A method for removing contaminants from the combustion gases generated by the incineration of waste. Air is injected into an incineration device along with a fuel and is supplemented by a oxygen feed. The resulting combustion waste gas stream contains contaminants such as nitrogen oxides and is quenched, then fed to a reaction zone where it will contact ozone for a predetermined period of time. The thus treated combustion waste gas stream can be fed to a scrubber assembly where the reaction products formed by the reaction of ozone and the contaminants are removed.