A method for the generation of a supply of ozone containing process gas exhibiting high effective ozone content basically involves the steps of (a) providing a stream of an oxygen containing feed gas having a temperature not greater than about 50.degree. C. and an absolute pressure between about 1 and 3 bar, (b) subjecting the stream of feed gas to an electric discharge that transforms some of its oxygen content into ozone to produce a stream of ozone containing gas, and (c) compressing the ozone containing gas with simultaneous cooling thereof to produce a stream of ozone containing process gas having a temperature not greater than about the temperature of the feed gas, an absolute pressure greater than 3 bar and an absolute ozone partial pressure of at least 0.2 bar. Various systems for carrying out such methods are disclosed.