A robust H-infinity controller has been developed to regulate the chemical oxygen demand in an anaerobic digester from the winery industry. A sensitivity analysis was performed, and the parameter set having the most significant effect on the process behavior was identified. The parameters inducing the most sensitivity in the solutions were selected as uncertain; in addition, they were related to kinetic terms and he hydrodynamic regime. Then, a control problem was formulated as robust regulation, and a controller was designed using H-infinity theory to ensure robust stability. The actions of the H-infinity, controller are illustrated through numerical simulations. The controller was found to execute robust regulation facing parametric uncertainties and load disturbances.