SITE INFORMATION AND CORRESPONDENCE_1985-1997

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M _ environmentally safe to use. The time-release technology is not based on a coating process which could introduce regulatory concerns regarding the introduction of such materials to aquifers. ORC releases oxygen when it is contacted with water, however, the material is stable at up to 3% moisture which facilitates storage (long shelf life) and handling. Moderate pH levels are maintained when ORC is used. The particle size of ORC is extremely small (-325 mesh or about 44 microns and below) which facilitates oxygen dispersion. Although it is designed to be removed upon depletion, if left in place, ORC would ultimately be converted to ordinary magnesium hydroxide (Milk of Magnesia) which is also insoluble. As a result of these features, ORC can provide a passive, low cost, long term remediation in many circumstances. In groundwater, the hydraulics of a contaminated plume will not be disturbed and pollutants will not be volatized. Also, the rate control features of ORC make it a "redox control' agent which can be important where specific microbial systems yield the desired bioremediation activity in a restricted range of redox potentials. Technology When ORC comes in contact with moisture, oxygen is slowly released. The reaction proceeds according to the following equation: M902 + H2O > '/202 t + Mg(OH)2 In groundwater application, the ORC powder is contained in a matrix, such as cement briquettes or sand, and then lowered into the groundwater in an inert container. When the oxygen has been dissipated, this container and spent ORC is removed from the groundwater. The by-products of the reaction are oxygen and magnesium hydroxide. The oxygen is consumed and the insoluble magnesium hydroxide is removed. Magnesium peroxide has several uses outside of bioremediation. In agriculture, magnesium peroxide is used to provide oxygen to treat anaerobic soils that limit plant growth. Fifty states have registered Oxygen Plus® Plant Food, a magnesium peroxide based product, for use. Magnesium peroxide is listed in the Merck Index as a digestive antiacid making it even safe to ingest. The manufacture of ORC uses hydrogen peroxide in an exothermic reaction that is essentially irreversible. Thus, magnesium peroxide does not degrade to hydrogen peroxide as is often assumed. Consequently, it does not have a significant ability to chemically oxidize compounds, or emit powerful free-radical mechanisms as is the case with hydrogen peroxide and peroxide hydrates, such as sodium percarbonate. Applications = Figure 1 presents typical release patterns for two concentration of ORC in saturated sod. In general terms, the product can be described as releasing up to 10% of the available oxygen in about the first 200 hours followed by a release of each additional 10% every thousand hours. This translates into a longevity of about one year under static conditions.