A method for the biodegradation of nitroaromatic-containing wastewater, including: (a) providing activated sludge as biological matrix, (b) adding a nitroaromatic-degrading microorganism to the activated sludge, (c) adding nitroaromatic-containing wastewater to the material of step (b) and (d) adding at least one carbon source which is more readily utilizable than the nitroaromatic to be degraded to the material of step (c).