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Highlights • The MW-Fe0/H 2 O 2 process was used to treat concentrated landfill leachate. • Reaction parameters and the degradation mechanism were systematically studied. • Refractory organics were degraded by the synergistic effects of MW, Fe0 and H 2 O 2. • Various analyses proved that refractory organics were efficiently degraded. • The reaction mechanism of the MW-Fe0/H 2 O 2 process has wide applicability. Abstract To study the treatment effect and mechanism of a combined microwave (MW)-Fe0/H 2 O 2 Fenton-like process on concentrated landfill leachate, the effects of initial pH, Fe0 dosage, H 2 O 2 dosage, MW power and reaction time on the removal of organic substances were investigated. The phase change of Fe0 before and after reaction and its catalytic mechanism were investigated using multiple analytical techniques. Results showed that the removal efficiencies of chemical oxygen demand, UV 254 and color number were 58.70%, 85.69% and 88.30%, respectively, at initial pH of 2.0, Fe0 dosage of 0.5 g/L, H 2 O 2 dosage of 20 mL/L, MW power of 400 W and reaction time of 14 min. Comparison of different Fenton-like processes indicated that the MW-Fe0/H 2 O 2 Fenton-like process was the most efficient and significantly decreased the aromaticity degree, molecular weight and condensation degree of organic substances in the leachate. The fluorescence peak of concentrated leachate exhibited a blue-shift in the MW-Fe0/H 2 O 2 process, further indicating that the condensation degree of humic substances declined and molecular weight remarkably decreased. The mechanism exhibited an advanced oxidation effect of a heterogeneous Fenton reaction between iron oxide and H 2 O 2 , as well as of adsorption and precipitation effects of iron-based colloids, on organic substances. Moreover, thermal and non-thermal effects of MW accelerated these reactions, achieving fast removal of organic pollutants in the concentrated landfill leachate. Overall, the results of this study showe that the MW-Fe0/H 2 O 2 process is an effective and promising method to handle concentrated landfill leachate. [ABSTRACT FROM AUTHOR]

• DOM composition in landfill and incineration leachate was systematically compared. • Transformations of the DOM molecular compositions by MBR/NF were investigated. • Phenolic compounds, polyphenols and polycyclic aromatics enriched in MBR leachate. • NF lowered the DOM abundances but with more complex DOM in the NF concentrate. • Coagulation in conjunction with an advanced O 3 /H 2 O 2 process was used to treat NF concentrate. Transformations of the molecular compositions of dissolved organic matter (DOM) in incineration leachate (IL) were investigated. Results revealed that DOM in IL had a lower oxidation degree than that in mature MSW landfill leachate (LL). Moreover, aliphatic compounds (2.0 ≥ H/C ≥ 1.5) having the highest bioavailability were the most abundant type of DOM in IL, making IL significantly more biodegradable than LL. Under microbial actions, etc., DOM composed of phenolic compounds (aromaticity index (AI) ≤ 0.50 and H/C < 1.5), polyphenols (0.66 ≥ AI > 0.50) and polycyclic aromatics (AI > 0.66) in MBR-treated effluents were enriched and more diverse than in the untreated leachates. Nanofiltration (NF) dramatically lowered the relative abundances of phenolic compounds, polyphenols and polycyclic aromatics in effluent generated by treatment of IL in a MBR. Although the concentration of DOM in NF effluent was comparatively low, the DOM compositions in the resulting NF concentrate were nearly identical to those in MBR effluent, but were more complex than those in an international standard DOM due to a higher content of CHOS and CHONS heteroatomic compounds. Particularly, coagulation in conjunction with ozone/hydrogen peroxide oxidation process were dramatically reduced most polyphenols and polycyclic aromatics from the NF concentrate. [ABSTRACT FROM AUTHOR]