Research on the treatment of biologically treated landfill leachate by joint electrochemical system.

Biologically treated landfill leachate (BTLL) is typically characterized by significantly high amount of total nitrogen (TN) and chemical oxygen demand (COD), and it has low biodegradability. In this study, a joint electrochemical system (JES) composed of iron anode reactor (IAR) and Ti/RuO anode reactor (TAR) was constructed to remove both TN and COD from BTLL and improve its biodegradability. The IAR and TAR with the same structure but using different anodes. As a result, JES could simultaneously remove COD and TN by 90.9 ± 0.3% and 90.2 ± 1.0%, respectively. Reduction of nitrite-N by Cu/Zn cathode in IAR and oxidation of ammonium-N by active chlorine in TAR were the major pathways for TN removal, while the COD could be removed by coagulation of iron flocs and oxidation by hydroxyl radicals and active chlorine. Fluorescence spectrum and parallel factor analysis showed that the main components of organics in BTLL were humic-like substances, fulvic-like substances, and soluble microbial degradation products. Humic-like substances were particularly removed by JES, and the remaining organics after electrolysis were some alkanes (e.g., heptane and nonane). Furthermore, decrease in molecular weight and aromaticity and increase in biodegradable substances indicated that the biodegradability of BTLL was effectively improved by the JES. The developed JES is a promising approach for application in the BTLL treatment.