Simultaneous Removal of Nitrogen and Refractory Organics from a Biologically Treated Leachate by Pulse Electrochemical Oxidation in a Multi-channel Flow Reactor

Abstract

Electrochemical oxidation (EO) is often used in the advanced treatment of refractory wastewater. However, in a conventional EO process of direct-current (DC) power supply, oxide layers often form on the anodes, which not only hinder the oxidation reaction on them but also cause higher energy consumption. In this paper, a biologically treated leachate (BTL) of municipal solid waste (MSW) was comparably treated by EO with DC (DC-EO), monopulse (MP-EO), and double pulse (DP-EO) power source models in a home-made multi-channel flow reactor. The effects of process parameters of current density (IA), superficial liquid velocity (UL), pulse frequency (fP), duty ratio (RD), and so forth on the removal efficiency of chemical oxygen demand (COD) (RECOD), total organic carbon (TOC) (RETOC), and total nitrogen (TN) (RETN) were investigated simultaneously. Average energy consumption (EC¯) and organic composition of the treated effluent of DC-EO and MP-EO were also compared comprehensively, and a new mechanism of MP-EO has been proposed accordingly. Under optimal conditions, 2 L of BTL was treated by MP-EO for 180 min, and the RECOD, RETOC, and RETN could reach as high as 80, 30, and 80%, respectively. Compared with DC-EO, the EC¯ of MP-EO is reduced by 69.27%. Besides, the kinds of organic matter in the treated effluent of MP-EO are reduced from 53 in the BTL to 11, which is much less than in the DC-EO process of 29 kinds. Therefore, the MP-EO process exhibits excellent removal performance of organics and TN and economic prospects in the treatment of refractory organic wastewater.