Treatability of landfill leachate combined with sanitary sewage in an activated sludge system

Landfill leachate is one of the major problems generated from waste; it has high concentrations of biodegradable and refractory organic and inorganic matter such as ammonia and heavy metals. The combined treatment of leachate with sewage has been used in various sewage treatment plants in the world. However, there are still many questions and uncertainties about the process, especially the effects of adding leachate to the treatment system. In this context, the objective of this work is to evaluate the efficiency of combined leachate/sewage treatment in activated sludge under different conditions. Treatability experiments were carried out using a bench scale (SBR) process using the volumetric proportions of 0 (control), 2 and 5% leachate under different experimental conditions. Experiment 2 (leachate pre-treated by alkalinization and air stripping) was technically more feasible, achieving removal efficiencies of BOD, COD and DOC above 97%, 82%, 60%, respectively, and the highest diversity indices of the bacterial and eukaryotic communities and flake structure stability were observed up to a volumetric ratio of 2% of pre-treated leachate. The DGGE technique used showed that populations of eukaryotes were apparently the most affected with increasing proportions of 2%-5% of the mixture, mainly for experiments 3 (B3R2) and 4 (B4R4), where the lowest diversity indices of these populations were found.