The continuous chlorination of swimming pool water and the input of organic contaminants by bathers in combination with recirculation of the pool water inside the system leads to the formation of the disinfection by-products and their accumulation in the water. The theoretical part of the thesis focuses on swimming pool water legislation, gives basic information on pool water treatment including the disinfection (chlorination), and describes the disinfection by-products (DBP) that form during the reaction with organic carbon and nitrogen compounds. For the practical part I cooperated with Terme Sončni park Vivat Spa. I analyzed the results of the laboratory samplings and assessed the effectiveness of the already introduced technological procedures of pool water treatment and their influence on the decrease of trihalomethanes (THM) concentrations. In Terme Vivat pool complex
they are by far the most common cause of pool water samples inconsistency. In Terme Vivat pool complex the pool water for 6 pools is treated in three separate pool systems: B1, B2 and B3. The concentrations of THMs in the pool water have decreased considerably and have stayed below the
maximum limiting value due to the consistent pool water treatment.