Medical & Clinical Research

Author(s): Lakshmi. N. Sridhar

The anaerobic digestion process is highly nonlinear. This complexity arises from the interconnected, multi-stage biochemical reactions involving various microorganisms, influencing factors like pH, temperature, and substrate concentration. Understanding and controlling this nonlinearity is crucial for optimizing biogas production and wastewater treatment. Several factors must be considered, and multiple objectives must be met simultaneously. Bifurcation analysis and multi-objective nonlinear model predictive control (MNLMPC) calculations are performed on two dynamic models involving anaerobic digestion. The MATLAB program MATCONT was used to perform the bifurcation analysis. The MNLMPC calculations were performed using the optimization language PYOMO in conjunction with the state-of-the-art global optimization solvers IPOPT and BARON. The bifurcation analysis revealed the existence of branch points in both models. The branch points (which cause multiple steady-state solutions from a singular point) are very beneficial because they enable the Multiobjective nonlinear model predictive control calculations to converge to the Utopia point ( the best possible solution) in the models. It is proved (with computational validation) that the branch points were caused because of the existence of two distinct separable functions