Escherichia coli (Escherichia coli) is the very first sanitary-indicative microorganism that has retained its significance to this day. Back in 1888, the French physician E. Mase suggested using this bacterium as an indicator of fecal water pollution. The third edition of the WHO Guidelines for the Monitoring of Drinking Water Quality recommends the E. coli index (index) as the index of choice for assessing fresh faecal contamination. As an alternative indicator of faecal contamination (under certain circumstances), the indicator Thermotolerant Coliform Bacteria (TCB) (index) is recommended. The indicator Coliform bacteria (CB) is recommended as a technological indicator for assessing the quality of water treatment (indicator). According to the domestic regulatory framework, Coliform Bacteria (CB) in WHO terminology correspond to the indicator of Total Coliform Bacteria (TCB).
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The membrane seeding method is widely used to determine coliform parameters, although the titration method is no less important. Methods for determining these indicators vary greatly depending on the object under study and regulatory and methodological documents. The main dense differential medium for determining coliform indicators in domestic methods is the Endo medium, however, in the latest edition of the ISO 9308-1:2000 standard, the Endo medium is replaced by another lactose medium - Tergitol 7. The reason for this replacement was the potential carcinogenicity of fuchsin, an aniline dye that is part of the Endo medium. For the MPN method, liquid enrichment media are used. For potentially clean objects, lactose-peptone water is used; for potentially contaminated objects, Kessler medium or its analogues are used.
It is necessary to note the nutrient media of the new generation, which are often called "chromogenic". Unlike traditional media, they allow determining not a sign, for example, lactose utilization, but directly individual enzymes, the presence of which is characteristic of the desired microorganisms. Chromogenic media for E. coli identification, e.g. Chromocult® or Coli ID, allow you to determine the enzyme β-glucuronidase, highly specific for Escherichia. The presence of this enzyme and the ability to form indole with a 95% probability indicate that enterobacteria belong to the species E. coli. The same media also make it possible to determine the enzyme β-galactosidase, which is characteristic of OTB, but the value of this diagnostic test is doubtful: Aeromonads, free-living oxidase-positive rods that are not related to OTB, also possess this enzyme. Merck tried to improve the chromogenic medium Chromocult EC and introduced into it a selective additive that inhibits the growth of aeromonads.
Of the innovative technologies in the field of sanitary bacteriology of water, it should be noted test systems that use dry media on special plastic substrates. Substrates are an example of such test systems. Petrifilm™ rulers Aqua and in particular the product Aqua Coliform Count Plate (AQCC, 3M™ Petrifilm™), which is designed to determine the OKB and TKB in water. The uniqueness of petrifilms (mediums on substrates) lies in their ease of use. The time-consuming stage of preparation of nutrient media is eliminated, their storage and disposal are facilitated. However, the main advantage over traditional media and media on substrates from other manufacturers is that, already at the stage of primary inoculation, when isolated colonies are obtained, petrifils make it possible to determine not only the ability of bacteria to utilize lactose to acid, but also to detect gas formation. This allows in most cases to reduce the analysis to 1-2 days. In addition, AQCC petrifilms (unlike Endo's medium) can be incubated at 44°C, which allows full use of the high temperature selective factor already at the stage of primary inoculation, which significantly reduces time and labor intensity in the analysis of TKB.
On selective petrifilms Aqua Coliform Count Plate (AQCC,3M™ Petrifilm™) TKB and TKB colonies turn intense red with the formation of gas bubbles around the colony.
Drinking water
The mismatch of water, as well as chemical, makes it undrinkable. If your water source is not protected from direct environmental exposure or the utility systems are outdated or have not been cleaned for a long time, then microbiological testing is a must. Your health and safety depends on it! This is especially important for those who use the well. - ground, it directly contacts the soil, which means it threatens to “drink” you with nitrates, heavy metals, ammonia, and, of course, harmful organic substances that enter the soil as a result of the activities of agricultural farms or lands.
Table 1 shows the microbiological indicators of the current standard SanPiN 2.1.4.1074-01 for drinking water:
Table 1. Microbiological standards for drinking water
Standard microbiological analysis
The standard microbiological analysis of drinking water at Moscow State University includes the determination of three indicators: the total microbial number, the number of total coliform and thermotolerant coliform bacteria.
Advanced microbiological analysis
An extended microbiological analysis of water includes the analysis of five indicators: total microbial count, total coliform bacteria count, thermotolerant coliform bacteria count, coliphage titer and content of spores of sulfite-reducing bacteria.
Microbiological analysis of surface water bodies (ponds, rivers, pools)
Often there are bodies of water on our sites or nearby, where we and our children like to spend time with pleasure. Of course, the water in these reservoirs is not potable, but its safety for humans, as well as drinking, is regulated. Table 2 presents the microbiological indicators of the current standard for hygienic requirements for the protection of surface waters (SanPiN 2.1.5.980-00)
Table 2. Microbiological standards for recreational water use, as well as within the boundaries of populated areas
Standard microbiological analysis (surface waters)
Microbiological analysis of non-drinking water includes the determination of the number of two indicators: total coliform and coliform thermotolerant bacteria.
Advanced microbiological analysis (surface waters):
In addition to the two main indicators, we propose to conduct an additional analysis for the content of: coliphages, opportunistic yeasts and micromycetes (frequent satellites of opportunistic diseases) and the self-purification index of the reservoir.
Determination of bacteria of the genus Salmonella and the genus Enterococcus
With a significant excess of SanPiN 2.1.5.980-00 standards, as well as possible fecal contamination of the reservoir, we propose to analyze for the presence of pathogens of intestinal infections (genus Salmonella and Enterococcus).
Glossary
Total Microbial Abundance (TMC)
The method determines in drinking water the total number of mesophilic aerobic and facultative anaerobic microorganisms (FMC) capable of forming colonies on nutrient agar at a temperature of 37 ° C for 24 hours, visible with a 2-fold increase. This indicator identifies potential bacteria that can harm human health.
Common coliform bacteria (TCB)
Common coliform bacteria (CBC) are gram-negative, oxidase-negative, non-spore-forming rods that can grow on differential lactose media, ferment lactose to acid, aldehyde and gas at a temperature of (37 + 1) ° C for (24-48) hours. Many representatives of this group are microorganisms of the normal microflora of the stomach, so the excess of this group of microorganisms may indicate possible anthropogenic (including fecal) water pollution.
Thermotolerant coliform bacteria (TCB)
Thermotolerant coliform bacteria (TCB) are among the common coliform bacteria, have all their characteristics and, in addition, are able to ferment lactose to acid, aldehyde and gas at a temperature of (44 ± 0.5) ° C for 24 hours. As well as OKB, they are an indicator group, however, they are more stable in the environment: that is why the detection of this group of microorganisms in water can indicate unequivocal contamination of it with human waste products.
coliphages
Coliphages, determined by the standard method (MUK 4.2.1018-01), are E. coli viruses (Escherichia coli) and are considered by epidemiologists as an additional, and sometimes more sensitive, method in determining water pollution by microorganisms of the E. coli group. Virus particles, and coliphages in particular, are more resistant to the environment than their host bacteria. In this regard, the presence of coliphages can serve as a reliable marker of older faecal contamination of the water source. A direct correlation was shown between the content of coliphages in water and enteroviruses dangerous to humans, so the presence of coliphages in water may indicate a viral infection of the source. The current regulatory document (SanPiN 2.1.4.1074-01) implies the absence of coliphages in 100 ml of water.
Spores of sulfite-reducing clostridia
Sulphite-reducing clostridia are spore-forming anaerobic rod-shaped microorganisms, which are an additional microbiological indicator of fecal pollution of a reservoir. Unlike relatively unstable coliform and thermotolerant coliform bacteria, Clostridium spores can persist in water bodies for a long time. Clostridia are found in the intestines of humans and domestic animals, however, if ingested with water in large quantities, they can cause food poisoning. Sulfite-reducing clostridia include clostridium dangerous to humans (Clostridium botulinum, Clostridium perfringens, Clostridium tetani), which cause severe diseases. According to the current standard (SanPiN 2.1.4.1074-01), Clostridia spores should be absent in 20 ml of water.
Opportunistic yeasts and micromycetes
Conditionally pathogenic yeasts and micromycetes (molds) include a large heterogeneous group of fungal organisms that can grow saprotrophically at 37 °C. It includes representatives such as Candida albicans and Cryptococcus neoformans, which are a frequent factor in human opportunistic diseases, causing candidiasis (fungal skin diseases), thrush, and so on. Other micromycete organisms (Cladosporium cladosporioides, Aspergillusniger) can be active sensitizers of allergic reactions, and sometimes allergens themselves. In the Russian Federation, water is not standardized for molds and yeast organisms in water.
Determination of the self-cleaning index (from MUK 4.2.1884-04)
The total number of microorganisms is not standardized in the water of reservoirs in recreation areas, since the level of this group of microorganisms largely depends on the natural characteristics of each object, season, etc.
However, when choosing a new source of water supply or a place of recreation in the water of reservoirs, it is additionally necessary to determine the total microbial population, which grows:
- at a temperature of 37 ° C for 24 hours;
- at 22°C for 72 hours.
It is assumed that:
- TMP at 37 °C is mostly represented by alochthonous microflora (introduced into the reservoir as a result of anthropogenic pollution, including fecal pollution);
- TMP at 20-22 °C is represented, in addition to the alochthonous, aboriginal microflora (natural, characteristic of this reservoir).
The ratio of the numbers of these groups of microorganisms makes it possible to judge the intensity of the self-purification process. At the end of the self-cleaning process, the OMC coefficient is 22 ° C / OMC 37 ° C. In places of pollution by household sewage, the numerical values of both groups are close.
The indicator provides additional information on the sanitary state of water bodies, sources of pollution, and self-purification processes.
Coliform bacteria are always present in the digestive tract of animals and humans, as well as in their waste products. They can also be found on plants, soil and water, where contamination is a major problem due to the possibility of infection by diseases caused by various pathogens.
Harm to the body
Are coliform bacteria harmful? Most of them do not cause disease, however, some rare strains of E. coli can cause serious illness. In addition to humans, sheep and cattle may also be infected. It is worrying that contaminated water, in its external characteristics, is no different from ordinary drinking water in taste, smell and appearance. Coliform bacteria are found even in which is considered to be flawless in every sense. Testing is the only reliable way to find out about the presence of pathogenic bacteria.
What happens when discovered?
What to do if coliform bacteria or any other bacteria are found in drinking water? In this case, repair or modification of the water supply system will be required. When used for disinfection, mandatory boiling is provided, as well as retesting, which can confirm that the contamination was not eliminated if it was thermotolerant coliform bacteria.
indicator organisms
Common coliforms are often referred to as indicator organisms because they indicate the potential presence of pathogenic bacteria in water, such as E. coli. While most strains are harmless and live in the intestines of healthy humans and animals, some can produce toxins, cause serious illness, and even death. If pathogenic bacteria are present in the body, the most common symptoms are gastrointestinal upset, fever, abdominal pain, and diarrhea. Symptoms are more pronounced in children or older family members.
safe water
If there are no common coliform bacteria in the water, then it can be assumed with almost certainty that it is microbiologically safe to drink.
If they were found, then it would be justified to conduct additional tests.
Bacteria love warmth and moisture.
Temperature and weather conditions also play an important role. For example, E. coli prefers to live on the surface of the earth and loves warmth, thus coliform bacteria in drinking water appear as a result of movement in underground streams during warm and humid weather conditions, while the smallest number of bacteria will be found in the winter season.
Impact chlorination
To effectively destroy bacteria, chlorine is used, which oxidizes all impurities. Its amount will be affected by water characteristics such as pH and temperature. On average, the weight per liter is approximately 0.3-0.5 milligrams. It takes approximately 30 minutes to kill common coliform bacteria in drinking water. Contact time can be reduced by increasing the dose of chlorine, but this may require additional filters to remove specific tastes and odors.
Harmful ultraviolet light
Ultraviolet rays are considered a popular disinfection option. This method does not involve the use of any chemical compounds. However, this agent is not used where the total coliform bacteria exceed one thousand colonies per 100 ml of water. The device itself consists of a UV lamp surrounded by a sleeve of quartz glass through which a liquid flows, irradiated with ultraviolet light. The raw water inside the apparatus must be completely clean and free from any visible contaminants, blockages or turbidity to allow exposure of all harmful organisms.
Other cleaning options
There are many other treatment methods used to disinfect water. However, they are not recommended as long term for various reasons.
- Boiling. At 100 degrees Celsius for one minute, bacteria are effectively killed. This method is often used to disinfect water during emergencies or when needed. This takes time and is an energy intensive process and is generally only applied in small amounts of water. This is not a long-term or permanent option for water disinfection.
- Ozonation. In recent years, this method has been used as a way to improve water quality, eliminate various problems, including bacterial contamination. Like chlorine, ozone is a strong oxidizing agent that kills bacteria. But at the same time, this gas is unstable, and it can only be obtained with the help of electricity. Ozone units are generally not recommended for disinfection because they are much more expensive than chlorination or UV systems.
- Iodization. The once popular disinfection method has recently been recommended only for short-term or emergency water disinfection.
thermotolerant coliform bacteria
This is a special group of living organisms that are able to ferment lactose at 44-45 degrees Celsius. These include the genus Escherichia and some species of Klebsiella, Enterobacter and Citrobacter. If foreign organisms are present in the water, this indicates that it has not been sufficiently cleaned, re-contaminated, or contains nutrients in excess. When they are detected, it is necessary to check for the presence of coliform bacteria that are resistant to elevated temperatures.
Microbiological analysis
If coliforms were found, then this may indicate that they got into the water. Thus, various diseases begin to spread. In contaminated drinking water, strains of Salmonella, Shigella, Escherichia coli and many other pathogens can be found, ranging from mild digestive tract disorders to severe forms of dysentery, cholera, typhoid fever and many others.
Household sources of infection
The quality of drinking water is monitored, it is regularly checked by specialized sanitary services. And what can an ordinary person do to protect himself and protect himself from unwanted infection? What are the sources of water pollution in the home?
- Water from the cooler. The more people touch this device, the more likely it is that harmful bacteria will enter. Studies show that the water in every third cooler is simply teeming with living organisms.
- Rainwater. Surprisingly, the moisture collected after the rain is a favorable environment for the development of coliform bacteria. Advanced gardeners do not use such water even for watering plants.
- Lakes and reservoirs are also at risk, since all living organisms multiply faster in stagnant water, and not just bacteria. An exception is the oceans, where the development and spread of harmful forms is minimal.
- Pipeline condition. If the sewers have not been changed and cleaned for a long time, this can also lead to trouble.
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Since this method of water analysis involves only determining the total number of colony-forming bacteria of different types, its results cannot unambiguously judge the presence of pathogenic microbes in the water. However, a high microbial count indicates a general bacteriological contamination of water and a high probability of the presence of pathogenic organisms.When analyzing water, it is necessary to control not only the content of toxic chemicals, but also the number of microorganisms that characterize the bacteriological contamination of drinking water. TMF is the total microbial number. In the water of centralized water supply, this number should not exceed 50 CFU / ml, and in wells, wells - no more 100 cfu/ml
Sanitary and microbiological research of water is carried out in a planned
order for the purpose of current surveillance, as well as for special epidemiological
kim testimony. The main objects of such research are:
Drinking water of the central water supply (tap water);
Drinking water of non-centralized water supply;
Water from surface and underground water sources;
Wastewater;
Water of coastal zones of the seas;
Swimming pool water.
The main indicators for assessing the microbiological state of drinking water in accordance with the current regulatory documents are:
1. Total microbial count (TMC) - the number of mesophilic bacteria in 1 ml of water.
If the titer- the smallest volume of water (in ml) in which at least one living
microbial cell related to BGKP.
BGKP index- the amount of BGKP in 1 liter of water.
3. The number of spores of sulfite-reducing clostridia in 20 ml of water.
4. Number of coliphages in 100 ml of water.
Determination of TMC makes it possible to assess the level of microbiological contamination of drinking water. This indicator is indispensable for the urgent detection of massive microbial contamination.
Total microbial count- this is the number of mesophilic aerobic and facultative anaerobic microorganisms capable of forming colonies on nutrient agar at a temperature of 37 ° C and within 24 hours, visible at a twofold increase.
When determining the total microbial number, 1 ml of the test water is added to a sterile Petri dish and 10-12 ml of warm (44 ° C) molten nutrient agar is poured. The medium is gently mixed with water, uniformly and
without air bubbles distributing along the bottom of the cup, then cover with a lid and leave to solidify. Crops are incubated in a thermostat at 37 °C for 24 hours. Count the total number of colonies grown in both dishes and determine the average value. The final result is expressed as the number of colony forming units (CFU) in 1 ml of the test water. 1 ml of drinking water should contain no more than 50 CFU
Definition of BGKP
At the same time, common coliform bacteria - OKB and thermotolerant coliform bacteria - TKB are determined.
GKB are gram-negative, non-spore-forming rods that ferment lactose to acid and gas at 37°C for 24-48 hours. TKB are among the OKB, they have their signs, but I ferment at 44 ° C. For the determination of enterobacteria - the method of membrane filters or titration.
Microbial number - the main criteria for assessing the microbiological state of drinking water, based on the current regulatory documents, is TMC (total microbial number), which characterizes the number of aerobic and anaerobic bacteria in one milliliter of water, formed per day at a temperature of 37 degrees, in a nutrient medium. This indicator is virtually indispensable for the rapid detection of massive microbial contamination.
For determination of the total microbial number one milliliter of the test water is added to a sterile Petri dish, then 10-15 ml of warm (about 44 ° C) nutrient agar is poured in a molten form. The medium is carefully mixed with water, distributed evenly and without air bubbles over the bottom of the dish, then closed with a lid and left in the Petri dish until solidified. The same is done in the other cup. Sowing in a thermostat is incubated at a temperature of 37 ° C during the day. Then, at double magnification under a microscope, the total number of colonies grown in two cups is counted, and the average value is determined. In 1 ml of drinking water should not be more than 50 CFU.
Organoleptic indicators
Smell natural water is caused by volatile odorous substances that enter the water naturally or with sewage. Springs containing only inorganic matter may smell of hydrogen sulfide. The intensity of the smell is estimated in points on a five-point scale, determined at a water temperature of 20°C. According to GOST, drinking water can smell up to 2 points.
The main smell in the studied springs is hydrogen sulfide. The source of hydrogen sulfide in natural waters is the recovery processes that occur during bacterial decomposition and biochemical oxidation of organic substances of natural origin and substances entering water bodies with wastewater. Hydrogen sulfide is found in the waters of springs in the form of non-dessociated H2S molecules and hydrosulfate HS ions. The presence of hydrogen sulfide in water is an indicator of its severe pollution and anaerobic conditions. It is the reason for the impossibility of its consumption, since hydrogen sulfide has a high toxicity, a bad smell, which sharply worsens the organoleptic properties of water, making it unsuitable for drinking water supply, technical and economic purposes.
Chroma due to the content of colored organic compounds in water, the presence of humic compounds, the content of ferric iron, the leaching of various substances from soils, and the ingress of contaminated wastewater. Humic substances - the result of the decomposition of plant residues - color the water, depending on the concentration, yellow or brown. The degree of color is expressed in degrees of the platinum-cobalt scale. High or increased color adversely affects the development of living organisms, worsens the conditions for the oxidation of iron dissolved in water.
The color standard according to SanPiN is 30 degrees.
Turbidity according to SanPiN standards, it should not exceed 1.5 mg / l. The turbidity of water in springs most often depends on the presence of suspended particles of silt, fine clay, high content of total iron and a number of other substances, often associated with undeveloped or poorly equipped places where springs exit and water storage tanks, and low flow rates of springs.
Hydrogen index (pH) is a value that characterizes the activity of the concentration of hydrogen ions in solutions and is numerically equal to the negative decimal logarithm of this activity or concentration, expressed in mol/dm3:
If water at 22°C contains 10-7.2 mol/dm3 of hydrogen ions (H+), then it will have a neutral reaction; with a lower content of H +, the reaction will be alkaline, with a higher content, it will be acidic. Thus, at pH = 7.2 the reaction of water is neutral, at pH 7.2 it is alkaline.
The pH value plays an important role in determining the quality of water. In river and spring waters, its value ranges from 6 to 8.5. The concentration is subject to seasonal fluctuations - in winter it is usually 6.8 - 7.4, in summer - 7.4 - 8.2.
The concentration of hydrogen ions is of great importance for chemical and biological processes occurring in natural waters. It determines the development and vital activity of aquatic plants, the stability of various forms of element migration, the degree of aggressiveness of water in relation to metals, concrete, etc.
For a person, slightly acidic waters (pH - 6.7 - 6.8) seem to be tastier than alkaline ones, therefore cold winter waters are "tastier" than warm summer waters.
Generalized indicators
Rigidity- a property of natural water, determined by the presence in it of dissolved salts of alkaline earth metals - calcium, magnesium and some others. The main characteristics that determine the hardness of water is the presence of calcium and magnesium ions in water. The upper limit of drinking water hardness in water supply systems, according to current sanitary standards, should not exceed 7-10 mg * eq / l. One milliequivalent of hardness corresponds to 20.04 mg/l Ca2+ or 12.16 mg/l Mg2+. When water is boiled for a long time, carbon dioxide is released from it and a precipitate consisting of calcium carbonate precipitates, while the hardness of the water decreases. Therefore, the term “temporary or removable hardness of water” is used, while understanding the presence of hydrocarbonate salts in water, which can be removed from water by boiling for one hour. The hardness of water remaining after boiling is called constant.
The hardness of natural water varies widely. In the same water body, its values change depending on time.
Natural waters are classified by total hardness as follows:
Very soft - up to 1.5 mmol/dm3
Soft - 1.5 - 3.0 mmol / dm3
Moderately hard -3.0 - 6.0 mmol/dm3
Rigid - 6.0 - 9.0 mmol/dm3
Very hard > 9.0 mmol/dm3.
According to the current standard, the hardness of drinking water should not exceed 7 mmol/dm3. For drinking, the use of relatively hard water is allowed, since the presence of calcium and magnesium salts is not harmful to health and does not impair the taste of water.
Recent studies have found that hard water, which is high in calcium and magnesium salts, puts extra stress on the kidneys and can cause kidney stones to form. The most favorable for the human body is water with a hardness of 3-4.5 mmol/dm3. Water with low hardness leaches salts from the body and then there is a threat of osteoporosis. On the other hand, there are studies that show a reduction in the risk of cardiovascular disease with the constant consumption of water with high hardness.
Dry residue is the sum of all water impurities, determined by evaporating the sample. The dry residue characterizes the general mineralization of water. Water suitable for water supply should not have a salinity higher than 1000 mg/dm3. According to the degree of mineralization of water, it is customary to subdivide into four groups: ultra-fresh with a salt content of up to 200 mg / dm3, fresh - from 200 to 500, increased mineralization - from 500 to 1000 and high salinity - above 1000 mg / dm3.
With an increase in the total salt content, the electrical conductivity of water increases and this leads to an acceleration of corrosion processes. Increased salt concentration can lead to a decrease in vegetation and oxygen.
inorganic substances
Nitrites (NO2-) in natural waters they are found in connection with the decomposition of organic substances and their nitrification. Nitrites are unstable components of natural waters. Their highest concentration (up to 10–20 mg/dm3 of nitrogen) is observed during summer stagnation. With a sufficient concentration of oxygen, the oxidation process proceeds further under the action of bacteria, and nitrites are oxidized to nitrates.
The increased content of nitrites indicates the presence of processes of decomposition of organic substances under conditions of slow oxidation of NO2- to NO3-, which indicates pollution of the water body with organic substances, i.e. is an important health indicator.
MPC for nitrites in drinking water is 3.0 mg/dm3.
Nitrates (NO3-)- compounds of nitric acid. The presence of nitrate ions in natural waters is associated with intra-aquatic processes of nitrification of ammonium ions in the presence of oxygen under the action of nitrifying bacteria. The content of nitrates increases by autumn and reaches a maximum in winter. An increased content of nitrates indicates a deterioration in the sanitary condition of the water body. At the same time, nitrates are the least toxic form of all nitrogen compounds (nitrites, ammonium) and can only be harmful to health at very high concentrations.
MPC for nitrates in drinking water is 45 mg/dm3.
chlorides- chloride ions are the main ions of the chemical composition of natural waters. The concentration of chlorides in springs ranges from fractions of a milligram to hundreds and thousands per 1 dm3.
The primary source of chlorides in natural waters are igneous rocks, which include chlorine-containing minerals (sodalite, chlorapatite, etc.). A significant amount of chlorides enter natural waters from the ocean through the atmosphere. Chlorides have a high migration ability, a weak ability to sorption on suspended solids and to be consumed by aquatic organisms.
The increased content of chlorides worsens the taste of water and makes it unsuitable for drinking water supply. The concentration of chlorides in surface waters is subject to noticeable seasonal fluctuations, correlated with changes in water salinity. MPC for chlorides is 350 mg/dm3.
sulfates- the natural content of sulfates in groundwater is due to weathering of rocks and biochemical processes occurring in aquifers. Some of them come in the process of death of organisms and oxidation of substances of plant and animal origin. The increased content of sulfates worsens the organoleptic properties of water and has adverse physiological effects on the human body.
Under aerobic conditions, sulfates do not change, while under anaerobic conditions, sulfates are reduced by obligate sulfate-reducing bacteria to sulfides, which then precipitate mainly in the form of iron sulfide. This process is observed in spring water storage tanks and wells, if they are little used, and water stagnates in them.
MPC in drinking water up to 500 mg/dm3.
Iron compounds almost always present in natural waters. Forms of the presence of iron in water are diverse. In the divalent state, iron can be present in water only at low pH and Eh values. It should be noted that only ferrous iron can be absorbed by the body, and not its most common trivalent form.
Iron compounds are present in water in dissolved, colloidal and undissolved form.
The increased content of more than 1 mg/dm3 of iron in drinking water worsens the quality of water and the possibility of its use for food purposes. Too much iron in the diet can cause numerous adverse effects on the body.
Water analysis is usually carried out according to the following parameters:
Parameter |
Units |
Chroma |
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Turbidity |
FMU / mg/l |
Oxidability permanganate |
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Dry residue |
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Conductivity |
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General hardness |
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Alkalinity |
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Bicarbonates |
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sulfates |
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Ammonium salts (NH4) |
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Nitrites (by NO2) |
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Nitrates (according to NO3) |
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Aluminum |
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Beryllium |
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Iron (total) |
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Iron Fe++ |
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Silicon (in Si) |
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Manganese |
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Molybdenum |
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Oil products |
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hydrogen sulfide |
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Strontium |
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Carbon dioxide |
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Chlorine residual free |
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Residual chlorine bound |
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Phosphates (in PO4) |
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microbiological indicators
OKB- the content of common coliform bacteria in water is an indicator of the quality of drinking water. They are easy to detect and quantify, so for many years they have been used as a kind of indicator of water quality.
OKB is an international qualification and they are part of a large group of BGKP (bacteria of the Escherichia coli group). The content of OKB in water can be determined by two methods: the method of membrane filters and the titration (fermentation) method.
Investigation of water by the method of membrane filters. The method is based on filtering a specified volume of water through membrane filters, growing crops on a differential diagnostic medium and subsequent identification of colonies by cultural and biochemical characteristics.
Titration method for the study of water. The method is based on the accumulation of bacteria after inoculation of a specified volume of water into a liquid nutrient medium, followed by re-inoculation onto a differential diagnostic medium and identification of colonies by cultural and biochemical tests.
"Coliform organisms" belong to a class of gram-negative, rod-shaped bacteria that live and multiply in the lower digestive tract of humans and many warm-blooded animals such as livestock and waterfowl, capable of fermenting lactose at 35-37 C to form acid , gas and aldehyde. Once in water with fecal effluents, they are able to survive for several weeks, although the vast majority of them lack the ability to reproduce.
According to recent studies, along with the bacteria Escherichia (E.Coli), Citrobacter, Enterobacter and Klebsiela, which are usually attributed to this class, the bacteria Enterobacter cloasae and Citrobadter freundii capable of fermenting lactose also belong to this class. These bacteria can be found not only in faeces, but also in the environment, and even in drinking water with a relatively high concentration of nutrients. In addition, this includes species that are rarely or not found in faeces and are able to breed in water of fairly good quality.
TKB- thermotolerant coliform bacteria. The number of TCB characterizes the degree of fecal contamination of water in water bodies and indirectly determines the epidemic danger in relation to pathogens of intestinal infections. TKB is determined by the same methods as BGKP (OKB).
OMC 37- total microbial count. Determining the number of pathogenic bacteria in the biological analysis of water is a difficult and time-consuming task; as a criterion for bacteriological contamination, the total number of colony-forming bacteria (Colony forming Units - CFU) in 1 ml of water is used.
| No. p / p | Indicator, units of measurement | Standards*, no more | Comment | ||||||
| SanPiN 2.1.4.1175-02 | GN 2.1.5.1315-03 |
SanPiN 2.1.4.1116-02 | WHO | EU | USA | ||||
| first category. | higher category | ||||||||
| 1 | 2 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| 1 | Smell, points at 20°C |
3 | – | 0 | 0 | 0 | Acceptable to the consumer without anomalous changes | – | The intensity of the smell is estimated on a 5-point scale: 0 - no smell, 1 - very weak (detected by an experienced specialist), 2 - weak (detected if you pay attention), 3 - noticeable (easily detectable), 4 - distinct (draws attention and makes water unpleasant to drink), 5 - very strong (undrinkable) |
| 2 | at 60°C | – | – | 1 | 0 | – | – | ||
| 3 | Taste (at 20°C), points | 3 | – | 0 | 0 | 0 | – | The intensity of taste is evaluated on a 5-point scale (see indicator No. 1 "Smell") | |
| 4 | pH | Within 6-9 | – | Within 6,5-8,5 |
6,5-8,5 | 6,5-9,5 | 6,5-8,5 | Depending on the pH, natural waters are divided into groups: strongly acidic (pH<3), кислые (3–5), слабокислые (5–6,5), нейтральные (6,5–7,5), слабощелочные (7,5–8,5), щелочные (8,5-9,5), сильнощелочные (>9,5). |
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| 5 | Еh, mV | – | – | – | – | – | – | The redox potential reflects the type of geochemical environment. There is the following vertical zonality of groundwater: oxygen water (Eh>200 mV), oxygen-free and sulfide-free water (Eh=200–100 mV), sulfide water (Eh<100 мВ, а чаще менее 0 мВ). From Eh and pH depends on the solubility and forms of migration in water of various elements, the vital activity of microorganisms. Both of these indicators must be determined immediately after sampling. |
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| 6 | Electrical conductivity at 25°С, µS/cm | – | – | – | – | 2500 | – | By electrical conductivity, one can approximately judge the total content of mineral salts dissolved in water. | |
| 7 | Chromaticity, ° | 30 | – | 5 | 5 | 15 | 20 | 15 | This indicator characterizes the intensity of water color and is expressed in degrees on the chromium-cobalt scale. The presence of color in natural waters is usually due to humic substances or iron salts dissolved in them. The waters of water supply sources are divided by color into low-color (up to 35°), medium color (from 35 to 120°), high color (> 120°). |
| 8 | Turbidity "according to formazin", EMF |
3,5 | – | 1,0 | 0,5 | 4,9 | 4,0 | 5 | Water turbidity is caused by suspended particles larger than 100 nm. |
| 9 | Rigidity general, mg-eq/l |
10 | – | 7 | Within 1.5-7.0 | 10 | – | – | Term rigidity determines the properties that calcium and magnesium compounds dissolved in it give to water. By hardness, water is divided into very soft (<1,5 мг-экв/л), мягкие (1,5–3), умеренно жесткие (3–5,4), жесткие (5,4–10,7), очень жесткие (>10,7). In the household aspect, water with increased hardness (> 8 mg-eq / l) is unfavorable due to the formation of scale, increased consumption of detergents, and poor cooking of meat and vegetables. The standard for the physiological usefulness of drinking water in terms of hardness salts is from 1.5 to 7.0 mg-eq / l. |
| Main ions: | |||||||||
| 10 | Bicarbonates (HCO3-), mg/l |
– | – | 400 | Within 30-400 | – | – | – | The standard for the physiological usefulness of drinking water in terms of bicarbonates is from 30 to 400 mg / l. |
| 11 | sulfates (SO42-), mg/l |
500 | 500 (LPV - org., hazard class 4) |
250 | 150 | 250 | 250 | 250 | The presence of a large amount of sulfates in water is undesirable, since they 1) worsen its taste (in the presence of sulfates in the form of MgSO4, a bitter aftertaste occurs, in the form of CaSO4 - astringent), 2) have laxative properties (in the presence of sulfates in the form of Na2SO4), 3) lead to the formation of foam on the surface of the water. |
| 12 | chlorides (Сl-), mg/l |
350 | 350 (org., 4) |
250 | 150 | 250 | 250 | 250 | Elevated concentrations of chlorides worsen the taste of water (in the presence of sodium ions, they give a salty taste). |
| 13 | Calcium (Ca2+), mg/l |
– | – | 130 | Within 25-80 | – | 100 | – | The standard of physiological usefulness for calcium is from 25 to 130 mg / l. |
| 14 | Magnesium (Mg2+), mg/l |
– | 50 (org., 3) |
65 | Within 5-50 |
– | 50 | – | The concentration of magnesium was obtained by calculation from the results of determining hardness and calcium. The standard of physiological usefulness for magnesium is from 5 to 65 mg / l. |
| 15 | Sodium (Na+), mg/l |
– | 200 (s-t, 2) |
200 | 20 | 200 | 200 | – | |
| 16 | Iron total, mg/l | – | 0,3 (org., 3) |
0,3 | 0,3 | 0,3 | 0,2 | 0,3 | When the content of total iron in water is more than 1-2 mg / l (ferrous iron - more than 0.3 mg / l), it begins to give the water an unpleasant astringent taste. Colloidal iron compounds give water a color (from yellowish to greenish hues). When in contact with atmospheric oxygen, water with a high iron content becomes cloudy due to the precipitation of Fe (OH) 3 solid particles. Long-term human consumption of water with a high iron content can lead to liver disease (hemosideritis), allergic reactions, the formation of kidney stones, and also increases the risk of heart attacks and diseases of the skeletal system. |
| 17 | Manganese, mg/l | – | 0,1 (org., 3) |
0,05 | 0,05 | 0,5 | 0,05 | 0,05 | Both ferrous iron and manganese worsen the taste of water even at their low content. When the manganese content is more than 0.5 mg/l, the water acquires an unpleasant taste. Excess manganese is dangerous to health: its accumulation in the body can lead to Parkinson's disease. It is usually accepted that the total content of iron and manganese in drinking water should not exceed 0.5–1.0 mg/l. |
| 18 | Fluorine, mg/l | 1,5 (s-t., 2) |
1,5 | In the range of 0.6–1.2 | 1,5 | In the range of 0.7–1.5 | 4,0 | The standard of physiological usefulness is in the range of 0.5–1.5 mg / l. At concentrations above 1.5 mg/l, it can cause dental fluorosis, and above 4 mg/l, serious bone disease. | |
| 19 | Ammonium (N–NH4+), mg/l |
– | 1,5 for the sum of ammonia (NH3) and ammonium (NH4) (org., 4) |
0,1 | 0,05 | 1,5 | 0,5 | – | Nitrogen-containing substances (ammonium ions, nitrite and nitrate ions) are formed in water mainly as a result of the decomposition of protein compounds that almost always enter it with domestic waste water or livestock effluents. The ammonium ion, like the nitrite ion, is a good indicator of organic water pollution. Marsh waters can also be a source of nitrogen compounds. In them, the ammonium ion is formed due to the reduction of nitrates by humic compounds. |
| 20 | Nitrites (NO2-), mg/l |
– | 3,3 (s-t., 2) |
0,5 | 0,005 | 3,0 | 0,5 | 3,3 | Nitrite is an intermediate step in the bacterial oxidation of ammonium to nitrate (under aerobic conditions) or, conversely, the reduction of nitrate to ammonium (under anaerobic conditions). The presence of nitrite ions usually indicates an existing organic contamination of the water. |
| 21 | Nitrates (NO32-), mg/l |
45 | 45 (s-t., 3) |
20 | 5 | 50 | 50 | 44 | The origin of nitrates in groundwater is either inorganic - due to the leaching of nitrogen-containing minerals (eg saltpeter) - or organic, when nitrates are the end product of the mineralization of organic substances. In the latter case, the presence of the nitrate ion indicates the former pollution of water with organic waste, and if present together with nitrites and ammonium, it indicates the pollution that exists at the present time. If it is necessary to use such water for drinking needs, bacteriological analysis is required. In the presence of more than 50 mg / l of nitrates in water, a violation of the oxidative function of the blood is observed - methemoglobinemia. |
| 22 | phosphates, (PO43-), mg/l |
– | 3,5 for polyphosphates (org., 3) |
3,5 | 3,5 | – | – | – | In groundwater, the content of phosphates is usually low. With a high content of phosphates, it can be concluded that there are impurities in the water of fertilizers, components of domestic wastewater (mainly detergents), and decomposing biomass. |
| 23 | General mineralization, mg/l | 1500 | – | 1000 | In pre-cases 200-500 | – | – | 500 | The standard of physiological usefulness is from 100 to 1000 mg/l. The value of mineralization characterizes the total content in water mineral substances. In this case, the total mineralization is obtained as the arithmetic sum of the amounts of all ions contained in the test water. Waters with a mineralization of more than 1000 mg/l are classified as mineralized. The lower limit of mineralization, at which there is no leaching of salts from the body, corresponds to a value of 100 mg/l. The optimal level of mineralization of drinking water is in the range of 200–500 mg/l. |
| 24 | Dry residue, mg/l | 1500 | – | 1000 | Within 200-500 | – | – | 500 | Dry residue is a conditional indicator that determines the content of dissolved and colloidal impurities remaining during water evaporation. It was obtained by evaporating water filtered through a membrane filter with a pore size of 0.45 μm. |
| 25 | Permanganate oxidizability, mg О2/l | 7 | – | 3 | 2 | – | 5 | – | Oxidability is one of the indirect indicators of the amount contained in water organic substances. Potassium permanganate usually oxidizes 25-50% of the organic matter contained in the water. |
| 26 | Oil products | – | 0,3 | 0,05 | 0,01 | – | – | – | Oil products in the analysis of water are conventionally considered to be only non-polar and low-polar hydrocarbons, soluble in hexane, which make up the bulk of the oil. Petroleum products were determined by the fluorimetric method on the Fluorat-02 liquid analyzer. |
