MICROBIOLOGICAL ASSESSMENT OF DRINKING WATER QUALITY AT DIFFERENT STAGES OF WATER TREATMENT

The object of research is the quality of sources of centralized water supply according to epidemiological indications and the technology of their disinfection at different stages of water treatment using the example of the «Zhytomyrvodokanal» utility company (UC) (Ukraine). The object of research is evaluated and it is found that studying the bacteriological state of water bodies that are sources of centralized water supply is currently one of the most important tasks. Especially, given the significant impact of human activities on surface waters and the insufficient pace of modernization of water treatment equipment. It is determined that widespread disinfection methods using ultraviolet and chemicals (chlorination and ozonation) have their strengths and weaknesses. The paper presents the results of analyzes of water from sources of centralized water supply at different stages of water treatment accordi"ng to microbiological indicators during 2019: total microbial number (TMN) and total number of coliphages. The unsatisfactory condition of water bodies has been established; it is a source of water supply in the city. It is proved that the existing technology of disinfecting water from centralized water sources, which is carried out in two stages using soluble chlorine and sodium hypochlorite, is effective in neutralizing bacteria of the Escherichia coli group. As a research result, the dependence of the concentration of microorganisms in water sources of centralized water supply on weather conditions is revealed (in total, microbial pollution is observed from May to October). A moderate level of water pollution (ranging from 1.1 to 7.5 units) has been proven by the epidemiological criterion in the «Denyshi» and «Vidsychne» reservoirs (Zhytomyr Region, Ukraine). It has been established that the epidemiological criterion is an acceptable level in clean water tanks. It can be argued that the water in the tanks is suitable for drinking water use by the local population. Thus, the research results show that the technology of water disinfection (involves the introduction of two stages of water treatment) used at the «Zhytomyrvodokanal» UC is effective. Accordingly, this technology may be interesting for other settlements, in the absence of significant funds for the modernization of equipment and in the face of climate change, accompanied by an annual increase in temperature and an increase in the number of microorganisms in water sources