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Slow-Releasing Oxygen Source
Citation:
DAVIS-HOOVER, W. J. AND S. J. VESPER. Slow-Releasing Oxygen Source. Presented at The World's Best Technologies Conference, Dallas, TX, May 14 - 15, 2008.
Impact/Purpose:
To investigate the advanced bioremediation process for subsurface treatment of soil pollution.
Description:
Subsurface pollution is an environmental issue of great concern in the United States and around the world. Bioremediation has proven to be an effective and environmentally preferable treatment for biodegradable pollutants, such as methyl tertiary butyl ether, toluene, ethylbenzene, xylene and others. Performance of bioremediation, however, has been limited because it can be difficult to access the contamination in subsurface soil and because, in most cases, bioremediation requires oxygen, which is highly insoluble in water. Researchers at EPA have developed an advanced bioremediation process for subsurface treatment of soil pollution that solves these problems. Bioremediation relies on microorganisms to break down pollutants into nontoxic matter. To access the subsurface, hydraulic fracturing was adapted by EPA from the oil drilling industry. A hole is drilled into the contaminated area, and high pressure water cracks the subsurface layers. Microorganisms then are introduced into the fractures, where they begin to degrade the pollutants. Because microorganisms require oxygen, it is pumped either as air or oxygenated water into the cracks. In both cases, the oxygen is lost quickly from the bioremediation process. EPA developed encapsulated sodium percarbonate, called Slow-Releasing Oxygen Source (SOS), to provide a slow, constant and controlled release of oxygen for use by the microorganisms to degrade pollutants. The SOS can be delivered in the hydraulic fracturing water directly to the site of the contamination in the soil. Hydraulic fracturing combined with the SOS offers numerous advantages over standard bioremediation methods. Operational costs are minimized because equipment maintenance is not required (i.e., surface pumps or meters, which tend to freeze and fail, are not needed), the proces does not spread pollutants, and the slow release of oxygen provides a long-term treatment. Bioremediation is part of the multibillion dollar U.S. remediation industry and has application woldwide. With growing concern about hazardous chemical remediation methods, bioremediation likely will increase in importance as an environmentally preferable remediation alternative.