NOVELTY - Oxidizing a substance (e.g. in a waste stream, drinking water, a paper pulp slurry or on a substrate surface) involves contacting the substance with peroxynitrite ion/peroxynitrous acid and at least one additional oxidizing agent.    USE - For oxidizing a substance; useful for purifying a waste stream by removing contaminants (e.g. chromium) from the waste stream, in oxidized form (e.g. hexavalent chromium); useful for purifying, disinfecting and sterilizing drinking water by oxidizing contaminants present in the drinking water; useful for oxidizing and etching a surface of substrate such as semiconductor chip; useful for bleaching paper pulp by oxidizing contaminant species in paper pulp slurry to reduce color of paper pulp (claimed); particularly useful for solubilizing and removing chromium from water-insoluble components of high level radioactive waste streams at e.g. Hanford site; useful for destroying wide variety of recalcitrant and toxic organic pollutants (e.g. trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and cyclotetramethylene-tetranitramine (HMX), chlorinated hydrocarbons, trichloroethylene (TCE), tetrachlorethylene (PCE), vinyl chloride, toluene, benzene, xylene and phenol, polychlorinated biphenyl (PCB) and dioxane) by oxidation; useful for bleaching waste paper and kraft pulp; useful in air purification by e.g. decontamination of avian flu virus; useful in sterilization of medical equipment, food and beverage preparation/storage equipment; useful in decontamination by destroying biological warfare agents; useful in medical treatments e.g. in oncology for destruction of tumors, in dermatology for removal of skin lesions and blemishes, in wound sterilization, in antiseptic treatments and in cosmetic treatments such as hair bleaching and dental bleaching; useful in agricultural applications such as defoliation, pesticide destruction, washing of fruits and vegetables for disinfection and pesticide removal; useful in surface treatments such as etching of semiconductors, stripping/etching of surfaces coated with paints or polymers, etching of metals for artistic production, catalyst regeneration, metal polishing, decontamination of objects exposed to radioactive components and leather tanning pretreatment; useful in separations such as mining, chromate processing, nuclear waste treatment; useful in energy production such as hydrogen production; useful in in-situ groundwater treatment via e.g. organic chemical destruction; useful in industrial and municipal wastewater treatment via organic chemical destruction and deflocculation; useful in air purification and off-gas treatment by e.g. oxidizing volatile organic compounds and oxidation of inorganics; useful in bleaching of textiles, paper pulp, laundry; useful in chemical synthesis including epoxidation, dehydrogenation of alkanes, polymerization and oxidation; useful in direct treatment of foodstuffs and beverages, and in pretreatment of materials useful in fuel cells.    ADVANTAGE - The method utilizes peroxynitrite ion/peroxynitrous acid in combination with additional oxidizing agent(s) for oxidizing the substance, reducing the amount of manganese added in the form of permanganate, thus reducing the quantity of high-level waste (HLW) glass produced. The combination of the oxidants reduces the mass of manganese left in solids portion of the waste stream. Hence, it is not necessary to remove the nitrate and nitrite salts in actual radioactive wastes, before using permanganate for oxidizing trivalent chromium in radioactive wastes. The addition of the mixed-oxidant peroxynitrite-permanganate does not require any design changes beyond that already established for permanganate; and the mixed-oxidant can be introduced into system at same location and in same manner as previously intended for the introduction of permanganate. The use of the mixed-oxidant peroxynitrite-permanganate reduces the mass otherwise added to the HLW Vitrification stream by permanganate alone; and reduces plutonium dissolution compared to permanganate employed as a single oxidant. Peroxynitrite has no impact on the mass of solids received at the HLW melter unlike permanganate which adds manganous hydroxide. Hence, the mixed-oxidant such as peroxynitrite-permanganate, requires less hydroxide than permanganate. As nitrate is already present in typical Hanford waste, peroxynitrite is compatible with the waste stream. Peroxynitrite bypasses the melter stream, to be released from the off-gas system of the treatment process, and thus does not add to the mass of glass produced in vitrification process. The application of mixed oxidants (e.g. peroxynitrite-permanganate) reduces the overall costs and risks of operations, by shortening the time of waste process operations.    DETAILED DESCRIPTION - Oxidizing a substance (e.g. in a waste stream, drinking water, a paper pulp slurry or on a substrate surface) involves contacting the substance with peroxynitrite ion/peroxynitrous acid and at least one additional oxidizing agent. The peroxynitrite ion/peroxynitrous acid is preferably generated by irradiating nitrate ion/nitric acid with electromagnetic radiation having energy to generate a peroxynitrite species. The electromagnetic radiation is selected from ultraviolet radiation, gamma radiation or other form of ionizing radiation, where the gamma radiation emanates from a radioactive component present in the substance. At least a portion of the peroxynitrite ion/peroxynitrous acid is generated from nitrate ion/nitric acid, preferably ex situ of the substance or in situ in the substance. The oxidation of the substance is enhanced, by direct application of the electromagnetic radiation to the substance, or by addition of a catalyst.