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 purified, 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 the most 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.
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 on 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 0C 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).
Sampling for sanitary and microbiological studies should be carried out in compliance with the rules of sterility and all the necessary conditions regulated for each object under study by the relevant regulatory documents.
Sampling errors lead to incorrect results. When packing and transporting samples, it is necessary to create conditions that exclude the death or reproduction of the original microbiota in the object under study. Therefore, the collected samples should be delivered to the laboratory for analysis as soon as possible.
Hygienic requirements for the quality of water for drinking and domestic needs are based on the principle that puts the focus on water quality, on which human health and living conditions depend. In accordance with modern sanitary legislation, drinking water must be safe in epidemic and radiation terms, harmless in chemical composition and have favorable organoleptic properties.
The safety of drinking water in an epidemic respect is determined by its compliance with the standards for microbiological indicators. The microbiological composition of drinking water is the main indicator of its quality and suitability for consumption. This takes into account both bacterial and viral contamination.
The epidemiological safety of drinking water in SanPiN is assessed by several indicators. A large role among them is assigned to thermotolerant coliforms as true indicators of fecal pollution and total coliforms.
Common coliform bacteria (CBC) are gram-negative, oxidase-negative, non-spore-forming rods that can grow on differential lactose media, fermenting lactose to acid and gas at a temperature of +37 for 24-48 hours.
Thermotolerant coliform bacteria (TCB) are part of the OKB and have all their characteristics, but unlike them, they are able to ferment lactose to acid, aldehyde and gas at a temperature of +44 for 24 hours. Thus, TKB differs from OKB in its ability to ferment lactose to acid and gas at a higher temperature. Thermotolerant and common coliforms should be absent in 100 ml of drinking water (in any of the samples with a threefold repetition of the analysis).
In the distribution network of large centralized drinking water supply systems (with the number of samples being studied at least 100 per year), 5% of non-standard samples for common coliforms are allowed, but not in two consecutive samples taken at one point.
The total number of microorganisms (total microbial number - TMC) is determined by growth on meat-peptone agar at an incubation temperature of 37. This indicator is used to characterize the efficiency of drinking water purification, it must be considered when monitoring water quality in dynamics. A sharp deviation of TMF even within the limits of the standard value (but not more than 50 in 1 ml) serves as a signal of a violation in the water treatment technology. The growth of TMP in the water of the distribution network may indicate its unfavorable sanitary condition, which contributes to the reproduction of microorganisms due to the accumulation of organic substances or leakage, which entails the suction of contaminated groundwater.
Aerobic saprophytes make up only a part of the total number of microbes in water, but they are an important sanitary indicator of water quality, since there is a direct relationship between the degree of contamination with organic substances and the microbial number. In addition, it is believed that the higher the total microbial count, the more likely the presence of pathogenic microorganisms in the water. The microbial number in tap water should not exceed 100.
The safety of drinking water in an epidemic sense is determined by its compliance with the standards for microbiological indicators (Table 1).
Table 1. Microbiological indicators of drinking water
The concept of sanitary indicative microorganisms
The main requirements for sanitary-indicative microorganisms: 1. they must have a common natural habitat with pathogenic microorganisms and be released into the external environment in large quantities; 2. In the external environment, sanitary-indicative microorganisms should be as evenly distributed as possible and be more resistant than pathogenic ones. They should remain in the water longer, practically not multiplying, be more resistant to various adverse factors, they should exhibit less variability in properties and characteristics; 3. methods for determining sanitary indicative microorganisms should be simple and have a sufficient degree of reliability.
From the standpoint of sanitary microbiology, water quality assessment is carried out in order to determine its sanitary and epidemiological danger or safety. For human health. Water plays an important role in the transmission of pathogens of many infections, mainly intestinal ones.
Direct quantitative determination of all infections for water quality control is not feasible due to the diversity of their types and the complexity of the analysis.
The analysis of only one water sample for the possible presence of pathogens of typhoid fever, paratyphoid A, paratyphoid B, dysentery, infectious jaundice, water fever and tularemia in it would completely load the entire staff of even a large bacteriological laboratory. In addition, the answer in this case would be given only after 2-3 weeks, i.e. when the population has already drunk the studied water for a long time.
In view of the obvious inexpediency of a detailed definition of the safety of water, as early as the end of the 19th century, attempts were made to replace the search for all water pathogenic microbes with one microbe, albeit non-pathogenic, but constantly present in human feces. Then it could be considered that if the water under study is indeed contaminated with faeces, then it can be dangerous for drinking, since both sick people and bacillus carriers can be found among the healthy population. The search for such bacteriological indicators of faecal contamination has been successful. It turned out that three of the following microbes are constantly present in human feces: 1) Escherichia coli; 2) enterococci; 3) anaerobic spore-forming bacteria, mainly Bac. perfingens.
Thus, E. coli predominates in domestic wastewater. But it's not just about the content. The main value of a bacterial indicator of faecal contamination lies in the fact that its rate of death of most pathogenic microbes. Only if this condition is met, a microbe constantly present in human feces will be an indicator of fecal contamination.
If we approach the discovered permanent inhabitants of the intestine from this point of view, we will find the following: microbes of the Bac group. perfingens persists in water much longer than pathogenic microbes; enterococci, on the contrary, die much sooner; as for Escherichia coli, the time of its preservation in water approximately corresponds to the survival time of pathogenic microbes.
Therefore, the main sanitary-bacteriological indicator of water is Escherichia coli. Only in Russia, the only country in the world, water quality is controlled by the bacterium of the Escherichia coli group (BGKP index). This group includes all representatives of the group of intestinal bacteria and opportunistic representatives.
In accordance with GOST 2874-73 and GOST 18963-73, bacteria of the Escherichia coli group (ECG) include gram-negative, non-spore-forming bacilli that ferment lactose or glucose to acid and gas at 37 ° in 24 hours and do not have oxidase activity. CGBs include representatives of various genera - Escherichia, Citrobacter, Enterobacter, Klebsiella, but they are all released into the environment from the intestines of humans and animals. In this regard, their detection in the environment should be considered as an indicator of faecal contamination.
Of the genera included in the BGKP, the genus Escherichia has the most sanitary and indicative value. The presence of all these bacteria in the environment is considered fresh faecal contamination.
Escherichia - is one of the background species of the intestines of humans and animals. The genus Escherichia, including the type species E. coli, is an indicator of fresh faecal contamination, a possible cause of toxic infections. Representatives of the genus in water are treated as thermotolerant coliform bacteria.
Citrobacter - live in wastewater, soil and other environmental objects, as well as in the feces of healthy and AII patients. They belong to the group of opportunistic bacteria. (Microbiological dictionary-reference book, 1999)
The disadvantages of citrobacter as SPMO include the following:
1. an abundance of analogues in the external environment.
2. variability in the external environment.
3. insufficient resistance to adverse effects.
4. the ability to reproduce in water.
5. fuzzy indicator even for the presence of salmonella.
Recent studies have revealed the absence of a direct correlation between the presence of pathogenic bacteria and indicators in water. In regions with intense anthropogenic pressure on water bodies, a decrease in the content of indicator microorganisms was noted with a change in their biological and cultural properties against the background of the quantitative predominance of potential pathogenic and pathogenic bacteria.
Enterobacter - live in the intestines of humans and other animals, are found in soil, water, food products, call for intestinal, urogenital, respiratory, purulent-inflammatory human diseases.
Klebsiella - live in water, soil, food, in the intestines and respiratory tract of humans, mammals, birds.
In 1910 Enterococci (Enterococcus faecalis, Enterococcus faecium) have been proposed for the role of SPMO.
Enterococci are a genus of facultative anaerobic asporogenic chemoorganotrophic Gram+ bacteria. Cells are polymorphic. Widely distributed in nature. They are one of the background species of the intestines of humans, mammals, birds. Often found in the flora of the skin of the perineum and genital tract, nasal cavities, pharynx, nose. Long survive in the soil, food products.
Benefits of Enterococcus as SPMO:
1. is constantly in the human intestine and is constantly released into the external environment. At the same time, Enterococcus faecalis mainly lives in the human intestine, so its detection indicates contamination with human feces. To a lesser extent, Enterococcus faecium occurs in humans. The latter is mainly found in the intestines of animals, although Enterococcus faecalis is also relatively rare.
2. is not able to reproduce in the external environment, Enterococcus faecium mainly reproduces, but it has less epidemiological significance.
3. does not change its properties in the external environment.
4. has no analogues in the external environment.
5. resistant to adverse environmental influences. Enterococcus is 4 times more resistant to chlorine than Escherichia coli. This is his main merit. Due to this characteristic, enterococcus is used to check the quality of water chlorination, as well as an indicator of the quality of disinfection. Withstands a temperature of 60 ° C, which allows it to be used as an indicator of the quality of pasteurization. resistant to common salt concentrations of 6.5-17%. Resistant to pH in the range of 3-12.
6. Highly selective media have been developed for the indication of enterococci. The survival rate of Enterococcus in water approaches that of pathogenic Enterobacteria. Enterococcus is rightfully the second sanitary-indicative test after E. coli in the study of drinking water.
Currently, enterococcometry is legalized in the international water standard as an indicator of fresh fecal contamination. When atypical Escherichia coli are found in the water, the presence of enterococci becomes the main indicator of fresh fecal contamination. Unfortunately, in SanPiN 2.1.4.1074-01 for drinking water, the definition of enterococcus is not provided.
The Proteus group is considered as the culprit of putrefactive processes in nature, and therefore, as indicators of the presence of organic substances in the water of reservoirs. This applies mainly to one species - Pr. vulgaris; the second species - Pr.mirabilis - is an inhabitant of the intestines of humans and animals. This ecological difference made it possible to judge the nature of water pollution and the degree of its epidemic safety. Pr.vulgaris can be an indicator of faecal pollution, Pr.vulgaris - an indicator of an increase in the concentration of organic matter in general. The weaknesses of this indicator are the intermittent presence of Pr.mirabilis in the human intestine and the ability of both species to reproduce quite intensively in water. There is also no research method that would allow differentially taking into account both species when they are simultaneously present in the test sample. The proposed method does not fulfill this task.
It has now been shown that bacteria of the genus Proteus are found in 98% of cases in the secretions of the intestines of humans and animals, of which 82% of cases are Pr.mirabilis. detection of proteus in water indicates contamination of the object with decaying substrates and indicates extreme sanitary problems. Proteometry is officially recognized in the USA.
Identification of spores of sulfide-reducing clostridia is carried out on water pipes from surface sources to assess the effectiveness of technological water treatment. Spores of sulfide-reducing bacteria should not be present in 20 ml of drinking water after completion of water treatment.
As an indicator of viral contamination of drinking water, SanPiN includes coliphages, which are closest to intestinal viruses in their biological origin, size, properties, resistance to environmental factors. Coliphages should not be detected in 100 ml of treated drinking water.
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 |
|
Turbidity |
FMU / mg/l |
Oxidability permanganate |
|
Dry residue |
|
Conductivity |
|
General hardness |
|
Alkalinity |
|
Bicarbonates |
|
sulfates |
|
Ammonium salts (NH4) |
|
Nitrites (by NO2) |
|
Nitrates (according to NO3) |
|
Aluminum |
|
Beryllium |
|
Iron (total) |
|
Iron Fe++ |
|
Silicon (in Si) |
|
Manganese |
|
Molybdenum |
|
Oil products |
|
hydrogen sulfide |
|
Strontium |
|
Carbon dioxide |
|
Chlorine residual free |
|
Residual chlorine bound |
|
Phosphates (in PO4) |
|
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 on 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). |
|
| 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 humus compounds. |
| 20 | Nitrites (NO2-), mg/l |
– | 3,3 (s-t., 2) |
0,5 | 0,005 | 3,0 | 0,5 | 3,3 | Nitrites are an intermediate step in the bacterial processes of ammonium oxidation to nitrates (under aerobic conditions) or, conversely, the reduction of nitrates 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 the water contains impurities 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. |
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 on 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 0C 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).
Sampling for sanitary and microbiological studies should be carried out in compliance with the rules of sterility and all the necessary conditions regulated for each object under study by the relevant regulatory documents.
Sampling errors lead to incorrect results. When packing and transporting samples, it is necessary to create conditions that exclude the death or reproduction of the original microbiota in the object under study. Therefore, the collected samples should be delivered to the laboratory for analysis as soon as possible.
