Combined biological and chemical degradation for treating a mature municipal landfill leachate

The paper reports the results of a laboratory scale investigation aimed at evaluating the effectiveness of mature municipal landfill leachate treatment by a biological stage, carried out in a periodic biofilter with granular biomass (SBBGR), followed by a chemical oxidation step, performed using ozone or Fenton, for further COD removal. The results show that the biological treatment was able to remove roughly 80% of COD in leachate at an organic loading approximately equal to 1.1 kgCOD/(m3 day). Ammonia removal efficiency was very low (lower than 20%) because of the presence of high salinity and inhibitory compounds. When the leachate was pre-treated in order to reduce considerably the ammonia content, it was found to be possible to reach organic loadings as high as 4.5 kgCOD/m3 day with a decrease in COD removal of only 10%. The biological treatment was characterised by a negligible sludge production. Ozone and Fenton reagent were used to reduce the remaining COD content presumably made up of recalcitrant compounds. The treatment with ozone was able to remove only 33% of residual COD whereas using Fenton reagent an 85% removal efficiency of COD was achieved.