Study of different integrated physical-chemical plus adsorption processes for landfill leachate remediation

Some integrated processes to deal with landfill leachates have been investigated and their efficiencies expressed in terms of chemical oxygen demand (COD) removal. The systems tested were the result of different combinations of the following single stages: acidic pH shift (elimination of humic substances), ozonation (O-3), coagulation-flocculation with Fe(III) salts, Fenton's oxidation (Fe(III) + H2O2), wet air oxidation (with or without radical promoters), and adsorption onto activated carbon (commercial Norit 0.8 powdered activated carbon). COD removals obtained ranged in the interval of 80-96% for initial COD values close to 11000 mg L-1. None of the processes tested reduced the COD levels sufficiently to allow direct discharge; however, the ratio biochemical oxygen demand (BOD)/COD was significantly increased (up to 1000% in some cases, i.e., from 0.1 to values above 1.0). Total carbon reduction achieved ranged from 60 to 94%, while complete decolorization (measured as the absorbance at 410 nm) was obtained in practically all the combinations investigated.