Exergy analysis of a laboratory-scale upflow anaerobic sludge blanket reactor with sulfate-reducing microorganisms to precipitate heavy metal ions (Cu, Fe, Zn, and Pb) using Aspen Plus

• Published in: Brazilian journal of chemical engineering 2022-03, Vol.39 (1), p.273-287
• Main Authors: Leal-Gutiérrez, Manuel José, Bernal-González, Marisela, Durán-Domínguez-de-Bazúa, María del Carmen, Chávez-Castellanos, Ángel Enrique, Bazúa-Rueda, Enrique Rodolfo
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Industrial Chemistry/Chemical Engineering; Original Paper
• ISSN: 0104-6632; 1678-4383
• DOI: 10.1007/s43153-021-00195-2

Bioreactors with sulfate-reducing microorganisms (SRM) are an option to treat wastewater from the flotation operation of a mine containing dissolved sulfate and metal ions. SRM degrade organic carbonaceous substrates to obtain energy using sulfate ions as terminal electron acceptor and generating hydrogen sulfide to precipitate metals as sulfides. Exergy is a property to aid in the thermodynamic analysis of processes. This study aims to develop an exergy analysis of a laboratory-scale UASB reactor with SRM precipitating heavy metal ions using an electrolyte model in Aspen Plus® process simulation software fitted to experimental data. A simulation model of the biotransformation of sulfates to sulfides and the precipitation of metals was developed using Aspen Plus®. The UASB reactor was split into ten stages to observe the behavior of the compounds and their distribution throughout the reactor. The thermodynamic model selected was the Unsymmetric NRTL electrolyte activity coefficient model proposed by Chen and Evans, model ENRTL-RK in Aspen. Biochemical reactions were simulated using stoichiometric reactors with a double Monod kinetic model. The Aspen Plus® electrolyte model demonstrated that simulating the behavior of ionic species present in the streams of the laboratory scale UASB reactor is feasible. Comparison of calculated values of the Aspen Plus® simulation model and the laboratory scale UASB reactor experimental data showed internal consistency and the Aspen Plus® simulation model could represent them. Exergy analysis with thermodynamic procedures calculated aqueous ionic solutions exergies. The results of the exergy analysis demonstrated that they could provide insight for understanding the performance of a biochemical reactor and its implications in quantifying its environmental benefits. The second law efficiency provides means for further optimization of the process.