Advanced landfill leachate treatment: Sequential electrocoagulation and electrooxidation system for efficient remediation

The treatment of concentrated landfill leachate generated by nanofiltration and reverse osmosis processes represents a significant challenge. This concentrate is characterized by high concentrations of heavy metals, contaminants of emerging concern, dissolved salts, and organic compounds. In this study, a novel advanced treatment system integrating an Electrocoagulation Reactor with a subsequent electrooxidation process was proposed. Two anode/cathode arrangements were evaluated: electrocoagulation followed by electrooxidation with “boron-doped diamond” and steel electrodes, and electrocoagulation followed by electrooxidation with “boron-doped diamond” and aluminum electrodes, focusing on their effectiveness in degrading contaminants and improving the quality of the treated concentrated landfill leachate. In order to monitor the efficiency of the electrocoagulation process and integrated systems, the degradation of the physicochemical parameters of absorbance at 254 nm, total organic carbon , and turbidity were investigated. Within the best performance, acute toxicity indices ( Artemia salina - LC50) were determined and possible degradation and/or formation of contaminants of emerging concern were identified by gas chromatography–mass spectrometry (GC–MS). The results indicated the mineralization of 73 % of total organic carbon and 25 % of total nitrogen, an increase in the biodegradability fraction (BOD5/COD) of the concentrated landfill leachate from 0.18 to 0.35, as well as a significant reduction in toxicity (LC50 of 54.4 %), demonstrated by Artemia salina bioassays. The reduction in toxic potential was also observed in the by-product analysis by GC–MS, which indicated the removal of emerging contaminants such as benzene, 2-(2-methoxy-1-propenyl)-1,3,5-trimethylbenzene, benzothiazole, 2-(methylthio) and phenol , 2,2′-methylenebis[6-(1,1-dimethylethyl)-4-methyl-. These findings highlight that the integration of the electrocoagulation process with electrooxidation using a boron-doped diamond and aluminum electrode arrangement is an effective and sustainable solution for the treatment of concentrated landfill leachate. • A new EC reactor configuration was proposed and studied. • BDD/Steel and BDD/Al anodes were compared. • The sequential EO - EC process with BDD/Al anodes is efficient in treating concentrated LL, reducing toxicity and enabling LL purification. • Increased biodegradability conditions (BOD 5 /COD ratio = 0.35)