Biodegrdn. of [Me(CH2)(9)](2)Me2NNO3 (I) in activated sludge from a com. wastewater treatment plant was studied under laboratory conditions (I concn. 0.06 to 16.0 mg/L). At the low concns., I showed a stimulating effect on the growth of microorganisms. At the highest I conc., an increase in Mohlmann index and a disturbance in the activated sludge operation were obsd. Products of I degradn. did not show any toxic effect on the microorganisms present in the activated sludge.