Swirling fluidization in an anoxic membrane bioreactor as an antifouling technique

Scarce attention has been placed on the geometry of anoxic fluidized bed membrane bioreactors (AFMBR) affecting the hydrodynamic pattern inside the reactor and, consequently, on the mechanical cleaning driven by granular carbon (GC) around the membrane. The present work evaluated the application of a swirling fluidization, produced by a tangential inlet in a reactor with hydrocyclone geometry, with the aim to avoid membrane fouling during the performance of a denitrification process. The study includes 3D-hydrodynamic description of the flow and particles fluidization through computation fluid dynamics (CFD), experimentally validated with the particle image velocimetry (PIV) technique. Water shear stress and GC particles momentum acting over the membranes were also assessed, in addition to monitoring filtration and denitrification performance. The conical section showed higher shear stress and particles momentum as compared to the cylindrical zone. Soluble microbial products (SMP) accumulated on the membrane walls with lower shear stress and particles momentum. The operation of the AFMBR was maintained with a continuous permeate flow without any change in suction pressure and the nitrate removal efficiency was above 90% with negligible accumulation of NO2− and N2O in the denitrifying process. This novel reactor configuration could be suitable for the treatment of industrial wastewaters.