Landfill Leachate Treatment by Combining Coagulation and Advanced Electrochemical Oxidation Techniques

This paper presents and discusses the results obtained in the treatment of raw landfill leachate (RLL) with a combination of coagulation-flocculation (Alum) and electrochemical techniques, using a filter-press reactor with a boron-doped diamond electrode. The success of the treatment was demonstrated by the quality of the treated water, which was evaluated based on parameters such as color, odor, turbidity, chemical oxygen demand, biochemical oxygen demand, free and total chlorine, total nitrite and nitrate, ammonia and microbiological tests (mesophiles and termotolerant coliforms). The best conditions for coagulation-flocculation involved a dosage of 20 mL/L Al-2(SO4)(3) (50 g/L) at pH 6.0. To reduce energy consumption, the electrochemical treatments were carried out by applying different limiting current density (i(lim)) step sequences. This strategy reduced the energy consumed in the removal of the organic load by up to 40% while maintaining a similarly effective mineralization rate (> 90% COD removal) between the steps. Microbiological tests revealed that the number of mesophiles was more than twelve orders of magnitude lower after electrolysis, indicating the important sanitizing effect caused by the HClO/chloramine species generated in the process. Color, turbidity and ammoniacal nitrogen were completely eliminated from the treated leachate by the end of the electrolysis process.