Optimization of Mixing in IFAS and MBBR Aeration Basins using Computational Fluid Dynamics

While mixing dynamics of activated sludge aeration basins using diffused aeration systems, particularly fine bubble systems, is well understood, there is little body of knowledge available on the mixing dynamics in the aeration basins with biofilm carriers (media). This paper presents first of its kind such an undertaking to design, develop and evaluate the hydrodynamics in IFAS basins at one of its installations in Virginia utilizing Computational Fluid Dynamics (CFD). The CFD modeling and simulations were very useful in evaluating different aeration grid layouts and air flow distributions in the media containing tanks to optimize the most efficient grid layouts and airflow regimes that ensured optimal mixing in the IFAS basins along with maintaining homogenous distribution of the MLSS and biofilm carriers. This approach is promising in terms of its predictive ability, suitability for similar applications and cost savings in the design process.