In this study, photocatalytic degradation of ammonia in petrochemical wastewater was investigated by solar light/TiO2 photocatalysis. The TiO2 nanoparticles were used as photocatalysts, which were immobilized on light expanded clay aggregate (LECA) granules as a new porous and light-weight support. A real Siri (Iran) petroleum refinery wastewater, containing a range of aromatic organic compounds, was treated using TiO2 photocatalyst. Samples were collected from the inlet point of the biological treatment unit. Optimal suspended catalyst concentration, fluid pH, and temperature were obtained at amounts of near 100 mgL-1, 3, and 45 degrees C, respectively. The identification analysis of the organic pollutants, provided by means of a gas chromatography-mass spectrometry, equipped with headspace injection technique, showed that different petroleum compounds were degraded with high efficiencies.