ZnO nanoparticles were synthesized by sol gel method on granular porous natural scoria. Structure and morphology of scoria, synthesized ZnO nanoparticles, and ZnO/scoria nanocomposite were studied by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Approximately 49 mg of nano ZnO was immobilized per gram of scoria. Photocatalytic performance of ZnO/scoria nanocomposite was examined for phenazopyridine and Acid Blue 113 removal from synthetic aqueous solutions under UV irradiation in a continuous open channel reactor. Removal of Acid Blue 113 in pH of 5.5, flow rate of 15 ml/min and Acid Blue 113 concentration of 20 mg/L was obtained 70.78%. Removal of phenazopyridine in pH of 6.0, flow rate of 15 ml/min and concentration of 15 mg/L was obtained 72.55%. Also, prepared photocatalyst was used for treatment of pharmaceutical and textile pollutants from real wastewaters. COD reductions of these wastewaters were 40.55% and 58.25% respectively in their natural pH, 5 ml/min with initial COD of 800 and 510. Results reveal that ZnO/scoria nanocomposite is efficient for photocatalytic removal of pharmaceutical and textile pollutants with reusability.