Codigestão anaeróbia de esgoto sanitário, lixiviado de aterro sanitário e glicerina bruta: da seleção de proporções ao desempenho em reator de leito fixo.

Abstract

Waste disposal and energy recovery has become a global priority, so landfills and Anaerobic Digestion (AD) have been frequently mentioned as options. Furthermore, AD allows biogas production, while landfills intrinsically generate leachate, an effluent difficult to be treated biologically, then, Anaerobic Co-digestion (AcoD) comes as a viable solution. Sustainability, generation volume, and composition are key-factors to be considered when selecting effluents for AcoD application. Thus, this study aimed at using Municipal Wastewater (MWW), Landfill Leachate (LL), and Crude Glycerin (CG) from biodiesel production as substrates for AcoD, evaluated in two phases. Phase 1 involved batch tests using Response Surface Methodology (RSM), while Phase 2 involved the use of a Fixed-Bed Anaerobic Reactor (FBAR) under continuous operation. Acetic and propionic acids were predominant in both phases, but the inhibition associated with propionic acid occurred due to accumulation only in Phase 1. In this phase, an optimal point of 8.584% LL, 3.376% CG, and 88.041% MWW was obtained by optimizing the response-variables: soluble COD removal (%), methane production (mL NCH4.⋅LREACTOR−1), and the Volatile Fatty Acids/Total Alkalinity (VFA/TA) ratio at the end of the experiment. Experimental validation from the optimal point in Phase 1 failed to confirm the predicted results, thereby invalidated the optimized point. However, the objective of maximizing methane production was achieved with a yield of 329.08 mL NCH4.g sCODremoved−1. This has shown that the determined ratio represents a promising mixture. In Phase 2, the mixture identified in the previous phase was evaluated in a FBAR at three different Hydraulic Retention Times (HRTs): 10, 5, and 1.9 days. Analysis of Variance (ANOVA) indicated that the optimal HRT for FBAR operation with the influent composition (8.584% LL, 3.376% CG, and 88.041% MWW) was five days. This condition achieved average total and soluble COD removal of 91%, associated with an average methane yield of 238 mL NCH4.g CODremoved−1, under stable operation (VFA/TA < 0.4).