This study aims to present the results obtained from the simulation of a flat plate photocatalytic reactor using CFD code FLUENT. For various turbulence models, the simulation results showed the computed flow features for inlet and outlet components of the flat plate reactor under different flow regimes.In addition the performance of the photocatalytic reactor for pollutant degradation was observed to depend on the reactor s hydrodynamics. The results reported here suggest the importance of fluid mixing in the flat plate reactor since the reaction takes place only at the fluid-catalyst interface.The effect of inlet positions and roughness elements on the flow and mass transport of formic acid in the reactive module has been examined which provides significant insight for the efficient design of the flat plate reactor.