Co-digestión anaerobia líquida como estrategia circular para valorizar residuos orgánicos y aguas residuales

Abstract

The present study assessed the operational performance and biogas productivity of two UASB (Upflow Anaerobic Sludge Blanket) reactors treating wastewater (WW), one of which (R2) was co-fed with organic waste (OW) derived from food residues under liquid anaerobic co-digestion (L-AcoD). Furthermore, the experiment was structured in five operational phases, reaching a peak organic loading rate (OLR) of 28.66 kgCOD m-3 d-1. In the concluding phase, reactor R2 attained a biogas yield of 5.56 L m-3 WW treated, in comparison to 0.02 L m-3 in the mono-digestion reactor (R1). When extrapolated to a standard wastewater treatment plant (WWTP) with a flow rate of 25 L s⁻¹ (equivalent to 2160 m³ d⁻¹), this would yield 12.01 m³ of biogas daily or 4383.65 m³ annually. In order to maintain this level of performance, it is estimated that 226.8 tonnes d-1 (82,782 tonnes yr-1) of OW would be necessary, representing a significant diversion from landfill. This reduction contributes not only to the minimization of OW, but also to energy self-sufficiency in WWTPs, thereby supporting decarbonisation strategies. The bromatological analysis of OW revealed carbohydrate-rich substrates, with specific fractions (e.g., banana peels) influencing effluent color and reactor performance. Nevertheless, the process stability is ensured by proper dilution (10% v/v) and pH buffering. These findings emphasize the viability of L-AcoD as a decentralized circular economy solution for Latin America, offering synergistic benefits in waste reduction and renewable energy generation.