Abstract: A system for the treatment of oxidizable contaminants in wastewater includes a contaminant treatment vessel and a hydrogen peroxide supply unit. The hydrogen peroxide supply unit includes a hydrogen peroxide transfer line in fluid communication with the contaminant treatment vessel with an air-gap. A wastewater feed stream may also be in fluid communication with the contaminant treatment vessel. A contaminant treatment vessel effluent stream may also be in fluid communication with the contaminant treatment vessel. A method for the treatment of oxidizable contaminants in wastewater includes supplying wastewater to a contaminant treatment vessel, supplying hydrogen peroxide to the contaminant treatment vessel so that the supply is above the maximum filling level of the vessel in an air-gap, and contacting wastewater in the contaminant treatment vessel with hydrogen peroxide.