Potencial de geração de metano via codigestão anaeróbia de lixiviado de aterro sanitário e efluentes do tratamento de esgoto sanitário.

Abstract

The sustainable management of urban effluents, including activated sludge and scum from sanitary sewage treatment, as well as landfill leachate, is crucial for minimizing environmental impacts and harnessing energy resources. This study investigated the anaerobic co-digestion of these wastes, aiming to maximize methane (CH₄) yield and minimize pollution potential. These co-substrates were selected based on a literature review, which suggested that a ternary mixture could yield satisfactory results. Furthermore, this choice is justified by the fact that these effluents are found in landfills, either as a source (leachate) or as a destination (residual activated sludge and scum), pointing to a logistical benefit in the availability of these materials. The research was structured in two phases: (1) Biochemical Methane Potential (BMP) tests with a simplex-centroid experimental design (12 mixtures), analyzing volumetric proportions of leachate (LEA), residual activated sludge (RAS), and scum (S), and (2) operation of an anaerobic fixed-bed reactor (AFBR) with upward flow, subjected to hydraulic detention times (HDT: 15–45 h) and volumetric organic loads (VOC: 11.58–43.04 g COD/L.d). In the BMP, the mixture relative to the center point of the design (33.33% LEA-RAS-S) presented the highest CH₄ yield (435.4 ± 13.2 mL/g VS) and the best synergistic effect, evaluated by the Co-digestion Impact Factor (CIF), which relates the PBM yield to the yield weighted by the proportions of the substrates based on the results of the mono-digestion yields, with CIF = 1.7 ± 0.1. LEA mono-digestion did not generate CH₄ due to the recalcitrance of the constituent organic matter, attributed to the low biodegradability of the material. Soluble COD removal reached 74.88% in mixtures with 66.66% ESC, highlighting the contribution of biodegradable organic matter from the scum. Based on the PBM results, the desirability analysis recommended an optimized mixture in terms of CH4 yield and soluble chemical oxygen demand (COD) removal of 25.37% LEA, 36.37% RAS, and 38.26% S. In the AFBR, the condition with an HDT of 30 h and a VOC of 21.21 g COD/L.d was the most optimized, with a productivity of 0.77 ± 0.23 L CH₄/L.d, an average CH₄ content of 80.6%, and a removal of 44.2% of the total COD. The AFBR remained stable in its biochemical functions throughout the experiment, as indicated by the IA/PA ratio of 0.3–0.4 and the VFA/TA ratio of 0.1–0.35, as well as the accumulation of volatile organic acids in the vertical profile of the reactor. However, operational challenges were encountered, such as biomass clogging and washing, which reduced efficiency due to physical parameters, requiring interventions to optimize biomass retention. It is concluded that anaerobic co-digestion is technically feasible for integrating waste already available in landfills. For future studies, we recommend validating the optimized mixture in the MBT, performing metagenomic analysis of the microbial consortium, and better evaluating the type of reactor for system operation.