Methods and apparatuses are described for contacting an oxidizing solution such as an aqueous hydrogen peroxide composition of hydrogen peroxide, at least one additive that catalyzes the decomposition of the hydrogen peroxide into hydroxyl radicals, and a biocide with an atmospheric effluent containing odorous and/or noxious components. These components are absorbed by the aqueous hydrogen peroxide composition to produce an atmospheric effluent having reduced amounts of the odorous and/or noxious components. Various methods are described for adding the hydrogen peroxide, the decomposition additive, and the biocide.