High gradient magnetic separation combined with electrocoagulation and electrochemical oxidation for the treatment of landfill leachate

Landfill leachate was treated in a bench scale plant by high gradient magnetic separation combined with electrocoagulation using iron electrodes and electrochemical oxidation. The electrocoagulation with iron electrodes was used as a magnetic seeding method for phosphorus and organic compounds. Some organic compounds in landfill leachate was coagulated by iron(II) hydrates or hydroxides produced from iron electrodes. Phosphorus in landfill leachate was also suspended as iron phosphate. These magnetized solids were removed by high gradient magnetic separation using a superconducting magnet. The removal rate of total phosphate (T-P) was approximately 90% at a flow rate of 100 L/h. Residuals in the effluent of magnetic filter such as ammonium nitrogen (NH₄ - N) and chemical oxygen demands (COD) were destroyed by electrochemical oxidation using Ti/PbO₂ anode. The hypochlorite generated from oxidation of chloride in leachate might play a key oxidant in the effective removal of NH₄ - N. The experimental result showed that the pretreatment combined process of electrocoagulation using iron electrodes and high gradient magnetic separation might improve the charge efficiency in electrochemical oxidation. Several chemicals that were suspected of having environmental endocrine disrupting effects was also decreased.