How to use water resource effectively is an important problem in developing industry. Three combined processes which are composed of oil separator+de-emulsification flocculation+sand filtration (SDF), oil separator+hydrolytic acidification+SBR (SAS) and oil separator+de-emulsification flocculation +SBR (SDS) are conducted in laboratory-scale experiment to treat oil extraction wastewater for an oil-field. The experimental results show that the removal rate of COD(chemistry oxygen demand) and oil treated by SDF process are 85% and 95% respectively, the residual oil in effluent can meet the discharge standard, but the residual COD can not. The removal rate of COD and BOD (biological oxygen demand) of the SAS effluent are 85% and 90% respectively, the BOD can meet but the COD can not meet discharge standard. So the further treatment is required in the process. The SDS effluent with removal rate of 95% and 90% are obtained for COD and BOD respectively, which can completely meet the national standards of oil wastewater discharge and refilling (China). The experimental result shows that oil extraction wastewater has turned into water resource after being treated by SDS.
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