Measuring the content of oxygen dissolved in a freshwater reservoir
Authors:   Kyiv National University of Construction and Architecture, Pil'kevych Yu. H. , Rоzоrinov H. М. ,   National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute", Ткаchenko Т. М. ,   Kyiv National University of Construction and Architecture
Published: May 2021

For the life of fish and other aquatic animals, the oxygen dissolved in water is particularly important. Oxygen partially penetrates into water from the atmosphere, partially released in the reservoir itself as a result of the livelihoods of plant organisms. By means of chlorophyll, green plants extracted from carbon dioxide needed to construct a living matter of carbon, allocating oxygen in the surrounding space. This process of photosynthesis proceeds due to the energy of sunlight only in the light time of day. The penetration of oxygen in the atmosphere contributes to wind, flow, precipitation, sharp changes in temperature and other reasons that increase the mixing of water layers. In reservoirs, strongly contaminated organic substances, the water in addition to the rich salts of sulfuric acid (sulfates) may appear poisonous for fish and other aqueous animals gaz – hydrogen sulfide. It occurs only in the absence of oxygen with the participation of special bacteria. Carbon dioxide is accumulated as a result of breathing aquatic organisms, and most importantly - as a result of oxidation of organic matter. Therefore, the excess of carbon dioxide indicates a significant contamination of reservoirs by organic substances. In itself, the increase in water oxidation is safe for fish, and even useful to the known limits, since it usually increases the productivity of reservoirs. Organic substances that are formed in the reservoir itself, or industries from fields from fields, farmsteads, or stand out by birds, animals, human, contain some elements and compounds necessary for the development of all living creatures. Among such elements are primarily nitrogen and phosphorus. The abundance of organic substances containing these elements provides for the development of aquatic animals and plants. But when organic substances accumulate too much, then the oxygen regime of the reservoir deteriorates sharply until the conditions of the order. Classic methods and controls of biota parameters of fresh reservoirs have a row of substantial defects to that belong: systematic uncharacter of control of informatively important parameters; subzero exactness of parameters control; large volume of hand operations; necessity of knowledge of mathematical bases of method; bad interpretation of results; need to use support staff. The shortcomings of known methods can be corrected with an automated way of obtaining and processing the informative parameters of fresh water biota. A structural scheme of the process of obtaining the selected parameters of the biota and the preferential algorithm of their processing have been developed. It is shown that the most convenient for collecting mass material about the content of dissolved oxygen in the reservoir is the optical method. Comparison of synchronous measurements by optical and electrochemical sensors showed a significant underestimation of the dissolved oxygen content by an electrochemical sensor compared to the optical one. The optical method of measuring the content of oxygen dissolved in water is based on finding the time and intensity of fluorescence of the sensitive membrane by empirical ratio. Molecules of dissolved oxygen reduce the time and the intensity of membrane fluorescence, created from carefully selected chemical elements. An absolute concentration can be determined after linearization and thermocompensation, which is performed with the help of a built-in water temperature sensor.