Between groups of sanitary-indicative microorganisms there are no clearly defined boundaries. Some microorganisms are indicators of both faecal and oral contamination. Some are indicators of self-purification processes. In this regard, all SMPs are regarded as indicators of biological pollution.
Group A of sanitary-indicative microorganisms. Includes inhabitants of the intestines of humans and animals. Microorganisms are regarded as indicators of faecal contamination. It includes BGKP - Escherichia, Enterococcus, Proteus, Salmonella. Also included in group A are sulfite-reducing clostridia (Clostridium petfringens and others), thermophiles, bacteriophages, bacteroids, Pseudomonas aeruginosa, candida, akinetobacter and aeromonads.
Group B of sanitary-indicative microorganisms. Includes inhabitants of the upper respiratory tract and nasopharynx. Microorganisms are regarded as indicators of oral contamination. It includes green, a- and (3-streptococci, staphylococci (plasma-coagulating, licitinase-positive, hemolytic and antibiotic-resistant; in some cases, the type of Staphylococcus aureus is also determined).
Group C of sanitary-indicative microorganisms. Includes saprophytic microorganisms living in the external environment. Microorganisms are regarded as indicators of self-purification processes. It includes proteolytic bacteria, ammonifying and nitrifying bacteria, some spore-forming bacteria, fungi, actinomycetes, cellulose bacteria, bdellovibrios, and blue-green algae.
The main groups of sanitary-indicative microorganisms
To the main sanitary-indicative microorganisms include BGKP, enterococci, proteas, salmonella, Clostridium perfringens, thermophilic bacteria and bacteriophages of enterobacteria (coliphages).
Bacteria of the Escherichia coli group
coli marked the beginning of the entire SPM group. The BGKP includes various representatives of the Enterobacteriaceae family. Depending on the purpose and object of the study, various requirements are imposed on the sanitary-indicative BGKP. They are conditionally divided into three subgroups and, under various circumstances, the fact of their presence is used for bacteriological characteristics of an object or substrate.
Subgroup I Escherichia coli includes BGKP, which are trying to identify, but which should not be in the study of objects and substrates that are "clean" in nature or become pure as a result of their processing (for example, thermal). The group of objects with such properties includes the following. Drinking (artesian, tap chlorinated, well) and distilled water (taken from a distiller or pipeline). Thermally processed food products (cutlets, sausages, fish, etc.). Analyze samples taken from the thickness of the product.
Milk(taken from the pasteurizer before entering the milk pipelines), soups, sauces, compotes, main courses (selected from boilers). Washouts selected during the control of the effectiveness of disinfection treatment in due time (not earlier than 45 minutes and not later than 1 hour after treatment).
Bacteria of this subgroup of Escherichia coli ferment lactose and glucose or only glucose to gas at 37 ° C and do not show oxidase activity. This subgroup includes Escherichia ha//, Klebsiella, Citrobacter, Enterobacter and other members of the Enterobacteriaceae family. Their presence is allowed in objects that do not belong to the category of "clean".
Subgroup II Escherichia coli includes CGBs indicating temporally undetermined faecal contamination. Microorganisms ferment lactose and glucose to acid and gas at 43-44.5 °C. This subgroup includes bacteria (E. coli, Klebsiella, citrobacter, enterobacter, etc.) that have retained the ability to form gas at elevated temperatures. Similar requirements are imposed on BGKP if it is impossible to protect the substrate from contamination. At the same time, one should limit oneself to determining only indicators of epidemiological distress. Such objects include: water from open reservoirs, wastewater, soil and all food products for which there is a high risk of contamination after heat treatment. In such cases, solid food products (surface layer), liquid food products, second and third dishes for distribution, washings from equipment and utensils are examined. Crops are cultivated at 43-44.5 °C. E. coli is differentiated from other bacteria by its ability to ferment lactose and glucose or only glucose.
Subgroup III Escherichia coli includes CGBs indicating fresh faecal contamination. A distinctive feature of this group of bacteria is the ability to break down lactose to gas at 43-44.5 "C.
In order to drink pure water, it must first of all be evaluated for the content of various kinds of inclusions. Even tap water can be contaminated. And the reason for this is the poor condition of the water supply system. Very often in water, especially untreated today, you can find all kinds of bacteria. And in order for the water to become drinkable, colimorphic bacteria in the water must be destroyed.
Is it really necessary to test the water?
Finding bacteria in water is not easy. All the same, there is a composition of water that is clearly regulated at the legislative and regulatory level, and the presence of some not entirely beneficial bacteria in it can not be seen or tasted. Therefore, everyone who builds a house, or just wants to buy for himself, is advised to analyze the water in order to determine its composition. And the presence of coliform bacteria in water will be an indispensable element of bacteriological analysis. Below is a summary table of standards for drinking water from central water supply. These are the norms that should be guided by the assessment.
As can be clearly seen from the table, there should be practically no bacteria in the water. Any presence of coliform bacteria in water, or any other, can cause mass epidemics. That is why their presence is banned. This can lead to the death of many people.
The entire list of harmful bacteria is quite extensive. It is difficult to identify all the harmful bacteria in water, which is why they came up with a more chemical-bacteriological one, which helps to identify harmful rod bacteria, as well. These harmful impurities can only be detected in the laboratory. It is impossible to identify them by taste, color and appearance.
Such bacteria appear in any warm-blooded creature. Including in the intestines of animals or humans. Where do they come from in the water? It's simple, if feces get into the water, then the development of such harmful bacteria is very possible.
Feces can also enter the water from sewers, cesspools, filter trenches. They can even appear in, due to the displacement of soil layers. The person operating the well may not notice this. Therefore, it is recommended to do a water analysis in the well after a while if there is no high-quality treatment system on the site.
According to sanitary standards, coliform bacteria in the water should not be at all. Therefore, at water supply stations there is always a disinfection stage, which is precisely concerned with the elimination of harmful bacteriological impurities.
The most popular options for removing bacteria from water are disinfection plants. Of course, disinfectants can also be dosed manually. But this is fraught with bad consequences. Because of this, manual labor in the operation of disinfecting plants has long been removed from the factories.
To eliminate the bacteriological threat at enterprises, dosing of chemicals is used. If the water will be used for drinking, then in this case, ultraviolet disinfectors are used, which work without harmful substances.
About bacteria in scientific language and in more detail
Coliform bacteria are also called very harmful. This group is one of the most harmful groups of bacteria. From the Enterobacteriaceae family, the coli group is culturally featured. A group of such bacteria is a sanitary indicator of fecal water.
In order, the following features of the behavior of Escherichia coli bacteria will be investigated below:
- The behavior of bacteria in a dense nutrient medium;
- Biochemical features
- Sustainability
- Sanitary values
Although this type of information is quite specific, it helps to visually trace all the features of the work of bacteria in water. How stable are they, what do they cause with their work in water, etc.
So, nutrient medium. Bacteria thrive in meat broth or agar. The sediment at the same time has a small size, but the growth of bacteria goes up sharply and a strong turbidity of the water appears.
Bacteria in the broth form a border, while there is no film on the surface. In color, a large accumulation of bacteria may have a gray-blue tint, sometimes the colonies may be red with a metallic sheen. Colonies of lactose-negative bacteria are most often colorless. In general, it is quite difficult to classify the bacteria of the coli group by color and behavior.
Now, as for the biochemical properties. Bacteria of this kind help to curdle milk, do not dilute gelatin. They have no oxidase activity.
To break down lactose can just the bacteria of Escherichia coli (lactose-positive).
As for the resistance of bacteria to various kinds of strong chemical disinfectants. To neutralize E. coli is quite simple. For this, standard pasteurization at a temperature of 65, at most 75 degrees, is sufficient. At a temperature of 60 degrees Celsius, E. coli is killed within 15 minutes. A 1% phenol solution removes the stick in 5 to 15 minutes. If you dilute the sublimate in proportions of one to a thousand, then the stick will be removed in 2 minutes. That is, removing such bacteria is not a problem.
The sanitary indicators of Escherichia coli bacteria have different meanings. If bacteria of this kind are found on fruits and vegetables in water or soil, this means only one thing - fresh fecal contamination occurs.
Tellingly, in the stomach of a person, if he uses antibiotics for a long time, E. coli bacteria are also formed. Lactose-negative bacteria are able to ferment lactose, and they are formed in large quantities in the intestine. This is how typhoid fever, dysentery are formed, just those diseases that manifest themselves when drinking water contaminated with Escherichia coli.
From the above, we can conclude. Coliform bacteria in water should be completely absent. Their presence in water threatens with epidemics and mass deaths. To avoid mass infection, you need to constantly monitor the composition of the water. Altering groundwater flows can lead to the formation of dirty streams.
There are only two ways to eliminate coliform bacteria from water. Use either disinfection or disinfection. The difference in concepts lies in the impact. It may be chemical or it may be physical. For chemical exposure using chlorine-containing elements can be used. But in this case, additional cleaning must be carried out. To eliminate excess chlorine from water, which also negatively affects human health.
The remaining options for the production of drinking water use ultraviolet emitters, which kill a group of E. coli bacteria with the help of. Without irradiating the water with harmful rays and leaving no traces behind.
Another disinfection option is the use of ozone - concentrated liquid oxygen. It quickly evaporates from the surface of the water, perfectly cleans it and has no residual effects in the water. Completely environmentally friendly. But it is difficult to manufacture and expensive.
Sanitary and epidemiological rules and regulations SanPiN 2.1.4.1074-01 “Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control." apply to water supplied by water supply systems and intended for public consumption for drinking and domestic purposes, for use in the processing of food raw materials and the production of food products, their storage and trade, as well as for the production of products requiring the use of water of drinking quality.
coliform bacteria
In order to drink pure water, it must first of all be evaluated for the content of various kinds of inclusions. Even tap water can be contaminated with bacteria. And the reason for this is the poor condition of the water supply system. Very often in water, especially untreated today, you can find all kinds of bacteria. And in order for the water to become drinkable, colimorphic bacteria in the water must be destroyed.
Finding bacteria in water is not easy. They cannot be seen or tasted. Any presence of coliform bacteria in water, or any other, can cause massive epidemics. That is why their presence is banned. This can lead to the death of many people. Typhoid fever, dysentery, just those diseases that manifest themselves when drinking water contaminated with Escherichia coli. To avoid mass infection, you need to constantly monitor the composition of the water.
Coliforms have long been considered useful microbial indicators of drinking water quality, mainly because they are easy to detect and quantify.
Common coliform bacteria
Thermotolerant fecal coliforms
According to SanPiN, thermotolerant fecal coliforms should be absent in 100 ml of the studied drinking water.
Thermotolerant fecal coliforms are microorganisms capable of fermenting lactose at 44°C or 44.5°C.
Secondary growth of faecal coliforms in the distribution network is unlikely unless sufficient nutrients are present (BOD greater than 14 mg/l), water temperature is above 13°C and there is no free residual chlorine. This test cuts off the saprophytic microflora.
Coliforms may indicate the ingress of pathogenic microorganisms into the water. Intestinal pathogenic diseases are widespread throughout the world. Among the pathogens found in contaminated drinking water, strains of Salmonella, Shigella, enteropathogenic Escherichia coli, Vibrio cholerae, Yersinia, enterocolitics, campylobacteriosis are found. These organisms cause diseases ranging from mild gastritis to severe and sometimes fatal forms of dysentery, cholera, and typhoid fever.
Other organisms that are naturally present in the environment and are not considered pathogenic agents can sometimes cause opportunistic diseases (i.e., diseases caused by opportunistic microorganisms - Klebsiela, Pseudomonas, etc.). Such infections most often occur in people with impaired immune systems (local or general immunity). At the same time, the drinking water used by them can cause a variety of infections, including lesions of the skin, mucous membranes of the eyes, ear, and nasopharynx.
Do not put yourself and your loved ones in danger, use only tested water!
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The presence of coliform bacteria is also determined in water of all kinds. Thermotolerant coliform bacteria quickly die off in the external environment, so their detection indicates fresh fecal contamination of water.
To determine coliform bacteria in drinking water and purified water, the method of membrane filters is used. The number of lactose-positive colonies grown on the filters, identified as coliform bacteria, is counted.
In the absence of common coliform bacteria, glucose-positive colimorphic bacteria (GBC) are determined with an oxidase test.
For example, the main indicator of fecal contamination is coliform bacteria, their determination is carried out in washings from hands, workwear of personnel, laboratory glassware, in non-sterile dosage forms, injectable solutions and eye drops before sterilization. The air is evaluated by the content of Staphylococcus aureus, which enters it from the upper respiratory tract, the oral cavity. It is considered an indicator of droplet air pollution. Other microbes that reflect the sanitary problems of a particular object are yeast and mold fungi, Pseudomonas aeruginosa, and salmonella.
The effectiveness of the disinfection process is determined by the analysis of a group of coliform bacteria, which are indicators of water quality. The sensitivity of bacteria to chlorination is well known, while the effect of chlorination on protozoa and viruses is not entirely clear. Protozoan larvae and intestinal viruses are more resistant to chlorine than coliforms and other intestinal bacteria. However, there is very little evidence that current water treatment practices are deficient. There have been no documented outbreaks of disease associated with the consumption of water containing viral or protozoal infections.
The given data show how statistically significant the increase in the content of coliform bacteria is.
When determining water quality, it is necessary to calculate the amount of coliform bacteria present to determine if the water meets established standards. A variety of fermentation tubes are used to count positive coliform tests (presumptive, confirmatory, and fecal). When calculating, the method of statistical processing of the results of analyzes carried out with serial dilution of the sample is used. For example, MPN 10 means that there are 10 coliform bacteria per 100 ml of water.
Natural purification leads to a decrease in turbidity, color and coliform bacteria content, as well as to the elimination of daily fluctuations in quality indicators. On the other hand, algae growth can lead to an increase in turbidity and the formation of stubborn tastes and odors in summer and autumn. Chlorination can be both a preliminary and last (secondary) stage of water treatment, ensuring the disinfection of raw water and establishing the proper concentration of residual chlorine in treated water. Intensive pre-chlorination and water treatment with activated carbon are used to remove compounds that cause tastes and odors from water. The special chemical compounds used in coagulation are selected depending on the properties of the water and on the basis of economic considerations. River water usually requires an extensive complex of treatment facilities with great operational flexibility due to daily fluctuations in water quality. The pre-treatment step often consists of pre-settling to reduce the amount of sludge and sedimentable organic matter prior to chemical treatment. As shown in fig. 7.2, in many river water treatment facilities, chemical coagulation and sedimentation are carried out in two stages in order to achieve a greater degree of purification and flexibility in the operation of facilities. Depending on certain factors, up to twelve different chemical compounds can be used to obtain a satisfactory quality of treated water.
In the sanitary assessment of the quality of groundwater, the absence of coliform bacteria in the composition of water was usually considered a sign of the absence of pathogens.
Nearly all states now require testing of treated water for coliforms; in this case, the number of tests required depends on the population served. Fecal coliform enumeration, although not usually mandatory from the point of view of regulatory authorities, is not difficult and can provide additional insight into sources of pollution. Sometimes specific plant-specific limits are set for certain parameters such as residual chlorine, turbidity, dissolved solids, nitrate, and color. The residual chlorine concentration in the distribution system is measured to determine if the chlorination is sufficient. Other laboratory analyzes are related to the control of chemical treatment, the identification and elimination of some problems that occur in distribution system facilities, and consumer complaints about water quality. Chemical reagents should meet the requirements of the relevant specifications and should be subjected to conventional analyzes, with a penalty imposed on the supplier if they deviate from the specifications. For example, lime is typically purchased at 88-90% CaO, alum at 17% A12O3, and activated carbon at phenol specifications. If the contract for the supply of chemicals provides for the imposition of fines on the supplier based on the results of laboratory tests, this can protect the water treatment plant from entering it with poor-quality materials.
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 method of disinfection has recently been recommended only for short-term or emergency disinfection of water.
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 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.
