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Hygienic requirements and standards for drinking water quality
The quality of drinking water is the basis of epidemiological safety and public health. High-quality water is an indicator of high sanitary well-being and living standards of the population, provided with centralized water supply. In developed countries, the state and health authorities pay special attention to the quality of drinking water.
Drinking water must comply with SanPiN 22.214.171.1244-01 “Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control". These sanitary rules apply to water intended for consumption by the population for drinking and domestic purposes, for use in food processing and food production processes, their storage and trade, as well as for the production of products that require the use of drinking-quality water.
Drinking water sold to the population in bottles, containers, bags, must meet the requirements of SanPiN 126.96.36.1996-02 "Drinking water. Hygienic requirements for the quality of water packaged in containers. Quality control".
Drinking water should have favorable organoleptic properties, harmless in chemical composition, be safe in epidemic and radiation terms.
Organoleptic indicators of drinking water. Drinking water should have good organoleptic properties, i.e. be transparent, colorless, unpainted, without smacks and smell, have a refreshing temperature and do not contain visible impurities.
Water temperature. The optimum drinking water temperature for human physiological needs is 8-15 ° C. It has a pleasant refreshing effect, quenches thirst better, is absorbed faster, stimulates the secretory and motor activity of gastrointestinal waste. A water temperature of 25 ° C does not quench thirst; a temperature of 25-35 ° C is unpleasant and causes a gag reflex.
The organoleptic properties of water are normalized in two directions: by the intensity of a person's perception of odor, taste, color and turbidity, and also by the concentration of chemicals in water that affect its organoleptic properties.
The smell of water. The nature and intensity of the smell is determined by the perception of the perceived smell. There are two groups of odors: odors of natural and artificial origin.
Smells of natural origin are caused by living and dying organisms in the water, the influence of the coast, bottom, soil, soil, etc. Thus, the presence of plant debris in water gives it an earthy, silty or marsh odor; when flowering, the water has an aromatic smell; the presence of hydrogen sulfide gives the water the smell of rotten eggs; when rotting organic matter or contaminating it with sewage, a putrefactive, hydrogen sulfide or fecal odor arises.
Odor of artificial origin occurs when water is polluted by industrial and other wastewater (phenolic, camphor, pharmacy, chlorine, metal, gasoline, etc.).
The intensity of the smell of drinking water is estimated by a 5-point system, presented in table. 1. The smell of water should not exceed 2 points.
Odor Intensity Rating
Continuation of the table. 1
Taste and taste. Drinking water should be pleasant, have a refreshing taste without any extraneous taste. The taste of water depends on the mineral composition of water, its temperature and dissolved gases. There are four main taste sensations: salty, sour, sweet, bitter. All other taste sensations are called tastes (alkaline, metallic, chlorine, astringent, etc.). The taste and taste are determined in obviously safe water at a temperature of 20 ° C, and in doubtful cases the water is boiled for 5 minutes and cooled.
The hygienic significance of odors and flavors of water is that when their intensity is above 2 points, water consumption is limited; artificial smells and flavors can be indicators of water pollution by wastewater; natural odors and flavors above 2 points indicate the presence in the water of biologically active substances secreted by blue-green algae.
Chromaticity is a natural property of water, due to the presence of humic substances that are formed during the destruction of organic compounds in the soil, are washed out of it, enter open water bodies and give them a yellowish to brown color. Therefore, the color is inherent in the water of open reservoirs and increases sharply during the flood period. Iron compounds (yellow-greenish coloration), blooming algae, suspended solids, wastewater contamination, etc. can color the water. The color of drinking water is determined photometrically, it should not be higher than 20 °, then the water is considered colorless.
The hygienic meaning of color is that when color is higher than 35 °, water consumption is limited; an increase or decrease in the color of groundwater indicates their pollution; color is an indicator of the effectiveness of bleaching water in waterworks.
Turbidity of the water depends on the presence in the water of suspended particles of mineral or organic origin. Increased turbidity limits water consumption, indicates pollution of natural waters. Turbidity is an indicator of the effectiveness of the process of clarification of water in wastewater treatment plants.
Organoleptic indicators of drinking water must comply with the standards presented in table. 2.
Organoleptic indicators of drinking water
Note: the value indicated in brackets can be set based on the sanitary-epidemiological situation.
Chemicals that can degrade the organoleptic properties of water include natural mineral elements (chlorides, sulfates, iron, copper, zinc, calcium and magnesium salts), as well as some chemicals added to drinking water during its treatment (aluminum compounds, polyacrylamides etc.), therefore, limit standards for the content of such substances are established (Tables 3, 4).
Changes in the organoleptic characteristics of water have an adverse effect on humans and can lead to a deterioration in the sanitary state of water (for example, an increase in turbidity of water reduces the bactericidal effect of chlorination).
Chemical indicators of drinking water. The safety of drinking water by chemical composition is determined by 3 groups of standards: generalized indicators; the content of chemicals generated during water treatment; the content of chemicals resulting from human activities.
1. Generalized indicators and the content of harmful chemicals that are most often found in natural waters on the territory of Russia, as well as substances of anthropogenic origin that have received global distribution, are presented in table. 3.
Generalized indicators and the content of harmful chemicals
in drinking water
1. A limiting sign of the harmfulness of a substance according to which the standard is established: “s.-t.” - sanitary-toxicological, "org." - organoleptic.
2. The value indicated in brackets may be set in the respective territory depending on the situation.
3. Hazard classes of the substance: 1 class - extremely dangerous, 2 - highly dangerous, 3 - dangerous, 4 - moderately dangerous.
From the generalized indicators of water, rigidity is of great hygienic importance. It depends on the degree of salinity of the water, i.e. the content of calcium and magnesium salts in it. Hardness is measured in mg / equiv / l (1 mg / equiv = 28 mg / l CaO) or in degrees (1 degree = 10 mg / l CaO). Water with a hardness of up to 3.5 mg / equiv / l (10 °) is considered soft, from 7 to 14 mg / equiv / l - hard and above 14 mg / equiv / l (40 °) - very hard.
The hardness of the water reduces the taste and digestibility of the cooked food. So, vegetables and meat cooked in hard water are poorly digested as a result of the formation of sparingly soluble protein compounds with calcium and magnesium salts; the appearance and taste of tea is getting worse. Hard water forms an insoluble precipitate on hot water pipes and utensils, making it difficult to care for them. A connection was found between the use of hard water and the increased incidence of urolithiasis. Permissible water hardness should not exceed 7 mg / equiv / l.
Among the natural chemicals of great physiological importance include fluoride. So, with an increased fluorine content in the soil and, therefore, in water (more than 1.5 mg / l), the disease fluorosis develops, the external sign of which is the appearance of stains on tooth enamel; when the fluorine content is less than 0.5 mg / l, tooth decay occurs.
In SanPiN 188.8.131.526-02 "Drinking water. Hygienic requirements for the quality of water packaged in containers ”also includes MPC standards for a number of chemicals that are most hazardous to human health, such as beryllium, mercury, lead, molybdenum, arsenic, strontium, etc., which can cause chronic intoxication of a person. The MPCs of these elements in drinking water are determined depending on the degree of their toxic effect and cumulative properties (ability to accumulate in the body).
Among the possible chemical pollutants of drinking water, nitrates are of great hygienic importance. Nitrates can be contained in deep underground waters as their natural component, but the main source of nitrate accumulation in water bodies is the decomposition products of organic wastewater substances. Consequently, the amount of nitrates in the water serves as an indirect indicator of pollution with its organic substances of domestic origin. The importance of nitrates as a sanitary indicator of water quality, as well as their toxicity (the development of methemoglobinemia in children) with a significant increase in the concentration of nitrates, served as the basis for their limitation in drinking water (up to 45 mg / l by NO3 ion).
2. The content of harmful chemicals entering and forming in the water during its processing in the water supply system. This group combines toxic substances, the presence of which is due to the addition of reagents in order to clarify, bleach, and disinfect water or to conduct one of the types of special treatment (softening, fluorination, etc.). So, for the purification of drinking water, a synthetic organic flocculant is used - polyacrylamide (PAA), the residual amounts of which in drinking water should not exceed 2 mg / l (table. 4).
The content of harmful chemicals entering and forming in the water during its processing in the water supply system
3. The content of harmful chemicals entering water sources as a result of human activities. This list includes hygiene standards for more than 1200 chemicals that may be present in drinking water and can be identified by modern analytical methods.
Radiation indicators of drinking water. The radiation safety of drinking water must comply with the standards presented in table. 5.
Radiation indicators of drinking water
The identification of radionuclides present in water and the measurement of their individual concentrations is carried out when the standards for total activity are exceeded.
Microbiological and parasitological indicators of drinking water. The safety of drinking water in an epidemic respect is determined by its compliance with the standards presented in table. 6.
Microbiological and parasitological indicators of drinking water
Thermo-tolerant coliform bacteria are true indicators of fecal contamination. They are identified by the fermentation of lactose at a temperature of 44 ° C. Common coliform bacteria ferment lactose at 37 ° C.
The total microbial number (TBC) is determined by the increase in MPA during incubation of 37 ° C. This indicator characterizes the effectiveness of drinking water purification and its determination in dynamics is recommended.
Coliphages are indicators of viral contamination of drinking water.
Spores of sulfite-reducing clostridia are highly resistant to disinfection, therefore, they are an indirect indicator of the quality of water purification from intestinal viruses and parasitic protozoa that are resistant to disinfection. They are determined only in water supply systems from surface sources before water is supplied to the distribution network.
Giardia cysts characterize the parasitic safety of drinking water obtained from surface water sources. Determined only when evaluating the effectiveness of water treatment technology.
Pathogenic microorganisms in drinking water are determined by sanitary and epidemiological indications.
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