Contamination of groundwater and surface water with nitrate is a serious problem in many parts of the world. Nitrate enters surface and groundwater through the decomposition and decay of human and animal waste, industrial production, and agricultural runoff. Zinc oxide can be used as a semiconductor catalyst to clean the environment because of its high efficiency, photochemical stability, non-toxic nature and low cost. The aim of this study was to investigate the photocatalytic removal of nitrate from aqueous solutions using ZnO / UV process.