In conclusion, the most efficient AOP for the inactivation of the bacteria studied is the combined UV-Chlorine process. However, the degradation of chlorine during the photolysis processes has been measured, the final free chlorine concentration has always been higher than 0.02 ppm, taking into account that the concentration of toxic chlorine becomes visible for concentrations higher than this value for the health of the aquatic environment, an active carbon filter should be installed before introducing the regenerated water into the aquaponic system. INTRODUCTION METHODOLOGY RESULTS CONCLUSIONS Some of the most effective methods used are Advanced Oxidation Processes (AOP), where oxidants such as hydroxyl radicals are formed to oxidize organic contaminants and microorganisms. Among these methods, the combination of ultraviolet radiation (UVC) with oxidizing agents such as chlorine or hydrogen peroxide (H2O2) stands out. This study focuses on bacterial inactivation in water for reuse purposes using UVC/Cl and UVC/H2O2 AOPs, forming mainly hydroxyl free radicals and chlorine, in a small-scale reactor. The use of oxidizing agents is supposed to increase the efficacy of this process to be applied as a tertiary treatment in a sewage treatment plant. INACTIVATION OF E. COLI AND ANTIBIOTIC RESISTANCE BY UVC/CHLORINE FOR THE FEEDING OF AQUAPONIC SYSTEMS WITH REGENERATED WASTEWATER. Molina Ramírez, María Dolores; Pablos Carro, Cristina; Marugán, Javier Department of Chemical and Environmental Technology, ESCET, Universidad Rey Juan Carlos, C/Tulipán s/n, 28933 Móstoles, Madrid, Spain. E-mail: mariadolores.molina@urjc.es G Grupo de Ingeniería Química y Ambiental ACKNOWLEDGEMENTS: The authors are grateful for the financial support of the Ministry of Science and Innovation through the AquaEnAgri Project (2022/00305/017) and the Horizon Europe Framework Program (HORIZON-CL6-2022-FARM2FORK-01, through AWARE Project, GA N. 101084245. Recirculating aquaculture systems (RAS) involves the accumulation of waste products and microbial load. To maintain optimal growth of plants and fish in aquaponics, filtration and contaminant removal systems must be implemented. A RAS advantage is the reduction of water requirements compared to raceway or pond aquaculture systems.. To go further and for this purpose, this work has evaluated the efficacy of photolysis process in bacterial inactivation with the goal of being applied as a regenerated wastewater treatment to be reused in the aquaponics system. In the case of E. coli inactivation processes, the kinetic constant increases linearly with irradiance and chlorine concentration. However, in the non-irradiated chlorination processes during ARB (Van) inactivation, no further degradation is observed with increasing chlorine concentration. This shows that the use of UV-C radiation is necessary to degrade this type of contaminant. Residual free chlorine at the end of each experiment comprises values between 0.06 and 0.09 ppm, at an initial chlorine concentration of 0.1 ppm and values of 0.06 and 0.17 ppm for an initial concentration of 0.25 ppm, depending on the light conditions. In the case of UV-H2O2 processes, they have shown to be less effective resulting in lower and similar kinetic constants despite the increase in concentration of the compound. TESTS Pollutants • Escherichia coli • Resistant bacteria to the antibiotic Vancomycin (ARB-Van) Kinetic constants calculation (k) Log (CFU/mL) = k · t (min) Oxidizing compound (ppm) Free chlorine Hydrogen Peroxide 0.1 20 0.17 50 0.25 0.5 UVC (254 nm) Radiation (W/m2) 2.89 4.79 7.89 34.42 82.41 0 5 10 15 20 25 30 0 10 20 30 40 k (min-1) Rad (W/m2) E. coli, UV-Cl Process 0 ppm 0.1 ppm 0.25 ppm 0 1 2 3 4 5 6 0 10 20 30 40 k (min-1) Rad (W/m2) E. coli, UV-H2O2 Process 0 ppm 20 ppm 50 ppm 0 5 10 15 20 25 30 0 10 20 30 40 k (min-1) Rad (W/m2) ARB (Van), UV-Cl Process 0 ppm 0.1 ppm 0.25 ppm 0 1 2 3 4 5 6 7 8 0 10 20 30 40 k (min-1) Rad (W/m2) ARB (Van), UV-H2O2 Process 0