Abstract-Advanced oxidation processes (AOPs) have emerged as promising techniques for the treatment of wastewater containing complex organic compounds. In this study, experiments were carried out to determine the effect of superficial gas velocity on the hydrodynamic conditions (average gas hold-up & bubble size) and the effect of operating conditions on the photodegradation of methyl orange (MO) in a fluidized bed photoreactor. Optimum operating parameters were found to be: time of 120 min, catalyst loading of 1.5 g/L and the superficial gas velocity being 212.23 mm/s. An increase in the superficial gas velocity increases the average gas hold-up and bubble size. The effect of hydrodynamic conditions on photodegradation showed that an increase in the superficial gas velocity results in an increase in the removal of color and total organic carbon (TOC) removal.