Water
Water is one of the important elements of the environment. Water has physiological, sanitary-hygienic, industrial and epidemiological significance for humans. The use of non-standard water can lead to the violation of the sanitary regime of production, the release of a low-quality product, and can also be the cause of infectious diseases, food poisoning, helminthosis, etc.
The physiological importance of water for humans lies in the fact that it is part of all biological tissues. 60-70% of the body's mass is water, it is a component of blood, various secretions (eg gastric juice, bile) and excreta (the final product of metabolism, which is expelled from the body). Water contains not only the liquid area, but also dense tissues. The water content in tooth enamel is 0.2%, in bones - 22%, in adipose tissue - 30%, in the liver - 70%, in skeletal muscles - 76%, in the gray matter of the brain - 86%. All biochemical reactions and physiological processes take place in an aqueous environment. It is a universal solvent, participates in salt exchange, maintenance of osmotic pressure, acid-alkaline balance, thermoregulation. Water transports many salts, trace elements, vitamins and nutrients. At the same time, it participates in the excretion of toxic substances in urine, sweat and other forms.
A person's physiological need for water is about 2.5-3 liters per day. Under normal conditions, the amount of liquid to drink is 1-1.5 L/day-night, in addition, 1-1.2 L of water enters the body with food products, as well as 0.5 L of water is produced in the body as a result of the oxidation of nutrients. In the heat and during intense physical exertion, due to increased sweating, the need for water can increase to 10-12 L per day, which leads to dehydration and the release of Na and K salts, as well as water-soluble vitamins from the body.
The human body can hardly tolerate dehydration: 10% water loss leads to metabolic disorders, and 20-22% - causes death.
The sanitary-hygienic importance of water - water is the leading indicator of the sanitary well-being of the population. Humans need a large amount of water for household and drinking purposes: cold and hot water supply, drinking water, for cooking, washing dishes, wet cleaning, laundry, sewage, street cleaning, etc. Thus, the cost of water per capita per day in the form of drinking water and for household needs is approximately 200 to 400 L.
Industrial significance - water is a valuable technological raw material. For example, 1500 m3 of water is needed to grow 1 ton of wheat, 2000 m3 to produce 1 ton of meat, etc.
Epidemiological importance - according to the data of the experts of the International Health Organization, it is determined that 80% of infectious diseases in the world are related to the unsatisfactory quality of drinking water and the violation of sanitary and hygienic norms of water supply.
The main infectious diseases that are transmitted through water:
1) intestinal infections of bacterial nature - cholera, typhoid fever, paratyphoid А and В, dysentery, various types of enteritis and enterocolitis;
2) viral diseases - infectious hepatitis (botkin), poliomyelitis, adenoviral and enteroviral diseases caused by type A virus;
3) bacterial zoonotic infections - tularemia, brucellosis, tuberculosis, anthrax;
4) protozoan invasions (diseases caused by protozoa) - lambliosis, amebiasis;
5) Infestations caused by geohelminths develop without an intermediate host (ascaridosis, ankylostomosis, bronchiloidosis) and with biohelminths, pass the larval stage in the organism of the intermediate host - domestic animals, molluscs, crustaceans, fish (pig solitaire, liver fluke, opisthorchosis, etc.).
The causative agents of the disease are found in domestic water bodies and industrial sewage waters. Contamination of drinking water can occur during various types of accidents. Infection occurs most often when open contaminated water bodies are used for washing dishes, fruits and vegetables.
In addition to infectious diseases, water can be the cause of non-infectious human diseases (endemic, gout, fluorosis, caries, etc.), which are related to the violation of the natural chemical composition of water.
Sources of water supply can be surface, underground and atmospheric waters.
The main hygienic requirement for water sources is that the quality of water in natural conditions should be guaranteed, we should be protected from the danger of spreading infectious diseases, from contamination with poisonous and radioactive substances harmful to health, and according to the organoleptic properties, it should meet the requirements of the population. The quality of drinking water determines the health and epidemiological safety of the population. Drinking water should have pleasant organoleptic properties, should be harmless in terms of chemical composition, safe from the epidemiological and radiation point of view.
Organoleptic indicators of drinking water - drinking water should have good organoleptic properties - it should be hard, colorless, colorless, without taste and smell, have a cooling temperature and should not contain visible impurities.
Water temperature - the optimal water temperature for human physiological needs is 8-15оС. It exhibits a pleasant cooling effect, quenches thirst better, is quickly absorbed, stimulates the secretory and motor function of the gastrointestinal tract. Water with a temperature of 25oС does not satisfy thirst well, 25-35oС is unpleasant and causes a nausea reflex.
The smell of water Two groups of odors are distinguished: natural and artificial odors.
Odors of natural origin are caused by living and dead organisms in water, shore, bottom, soil, ground, etc. by influence. For example, the presence of plant debris in water gives it an earthy, muddy or swampy smell; An aromatic smell will be noticed when the water blooms; The presence of hydrogen sulfide gives the water a rotten egg smell; When organic matter rots or becomes contaminated with its waste, a putrid, hydrogen sulfide, or fecal odor is produced.
Odors of artificial origin arise when water is polluted by industrial and sewage water (phenolic, pharmacy odor, chlorine, metallic, oil, etc.).
taste and aroma. Drinking water should be pleasant, without any side taste. The taste of water depends on the mineral composition of the water, its temperature and the gases dissolved in it.
Coloration is a natural property of water caused by humic substances. They are formed during the decomposition of organic matter in the soil, are washed out of it, get into open water bodies and give it a yellow to brown color. Therefore, coloration is an inherent property of water in open watercourses and it increases sharply during the flood period. Water can be colored by iron compounds (metallic green color), algae, substances suspended in it, contamination with sewage water, etc. The color of drinking water is determined photometrically and it should be 20º, in this case the water is considered colorless.
Water turbidity - depends on the particles of mineral or organic origin in the water. Increased turbidity limits water consumption, it indicates pollution of natural waters.
Hardness - depends on the degree of water mineralization, i.e. on the content of calcium and magnesium salts in it. Hard water reduces the nutritional value and digestibility of prepared food. For example, vegetables and meat cooked in hard water are difficult to process, as hard-to-dissolve protein compounds are formed with calcium and magnesium salts; The taste of tea worsens. Hard water forms insoluble deposits in hot water pipes and on dishes. The connection between the consumption of hard water and urolithiasis has been revealed. The permissible water hardness should not exceed 7 mg/Eq/L.
