Membrane-concentrated landfill leachate (MCLL) is a type
of recalcitrant
wastewater with extremely low biodegradability. Identification of
the recalcitrant components and their degradation characteristics
is crucial for developing effective treatment strategies. In this
work, spectroscopic techniques were integrated with chemometrics and
Fourier transform ion cyclotron resonance-mass spectrometry to track
the compositional changes of dissolved organic matter (DOM) in MCLL
during Cu-Fenton treatment. The degradation of both fluorescent and
chromophore components followed pseudo-first-order kinetics during
the Cu-Fenton process, with the sequential order of fluorescent DOM
(terrestrial humic-like > microbial humic-like) > chromophore
DOM
(aromatic structure > conjugated unsaturated structure). The degradation
characteristics of DOM in MCLL exhibited variations in response to
elemental compositions and molecular structure. Nitrogen-containing
compounds showed an increase in relative abundance, while sulfur-containing
compounds progressively decreased. Lipids, aliphatic/proteins, aromatics,
and lignin/carboxylic-rich alicyclic molecule-like structure with
a low O/C ratio were effectively removed, resulting in the transformation
of DOM from an unsaturated redox state to a saturated oxidation state.
This study provides a comprehensive insight into the transformation
of DOM in MCLL during the Cu-Fenton process, which demonstrates its
potential as a promising technology for refractory wastewater treatment.