Improved landfill leachate quality using ozone, UV solar radiation, hydrogen peroxide, persulfate and adsorption processes

Advanced oxidation processes based on ozonation, UV solar radiation, hydrogen peroxide, and persulfate were tested for the complete treatment of a specific landfill leachate. As a post-treatment of the advanced oxidation process, an additional adsorption process was carried out using a natural zeolite. Application of the UVsolar/O-3/H2O2 process required 140 min of irradiation and the consumption of 0.67 g/L H2O2 to eliminate 56% and 17% of colour and chemical oxygen demand (COD), respectively. When adding persulfate to the system (UVsolar/O-3/H2O2/S2O8-2), colour and COD were reduced by 29% and 77%, respectively, with a 0.2 g/L concentration of S2O8-2 requiring 250 min of irradiation time. In an experimental run with landfill leachate, adsorption post-treatment with a natural zeolite resulted in 36%, 99%, and 18% total reductions in COD, ammonium, and chloride, respectively. In another experimental run, adsorption with a zeolite was used as a pre-treatment for the advanced oxidation process (UVsolar/O-3/H2O2 and UVsolar/O-3/H2O2/S2O8-2). The results were similar to those for adsorption post-treatment, with 30%, 90%, and 20% total reductions in COD, ammonium, and chloride, respectively. Despite improvements, some measured parameters of treated landfill leachate still exceeded Chilean regulations for water quality. Furthermore, Lactuca sativa seeds did not germinate after irrigation with 100% treated landfill leachate or dilutions above 3%. Finally, EC50 values were enhanced during treatment, going from 0.002% for raw landfill leachate to 1.179% after the adsorption process.