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The total volume of water on the globe is about 1.5 billion km3. At the same time, 93.96% of the water is concentrated in the seas and oceans. Fresh water accounts for less than 6% of available water resources. It is believed that only 0.2-0.3% of all water on Earth can be used for drinking purposes.
One of the current problems is the shortage of drinking water. This problem arose in connection with the growing population of the globe, the intensive consumption of water by humans, pollution of water sources by industrial emissions, chemicalization of agriculture, etc.
Effective measures to reduce the shortage of drinking water are to reduce the use of water supply for the technological needs of enterprises, reduce unproductive water losses associated with a malfunction of the water supply system, and the installation of closed circulating water supply systems.
Sources of water supply can be surface, groundwater and atmospheric water.
The main hygiene requirements for the water source are that the quality of the water in its natural state or after treatment guarantees against the danger of the spread of infectious diseases, from contamination with toxic and radioactive substances in doses that are harmful to health, and with respect to organoleptic properties, satisfy the requirements of the population.
Surface water sources are rivers, lakes, artificial reservoirs, as well as seas and oceans. The water in them varies in physical properties, in the content of organic, mineral substances and microorganisms, the ability to self-purify, and to renew water resources.
Most often rivers are used for water supply. River waters have the greatest abilities for self-purification, renewal of runoff, high flow rate, and stability of the mineral composition. However, the rivers are most polluted by anthropogenic impurities, because they are most often used for the discharge of fecal water, industrial and agricultural wastewater. In large quantities, flood and storm water enter them, and in hot weather the volume of water in them decreases.
More stable water sources include artificial reservoirs. However, due to a sharp slowdown in the movement of water in them, water exchange decreases, which contributes to the accumulation and deposition of organic substances, the development of anaerobic microflora, flowering of water, the formation of bottom sediments and silt. A characteristic feature of the reservoirs is the mineralization of water due to its intensive evaporation from the surface of the reservoir, the uneven layer-by-layer distribution of dissolved salts at various depths.
Natural lakes also have similar disadvantages, the water of which is even more prone to the accumulation of organic substances and putrefactive microorganisms.
The waters of open reservoirs are usually characterized by a large number of suspended particles, increased turbidity, significant organic and bacterial pollution, expressed seasonal changes in water quality and therefore can be used for drinking purposes only after appropriate treatment.
A promising and almost unlimited source of water remains the seas and oceans.
However, sea water has high salinity, reaching 10–20 g / l in the Baltic Sea, 17–18 g / l in the Black Sea, and up to 10 g / l in the Caspian Sea. The seas have a high level of microbial and organic pollution in the coastal zone. Along with disinfection, seawater must be desalinated.
Groundwater is formed by filtering atmospheric precipitation and surface water through the soil. The sanitary state of groundwater depends on the depth of their occurrence, the nature of the soil and the intensity of pollution. They are divided into ground and interstratal waters.
Groundwater - soil water penetrating to the first water-resistant layer. When passing through the soil, they are filtered. Groundwater is characterized by high salinity, reflecting the chemical composition of local soil. They practically do not contain microorganisms, have a low temperature and a pleasant taste. However, with a small thickness of the soil, as well as its mechanical disturbance, there is not enough purification of groundwater and is not suitable for drinking purposes.
Interstratal waters - are located between watertight strata below the first water-resistant soil layer. These waters are the most stable and reliable in sanitary and epidemiological terms. The depth of their occurrence is from tens to thousands or more meters. Interstratal waters have a stable chemical composition, higher mineralization, increased content of macro- and microelements (calcium, magnesium, iodine, fluorine, etc.), low stable temperature, and good organoleptic properties. Interstratal waters are usually transparent, colorless, odorless and tasteless, practically free of microorganisms, and therefore suitable for drinking purposes without prior purification. In some cases, they are highly mineralized and require softening.
Interstratal water, which is under pressure and rises under natural pressure, is called pressure or artesian. The formation of pressure water is explained by the peculiarities of geographical and geological structures in vast territories (elevation, depressions, slopes of the water-resistant layer), which provide hydrostatic water pressure. In this case, a natural violation of the water-resistant layers and the formation of springs and keys are possible. Artesian waters are considered the cleanest waters.
Atmospheric waters - precipitation in the form of rain and snow. Used in the arid southern regions, in the Arctic zone, as well as in extreme conditions. Rain and snow waters are soft, low mineralized. However, the high level of atmospheric pollution in modern conditions, especially in large industrial centers, leads to precipitation contamination with soluble toxic substances, solid aerosols and microorganisms. It was found that 1 liter of rainwater washes 325,000 dm3 of atmospheric air. The precipitates contain ions of sulfuric and nitric acids, carbon dioxide, carcinogenic and radioactive impurities. It is estimated that on rainy days 9 times more radioactive substances fall on the Earth's surface than in dry weather. Thus, precipitation water cannot be considered clean and must be specially treated.
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- Hygienic characteristics of water sources
Sources of water for a centralized drinking water supply system can serve as fresh surface water bodies (rivers, lakes, reservoirs, canals, etc.), and groundwater (interstratal - pressure and non-pressure). In conditions of decentralized (local) water supply, underground (ground) water, as well as springs, are more often used. In the arid zone in the absence of others
- The choice of source for drinking water
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- Hygienic characteristics of water sources
There are three types of origin and localization of water: underground, surface and atmospheric. Groundwater is formed from atmospheric precipitation passing through the soil and lingering on waterproof layers of clay or granite (Fig. 2.2). According to the occurrence conditions, there are distinguished ground, interstratal pressureless and interstratal pressure (artesian) waters. Groundwater accumulates on
- WATER HYGIENE AND SANITARY PROTECTION OF WATER SUPPLIES
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- Water supply systems
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- Rural water supply
When choosing a source of centralized water supply, preference is given to groundwater. When artesian waters are insufficient or they cannot be used in terms of quality, water pipelines from open reservoirs (rivers, lakes, reservoirs), irrigation and watering canals are arranged. The water intake site is located above the settlement along the river (canal), it should be
- Use in water supply
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- Sanitary and epidemiological requirements for water supply of food facilities
Water supply of food facilities can be carried out by various systems. The local water supply system is the construction of mine and tubular wells, mainly in rural areas. The sources of water for this system are groundwater, which is used without prior treatment. The hygienic characteristics of the wells depend on the depth of the aquifer and protection measures