CFD simulation of the hydrodynamics and reactions in an activated sludge channel reactor of wastewater treatment

This paper presents a complete CFD modelling of a wastewater gas–liquid cross-flow reactor, taking into account hydrodynamics, mass transfer and biological reactions. Transfer processes, kinetics model and assumptions made are described in detail. The simulations have been successfully compared to experimental results obtained in a bench scale reactor. Chemical oxygen demand (COD), nitrate, ammonium and oxygen concentrations have been measured along the length of the reactor and compared to the simulated profiles. A very good agreement has been obtained for the COD and nitrate concentration profiles. Agreement for the oxygen concentration profile is reasonably good with respect to the experimental uncertainty. These results have been obtained without any adjustment of the kinetics parameters. The basics of a three-phase CFD model taking into account the transfer between flocs and wastewater, as well as the inhomogeneous concentration of biomass due to the hydrodynamics of the reactor, are proposed as perspectives.