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

Abstract

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

An Unstructured Model for Anaerobic Treatment of Raw Cheese Whey for Volatile Fatty Acids Production

“…Notice that high determination coefficients are obtained (R 2 > 0.95), which indicates that the proposed model could accurately estimate the key variables' behavior during the anaerobic treatment of raw cheese whey at different pH and temperature conditions. Table 3 shows the estimated parameter values, which agree with the data reported in the current literature and remain in the same order of magnitude for all the operating conditions evaluated [36,37,42]. However, it is noteworthy that, for each experimental condition evaluated, the estimated parameters exhibit a different value, which is associated with the process performance, where, for each condition, different proportions of by-products are obtained ( Table 2).…”

“…Models that include the effect of pH focus on the inhibition in the metabolism of microbial consortia due to changes in pH [35,39], while the effect of temperature has been included in the kinetic model of microbial growth [40,41]. Considering both effects, Moguel-Castañeda et al [42] presented an AD model for tequila vinasses treatment, which obtained good correspondence between the results in experimental tests and model predictions at different conditions of pH and temperature. However, the functions that describe the effects of pH and temperature are empirical relationships that require the estimation of at least five parameters for each function, which can limit the application of the model when insufficient experimental data are available.…”

“…In order to include the effect of pH and temperature in a wide range of operating conditions, it is possible to generate a function of the parameters that exhibit greater variation against changes in those parameters. A simplified model can be described as a first order polynomial of two variables, pH and temperature [42], such as…”

In Focus: ANQUE‐ICCE‐CIBIQ 2019

“…This In Focus section concludes with selected papers devoted to the use of biomass as feedstock and the purification of biofuels. A mathematical model is presented to describe the production of xylitol through a biotechnological route, and the anaerobic digestion of cheese whey and tequila vinasses is considered for the synthesis of biogas . Eventually, the complexity of biofuel purification is addressed using ceramic membranes for the separation of biodiesel from glycerol and other by‐products …”

“…A mathematical model is presented to describe the production of xylitol through a biotechnological route, 10 and the anaerobic digestion of cheese whey and tequila vinasses is considered for the synthesis of biogas. 11,12 Eventually, the complexity of biofuel purification is addressed using ceramic membranes for the separation of biodiesel from glycerol and other by-products. 13 We would like to thank the Editors of the Journal of Chemical Technology and Biotechnology for offering us the chance to prepare the ANQUE-ICCE-CIBIQ 2019 Special Issue.…”