Ozonation of biologically treated landfill leachate: treatment efficiency and molecular size distribution analysis

A wide range of ozone doses were used to oxidise biologically treated Clover Bar landfill leachate, and results were compared to those of a previous study that involved aged raw leachate. The COD, BOD5 and colour of the leachate were measured prior to and after ozonation. The molecular size distribution of each sample was also analysed. At an ozone dose of 2.6 g l(-1), COD and colour removal efficiencies were 47% and 91%, respectively, while BOD5 increased by 324%. The BOD5/COD ratio increased from 0.02 prior to ozonation to approximately 0.2 following an ozone dose of 5.5 g l(-1), indicating improvement in the leachate biodegradability. Ozonation was very effective in reducing the concentration of organic compounds with molecular weights larger than 300 Dalton. After ozonation, no new peaks representing small molecules were observed. Relationships representing ozone dose, COD, BOD5, and the BOD5/COD ratio, as functions of total peak area of molecular size distribution, were determined.