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Introduction: Carwash are industries that consume large amounts of water and results wastewater that have different type of pollutents(detergents, oil and grease, metals, etc.).  Enough treatment of carwash wastewater is important and could be protect surface and ground water. Therefore, in this study ozonation process was used for carwash wastewater that generated from washing the cars in Yazd.

Method: The study was conducted on a laboratory scale. Samples were collected from a carwash unit. In a cylindrical pilot packed reactor (with height=1 m and internal diameter=5 cm) with plastic bed, removal rate of COD and anionic surfactants determined by method digestion and Standard chloroform extraction, respectively during the ozonation process with Two Ozone doses (0.7 and 1.1 mg per minute), 3 reaction time ( 30, 60 and 90 minute) and three pH (7, 9 and 11) were used.

Results: The results showed that removal efficiency of COD and anionic surfactants increases with increasing pH and reaction time. At pH =11 and after a reaction time of 90 minutes for an ozone dose of 1.1 mg/min, removal efficiency of COD and anionic surfactants was %68.57 and %77.71, respectively.

Conclusion: The results showed that the ozonation process in packed bed rector has significant ability to remove COD and anionic surfactants from carwash wastewater. But this process alone cannot remove organic content of carwash wastewater completely. The ozonation process can be combined with other methods as appropriate and safe method for treating carwash wastewater.