Ozonation of a pretreated landfill leachate: evaluation of recalcitrance removal

The sanitary landfill method for the ultimate disposal of solid waste material continues to be widely accepted and used due to its economic advantages. However, water infiltrates through the solid waste and a variety of organic and inorganic pollutants will be dissolved and transported. These leachates may contain large amounts of organic matter, as well as ammonia-nitrogen, heavy metals, chlorinated organic and inorganic salts. The removal of organic material is usual the prerequisite before discharging the leachates into natural waters. In the search for an efficient method for the recalcitrance removal of organic matter from landfill leachates, ozone-based processes with or without UV radiation and/or iron catalyst were studied. These treatments were compared with Fenton oxidation as a reference technique. The investigated leachate was pretreated by a biological process combined with ultrafiltration. A certain amount of refractory compounds remains present in the leachate. Based on the results, the contribution of the UV radiation and the iron catalyst is discussed. At lower ozone dosages, the partial oxidation efficiency is reduced compared to ozonation only and therefore, a better mineralisation of the organic matter is achieved. Finally, the best results are obtained by the Fenton oxidation, however, due to foam formation the treatment of the leachate at low pH values is not recommended.