Effects of biofilm geometry on deammonification biofilm performance: A simulation study

► Deammonification biofilm performance was strongly sensitive to biofilm geometry. ► Granular biofilm could effectively work in a wide range of DO and have the highest performance as a result of its large surface area for mass transfer. ► Cylindrical biofilm is also effective as the denitrifiers growth was intimately related to a large anaerobic zone caused by geometry. ► DO should be increased abruptly for each biofilm as the shortened HRT, which break the concept that DO should be controlled below 0.5 mg/L.