Removal of refractory humic acid-like components from UF filtrate of landfill leachate through pH adjustment and coupled electrochemical process

Mature landfill leachate contains large quantities of a wide range of hazardous and refractory pollutants, especially humic acid-like (HA) and fulvic acid-like (FA) substances. These have poor biodegradability and a considerable ultraviolet-light quenching capacity, severely inhibiting the performance of wastewater treatment and post ultraviolet-light disinfection, but this aspect has attracted little previous research. The Fenton reaction has proved to be a feasible method for removing ultraviolet-quenching substances (UVQSs) but in conventional systems it is unable to completely mineralize organic contaminants. In this study, a novel electro-oxidation process was developed consisting of a flow-through reactor with a Cu 2 O cathode to catalyze Fenton-type reactions, and oxidation at a RuO 2 anode. The combination of pH adjustment and electro-oxidation was evaluated for the treatment of real ultrafiltration (UF) filtrate of mature landfill leachate. A series of analytical techniques were used to determine the performance for the removal of HA and FA. Under optimal conditions, the elimination of fluorescence characteristics of HA and FA reached 100 % and 99.3 %, respectively, according to PARAFAC results based on EEM spectra. TOC was removed by 25.5 %∼30.4 % during the pH adjustment step and 51 % by electrochemical oxidation. Changes in the molecular weight distribution and fluorescence content showed that pH adjustment played an important and significant role in removing UVQSs, and the remaining TOC after electrochemical oxidation was attributed to bioavailable amino acid-like substances. Overall, the results have demonstrated the successful development of an effective method of treating the UF filtrate from mature landfill leachate, with particular respect to the removal of the problematic HA and FA content.