Coupling anaerobic digestion process and electrocoagulation using iron and aluminium electrodes for slaughterhouse wastewater treatment

•A two-stage process combining AD and EC was used for treatment of SWW.•AD used as primary treatment allowed the removal of 50% of COD.•Secondary treatment using EC allowed simultaneous removing COD, orthophosphate and nitrate.•More than 79% of COD, 95% of nitrate, and 90% of turbidity were removed while AD and EC were successively used. The performance of a two-stage process combining anaerobic digestion (AD) and electrocoagulation (EC) was studied for the treatment of slaughterhouse wastewater (SWW). Anaerobic digestion was used as primary treatment, whereas electrocoagulation process was used as secondary treatment. After anaerobic digestion, the optimal current density and the treatment time for Chemical Oxygen Demand (COD) and P-PO43− removal by electrocoagulation using Fe and Al electrodes were determined. These optimal conditions were finally used for the secondary treatment of slaughterhouse wastewater by electrocoagulation. The primary treatment by anaerobic digestion removed of 49.93 ± 0.37% COD. However, this led to an increase in residual concentration of P-PO43−. The optimal conditions for COD and P-PO43− removal by electrocoagulation were obtained with a current density of 18.18 mA/cm2 and a treatment time of 40 min for both types of electrodes. The secondary treatment by electrocoagulation respectively resulted from a total removal of 79.73±0.75% and 80.12±0.85% COD, 95.90±0.03% and 95.42±0.11% NO3−, and 92.48±0.20% and 90.66±0.36% of turbidity, respectively, with Fe and Al electrodes. This study reveals the complementarity of anaerobic digestion and electrocoagulation could be the basis of a process able to simultaneously remove organic and inorganic pollutants for various applications (municipal and industrial wastewater treatment, etc.).