This paper is focused on the influence of granulated activated carbon (GAC) and zeolite as catalysts as well as influences of temperature and pH on the ozonation process. From obtained results it can be concluded that the addition of granulated activated carbon and zeolite to model wastewater has a positive effect on the efficiency and degradation rate of methylene blue oxidation with ozone. The highest oxidation efficiency was observed in the alkaline pH range for which radical reaction mechanism of ozone is characteristic. From the results obtained during the study of the effect of temperature on the ozonation process it follows that both the efficiency and the rate of oxidation of methylene blue grow with increasing temperature.

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The feasibility of ozonation process for 2-mercaptobenzothiazole (2-MBT) removal follows from results of ozonation of the model wastewater. Total removal of 2-MBT was observed after 20 minutes of ozonation. Very good reproducibility of repeated ozonation trials including sampling and analysis was observed. However, the majority of dissolved organic carbon (DOC) and chemical oxygen demand (COD) remained in the reaction mixture. Benzothiazole (BT) and 2-hydroxybenzothiazole (OBT) intermediates were identified during degradation of 2-MBT with ozone. In addition to the above benzothiazole derivatives, the creation of some other organic compounds follows from results of mass balance. The best fits of experimental data were obtained using the first kinetic model for 2-MBT and zero-order kinetic model for COD and DOC. The reaction time of 60 minutes can be considered as effective with regard to controlled oxidation in order to increase a portion of partially oxidized substances. Higher biodegradability and lower toxicity of ozonation products on respiration activity of activated sludge microorganisms was observed at higher ozonation time.

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Water is becoming a strategic raw material and thus, protection of water resources belongs to priorities. Toxic substances need to be removed prior to the biological treatment stage in a WWTP. Biologically resistant substances flow through the biological treatment stage in a WWTP directly to water recipients, and can travel as far as to the underground water and drinking water sources. Taking into account the large volumes of these substances, their removal from ground water and water sources would be extremely costly. It is economical therefore to remove these already at their source or in a WWTP using separation or degradation processes. This paper deals with the possibility to use ozonisation for pretreatment of wastewater prior to the WWTP biological stage. Benzothiazole removal efficiency exceeding 95 % within 60 min. of ozonation was reached when combining ozonation with zeolite addition. Partially oxidised COD portion was significant in the first 15 minutes, followed by subsequent growth of mineralised COD portion.