Degradation of recalcitrant organic matter in SAARB leachate by a combined process of coagulation and catalytic ozonation.

A combined coagulation and γ-Al2O3 catalytic ozonation process was used to treat semi-aerobic aged refuse biofilter (SAARB) effluent from treating mature landfill leachate. First, the coagulant providing the best pretreatment performance was selected. Then, the coagulated SAARB leachate was further treated in an optimized γ-Al2O3-catalyzed ozonation process. Characteristics of the γ-Al2O3-catalyzed ozonation process were determined, and a reaction mechanism was proposed. FeCl3 provided the best treatment efficiency (chemical oxygen demand (COD) removal of 65.8%, absorbance at 254 nm (UV254) removal of 68.55%, and color number (CN) removal of 79.4%). Under optimized O3 dosage (18.92 mg/min) and γ-Al2O3 dosage (10 g/L), efficiencies of removing COD, UV254, and CN were 54.3%, 82.9%, and 95.9%, respectively, at 30 min. In addition, spectral analysis indicated that fulvic-like substances in ultraviolet and visible regions were effectively degraded in the γ-Al2O3-O3 process and some smaller organic products were produced. Characterization of γ-Al2O3 showed that γ-Al2O3 was relative stable; its morphology and constituent elements did not change much after reaction. In addition, ozonation capacity was enhanced by heterogeneous catalytic effects of γ-Al2O3. The combined coagulation and γ-Al2O3 catalytic ozonation process was proven to be an efficient treatment method for removing bio-refractory organic matter contained in SAARB leachate.