Integrated computational fluid dynamics and experimental evaluation of a tubular membrane photoreactor for UVC-driven advanced oxidation at bench- and pilot-scale

Abstract

This study combines computational fluid dynamics (CFD) simulations and experimental data to examine the hydrodynamic and photonic behavior of tubular membrane photoreactors operated under UVC and UVC/persulfate (UVC/PDS) conditions for the removal of organic micropollutants (OMPs). At bench-scale, CFD simulations revealed that the tangential inlet generated a helical flow pattern in the annular reaction zone (ARZ), promoting interaction between radial and axial velocity components. The effect of reflective surfaces on photon delivery was evaluated across three configurations: no reflector and one- and three-sided reflectors (N = 1 and N = 3). Reflective surfaces increased photon delivery to the ARZ, with the N = 3 configuration providing the highest optical efficiency and the best photolytic removal of the selected OMP in both demineralized water (DW) and conventional activated sludge (CAS) effluent. Based on these findings, a pilot-scale reactor preserving the same cross-sectional geometry and incorporating the N = 3 reflector was evaluated. Residence time distribution (RTD) experiments indicated a non-ideal plug flow with moderate axial dispersion, while CFD confirmed the persistence of the characteristic helical flow pattern. Under UVC alone, venlafaxine (VLX) removal remained limited, whereas under UVC/PDS operation removal exceeded 85% across all evaluated conditions. Simulations of the local volumetric rate of photon absorption (LVRPA) and spatial species distributions revealed a strong correlation between photon availability, oxidant distribution, and OMP degradation along the reactor length. These results provide valuable insights into the design of tubular membrane photoreactors and support their applicability for advanced urban wastewater treatment systems.