New way for treating oilfield thrice-circulated sewage by means of coagulation-electrocoagulation

The paper is aimed to present a renovated technology known as coagulation-electrocoagulation technology for treating oilfield thrice-circulated sewage to meet the demand of the state integrated sewage-discharging standard. As is known,the thrice oilfield sewage is a kind of sewage left-over in the oil-well drilling process,which contains large amounts of chemical oxygen demand (CODCr). According to the characteristics of the above said sewage,traditional disposal technology used in the domestic oil fields is no longer able to meet the needs of the state standard value of CODCr. To change the situation,the present authors have worked out an advanced processing technology known as the integrated coagulation-electrocoagulation technology. In this process,the thrice oilfield sewage can be disposed in a home-made reactor under different reaction conditions including reaction time,amount of flocculent,electric current,temperature and pH value etc. Then the vacuumized extraction and filtering method can be used to obtain the final disposed water,with the potassium dichromate method adopted to determine the CODCr concentration in the final disposed waste.The results of adopting the renovated technology to the sewage treatment prove that the removing rated of CODCr,can be expected to reach 66.7%. The other indices obtained can be shown as follows: the optimal values of pH=7.00,dosage of aluminum sulfate=300 mg/L,the rotational speed=100 r/min for 20 min,the current density=12.5 A/m2,the temperature=40 centigrade. In addition,the electrodes both positive and negative are made of steel in a distance of one centimeter. The CODCr of the effluent can meet the need of the expected standards. as well. Thus,it can be seen that the technology of coagulation-electrocoagulation can efficiently dispose the thrice oilfield sewage while the reaction conditions concerned also contribute greatly to the processing efficiency of the technology.