Biological soil pollution is a component of organic pollution caused by the presence of pathogens of infectious diseases, as well as harmful insects and mites, carriers of pathogens of human, animal and plant diseases.
Few infectious agents live in clean soil. These are mainly causative agents of wound infections (tetanus, gas gangrene), botulism and anthrax. These spore microorganisms can remain in the soil in a viable state for 25 years.
Pathogens enter the soil with excretions of humans and animals, with wastewater from medical institutions, etc. In clean soil, they usually die quickly. However, in soil intensively contaminated with organic matter and containing chemicals, self-purification processes are disrupted. The soil, which is constantly contaminated with organic matter, always contains pathogens of intestinal infections (dysentery, typhoid fever), the survival time of which can range from several months to one and a half years.
Contaminated soil is a favorable place for the development of flies. Sanitary and entomological indicators determined in the soil are the larvae and pupae of synanthropic flies. Synanthropic flies (house flies, house flies, meat flies, etc.) have important epidemic significance as mechanical carriers of pathogens of a number of infectious and invasive human diseases (cysts of intestinal pathogenic protozoa, helminth eggs, etc.). The period of development of a fly from larva to sexually mature individual is 4-7 days.
The presence of larvae and pupae in the soil of populated areas is an indicator of the unsatisfactory sanitary condition of the soil and indicates poor cleaning of the territory, improper sanitary and hygienic collection and storage of household waste and their untimely disposal. Soil contaminated with organic substances promotes the proliferation of rodents, which are sources and carriers of particularly dangerous zoonotic infections (plague, tularemia).
50.Hygienic importance of cleaning populated areas. Sewerage.
An important hygienic and anti-epidemic task is the cleaning of populated areas from waste generated in the process of industrial, economic and household activities of humans. There are liquid waste (sewage, water from cooking, washing dishes, laundry, wastewater from industrial and commercial enterprises) and solid waste (garbage, food leftovers, household waste, etc.). Waste can contain pathogens of infectious diseases and contaminate soil and water with them, and serve as a breeding ground for flies. The most preferable system for removing liquid waste from a hygienic point of view is sewerage. Sewerage is a floating system in which sewage diluted with water is floated through pipelines outside populated areas. Sewerage is constructed only if there is a water supply. With a common sewage system, atmospheric (rain, melt) water is also removed through pipelines along with domestic and industrial water. With a separate system, wastewater flows to a treatment plant, and precipitation through the rain network is removed directly into the reservoir.
Sewerage. A) General(single pipeline network for all drains)
b) Separate(two pipe systems: 1. for fecal and industrial wastewater 2. For atmospheric wastewater)
The main source of soil contamination by pathogenic microorganisms and helminth eggs are physiological wastes of humans and animals, wastewater, etc.
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Over time, as a result of soil self-purification processes, they die off, but retain their viability in it for a significant period.
Almost permanent and long-term inhabitants of the soil are spore-forming pathogenic microorganisms, the spores of which remain viable in the soil for decades. Basically, these are pathogens wound infections(tetanus, gas gangrene), botulism, anthrax.
Soil, especially contaminated with organic matter, should be a factor in the transmission of bacterial and viral pathogens intestinal infections- dysentery, typhoid fever, paratyphoid fevers A and B, salmonellosis, viral hepatitis, pseudotuberculosis, etc.
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The survival time of these pathogens in the soil can vary from several days to several months. Thus, bacteria of the typhoid-paratyphoid group can remain in the soil for up to 400 days, dysentery - up to 100 days.
The soil may become contaminated opportunistic microorganisms, coming with human secretions (coliforms, E.coli, B.cereus, Proteus, Cl.perfringens, etc.).
Soil plays a specific role in transmission geohelminths(roundworms, whipworm). The specific role is determined by the extreme importance of geohelminth eggs getting into the soil with human secretions, where they undergo a certain development cycle and acquire invasive properties. Only after “ripening” in the soil are ascaris eggs capable of causing invasion (disease) in humans. Ascaris eggs can remain viable in the soil for up to 1 year; with soil particles they can infect food products that are used as food without heat treatment.
Soil contaminated with organic matter provides habitat rodents, which are sources of such dangerous infections as rabies, plague, tularemia, etc., as well as a favorable place for the development flies, which can transmit pathogens of intestinal infections (Fig. 1).
Epidemiological significance of soil - concept and types. Classification and features of the category "Epidemiological significance of soil" 2017, 2018.
1. Rodents infect the soil with leptospirosis. 2. Ticks are carriers of vector-borne infections 3. Soil is a medium for the development of larvae of flies, horseflies, and fleas. Soil self-purification - transformations aimed at restoring the original state of the arable layer of the earth. The process... [read more] .
The main source of soil contamination by pathogenic microorganisms and helminth eggs are physiological wastes of humans and animals, wastewater, etc. Over time, as a result of soil self-purification processes, they die off, but retain their viability in it for a significant period.
Almost permanent and long-term inhabitants of the soil are spore-forming pathogenic microorganisms, the spores of which remain viable in the soil for decades. Basically, these are pathogens wound infections(tetanus, gas gangrene), botulism, anthrax.
Soil, especially contaminated with organic matter, can be a factor in the transmission of bacterial and viral pathogens intestinal infections- dysentery, typhoid fever, paratyphoid fevers A and B, salmonellosis, viral hepatitis, pseudotuberculosis, etc. The survival time of these pathogens in the soil can range from several days to several months. Thus, bacteria of the typhoid-paratyphoid group can remain in the soil for up to 400 days, dysentery - up to 100 days.
The soil may become contaminated opportunistic microorganisms, coming with human secretions (coliforms, E.coli, B.cereus, Proteus, Cl.perfringens, etc.).
Soil plays a specific role in transmission geohelminths(roundworms, whipworm). The specific role is determined by the need for geohelminth eggs to enter the soil with human secretions, where they undergo a certain development cycle and acquire invasive properties. Only after “ripening” in the soil are ascaris eggs capable of causing invasion (disease) in humans. Ascaris eggs can remain viable in the soil for up to 1 year; with soil particles they can infect food products that are used as food without heat treatment.
Soil contaminated with organic matter provides habitat rodents, which are sources of such dangerous infections as rabies, plague, tularemia, etc., as well as a favorable place for the development flies, which can transmit pathogens of intestinal infections (Fig. 1).
3.1. Sanitary and epidemiological requirements for water supply to food facilities
Water supply to food facilities can be carried out by various systems.
Local system water supply is the installation of shaft and tube wells, mainly in rural areas. The water sources for this system are groundwater, which is used without preliminary treatment. The hygienic characteristics of wells depend on the depth of the aquifer and measures to protect water from possible contamination. Tube wells (small-tube, artesian) meet hygienic requirements to a greater extent than shaft wells, since their design more reliably isolates water from surface contaminants.
In the absence of centralized water supply, it is equipped local water supply, which is fed from a deep mine or artesian well. The shaft well is located at a distance of at least 20 m from production premises and at least 100-150 m from possible sources of pollution. The well frame is raised above the ground by at least 0.6 m and tightly closed with a lid. A “clay castle” with a width of at least 1 m and a depth of up to 2 m is installed around the log house. Paved slopes with a slope of 0.1 m and a width of 2 m are arranged near the well.
Centralized system water supply is the installation of central water supply systems, which provides for the purification and disinfection of water at water supply stations before it enters the water supply pipes. The source of water supply when installing water pipelines, as a rule, is open reservoirs, and in small settlements - groundwater.
To prevent contamination of water intake sites and water supply structures, they are installed around them. sanitary protection zone.
A sanitary protection zone is understood as a territory where a special regime has been established and measures are taken aimed at preventing periodic or systematic pollution that can deteriorate the quality of water. The entire sanitary protection zone is divided into two zones: first belt - strict security zone, is designed to protect the place of water intake and the head structures of the water supply system. It is fenced and guarded; living and construction are prohibited on it. IN the second zone is a restricted zone, establishing a restrictive regime according to which construction is allowed only in agreement with the sanitary authorities.
To protect the water supply network from contamination, the impermeability of pipes, insulated joints, inspection wells, etc. is provided. Water pipes must be laid below the freezing level of the soil. When crossing the lines of the domestic and drinking water supply with sewer collectors, the former must be located above the latter at a distance of at least 0.4 m. If the intersection occurs at a shorter distance and the water supply is laid below the sewer level, then steel pipes are used for the water supply instead of cast iron, and for sewerage - cast iron instead of ceramic. At the intersection, water pipes are protected with a special case in clay soil - at least 5 m long in each direction, in filter soil - 10 m.
Water supply for catering establishments. Public catering establishments, regardless of their form of ownership, capacity, or location, are equipped with internal water supply systems. Water supply is carried out by connecting to a centralized water supply system, and in its absence, an internal water supply system is equipped with water intake from an artesian well or well. A sanitary and epidemiological conclusion is required for water supply sources of newly built, reconstructed and existing organizations.
The amount of water must fully meet the needs of the enterprise. The following water consumption standards are provided for the preparation of 1 ton of semi-finished products in public catering: meat - 1500 l, fish and vegetables - 2200 l, culinary - 1000 l. The calculated second water consumption and the percentage of simultaneous operation of the equipment are presented in table. 9.
Table 9
Estimated second water consumption
and the percentage of simultaneous operation of equipment
The quality of water used in public catering establishments must meet the hygienic requirements for household and drinking water.
In the event of any failure of the water supply network or during repair work, it is prohibited to use water from this water supply system. After repairs, the water supply network must be disinfected, and the water must be taken for bacteriological analysis.
In addition to cold water, food establishments must be provided hot water of appropriate quality.
According to the method of supply from the cold water supply network, open and closed hot water supply systems are distinguished, which are arranged with upper and lower wiring. For sanitary and hygienic reasons, it is preferable to install lower wiring in an underground channel or under the basement ceiling.
Hot water is supplied to washing machines and bathtubs, industrial sinks, showers, washbasins, to watering taps for washing wastewater treatment facilities (grease traps, dirt sumps and pulp collection tanks), as well as to the waste chamber for washing tanks. The minimum temperature of hot water must be at least 65 o C; to obtain a higher water temperature, special local heating devices are provided.
All production workshops must be equipped with sinks with cold and hot water supply. At the same time, mixer designs are provided that prevent contamination of hands.
If necessary, food enterprises are equipped with a steam supply system to disinfect equipment, containers, flasks, etc.
In cases where the amount of drinking water is limited, it is allowed to install a separate water supply network for technical needs, which must be completely separate from the drinking water supply. In such cases, it is allowed to supply process water to refrigeration units, vacuum pumps, barometric condensers, heating appliances, etc. It is prohibited to use hot water from a water heating system for technological, household purposes, as well as for processing technological equipment, containers, inventory and premises .
3.2. Sanitary and epidemiological requirements for sewerage
Soil self-purification
Without the self-cleaning properties of the soil, with its constant contamination by waste products of people and animals, it would become impossible to live on Earth. Soil self-purification is understood as its ability to convert hygienically hazardous organic substances into inorganic ones - mineral salts and gases that are absorbed by vegetation.
The self-purification process goes through two stages: the first stage is decay (decomposition), the second is the synthesis of organic substances (humus). During the mineralization of organic substances, ammonia and ammonium salts are formed, of which nitrites are formed, then nitrates, which are considered the final products of self-purification: they are able to be absorbed by plants. In parallel, the synthesis of humic acids, also harmless in a sanitary sense, continues.
Self-purification of the soil begins with the fact that organic substances that entered it along with pathogenic bacteria and helminth eggs are filtered through it and adsorbed by it. Pollutants under the influence of biochemical, biological, geochemical and other processes, passing through the soil, lose color (fade) and unpleasant odor, toxicity, virulence and other negative properties. The decomposition and mineralization of organic matter in the soil occurs with the active participation of microorganisms contained in it. These processes can last both aerobically (with air oxygen necessary for the life of aerobic bacteria) and anaerobically (without oxygen, with the help of putrefactive bacteria). From a hygienic point of view, aerobic decomposition of organic substances is better: in this case, unpleasant-smelling gases are not formed, and the hygienic quality of air and water does not deteriorate.
Self-purification is more intense in soil with a high oxygen content in the air of its pores. For example, in a pile of garbage, where there is no access to oxygen, rotting processes predominate. In soils that are slightly polluted by waste (little waste and cleaner soil), self-purification processes proceed to completion, ending with mineralization and the formation of humus.
At the same time, it should be remembered that the self-purification mechanism stops functioning when the soil is overloaded with polluting agents, especially substances that take a long time to decompose.
Epidemiological significance of soil
Soil is an extremely favorable environment for the habitat of bacteria, actinomycetes, fungi, algae, lichens, and simplex. 1 g of soil contains from 500 to 500,000 simple organisms. The safety of the soil, its possible adverse effects on the human body, and its health depend on the content and quality of contamination by microorganisms.
Microbes of anthrax, typhoid fever, dysentery, infectious hepatitis and other intestinal infections can survive in the soil for a long time. If pathogens of infectious diseases are present, soils are divided into groups:
Soils with microorganisms that constantly live in their thickness (pathogens of gas gangrene, anthrax, tetanus, botulism, actinomycosis)
Soils with microorganisms that are temporarily located in their thickness (pathogens of intestinal infections, typhoid-paratyphoid diseases, dysentery, cholera)
Soils with microorganisms that can be present in them either permanently or temporarily (tuberculosis, tularemia).
The soil may also contain pathogenic viruses - polio, ECHO, Coxsackie.
The bulk of microorganisms die when they enter the soil, but individual microbes can survive in it for a long time. The typhoid bacillus is viable in the soil for more than 13 months, the diphtheria bacillus - from 1.5 to 5 weeks, etc. The survival of microorganisms depends on the type of soil, humidity, temperature, the presence of a biological substrate on which they develop, and the influence of antagonism of microorganisms. The anthrax pathogen persists in the soil longer.
There may be helminth pathogens in the soil. There are geo- and biohelminths. For the former, soil is the environment in which eggs develop to the invasive stage (roundworms), as well as a factor in the transmission of the disease. Biohelminths include roundworms, pinworms, whipworms, and hookworms. Helminth eggs survive in the soil for an average of 1 year, although in the experiment they remain viable only for three months.
The role of soil in the transmission of pathogenic anaerobes deserves the greatest attention. The causative agents of tetanus, gas gangrene and botulism, which are intestinal saprophytes of warm-blooded animals and humans, enter the soil with feces, form spores there, and remain viable for years. In populated areas without asphalt (or paved) streets and sewerage, soil contamination by bacteria and helminth eggs in yards and on the street can be significant, especially in shaded areas. The survival period in soil for pathogens of dysentery, typhoid fever, paratyphoid fever, cholera and purulent infections is usually several weeks, sometimes months. This depends on the physical properties of the soil, the availability of nutrients, microclimate and interspecific competition.
In the case of direct contact of a person with soil through damaged skin, one can develop tetanus and gas gangrene, the causative agents of which are among the spore-bearing anaerobes and are constantly present in the soil. Tetanus spores are most often found in garden soil fertilized with manure, as well as in other places contaminated with animal excrement. Therefore, grazing in rural stadiums is unacceptable.
With various traumatic injuries to the skin, along with soil particles and dust, for example, tetanus spores enter the body, which can cause
diseases. For the purpose of prevention, it is necessary, even with minor damage to the skin and contact with soil, to administer anti-tetanus serum. Athletes should remember this, as skin damage may occur during competitions. During sports activities with contaminated floors, it is also possible for the skin to become infected, which requires regular wet cleaning to prevent.
In modern conditions, the hygienic importance of soil is increasing for creating optimal sanitary living conditions for the population, both in the location of cities and villages, their planning, and in the use of large land masses for various spheres of human activity, including for sports (creation of sports grounds). In preventing the negative impact of soil on people's health, landscaping and proper sanitary and hygienic maintenance of populated areas, as well as sewage systems, asphalting (paving), landscaping, systematic cleaning and watering of streets and courtyards, sanitary soil protection and rationally organized cleaning of territories are of decisive importance. from garbage.
Qualitative criteria for sanitary and hygienic assessment of soil:
1. Sanitary and chemical criteria. This includes the Khlebnikov sanitary number - the ratio of humus nitrogen to total nitrogen. Total nitrogen is the sum of humus nitrogen and pollutant nitrogen. The soil is considered clean if the sanitary number approaches 1. For the sanitary and hygienic assessment of the soil, it is important to know the content of such pollution indicators as nitrites, ammonia salts, nitrates, chlorides, and sulfates. their concentration should be compared with the control for the given area. The soil air is assessed for its hydrogen and methane content, along with carbon dioxide and oxygen.
2. Sanitary and bacteriological indicators. These include titers of microorganisms. The soil is considered clean if the titer of coli bacteria does not exceed 4.0. Based on the content of microorganisms, one can determine the age of fecal contamination: fresh, when E. coli appears in the soil, old - clostridia.
3. helminthological assessment. Clean soil should not contain helminths and their eggs and larvae.
4. Sanitary entomologist. The number of fly larvae and pupae is counted.
5. Algological indicators: in clean soil yellow-green algae predominate, in polluted soil blue-green and red algae predominate.
6. radiological indicators: you need to know the level of radiation and the content of radioactive elements.
7. Biogeochemical indicators - content of chemicals and microelements.
When assessing the content of chemical substances per pound, the limit of the amount of substances is allowed at which their migration from soil to plants, groundwater, and atmospheric air will not exceed the maximum concentrations established for these environments
Soil as an environmental factor influences human health. The soil consists of mineral and organic substances, organomineral complexes, soil microorganisms, as well as soil moisture and air. The most important component of the soil is humus, which determines its fertility.
The nature of the soil (rocky, sandy, clayey, etc.) and its physical properties (porosity, water capacity, air and moisture permeability, capillarity) must be taken into account when choosing a site for the construction of public catering establishments. The water capacity of the soil, i.e. its ability to hold water, determines the level of groundwater. Soil air permeability is important for self-purification processes, since the influx of oxygen promotes the rapid oxidation of organic substances.
The great hygienic importance of soil as an element of the biosphere is that it not only accumulates various wastes, but is a natural environment for their neutralization. It is used for the neutralization of municipal solid waste (MSW), storage of industrial solid waste (ISW), treatment and neutralization of wastewater in aeration fields, irrigation, etc. Into the soil
pesticides and mineral fertilizers are applied. As a result of human economic activity, a wide variety of chemicals enter it, including those that pose a danger to human health.
Processes aimed at restoring the natural state of the soil are called soil self-purification processes. Organic substances that have entered the soil in the form of proteins, fats, carbohydrates and their metabolic products undergo decomposition under the influence of microorganisms down to inorganic substances (mineralization process). At the same time, humus is formed in the soil - a complex organic substance of the soil that ensures soil fertility. Mineralization of the final products of protein breakdown is accomplished with the help of nitrifying bacteria with the formation of nitrates. Soil self-purification processes lead to the liberation of soil from biological contaminants, the death of microorganisms and helminth eggs.
The important hygienic significance of soil also lies in the fact that the soil forms the chemical composition of food products consumed by humans, drinking water and partly atmospheric air. Increased or decreased concentrations of fluorine, iodine, manganese, selenium and other chemical elements lead to the formation of natural or artificial geochemical provinces that play a leading role in the occurrence of endemic diseases - fluorosis, endemic goiter, etc.
The largest number of microorganisms are found in the soil at a depth of 5...10 cm. The permanent inhabitants of the soil are spore-bearing aerobic and anaerobic bacteria, as well as other bacteria that take part in self-purification processes.
The epidemiological danger of the soil is that pathogenic spore-bearing anaerobes, the causative agents of tetanus and gas gangrene, constantly live in it; spores of the causative agent of anthrax and botulinum bacillus persist for years, causing serious human diseases. Soil contaminated with human feces may contain pathogens of acute intestinal infections. Contaminated soil can act as a factor in the transmission of typhoid and paratyphoid fever, salmonellosis, bacterial and amoebic dysentery, cholera, viral hepatitis A, polio, tuberculosis, yersiniosis, giardiasis and geohelminthiasis (ascariasis, trichuriasis, etc.). The survival period of bacteria of the typhoparatyphoid group in soil is on average about 2...3 weeks, and under favorable conditions several months. Mycobacterium tuberculosis and polio viruses can survive in soil for more than 3 months. Geohelminth eggs (roundworm and whipworm) undergo a maturation stage in the soil to the state of invasiveness, i.e., the ability to infect humans, within 2...3 weeks to 2...3 months. The survival time of the eggs of these helminths in the soil can be up to 7...10 years.
The epidemiological significance of contaminated soil also lies in the fact that flies, which are carriers of pathogens of intestinal infections, develop and breed in it. Rodents often live in the soil, infecting the soil with pathogens of leptospirosis, tularemia, yersiniosis, etc.
In the process of selecting a site for construction and during operation of the enterprise, it should be taken into account that the soil’s ability to self-purify is limited. Protecting the soil, cleaning it from pollution, sanitary improvement, and fighting insects and rodents are of great hygienic importance.
In order to determine the quality and degree of safety of the soil in populated areas, resort areas and other significant areas, a hygienic assessment of the soil is carried out with the drawing up of a sanitary and epidemiological report on its condition and suitability for construction.
Maximum permissible concentrations of chemicals have been established for soil, including heavy metals, pesticides, petroleum products, etc. Clean soil should be free of pathogenic bacteria, geohelminth eggs, fly larvae and pupae, index (quantity) of coliform bacteria (coliforms) and index Enterococci should not be higher than 10 per gram of soil.