purity. The high pollution of surface waters in Europe compared to North America is illustrated by data on the content of carbon tetrachloride in the waters of these regions, one of the priority pollutants (it is used as a solvent in the chemical industry and for dry cleaning):

In Europe (Germany, 1976), the highest level of one-time pollution of river water with carbon tetrachloride was also registered: from 160 to 1500 mg/l in the Rhine River, an average of 75 mg/l in the Main River.

The inhabitants of Western Europe were the first to feel and realize that the supply of water is limited, and the more water is used, the more difficult and expensive it is to process it. It is wiser to bottle water from clean sources than to supply it to the mains.

In the US, tap water is considered drinking water. Its quality is protected by the federal law "On the safety of drinking water", the 25th anniversary of which was widely celebrated in the United States in 1999. The President, legislators, public organizations recognized the effectiveness of the law, its positive impact on the health of the nation. According to this law, city authorities are required to bring to the attention of the public information about the quality of water from centralized water supply, for example, by posting it on the Internet on the municipal website. For example, fans of the television series Santa Barbara can go to www.ci.santa-barbara.ca.us and find out about the quality of water supplied to the homes of their favorite TV characters. The information reports on the state of the city's drinking water sources and the content of substances controlled at the water treatment plant, in the distribution system and in the consumer water supply system. In the distribution system, mainly by-products of water chlorination are controlled.

In the US, bottled water (mostly imported from Europe) is also quickly becoming popular as a mainstream alternative drink, much like soft drinks or iced tea. But here, a water bottle does not replace running water, but rather a convenient form of transportation: most of the bottled water is consumed in cars. Municipal information reassures the public that tap water is completely safe to drink and does not need to be replaced with bottled water. What's more, about 25% of bottled water sold in the US is municipal tap water, sometimes filtered, sometimes not.

In 2001, the magazine "Drinking Water" began to appear in Russia. The editors of the magazine, discussing the availability of information on the quality of tap water in the United States, expressed their readiness to place on their pages information from Vodokanals on the quality of supplied water. The editors also recommend posting such information on the Internet, for example, on the corporate website of Vodokanals, which was created in St. Petersburg - http://www.waterandecology.ru/vodokanal. So far, this call has not been heeded. On the site, among others, there is also one Ukrainian Vodokanal - Lutsk.

Features of post-treatment of tap water

For additional purification, water is passed through filters, distilled to obtain distilled water, or treated with sorbents (solids that absorb dissolved impurities).

What should be remembered when using such water for drinking?

Distilled water may contain organochlorines, by-products of water chlorination. They are volatile and are distilled off during distillation and then condense together with water vapor. The content of volatile chloroorganic substances in distilled water (as well as in tap water) decreases when boiled or settled. Distilled water contains a noticeable amount of copper compounds, because the internal parts of distillation units are usually brass.

Cleaning on filters is effective until the filter has exhausted its resource, in other words, it has not become clogged. Here, the consumer has to rely on the indications of the resource of the filter manufacturers, as well as on the fact that the water being treated is not dirtier than the one for which this resource was installed. It is known that the resource of the filter can vary by dozens of times depending on the composition of the treated water; In addition, different manufacturers have different ways of evaluating the resource, which makes it difficult to compare different water treatment devices in terms of efficiency.

When using natural sorbents, such as clays, the question arises of the chemical and bacteriological purity of the sorbent itself.

In all cases, post-treated water contains less dissolved substances. Along with pollutants, substances of natural origin, in particular, useful minerals and trace elements, are also removed from the water. Therefore, part of Western European, and now domestic consumers consider the main disadvantage of treated water to be that with its regular use, the body receives less valuable nutrients. However, drinking water has never been and is not the main source of minerals or trace elements necessary for the body. Perhaps the largest contribution of drinking water to providing the body with fluorine is up to half of the daily requirement. The need for other elements or trace elements is provided mainly, of course, by food; water for this would require drinking too much. This is shown by the following data:

Brief summary

There are good reasons to believe that the quality of domestic tap water has deteriorated over the past 30-40 years. The pollution of water supply sources has significantly increased, the range of toxic pollutants has increased, and the technologies of centralized water treatment have remained practically the same, designed for clean water sources. Worn pipes further pollute tap water. Operational, available to the average consumer information about the quality of the supplied water could convince the safety of drinking tap water. But water suppliers themselves do not have complete information that would correspond to the world experience in drinking water quality control.

Perhaps, in the coming years, we should not expect significant changes either in the quality of domestic water treatment, or in the awareness of the population about the quality and safety of tap water. The choice of alternative methods of water consumption remains with the consumer.

Literature

1. Chemical encyclopedia: In 5 volumes - M .: Sov. Encycl., 1988. - T. 1 - 623 s;. – M.: Sov. Encycl., 1990. - T. 2. - 671 p.;
2. Pitna water. Normative documents: Dovіdnik: U 2 vol. - Lviv: STC "Leonorm-format", 2001. - Vol.1. - 260 p.; T.2. – 234 p.
3. Control of chemical and biological parameters of the environment. St. Petersburg, Soyuz Ecological and Analytical Information Center, 1998. - 896 p.
4. Analytical chemistry of the natural medium / B. Y. Nabivanets, V. V. Sukhan, L. V. Kalabina et al. - K .: Libid, 1996. - 304 p.
5. WHO Carbon Tetrachloride. Environmental Health Criteria No. 208. World Health

L. P. Loginova. All-Ukrainian popular science magazine “UNIVERSITATS. Science and education»

One of the most important problems today has become the problem of clean water. Scientific progress has generated another problem - environmental pollution. Not everyone dares to drink tap water. Of course, this may not end in anything bad, but no one wants to risk their health. Why is tap water dangerous? What is she?

With an increased content of manganese in tap water, anemia may develop, the functional state of the central nervous system may be disturbed. Some doctors have an opinion that an increased content of manganese has a mutagenic effect on a person; during pregnancy, the risk of pathogenic childbirth and stillbirth increases.

If the content of salts of sulfuric and hydrochloric acids (chlorides and sulfates) is increased in water, then the taste of water becomes unpleasantly salty or bitter-salty. With the use of such water, disturbances in the work of the gastrointestinal tract may occur. Water is considered unfavorable for health, the content of chlorides per 1 liter in which is more than 350 mg, and sulfates - more than 500 mg.

If the water contains calcium and magnesium cations, then it becomes hard. The optimal level of hardness is considered to be 3.0–3.5 mg eq / l (= mol / cubic meter). With the constant use of water, in which hardness is increased, salts accumulate in the body, which ultimately leads to the development of joint diseases (arthritis, polyarthritis), the formation of stones in the kidneys, urinary and gall bladders.

When drinking tap water with a high fluorine content, tooth enamel becomes mottled, calcium excretion in the urine increases, phosphorus and calcium content in the bones decreases, immune reactivity is suppressed, and morphofunctional changes occur in the liver and kidneys. But the low content of fluorine in water is also not good, since the condition of a person’s teeth depends on the water. For example, the incidence of caries directly depends on how much fluorine is contained in the water. In order for water not to cause harm, fluorine in it should be contained in the range of 0.7 - 1.5 mg / l.

If there are sulfides (hydrogen sulfide) in the water, an unpleasant odor appears in the water and such water causes skin irritation. Arsenic causes disorders of the central and peripheral nervous systems, which then contribute to the development of polyneuritis. Harmless concentration of arsenic is 0.05 mg/l.

With prolonged intake of strontium in the human body in large quantities (more than 7 mg / l), functional changes in the liver may appear.

The cause of senile dementia, neurological changes associated with Parkinson's disease, increased excitability may be the accumulation of aluminum in the body. In a child's body, aluminum causes disturbances in motor reactions, anemia, kidney disease, headaches, liver, colitis.

These types of pollution are chemical. But there are also organic water pollution, which include bacteria that cause various diseases.

Organic contamination of tap water

For example, diseases such as dysentery, typhoid fever, poliomyelitis, and water fever can be transmitted through contaminated water. Yes, and an elementary indigestion is not the most pleasant thing. Bacteria are killed when water is boiled.

For many years, chlorine was used to disinfect water, which was considered the most effective means. But they not only destroy bacteria, but it also enters into chemical reactions with other substances, while the formation of compounds that are no less dangerous to health occurs. It is these organochlorine compounds (formed, in particular, by boiling chlorinated water) that can develop chronic nephritis and hepatitis, toxicosis during pregnancy, and diathesis in children. Moreover, chlorine, as a more active element, displaces iodine from the body, thereby weakening the functional state of the thyroid gland. If water, in addition to chlorine, also contains phenol, then these two elements form chlorophenolic compounds, which are especially toxic and hazardous to health.

It is not enough just to purify water from harmful impurities, it must also be properly directed to homes. Each of us has noticed that sometimes, when opening a water tap, we find a brown stream. The bottom line is that water contains a huge amount of iron, more familiar as rust. It's all about the dilapidated and rotten pipes through which water enters the houses. Most of them have long been in need of replacement, but everything again rests on financial nuances. Therefore, post-treatment of tap water is of great importance, i.e. bringing it to a level corresponding to the level of drinking quality. Physical and chemical contaminants may be present in the water, but in lower concentrations than initially at the wastewater treatment plant. The issue of disinfection of tap water is also relevant, because. chlorination still does not kill all harmful microbes.

If you drink tap water, you should know that it contains organochlorine compounds, the amount of which after the procedure for disinfecting water with chlorine reaches 300 μg / l. Moreover, this amount does not depend on the initial level of water pollution, these 300 substances are formed in water due to chlorination. Of course, there will be no quick consequences from the consumption of such drinking water, but in the future it can very seriously affect health. The fact is that when organic substances are combined with chlorine, trihalomethanes are formed. These methane derivatives have a pronounced carcinogenic effect, which contributes to the formation of cancer cells.

Much has already been said about the unusually harmful properties of chlorine, including the direct impact on the development of cancer, but its amount in drinking water has not decreased. And all because it is not economically feasible to disinfect water without chlorine, since alternative methods of water disinfection (ozonation, the use of ultraviolet light) are expensive.

When boiling chlorinated water, it produces the strongest poison - dioxin. The content of trihalomethanes in water can be reduced by reducing the amount of chlorine used or by replacing it with other disinfectants, for example, using granular activated carbon to remove organic compounds formed during water purification. And, of course, we need more detailed control over the quality of drinking water.

How is water purified in the country?

Not all regions treat water in the same way, as water contains different chemicals in different areas. Depending on the degree of pollution of the water body and the purpose of water, additional requirements are imposed on its quality. However, there is a set of typical procedures used in water treatment systems and the sequence in which these procedures are used. In the practice of water supply of settlements with water of drinking quality, the most common water purification processes are clarification and disinfection.

Lightening

Clarification is a stage of water purification, during which the turbidity of water is eliminated by reducing the content of suspended impurities in it. The turbidity of natural water, especially surface sources during the flood period, can reach 2000-2500 mg/l (at the norm for drinking water - no more than 1500 mg/l).

Impurities suspended in water have a different degree of dispersion - from coarse, quickly settling particles, to the smallest, forming colloidal systems.

Finely dispersed colloidal particles, having the same electrical charge, repel each other and, as a result, cannot grow larger and precipitate.

One of the most widely used methods in practice to reduce the content of finely dispersed impurities in water is their coagulation (precipitation in the form of special complexes - coagulants) followed by precipitation and filtration. After clarification, the water enters the clean water tanks.

Disinfection

To date, the most popular method of water disinfection in our country is chlorination, because. in the rivers and lakes where water is taken from, there are many microorganisms that got there with sewage, and chlorine is a powerful oxidizing agent that can destroy pathogens.

How much has already been said about extremely harmful properties of chlorine, including direct impact on development oncological diseases, however, its quantity in drinking water has not decreased. And all because it is not economically feasible to disinfect water without chlorine, since alternative methods of water disinfection (ozonation, the use of ultraviolet light) are expensive.

Water can contain many different substances, and chlorine reacts with some of them. As a result, much more unpleasant compounds are formed than chlorine itself. For example, chlorine compounds with phenol; they give the water an unpleasant odor, affect the liver and kidneys, but in small concentrations are not very dangerous. However, compounds of chlorine with benzene, toluene, gasoline are possible, with the formation of dioxin, chloroform, chlorotoluene and other carcinogens.

For reference, in order for chlorine to completely evaporate from the water, it is necessary to defend the water for 7 days.

“The most annoying thing is that no matter how much chlorine you throw in, it still won’t kill all harmful microbes,” says Nailya Davletova, specialist of the Department of Occupational Hygiene and Medicine with a course in medical ecology at KSMU. - But this element has a powerful toxic, local irritant and allergic effect on a person. Ideally, it is necessary to clean the water with a natural and safe agent - ozone. It is a gas with a pungent aroma, similar to the smell of fresh air after a thunderstorm. Purification of tap water with ozone is currently practiced in many civilized countries of the world, including Germany, Italy, Canada and the USA. There, ozone units have long been part of community water treatment systems, and they are also used by bottled water companies. In Russia, they prefer not to spend money on such expensive water treatment, sacrificing people's health.

You can also destroy bacteria living in water using ultraviolet radiation. To get rid of most harmful microorganisms, just a few seconds are enough. And with exceptionally low operating costs, ultraviolet can process thousands, tens and hundreds of thousands of liters of water. By the way, since 2007, thanks to this safe method of cleaning, residents of St. Petersburg have been enjoying, unlike other Russians, high-quality drinking water. But even here you should not relax. As soon as the water enters the old, almost 80-90% worn-out water supply network, big adventures await the water here. Through old, sometimes rotten pipes, harmful substances, bacteria and viruses can enter the water. It is enough to remember when accidents occur or when water pipes are replaced - tap water smoothly changes from dark brown or black to transparent within an hour. And no one knows what got into the pipes during their welding.

And if the water is clean and clear in appearance? Is this a guarantee that it does not contain harmful impurities? Unfortunately no.

Mineralization of water or optimal salt composition.

Imagine that we received sterile water. In such water there are no harmful substances and microorganisms. Is such water complete for our consumption? It turns out not.

Indeed, with water, the body must receive a whole complex of minerals, without which a person risks facing many troubles. Drinking water should contain not only fluorine and iodine, but also calcium, magnesium, iron, copper, zinc.

For example, here are the symptoms that may be the cause of a lack of minerals:

• Magnesium: Intermittent heartbeat, craving for chocolate, cramps, PMS, periodontitis, high blood pressure, etc.
• Iron: anemia, fatigue, etc.
• Copper: anemia, thyroid dysfunction, poor digestion, enzymatic function of the liver, since most of the enzymes in it are copper-dependent, rapid occurrence of hematomas, etc.
• Zinc: Anorexia, loss of sense of taste and smell, low libido, PMS, height reduction, acne and other skin disorders, etc.
• Iodine: thyroid dysfunction, bile thickening, etc.

But that's not all.

Mineralization of water (the amount of salts dissolved in water) is an ambiguous parameter.

Studies conducted in recent years have shown an adverse effect on the human body of drinking water with a mineralization of more than 1500 mg/l and below 30-50 mg/l. Such drinking water does not quench thirst well, impairs the functioning of the stomach, and disrupts the water-salt metabolism in the body. Until recently, the high mineralization of water - hardness - was paid attention only because of its effect on the suitability of water for washing hair and laundry, as well as on the intensity of scale formation when water is boiled.

Now, thanks to the scientific data obtained, it has become clear that water purification is necessary, because the hardness of drinking water is of great importance for maintaining health. For example, an increased content of calcium and magnesium salts in water contributes to the development of atherosclerosis, urolithiasis, and causes metabolic disorders. On the other hand, mortality from cardiovascular diseases is 25-30% higher among people who drink soft water containing less than 75 milligrams of calcium and magic per liter of water.

By the way - there are no harmful substances, there are harmful amounts.

Water from artesian wells and springs

There is a widespread opinion regarding the healing properties of water from the bowels of the earth. How does it differ from water from the mineral springs of the North Caucasus. It turns out that it differs, and very significantly. First, the depth of the well. Artesian wells are drilled to pressure waters, for example, in the Moscow region located in coal limestones. The depth of such wells can be different: in the north of Moscow, where the glacier left powerful deposits, in the area of ​​​​the Klin-Dmitrovskaya ridge, their depth reaches 200 - 250 m. To the south of Moscow, in some places, limestone comes to the surface, here artesian wells are the smallest , 30 - 40 m. To the west and east of Moscow, the depth of artesian wells ranges from 60 to 150 m. But in the Moscow region, as well as near other large cities, aquifers with a depth of less than 100 m can no longer be considered bacteriologically safe. However, during the drilling of wells, some technological processes may be disrupted, the produced water may turn out to be too hard, tasteless, and leave a strong scale when boiled.

In a cottage or in a summer cottage, located in a beautiful area, devoid of any signs of pollution, water can flow from the ground, completely unsuitable for drinking and even life-threatening, in which the concentration of iron, magnesium, fluorine salts exceeds the permissible values ​​​​tens of times . Moreover, the concentration of salts in water tends to increase with long-term use of the aquifer. Underground drinking water often has an unpleasant feature - it darkens in the process of contact with air. This oxidizes the free iron dissolved in water. Clear, clean water, standing in a jug for 10-15 minutes, becomes brown.

In order to somehow help their body, many residents travel outside the city, collecting water from roadside springs. But even here you need to be careful: few people know what unverified spring streams carry in themselves. First of all, chemicals and pesticides seeped through the soil from the fields can get here, which is especially dangerous.

Underground sources are considered the cleanest and most suitable for drinking. Voditsa there needs more gentle cleaning, but it also requires a competent approach and adherence to technologies in their development and use.

The composition of drinking water, which brings the body, has a fairly strict limits on the content of minerals and salts. A person can benefit from drinking water, the boundaries of mineralization of which lie in the range from 0.02 to 2 grams of minerals per liter.

Sulfates, bicarbonates, magnesium, sodium and calcium chlorides are the main salts that saturate water and are required by a person for life. The amount of these salts should not exceed 0.5 grams per liter of water.

Also useful and necessary for us water should contain such microelements as fluorine, bromine, iodine. The content of these trace elements in water is negligible and is measured in milligrams, but nevertheless it is very important for the normal functioning of many physiological functions of the body. At the same time, the dosage is very important, since it seriously affects certain processes of the formation of certain tissues and cells. The dosage of fluorine in water is very indicative. If fluorine is less than 0.5 milligrams per liter, tooth decay inevitably occurs. At the same time, the concentration of fluorine exceeding 1.0-1.5 milligrams will also inevitably lead to another dental disease - fluorosis (The disease was first described as early as the 18th century as "mottled teeth"). It can develop both before and after teething. Causes destruction of tooth enamel.

Water in which there are no salts and microelements is as harmful as it is tasteless. It is unpleasant to drink it, it is harmful in that it lowers the osmotic pressure inside the cells. This water is distilled water. Drinking this water is not recommended. Salt concentrations less than 100 milligrams per liter are considered unacceptable for drinking.

Elements such as sodium, calcium and potassium are distributed differently in our body, the presence of which in water is also necessary. Intracellular fluids of blood plasma, digestive juices, eye moisture, cerebrospinal fluid require sodium ions. Intracellular fluids of cells of muscles, nerves, skin, and other organs - calcium and potassium ions. Again, dosage matters a lot.

Natural water contains not only these elements. Their huge variety. Almost all the chemical elements of the earth in one concentration or another are found in real natural water. The difference is only in quantity. Therefore, it is so important from which source you drink water.

Of course, we do not always have the opportunity to study the composition of the water that we have to drink. But nature has endowed us with taste buds and this is an important way to quickly analyze, giving us the opportunity to understand whether we need to drink this or that water. Academician I. P. Pavlov said that in the course of evolution a person developed a reflex of aversion to water that is unpleasant or unusual in taste. So, even if it is not possible to read the composition of the water on the bottle label, taste the water and if you don’t like something in it, don’t drink it. Good water always tastes good, you want to drink it. Only such water can satisfy the needs of our body, benefit and not harm.