Background: In the context of deteriorating surface water quality, it is important to create a monitoring system to control constantly changing indicators that can affect the quality of both natural and potable water supplied to the population. Organic carbon is one of the key indicators reflecting the rate of production and destruction, climate change and anthropogenic impacts, safety and efficiency of potable water treatment. Objective: To study key indicators in the organization of potable water source quality monitoring. Materials and methods: In 2020–2021, monthly water sampling was carried out in a reservoir serving as the source of household and potable water supply of a large industrial city of the Sverdlovsk Region, and after water treatment. Water temperature, dissolved total, organic, and inorganic carbon, pH, the permanganate index (PI), hardness, and dry residue were measured. We then analyzed correlations between the indicators and assessed the efficiency of water treatment. Results: Maximum concentrations of Ctotal (54.3 mg/dm3) and Corg (36.0 mg/dm3) in the source water were found in January 2021. The predominance of Cinorg concentrations compared to Corg was mainly observed in warm months of the year. Water treatment generally decreased the content of Ctotal in potable water by 12–32 %, Corg by 12–47 %, Cinorg by 6–32 %, and PI by 28–68 %, except for a few months. In spring and summer 2021, we noted a decrease in PI in the reservoir; compared to other seasons, an increase in water pH was revealed in summer. We established a negative correlation between concentrations of organic carbon and water temperature. Conclusions: Monitoring studies of the surface potable water source have been organized. We revealed seasonal patterns of carbon changes and indicators of the mineral composition of water, and demonstrated the efficiency of water treatment.

Introduction. Increased content of organic substances in natural waters, expanding the list of input substances to water bodies, owing to industrial and economic activities of a person, and climate changes is an urgent issue. Against this background, compounds with unknown chemical and toxic properties are likely to appear. The purpose of this study is to collect data concerning the ways for organic compounds entering water bodies and the human body, study data on interaction mechanisms of organic substances with metals, reveal the fate of known organic chelators, complexing agents as well as organometallic compound shaped by them inside the body. The literature search was carried out in Scopus, Web of Science, CyberLeninka databases. Sources of organic substances entering water bodies, properties of organic substances. There are three types of organic substances in water bodies, divided by the sources of their occurrence (inflow): terrigenous origin, shaped inside water bodies and coming from man-made sources. Organic compounds may produce soluble and insoluble compounds with metals and colloids. Mechanisms of interaction of organic substances with metals. Bonding of organic substances takes place by the type of chelation and complexation. There are factors for bonding: functional group content, the molecular mass of substances, ion radius, and competitive interaction with binding sites. Substances having binding properties include phenolic compounds, carboxylic acids, polysaccharides, and flavonoids. Considering that phenolic compounds are located in large quantities in plant and animal tissues, this group of compounds has been researched more thoroughly in terms of interactions with metals and toxicometry. Intake of organic and organometallic compounds into the body, their kinetics, metabolism and decay. Organic compounds, chelates, and complexes enter the body with drinking water, food, and drugs. They are also generated in the body, including by replacing ions. Data on biochemical and toxicological studies of currently known compounds is given