Análisis del estado estacionario inhibido transitorio en la digestión anaerobia del semisólido obtenido en el pretratamiento de aguas residuales de rastro bovino

Abstract

This work aimed to analyze the dynamics of methane production and the conditions leading to a transient-inhibited steady-state phase in anaerobic digestion of physically pretreated slaughterhouse wastewater. Mathematical analysis provided complementary information for applications at the real scale. The pretreatments consisted of autoclaving (120 °C, 1.2 atm, 60 min), which generated the semisolid, and homogenization (30000 rpm, 1 minute). The semisolid was the substrate for a biochemical methane production test, which was carried out at room temperature with a substrate to inoculum ratio of 3:1. The methane production kinetics were complex and followed a stepped curve with four stages: 1) an exponential phase, 2) a transient methanogenesis inhibition phase, 3) a recovery phase and 4) a stationary phase. FTIR analysis showed that both the wastewater and semisolid had high contents of aliphatic and nitrogen compounds, while anaerobic digestion led to reductions of amines I and II, other amides, and aliphatic structures and the production of several amino acids. Mathematical models employed to predict cumulative methane production (Gompertz, Richards, Luedeking-Piret, and Modified first-rate) showed a good fit and low percentage error, although none of them accurately forecasted the transient inhibited steady-state (2nd phase).