Physical and chemical treatment of a nitrified leachate from a municipal landfill

Leachate from a Swedish municipal landfill in the methanogenic phase was nitrified and then treated by various physical and chemical methods: oxidation with Fenton's reagent and with ozone, precipitation with ferric chloride and with aluminum sulphate and adsorption onto activated carbon. The leachate was analyzed by measuring the COD (chemical oxygen demand), the BOD, (biochemical oxygen demand) and the TOC (total organic carbon). Specific organic compounds were analyzed by GC/MS (gas chromatography and mass spectrometry) while the molecular weight of the organic matter was determined by ultrafiltration. The nitrification process resulted in 20-30% of the COD being removed. The maximum COD removed after nitrification and oxidation was 80% using Fenton's reagent and 54% using ozone. The combination of nitrification and precipitation gave a maximum COD removal of 68% using ferric chloride and 54% using aluminum sulphate, while nitrification and adsorption onto activated carbon gave a maximum COD removal of 76%. A combination of nitrification, precipitation with ferric chloride and adsorption on activated carbon gave a TOC removal of 96%. The ultrafiltrations showed that nitrification and adsorption onto activated carbon were the most efficient processes for the removal of low molecular weight compounds. The GC/MS analyses showed that, for instance, C-3-substituted benzenes and C-2-C-4 substituted phenol isomers were degraded during the nitrification process, while phthalates were unaffected even after treatment with Fenton's reagent or by adsorption onto activated carbon.