The key purpose of any community is to create a favorable living environment so that people could live a long healthy life, and the country could ensure development of human potential. One of the most important constituents of the favorable living environment is sanitary and epidemiological well-being of people as a basis of national security. Nevertheless, the issue of environmental pollution and protection in the Russian Federation is still timely and relevant in the beginning of the third millennium. Provision of population with drinking water of good quality is one of the main tasks of epidemiological welfare and prevention of population morbidity by the country [1, 2].

In accordance with sanitary and epidemiological requirements, drinking water should have epidemiological and radiological safety, harmless chemical composition and good organoleptic properties [3, 4]. According to some authors, quality of water that comes from water supply sources and networks in the majority of regions in the Russian Federation is still bad [5–7].

In 2014, the Russian Federation gained new territories due to accession of the Crimean Peninsula, which is of an important strategic and economic value. Owing to natural and geographical peculiarities, the peninsula had the shortest water supply as compared with other regions of Russia and the USSR. In the 60s of the last century, the North Crimean Canal was built to provide drylands of Crimea with water. Dnipro water from the Kakhovka reservoir was taken to the peninsula through the Canal that had poorly coped with the task for several decades. Following accession of Crimea to Russia, Ukraine blocked the Canal, and the question of fresh water became critically acute. In the present time, hydrotechnical constructions have been built. They took water from the Belogorsk and Taygan water reservoirs to the North Crimean Canal. Three water intake areas were also created in Nizhny Gorsk and Dzhankoi Districts.

According to the Agricultural Research Institute of Crimea, over 50% water sources in Crimea do not correspond to Sanitary Rules and Regulations 1.2.3685–21 and Sanitary Rules and Regulations 2.1.3684–21 [8].

The Samara region belongs to heavily industrial, densely- populated and urbanized regions of Russia. By the extent of human impact on the environment, the Samara region is one of environmentally unfriendly regions of the Volga River basin. Motor vehicles have been playing the leading role in the creation of ecological and hygienic situation in the Samara region over the last years, as exhaust gases from these vehicles account for 60–80% of all toxic atmospheric emissions here.

The Volga River and its tributaries, that account for more than 38.5% of the total intake from all water sources in the Russian Federation, experience a great anthropogenic impact. The Samara urban area has prerequisites for a tense ecological and hygienic environmental situation. It dictates the need for constant surveillance over sanitary and hygienic condition of environmental objects, including the centralized domestic water supply system [9–11].

The sanitary and hygienic well-being of drinking water can produce both favorable and unfavorable effects on people’s health. Composition of drinking water influences the total health risk. Thus, drinking water quality should be monitored on a constant basis.

MATERIALS AND METHODS

Quality of drinking water from the centralized domestic water supply system in the Samara urban area and Republic of Crimea (hereinafter referred to as the RC) was analyzed.

The samples were taken in summer 2021. The studies were conducted using 20 sanitary and chemical parameters in accordance with Sanitary Rules and Regulations 1.2.3685–21 and Sanitary Rules and Regulations 2.1.3684–21. The studies were conducted using sanitary and chemical parameters based on health and hygiene rules and standards. Water samples were drawn in summer 2020–2021. The primary data were collected and stored using Microsoft Excel 2013 (Microsoft, USA).

STUDY RESULTS

As shown in table, drinking water corresponds to the requirements of Sanitary Rules and Regulations 1.2.3685–21 and Sanitary Rules and Regulations 2.1.3684–21 by many sanitary and chemical parameters.

The content of oil products was higher than MPL in all tested samples from the Samara urban area and Republic of Crimea. This can be an indicator of non-qualitative water supply.

In the Samara urban area, the average value of that parameter exceeded the MPL by 0.18 mg/dm³. It should be noted that according to the studies conducted at the department of food hygiene with a course of hygiene for children and adolescents and by Pharmatsia Research and Educational Center of the Samara State Medical University of the Ministry of Health of the Russian Federation, the content of oil products in drinking water from the centralized water supply system in the Samara urban area tends to increase.

Exceeding the maximum permissible limit of carbon compounds in surface water and groundwater is a consequence of industrial development and non-compliance with ecological standards of manufacture. Dangerous compounds seep through the soil into groundwater and contaminate the natural sources of drinking water. Water is also contaminated with oil products from transport activity and when artesian and oil-bearing layers are mixed. Consumption of water with high content of oil products increases the risk of cancer of internal organs, diseases of digestive and endocrine systems and oral cavity.

Within the Samara urban area, hardness values of groundwater samples exceeded the maximum permissible limits. Color, dry residue, permanganate index (PI), sulphates, chlorides and copper content were within normal hygienic limits. PI of drinking water in the Samara urban area was 4.5 times higher than that in the RC, whereas the average values of drinking water color and dry residue found in Samara were 1.5 times higher than the respective average values for the analyzed samples in the RC. It is worth noting that in the Samara urban district the values of dry residue were higher than normal limits (1000 mg/dm³) in areas where drinking water is mixed with groundwater, i. e., Kuibyshevskyi district (1690.70 mg/dm³) and Ozerny village (1435.20 mg/dm³).

Water permanganate index is an indicative that the water contains dissolved readily oxidizable organic substances. Water color is an indirect parameter showing the presence of dissolved organic matter, in particular, humic and fulvic acids. This can also be indicative of technogenic-r elated contamination.

Dry residue characterizes the content of organic and inorganic matter in water. High values of dry residue influence the organoleptic indicators of water, in particular, taste. In separate areas of the Samara urban district, high values of mineralization by the dry residue are due to the values of groundwater supply sources, the Samara River impact and possible non-effective functioning of decontamination stations.

In its turn, content of sulphates and chlorides in the analyzed samples of drinking water in the RC exceeded by 1.2 times the respective values in the Samara urban area. Content of copper was 3 times lower in drinking water of the Samara urban area as compared with that of the RC.

Copper produces a negative effect on water- supply and sanitary engineering devices, as its higher water content is dangerous for human health. Professionals believe that copper is the third hazard class substance with its maximum permissible limit being 1.0 mg/l.

Nitrogenous compounds present in drinking water as nitrates, nitrites and ammonia, are indicative of contamination of water sources with sewage. No exceeded values were found in all analyzed samples by all the parameters of nitrogenous compounds.

DISCUSSION OF RESULTS

In the analyzed samples, drinking water corresponded to the requirements of Sanitary Rules and Regulations 1.2.3685– 21 and Sanitary Rules and Regulations 2.1.3684–21 by many sanitary and chemical parameters. During the comparative analysis of sanitary and chemical parameters of drinking water in the Samara urban area and Republic of Crimea, higher concentrations of sulphates (mean difference of 21.5 mg/dm³), chlorides (mean difference of 19 mg/dm³) and copper (mean difference of 0.015 mg/dm³) were found in water samples from the Republic of Crimea and higher values of dry residue (mean difference of 165.02 mg/dm³), color (mean difference of 3.66 mg/dm³) and permanganate index (mean difference of 2.72 mg/dm³) were detected in samples of drinking water from the Samara urban area. The obtained results can demonstrate natural composition differences in the sources of central water supply, water treating and condition of water supply pipes [2, 8]. Based on the conducted analysis it was shown that quality of the analyzed samples of drinking water in the Samara urban area and Republic of Crimea does not correspond to hygienic requirements as far as oil product content goes.

Quality of drinking water is determined with a source of drinking water supply (surface and underground). Thus, respective water treatment is necessary to obtain normal composition of prepared drinking water [10, 11]. Bad condition of water supply pipes also produced an unfavorable effect on quality of water obtained by the consumer. In this case, the consumer can improve quality of drinking water by following a number of recommendations [5, 7, 10].

CONCLUSIONS

Nonconformance to hygienic requirements was reported during the conducted study estimating quality of drinking water supply in different regions of the Russian Federation. The obtained results are a testimony to the insignificant effect of cleaning with pumping and filtering units regarding organic substances which are resistant to oxidation.