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i . kn KL E I N F E L D E R <br /> For Oxygen Delivery <br /> In addition to physical stripping, air sparging also introduces oxygen to the groundwater. <br /> Sometimes referred to as biosparging, air sparging raises the oxygen concentration of the <br /> groundwater facilitating aerobic degradation of contamination to inert products. Biosparging is a <br /> j common approach for low levels of dissolved petroleum hydrocarbons, and can be implemented <br /> at low flows without the use of soil vapor extraction. The equation below represents the <br /> degradation of a simple, typical gasoline-range hydrocarbon(C6H8): <br /> C6H8+ 802+ bacteria 6CO2 + 4H2O <br /> Equating molecular weights in the equation, it takes approximately 3.2 pounds of oxygen to <br /> degrade a pound of gasoline. <br /> 3.1.3 THEORY OF OZONE SPARGING <br /> Ozone sparging is similar to the oxygen delivery strategy in air sparging, except that the objective <br /> is to deliver ozone to the dissolved contamination. Ozone (03) is a relatively powerful molecule <br /> with an oxidation potential of 2.07 volts capable of oxidizing petroleum hydrocarbons and <br /> chlorinated solvents to inert products. Ozone is an unstable molecule, with a half-life of about 2 <br /> minutes in air and 20 minutes dissolved in water. This makes the molecule reasonably safe for <br /> remediation because is degrades rapidly, but requires engineers to take care to expedite <br /> subsurface delivery to ensure effectiveness. The solubility of ozone at 20 degrees Celsius is 600 <br /> mg/l, which is approximately 13 times the solubility of oxygen making it an efficient compound <br /> to deliver and diffuse in the groundwater. <br /> The equation below represents the oxidation of DCA(C2C12H4) to carbon dioxide with ozone: <br /> C202H4+ 203 10 2CO2 + 2H2O + 2C" <br /> Equating molecular weights in the equation, 1 pound of 03 can oxidize approximately 1.0 pound <br /> ! of DCA. <br /> ! When ozone is used in sparging, the contact with the groundwater will also produce some <br /> hydroxyl radicals, which at 2.8 volts has even more oxidation potential than ozone. The hydroxyl <br /> radical OH• is formed from ozone in water as follows: <br /> 03 + 3H2O 60H* <br /> 12280/2002R476 Page 8 of 26 <br /> Copyright 2002 Kleinfelder,Inc. May 17,2002 <br />