Biological Aerated Filtration (BAF) is a technology which is today successfully used in more than 500 European wastewater treatment plants. Biofiltration is a compact and modular aerated biological reactor which has several advantages compared with classic technologies like activated sludge with its suspended growth. The main advantages of using biofilters with fixed film biomass are the possibilities to adapt the biological treatment process to a wide range of incoming pollution loads and hydraulic variations. Due to the natural high sludge age of the biofilm in the reactor (ts > 30 days) and the independency of the efficiency of a final settlement tank biofilters are efficient also at relative high temperatures of wastewater. The new generation of standardized biofiltration sBAF is able to treat wastewater steadily, with high efficiency (h>90%) and for lower costs compared to classical technologies.