Wastewater can be purified in many ways, and in this thesis aerobic bioreactor was described. The bioreactor was located in the industrial zone in Koprivnica, and had been built in 1975. Indicators of total pollution in wastewater are biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Determination of BOD5 was carried out using OxiTop sensor that operate on the principle of measuring the pressure within the closed system. COD was determined by spectrophotometric method, using dichromate in sulfuric acid as an oxidizing agent with silver sulphate as a catalyst. Wastewater was also comprised of anionic surfactants used as production facility cleansers. Determination of anionic surfactant was carried out by using Methylene Blue Active Substances (MBAS) spectrophotometric method. At the entrance to the wastewater treatment plant the amount of BOD5 was 650 mg \(O_{2}\)/L, and at the output of device 10 mg \(O_{2}\)/L. Spectrofotometric determination of COD value gave the following results: at the entrance of the device measured value was 1175 mg \(O_{2}\)/L and at the output of the device 119 mg \(O_{2}\)/L. Concentration of anionic surfactants measured by MBAS method showed at the entrance of the device a value of 0,92 mg/L, but at the output of the device it was found 0,14 mg/L. In the teaching methodology part, lesson unit 'Water' has been processed. It was shown that students of grade 7 learned the importance of water, types of water, its properties and elements of wastewater treatment Teacher’s lesson plan consists of detailed elaboration of the lesson including specific exercises and description of class experiment. By conducting experiments, students practiced the use and handling of laboratory equipment.