Sources of pollution water may be atmospheric precipitation, which carries various anthropogenic pollutants from the air and soil; municipal wastewater, mainly domestic wastewater (municipal), containing feces, detergents (detergents), pathogenic microorganisms; industrial wastewater from various industries.

The most persistent pollutants are petroleum oils. Pollutants from the pulp and paper, chemical, textile, metallurgical, mining, and food industries are dangerous; purification plants uranium ore and processing of nuclear fuel for reactors and nuclear power plants. The source of pollution is Agriculture in connection with the use of pesticides, fertilizers; due to the formation of livestock runoff rich in urea (they can enter water bodies from agricultural land with storm water).

Typically, a distinction is made between biological (organic), chemical and physical (thermal) water pollution.

Biological contamination – wastewater containing feces, urine, food waste, effluent from slaughterhouses, breweries, dairy and sugar factories, cheese factories, waste from the pulp and paper industry, tanneries, etc. Such waters are bacteriologically contaminated and can cause diseases: dysentery, intestinal infections, typhoid and others.

Chemical pollution water is caused by wastewater from enterprises containing toxic amounts of salts of lead, copper, nickel, zinc, cadmium, beryllium, nitrates and nitrites, sulfates and sulfides, persulfates, petroleum products, phenols, pesticides and other chemical compounds that disrupt the processes of photosynthesis and cause unsuitability water for fisheries, recreational purposes and household and drinking purposes.

Thermal pollution comes from thermal power plants. The discharge of heated water into natural bodies of water causes an increase in water temperature, replacing the usual flora with blue-green algae, which release when decomposing toxic substances. Such water is unsuitable for drinking, fishing, and often for industry, since disruption of technological processes and corrosion of metal structures are possible.

Toxic substances contained in waters are very dangerous for humans, as they actively accumulate in food chains.

Thus, hydrocarbons, aromatic amines, nitro compounds, when entering the human body, can cause cancer. There are cases of poisoning from fish containing mercury compounds.

Water pollution negatively affects the biosphere. Harmful substances from contaminated water affect the skin of the body, mucous membranes and can enter the body with food. The greatest harm to the biosphere is caused by chemical impurities in water. Even a slight increase in the concentration of some pollutants causes significant harm to living organisms. The greatest harm is caused by the following water pollution:

· Heavy metals: lead, cadmium, chromium, mercury, beryllium, etc. Cadmium causes bone disease. Chromium affects the skin (edema, eczema). Mercury causes chronic poisoning and disorders in the central nervous system. Beryllium is a generally toxic poison with a high degree of accumulation that affects the central nervous system.

· Chemical substances: cyanides, arsenic, fluorine, boron, etc. Thus, fluorine concentrations above 1.5 mg/l cause fluorosis, which affects human bones.

· Pesticides,used in the cultivation of agricultural land. Their harmful effects on the biosphere depend on the type of product and the form of its use.

· Bacterial contamination water pathogens of infectious diseases lead to epidemics (cholera, typhoid fever, anthrax, dysentery, etc.).

· Synthetic surfactants (surfactants) that disrupt water aeration and the self-purification process stimulate the proliferation of dangerous microorganisms.

These pollutants lead to diseases in animals and plants. And above all, they have a detrimental effect on life aquatic organisms a decrease in oxygen in water due to pollution with petroleum products, as well as thermal pollution of water bodies. The latter disrupts the thermal and biological regime of water bodies.

Water quality is characterized by its physical, chemical and bacteriological properties.

TO physical properties include: its temperature, color, turbidity, taste and smell. The temperature of water from wells should be 7-12°C. Water at a higher temperature loses its refreshing properties. Temperatures below 5° C are considered harmful to human health and lead to colds.

Under chromaticity understand its color and express it in degrees on the platinum-cobalt scale.

Turbidity determined by the content of suspended particles in water and expressed in milligrams per liter (mg/l). Water from underground sources has low turbidity.

The presence of organic substances in water sharply worsens its physical (organoleptic) characteristics, causing various kinds of odors (earthy, putrefactive, fishy, ​​swampy, pharmaceutical, camphorous, oil smell, chlorophenolic, etc.), increases color, foaming, and has an adverse effect for humans and animals.

It was found that minor changes physical properties water reduces the secretion of gastric juice, and pleasant taste sensations increase visual acuity and heart rate (unpleasant ones - reduce).

Chemical properties waters are characterized by the following indicators: active reaction, hardness, oxidability, content of dissolved salts.

Active reaction water is determined by the concentration of hydrogen ions. It is usually expressed in terms of pH. At pH=7 the environment is neutral; at pH<7 среда кислая, при pH>7 alkaline environment.

Hardness of water determined by the content of calcium and magnesium salts in it. It is expressed in milligram equivalents per liter (mg·eq/L). Water from underground sources has high hardness, while water from surface sources has relatively low hardness (3-6 mEq/l).

Hard water contains many mineral salts, which cause scale to form on the walls of dishes, boilers and other units - rock salt. Hard water is destructive and unsuitable for water supply systems. In such water, tea does not brew well, soap does not dissolve well, and vegetables, especially legumes, are hardly cooked.

Soft water should have a hardness of no more than 10 mEq/l.

IN last years It has been suggested that water with a low content of hardness salts contributes to the development of cardiovascular diseases.

Oxidability is determined by the content of dissolved organic substances in water and can serve as an indicator of contamination of the source with wastewater. For wells, wastewater that contains proteins, fats, carbohydrates, organic acids, ethers, alcohols, phenols, oil, etc. is especially dangerous.

Content of dissolved salts in water(mg/l) is characterized by dense (dry) sediment. Water from surface sources has less dense sediment than water from underground sources, i.e. contains less dissolved salts. The limit of mineralization of drinking water (dry residue) of 1000 mg/l was at one time established on an organoleptic basis. Waters with a high salt content have a brackish or bitter taste. They are allowed to be contained in water at the sensation threshold level: 350 mg/l for chlorides and 500 mg/l for sulfates. The lower limit of mineralization, at which the body's homeostasis is maintained by adaptive reactions, is a dry residue of 100 mg/l, the optimal level of mineralization is 200-400 mg/l. In this case, the minimum calcium content should be at least 25 mg/l, magnesium -10 mg/l.

Degree bacteriological contamination water is determined by the number of bacteria contained in 1 cubic cm of water and should be no more than 100. Water from surface sources contains bacteria introduced by sewage and rainwater, animals, etc. Water from underground artesian springs is usually not contaminated with bacteria.

There are pathogenic (disease-causing) and saprophytic bacteria. To assess the contamination of water with pathogenic bacteria, the content of E. coli in it is determined. Bacterial contamination is measured by coli titer and coli index. Coli titer– the volume of water containing one E. coli must be at least 300. Coli index– the number of E. coli contained in 1 liter of water should not be higher than 3.

• Geochemistry of natural and technogenic landscapes
  • DIDACTIC PLAN
  • LITERATURE
  • Water pollution assessment
  • Biochemical and chemical oxygen demand
  • Analytical determination of BOD and COD
  • Inorganic substances in water. Ions coming from fertilizers and salts used for snow melting and ice control. Acid emissions. Heavy metal ions. Basic chemical reactions in the hydrosphere
  • Methods of water purification: physical, chemical and biological. Basic principles and hardware design. Purification of drinking water: water treatment processes and the chemical reactions underlying them. Water standards
  • Soil pollution. Chemical effects of acid pollution
  • The role of metals in living nature
  • Necessity and toxicity of metal ions
  • Relationship between requirement and toxicity of metals in ecosystems
  • Potentially hazardous trace metals in the atmosphere, hydrosphere and lithosphere
  • Global transport of trace amounts of potentially hazardous metals
  • Microelements. Receipt and absorption of metals in the body
  • Molecular basis of metal toxicity. Toxicity series
  • Environmental factors affecting toxicity
  • Tolerance of organisms to metals. Carcinogenicity of metal ions. Ways metals affect the body
  • Heavy metal ions in natural waters. Forms of existence of metals in aquatic ecosystems, dependence of toxicity on form. Secondary water toxicity
  • The structure of the atmosphere
  • Distribution of temperature, pressure and other parameters over height
  • Reasons for the formation of characteristic layers in the atmosphere (barometric formula, convection, cosmic radiation). The meaning of layers for humans
  • Ionosphere
  • Change in chemical composition with altitude (inconsistency with the barometric formula)
  • Consideration of the atmosphere as a system (open, closed, isolated). Thermodynamic approach (N2O). Thunderstorms
  • Kinetic approach
  • Basic chemical reactions in the atmosphere and troposphere
  • Elements of chemical kinetics (reaction order, molecularity, dependence of rate on pressure)
  • Ozone layer
  • Destructive effect of halogens, freons, etc.
  • Characteristic chemical composition of atmospheric emissions
  • Chemical transformations of pollutants
  • Possibility of self-purification of the atmosphere
  • Boundaries of the biosphere, composition and mass of living matter
  • Clarks and geochemical functions of living matter, biogeochemical processes as a geological factor
  • Organic matter, processes of synthesis and decomposition

DIRECT CYCLE OF DECOMPOSITION OF NITROGEN-CONTAINING ORGANIC COMPOUNDS

It is represented by undecomposed protein substances, often of animal origin, as well as nitrogen, which is part of microorganisms, low plants and undecomposed remains of higher plants.

At the beginning of decomposition, ammonia is formed, then under the action of nitrifying bacteria in the presence of a sufficient amount of oxygen, ammonia is oxidized to nitrous acid (NO 2 -) ( nitrites) and then enzymes of another microbial family oxidize nitrous acid into nitric acid (NO 3 -) (nitrates).

With fresh pollution by waste, the content of water increases. AMMONIUM SALTS, that is, the ammonium ion is 1. An indicator recent pollution water with organic substances of protein nature. 2. Ammonium ion can be found in clean waters containing humic substances and in waters of deep ground origin.

Detection of NITRITES in water indicates recent contamination of the water source with organic matter (the content of nitrites in the water should be no more than 0.002 mg/l).

NITRATES- this is the final product of the oxidation of ammonium compounds; the presence in water in the absence of ammonium and nitrite ions indicates long-standing pollution water source. The nitrate content in mine well water should be 10 mg/l; in drinking water from centralized water supply up to 45 mg/l).

The detection of the simultaneous presence of ammonium salts, nitrites and nitrates in water indicates constant and long-term organic pollution of water.

CHLORIDES- are extremely widespread in nature and are found in all natural waters. A large amount of them in water makes it undrinkable due to its salty taste. In addition, chlorides can serve as an indicator of possible contamination of a water source with wastewater, therefore chlorides as sanitary indicator substances can be important if tests for their content are carried out repeatedly, over a more or less long period of time. (GOST "Drinking water not >> 350 mg/l).

SULPHATES- are also important indicators of organic water pollution, since they are always contained in household wastewater. (GOST "Drinking water" not >> 500 mg/l).

OXIDIZABILITY- this is the amount of oxygen in mg consumed for the oxidation of organic substances contained in 1 liter of water.

DISSOLVED OXYGEN

Due to the lack of contact with air, groundwater very often does not contain oxygen. The degree of saturation of surface waters varies greatly. Water is considered clean if it contains 90% of the maximum possible oxygen content at a given temperature, Medium purity - at 75-80%; Doubtful - at 50-75%; Contaminated - less than 50%.

According to the “Rules for the Protection of Surface Waters from Pollution,” the oxygen content in water at any time of the year must be at least 4 mg/l in a sample taken before 12 noon.

Due to significant fluctuations in the absolute oxygen content in natural waters, a more valuable indicator is the amount of oxygen consumption during a certain storage period of water at a certain temperature (BIOCHEMICAL DEMAND FOR OXYGEN for 5 or 20 days - BOD 5 - BOD 20).

To determine it, the test water is saturated with atmospheric oxygen by vigorous shaking, the initial oxygen content in it is determined and left for 5 or 20 days at a temperature of 20 0 C. After this, the oxygen content is determined again. Most often the indicator BOD 5 used to characterize the processes of self-purification of water bodies from pollution by industrial and domestic wastewater.

MAIN SOURCES OF RESERVOIR POLLUTION, CONSEQUENCES OF RESERVOIR POLLUTION

The main sources of water pollution are:

1. industrial and domestic wastewater (domestic water has high bacterial and organic contamination)

2. drainage water from irrigated lands

3. wastewater from livestock complexes (may contain pathogenic bacteria and helminth eggs)

4. organized (storm drainage) and unorganized surface runoff from the territory of settlements, agricultural fields (use of various chemicals - mineral fertilizers, pesticides, etc.)

5. mole wood rafting;

6. water transport (3 types of wastewater: fecal, domestic and water obtained in engine rooms).

In addition, additional sources of water contamination by pathogens of intestinal infections can be: hospital wastewater; mass bathing; washing clothes in a small pond.

Pollution entering water bodies:

1. violate the normal living conditions of the biocenosis of the reservoir;

2. contribute to changes in the organoleptic parameters of water (color, taste, smell, transparency);

3. increase bacterial contamination of water bodies. Human consumption of water that has not undergone purification and disinfection methods leads to the development of: infectious diseases, namely bacterial, dysentery, cholera, viral (viral hepatitis), zoonoses (leptospirosis, tularemia), helminthiasis, as well as human infection with protozoa (amoeba, ciliates slipper);

4. increase the amount of chemicals, the excess of which in drinking water contributes to the development of chronic diseases (for example, the accumulation of lead, beryllium in the body)

Therefore, the following hygienic requirements are imposed on the quality of drinking water:

1. Water must be epidemiologically safe against acute infectious diseases;

2. must be harmless in chemical composition;

3. water must have favorable organoleptic characteristics, must be pleasant to the taste, and must not cause aesthetic objection.

To reduce human morbidity associated with water-borne transmission, it is necessary:

implementation of an environmental complex of measures (enterprises are sources of pollution) and control over its implementation (controlling bodies of the Ministry of Natural Economy, FS Rospotrebnadzor);

application of methods to improve the quality of drinking water (vodokanal);

Cleaning technologies

Activities

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Ask a question to a specialist

Traditionally, water quality indicators are divided into physical (temperature, color, taste, smell, turbidity, etc.), chemical (water pH, alkalinity, hardness, oxidability, total mineralization (solids), etc.) and sanitary and bacteriological (general bacterial contamination of water, coli index, content of toxic and radioactive components in water, etc.).

To determine how well water meets the required standards, numerical values ​​of water quality indicators are documented, with which the measured indicators are compared.

The regulatory and technical literature that makes up water and sanitary legislation sets specific requirements for water quality, depending on its purpose. Such documents include GOST 2874-82 “Drinking water”, SanPiN 2.1.4.559-96 “Drinking water”, “Drinking water. Hygienic requirements for water quality in centralized drinking water supply systems", SanPiN 2.1.4.1116-02 "Drinking water. Hygienic requirements for the quality of water packaged in containers. Quality control", SanPiN 2.1.4.1175-02 "Hygienic requirements for the quality of water from non-centralized water supply. Sanitary protection of sources."

According to SanPin requirements, drinking water must be harmless in its chemical composition, safe in radiation and epidemiological terms, and also have a pleasant taste and smell. Therefore, to maintain your own health, it is so important to know what kind of water you drink. To do this, it must be submitted for analysis to check how well the water meets the requirements of sanitary standards and regulations.

Let us consider in detail the parameters by which water quality is assessed.

Physical indicators of water quality

Water temperature surface sources are determined by air temperature, humidity, speed and nature of water movement (as well as a number of other factors). Depending on the time of year, it can undergo significant changes (from 0.1 to 30º C). For underground sources, the water temperature is more stable (8-12 º C).

The optimal water temperature for drinking purposes is 7-11 ºС.

It is worth noting that this water parameter has great importance for some industries (for example, for cooling and steam condensation systems).

Turbidity– an indicator of the content of various suspended substances in water (mineral origin - particles of clay, sand, silt; inorganic origin - carbonates of various metals, iron hydroxide; organic origin - plankton, algae, etc.). Suspended substances enter the water due to erosion of the banks and bottom of the river, their entry with melt, rain and wastewater.

Underground springs, as a rule, have a slight turbidity of water due to the presence of suspended iron hydroxide in it. For surface waters, turbidity is often caused by the presence of zoo- and phytoplankton, silt or clay particles; its value fluctuates throughout the year.

Water turbidity is usually expressed in milligrams per liter (mg/L); its value for drinking water according to SanPiN 2.1.4.559-96 standards should not exceed 1.5 mg/l. For a number of productions in the food, medical, chemical, and electronic industries, water of the same or more High Quality. At the same time, in many production processes it is permissible to use water with a high content of suspended solids.

Water color- an indicator characterizing the intensity of water color. It is measured in degrees on the platinum-cobalt scale, and the water sample under study is compared in color with standard solutions. The color of water is determined by the presence of impurities in it, both organic and inorganic. This characteristic is strongly influenced by the presence in water of organic substances washed out from the soil (humic and fulvic acids, mainly); iron and other metals; technogenic pollution from industrial wastewater. SanPiN 2.1.4.559-96 requirement – ​​the color of drinking water should be no more than 20º. Selected species industries are tightening requirements for the color value of water.

Smell and taste of water– this characteristic is determined organoleptically (using the senses), so it is quite subjective.

The odors and tastes that water may have appear due to the presence in it of dissolved gases, organic substances, mineral salts, and chemical man-made pollutants. The intensity of odors and tastes is determined on a five-point scale or by the “threshold of dilution” of the test water sample with distilled water. In this case, the dilution ratio necessary to eliminate the smell or taste is established. The determination of smell and taste occurs through direct tasting at room temperature, as well as at a temperature of 60º C, which causes them to intensify. Drinking water at 60º C should not have a taste or odor of more than 2 points (requirements of GOST 2874-82).

In accordance with a 5-point scale: at 0 points - no smell or taste is detected;

with a score of 1, the water has a very slight odor or taste, detectable only by an experienced researcher;

with 2 points there is a slight smell or taste, obvious to a non-specialist;

at 3 points, a noticeable odor or taste is easily detected (which is the reason for complaints about water quality);

with a score of 4, there is a distinct smell or taste that can make you refrain from drinking water;

with a score of 5, the water has such a strong smell or taste that it becomes completely unfit for drinking.

The taste of water is determined by the presence of dissolved substances in it, giving it a certain taste, which can be salty, bitter, sweet and sour. Natural waters, as a rule, have only a salty and bitter aftertaste. Moreover, a salty taste appears in water containing sodium chloride, and a bitter taste comes from excess magnesium sulfate. Water with a large amount of dissolved carbon dioxide (so-called mineral water) has a sour taste. Water with an inky or ferrous taste is saturated with iron and manganese salts; an astringent taste is given to it by calcium sulfate and potassium permanganate; The alkaline taste is caused by the content of soda, potash, and alkali in the water. The taste can be of natural origin (presence of manganese, iron, methane, hydrogen sulfide, etc.) or artificial origin (due to industrial waste discharge). SanPiN 2.1.4.559-9 requirements for drinking water - taste no more than 2 points.

Odors in water are given by various living and dead organisms, plant debris, specific substances secreted by certain algae and microorganisms, as well as the presence of dissolved gases in water, such as chlorine, ammonia, hydrogen sulfide, mercaptans or organic and organochlorine contaminants. Odors can be of natural (natural) or artificial origin. The first include such odors as woody, aromatic, earthy, swampy, moldy, putrid, grassy, ​​fishy, ​​vague and hydrogen sulfide, etc. Odors of artificial origin get their name from the substances that determine them: camphor, phenolic, chlorine, resinous, pharmaceutical, chlorine-phenolic, smell of petroleum products, etc.

SanPiN 2.1.4.559-9 requirements for drinking water - odor no more than 2 points.

Chemical indicators of water quality

General mineralization(dry residue). Total mineralization is a quantitative indicator of substances dissolved in 1 liter of water (inorganic salts, organic substances - except gases). This indicator is also called total salt content. Its characteristic is the dry residue obtained by evaporating filtered water and drying the retained residue to a constant weight. Russian standards allow the mineralization of water used for domestic and drinking purposes to be no more than 1000 - 1500 mg/l. Dry residue for drinking water should not exceed 1000 mg/l.

Active water reaction(the degree of its acidity or alkalinity) is determined by the ratio of the acidic (hydrogen) and alkaline (hydroxyl) ions existing in it. When characterizing it, they use pH - hydrogen and hydroxyl indicators, which determine, respectively, the acidity and alkalinity of water. The pH value is equal to the negative decimal logarithm of the concentration of hydrogen ions in water. With equal amounts of acidic and alkaline ions, the reaction of water is neutral, and the pH value is 7. At pH<7,0 вода имеет кислую реакцию; при рН>7.0 – alkaline. SanPiN 2.1.4.559-96 standards require that the pH value of drinking water be within the range of 6.0...9.0. Most natural sources have a pH value within these ranges. However, it may cause a significant change in pH value. Correct assessment of water quality and accurate choice of method for its purification requires knowledge of the pH of water sources at different periods of the year. Water with low pH values ​​is highly corrosive to steel and concrete.

Water quality is often described through a term such as hardness. Requirements for water quality in terms of hardness in Russia and Europe are very different: 7 mEq/l (according to Russian standards) and 1 mEq/l (EU Council directive). Increased hardness is the most common water quality problem.

Hardness of water– an indicator characterizing the content of hardness salts in water (mainly calcium and magnesium). It is measured in milligram equivalents per liter (mg-eq/L). There are such concepts as carbonate (temporary) hardness, non-carbonate (permanent) hardness and total water hardness.

Carbonate hardness (removable) is an indicator of the presence of calcium and magnesium bicarbonate in water. When water boils, it decomposes with the formation of slightly soluble salts and carbon dioxide.

Non-carbonate or constant hardness is determined by the content of non-carbonate calcium and magnesium salts in water - sulfates, chlorides, nitrates. When water is boiled, they do not precipitate and remain in solution.

Total hardness is the total content of calcium and magnesium salts in water; is the sum of carbonate and non-carbonate hardness.

Depending on the amount of hardness, water is characterized as:

The amount of water hardness varies significantly depending on what types of rocks and soils make up the drainage basin; depending on weather conditions and season of the year. Thus, in surface sources, water is, as a rule, relatively soft (3...6 mEq/l) and depends on the location - the further south, the higher the water hardness. The hardness of groundwater varies depending on the depth and location of the aquifer horizon and the amount of annual precipitation. In a limestone layer, water hardness is usually 6 mEq/L or more.

The hardness of drinking water (according to SanPiN 2.1.4.559-96) should not exceed 7.0 mEq/l.

Hard water has an unpleasant taste due to excess calcium. The danger of constantly drinking water with increased hardness is a decrease in gastric motility, the accumulation of salts in the body, the risk of joint diseases (arthritis, polyarthritis) and the formation of stones in the kidneys and bile ducts. True, very soft water is also not beneficial. Soft water, which is highly active, can wash calcium out of bones, which leads to their fragility; development of rickets in children. Another unpleasant property of soft water is its ability, when passing through the digestive tract, to wash away beneficial organic substances, including beneficial bacteria. The best option is water with a hardness of 1.5-2 mEq/l.

It is already common knowledge that it is undesirable to use hard water for household purposes. Consequences such as plaque on plumbing fixtures and fittings, scale formation in water heating systems and appliances are obvious! The formation of sediment of calcium and magnesium salts of fatty acids during household use of hard water leads to a significant increase in the consumption of detergents and a slowdown in the cooking process, which is problematic for the food industry. In some cases, the use of hard water for production purposes (in the textile paper industry, artificial fiber enterprises, to power steam boilers, etc.) is prohibited due to undesirable consequences.

The use of hard water reduces the service life of water heating equipment (boilers, central water supply batteries, etc.). Deposition of hardness salts (Ca and Mg hydrocarbonates) on the inner walls of pipes, scale deposits in water heating and cooling systems reduce the flow area and reduce heat transfer. It is not allowed to use water with high carbonate hardness in recycling water supply systems.

Alkalinity of water. The total alkalinity of water is the sum of the hydrates and anions of weak acids contained in it (silicic, carbonic, phosphoric, etc.). When characterizing groundwater, in the vast majority of cases, hydrocarbonate alkalinity is used, that is, the content of hydrocarbonates in water. Forms of alkalinity: bicarbonate, carbonate and hydrate. Determination of alkalinity (mg-eq/l) is carried out for the purpose of monitoring the quality of drinking water; to determine the suitability of water for irrigation; to calculate carbonate content for subsequent wastewater treatment.

Maximum permissible concentration for alkalinity is 0.5 - 6.5 mmol / dm3.

Chlorides– their presence is observed in almost all waters. Their presence in water is explained by the leaching of sodium chloride (table salt), a very common salt on Earth, from rocks. A significant amount of sodium chlorides is found in sea water, as well as in the water of some lakes and underground springs.

Depending on the standard, the maximum permissible concentration of chlorides in drinking water is 300...350 mg/l.

An increased content of chlorides with the simultaneous presence of nitrites, nitrates and ammonia in the water occurs when the source is contaminated with domestic wastewater.

Sulfates present in groundwater as a result of the dissolution of gypsum present in the formations. If there is an excessive content of sulfates in water, a person may experience gastrointestinal upset (these salts have a laxative effect).

The maximum permissible concentration of sulfates in drinking water is 500 mg/l.

Content silicic acids. Silicic acids of various forms (from colloidal to ionic-dispersed) are found in water from underground and surface sources. Silicon has low solubility and its content in water is usually low. Silicon also gets into water with industrial wastewater from enterprises producing ceramics, cement, glass products, and silicate paints.

The maximum permissible concentration for silicon is 10 mg/l. The use of water containing silicic acids is prohibited for feeding high-pressure boilers - due to the formation of silicate scale on the walls.

Phosphates There is usually little in the water, so their increased content signals possible contamination by industrial wastewater or runoff from agricultural fields. With an increased content of phosphates, blue-green algae develop intensively, releasing toxins into the water when they die.

The maximum permissible concentration for phosphorus compounds in drinking water is 3.5 mg/l.

Fluorides And iodides. Fluorides and iodides have some similarities. A deficiency or excess of these elements in the human body leads to serious diseases. For example, a deficiency (excess) of iodine provokes diseases of the thyroid gland (“goiter”), which develop when the daily iodine intake is less than 0.003 mg or more than 0.01 mg. Fluorides are found in minerals - fluoride salts. To preserve human health, the fluoride content in drinking water should be in the range of 0.7 - 1.5 mg/l (depending on the climate).

Surface sources have predominantly low fluorine content (0.3-0.4 mg/l). The fluorine content in surface waters increases as a result of the discharge of industrial fluoride-containing wastewater or when water comes into contact with soils saturated with fluorine compounds. Thus, artesian and mineral waters in contact with fluorine-containing water-bearing rocks have a maximum fluorine concentration of 5-27 mg/l or more. An important characteristic for human health is the amount of fluoride in their daily diet. Typically, the fluoride content in the daily diet ranges from 0.54 to 1.6 mg of fluoride (average - 0.81 mg). It is worth noting that the human body enters 4-6 times less fluoride with food than with drinking water, which has its optimal content (1 mg/l).

With an increased fluorine content in water (more than 1.5 mg/l), there is a danger of endemic fluorosis (the so-called “spotted tooth enamel”), rickets and anemia in the population. These diseases are accompanied by characteristic dental damage, disruption of skeletal ossification processes, and exhaustion of the body. Therefore, the fluoride content in drinking water is limited. It is also a fact that some fluorine content in water is necessary to reduce the level of diseases determined by the consequences of odontogenic infection (cardiovascular pathology, rheumatism, kidney disease, etc.). When drinking water with a fluoride content of less than 0.5 mg/l, dental caries develops, so in such cases doctors recommend using fluoride-containing toothpaste. Fluoride is better absorbed by the body from water. Based on the above, the optimal dose of fluoride in drinking water is 0.7...1.2 mg/l.

Maximum permissible concentration of fluorine is 1.5 mg/l.

Oxidability permanganate– parameter determined by the presence of organic substances in water; In part, it can signal that the source is polluted with wastewater. Depending on what oxidizing agent is used , there is a difference between permanganate oxidation and bichromate oxidability (or COD - chemical oxygen demand). Permanganate oxidability is a characteristic of the content of easily oxidized organic matter, bichromate - the total content of organic substances in water. The quantitative value of these indicators and their ratio allows us to indirectly judge the nature of the organic substances present in water, as well as the methods and effectiveness of water purification.

According to SanPiN requirements: the value of permanganate oxidation of water should not exceed 5.0 mg O 2 /l. Water with permanganate oxidation less than 5 mg O 2 /l is considered clean, more than 5 mg O 2 /l - dirty.

In truly dissolved form (ferrous iron Fe2+). It is usually found in artesian wells (there is no dissolved oxygen). The water is clear and colorless. If the content of such iron in it is high, then when settled or heated, the water becomes yellowish-brown;

In undissolved form (ferric iron Fe3+) is found in surface water supplies. The water is clear - with brownish-brown sediment or pronounced flakes;

In a colloidal state or in the form of a finely dispersed suspension. The water is cloudy, colored, yellowish-brown opalescent. Colloidal particles, being in suspension, do not precipitate even after long-term settling;

In the form of so-called organic iron - iron salts and humic and fulvic acids. The water is clear, yellowish-brown;

Iron bacteria that form brown slime on water pipes.

The iron content in surface waters of central Russia is from 0.1 to 1.0 mg/dm 3 iron; in groundwater this value reaches 15-20 mg/dm3 or more. It is important to analyze the iron content in wastewater. Water bodies are especially contaminated with iron by wastewater from metalworking, metallurgical, paint and varnish industries, textiles, as well as agricultural runoff. The concentration of iron in water is affected by the pH value and oxygen content in the water. In well and borehole water, iron can be in oxidized and reduced form, but when the water settles, it always oxidizes and can precipitate.

SanPiN 2.1.4.559-96 allow general content iron no more than 0.3 mg/l.

It is believed that iron is not toxic to the human body, but with prolonged consumption of water with excess iron content, deposition of its compounds in human tissues and organs can occur. Water contaminated with iron has an unpleasant taste and causes inconvenience in everyday life. On a number industrial enterprises that use water to wash the product during its manufacture, for example, in the textile industry, even little content Iron in water significantly reduces product quality.

Manganese found in water in similar modifications. Manganese is a metal that activates a number of enzymes involved in the processes of respiration, photosynthesis, affecting hematopoiesis and mineral metabolism. With a lack of manganese in the soil, plants experience chlorosis, necrosis, and spotting. Therefore, soils poor in manganese (carbonate and over-limed) are enriched with manganese fertilizers. For animals, the lack of this element in feed leads to slower growth and development, disruption of mineral metabolism, and the development of anemia. A person suffers from both a deficiency and an excess of manganese.

SanPiN 2.1.4.559-96 standards allow the manganese content in drinking water to be no more than 0.1 mg/l.

An excess of manganese in water can cause diseases of the human skeletal system. This water has an unpleasant metallic taste. Its long-term use leads to the deposition of manganese in the liver. The presence of manganese and iron in water promotes the formation of ferruginous and manganese bacteria, the waste products of which in pipes and heat exchangers cause a decrease in their cross-section, sometimes even complete blockage. Water used in the food, textile industry, plastics production, etc. must contain strictly limited quantity iron and manganese.

Also, an excess of manganese leads to staining of laundry during washing and the formation of black spots on plumbing fixtures and dishes.

Sodium And potassium- the entry of these elements into groundwater occurs during the process of dissolution of bedrock. The main source of sodium in natural waters is deposits of table salt NaCl, which arose in the locations of ancient seas. Potassium is less common in waters due to its absorption by soil and plants.

Sodium plays an important biological role for most forms of life on Earth, including humans. The human body contains approximately 100 g of sodium. Sodium ions carry out the task of activating enzymatic metabolism in the human body.

According to SanPiN 2.1.4.559-96, the maximum permissible concentration of sodium is 200 mg/l. Excess sodium in water and food provokes the development of hypertension and hypertension in humans.

Potassium promotes increased removal of water from the body. This property is used to facilitate the functioning of the cardiovascular system in case of its insufficiency, disappearance or significant reduction of edema. Lack of potassium in the body leads to dysfunction of the neuromuscular (paralysis and paresis) and cardiovascular systems and contributes to depression, incoordination of movements, muscle hypotension, convulsions, arterial hypotension, changes in the ECG, nephritis, enteritis, etc. Potassium MPC - 20 mg/l.

Copper, zinc, cadmium, arsenic, lead, nickel, chromium And mercury– the entry of these elements into water supply sources occurs mainly with industrial wastewater. An increase in the content of copper and zinc may also be a consequence of corrosion of galvanized and copper water pipes in the case of an increased content of aggressive carbon dioxide.

According to SanPiN standards, the maximum permissible concentration for these elements is: for copper - 1.0 mg/l; zinc - 5.0 mg/l; lead - 0.03 mg/l; cadmium - 0.001 mg/l; nickel - 0.1 mg/l (in EU countries - 0.05 mg/l), arsenic - 0.05 mg/l; chromium Cr3+ - 0.5 mg/l, mercury - 0.0005 mg/l; chromium Cr4+ - 0.05 mg/l.

All these compounds are heavy metals that have a cumulative effect, that is, they tend to accumulate in the body.

Cadmium very toxic. The accumulation of cadmium in the body can lead to diseases such as anemia, damage to the liver, kidneys and lungs, cardiopathy, pulmonary emphysema, osteoporosis, skeletal deformation, hypertension. An excess of this element provokes and enhances the deficiency of Se and Zn. Symptoms of cadmium poisoning include damage to the central nervous system, protein in the urine, acute bone pain, and genital dysfunction. All chemical forms of cadmium are hazardous.

Aluminum- a light silvery-white metal. First of all, it enters water during the water treatment process - as part of coagulants and during the discharge of wastewater from bauxite processing.

In water, the maximum permissible concentration for aluminum salts is 0.5 mg/l.

When there is an excess of aluminum in water, damage to the human central nervous system occurs.

Bor And selenium– the presence of these elements in some natural waters is found in very low concentrations. It must be remembered that their increased concentration leads to serious poisoning.

Oxygen remains in water in dissolved form. There is no dissolved oxygen in groundwater. Its content in surface waters depends on the water temperature, and is also determined by the intensity of the processes of enrichment or depletion of water with oxygen, reaching up to 14 mg/l.

Even significant content oxygen And carbon dioxide does not deteriorate the quality of drinking water, while at the same time promoting the growth of metal corrosion. An increase in water temperature, as well as its mobility, intensifies the corrosion process. The increased content of aggressive carbon dioxide in water also makes the walls of concrete pipes and tanks susceptible to corrosion. The presence of oxygen is not allowed in the feed water of medium and high pressure steam boilers. Hydrogen sulfide has the property of giving water a characteristic unpleasant odor and causing corrosion of the metal walls of boilers, tanks and pipes. Because of this, the presence of hydrogen sulfide in drinking water and in water for most industrial needs is not allowed.

Nitrogen compounds. Nitrogen-containing substances include nitrites NO 2 - , nitrates NO 3 - and ammonium salts NH 4 + , almost always present in all waters, including groundwater. Their presence indicates that the water contains organic substances of animal origin. These substances are formed as a result of the breakdown of organic impurities, mainly urea and proteins, which enter the water with household wastewater. The group of ions under consideration is closely interconnected.

The first decomposition product is ammonia (ammonium nitrogen), is formed as a result of the breakdown of proteins and is an indicator of fresh fecal contamination. The oxidation of ammonium ions to nitrates and nitrites in natural water is carried out by the bacteria Nitrobacter and Nitrosomonas. Nitrites- the best indicator of fresh fecal contamination of water, especially if the content of ammonia and nitrites is simultaneously elevated. Nitrates-an indicator of older organic fecal contamination of water. The content of nitrates together with ammonia and nitrites is unacceptable.

Thus, the presence, quantity and ratio of nitrogen-containing compounds in water allows us to judge how strongly and for how long the water has been contaminated with human waste products. In the absence of ammonia in the water and, at the same time, the presence of nitrites and especially nitrates, we can conclude that the reservoir was polluted a long time ago, and during this time the water self-purified. If ammonia is present in the reservoir and there are no nitrates, it means that the water has been polluted with organic substances recently. Ammonia and nitrites are not allowed in drinking water.

MPC in water: ammonium - 2.0 mg/l; nitrites - 3.0 mg/l; nitrates - 45.0 mg/l.

If the concentration of ammonium ion in water exceeds background values, it means that pollution has occurred recently and the source of pollution is close. It can be livestock farms, municipal wastewater treatment plants, accumulations of nitrogen fertilizers, manure, settlements, industrial waste settling tanks, etc.

When drinking water with a high content of nitrates and nitrites, the oxidative function of the blood is disrupted.

Chlorine introduced into drinking water when it is. Chlorine exhibits its disinfecting effect by oxidizing or chlorinating (replacing) the molecules of substances that are part of the cytoplasm of bacterial cells, as a result of which the bacteria die. The causative agents of dysentery, typhoid fever, cholera and paratyphoid fever are extremely sensitive to chlorine. Relatively small doses of chlorine disinfect even water that is heavily contaminated with bacteria. However, complete sterilization of water does not occur due to the survival of individual chlorine-resistant individuals.

Free chlorine- a substance harmful to human health, therefore, the content of residual free chlorine in drinking water of centralized water supply is strictly regulated by SanPiN hygienic standards. SanPiN sets the upper and minimum permissible limits for the content of free residual chlorine. The problem is that, although the water is disinfected at the water treatment plant, on the way to the consumer it is at risk of secondary contamination. For example, in a steel underground main there may be fistulas through which soil contaminants enter the main water.

Therefore, SanPiN 2.1.4.559-96 stipulates that the residual chlorine content in tap water is not less than 0.3 mg/l and not more than 0.5 mg/l.

Chlorine is toxic and a strong allergenic agent, so chlorinated water has an adverse effect on the skin and mucous membranes. This includes redness in various areas of the skin and manifestations of allergic conjunctevitis (swelling of the eyelids, burning, lacrimation, pain in the eye area). Chlorine also has a harmful effect on the respiratory system: as a result of staying in a pool with chlorinated water for several minutes, 60% of swimmers experience bronchospasm.

About 10% of the chlorine used in water chlorination is formed by chlorine-containing compounds, such as chloroform, dichloroethane, carbon tetrachloride, tetrachlorethylene, trichloroethane. 70 - 90% of chlorine-containing substances formed during water treatment are chloroform. Chloroform contributes to occupational chronic poisoning with primary damage to the liver and central nervous system.

Also, during chlorination there is a possibility of the formation of dioxins, which are extremely toxic compounds. The high degree of toxicity of chlorinated water greatly increases the risk of developing cancer. Thus, American experts consider chlorine-containing substances in drinking water to be indirectly or directly responsible for 20 cancers per 1 million inhabitants.

Hydrogen sulfide It is found in groundwater and is predominantly of inorganic origin.

In nature, this gas is constantly formed during the decomposition of protein substances. It has a characteristic unpleasant odor; provokes corrosion of the metal walls of tanks, boilers and pipes; is a general cellular and catalytic poison. When combined with iron, it forms a black precipitate of iron sulfide FeS. All of the above is the basis for the complete removal of hydrogen sulfide from drinking water (see GOST 2874-82 "Drinking water").

It is worth noting that SanPiN 2.1.4.559-96 allows the presence of hydrogen sulfide in water up to 0.003 mg/l. The question is: isn’t this a typo in the regulatory document?!

Microbiological indicators. Total microbial count(TMC) is determined by the number of bacteria contained in 1 ml of water. According to GOST requirements, drinking water should not contain more than 100 bacteria per ml.

The number of coliform bacteria is of particular importance for the sanitary assessment of water. The presence of E. coli in water is evidence of its contamination with fecal waste and, as a consequence, the risk of pathogenic bacteria entering it. Determining the presence of pathogenic bacteria during biological analysis of water is difficult, and bacteriological studies are reduced to determining the total number of bacteria in 1 ml of water growing at 37ºC, and E. coli - coli bacteria. The presence of the latter signals water contamination with secretions of people, animals, etc. The minimum volume of test water, ml, per one E. coli is called colititre, and the number of E. coli in 1 liter of water is called the coli index. According to GOST 2874-82, a coli index of up to 3 is allowed, a colititre of at least 300, and total number bacteria in 1 ml - up to 100.

According to SanPiN 2.1.4.559-96, the total microbial count is 50 CFU/ml, common coliform bacteria(OKB) CFU/100ml and thermotoletarian coliform bacteria(TCB) CFU/100ml - not allowed.

Pathogenic bacteria and viruses found in water can cause diseases such as dysentery, typhoid fever, paraphyte, amoebiasis, cholera, diarrhea, brucellosis, infectious hepatitis, tuberculosis, acute gastroenteritis, anthrax, polio, tularemia, etc.

Company Waterman offers you a professional solution to the problem of water purification from compounds whose content in water is higher than the standard. Our specialists will advise on any questions that may arise and help in choosing and implementing the optimal water treatment scheme, based on specific initial data.

Natural water has a slightly alkaline reaction (6.0-9.0). An increase in alkalinity indicates pollution or blooming of the reservoir. An acidic reaction of water is observed in the presence of humic substances or the penetration of industrial wastewater.

Rigidity. Water hardness depends on chemical composition the soil through which water passes, the content of carbon monoxide in it, the degree of contamination with organic matter. It is measured either in mEq/L or in degrees. According to the degree of hardness, water can be: soft (up to 3 mg-eq/l); medium hardness (7 mg = eq/L); hard (14 mg=eq/l); very hard (over 14 mg-eq/L). Very hard water has an unpleasant taste and can worsen the course of kidney stones.

The oxidability of water is the amount of oxygen in milligrams that is consumed for the chemical oxidation of organic and inorganic substances contained in 1 liter of water. Increased oxidation may indicate water contamination.

Sulfates in quantities exceeding 500 mg/l give water a bitter-salty taste; at a concentration of 1000-1500 mg/l they adversely affect gastric secretion and can cause dyspepsia. Sulfates can be an indicator of contamination of surface waters by animal waste.

An increased iron content causes coloring, cloudiness, gives the water a smell of hydrogen sulfide, an unpleasant inky taste, and in combination with humic compounds - a marshy taste.

Ammonia in water is regarded as an indicator of epidemiologically dangerous fresh water pollution with organic substances of animal origin. An indicator of older contamination are salts of nitrous acid - nitrates, which are products of ammonia oxidation under the influence of microorganisms during the process of nitrification. The presence of nitrates in water without ammonia and salts of nitrous acid indicates the completion of the mineralization process and, with a high content of them in water, indicate long-standing contamination of it . However, the content of all three components in water - ammonia, nitrites and nitrates - indicates the incompleteness of the mineralization process and epidemiologically dangerous water pollution.

52. Methods for improving water quality .

I.Basic methods

1. Clarification and decolorization (purification): settling, filtration, coagulation.

2. Disinfection: boiling, chlorination, ozonation, irradiation with UV rays, the use of the oligodynamic action of silver, the use of ultrasound, the use of gamma rays.

II.Special processing methods: deodorization, degassing, deferrization, softening, desalination, defluoridation, fluoridation, decontamination.

At the first stage of water purification from an open water source, it is clarified and discolored. Clarification and decolorization refers to the removal of suspended substances and colored colloids (mainly humic substances) from water and is achieved by settling and filtration. These processes are slow and the bleaching efficiency is low. The desire to accelerate the sedimentation of suspended particles and speed up the filtration process led to preliminary coagulation of water with chemicals (coagulants) that form hydroxides with quickly settling flakes and accelerating the sedimentation of suspended particles.

Aluminum sulfate – Al2(SO4)3 – is used as coagulants; ferric chloride – FeCl3; iron sulfate - FeSO4, etc. Coagulants, when properly treated, are harmless to the body, since the residual amounts of aluminum and iron are very small (aluminum - 1.5 mg/l, iron - 0.5 - 1.0 mg/l).

After coagulation and settling, the water is filtered using fast or slow filters.

With any scheme, the final stage of water treatment at a water treatment plant should be disinfection. Its task is to destroy pathogenic microorganisms, i.e. ensuring epidemic water safety. Disinfection can be carried out by chemical and physical (reagent-free) methods.

Boiling is a simple and reliable method. Vegetative microorganisms die when heated to 800C within 20 - 40 seconds, so at the moment of boiling the water is actually disinfected.

Ultrasound is used to disinfect domestic wastewater. It is effective against all microorganisms, including spore forms, and its use does not lead to foaming when disinfecting household wastewater.

Gamma radiation is a very reliable and effective method that instantly destroys all types of microorganisms.

Reagents that do not change the chemical composition of water during disinfection include ozone.

Currently, the main method used to disinfect water at water supply stations due to technical and economic reasons is the chlorination method.

The effectiveness of water disinfection depends on the selected dose of chlorine, the time of contact of active chlorine with water, the temperature of the water and many other factors.

Modifications of chlorination include: double chlorination, chlorination with ammoniation, and rechlorination.

Conditioning the mineral composition of water can be divided into removing salts or gases from water that are in excess quantities (softening, desalting and desalination, deferrization, defluoridation, degassing, decontamination, etc.) and adding minerals in order to improve the organoleptic and physiological properties of water (fluoridation, partial mineralization after desalination, etc.).

To disinfect individual water supplies, tablet forms containing chlorine are used. Aquasept, tablets containing 4 mg of active chlorine monosodium salt of dichloroisocyanuric acid. Pantocide is a drug from the group of organic chloramines, solubility is 15-30 minutes. Releases 3 mg of active chlorine.

The value characterizing the content of organic and mineral substances in water that are oxidized by one of the strong chemical oxidizing agents under certain conditions is called oxidability. There are several types of water oxidation: permanganate, dichromate, iodate, cerium. The highest degree of oxidation is achieved by the methods of dichromate and iodate oxidation of water.

Oxidability is expressed in milligrams of oxygen used to oxidize organic substances contained in 1 dm 3 of water.

The composition of organic substances in natural waters is formed under the influence of many factors. The most important ones include intra-reservoir biochemical processes of production and transformation, receipts from other water bodies, with surface and underground runoff, with precipitation, with industrial and domestic wastewater. Organic substances formed in a reservoir and entering it from the outside are very diverse in nature and chemical properties, including resistance to the action of various oxidizing agents.

The ratio of easily and difficultly oxidized substances contained in water significantly affects the oxidability of water under the conditions of a particular method of its determination.

In surface waters, organic substances are in dissolved, suspended and colloidal states. The latter are not taken into account separately in routine analysis; therefore, the oxidation of filtered (dissolved organic matter) and unfiltered (total organic matter) samples is distinguished.

The oxidability values ​​of natural waters vary from fractions of milligrams to tens of milligrams per liter, depending on the general biological productivity of water bodies, the degree of pollution with organic substances and compounds of nutrients, as well as on the influence of organic substances of natural origin coming from swamps, peat bogs, etc. . Surface waters have a higher oxidability compared to underground waters (tenths and hundredths of a milligram per 1 dm 3), with the exception of water from oil fields and groundwater fed by swamps. Mountain rivers and lakes are characterized by oxidability of 2-3 mg O/dm 3 , lowland rivers - 5-12 mg O/dm 3 , rivers fed by swamps - tens of milligrams per 1 dm 3 .

The oxidation of unpolluted surface waters exhibits a fairly distinct physiographic zonation (Table 1).

Table 1. Physiographic zonation of natural waters

Oxidability is subject to regular seasonal fluctuations. Their character is determined, on the one hand, by the hydrological regime and the supply of organic substances from the catchment area, which depends on it, and, on the other, by the hydrobiological regime.

In bodies of water and watercourses subject to strong impacts economic activity human, the change in oxidability acts as a characteristic reflecting the regime of wastewater influx. For natural, slightly polluted waters, it is recommended to determine permanganate oxidation; in more polluted waters, dichromate oxidation (COD) is usually determined.

In accordance with the requirements for the composition and properties of water in reservoirs near drinking water use points, the COD value should not exceed 15 mg O/dm 3 ; in recreation areas in water bodies a COD value of up to 30 mg O/dm 3 is allowed.

In monitoring programs, COD is used as a measure of the amount of organic matter in a sample that is susceptible to oxidation by a strong chemical oxidizer. COD is used to characterize the state of watercourses and reservoirs, the influx of domestic and industrial wastewater (including the degree of their purification), as well as surface runoff.

Table 2. COD values ​​in water bodies with varying degrees of pollution

To calculate the concentration of carbon contained in organic matter, the COD value (mg O/dm3) is multiplied by 0.375 (a coefficient equal to the ratio of the amount of carbon equivalent substance to the amount of oxygen equivalent substance).

Biochemical oxygen demand (BOD)

The degree of water contamination with organic compounds is defined as the amount of oxygen required for their oxidation by microorganisms under aerobic conditions. Biochemical oxidation of different substances occurs at different rates. Easily oxidizing (“biologically soft”) substances include formaldehyde, lower aliphatic alcohols, phenol, furfural, etc. The middle position is occupied by cresols, naphthols, xylenols, resorcinol, pyrocatechol, anionic surfactants, etc. “biologically hard” substances, such as hydroquinone, sulfonol, nonionic surfactants, etc.

BOD 5

In laboratory conditions, along with BOD n, BOD 5 is determined - the biochemical demand for oxygen for 5 days.

In surface waters, BOD 5 values ​​usually vary within 0.5-4 mg O 2 /dm 3 and are subject to seasonal and daily fluctuations.

Seasonal variations depend mainly on changes in temperature and on the initial concentration of dissolved oxygen. The influence of temperature is reflected through its effect on the rate of consumption process, which increases 2-3 times with an increase in temperature by 10 o C. The influence of the initial oxygen concentration on the process of biochemical oxygen consumption is due to the fact that a significant part of microorganisms have their own oxygen optimum for development in in general and for physiological and biochemical activity.

Daily fluctuations in BOD 5 values ​​also depend on the initial concentration of dissolved oxygen, which can change during the day by 2.5 mg O 2 /dm 3 depending on the ratio of the intensity of the processes of its production and consumption. Changes in BOD 5 values ​​are very significant depending on the degree of pollution of water bodies.

Table 3. BOD 5 values ​​in water bodies with varying degrees of pollution

For water bodies polluted primarily by domestic wastewater, BOD 5 is usually about 70% of BOD p.

Depending on the category of the reservoir, the BOD 5 value is regulated as follows: no more than 3 mg O 2 /dm 3 for reservoirs for domestic and drinking water use and no more than 6 mg O 2 /dm 3 for reservoirs for domestic and cultural water use. For seas (categories I and II of fishery water use), the five-day oxygen demand (BOD 5) at 20 o C should not exceed 2 mg O 2 /dm 3.

The determination of BOD 5 in surface waters is used to assess the content of biochemically oxidizable organic substances, the living conditions of aquatic organisms, and as an integral indicator of water pollution. It is necessary to use BOD 5 values ​​when monitoring the efficiency of wastewater treatment plants.

BOD p

Total biochemical oxygen demand (BOD p) is the amount of oxygen required to oxidize organic impurities before the onset of nitrification processes. The amount of oxygen consumed to oxidize ammonia nitrogen to nitrites and nitrates is not taken into account when determining BOD. For domestic wastewater (without significant industrial admixtures), BOD 20 is determined, assuming that this value is close to BOD p.

The total biological oxygen demand BOD for inland fishery reservoirs (categories I and II) at 20 o C should not exceed 3 mg O 2 /dm 3.

Dissolved oxygen

Dissolved oxygen is found in natural water in the form of molecules O2. Its content in water is affected by two groups of oppositely directed processes: some increase the oxygen concentration, others reduce it. The first group of processes that enrich water with oxygen includes:

the process of absorption of oxygen from the atmosphere;

release of oxygen by aquatic vegetation during photosynthesis;

entry into reservoirs with rain and snow waters, which are usually supersaturated with oxygen.

Absorption of oxygen from the atmosphere occurs on the surface of a water body. The rate of this process increases with decreasing temperature, increasing pressure and decreasing mineralization. Aeration - the enrichment of deep layers of water with oxygen - occurs as a result of mixing of water masses, including wind, vertical temperature circulation, etc.

Photosynthetic release of oxygen occurs when carbon dioxide is assimilated by water

vegetation (attached, floating plants and phytoplankton). The process of photosynthesis proceeds more strongly, the higher the water temperature, the intensity of sunlight and the more biogenic (nutrients) substances ( P,N etc.) in water. Oxygen production occurs in the surface layer of the reservoir, the depth of which depends on the transparency of the water (for each reservoir and season it can be different, from several centimeters to several tens of meters).

The group of processes that reduce the oxygen content in water includes reactions of its consumption to the oxidation of organic substances: biological (respiration of organisms), biochemical (respiration of bacteria, oxygen consumption during the decomposition of organic substances) and chemical (oxidation Fe 2+,Mn 2+,NO 2 -,NH4+,CH 4,H2S). The rate of oxygen consumption increases with increasing temperature, the number of bacteria and other aquatic organisms and substances subject to chemical and biochemical oxidation. In addition, a decrease in the oxygen content in water can occur due to its release into the atmosphere from the surface layers and only if the water at a given temperature and pressure turns out to be supersaturated with oxygen.

In surface waters, the content of dissolved oxygen varies widely - from 0 to 14 mg/dm 3 - and is subject to seasonal and daily fluctuations. Daily fluctuations depend on the intensity of the processes of its production and consumption and can reach 2.5 mg/dm 3 of dissolved oxygen. In winter and summer, the distribution of oxygen is stratified. Oxygen deficiency is more often observed in water bodies with high concentrations of polluting organic substances and in eutrophicated water bodies containing large amounts of nutrients and humic substances.

The oxygen concentration determines the magnitude of the redox potential and, to a large extent, the direction and speed of the processes of chemical and biochemical oxidation of organic and inorganic compounds. The oxygen regime has a profound impact on the life of a reservoir. The minimum content of dissolved oxygen that ensures normal development of fish is about 5 mg/dm3. Reducing it to 2 mg/dm 3 causes mass death (killing) of fish. Oversaturation of water with oxygen as a result of photosynthesis processes with insufficient mixing of water layers also has an adverse effect on the condition of the aquatic population.

In accordance with the requirements for the composition and properties of water in reservoirs at points of drinking and sanitary water use, the content of dissolved oxygen in a sample taken before 12 noon should not be lower than 4 mg/dm 3 at any time of the year; for fishery reservoirs, the concentration of oxygen dissolved in water should not be lower than 4 mg/dm 3 in winter (during freeze-up) and 6 mg/dm 3 in summer.

The determination of oxygen in surface waters is included in observation programs to assess the living conditions of aquatic organisms, including fish, and also as an indirect characteristic of assessing the quality of surface waters and regulating the process of wastewater treatment. Dissolved oxygen content is essential for aerobic respiration and is an indicator of biological activity (i.e. photosynthesis) in a body of water.

Table 4. Oxygen content in water bodies with varying degrees of pollution

Water pollution level and quality class	Dissolved oxygen
	summer, mg/dm 3	winter, mg/dm 3	% saturation
Very clean, I
Clean, II
Moderately polluted, III
Contaminated, IV
Dirty, V
Very dirty, VI

The relative oxygen content of water, expressed as a percentage of its normal content, is called the degree of oxygen saturation. This value depends on the water temperature, atmospheric

pressure and salinity. Calculated by the formula:

M- degree of water saturation with oxygen, %;

A- oxygen concentration, mg/dm 3 ;

R- atmospheric pressure in a given area, Pa;

N- normal oxygen concentration at a given temperature, salinity (salinity) and total pressure of 101308 Pa.

Alkalinity (pH)

Alkalinity of natural or purified waters refers to the ability of some of their components to bind an equivalent amount of strong acids. Alkalinity is due to the presence of weak acid anions in water (carbonates, bicarbonates, silicates, borates, sulfites, hydrosulfites, sulfides, hydrosulfides, humic acid anions, phosphates).

Their sum is called total alkalinity. Due to the insignificant concentration of the last three ions, the total alkalinity of water is usually determined only by carbonic acid anions (carbonate alkalinity). Anions, when hydrolyzed, form hydroxide ions:

CO 3 2- + H 2 OÛ HCO 3 - + OH - ;

HCO 3 - + H 2 OÛ H 2 CO 3 + OH - .

Alkalinity is determined by the amount of strong acid required to neutralize 1 dm 3 of water. The alkalinity of most natural waters is determined only by calcium and magnesium bicarbonates, pH of these waters does not exceed 8.3.

Determination of alkalinity is useful when dosing chemicals required for water treatment for water supply, as well as for reagent treatment of some wastewater. Determination of alkalinity in excess concentrations of alkaline earth metals is important for determining the suitability of water for irrigation. Along with the values pH water alkalinity is used to calculate the carbonate content and carbonic acid balance in water.

Hydrogen value (pH)

CO 2 + H 2 0Û H + + HCO 3 -Û 2 H + + CO 3 2- .

For convenience of expressing the content of hydrogen ions, a value was introduced that is the logarithm of their concentration, taken with the opposite sign:

pH = -lg.

Surface waters containing small amounts of carbon dioxide are characterized by an alkaline reaction. Changes pH are closely related to the processes of photosynthesis (when consuming CO2 one

ions are released by vegetation HE-). Humic acids present in soils are also a source of hydrogen ions. Hydrolysis of heavy metal salts plays a role in cases where significant amounts of sulfates of iron, aluminum, copper and other metals enter the water:

Fe 2+ + 2H 2 OÞ Fe(OH) 2 + 2H + .

Meaning pH in river waters it usually varies between 6.5-8.5, in precipitation 4.6-6.1, in swamps 5.5-6.0, in sea ​​waters 7.9-8.3. The concentration of hydrogen ions is subject to seasonal fluctuations. In winter the size pH for most river waters it is 6.8-7.4, in summer 7.4-8.2. Magnitude pH natural waters is determined to some extent by the geology of the drainage basin.

In accordance with the requirements for the composition and properties of water in reservoirs near drinking water use points, water in water bodies in recreation areas, as well as water in fishery reservoirs, the pH value should not go beyond the range of 6.5-8.5.

Magnitude pH water is one of the most important indicators of water quality. The concentration of hydrogen ions is of great importance for the chemical and biological processes occurring in natural waters. From size pH depends on the development and vital activity of aquatic plants, the stability of various forms of migration of elements, and the aggressive effect of water on metals and concrete. Magnitude pH water also affects the processes of transformation of various forms of nutrients and changes the toxicity of pollutants.

In a reservoir, several stages of the acidification process can be distinguished. At the first stage pH practically does not change (bicarbonate ions manage to completely neutralize ions H+). This continues until the total alkalinity in the reservoir drops by about 10 times to a value of less than 0.1 mol/dm 3.

At the second stage of reservoir acidification pH water usually does not rise above 5.5 throughout the year. Such reservoirs are said to be moderately acidic. At this stage of acidification, significant changes occur in the species composition of living organisms.

At the third stage of reservoir acidification pH stabilizes at values pH<5 (обычноpH 4.5), even if precipitation has higher values pH. This is due to the presence of humic substances and aluminum compounds in the reservoir and soil layer.

Depending on pH, natural waters can be rationally divided into seven groups (Table 3.3).

Table 5. Groups of natural waters depending on pH

Group		Note
Strongly acidic waters		the result of hydrolysis of heavy metal salts (mine and mine waters)
Acidic waters		the entry of carbonic acid, fulvic acids and other organic acids into water as a result of the decomposition of organic substances
Slightly acidic waters		the presence of humic acids in soil and swamp waters (waters of the forest zone)
Neutral waters		presence in waters Ca(HCO 3) 2, Mg(HCO 3) 2
Slightly alkaline waters		presence in waters Ca(HCO 3) 2,Mg(HCO 3) 2
Alkaline waters		presence Na 2 CO 3 or NaHCO3
Highly alkaline waters		presence Na 2 CO 3 or NaHCO3

Suspended substances (coarse impurities) explosives

Suspended solids present in natural waters consist of particles of clay, sand, silt, suspended organic and inorganic substances, plankton and various microorganisms. The concentration of suspended particles is associated with seasonal factors and flow regime, depends on the rocks composing the riverbed, as well as on anthropogenic factors such as agriculture, mining, etc.

Suspended particles affect water clarity and light penetration, temperature, dissolved composition of surface waters, adsorption of toxic substances, as well as the composition and distribution of sediments and the rate of sedimentation. Water containing a lot of suspended particles is not suitable for recreational use for aesthetic reasons.

In accordance with the requirements for the composition and properties of water in water bodies at points of economic, drinking and cultural purposes, the content of suspended substances as a result of wastewater discharge should not increase, respectively, by more than 0.25 mg/dm 3 and 0.75 mg/ dm 3. For reservoirs containing more than 30 mg/dm3 of natural mineral substances during low-water periods, an increase in the concentration of suspended substances within 5% is allowed.

Determining the amount of suspended particles is important when monitoring the processes of biological and physicochemical treatment of wastewater and when assessing the condition of natural reservoirs.

Coarse impurities are determined by the gravimetric method after their separation by filtration through a “blue ribbon” filter (mainly for samples with transparency less than 10 cm).