A bioreactor cascade with a submerged biofilm is proposed to treat young landfill leachate of jbel chakir landfill site south west from capital Tunis, Tunisia. The prototype was run under different organic loading charges varying from 0.6 to 16.3 kg TOC m(-3) day(-1). Without initial pH adjustment total organic carbon (TOC) removal rate varied between 65% and 97%. The total reduction of COD reached 92% at a hydraulic retention time of 36 h. However, the removal of total kjeldahl nitrogen for loading charges of 0.5 kg N m(-3) day(-1) reached 75%. The adjustment of pH to 7.5 improved nitrogen removal to a rate of 85% for loading charge of 1 kg N m(-3) day(-1). The main bacterial groups responsible for a simultaneous removal of organic carbon and nitrogen belonged to Bacillus, Actinomyces, Pseudomonas and Burkholderia genera. These selected isolates showed a great capacity of degradation at different leachate concentrations of total organic carbon. (C) 2011 Elsevier Ltd. All rights reserved.