Nitrogen removal via nitrite has recently gained increasing interest because of its associated economic savings when compared to classical nitrogen removal technologies, in which the ammonium is fully oxidized to nitrate. To improve the capacity of the N-removal via nitrite, it is necessary to develop a robust technology that is able to partially nitrify at higher nitrogen loading rates (NLRs). Recently, a ratio control strategy was successfully applied to biofilm airlift reactors to obtain full nitritation (100%ammoniaconversion to nitrite) under stable operating conditions, the so-called automatic control for partial nitrification to nitrite in biofilm reactors (ANFIBIO).
Technology transfer was enhanced by 2010VALOR00096 (Generalitat de Catalunya) and a pilot plant installation was placed in a Catalan waste water treatment plant to demonstrate the concept. The pilot plant is able to perform full nitritation at a volumetric nitrogen loading rate of 2 g of N / L /day at 30 °C.