Study On Processing Of Tertiary Oil Recovery Wastewater By Pulsed Current Electroflocculation

Nowadays,most of oil exploitation in China enters a stage of tertiary oil recovery. With the development of oil exploitation, increasing amount of tertiary oil recovery wastewater is needed to be treated so as to meet the requirements of wastewater re-injecting process and discharging in the environment. Generally the tertiary oil recovery wastewater has high temperature, high concentration of salt, polymer and hydrocarbons, high COD but low BOD, and many kinds of chemical agents contained. In this case, the treatment of this kind of wastewater is getting more and more difficult. Moreover, the traditional wastewater processing technology can hardly meet the need of treatment. So how to develop a new method to treat the wastewater from tertiary oil recovery with high adaptability, good effect and high efficiency, becomes an urgent issue in China.In the present work, pulsed current (PC) electroflocculation was applied to treat the tertiary oil recovery wastewater obtained from an oil field. Various factors, including stirring condition, electrode distance, concentration of sodium chloride, operating time, pH, and pulsed current parameters (amplitude, frequency and duty cycle) were investigated to find their effects on the treatment result. Then, based on these results, the amplitude, frequency and operating time were selected as the main factors, and the optimum treatment condition was determined by orthogonal experiments. Meanwhile, the selected factors effects were analyzed and proved by the single-factor experiment results. From the energy consumption and treatment affect, the PC electroflocculation method was compared with the traditional chemical treatment method and direct current (DC) electroflocculation method.The results show that various single-factors and pulsed current parameters have significantly effect on COD and turbidity of the treated wastewater, so they should be optimized based on the wastewater condition. In this work, with the optimized treatment condition, CODCr and turbidity of the treated wastewater can meet the requirements of National Integrated Wastewater Discharge Standard, which means that the pulsed current electroflocculation method can be applied effectively in the treatment of wastewater from tertiary oil recovery. The orthogonal experiment results analysis show that the importance of factors order is: operating time>amplitude>>frequency. Compared with the traditional DC method, under the same supplied electric quantity condition, the PC method consumed less electric energy and created more hydroxyl free radical. The treatment effect indicates that the PC electroflocculation method is much better than the traditional chemical flocculation treatments, using polyaluminium chloride and polymeric ferric sulfate, and the traditional DC electroflocculation method.