Toxic response of Nitrosomonas europaea to copper in inorganic medium and wastewater

Abstract A study was conducted to examine potential toxicity of copper(II) and its species in nitrification processes monitoring the oxidation of ammonia by Nitrosomonas europaea . The copper toxicity data were analyzed in terms of chemical speciation computed by a chemical equilibrium model. Increased toxicity with increasing ammonia concentration was observed for both the inorganic medium and the wastewater, that is analogous to the result reported for a full-scale nitrifying activated sludge plant. The 50% inhibition concentration (IC 50 ) of total copper(II) decreased from 0.5 to 0.01 mg l −1 Cu(II) as the total ammonia concentration was raised from 3 to 23 mg l −1 as N. On the basis of statistical correlation, the increasing copper toxicity with increasing ammonia is apparent, which is further explained by the formation of copper-ammine complexes. The toxic response of N. europaea observed in the inorganic medium was defined as a function of the logarithmic activities of copper-ammine complexes.