Research work in the field of heterotrophic denitrification was done in Dresden between 1976 and 1980; in 1985 it was resumed with new objectives. A fluidized-bed reactor with a floatable granular carrier material was developed and represents a novel solution. The process could be essentially improved by making use of the NEBIO tube reactor, where the fluidized bed is produced by downward flow of the water to be treated. The circulation of a partial stream is not required. In February 1989 a pilot plant with a capacity of 650 m3/d was taken into operation. Due to the good results, further work has been sponsored by the Bundesministerium für Forschung und Technologie from the middle of 1990. Planning work for a demonstration plant was carried out in 1991. In August 1992 two reactors with a water throughput of 6,100 m3/d were already started, and the aftertreatment unit with aeration, multi-layer and activated-carbon filter, pH adaptation by gas exchange and a two-stage disinfection with chlorine was taken into operation. In November 1992 for the first time water was fed into the supply system. The NEBIO tube reactor process proved to be a reliable and safe process for the biological elimination of nitrate. Continued research work will focus on the development of models for the degradation processes in the tube reactor and the optimisation of the overall technology.