Evaluation of electrocoagulation process for high-strength swine wastewater pretreatment

Abstract

• Electrocoagulation for swine wastewater pretreatment was systematically studied. • Fe anode and neutral matrix were better than Al anode and more acid/alkali matrix. • Removal of 98.5%, 99.5%, 50.6% was achieved for SS, TP, COD by electrocoagulation. • Electrooxidation occurred during electrocoagulation improved the biodegradability. Characterized by the high concentration suspended solids (SS), chemical oxygen demand (COD), biological oxygen demand (BOD), ammonium nitrogen and total phosphorus (TP), a solid–liquid separation as a pretreatment is mandatory for swine wastewater before biological treatment. In this study, batch tests of electrocoagulation were investigated under different structural parameters (anode material, inter-electrode distance) and operational parameters (current density, stirring speed, initial pH and reaction time). The results showed that the optimal conditions were the Fe anode, inter-electrode distance of 2.0 cm, current density of 30 mA/cm 2 , no stirring, initial pH of 6.3 without control and reaction time of 35 min in this study. By comparing with chemical coagulation, satisfactory performance was achieved under optimal electrocoagulation: supernatant recovery of 60%, SS, TP, COD and BOD removal efficiencies of 98.5%, 99.5%, 50.6% and 10%. In addition, fluorescent substances formation was observed under electrocoagulation and thus increased the BOD/COD ratio from 0.36 to 0.66. The enhanced biodegradability would facilitate the subsequent biological removal and the overall swine wastewater treatment. Conclusively, the iron electrocoagulation technology is a promising process for high-strength swine wastewater pretreatment.