Different Fenton Treatments on Diverse Landfill Organics: Discover the Underestimated Effect of Derived-DOM

Fenton is one of the most promising processes for the removal of dissolved organic matter (DOM). It has always been highly suspected that derived-DOM would be generated during Fenton reaction, but there is lack of direct evidence at the molecular level. The present study explored the molecular properties of the derived-DOM of five common Fenton technologies for degradation of nine landfill organics including leachates and concentrates based on UPLC Orbitrap MS/MS analysis. The comparative results confirmed that DOM derivation was essential for Fenton technologies, with the DOM derivation rate as high as 17.3%-70.3%. The derived-DOM are dominated by trace organic contaminants (CHON-DOM), and typical new contaminants (PPCPs, flavors, etc.). Heterogeneous Fenton had significantly lesser derived-DOM (35.1% ± 16.9%) than other Fenton technologies. Among all landfill organics, medium leachate was most likely to derive DOM (51.4% ± 13.9%), while unexpectedly old leachate had the lowest derivation rate (32.0% ± 5.3%). In the overall membrane treatment process, the secondary membrane concentrate is more susceptible to DOM derivation (43.4% ± 5.5%-49.6% ± 3.8%) than the primary membrane concentrate (40.7% ± 14.1%), and the elements and subcategories composition and molecular property indexes of the derived-DOM become more complex. On the contrary, the DOM derivatization rate of the biological treatment effluent after Fenton treatment was much lower than that of the various concentrates after Fenton treatment and the molecular property are simpler. Therefore, Fenton may replace the membrane process directly as a deep treatment process after biological treatment of landfill leachate. These information would help the selection and application of Fenton technologies.