The aim of this study was to determine an appropriate combination for effective and economical COD and nitrogen removal from landfill leachate. Biological (nitrogen) treatment was performed with the autotrophic nitrogen removal (ANR) process. The (post-) treatment performances of (i) ozonation alone, (ii) adsorption to granular activated carbon (GAC) alone, (iii) the combination of 03 and GAC and (iv) an integrated approach with continuous recirculation of ozonated ANR effluent were investigated. It was observed that ANR post-treatment with ozonation was able to remove only 15.2% of residual COD and 14.0% of total nitrogen in the effluent whereas using activated carbon a 73.6% removal efficiency of COD and 17.3% of total nitrogen was achieved. The best performance was obtained for an ANR post-treatment combination of ozonation and GAC, ensuring a high removal for both COD and total nitrogen. When different ratios of zonated effluent were mixed with the influent of the ANR, it was found to be possible to reach COD removal as high as 40% in the ANR with a slightly decrease in nitrogen removal of around 70-80% compared to respectively 5.31% (COD) and 85.9% (total nitrogen) when no ozonated leachate was recycled to the ANR reactor. Taking the overall performance and operational expenses into account, a combination of ANR biological treatment and its different (post-) treatments (ANR + zonation + GAC) results in a good performance and a lower cost compared to traditional treatment. (C) 2015 Elsevier B.V. All rights reserved.