A computational fluid dynamics (CFD) analysis has beenperformed for a flat plate photocatalytic reactor using CFD codeFLUENT. Under the simulated conditions( Reynolds number , Rearound 2650), a detailed time accurate computation shows thedifferent stages of flow evolution and the effects of finite lengthof the reactor in creating flow instability, which is important toimprove the performance of the reactor for storm and wastewaterreuse. The efficiency of a photocatalytic reactor for pollutantdecontamination depends on reactor hydrodynamics andconfigurations. This study aims to investigate the role of differentparameters on the optimization of the reactor design for itsimproved performance. In this regard, more modelling andexperimental efforts are ongoing to better understand theinterplay of the parameters that influence the performance of theflat plate photocatalytic reactor.