Investigation and improvement of electrochemically activated peroxydisulfate systems for treating incineration leachate

The aim of this study was to develop processes to efficiently treat incineration leachate with complex pollutant compositions. The performance of the electrocoagulation-activated peroxydisulfate system with an iron anode (Fe-EC/PDS) and the electrooxidation-activated peroxydisulfate system with Fe²⁺ addition (EO/Fe²⁺/PDS) for treating actual low-concentration incineration leachate (LCIL) was compared. Under the optimal operating conditions determined through experiments, the Fe-EC/PDS system ([PDS]₀ = 33.6 mM, current density = 13.07 mA/cm², natural pH₀ of LCIL (≈ 7), and reaction time = 60 min) could achieve 50.26% CODcr removal, which was higher than the value of 48.73% achieved in the EO/Fe²⁺/PDS system ([PDS]₀ = 50.4 mM, [Fe²⁺]₀ = 33.6 mM, current intensity = 26.14 mA/cm², natural pH₀ of LCIL, and reaction time = 120 min), and the reaction rate of the former was more than twice that of the latter. Furthermore, detailed analysis revealed that these two systems demonstrated different treatment capabilities for different types of organic contaminants, although both produced the reactive species SO₄^∙− and HO^·. To achieve high efficiency in treating incineration leachate, hybrid processes that combined the medium-pressure ultraviolet activated peroxydisulfate system (MPUV/PDS) with Fe-EC/PDS and EO/Fe²⁺/PDS, respectively, were constructed for the first time. The hybrid processes exhibited good pollutant treatment performance, reducing CODcr in the high-concentration incineration leachate (HCIL) from 1401.18 mg/L to 88.58 mg/L within 200 min. Moreover, it was found that the use of MPUV/PDS for pretreatment could result in higher CODcr removal in the Fe-EC/PDS and EO/Fe²⁺/PDS systems (18.33% and 37.19% increase, respectively) with lower specific energy consumption (SEC) by mitigating the interference from leachate chemical background.