Indicators of pollution by organic indicators of water. Interpretation of water analysis indicators
DIRECT CYCLE OF DECOMPOSITION OF NITROGEN-CONTAINING ORGANIC COMPOUNDS
It is represented by undecomposed substances of a protein nature, 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 to nitric acid (NO 3 -) (nitrates).
With fresh pollution with waste in the water, the content AMMONIUM SALTS, that is, the ammonium ion is 1. 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 water should not exceed 0.002 mg/l).
NITRATE- this is the end product of the oxidation of ammonium compounds, the presence in water in the absence of ammonium ions and nitrites indicates old pollution water source. The content of nitrates in the water of mine wells should be 10 mg / l in drinking water of centralized water supply up to 45 mg / l).
The detection of the simultaneous presence of ammonium salts, nitrites and nitrates in water indicates a constant and long-term organic pollution of water.
Chlorides- have an exceptionally wide distribution in nature and are found in all natural waters. A large number of them in the water makes it undrinkable due to the salty taste. In addition, chlorides can serve as an indicator of possible pollution of a water source by sewage, so chlorides as sanitary indicative substances can be important if analyzes for their content are carried out repeatedly, for a more or less long time. (GOST "Drinking water is not >> 350 mg/l).
SULFATES- are also important indicators of organic water pollution, as they are always contained in domestic 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
Groundwater, due to the lack of contact with air, very often does not contain oxygen. The degree of saturation of surface waters varies greatly. Water is considered clean if it contains 90% of oxygen from the maximum possible 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 in any period of the year should 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 amount of oxygen consumption during some period of storage of water at a certain temperature (BIOCHEMICAL OXYGEN DEMAND 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 is determined in it and left for 5 or 20 days at a temperature of 20 0 C. After that, the oxygen content is again determined. The most common indicator BOD 5 is used to characterize the processes of self-purification of water bodies from pollution by industrial and domestic wastewater.
MAIN SOURCES OF WATER POLLUTION, CONSEQUENCES OF WATER POLLUTION
The main sources of water pollution are:
1. industrial and domestic wastewater (domestic water has a 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 sewerage) and unorganized surface runoff from the territory of settlements, agricultural fields (use of various chemicals - mineral fertilizers, pesticides, etc.)
5. mole rafting of wood;
6. water transport (waste water of 3 types: fecal, household and water obtained in engine rooms).
In addition, additional sources of water contamination by causative agents of intestinal infections can be: wastewater from hospitals; 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 a change in the organoleptic characteristics 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), helminthiases, as well as human infection with protozoa (amoeba, infusoria shoe);
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 should be epidemiologically safe in relation to acute infectious diseases;
2. must be harmless in terms of chemical composition;
3. Water should have favorable organoleptic characteristics, should be pleasant to the taste, should not cause aesthetic rejection.
To reduce human morbidity associated with the water transmission factor, it is necessary:
implementation of the environmental complex of measures (enterprises sources of pollution) and control over its implementation (supervisory bodies of the Ministry of Natural Economy, Federal Service "Rospotrebnadzor");
application of methods for improving the quality of drinking water (vodokanal);
drinking water quality control.
Natural water has a slightly alkaline reaction (6.0-9.0). An increase in alkalinity indicates pollution or blooming of the reservoir. The acidic reaction of water is noted in the presence of humic substances or the penetration of industrial wastewater.
Rigidity. The hardness of water depends on the chemical composition of the soil through which the water passes, the content of carbon monoxide in it, and the degree of contamination with organic substances. It is measured either in mg-eq / l, or in degrees. According to the degree of hardness, water is: soft (up to 3 mg-eq / l); medium hardness (7mg=eq/L); hard (14mg=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 oxidizability of water is the amount of oxygen in milligrams that is spent on the chemical oxidation of organic and inorganic substances contained in 1 liter of water. Increased oxidizability may indicate water pollution.
Sulfates in amounts exceeding 500 mg/l give the water a bitter-salty taste, at a concentration of 1000-1500 mg/l adversely affect gastric secretion and can cause dyspepsia. Sulphates can be an indicator of pollution of surface waters by animal waste.
The increased content of iron causes coloring, turbidity, gives the water the smell of hydrogen sulfide, an unpleasant inky taste, and in combination with ms humic compounds - a swampy 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 pollution are salts of nitrous acid - nitrates, which are the products of ammonia oxidation under the influence of microorganisms in the process of nitrification. . 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. Lightening and bleaching (cleaning): sedimentation, 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 treatment methods: deodorization, degassing, iron removal, softening, desalination, defluorination, fluorination, decontamination.
At the first stage of water purification from an open water source, it is clarified and discolored. Under clarification and discoloration is meant the removal of suspended solids and colored colloids (mainly humic substances) from water and is achieved by sedimentation, filtration. These processes are slow and the bleaching efficiency is low. The desire to accelerate the settling of suspended particles, to speed up the filtration process led to the preliminary coagulation of water with chemicals (coagulants) that form hydroxides with rapidly settling flakes and accelerate the settling of suspended particles.
Aluminum sulphate - Al2(SO4)3 is used as coagulants; ferric chloride - FeCl3; ferrous sulphate - FeSO4, etc. Coagulants with properly performed water treatment 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 on fast or slow filters.
With any scheme, the final stage of water treatment at the water treatment plant should be disinfection. Its task is the destruction of pathogenic microorganisms, i.e. ensuring epidemic water safety. Disinfection can be carried out by chemical and physical (reagentless) methods.
Boiling is a simple and reliable method. Vegetative microorganisms die when heated to 800C in 20-40 seconds, therefore, 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 domestic wastewater.
Gamma radiation is a very reliable and effective method that instantly destroys all types of microorganisms.
Ozone is one of the reagents that do not change the chemical composition of water during disinfection.
Currently, the main method used for water disinfection at waterworks due to technical and economic reasons is the chlorination method.
The effectiveness of water disinfection depends on the selected dose of chlorine, the contact time of active chlorine with water, water temperature and many other factors.
Modifications of chlorination include: double chlorination, chlorination with ammoniation, rechlorination.
The conditioning of the mineral composition of water can be divided into the removal of excess salts or gases from the water (softening, desalination and desalination, iron removal, defluorination, degassing, decontamination, etc.) and the addition of mineral substances in order to improve the organoleptic and physiological properties of water (fluorination, partial mineralization after desalination, etc.).
For the disinfection of individual water supplies, tablet forms containing chlorine are used. Aquasept, tablets containing 4 mg of active chlorine monosodium salt of dichloroisocyanuric acid. Pantocid is a preparation from the group of organic chloramines, solubility is 15-30 minutes. It releases 3 mg of active chlorine.
presence of organic matter in the water. The amount of dissolved oxygen depends on the temperature of the water. The lower the temperature o, the more dissolved oxygen in the water. In addition, the oxygen content depends on the presence of zoo- and phytoplankton in the water. If there are a lot of algae or a lot of animals in the water, then the oxygen content is less, since part of the oxygen is spent on the vital activity of zoo - and phytoplankton. The oxygen content also depends on the surface of the reservoir: there is more oxygen in open reservoirs. The oxygen content under all other conditions will depend on the barometric pressure and on pollution. The greater the pollution, the less oxygen is contained in the water, because oxygen will be spent on the oxidation of pollution (organic substances). In order to judge whether there is enough or not enough oxygen in a reservoir, there are Windler tables, which provide data on the limit of oxygen solubility at a given temperature. If we determine the amount of dissolved oxygen in our water sample and find that at 7 degrees we have 9 mg of oxygen in our sample, then these numbers do not give anything. We have to look at Windler's table: at 7 degrees, 11 mg should be dissolved. Oxygen per liter and this suggests that, apparently, the water contains a large amount of organic matter
Indicator of biochemical oxygen demand (BOD). BOD is the amount of oxygen that is necessary for the oxidation of easily oxidized organic substances in 1 liter of water. Conditions for this analysis: exposure 1 day, 5 days, twenty days. Technique: it takes time and a dark place: two jars are taken, filled with the investigated water. In the first jar, the oxygen content is determined immediately, and the second jar is placed either for a day, or for 5, or for 20 in a dark room and the oxygen content is determined. The more organic substances are contained in the water sample, the less oxygen will be detected, because part of the dissolved oxygen will be spent on the oxidation of organic substances (easily oxidized).
The oxidizability of water is the amount of oxygen that is necessary for the oxidation of easily and moderately oxidizable organic substances found in 1 liter of water. Conditions: oxidizing agent - potassium permanganate, 10 minute boiling. Not always a high oxidizability figure indicates a problem with the water source. A high oxidizability figure may be due to plant organic matter. For example, the water of Lake Ladoga and, in general, the water of northern reservoirs contains a greater amount of organic matter of plant origin and the oxidizability of our waters is quite high, but this does not mean that the water is harmful or polluted. In addition, a high oxidizability figure may be due to the presence of inorganic substances in water - strong reducing agents, which is typical for groundwater. These include sulfides, sulfites, ferrous oxide salts. Nitrites. A high oxidizability figure may be due to the presence of organic matter of animal origin in the water, and only in this case we say that the reservoir is polluted. Naturally, the question arises, how can we decide due to what we have a high oxidizability figure. To answer this question, there are the following methods: in order to differentiate oxidizability due to organic substances from oxidizability due to inorganic substances, you need to put a sample in the cold: inorganic substances (mineral) are oxidized in the cold. Suppose we had an oxidizability of 8 mg/l, put a sample in the cold, found out that the oxidizability in the cold is 1 mg/l. It turns out that due to organic substances 7 mg / l are accounted for. Now we must differentiate vegetable organics from animal origin. In this case, you need to look at bacteriological indicators. GOST does not standardize oxidizability, since it can be high both in normal and polluted water. However, there are guidelines. Indicative norms are as follows: for surface water bodies - 6-8 mg / l. For underground water sources, for mine wells 4 mg/l, for artesian waters 1-2 mg/l.
COD is also an indicator of the presence of organic matter in water - chemical oxygen demand. This is the amount of oxygen that is necessary for the oxidation of easily, moderately and difficultly oxidized organic substances in 1 liter of water. Analysis conditions: potassium dichromate as an oxidizing agent, concentrated sulfuric acid, two-hour boiling. In any water, if analyzed correctly, the BOD will always be less than the oxidizability, and the oxidizability will always be less than the COD. The determination of COD, BOD and oxidizability is important for predicting the wastewater treatment system. If we take the wastewater - the household and fecal wastewater of our city and the wastewater of the pulp and paper mill, and determine these 3 factors, you will get that in the household and fecal wastewater, the bulk is made up of easily oxidized chemicals, therefore, a biological method must be used for cleaning. In the effluents of the pulp and paper mill, there are significantly more medium- and difficult-to-oxidize substances, therefore, it is necessary to use chemical treatment.
The study of organic carbon is an indicator for the presence of organic substances in water. The more organic carbon found, the more organics in the water. There are indicative standards for organic carbon. It is considered that if it is present in the range of 1-10 mg / l, this reservoir is clean, More than 100 - polluted.
CCE - carbo-chloroform extract. This indicator allows you to determine the presence in the water of difficult-to-detect substances: petroleum products, pesticides, surfactants. All these substances are adsorbed on carbon and then extracted. It is believed that if CCE is within 0.15 - 0.16, then this reservoir is clean, 10 or more - the reservoir is polluted.
Determination of chlorides and sulfates. Chlorides give a salty taste, sulfates give a bitter taste. Chlorides should not exceed 250 mg/l, and sulfates should not exceed 500 mg/l. Most often, chlorides and sulfates in water are of mineral origin, which is associated with soil composition, but in some cases, chlorides and sulfates can be indicators of pollution when they enter water bodies as pollution with sewage baths, etc. If the content of these substances changes in dynamics, then, of course, there is pollution of the water source.
dry residue. If you take 1 liter of water and evaporate, weigh the remainder, you will get the weight of the dry residue. The more mineralized water, the greater this dry residue will be. According to GOST, the dry residue should not exceed 1000 mg/l. Loss on ignition makes it possible to judge the amount of organic matter in the residue (this is how organic substances burn out). The greater the loss on ignition, the more organic substances are contained in the water. In pure water, losses on ignition should not exceed 1/3 of the dry residue, that is, 333 mg.
All these indicators are indirect, since they do not allow themselves to determine those substances that caused pollution. More direct are bacteriological indicators - the index and titer of bacteria of the Escherichia coli group.
Cleaning technologies
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Traditionally, water quality indicators are divided into physical (temperature, color, taste, smell, turbidity, etc.), chemical (water pH, alkalinity, hardness, oxidizability, total mineralization (dry residue), etc.) and sanitary-bacteriological (general bacterial contamination of water, coli-index, content of toxic and radioactive components in water, etc.).
To determine how water meets the required standards, numerical values of water quality indicators are documented, with which the measured indicators are compared.
The normative and technical literature that makes up the water and sanitary legislation imposes specific requirements on the quality of water, 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 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 water meets the requirements of sanitary norms and rules.
Let us consider in detail the parameters by which water quality is assessed.
Physical indicators of water quality
Water temperature surface sources is determined by air temperature, its humidity, speed and nature of water movement (as well as a number of other factors). Depending on the season, it can undergo significant changes (from 0.1 to 30º C). For underground sources, the water temperature is more stable (8-12 ºС).
The optimum water temperature for drinking purposes is 7-11 ºС.
It should be noted that this water parameter is of great importance for some industries (for example, for cooling systems and steam condensation).
Turbidity- an indicator of the content of various suspended solids in water (mineral origin - particles of clay, sand, silt; inorganic origin - carbonates of various metals, iron hydroxide; organic origin - plankton, algae, etc.). The ingress of suspended solids into the water occurs due to the erosion of the banks and the bottom of the river, their entry with melt, rain and waste water.
Underground sources have, as a rule, a slight turbidity of water due to the presence of a suspension of iron hydroxide in it. For surface waters, turbidity is more often caused by the presence of zoo- and phytoplankton, silt or clay particles; its value fluctuates throughout the year.
The turbidity of water is usually expressed in milligrams per liter (mg/L); its value for drinking water according to SanPiN 2.1.4.559-96 should not exceed 1.5 mg/l. For a number of food, medical, chemical, electronic industries, water of the same or higher quality is used. At the same time, in many production processes, the use of water with a high content of suspended solids is acceptable.
Water color- an indicator characterizing the intensity of water color. It is measured in degrees on the platinum-cobalt scale, while the studied water sample is compared in color with reference solutions. The color of water is determined by the presence in it of impurities of both organic and inorganic nature. This characteristic is strongly affected by the presence in the water of organic substances washed out of the soil (humic and fulvic acids, mainly); iron and other metals; technogenic pollution from industrial wastewater. The requirement of SanPiN 2.1.4.559-96 - the color of drinking water should not exceed 20º. Certain types of industry are tightening the requirements for the value of water color.
Smell and taste of water- this characteristic is determined organoleptically (with the help of the senses), so it is quite subjective.
The smells and taste that water can have appear due to the presence of dissolved gases, organic substances, mineral salts, and chemical man-made pollution in it. The intensity of odors and tastes are determined on a five-point scale or according to the “dilution threshold” of the tested water sample with distilled water. This sets the dilution ratio necessary for the disappearance of the smell or taste. 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 and smell of more than 2 points (requirements of GOST 2874-82).
In accordance with a 5-point scale: at 0 points - smell and taste are not detected;
at 1 point, the water has a very slight smell 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 smell or taste is easily detected (which is the reason for complaints about water quality);
at 4 points, there is a distinct smell or taste that can make you refrain from drinking water;
at 5 points, the water has such a strong smell or taste that it becomes completely undrinkable.
The taste of water is due to the presence of dissolved substances in it, giving it a certain taste, which can be brackish, bitter, sweetish and sour. Natural waters have, as a rule, only a brackish and bitter taste. Moreover, a salty taste appears in water containing sodium chloride, and a bitter taste gives an excess of magnesium sulfate. Water with a large amount of dissolved carbon dioxide (so-called mineral waters) tastes sour. Water with an inky or ferrous taste is saturated with iron and manganese salts; astringent taste gives it calcium sulfate, potassium permanganate; alkaline taste is caused by the content of soda, potash, alkali in water. The taste can be of natural origin (the presence of manganese, iron, methane, hydrogen sulfide, etc.) and artificial origin (when industrial waste is discharged). SanPiN 2.1.4.559-9 requirements for drinking water - taste no more than 2 points.
Various living and dead organisms, plant residues, specific substances secreted by some algae and microorganisms, as well as the presence of dissolved gases in the water, such as chlorine, ammonia, hydrogen sulfide, mercaptans, or organic and organochlorine contaminants, give odors to water. Smells are natural (natural) and artificial origin. The former include such odors as woody, aromatic, earthy, marsh, moldy, putrefactive, herbaceous, fishy, indefinite and hydrogen sulfide, etc. Smells of artificial origin get their name from the substances that define them: camphor, phenolic, chlorine, resinous, pharmaceutical, chlorine phenolic, smell of petroleum products, etc.
SanPiN 2.1.4.559-9 requirements for drinking water - smell no more than 2 points.
Chemical indicators of water quality
General mineralization(dry residue). General mineralization - a quantitative indicator of substances dissolved in 1 liter of water (inorganic salts, organic substances - except for gases). This indicator is also called the total salt content. Its characteristic is the dry residue obtained by evaporating the filtered water and drying the retained residue to constant weight. Russian standards allow mineralization of water used for domestic and drinking purposes, not 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 it is characterized, pH is used - 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 an equal amount 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. Norms SanPiN 2.1.4.559-96 require that the pH value of drinking water be in the range of 6.0 ... 9.0. Most natural sources have a pH value within these limits. However, it can cause a significant change in the pH value. The correct assessment of water quality and the exact choice of the method of its purification requires knowledge of the pH of the water sources in different periods of the year. Water with low pH values is highly corrosive to steel and concrete.
Water quality is often described in terms of hardness. Requirements for water quality in terms of hardness in Russia and Europe are very different: 7 mg-eq/l (according to Russian standards) and 1 mg-eq/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 general water hardness.
Carbonate hardness (removable) is an indicator of the presence of calcium and magnesium bicarbonate in water. When water is boiled, it decomposes with the formation of sparingly soluble salts and carbon dioxide.
Non-carbonate or permanent hardness is determined by the content of non-carbonate calcium and magnesium salts in water - sulfates, chlorides, nitrates. When boiling water, they do not precipitate and remain in solution.
General hardness - the total value of the content of calcium and magnesium salts in water; is the sum of carbonate and non-carbonate hardness.
Depending on the hardness value, water is characterized as:
The amount of water hardness varies greatly depending on what types of rocks and soils make up the catchment area; on weather conditions and the season of the year. So, in surface sources, water, as a rule, is relatively soft (3 ... 6 mg-eq / l) and depends on the location - the further south, the higher the hardness of the water. The hardness of groundwater varies depending on the depth and location of the aquifer and the amount of annual precipitation. In a limestone layer, water hardness is usually 6 meq/l or more.
Drinking water hardness (according to SanPiN 2.1.4.559-96) should not exceed 7.0 mg-eq/l.
Hard water due to excess calcium has an unpleasant taste. The danger of constant use of water with increased hardness is a decrease in gastric motility, the accumulation of salts in the body, the risk of joint disease (arthritis, polyarthritis) and the formation of stones in the kidneys and bile ducts. True, very soft water is also not useful. Soft water, which has great activity, is able to wash calcium out of the bones, which leads to their fragility; development of rickets in children. Another unpleasant property of soft water is its ability to wash out beneficial organic substances, including beneficial bacteria, as it passes through the digestive tract. The best option is water with a hardness of 1.5-2 mg-eq / l.
It is already well known 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 a precipitate of calcium and magnesium salts of fatty acids during domestic use of hard water leads to a significant increase in the consumption of detergents and slows down the cooking process, which is problematic for the food industry. In some cases, the use of hard water for industrial purposes (in the textile and paper industry, at artificial fiber enterprises, for feeding 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.). The deposition of hardness salts (Ca and Mg bicarbonates) on the inner walls of pipes, scale deposits in water heating and cooling systems reduce the flow area, reduce heat transfer. It is not allowed to use water with high carbonate hardness in circulating water supply systems.
Alkalinity of water. The total alkalinity of water is the sum of the hydrates and anions of weak acids (silicic, carbonic, phosphoric, etc.) contained in it. When characterizing groundwater, in the overwhelming majority of cases, hydrocarbon 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 in order to control the quality of drinking water; to determine the suitability of water for irrigation; to calculate the content of carbonates, for subsequent wastewater treatment.
MPC for alkalinity 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 (common salt), a very common salt on Earth, from rocks. A significant amount of sodium chloride is found in sea water, as well as in the water of some lakes and underground sources.
Depending on the standard, MPC for 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 are present in groundwater, as a result of the dissolution of gypsum present in the layers. With an excess of sulfates in water, a person develops an upset gastrointestinal tract (these salts have a laxative effect).
MPC for sulfates in drinking water is 500 mg/l.
Content silicic acids. Silicic acids of various forms (from colloidal to ion-dispersed) are found in water from underground and surface sources. Silicon has a low solubility and its content in water is usually low. Silicon also enters water with industrial effluents from enterprises engaged in the production of ceramics, cement, glass products, and silicate paints.
MPC 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 pollution by industrial effluents or effluents from agricultural fields. With an increased content of phosphates, blue-green algae develop intensively, releasing toxins into the water when they die.
MPC of phosphorus compounds in drinking water - 3.5 mg/l.
Fluorides and iodides. Fluorides and iodides have some similarities. The lack or excess of these elements in the human body leads to serious diseases. For example, a lack (excess) of iodine provokes thyroid disease ("goiter"), which develops when the daily iodine ration is less than 0.003 mg or more than 0.01 mg. Fluorides are contained in minerals - fluorine salts. The content of fluorine in drinking water to maintain human health should be in the range of 0.7 - 1.5 mg/l (depending on the climate).
Surface sources have mainly low fluorine content (0.3-0.4 mg/l). The content of fluorine in surface waters increases as a result of the discharge of industrial fluorine-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 his daily diet. Usually the content of fluorine in the daily diet is from 0.54 to 1.6 mg of fluorine (averaged - 0.81 mg). It should be noted that 4-6 times less fluorine enters the human body with food than with drinking water, which has an optimal content (1 mg/l).
With an increased content of fluorine in water (more than 1.5 mg / l), there is a danger of developing endemic fluorosis (the so-called "spotted tooth enamel"), rickets and anemia in the population. These diseases are accompanied by characteristic damage to the teeth, a violation of the processes of ossification of the skeleton, and exhaustion of the body. Therefore, the content of fluorine 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 fluorine content of less than 0.5 mg / l, dental caries develops, therefore, in such cases, doctors recommend using fluoride-containing toothpaste. Fluorine is better absorbed by the body from water. Based on the foregoing, the optimal dose of fluoride in drinking water is 0.7...1.2 mg/l.
MPC for fluorine - 1.5 mg/l.
Oxidability permanganate is a parameter determined by the presence of organic substances in water; in part, it can signal the contamination of the source with sewage. Depending on which oxidizer is used , permanganate oxidizability and bichromate oxidizability (or COD - chemical oxygen demand) differ. Permanganate oxidizability is a characteristic of the content of easily oxidizable organics, bichromate - the total content of organic substances in water. The quantitative value of these indicators and their ratio allows one to indirectly judge the nature of organic substances present in the water, as well as the methods and efficiency of water purification.
According to the requirements of SanPiN: the value of permanganate oxidizability of water should not exceed 5.0 mg O 2 /l. Water with a permanganate oxidizability of less than 5 mg O 2 /l is considered clean, more than 5 mg O 2 /l is dirty.
In a 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 settling or heating, the water becomes yellowish-brown;
In undissolved form (trivalent iron Fe3 +) is found in surface water sources. The water is clear - with a 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 a suspended state, do not precipitate even with prolonged settling;
In the form of the so-called iron-organics - iron salts and humic and fulvic acids. The water is clear, yellowish-brown;
Iron bacteria that form brown slime on water pipes.
The content of iron in the surface waters of central Russia is from 0.1 to 1.0 mg / dm 3 of iron; in groundwater this value reaches 15-20 mg/dm 3 and more. It is important to analyze the iron content in wastewater. Wastewater from metalworking, metallurgical, paint and varnish industries, textile, as well as agricultural effluents especially "clog" water bodies with iron. The concentration of iron in water is affected by the pH value and the oxygen content in the water. In well and borehole water, iron can be in oxidized and reduced form, however, when water settles, it always oxidizes and can precipitate.
SanPiN 2.1.4.559-96 allow a total iron content of not more than 0.3 mg/l.
It is believed that iron is not toxic to the human body, but with prolonged use of water with an excess content of iron, its compounds can be deposited in human tissues and organs. Water contaminated with iron has an unpleasant taste and brings inconvenience to everyday life. In a number of industrial plants that use water to wash the product during its manufacture, for example, in the textile industry, even a small amount of iron in the water significantly reduces the quality of the product.
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 a slowdown in growth and development, a violation of mineral metabolism, and the development of anemia. A person suffers from both a lack and an excess of manganese.
Norms SanPiN 2.1.4.559-96 allow the content of manganese in drinking water not more than 0.1 mg/l.
An excess of manganese in water can cause a disease 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 products of their vital activity in pipes and heat exchangers cause a decrease in their cross section, sometimes even complete blockage. Water used in the food, textile, plastics, etc. industries must contain a strictly limited amount of iron and manganese.
Also, an excess of manganese leads to staining of linen during washing, the formation of black spots on plumbing and dishes.
Sodium and potassium- the entry of these elements into groundwater occurs in the process of dissolution of bedrock. The main source of sodium in natural waters is the deposits of table salt NaCl, which arose in the places where the ancient seas were located. Potassium is less common in waters due to its uptake 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 perform the task of activating enzymatic metabolism in the human body.
According to SanPiN 2.1.4.559-96 MPC sodium - 200 mg/l. Excess sodium in water and food provokes the development of hypertension and hypertension in humans.
Potassium promotes increased excretion 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. A lack of potassium in the body leads to dysfunctions of the neuromuscular (paralysis and paresis) and cardiovascular systems and contributes to depression, incoordination of movements, muscle hypotension, convulsions, arterial hypotension, ECG changes, 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 effluents. An increase in the content of copper and zinc can 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 the norms of SanPiN, the MPC of 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 deformity, and hypertension. An excess of this element provokes and enhances the deficiency of Se and Zn. Symptoms of cadmium poisoning are damage to the central nervous system, protein in the urine, acute bone pain, dysfunction of the genital organs. All chemical forms of cadmium are hazardous.
Aluminum- light metal of silver-white color. First of all, it enters the water in the process of water treatment - in the composition of coagulants and when discharging wastewater from bauxite processing.
In water, the MPC of aluminum salts is 0.5 mg/l.
With 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 stays dissolved in water. 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 impair the quality of drinking water, while at the same time contributing to the growth of metal corrosion. An increase in water temperature, as well as its mobility, enhances 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 It tends to give water a characteristic unpleasant odor and cause 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 are nitrites NO 2 -, nitrates NO 3 - and ammonium salts NH 4 + , almost always present in all waters, including groundwater. Their presence indicates that there are organic substances of animal origin in the water. These substances are formed as a result of the breakdown of organic impurities, mainly urea and proteins, which enter the water with domestic wastewater. The considered group of ions is in close relationship.
The first decay product ammonia (ammonium nitrogen), is formed as a result of the breakdown of proteins and is an indicator of fresh faecal 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 faecal contamination of water, especially if the content of ammonia and nitrites is increased at the same time. Nitrates-indicator of older organic fecal water pollution. The content of nitrates together with ammonia and nitrites is unacceptable.
Thus, the presence, quantity and ratio of nitrogen-containing compounds in water makes it possible to judge how much and 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, it can be concluded that the reservoir has been polluted for a long time, and during this time the water has self-purified. If ammonia is present in the reservoir and there are no nitrates, then water pollution with organic substances has happened recently. Drinking water should not contain ammonia and nitrites.
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 the water exceeds the background values, then the pollution has occurred recently, and the source of pollution is close. These can be livestock farms, municipal sewage treatment plants, accumulations of nitrogen fertilizers, manure, settlements, industrial waste lagoons, etc.
When drinking water with a high content of nitrates and nitrites, the oxidative function of the blood is disturbed in humans.
Chlorine introduced into drinking water when it is. Chlorine exhibits a disinfecting effect by oxidizing or chlorinating (replacing) the molecules of substances that make up the cytoplasm of bacterial cells, as a result of which the bacteria die. The pathogens of dysentery, typhoid, cholera and paratyphoid are extremely sensitive to chlorine. Relatively small doses of chlorine disinfect even heavily contaminated water. However, complete sterilization of water does not occur due to the viability of individual chlorine-resistant individuals.
free chlorine- a substance harmful to human health, therefore, in the drinking water of centralized water supply, SanPiN hygiene standards strictly regulate the content of residual free chlorine. SanPiN establishes the upper and minimum allowable limits for the content of free residual chlorine. The problem is that although water is disinfected at a 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 contamination enters the main water.
Therefore, the norms SanPiN 2.1.4.559-96 provide for the content of residual chlorine in tap water not less than 0.3 mg/l and not more than 0.5 mg/l.
Chlorine is toxic and highly allergic, so chlorinated water has an adverse effect on the skin and mucous membranes. These are redness of various parts of the skin, and manifestations of allergic conjunctivitis (swelling of the eyelids, burning, tearing, pain in the eye area). Chlorine also adversely affects the respiratory system: as a result of being 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, tetrachloethylene, trichloroethane. 70 - 90% of the chlorine-containing substances formed during water treatment is chloroform. Chloroform contributes to professional chronic poisoning with a primary lesion of 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 oncology. Thus, American experts believe that chlorine-containing substances in drinking water are indirectly or directly responsible for 20 cancers per 1 million inhabitants.
hydrogen sulfide found in groundwater and is predominantly inorganic in origin.
In nature, this gas is constantly formed during the decomposition of protein substances. It has a characteristic unpleasant odor; provokes corrosion of 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 should be noted that SanPiN 2.1.4.559-96 allows the presence of hydrogen sulfide in water up to 0.003 mg/l. The question is - is this a typo in a regulatory document ?!
Microbiological indicators. Total microbial count(MCH) is determined by the number of bacteria contained in 1 ml of water. According to the requirements of GOST, drinking water should not contain more than 100 bacteria per 1 ml.
The number of bacteria of the Escherichia coli group is of particular importance for the sanitary assessment of water. The presence of Escherichia coli in the water is evidence of its contamination with fecal effluents and, as a result, the risk of pathogenic bacteria entering it. Determining the presence of pathogenic bacteria in the 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 37ºС, and Escherichia coli - coli bacteria. The presence of the latter indicates water pollution by excretions of people, animals, etc. The minimum volume of water to be tested, ml, per one E. coli, is called colititer, and the number of E. coli in 1 liter of water is called the coli index. According to GOST 2874-82, if the index is up to 3, the colititer is at least 300, and the total number of bacteria in 1 ml is up to 100.
According to SanPiN 2.1.4.559-96, a total microbial count of 50 CFU / ml is permissible, common coliform bacteria(OKB) CFU/100ml and thermotoletic coliform bacteria(TCB) CFU/100ml - not allowed.
Pathogenic bacteria and viruses in the water can cause diseases such as dysentery, typhoid fever, paraphytosis, amoebiasis, cholera, diarrhea, brucellosis, infectious hepatitis, tuberculosis, acute gastroenteritis, anthrax, poliomyelitis, tularemia, etc.
Company Waterman offers you a professional solution to the problem of water purification from compounds, the content of which in water is higher than the standard. Our specialists will advise on the issues that have arisen and help in the selection and implementation of the optimal water treatment scheme, based on specific initial data.
Toxic emissions into the environment are so massive that pollution of water sources has become natural. Harmful substances from industrial enterprises, agricultural waste, organic compounds, household waste penetrate into water bodies. Indicators of water pollution make it possible to judge the nature and extent of the danger threatening humanity, wildlife and the environment as a whole.
Chemical and bacteriological indicators
Chemical and bacteriological quantities are used to assess the quality of water resources. In sanitary practice, the first group includes:
- BOD. biological oxygen demand.
- COD. Chemical oxygen demand.
- The amount of dissolved oxygen.
- Oxidability.
COD in this list is the main value by which the quality of the liquid is determined. COD is indicated in milligrams of oxygen spent on the oxidation of organic substances in 1 dm 3 of water. According to sanitary standards, it should not exceed 8 mg O / dm 3.
Bacteriological indicators include:
- Microbial number (the number of colonies in 1 ml of liquid).
- Coli-titer (the smallest volume of liquid in which 1 Escherichia coli is found).
- Coli index (an indicator of the number of rod-shaped bacteria in 1 liter).
The microbial number indicates the contamination of the water source with saprophytes. The lower the percentage in the sample, the safer the water in epidemiological terms.
Particular attention is paid to the detection of E. coli excreted by human and animal feces. Fresh fecal contamination is determined by the presence and count of all representatives of the microorganism in the water. Gram-negative bacteria of this type provoke various diseases and infections. Through the analysis of water sources, infection with pathogenic microorganisms can be prevented.
organic pollution
Chemical indicators of water pollution by organic substances - nitrogen-containing components. They judge the quality of the resource. Nitrates and ammonia are a sign of periodic discharge of waste into a water source, nitrites - a source of contamination appeared relatively recently.
The root cause of contamination with organic substances are the corpses of animals, organic compounds in the composition of the soil, waste disposal of industrial sites, detergents, factory effluents.
Drinking water quality
According to WHO, drinking water contains 13,000 potentially hazardous substances. Among them are salts of heavy metals, organic residues, pesticides. Pollution of drinking water provokes 80% of diseases from which 25 million people die every year. There is only 1% of water left on the planet that can be consumed without prior purification, and humanity itself is to blame for this. According to the UN organization UNICEF and WHO, 800 million people on Earth (of which 40% are Africans) still use polluted water sources.
