The denitrification potential of a continuous denitrifying granular-sludge bioreactor for concentrated nitrate/nitrite wastes was investigated. Granules were cultivated using nitrite as sole electron acceptor. Complete denitrification could be achieved at nitrite, nitrate, and nitrate-nitrite mixture (50:50) loading rates upto 2.7, 3 and 3g NL(-1)d(-1), respectively. The maximum nitrite and nitrate reduction capacities were limited by the biomass concentration. Removal of nitrate and nitrite was studied with constant biomass concentration at different pH values. A lower pH value resulted in a considerable increase of inhibitory effects of both nitrite and nitrate whereby nitrate exhibited the more significant impact.