Electrochemical Oxidation Combined with Physical–Chemical Pretreatment Processes for the Treatment of Refractory Landfill Leachate

Abstract

An electrochemical oxidation process was adopted for the treatment of refractory landfill leachate in this study. It was found that the process was effective for the removal of COD and ammonium, but expensive energy loading was required for the individual electrochemical treatment of landfill leachate. Thus, coagulation and adsorption pretreatments were conducted to assist the electrochemical oxidation treatment of refractory landfill leachate. In this study, electrochemical oxidation combined with pretreatment processes was found to accomplish better results than the individual electrochemical oxidation process for the treatment of landfill leachate. COD and ammonium removal efficiencies of 90.3% and 80.1% could be obtained by electrochemical oxidation combined with adsorption pretreatment. In this study, coagulation and carbon adsorption pretreatment processes were found to remove specific organics in landfill leachate. Low molecular weight (LMW) organics were predominant after coagulation pretreatment while high molecular weight (HMW) compounds mostly found in the leachate after carbon adsorption pretreatment. The variation of organic characteristics caused by coagulation and adsorption pretreatments also affected the electrochemical treatability of landfill leachate. The electrolysis of the pretreated leachate by carbon adsorption showed higher current efficiency and faster COD removal rate than the electrolysis of coagulation pretreated leachate. It is inferred that the residual organics in the leachate pretreated by adsorption were more amenable to electrochemical oxidation treatment than those in the coagulation pretreated leachate. The results suggested that the electrochemical oxidation process favored the destruction of HMW organics rather than LMW organics in landfill leachate.