An evaluation of different types of air diffusers applied to the biological landfill leachate treatment was executed. The optimization of performances in the experimental scale was determined evaluating the pressure evolution at different inlet air flows for two types of elastomeric polyethylene diffusers. The microscope analysis permitted the definition of the chemical compounds precipitated on surface of the diffusers and inside the pores. The compounds were mainly composed of calcium and iron deposits. Formic acid solution was identified as the most efficient for the removal of the insoluble salts. During the experimental phase, the elastomeric polyethylene diffuser was found to be the best suited to the biological treatment of matrices at a level of high alkalinity (2900 mgCaCO(3)l(-1)). This result determined the replacement of 500 rigid diffusers in the full scale biological reactor. The substitution incremented the standard oxygen transfer efficiency to 16% and the standard aeration efficiency to 5.1 kgO(2)kWh(-1) with an improvement of the ammonia performances and of energy saving. (C) 2014 Elsevier B.V. All rights reserved.