Wastewater treatment by periodic biofilter characterized by aerobic granular biomass

The paper reports the results of an experimental investigation aimed at evaluating the role of hydrodynamic conditions on generation and main properties of granular biomass grown under aerobic conditions in a periodic packed bed reactor. During the start-up period, the trend of the hydrodynamic shear forces, calculated by a methodology previous developed by authors, provided a key for explaining the process of biomass granulation. The granular biomass was characterized by a high density (i.e., 70-120 gVSS/Lbiomass) that permitted to achieve a biomass concentration such high as 20-38 gVSS/Lbed. The biomass density increased with the increase of shear forces. The EPS (Extracellular Polymeric Substances) content of the biomass (5-7% of the total organic matter) was not affected by hydrodynamic shear forces as well as the biomass protein content. Periodic packed bed reactor applied to a municipal wastewater showed performances very satisfactory with high efficiencies removal (around 90%) for both COD and ammonia, up to an applied organic loading value of 5.7 kgCOD/m3.d, and negligible sludge production.