CFD modeling of formaldehyde biodegradation in an immobilized cell bioreactor with disc-shaped Kissiris support

Abstract

Packed-bed bioreactors (PBRs) have been recognized as a breakthrough technology in industrial wastewater treatment plants due to high removal efficiency and low investment and operating cost. A coupled computational fluid dynamic (CFD) model, combining the fluid dynamics with biochemical reactions was developed to simulate the dynamic behavior of formaldehyde (FA) biodegradation by Ralstonia eutropha in an immobilized cell bioreactor with disk-shaped Kissiris pieces operating in batch-recycling and continuous mode. The multiphase CFD model was investigated to promote the design, optimization and scale-up of the existent environmental technologies on the decontamination of aqueous streams. The Eulerian CFD model was developed to evaluate the effect of different inlet substrate concentrations (1.67–20mol/m3 of FA) and feed flow rates (6–60.3mL/min) on the treatment efficiency under unsteady-state condition by visualizing concentration profiles for FA depletion. To validate the CFD model effectively, the theoretical calculations were compared against experimental biodegradation data reported in the literature and the time-dependent simulation results illustrated a satisfactory agreement with the experimental data. The results clearly demonstrated that the bioreactor operating in batch-recycling mode was more efficient in means of pollutant elimination while increasing the feed flow rate and inlet FA concentration had reverse effect on FA removal efficiency of the bioreactor. The Eulerian computations have shown promising results on how fluid dynamics can be correlated with biochemical reaction model (Luong inhibition model) and reasonably predict the formaldehyde concentration variations along the bioreactor.