Since the day when a man created pesticides and started using them, they became pollutants because it is extremely difficult to degrade them naturally. Pesticides have some positive characteristics but once they enter the aquatic system they become a problem because of their harmful effect. Because of that effects, on humans, plants and animals, some pesticides are included in the list of priority substances of Directive 2013/39/EU, including atrazine, and their concentration in the aquatic environment is continuously monitored. Therefore, there is a need to find effective, but also environmentally acceptable methods for removing them. Methods of first and second stage wastewater treatment are not effective for the removal of pesticides, so Advanced Oxidation Processes (AOPs) are increasingly used and shown to be more effective. The aim of this work was to apply photolysis and photooxidation processes with the addition of oxidants (hydrogen peroxide and sodium persulfate) in a tubular reactor for removing atrazine from Zagreb water supply. The influence of the process parameters (flow and concentration of oxidants) on the efficiency of atrazine removal was studied. Using a combination of full factor plan and response surface methodology (RSM), the maximum removal of atrazine of 78.11 % was achieved by applying a VUV/PS process at a flow rate of 0.6 L/min and a persulfate concentration of 2 mM which was in accordance with the predicted values RSM model (78.68 %). It has been shown that both process parameters, flow and concentration of oxidants have a significant effect on the efficiency of atrazine removal.