Characterization of a new biofilm reactors configuration was carried out on a pilot plant performing nitrification, pre- and post-denitrification. Thereby, degradation rate limitations - whether there are related to mass transfer resistances, kinetic or stoichiometry - were determined for the different stages.
The experimental results showed that under certain conditions moderate aeration of the predenitrification stage enhances both denitrification and organic carbon removal due to an acceleration of diffusion rates. Post-denitrification was limited by the addition of C-source exclusively, whereas nitrification was inhibited by elevated organic loadings as well as low temperatures.
The described system offers a certain flexibility concerning BOD removal in the predenitrification stage because of the potentiality of aeration, as well as the possibility of recirculating nitrate very economically enabled by the small head losses in the systems. Furthermore, combination of pre- and post-denitrification with biofilm systems leads to economic and safe processes for advanced elimination of nutrients such as nitrogen and phosphorus.