Manganese is usually attributed to the group of heavy metals, this substance is not as widespread as iron, but is quite common, and in its properties resembles iron itself. As a result of the increased content of manganese in water, deposits of this metal begin to accumulate on the internal surfaces of water pipes and water heating equipment, which, in turn, can cause blockage and deterioration of heat transfer processes, so you should think about quality. In addition, such water leaves indelible marks on plumbing fixtures. It is also worth noting that this is not all the harm that a liquid with a high concentration of manganese can bring, since manganese in drinking water is one of the main reasons for its unpleasant taste, in addition, the use of such a liquid for quenching thirst and cooking negatively affects the state of the human body. Recent studies have shown that drinking water that is excessively enriched with manganese leads to a decrease in intellectual abilities in children. The constant use of drinking water, in which the concentration of manganese exceeds 0.1 mg / l, can provoke the occurrence of serious diseases of the skeletal system.

BWT solutions for water iron removal:

It should be noted that today the problem of high manganese content in drinking and tap water is almost as acute as the problem of water with high iron concentration. For this reason, in many modern states, including Russian Federation, is one of the main tasks of water treatment. Despite this, many people install additional filter systems in their homes and apartments in order to obtain the optimal composition of the liquid, which is so necessary for all living organisms for a normal existence.

If the permissible concentration of manganese is exceeded in tap or drinking water, the liquid acquires a yellowish tint and has an unpleasant astringent taste. Drinking such water is not only unpleasant because of the bad taste, but also dangerous to health. Yes, higher content manganese in drinking water threatens with diseases of the liver, in which this metal is mainly concentrated. In addition, manganese, consumed with water, has the ability to penetrate the small intestine, bones, kidneys, endocrine glands, and even affect the brain. It is important to know that as a result of the constant use of drinking water, in which the content of this chemical element is exceeded, chronic poisoning with this metal hazardous to health may begin. The poisoning is either neurological or pulmonary. In the case of a neurological form of poisoning, the patient may experience the following symptoms:

• Complete indifference to the events taking place around;
• Drowsiness;
• Loss of appetite;
• dizziness;
• Severe headaches.

If the poisoning was extremely strong, loss of coordination of movements, convulsions, back pain, and a sharp change in mood are not ruled out. People poisoned by manganese may suddenly burst into tears or, on the contrary, burst out laughing. To all of the above, an increased tone of the facial muscles is added, which causes a change in the expression of the patient's face. So that manganese in drinking water extremely hazardous to the health of the human body.

All of the above allows, without a shadow of a doubt, to declare the need to purify drinking and ordinary tap water if the concentration of manganese exceeds the permissible limits, or rather 0.1 mg / l. Moreover, in some countries, the maximum concentration of manganese does not exceed 0.05 mg / l - this substance is considered so dangerous. In general, all currently existing methods and purification of water from manganese are reduced to the following principle. Initially, bivalent manganese is oxidized (it is in this form that it enters plumbing communication systems from natural sources) to tri- and tetravalent manganese. Oxidized tetravalent manganese, as a result of reaction with a certain substance, forms an insoluble precipitate, which is removed by means of mechanical filters. Oxides, hydroxides or salts of acids can act as an insoluble precipitate; the type of precipitate primarily depends on the type of reagent used and the method chosen.

In well water. As a rule, it is found in iron-containing water, the source of which is reservoirs, river, sea, groundwater.

How does manganese get into water?

Natural manganese enters surface waters in the process of leaching of minerals, including manganese (manganites, pyrolusites, and others), as well as as a result of the decomposition of plants and aquatic organisms. Manganese compounds enter water bodies with wastewater from chemical industry enterprises and metallurgical plants. The content of manganese in river waters ranges from 1-160 mcg/dm3, in sea waters - up to 2 mcg/dm3, in groundwater - from hundreds to thousands of mcg/dm3.

In natural waters, manganese migration occurs in various forms: complex compounds with sulfates and bicarbonates, colloidal, ionic - in surface waters there is a transition to high-valent oxides, precipitated, complex compounds with organic substances ( organic acids, amines, humic substances and amino acids), sorbed compounds - manganese-containing suspensions of minerals washed out by waters.

The balance and forms of manganese content in water are determined by temperature, oxygen content, pH, absorption, release by aquatic organisms and underground runoff.

For manganese, seasonal fluctuations in concentration are characteristic. There are many factors affecting the level of free manganese in solution - the presence of photosynthetic organisms, the connection of lakes and rivers with reservoirs, the decomposition of biomass (dead plants and organisms), aerobic conditions.

Why is manganese dangerous?

Elevated concentrations of manganese in water are indicated by black spots and stains on household appliances and plumbing. Manganese is an extremely toxic element that has a detrimental effect on the nervous and circulatory systems. Excess metal can penetrate into the kidneys, endocrine glands, small intestine, bones, brain and provoke disruption of the endocrine system, pancreas, as well as increase the risk of developing cancer and Parkinson's disease. The clinical manifestation of chronic manganese poisoning can have pulmonary and neurological forms.

When exposed to nervous system There are three stages of the disease:

1. The first stage is characterized by the predominance of functional disorders of the nervous system, expressed in increased fatigue, drowsiness, the presence of paresthesia and a gradual decrease in strength in the limbs, symptoms of autonomic dystonia, increased salivation and sweating. During an objective examination, muscle hypotension, mild hypomimia (weakening of expressive movements of the facial muscles), revitalization of tendon reflexes, peripheral autonomic disorders, and distal hypesthesia can be detected. Changes in mental activity are considered typical for this stage of intoxication: a narrowing of the range of interests, a decrease in activity, a paucity of complaints, a weakening of associative processes, a decrease in memory and criticism of the disease. Following changes in the psyche, as a rule, focal neurological symptoms of intoxication are observed, but in view of the decrease in patients' criticism of their own condition, such changes are often not diagnosed in a timely manner. With continued contact with elevated concentrations of manganese, signs of intoxication may increase, and the process runs the risk of becoming an irreversible organic character.
2. The second stage is characterized by an increase in the symptoms of toxic encephalopathy, such as a mnestic-intellectual defect, severe asthenic syndrome, drowsiness, apathy, neurological signs of extrapyramidal insufficiency: bradykinesia, hypomia, muscular dystonia with an increase in the tone of individual muscle groups, pro- and retropulsion. The signs of polyneuritis, weakness, paresthesia of the extremities are aggravated. There is also inhibition of the function of the adrenal glands, gonads and other endocrine glands. Even the termination of contact with manganese does not stop the development of this process, which progresses for several more years. At this stage, full recovery of health in most cases is not observed.
3. For the third stage of intoxication, the so-called manganese parkinsonism, gross disorders of the motor sphere are indicative: dysarthria, masking of the face, monotonous speech, impaired writing, significant hypokinesia, spastic-paretic gait, gross pro- and retropulsions, paresis of the feet. There is an increase in muscle tone according to the extrapyramidal type, in the vast majority of cases in the legs. Sometimes there is hypotension or muscle dystonia, a polyneuritic type of hypesthesia. Also, various mental disorders are characteristic: patients are complacent, euphoric or apathetic. Reduced or absent criticism of one's own illness, violent emotions (laughter or crying) may occur. The mnemonic-intellectual defect is expressed to a large extent (difficulty in determining the time, forgetfulness, deterioration of social, including professional, activity).

In view of the possibility of such severe consequences, it is important to timely detect the presence of an excess of manganese in the water that a person eats and uses for water procedures, brushing his teeth, etc.

Maximum permissible concentrations of manganese

According to the data of the World Health Organization, since 1998, the norms for the maximum permissible content of manganese in tap water have been determined. This figure is 0.05 mg/l. While in the USA the figures reach 0.5 mg / l. In accordance with Russian sanitary standards, the level of the maximum permissible content of manganese in drinking water should not exceed 0.1 mg/l.

Excessive content of manganese reduces the organoleptic properties of water. Levels above 0.1 mg/l cause undesirable water taste and stains on sanitary ware. Accumulating in water pipes, manganese provokes the appearance of a black precipitate and, as a result, cloudy water.

Manganese Elimination Methods

If the presence of iron in water, as a rule, implies the presence of manganese, then manganese itself can be contained in water even in the absence of excess iron in it. At the same time, it does not change the taste, color and smell of water. In some cases, when manganese comes into contact with something, black or brown traces remain even if its minimum concentrations in water (in the amount of 0.05 mg / l) remain.

The maximum permissible concentration of manganese is determined in terms of its coloring properties. Depending on the ionic form, manganese is removed by ion exchange, aeration methods followed by filtration, catalytic oxidation, reverse osmosis, or distillation. Manganese dissolved in water oxidizes more slowly than iron, so it is difficult to remove it from water. Shallow waters and surface wells contain colloidal and organic manganese compounds. In such waters, insoluble manganese hydroxide, the so-called "black water", is found.
On the inner walls of heat-stressed elements and pipes, manganese is deposited as a black film, which greatly complicates the necessary heat transfer in technological processes.

In water obtained from underground wells and natural reservoirs, manganese is in the divalent form. This is a partially soluble form that precipitates out only when the solution is strongly heated. To carry out the purification of water from manganese, it is necessary to convert manganese ions into a tri- or tetravalent form. In it, manganese forms acid salts, hydroxides, insoluble oxides (depending on the reagent by which manganese is precipitated after oxidation).

In total, water purification processes consist in the oxidation of divalent manganese to tri-, tetravalent. After this, the tetravalent manganese reacts with oxygen or another substance, with which an insoluble precipitate is formed. And the precipitate is already filtered mechanically.

Aeration followed by filtration

Aeration in the process of water purification from manganese is carried out similarly to reagent-free water deironing: a vacuum ejection apparatus is used, with the help of which water is saturated with oxygen, capable of oxidizing manganese to the required valence, and then filtered using mechanical filters (sand and others).

This method of water purification is considered the most economical. However, it is impossible to use it in all cases, because for the oxidation of manganese with atmospheric oxygen, certain conditions must be met.

This purification method is relevant when the permanganate oxidizability of the source water is up to 9.5 mg/l. Mandatory is the presence of ferrous iron in the water. In the process of its oxidation, iron hydroxide is formed, which adsorbs divalent manganese and catalytically oxidizes it. The concentration ratio / must be at least 7/1.

catalytic oxidation

Catalytic processes are actively used in the process of water purification from manganese. Using a dosing pump, a layer of tetravalent manganese hydroxide is formed on the surface of the filter material, which is capable of oxidizing bivalent manganese oxide to a trivalent form. The trivalent form of the oxide is oxidized by dissolved atmospheric oxygen to an insoluble form, subject to high concentrations as well.

Reverse osmosis

To remove manganese from water, methods such as water purification by reverse osmosis and the introduction of oxidizing agents are used. This method is used when the concentration of manganese in the source water is extremely high. Strong oxidizing agents are used as a reagent: chlorine, its dioxide, sodium hypochlorite and ozone.

Demanganation with potassium permanganate

This method is applicable to both groundwater and surface water. The introduction of potassium permanganate into water provokes the oxidation of dissolved manganese with the formation of slightly soluble manganese oxide in accordance with the following equation:

3 Mn2+ + 2 KMnO4 + 2 H2O = 5 MnO2↓ + 4 H+ (1)

Precipitated manganese oxide (in the form of flakes) has a high developed specific surface, approximately 300 square meters per 1 g of sediment. This indicates its high sorption properties. This precipitate is an excellent catalyst as it can demanganize at pH 8.5. To get rid of 1 mg of divalent manganese, 1.92 m of potassium permanganate is required. This proportion assumes the oxidation of 97% of divalent manganese.

The next stage of water purification is the introduction of a coagulant to remove oxidation products and elements present in the water in the form of a suspension. Water after coagulation is filtered using sand filler. In addition, ultrafiltration equipment can be used.

Introduction of oxidizing reagents

The rate of oxidation of manganese by ozone, sodium hypochlorite, chlorine, chlorine dioxide depends on the pH. When chlorine or sodium hypochlorite is added, complete oxidative reaction observed at pH from 8.0-8.5, subject to the duration of interaction between the oxidizing agent and water 60-90 minutes. Often source water needs to be alkalized. This need arises when oxygen is used as an oxidizing agent and the pH does not exceed 7.

Theoretically, for the oxidation of divalent manganese to tetravalent, it is necessary to use 1.3 mg of the reagent per 1 mg of manganese. In practice, the doses are usually higher.

It is more effective to use chlorine dioxide or ozone. In this case, manganese oxidation will take 10-15 minutes (assuming a pH of 6.5-7.0). According to stoichiometry, the proportion of ozone should be 1.45 mg (or chlorine dioxide 1.35 mg) per 1 mg of divalent manganese. It is important to take into account that during ozonization, ozone will be decomposed by manganese oxides, so its proportion should be greater than in the theoretical calculation.

Ion exchange

To purify water in this way, hydrogen or sodium cationization is performed. During the purification process, water is treated in two layers of ion exchange material in order to more effectively remove all dissolved salts. Simultaneously and sequentially, a cation exchange resin with hydrogen ions H+, as well as an anion exchange resin with hydroxyl ions OH- are used. Given the fact that all water-soluble salts consist of anions and cations, the mixture of resins in the purified water replaces them with hydroxyl ions OH- and hydrogen H+. Finally, as a result chemical reaction positive and negative ions combine and form water molecules, that is, the process of water desalination takes place.

When choosing a multicomponent complex combination of ion exchange resins, effective and acceptable for water quality with a large limit of parameters, this method is the most promising in the fight against manganese and iron.

Distillation

This method involves the evaporation of water, followed by the concentration of steam. The boiling point of water molecules is 100 degrees Celsius. Other substances have different boiling points. Due to this difference, water is extracted. What boils at a lower temperature evaporates first, what evaporates at a higher temperature after most of the water has boiled away. The result is water without impurities. However, this technology is quite energy intensive.

For the period from 04/25/14 to 05/08/14, in 2 samples of drinking water (well), an excess of manganese and iron was found.
Manganese enters natural waters as a result of leaching of ferromanganese ores and other soil minerals. A significant amount comes in the process of decomposition of the remains of aquatic animals and plant organisms.
The content of manganese in spring water is subject to seasonal fluctuations.
MPC for manganese in drinking water is 0.1 mg/dm3.
Manganese is considered to be one of the most commonly found toxic elements in spring water and, when exceeded, can cause many undesirable health effects.
If the permissible concentration of manganese is exceeded in drinking water, the liquid acquires a yellowish tint and has an unpleasant astringent taste. Drinking such water is not only unpleasant because of the bad taste, but also dangerous to health.
The increased content of manganese in drinking water threatens with liver diseases, in which this metal is mainly concentrated. In addition, manganese, consumed with water, has the ability to penetrate into the small intestine, bones, kidneys, internal glands, and affect the brain. As a result of the constant use of drinking water, in which the content of this chemical element is exceeded, chronic poisoning with this metal may begin. The poisoning is either neurological or pulmonary. In the case of a neurological form of poisoning (when manganese penetrates into the tubules of nerve cells, the passage of nerve impulses is inhibited), the patient has complete indifference to the events taking place around him, drowsiness, loss of appetite, dizziness, and severe headaches.
Manganese poisoning is very difficult to diagnose. Symptoms of manganese poisoning are inherent in many diseases. Especially dangerous is the use of water with a high concentration of manganese by pregnant women. Mentally disabled children are very often born in women who consume water with a high concentration of manganese during pregnancy.
The concentration of iron in water is subject to noticeable seasonal fluctuations.
MPC of iron in drinking water is 0.3 mg/dm3.
Exceeding the MPC of iron in water increases the risk of heart attacks, allergic reactions, liver and blood diseases.
It should be noted that in all underground and surface water sources, the quality of water is different. In addition, in each water source, especially surface water, the nature of the water changes over time. Yes, maximum organic matter usually seen during floods.
With increasing urbanization and industrial production, chemicalization of agriculture, the anthropogenic factor has an increasing impact on the overall aquatic ecology, i. factor in human use of water.
Therefore, at present there is a great need to control the safety and quality of water consumed.
Chemical-toxicological studies must be carried out by accredited laboratories.

In the federal state institution "Central Research and Production Veterinary Radiological Laboratory" in the chemical and toxicological department, the determination of the content of iron and manganese in water (as well as a number of other elements, such as aluminum, silver, nickel, calcium, magnesium, chromium, sodium, silicon, cadmium, arsenic, lead, cobalt, nickel, etc.) is carried out by atomic emission spectrometry with inductively coupled argon plasma on a modern device Optima 7300DV.

Heavy metals are very dangerous toxic substances. Nowadays, monitoring the levels of various such substances is especially important in industrial and urban areas.

Although everyone knows what heavy metals are, not everyone knows which chemical elements still fall into this category. There are a lot of criteria by which different scientists define heavy metals: toxicity, density, atomic mass, biochemical and geochemical cycles, distribution in nature. According to one criterion, heavy metals include arsenic (a metalloid) and bismuth (a brittle metal).

General facts about heavy metals

More than 40 elements are known that are classified as heavy metals. They have atomic mass more than 50 a.u. Strange as it may seem, it is these elements that are highly toxic even at low cumulation for living organisms. V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo…Pb, Hg, U, Th… they all fall into this category. Even with their toxicity, many of them are important trace elements other than cadmium, mercury, lead and bismuth for which no biological role has been found.

According to another classification (namely, N. Reimers), heavy metals are elements that have a density greater than 8 g / cm 3. Thus, there will be fewer of these elements: Pb, Zn, Bi, Sn, Cd, Cu, Ni, Co, Sb.

Theoretically, heavy metals can be called the entire periodic table of elements starting with vanadium, but researchers prove to us that this is not entirely true. Such a theory is due to the fact that not all of them are present in nature within toxic limits, and confusion in biological processes is minimal for many. This is why many include only lead, mercury, cadmium, and arsenic in this category. The United Nations Economic Commission for Europe does not agree with this opinion and considers that heavy metals are zinc, arsenic, selenium and antimony. The same N. Reimers believes that by removing rare and noble elements from the periodic table, heavy metals remain. But this is also not a rule, others add gold, platinum, silver, tungsten, iron, manganese to this class. That's why I'm telling you that it's still not clear on this topic...

When discussing the balance of ions of various substances in solution, we will find that the solubility of such particles is associated with many factors. The main solubilization factors are pH, the presence of ligands in solution, and redox potential. They are involved in the processes of oxidation of these elements from one oxidation state to another, in which the solubility of the ion in solution is higher.

Depending on the nature of the ions, various processes can occur in the solution:

• hydrolysis,
• complexation with different ligands;
• hydrolytic polymerization.

Due to these processes, ions can precipitate or remain stable in solution. The catalytic properties of a certain element and its availability for living organisms depend on this.

Many heavy metals form fairly stable complexes with organic substances. These complexes are part of the mechanism of migration of these elements in ponds. Almost all heavy metal chelates are stable in solution. Also, complexes of soil acids with salts of various metals (molybdenum, copper, uranium, aluminum, iron, titanium, vanadium) have good solubility in a neutral, slightly alkaline and slightly acidic environment. This fact is very important, because such complexes can move in the dissolved state over long distances. Most exposed water resources- these are low-mineralized and surface water bodies, where the formation of other such complexes does not occur. To understand the factors that regulate the level of a chemical element in rivers and lakes, their chemical reactivity, bioavailability and toxicity, it is necessary to know not only the total content, but also the proportion of free and related forms metal.

As a result of the migration of heavy metals into metal complexes in solution, the following consequences can occur:

1. Firstly, the cumulation of ions of a chemical element increases due to the transition of these from bottom sediments to natural solutions;
2. Secondly, there is a possibility of changing the membrane permeability of the resulting complexes, in contrast to ordinary ions;
3. Also, the toxicity of an element in the complex form may differ from the usual ionic form.

For example, cadmium, mercury and copper in chelated forms have less toxicity than free ions. That is why it is not correct to talk about toxicity, bioavailability, chemical reactivity only by the total content of a certain element, while not taking into account the proportion of free and bound forms of a chemical element.

Where do heavy metals come from in our environment? The reasons for the presence of such elements may be wastewater from various industrial facilities involved in ferrous and non-ferrous metallurgy, mechanical engineering, and galvanization. Some chemicals are found in pesticides and fertilizers and thus can be a source of pollution for local ponds.

And if you enter into the secrets of chemistry, then the main culprit in the increase in the level of soluble salts of heavy metals is acid rain (acidification). A decrease in the acidity of the environment (a decrease in pH) entails the transition of heavy metals from poorly soluble compounds (hydroxides, carbonates, sulfates) to more readily soluble ones (nitrates, hydrosulfates, nitrites, bicarbonates, chlorides) in the soil solution.

Vanadium (V)

It should be noted first of all that contamination with this element by natural means is unlikely, because this element is very dispersed in the Earth's crust. In nature, it is found in asphalts, bitumens, coals, iron ores. Oil is an important source of pollution.

The content of vanadium in natural reservoirs

Natural reservoirs contain an insignificant amount of vanadium:

• in rivers - 0.2 - 4.5 µg / l,
• in the seas (on average) - 2 μg / l.

Anionic complexes (V 10 O 26) 6- and (V 4 O 12) 4- are very important in the processes of transition of vanadium in the dissolved state. Soluble vanadium complexes with organic substances, such as humic acids, are also very important.

Maximum allowable concentration of vanadium for the aquatic environment

Vanadium in high doses is very harmful to humans. Maximum allowable concentration for aquatic environment(MPC) is 0.1 mg/l, and in fishery ponds, MPC fish farms are even lower - 0.001 mg/l.

Bismuth (Bi)

Mainly, bismuth can enter rivers and lakes as a result of leaching processes of minerals containing bismuth. There are also man-made sources of pollution with this element. These can be glass, perfume and pharmaceutical factories.

The content of bismuth in natural reservoirs

• Rivers and lakes contain less than a microgram of bismuth per litre.
• But groundwater can contain even 20 μg / l.
• In the seas, bismuth, as a rule, does not exceed 0.02 µg/l.

Maximum allowable concentration of bismuth for the aquatic environment

Maximum allowable concentration of bismuth for the aquatic environment is 0.1 mg/l.

Iron (Fe)

Iron - chemical element not rare, it is contained in many minerals and rocks, and thus in natural reservoirs the level of this element is higher than other metals. It can occur as a result of the processes of weathering of rocks, the destruction of these rocks and dissolution. Forming various complexes with organic substances from a solution, iron can be in colloidal, dissolved and suspended states. It is impossible not to mention the anthropogenic sources of iron pollution. Waste water from metallurgical, metal-working, paint and varnish and textile factories sometimes goes off scale due to excess iron.

The amount of iron in rivers and lakes depends on chemical composition solution, pH and partly on temperature. Weighted forms of iron compounds have a size of more than 0.45 μg. The main substances that are part of these particles are suspensions with sorbed iron compounds, iron oxide hydrate and other iron-containing minerals. Smaller particles, ie colloidal forms of iron, are considered together with dissolved iron compounds. Iron in the dissolved state consists of ions, hydroxocomplexes and complexes. Depending on the valency, it is noticed that Fe(II) migrates in the ionic form, while Fe(III) remains in the dissolved state in the absence of various complexes.

In the balance of iron compounds in an aqueous solution, the role of oxidation processes, both chemical and biochemical (iron bacteria), is also very important. These bacteria are responsible for the transition of Fe(II) iron ions to the Fe(III) state. Ferric compounds tend to hydrolyze and precipitate Fe(OH) 3 . Both Fe(II) and Fe(III) are prone to the formation of hydroxo complexes of the – , + , 3+ , 4+ , ​​+ type, depending on the acidity of the solution. Under normal conditions in rivers and lakes, Fe(III) is associated with various dissolved inorganic and organic substances. At pH greater than 8, Fe(III) transforms into Fe(OH) 3 . Colloidal forms of iron compounds are the least studied.

Iron content in natural waters

In rivers and lakes, the level of iron fluctuates at the level of n * 0.1 mg/l, but can rise near swamps to several mg/l. In swamps, iron is concentrated in the form of humate salts (salts of humic acids).

Underground reservoirs with low pH contain record amounts of iron - up to several hundred milligrams per liter.

Iron is an important trace element and many important biological processes depend on it. It affects the intensity of phytoplankton development and the quality of microflora in water bodies depends on it.

The level of iron in rivers and lakes is seasonal. The highest concentrations in water bodies are observed in winter and summer due to water stagnation, but in spring and autumn the level of this element noticeably decreases due to mixing of water masses.

Thus, a large amount of oxygen leads to the oxidation of iron from the divalent form to the trivalent form, forming iron hydroxide, which precipitates.

Maximum permissible concentration of iron for the aquatic environment

Water with a large amount of iron (more than 1-2 mg / l) is characterized by poor taste. It has an unpleasant astringent taste and is unsuitable for industrial purposes.

The MPC of iron for the aquatic environment is 0.3 mg/l, and in fishery ponds the MPC of fish farms is 0.1 mg/l.

Cadmium (Cd)

Cadmium contamination can occur during soil leaching, during the decomposition of various microorganisms that accumulate it, and also due to migration from copper and polymetallic ores.

Man is also to blame for the contamination with this metal. Wastewater from various enterprises engaged in ore dressing, galvanic, chemical, metallurgical production may contain large amounts of cadmium compounds.

Natural processes to reduce the level of cadmium compounds are sorption, its consumption by microorganisms and precipitation of poorly soluble cadmium carbonate.

In solution, cadmium is, as a rule, in the form of organo-mineral and mineral complexes. Cadmium-based sorbed substances are the most important suspended forms of this element. Migration of cadmium in living organisms (hydrobionites) is very important.

Cadmium content in natural water bodies

The level of cadmium in clean rivers and lakes fluctuates at a level of less than a microgram per liter, in polluted waters the level of this element reaches several micrograms per liter.

Some researchers believe that cadmium, in small amounts, may be important for the normal development of animals and humans. Elevated concentrations of cadmium are very dangerous for living organisms.

Maximum allowable concentration of cadmium for the aquatic environment

MPC for the aquatic environment does not exceed 1 µg/l, and in fishery ponds the MPC for fish farms is less than 0.5 µg/l.

Cobalt (Co)

Rivers and lakes can become contaminated with cobalt as a result of leaching of copper and other ores, from soils during the decomposition of extinct organisms (animals and plants), and of course, as a result of the activity of chemical, metallurgical and metalworking enterprises.

The main forms of cobalt compounds are in dissolved and suspended states. Variations between these two states can occur due to changes in pH, temperature, and solution composition. In the dissolved state, cobalt is found in the form of organic complexes. Rivers and lakes have the characteristic that cobalt is represented by a divalent cation. In the presence of a large number of oxidizing agents in solution, cobalt can be oxidized to a trivalent cation.

It is found in plants and animals because it plays an important role in their development. It is one of the main trace elements. If there is a deficiency of cobalt in the soil, then its level in plants will be less than usual and, as a result, health problems may appear in animals (there is a risk of anemia). This fact is observed especially in the taiga-forest non-chernozem zone. It is part of vitamin B 12, regulates the absorption of nitrogenous substances, increases the level of chlorophyll and ascorbic acid. Without it, plants cannot grow required amount squirrel. Like all heavy metals, it can be toxic in large amounts.

The content of cobalt in natural waters

• Cobalt levels in rivers range from a few micrograms to milligrams per litre.
• In the seas, the average level of cadmium is 0.5 µg/l.

Maximum permissible concentration of cobalt for the aquatic environment

MPC for cobalt for the aquatic environment is 0.1 mg/l, and in fishery ponds the MPC for fish farms is 0.01 mg/l.

Manganese (Mn)

Manganese enters rivers and lakes through the same mechanisms as iron. Mainly, the release of this element in solution occurs during the leaching of minerals and ores that contain manganese (black ocher, brownite, pyrolusite, psilomelane). Manganese can also come from the decomposition of various organisms. Industry has, I think, the biggest role in manganese pollution (sewage from mines, chemical industry, metallurgy).

The decrease in the amount of assimilable metal in solution occurs, as in the case of other metals under aerobic conditions. Mn(II) is oxidized to Mn(IV), as a result of which it precipitates in the form of MnO 2 . Important factors in such processes are temperature, the amount of dissolved oxygen in the solution and pH. A decrease in dissolved manganese in solution can occur when it is consumed by algae.

Manganese migrates mainly in the form of suspensions, which, as a rule, indicate the composition of the surrounding rocks. They contain it as a mixture with other metals in the form of hydroxides. The predominance of manganese in colloidal and dissolved form indicates that it is associated with organic compounds forming complexes. Stable complexes are seen with sulfates and bicarbonates. With chlorine, manganese forms complexes less frequently. Unlike other metals, it is weaker retained in complexes. Trivalent manganese forms such compounds only in the presence of aggressive ligands. Other ionic forms (Mn 4+ , ​​Mn 7+) are less rare or not found at all under normal conditions in rivers and lakes.

Manganese content in natural water bodies

The seas are considered the poorest in manganese - 2 μg / l, in rivers its content is higher - up to 160 μg / l, but underground reservoirs are champions this time - from 100 μg to several mg / l.

Manganese is characterized by seasonal fluctuations in concentration, like iron.

Many factors have been identified that affect the level of free manganese in solution: the connection of rivers and lakes with underground reservoirs, the presence of photosynthetic organisms, aerobic conditions, biomass decomposition (dead organisms and plants).

An important biochemical role of this element, because it is included in the group of microelements. Many processes are inhibited in manganese deficiency. It increases the intensity of photosynthesis, participates in nitrogen metabolism, protects cells from the negative effects of Fe (II) while oxidizing it into a trivalent form.

Maximum permissible concentration of manganese for the aquatic environment

MPC for manganese for reservoirs is 0.1 mg/l.

Copper (Cu)

Not a single microelement has such an important role for living organisms! Copper is one of the most sought after trace elements. It is part of many enzymes. Without it, almost nothing works in a living organism: the synthesis of proteins, vitamins and fats is disrupted. Without it, plants cannot reproduce. Still, an excess amount of copper causes great intoxication in all types of living organisms.

Copper levels in natural waters

Although copper has two ionic forms, Cu(II) occurs most frequently in solution. Usually, Cu(I) compounds are hardly soluble in solution (Cu 2 S, CuCl, Cu 2 O). Different aquaionic coppers can arise in the presence of any ligands.

With today's high use of copper in industry and Agriculture, this metal can cause pollution environment. Chemical, metallurgical plants, mines can be sources Wastewater with a high copper content. Pipeline erosion processes also contribute to copper contamination. The most important minerals with a high content of copper are malachite, bornite, chalcopyrite, chalcocite, azurite, brontantine.

Maximum allowable concentration of copper for the aquatic environment

The MPC of copper for the aquatic environment is considered to be 0.1 mg/l; in fish ponds, the MPC of the fish farm of copper is reduced to 0.001 mg/l.

Molybdenum (Mo)

During the leaching of minerals from high content molybdenum, various compounds of molybdenum are released. High level molybdenum can be seen in rivers and lakes that are close to beneficiation factories and non-ferrous metallurgy enterprises. Due to different processes of precipitation of sparingly soluble compounds, adsorption on the surface of different rocks, as well as consumption by aquatic algae and plants, its amount may noticeably decrease.

Mostly in solution, molybdenum can be in the form of the MoO 4 2- anion. There is a possibility of the presence of molybdenum-organic complexes. Due to the fact that loose finely dispersed compounds are formed during the oxidation of molybdenite, the level of colloidal molybdenum increases.

The content of molybdenum in natural reservoirs

Molybdenum levels in rivers range between 2.1 and 10.6 µg/l. In the seas and oceans, its content is 10 µg/l.

At low concentrations, molybdenum helps the normal development of the organism (both vegetable and animal), because it is included in the category of microelements. Also he is integral part various enzymes such as xanthine oxylase. With a lack of molybdenum, a deficiency of this enzyme occurs and thus negative effects can occur. An excess of this element is also not welcome, because normal metabolism is disrupted.

Maximum permissible concentration of molybdenum for the aquatic environment

MPC for molybdenum in surface water bodies should not exceed 0.25 mg/l.

Arsenic (As)

Contaminated with arsenic are mainly areas that are close to mineral mines with a high content of this element (tungsten, copper-cobalt, polymetallic ores). A very small amount of arsenic can occur during the decomposition of living organisms. Thanks to aquatic organisms, it can be absorbed by these. Intensive assimilation of arsenic from solution is observed during the period of rapid development of plankton.

The most important arsenic pollutants are considered to be the enrichment industry, pesticide and dye factories, and agriculture.

Lakes and rivers contain arsenic in two states: suspended and dissolved. The proportions between these forms may vary depending on the pH of the solution and the chemical composition of the solution. In the dissolved state, arsenic can be trivalent or pentavalent, entering into anionic forms.

Arsenic levels in natural waters

In rivers, as a rule, the content of arsenic is very low (at the level of µg/l), and in the seas - an average of 3 µg/l. Some mineral waters may contain large amounts of arsenic (up to several milligrams per litre).

Most of the arsenic can contain underground reservoirs - up to several tens of milligrams per liter.

Its compounds are highly toxic to all animals and to humans. In large quantities, the processes of oxidation and oxygen transport to the cells are disrupted.

Maximum allowable concentration of arsenic for the aquatic environment

MPC for arsenic for the aquatic environment is 50 μg/l, and in fishery ponds, the MPC for fish farms is also 50 μg/l.

Nickel (Ni)

Nickel content in lakes and rivers is influenced by local rocks. If there are deposits of nickel and iron-nickel ores near the reservoir, the concentration can be even higher than normal. Nickel can enter lakes and rivers when plants and animals decompose. Blue-green algae contain record amounts of nickel compared to other plant organisms. Important waste waters with a high nickel content are released during the production of synthetic rubber, during nickel plating processes. Nickel is also released in large quantities during the combustion of coal and oil.

High pH can cause nickel to precipitate in the form of sulfates, cyanides, carbonates or hydroxides. Living organisms can reduce the level of mobile nickel by consuming it. The processes of adsorption on the rock surface are also important.

Water can contain nickel in dissolved, colloidal and suspended forms (the balance between these states depends on the pH of the medium, temperature and water composition). Iron hydroxide, calcium carbonate, clay adsorb nickel-containing compounds well. Dissolved nickel is in the form of complexes with fulvic and humic acids, as well as with amino acids and cyanides. Ni 2+ is considered the most stable ionic form. Ni 3+ is usually formed at high pH.

In the mid-1950s, nickel was added to the list of trace elements because it plays an important role in various processes as a catalyst. In low doses, it has a positive effect on hematopoietic processes. Large doses are still very dangerous for health, because nickel is a carcinogenic chemical element and can provoke various diseases of the respiratory system. Free Ni 2+ is more toxic than in the form of complexes (approximately 2 times).

Nickel level in natural waters

Maximum allowable concentration of nickel for the aquatic environment

MPC for nickel for the aquatic environment is 0.1 mg/l, but in fishery ponds the MPC for fish farms is 0.01 mg/l.

Tin (Sn)

Natural sources of tin are minerals that contain this element (stannin, cassiterite). Anthropogenic sources are plants and factories for the production of various organic paints and the metallurgical industry working with the addition of tin.

Tin is a low-toxic metal, which is why eating from metal cans we do not risk our health.

Lakes and rivers contain less than a microgram of tin per liter of water. Underground reservoirs may contain several micrograms of tin per liter.

Maximum permissible concentration of tin for the aquatic environment

Maximum allowable concentration of tin for the aquatic environment is 2 mg/l.

Mercury (Hg)

Mainly, elevated level mercury in water is seen in areas where there are deposits of mercury. The most common minerals are livingstone, cinnabar, metacinnabarite. Wastewater from manufacturing plants different medicines, pesticides, dyes may contain important amounts of mercury. Thermal power plants (which use coal as fuel) are considered another important source of mercury pollution.

Its level in solution decreases mainly due to marine animals and plants, which accumulate and even concentrate mercury! Sometimes the mercury content in marine life rises several times higher than in the marine environment.

Natural water contains mercury in two forms: suspended (in the form of sorbed compounds) and dissolved (complex, mineral compounds of mercury). In certain areas of the oceans, mercury can appear as methylmercury complexes.

Mercury and its compounds are highly toxic. At high concentrations, it has a negative effect on the nervous system, provokes changes in the blood, affects the secretion of the digestive tract and motor function. The products of mercury processing by bacteria are very dangerous. They can synthesize organic substances based on mercury, which are many times more toxic than inorganic compounds. When eating fish, mercury compounds can enter our body.

Maximum permissible concentration of mercury for the aquatic environment

MPC of mercury in plain water- 0.5 µg/l, and in fishery ponds, the maximum concentration limit for fish farms is less than 0.1 µg/l.

Lead (Pb)

Rivers and lakes can be polluted with lead in a natural way when lead minerals are washed off (galena, anglesite, cerussite), and in an anthropogenic way (burning coal, using tetraethyl lead in fuel, discharges from ore-dressing factories, wastewater from mines and metallurgical plants). The precipitation of lead compounds and the adsorption of these substances on the surface of various rocks are the most important natural methods for lowering its level in solution. From biological factors, hydrobionts lead to a decrease in the level of lead in solution.

Lead in rivers and lakes is in suspended and dissolved form (mineral and organo-mineral complexes). Also, lead is in the form of insoluble substances: sulfates, carbonates, sulfides.

Lead content in natural waters

About the toxicity heavy metal we have heard. It is very dangerous even in small quantities and can cause intoxication. Lead enters the body through the respiratory and digestive systems. Its excretion from the body is very slow, and it can accumulate in the kidneys, bones and liver.

Maximum allowable concentration of lead for the aquatic environment

MPC for lead for the aquatic environment is 0.03 mg/l, and in fishery ponds the MPC for fish farms is 0.1 mg/l.

Tetraethyl lead

It serves as an antiknock agent in motor fuels. Thus, vehicles are the main sources of pollution with this substance.

This compound is highly toxic and can accumulate in the body.

Maximum allowable concentration of tetraethyl lead for the aquatic environment

The maximum permissible level of this substance is approaching zero.

Tetraethyl lead is generally not allowed in the composition of waters.

Silver (AG)

Silver mainly enters rivers and lakes from underground reservoirs and as a consequence of the discharge of wastewater from enterprises (photographic enterprises, enrichment factories) and mines. Another source of silver can be algicidal and bactericidal agents.

In solution, the most important compounds are the silver halide salts.

Silver content in natural waters

In clean rivers and lakes, the silver content is less than a microgram per liter, in the seas - 0.3 µg / l. Underground reservoirs contain up to several tens of micrograms per liter.

Silver in ionic form (at certain concentrations) has a bacteriostatic and bactericidal effect. In order to be able to sterilize water with silver, its concentration must be greater than 2 * 10 -11 mol / l. Biological role silver in the body is still not well known.

Maximum allowable concentration of silver for the aquatic environment

The maximum permissible silver for the aquatic environment is 0.05 mg / l.

Increased turbidity is typical for artesian, well, and tap water. Turbidity is caused by suspended and colloidal particles that scatter light. It can be either organic or inorganic substances or both at the same time. On their own, particulate matter does not pose a serious health threat in most cases, but for modern equipment, it can cause premature failure. Increased turbidity of tap water is often associated with mechanical separation of pipeline corrosion products and biofilms developing in the central water supply system. The reason for the increased turbidity of artesian waters is usually clay or lime suspensions, as well as insoluble oxides of iron and other metals formed upon contact with air.

The quality of water from wells is the least stable, since groundwater is subject to external influences. High turbidity from wells can be associated with the ingress of sparingly soluble natural organic substances into groundwater from soils with technogenic pollution. High turbidity adversely affects the effectiveness of disinfection, as a result of which microorganisms attached to the surface of the particles survive and continue to develop on their way to the consumer. Therefore, reducing turbidity often improves the microbiological quality of the water.

iron in water

The high content of iron in the water supply is associated with various reasons. These impurities enter the water supply system as a result of corrosion of pipelines or the use of iron-containing coagulants at water treatment plants, and in artesian waters - as a result of contact with iron-containing minerals. The content of iron in artesian waters, on average, exceeds the standard value by 2-10 times. In some cases, the excess can be up to 30-40 times. Usually, immediately after receiving, artesian water does not bear visible signs of the presence of iron compounds, however, upon contact with atmospheric oxygen, a yellow color may appear after 2-3 hours, and with longer settling, a light brown precipitate may be observed. All this is the result of an oxidative process, during which heat is released. Stimulating the development of glandular bacteria in artesian water.

manganese in water

Manganese impurities from artesian wells are detected simultaneously with iron impurities. The source of their receipt is the same - the dissolution of manganese-containing minerals. An excess of manganese in drinking water worsens its taste, and when used for household needs, dark deposits are observed in pipelines and on the surfaces of heating elements. Washing hands with a high content of manganese leads to an unexpected effect - the skin first turns gray, and then completely blackens. With prolonged assimilation of water with a high content of manganese, the risk of developing diseases of the nervous system increases.

Oxidation and color

The increased oxidizability and color of surface and artesian water supply sources indicates the presence of impurities of natural organic substances - humic and fulvic acids, which are decomposition products of living and inanimate objects. A high content of organic matter in surface waters is recorded during the period of algae decay (July - August). One of the characteristics of the concentration of organic contaminants is permanganate oxidizability. In the area of ​​peat occurrence, especially in the regions of the far north and eastern Siberia, this parameter can be ten times higher than the permissible value. By themselves, natural organic matter does not pose a threat to health. However, with the simultaneous presence of iron and manganese, their organic complexes are formed, making it difficult to filter them by aeration, that is, oxidation with atmospheric oxygen. The presence of organic substances of natural origin makes it difficult to disinfect water by oxidative methods, since disinfection by-products are formed. These include trihalomethanes, haloacetic acid, haloketones, and haloacetonitrile. Most studies show that the substances of this group have a carcinogenic effect, and also have a negative effect on the organs of the digestive and endocrine systems. The main way to prevent the formation of disinfection by-products is its deep purification from natural organic substances before the chlorination stage, however traditional methods centralized water treatment does not provide this.

The smell of water. Water with the smell of hydrogen sulfide

The smell of tap, artesian and well water make it unfit for consumption. When assessing water quality, consumers are guided by individual sensations of smell, color and taste.

Drinking water should not have any odor noticeable to the consumer.

The reason for the smell of tap water is most often dissolved chlorine entering the water at the disinfection stage during centralized water treatment.

The smell of artesian can be associated with the presence of dissolved gases - hydrogen sulfide, sulfur oxide, methane, ammonia and others.

Some gases may be the products of the vital activity of microorganisms or the result of industrial pollution of water sources.

Well water is most susceptible to foreign pollution, so often an unpleasant odor can be associated with the presence of petroleum products and traces of household chemicals.

Nitrates

Nitrates in well and artesian water can pose a serious threat to the health of consumers, since their content can be several times higher than the current standard for drinking water.

The main reason for the entry of nitrates into surface and groundwater is the migration of fertilizer components in soils.

Consumption with a high content of nitrates leads to the development of methemoglobinemia - a condition characterized by the appearance in the blood of an increased value of methemoglobin (> 1%), which disrupts the transfer of oxygen from the lungs to the tissues. As a result of poisoning with nitrates, the respiratory function of the blood is sharply disturbed and the development of cyanosis, a bluish coloration of the skin and mucous membranes, may begin.

In addition, a number of studies have shown the negative effect of nitrates on the absorption of iodine in the body and the carcinogenic effect of the products of their interaction with various substances human body.

Hardness of water. Hard and soft water

It is mainly determined by the concentration of calcium and magnesium ions in it.

There is an opinion that hard water does not pose a danger to the health of consumers, but this contradicts the conclusions of many years of research by one of the largest nutritionists, American researcher Paul Breguet. He believes that he was able to establish the cause of early aging of the human body. The reason for this is hard water. According to Paul Brega, hardness salts "slagging" blood vessels in the same way as pipes through which water flows with a high content of hardness salts. This leads to a decrease in the elasticity of the vessels, making them fragile. This is especially evident in the thin blood vessels of the cerebral cortex, which, according to Brega, leads to senile insanity in older people.

Hard water creates a number of domestic problems, causing the formation of deposits and raids on the surface of pipelines and working elements of household appliances. This problem is especially relevant for appliances with heating elements - hot water boilers (boilers), washing machines and dishwashers.

When using hard water in everyday life, the layer of deposits of calcium and magnesium salts on the heat transfer surfaces is constantly growing, as a result of which the efficiency of heat transfer decreases and the consumption of thermal energy for heating increases. In some cases, overheating of the working elements and their destruction is possible.

Water purification from fluorine

The existence of fluorine was first suggested by the great chemist Lavoisier, back in the 18th century, but then he could not isolate it from compounds. After him, many well-known scientists tried to obtain free fluorine, but almost all of them either became disabled because of these experiments, or died during them. After that, fluorine was called "destructive" or "bringing death." And only in late XIX century, it was possible to isolate fluorine from its compounds by electrolysis.

As you can see, fluorine is very dangerous, and, nevertheless, an element with such properties is necessary for many living organisms, including humans. Artesian water contains fluorine in the form of compounds.

Fluorine is a difficult element, and the boundary between its deficiency and excess in the body is difficult to discern. It is very easy to exceed the dose of fluorine, and then it becomes for our body what it is in nature - a poison.

Fluorine is found in various foods: black and green tea, seafood, sea fish, walnuts, cereals - oatmeal, rice, buckwheat, eggs, liver, etc. Getting fluoride from food is quite difficult. For an adult to receive the daily norm of fluorine, it is necessary to eat 3.5 kg of grain bread, or 700 g of salmon, 300 g of walnuts.

Fluorine is most easily extracted from water. Fluorine performs many essential functions in our body. The state of the skeletal system, its strength and hardness, the condition and growth of hair, nails and teeth depend on it.

However, we warn that it is necessary to be wary of excess fluoride in the body. In this regard, from our point of view, it is not desirable that the concentration of fluorine exceed 0.5 - 0.8 mg / l, given that it is recommended to drink up to 2 liters per day clean water. With an excess of fluorine in the body, the metabolism and growth slows down, the bones of the skeleton are deformed, the enamel of the teeth is affected, the person weakens and vomiting may occur, breathing quickens, pressure drops, a spasm appears, and the kidneys are affected.