Degradation of refractory organic matter in MBR effluent from treating landfill leachate by UV/PMS and UV/H₂O₂: a comparative study

ABSTRACT

This study applied ultraviolet/peroxymonosulfate (UV/PMS) and UV/hydrogen peroxide (UV/H₂O₂) processes to the advanced treatment of membrane bioreactor (MBR) effluent. The degradation efficiency of refractory organic matter and the reaction mechanisms of the two processes were systematically investigated. The results showed that the degradation efficiency of the UV/PMS processes was significantly lower than that of the UV/H₂O₂ process when the PMS concentration was significantly lower than the H₂O₂ concentration, e.g. the UV₂₅₄ removals under optimal conditions were 72.92% and 82.21%, respectively. Additionally, the UV/PMS process could operate over a broader pH range. The degradation efficiency of the UV/PMS process was slightly increased by HCO₃^– and Cl^- due to the activation of PMS, while in the UV/H₂O₂ process, HCO₃^- and Cl^- depressed the degradation efficiency by competing with organic matter to react with reactive oxygen species (ROS). After the two processes, the aromaticity, humification, condensation degree, and molecular weight of refractory organic matter in the MBR effluent were considerably decreased. Fulvic- (HA) and humic-like substances (FA) were greatly degraded by the two processes. The UV/PMS had a superior degradation efficiency for macromolecular HA in the early stage of the reaction, and the UV/H₂O₂ could degrade HA to protein-like substances in the latter stage of the reaction. These differences between the two processes could be attributed to the dominance of different ROS, with SO₄^•- and HO^• dominating in the UV/PMS, and HO^• dominating in the UV/H₂O₂. The results of this study provide theoretical support for the application of MBR effluent treatment.

Highlights

• Comparison on the MBR effluent treatment of UV/PMS and UV/H₂O₂ is studied.

• UV/PMS process can better destroy humic-like substances in the early reaction stage.

• Humic-like substances are transformed into protein-like compounds in UV/H₂O₂ process.

• UV/PMS and UV/PMS performs differently due to their different dominant ROS.

GRAPHICAL ABSTRACT

KEYWORDS:

• Advanced oxidation process
• landfill leachate
• refractory organic matter
• UV-Vis
• EEM

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Authors gratefully acknowledge the finical support of the Chengdu Science and Technology Bureau [grant number 2022-YF05-00802-SN].