Synergistic mixtures of biocides and their use to control the growth
of microorganisms in aqueous systems are disclosed. The method of using the synergistic
mixtures entails adding an effective amount of a nitrogenous compound activated
by an oxidant and at least one non-oxidizing biocide to an aqueous system. The
amount of activated nitrogenous compound and non-oxidizing biocide is selected
to result in a synergistic biocidal effect.