混凝-电凝聚-超滤技术处理3次采油废水研究

A novel approach to treating oilfield thrice- circulated sewage by means of coagulation-electr ocoagulation- ultr afiltration

为使3次采油废水的COD_(Cr)达到国家标准要求,在保留油田现有工艺处理的基础上,采用电凝聚-超滤耦合技术并投加无机混凝剂对3次采油废水进行深度处理。调整跨膜压差、反应时间、混凝剂投加量、电流密度、温度、pH值等进行条件筛选试验。电凝聚反应结束后启动超滤系统,从反应槽中取适量处理水,采用重铬酸钾法测定其COD_(Cr)。采用钢作电极,当极板间距为2 cm,pH值为7.00,硫酸铝混凝剂投加量为 300 mg/L,搅拌速度为500 r/min,电流密度为12.5 A/m^2时,40℃下水浴加热反应30 min后,启动超滤系统并控制跨膜压差为0.08 MPa,此时COD_(Cr)去除率达69.3%,出水COD_(Cr)值为81.8 mg/L,满足国家《污水综合排放标准》(GB 8987-1996)中一级标准要求。研究表明,混凝-电凝聚-超滤技术能够有效处理3次采油废水,反应时间为30-40 min,混凝剂投加量为300-400 mg/L,电流密度为12.5-16.7 A/m^2,温度为40℃,pH值为7-7.5时,其处理效果显著。

The paper is aimed to present a renovated technical approach known as the eoagulation-electrocoagulation-ultrafiltration technology in 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 by the oil-well drilling process, which contains large amounts of chemical oxygen demand （CODcr）. Technically speaking, the above said sewage is considered no more qualified to meet the needs of the state standard value of CODCr, if it is treated by traditional technological disposal means at home. To change the situation, we have developed a novel processing approach, known as the integrated coagulationelectrocoagulation-ultrafiltration technology. In this new approach, the thrice oilfield sewage can be treated in a home-made reactor under different reaction condition, including reaction time, amount of flocculent, electric current, temperature and pH value regulation, etc. Later, the ultrafiltration system can be applied to obtain the final-treated water and its CODCr. The results of our experimental use of the renovated technology indicate that the removal rate of CODCr reaches 69.3 %. The other optimal conditions obtained can be shown as follows： pH = 7.00, dosages of aluminum sulfate = 300 mg/L,the rotational speed = 500 r/min for 30 rain, the current density = 12.5 A/m^2, the temperature = 40 ℃. In addition, the transmembrane pressure on the ultrafiltration membrane = 0.08 MPa and the electrodes both positive and negative are made of steel in a distance of two cm. The CODCr of the effluent is in conformity with the demand of the expected standards as well. Thus, the technology of coagulation-electrocoagulation-ultrafiltration can be regarded as a novel qualified approach to the thrice oilfield sewage.