Hygienic requirements to drinking water

Hygienic assessment of the quality of water produced on the basis of its organoleptic properties, chemical, bacteriological, and hydrobiological characteristics. For the estimation of organoleptic properties of water determine its transparency, smell, taste. The deterioration in the organoleptic properties of water can be related to the natural features of the reservoir (the structure of the bottom of the coast, the presence of specific hidrofori). For example, marsh water has yellowish color, unpleasant smell. In the steppe regions with saline soils underground water is highly mineralized and become salty taste.
During the descent into water bodies of domestic and industrial waste water organoleptic properties of water deteriorates, indicating sanitary trouble.
Organoleptic properties of water are recognized as satisfactory, when the intensity of her smell and taste of not more than 2 points (on the standard scale determining the smell and taste of water); the color of not more than 20 degrees of the scale, color, and transparency of at least 30 cm (according to type). There should be a strange taste, not peculiar to the water in the locality.
Chemical water quality parameters give an idea of the quantity and composition of organic and inorganic origin. Organic and inorganic substances in water can be a natural impurity and can be a result of pollution of various waste and garbage. In the latter case, they point to the sanitary problems of the water source.
Being a good solvent, water dissolves different compounds included in composition of the soil and bedrock on which it flows. Therefore, the mineral composition of water is seen almost exclusively from the point of view of influence on the taste and stiffness, which lead salts of calcium and magnesium.
Hard water in some people causes skin irritation - In hard water boiled soft poorly vegetables. The result of education in hard water insoluble sediment soap increases its consumption when washing clothes.
Water hardness is expressed in conventional units - C or-milligram-equivalents (mEq) of calcium oxide. One degree of rigidity is equal to 10 mg of Cao in 1 l of water. Milligram-equivalents equal to 2.8 degrees on a rigidity, therefore, to convert a degree of rigidity in milligram-equivalents need a degree to divide 2.8.
Currently, with the purpose of improvement of sanitary water properties her umyagchaet (in centralized water supply), ensuring that total hardness not exceed 7 mg-EQ/l, i.e. 20 degrees. For local water sources (wells) Pets water hardness not exceeding 14 mEq, i.e. 40 degrees.
The chemical analysis of water investigate indirect indicators of bacterial contamination. These include compounds containing nitrogen, total amount of organic substances (water oxidation), chlorides and other
Chlorides (chlorine compounds with various cations, often with sodium) are widely distributed in nature and therefore almost always occur in different quantities in natural waters. They affect the organoleptic properties of water. High chloride content is 100-150 mg/l gives the water unpleasant salty taste. By themselves, chlorides are not dangerous and can allow their content to the limits taste the visibility. According to GOST 2874-73 the chloride content is limited to 350 mg/L.
Addition of chlorides of natural origin, in the water sources are chlorides with household and industrial wastes. Chlorides may indicate contamination of water, if they enter into it with the dregs of animals and humans.
Thus, chlorides is an indirect measure epidemiologically dangerous pollution of water as with the household sewage in it can get, and pathogens.
Indicators of water pollution are also ammonium salt, nitrite (nitrite), nitrates (salts of nitric acid).
Ammonia in the water can be of different origin. In the water deep artesian wells he comes from a physico-chemical reactions recovery nitrate compounds. Ammonia can meet in water marsh origin. In these cases, it does not indicate contamination by animals garbage. More often ammonia appears in the water due to the decomposition of protein substances introduced with domestic wastewater and garbage. Because ammonia is a primary product of decay, its presence in the water speaks of fresh pollution.
Ammonia should be considered as an indicator of water pollution with organic substances of animal origin in case this is confirmed by other indicators of water quality.
In the process of mineralization ammonia is oxidized to nitrite and then to nitrates. Nitrites are an intermediate product of the decomposition of nitrogen-containing organic substances, and their presence may indicate recent pollution. Note, however, that the nitrites may be contained in the clear waters, forming when restoring nitrates.
Nitrate salts (nitrates) are the end product of mineralization of organic substances. Their presence in water indicates the completion of intensive protein distraction and long term pollution of water sources. It should be borne in mind that in underground water (artesian wells) may contain large amounts of nitrates by restoration of nitrate in the soil.

This allows us to differentiate between the assessment of water quality. The presence only of ammonia can be accidental, therefore, if it is not detected when re-analysis, then, obviously, the water is not contaminated. If the water is simultaneously with ammonia is present nitrous acid, it indicates a clear water is contaminated. When there is water all three ingredients you can talk about the old and ongoing pollution. Salts of nitric acid at the same time without water ammonia and nitrous acid salts are allowed within not more than 10 mg/l, as in large quantities it can cause children to toxic cyanosis, which causes increased blood levels of methemoglobin.
On the content of organic substances in water indicates the so-called oxidation - quantity of oxygen required to oxidize organic matter in 1 l of water. Pure water has a oxidability within 2-4 mg/L. In the interpretation of data of the chemical analysis of water from the epidemiological point of view, it is necessary to take into account local conditions. Thus, high oxidation may be due to the presence of organic substances not only animal and vegetable (peat, swampy water).
The content of dissolved oxygen in water is a very important indicator of the sanitary state of water of open reservoirs. In unpolluted waters of the total amount of dissolved oxygen should correspond to the amount of oxygen that can be dissolved at a given temperature and pressure.
Bacteriological examination of water is most important to determine the presence of pathogens. However, this analysis is complex and receive the response takes time, besides it is not always possible to grow pathogenic microorganisms used on nutrient mediums. Therefore, on the possible content in water pathogens are judged by indirect indicators of pollution.
The main source of water contamination with pathogenic microbes are the faeces of humans and animals. A permanent resident of the intestine is E. coli, so if you have it in water in large quantities speak of faecal contamination of the water source.
Bacteriological analysis of water, define the following parameters:
1. Bacterial count - the number of colonies of bacteria grown at sowing 1 ml of the analyzed water. What it is, the more the probability of water pollution. Water is considered to be benign, if bacterial count is not more than 100.
2. E-coli - lowest water volume in ml, containing one E. coli. The more water contaminated with faeces, the less amount of water, which is found E. coli. According to GOST e-coli in tap water should be at least 333. Consider that in well water e-coli should be not less than 100.
3. The coliform index - the number of coliform bacteria in 1 l of water. For tap water should be not more than 3. Such coliform index is installed in accordance with the technical efficiency of the process of purification and disinfection of water on modern water treatment plant.
It is established experimentally that when coli-index equal to 3, there is a complete sterility of water against pathogenic microbes.
Tap water must meet certain hygiene requirements (table. 6).

Table 6. Requirements to the quality of drinking water (extract from GOST 2874-73)
Indicator Regulations
The smell and taste at a temperature of 20 degrees, points
Chromaticity scale, degrees
Turbidity on the standard scale, mg/l
Total hardness, mg-ekv/l
Lead, mg/l
Arsenic, mg/l
The content of fluorine, mg/l
Copper, mg/l
The content of iron, mg/l
The content of zinc, mg/l
The total number of bacteria at sowing 1 ml of water
The number of coliform bacteria in 1 l of water
Not more than 2
" " 20 degrees
" " 1,5
" above 7
" more than 0.1
" " 0,05
" " 1,5
" " 3
" " 0,3
" " 5
" " 100
" " 3

To water local water sources (wells) is not always possible to present a strict hygienic requirements. Therefore, for water from local water sources are the so-called local standards, developed on the basis of repeated laboratory tests and accounting hydro-geological features of the area. Thus, S. N. The cherkinsky, transparency should be at least 30 cm, color - not more than 35 degrees, the hardness not higher than 14 mEq (40 degrees), e-coli - not less than 100.