Modeling pH and temperature effects on the anaerobic treatment of tequila vinasses

BACKGROUND An unstructured mathematical model is proposed to evaluate the effect of key variables on the anaerobic digestion of tequila vinasses and to determine the operating conditions that improve biogas production. Most of the models currently reported do not consider the simultaneous effects of pH and temperature on the process kinetics. Instead, they only recognize the specific operational conditions under which the experiments were conducted. Hence, this work presents a mathematical model that considers the effects of pH and temperature on methane production. RESULTS Experimental data were obtained from the anaerobic treatment of tequila vinasses conducted in a sequencing batch reactor, which was evaluated at two temperatures (32 and 38 °C) and two pH values (7 and 8) to validate the proposed model. Parameter estimation was performed using the Levenberg–Marquardt algorithm yielding a simplified model with high determination coefficients (R2 > 0.99). Moreover, kinetic parameters estimated were consistent physically and statistically. CONCLUSIONS Numerical simulations provide the operating conditions under which methane production can be favored. Therefore, the proposed model might be advantageous in predicting the maximum methane production rate and the maximum organic loading rate that could be used without risking the stability of an anaerobic digestion process. © 2020 Society of Chemical Industry