The effect of autochthonous metal ions and humic substances on landfill leachate ozonation: Reactive oxygen species and 3D fluorescence analysis

Ruoyang Zhang, Jiadong Liu, Bo Gao, Mika Sillanpää

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1 Citation (Scopus)

Abstract

This study investigated the ozonation process for landfill leachate treatment, focusing on the impact of autochthonous metal ions (Fe3+, Cu2+, Mn2+, Mg2+) and humic substances on the degradation of pollutants. Our findings revealed that the presence of these metal ions significantly enhanced the generation of hydroxyl radicals ([rad]OH), especially for Fe3+, demonstrating the highest catalytic activity. However, the humic substance attenuated the signals of reactive oxygen species (ROS), particularly the superoxide radical ([rad]O2) in the presence of Cu2+ and Mn2+. These suggested that metal ions could complex with humic substances and further inhibit ROS production. Despite this inhibition, Fe3+ maintained its ROS-generating capacity even in the presence of humic substances, indicating its potential as a robust catalyst in landfill leachate. Batch tests further demonstrated that Fe3+ had the most positive effect on the degradation of sodium humate, as evidenced by a significant reduction in fluorescence regional integration (FRI) values. An integrated membrane bioreactor (MBR) and ozonation system were conducted, which firstly processed activated sludge treatment in the MBR and then pumped into the ozonation system via a peristaltic pump. After ozonation, the leachate overflowed back into the MBR for further treatment, creating a closed-loop system. It was observed that there was a significant reduction in humic substances, with a decrease of 96.31% in the FRI. Parallel factor analysis (PARAFAC) results corroborated these findings, which indicated a marked reduction in the abundance of humic-like substances C-BO-1 and C-BO-4 during the 17 days treatment period. This study revealed the pivotal role of microorganisms, ROS, metal ions, and humic substances in the treatment of landfill leachate. The metal ions presented in the leachate were confirmed to produce ROS during the ozonation process. However, a significant quantity of humic-like substances reduced the reactive ROS through complexation and consumption reactions. Simultaneously, microorganisms in the MBR system consumed humic substances such as C-BO-1 and C-BO-4, which promoted the degradation of contaminants in the landfill leachate. These insights provided implications for optimizing ozonation processes in leachate management, potentially leading to more efficient and environmentally sustainable waste disposal practices.

Original languageEnglish
Article number129433
JournalSeparation and Purification Technology
Volume354
DOIs
Publication statusPublished - 19 Feb 2025

Keywords

  • Landfill leachate
  • MBR
  • Ozonation
  • PARAFAC
  • ROS

ASJC Scopus subject areas

  • Analytical Chemistry
  • Filtration and Separation

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