Modeling and dynamic simulation of a two-stage pre-denitrification MBBR system under increasing organic loading rates

Biofilm-based wastewater treatment systems have become attractive due to their numerous advantages when compared to other suspended growth processes. However, the mathematical modeling of these reactors is relatively complex, since it has to consider a wide range of phenomena to accurately describe the process behavior. This work deals with the modeling of a two-stage MBBR system run in pre-denitrification mode for the removal of organic matter and nitrogen from wastewater. The model development took into account diffusive phenomena and kinetics in a homogeneous biofilm composed of different bacterial functional groups (namely heterotrophs and nitrifiers). The thickness of the biofilm was treated as a variable, given that detachment of adhered biomass took place. The suspended biomass fraction was also considered to remove the pollutants by means of Monod-type kinetics associated with the activated sludge model. The dynamic behavior of the components involved in the system and their spatial distribution in the biofilm obtained from simulated data showed good agreement with those reported in the literature, demonstrating the reproducibility of the model and encouraging future applications in full-scale MBBR plants.