A process of treating wastewater comprising the steps of inserting an ozonator into a source of wastewater to degrade contaminants in said wastewater; characterized by introducing said wastewater containing ozone gas into a UV reactor to completely degrade said contaminants through photo-Fenton process; and subjecting said photo-Fenton treated solution into a membrane module to degrade recalcitrant contaminants resulting in treated water wherein said photo-Fenton process involves homogenous and heterogeneous Fenton oxidation in combination with UV irradiation; wherein said photo-Fenton process is performed at a pH in a range of 2 to 5.