Evaluation of the Performance of the Dora Refinery Wastewater Treatment Plant


Oil refineries are major contributors to local environmental problems .The main pollutants are oil , dissolved components , spent acids , suspended solids, sludge . Technically it is possible to remove all these pollutants by Physical , chemical and biological means .Oil is initially removed in the (API) separators , by skimming, while the heavy particles by scrapping . Further removal of discrete particles is done by gravity settlement in the primary settlement tank .The remaining suspended matter is removed by chemicals , that are added in the flocculation tank , while further flocs are removed in the air flotation tank . The biological treatment follows to remove the biological pollutants , usually followed by secondary settlement to reduce the flux of suspended particles carried with the effluent water. This thesis deals with the Dora refinery wastewater treatment plant , its present performance in comparison with the designed treatment performance and its final effluents compared with the Iraqi discharged water quality limitations .In order to identify the characteristics of the refinery effluents and to evaluate the performance of the refinery wastewater treatment plant , wastewater from different treatment stages were analyzed for various physical and chemical parameters . Using these parameters as the criteria of performance , comparisons were made between the actual and the designed performance for various potential pollutants. The sampling was conducted during 6 months from May to October 2006 , with two samples in each month for each of the units, one before , and one after.The results showed that the wastewater treatment plant in Al-Dora Refinery performed significantly, where high removal efficiencies , were obtained. For T.S.S , Oil , COD , BOD , Sulfide and Phenol which were 95% , 88% , 86% , 81% , 85% and 97% respectively . And the plant was not very efficient in NH3 , SO4 and PO4 removal .