Experimental study on treatment of tertiary oil recovery wastewater by electrocoagulation

Abstract The mechanisms of the treatment of tertiary oil recovery wastewater by electrocoagulation are still unclear. Here, an electrocoagulation device for oilfield application was designed and used for a study of this system. Single factor analysis was used to investigate the effects of current density, initial pH value, polymer concentration (HPAM) and electrode type on the electro-coagulation treatment performance of oilfield sewage. Treatment effectiveness was quantified by measuring the oil fraction and turbidity as a function of time. The results show that the treatment is more effective at higher current density. Regarding pH, neutral conditions led to the most effective treatment, followed by acidic, then alkaline conditions. The polymer concentration had a significant influence on the final treated water quality, with treatment effectiveness decreasing gradually with increasing polymer concentration. These effects could all be explained by factors related to the stability of oil droplets against collision and coalescence. Compared to the Al electrode, the floc generated by Fe electrode in the treatment experiment is smaller, and therefore not as easy to coagulate and settle in a short time. Thus, Fe electrodes are not conducive to the rapid treatment of wastewater by electrocoagulation.