COMPARATIVE HYGIENIC ASSESSMENT OF SURFACE WATER QUALITY OF WATER WITHDRAWAL POINTS IN THE ADMINISTRATIVE CENTRE OF THE REGION

Background. In the article the results of the comparative assessment of the chemical composition and microbial content of the surface waters of the Oka River in three water withdrawal points of Ryazan centralized utility and drinking water supply are presented. Aim. The aim of the research was to give a comparative sanitary-hygienic assessment of water quality in Ryazan water withdrawal points from the Oka River. Materials and Methods. In Borkovskoi water withdrawal point and Sokolovskiy water withdrawal point water is withdrawn from the main riverbed of the Oka River whereas in Okskiy water withdrawal point – from the old dead arm of the river (Dyadkovskiy backwater). Organoleptic, composite, sanitary-chemical and microbiologic parameters were analyzed for the period from 2012 to 2016. The comparative assessment of the water quality in the Oka River in three water withdrawal points was done on the basis of long-time average annual parameters and percentage of water samples which do not correspond to the hygienic standards. Results. A significant decrease in odor intensity (at 20° C) and long-time average annual concentrations of ammonia nitrogen and nitrites were detected in the water of Sokolovskiy water withdrawal point compared to Borkovskoi water withdrawal point (p<0.05) as well as more intense water odor (at 20° C) and higher long-time average annual concentrations of ammonia nitrogen and nitrites in the water of Okskiy water withdrawal point in contrast with Sokolovskiy one. A significant decrease in long-time average annual concentrations of iron, arsenic, chromium and chloroform in the water of Sokolovskiy water withdrawal point was found as compared to Okskiy one. The highest percentage of water samples which do not correspond to the hygienic standards by biochemical oxygen, chemical oxygen and ammonia nitrogen concentration was detected in the water of Borkovskoi water withdrawal point and it was 15.0%, 75% and 25%, respectively, while in the water of Sokolovskiy water withdrawal point, ammonia nitrogen concentration did not exceed maximum permissible concentrations (1.5mg/l) and the percentage of the water samples where standard biochemical oxygen demand and chemical oxygen demand did not correspond to Sanitary Regulations and Norms 2.1.5.980-00, was much lower. Bacteriological water analysis of all the water withdrawal points revealed a high percentage of water samples which did not correspond to the sanitary-hygienic standards by Thermotolerant coliform bacteria content which varied in the range from 76.7% in the water abstraction point of Sokolovskiy water withdrawal point to 78.3% in Borkovskoi and Okskiy water withdrawal points. The surface water of the Oka River in water withdrawal points does not correspond to the hygienic standards by aluminium and manganese content in 44.1-61.7% and 31.7-57.6% of water sample, respectively. Conclusion. Signs of water pollution with organic substances, chlorides, compounds of chromium, manganese, formaldehyde and chloroform were found in Dyadkovskiy backwater.