Abstract: A process for eliminating and removing impurities including sulfur compounds and microorganisms as well as preventing further microbial contamination is accomplished by treating petroleum products or other hydrocarbon fluids with an aqueous solution of an oxidizing agent such as hydrogen peroxide or ozone together with a metallic ion catalyst, such as a mixture of ferric chloride and cupric chloride, where the metal ion is capable of forming activated oxygen complexes in the presence of such oxidizing agent, or by treatment with an aqueous solution of metallic ion catalyst and activated oxygen complexes formed from permanganate, peroxyborate or chromate ions.