CFD approach for pumped-recirculation mixing strategy in wastewater treatment: Minimizing power consumption, enhancing resource recovery in commercial anaerobic digester

Abstract

In present study, three-dimensional computational fluid dynamics (CFD) simulation of a real and working sewage treatment plant (anaerobic reactor) was performed by selecting standard k-ε turbulence model to define the turbulent flow. Three geometrical configurations were created for simulation by varying the plane of inlets. Providing two bottom suctions, two bottom inlets and two to four top inlets, and depending upon the configuration employed, recirculation was incorporated. Four different cases of mass flow rates (40, 60, 70, 80 Kg/s) for each suction was studied for first configuration. The results showed that suction mass flow rate of 70 Kg/s was most acceptable mass flow rate as it provided complete mixing condition with savings of 14.3 % power compared to mass flow rate of 80 Kg/s. By choosing multiple planes of inlets instead of single plane; suction mass flow rate of 60 Kg/s was observed to be the acceptable mass flow rate as it saved 14.3 % power compared to 70 Kg/s mass flow rate with single plane inlets. Hence, configuration-3 which had two bottom suctions, four top inlets and two bottom inlets in two perpendicular XZ and YZ-planes was considered the best geometrical configuration for mixing with minimum power consumption.