Computational fluid dynamics modelling of primary sludge classification in an activated sludge process based wastewater treatment plant: Simulating the hydrodynamic behaviour and experimental verification of the classification efficiency

The primary treatment of wastewater, which involves the sedimentation of solid debris, results in the production of primary sludge. This paper presents the computational fluid dynamics (CFD) study of the Rietema type hydrocyclone for primary sludge classification in an activated sludge process (ASP) based wastewater treatment plant. The CFD simulation of hydrocyclone was performed to study the pressure profiles (absolute pressure, total pressure), axial velocity, tangential velocity, particle track and classification efficiency for the experimental validation. The experimental values of concentration factor (CF) for total suspended solids (TSS), fixed suspended solids (FSS) and volatile suspended solids (VSS) were 1.50 ± 0.18, 1.69 ± 0.27 and 1.35 ± 0.21, respectively. The simulation and experimental classification efficiencies were 27.6% and 28.2%, respectively. Furthermore, the results of this study shows that the installation of hydrocyclone for the classification of the primary sludge saves 3194 kWh/year of energy required for wastewater treatment.