Treatment of high chlorine-containing composting leachate biochemical effluent by Ti/RuO2-IrO2 anodic electrochemical oxidation: Optimization and evolution of pollutants

In this paper, the treatment of composting leachate biochemical effluent (CLBE) by electrochemical oxidation (EO) with Ti/RuO2-IrO2 as the anode could achieve concomitantly organic carbon removal (COD) and nitrogen removal (NH3-N), taking advantage of CLBE inherent high chlorine content. Under the optimal conditions of the current density of 90 mA·cm−2, A/V= 14 m−1, d= 1 cm, pH= 8.34 and Cl- concentration of 6000 mg·L−1, 92.19% of NH3-N and 85.59% of TN could be removed in 40 min, and 100% COD removal could be achieved after 100 min, with energy consumption (EC) of 111.09 kW·h·m−3. And the increase in Cl- concentration could reduce the EC of the EO process. In parallel, constructed simple quantitative accounting models for chlorine-containing and nitrogen-containing species in the EO system and clarified the evolution of them. Cl species eventually exist mainly in the form of free chlorine (by-product AOCL concentration always below 2 mg·L−1), while N species were mainly removed in the form of N2 (≈95.10% of TN). Additionally, the gas chromatography-mass spectrometry (GC-MS) showed that the dominant component of dissolved organic matter (DOM) in CLBE was degraded from the initial unsaturated C21-C30 to the saturated C11-C20. And the Excitation emission matrix (EEM) showed that the EO achieved the non-selective degradation of DOM, the refractory humic acid DOM reached 90.74% removal and the readily biodegradable non-humic DOM removal 92.02%, respectively. These results indicated that the EO technology has broad application potential in the treatment of chlorinated wastewater, and coupling it after biological treatment would be a promising method.