: Ultrasonic flowmeter works on the principle of transmitting and returning ultrasonic waves that pass through the liquid, ie. fluid, and is used to measure the speed of fluid movement through a pipeline or some other structural form of fluid movement. By knowing the velocity of the fluid and the cross-sectional area of the pipeline or other system, the value of the volumetric or mass flow can be obtained indirectly. Fluid flow measuring device model OMNI TDI 200H owned by the laboratory of the Biotechnical Faculty was used for the first time to measure the flow of purified water at the outlet of the plant device of the training center "Grmeč", built as a pilot plant. The paper will describe the role and importance of flow measurement by the conventional method and present the results of the trial operation of an ultrasonic flow meter, model OMNI TDI 200H.

Legionella bacteria are microorganisms found in water and moist soil. They are especially favoured by moisture and heat, especially in different types of swimming pools where these bacteria reproduce and survive even for several months. Legionella spp. cause human diseases if they are introduced into the body through the respiratory tract. This most often happens by inhalation of aerosols, and less often by microaspiration of water contaminated with Legionella . The research aims to examine the presence of Legionella spp. bacteria in pool waters and the factors that influence their maintenance in these waters. Water samples were taken from 13 swimming pools that were registered for swimming and recreation in the Central Bosnian Canton in 2022. The presence of legionella was tested, and temperature, pH values (method BAS EN ISO 10523:2013), and residual chlorine concentrations were measured. The temperature was measured by immersing the probe with a calibrated thermometer until the stabilization of temperature values on the display was reached. The free residual chlorine was measured by the standard colourimetric technique – the N, N-diethyl-phenylenediamine method (HANNA Instruments 96701, Rhode Island, USA). Descriptive statistics and the Chi-square test will be used for data analysis. Statistical analysis of the obtained data will be performed using the basic functions of MS Excel and GraphPad Prism. Of the total number of analyzed samples (n = 13), the presence of legionella was confrmed in 4 samples (31 %). The average water temperature of the samples taken