Avaliação do desempenho do uso de biorreator com membranas inoculado com leveduras (Saccharomyces cerevisiae) no tratamento de lixiviado de aterro sanitário

Abstract

The landfill leachates are effluents with great complexity and high pollution potential. The physico-chemical methods are expensive and conventional biological treatments, used alone, are insufficient to suit this effluent to standards legislation. In this context, arises the membrane bioreactors, which allow the total retention of the microbial cells in the bioreactor, resulting in a more effective system for biological degradation. The bacterial sludge, normally used in bioreactors, has shown limitations for the degradation of recalcitrant organic compounds from the leachate. In contrast, fungi and yeasts have high capacity of breaking and uptake the pollutants of difficult degradation. Thus, the objective of this study was to evaluate the performance of a MBR inoculated with the yeast Saccharomyces cerevisiae biomass in the treatment of landfill leachate. The work was divided into four stages: first, the leachate was characterized; then, the tolerance of S. cerevisiae to leachate was determined; in the third step, the acclimatization of biomass occurred in MBR; and, in the fourth, the operational performance of MBR was rated in terms of pollutant removal efficiency and fouling, monitored the microbial species present in the sludge and determined the fraction COD inert of the leachate to the biomass of the MBR. The leachate after ammonia removal by air stripping was used and the inoculum employed was a lyophilized baker's yeast. The MBR operated with permeate flux of 5.0 L/h.m2, HRT of 48 h and pH of 3.5. Average removal efficiencies of COD, color, NH3 and humic substances of 68, 79, 68 and 50%, was obtainedrespectively, during the stage after acclimatization. The fraction of inert COD of the leachate observed for the MBR sludge was about 30%. Severe contamination by other microbial groups occurred in the biological tank of the BRM. The system performed well in relation to membrane fouling when compared to MBR systems with conventional sludge. This fact is possibly associated with the low average production of EPS in the system as well as the low viscosity of the sludge. Despite being at high concentrations, the SMP were not a major factor in membrane fouling. In the other hand, aeration of the module and mixed liquor suspended solid (MLSS) concentration appear to have been the main factors influencing the loss of membrane permeability during the system operation. Anyway, the use of MBR with "fungal sludge presented itself as a great alternative for the treatment of landfill leachate with a high content of recalcitrant compounds.