Ozonation of a landfill leachate: evaluation of toxicity removal and biodegradability improvement

This work shows an evaluation of treatments for the leachate produced at the Gramacho Municipal Landfill in Rio de Janeiro state, Brazil. This leachate has very peculiar characteristics, with a high salinity level and very low biodegradability (BOD5/COD of 0.05). A sequence of processes was employed in the treatment of this leachate. Initially, a physicochemical treatment was used, while the second stage consisted of application of ozone to improve the biodegradability of the leachate. The final stage comprised a biological treatment. The physical-chemical treatment led to COD and DOC removal levels of 40 and 25%, respectively, with the use of Al2(SO4)3. The sequence of treatments proposed brought good results, with an increase in the BOD5/COD ratio from 0.05 to 0.3 after ozonation. The toxicity tests performed using Brachydanio rerio and Poecilia vivipara showed that the toxicity of the leachate had hardly been reduced by ozonation. These results are in agreement with the fact that, despite the higher BOD5/COD ratio, the biological process did not present a good performance. The total average removal levels of COD and DOC achieved using the combined treatment were 73 and 63%, respectively, for an ozone dose of 3.0 g L−1 by the leachate.