Treatment of organic wastewater containing nitrogen and chlorine by combinatorial electrochemical system: Taking biologically treated landfill leachate treatment as an example

This study presents a combinatorial electrochemical system (CES) for the treatment of refractory organic wastewater containing nitrogen and chloride ion. The CES was composed of iron anode reactor (IAR), Ti/RuO2 anode reactor (TAR) and available chlorine removal reactor (CRR). Biologically treated landfill leachate (BTLL) was selected as the treatment object to evaluate the performance of CES. The results showed that CES could simultaneously remove chemical oxygen demand (COD) and total nitrogen (TN) by 94.6% and 98.3%, respectively. Reduction of nitrite-N by cathode in IAR and oxidation of ammonium-N by available chlorine in TAR were the major pathways for TN removal. Fluorescence spectroscopy and parallel factor analysis (PARAFAC) showed that the main organic components in BTLL were humic-like substances and soluble microbial degradation products. These substances were removed by CES and the remaining organics were some hydrocarbons and carboxylic acids. The available chlorine was rapidly reduced into chloride ion by IAR precipitates, thus decreasing the cytotoxicity. In addition, the formation of stable Fe3+ crystals was promoted by the oxidation of available chlorine in CRR, which increased the density of the precipitates and reduced their volume. Therefore, the CES is a promising solution for the treatment of refractory organic wastewater containing nitrogen and chlorine ion.