Measurement of critical tractive force of sponge carrier media in a moving bed biofilm reactor and the application of computational fluid dynamics/discrete element method model simulation

Moving bed biofilm reactors (MBBRs) are commonly used to remove organic pollutants and ammonia from wastewater for water reuse as secondary treatment. In MBBRs, small, free-floating media are introduced into aeration tanks to provide a large surface area onto which microorganisms such as ordinary heterotrophic organisms and ammonia oxidizing organisms, can attach. We measured the settling velocity and the critical tractive velocity of the sponge carrier media in an operating full-scale MBBR aeration tanks. Critical friction Reynolds number, Re _C * was strongly related to the particle Reynolds number, Re _p (r = 0.944, p < 0.01). Based on this, the critical parameters for distinct element method computational fluid dynamics (CFD-DEM) simulations were obtained. The simulation results were compared to the measured deposition in one of the MBBR aeration tanks. Based on the results of the physical model and CFD-DEM simulations, a modified configuration was proposed to reduce deposition.