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ORC TECHNICAL BULLETIN # V.2 Oxygen Release Compound,ORC® Uses in the Remediation of Chlorinated Hydrocarbons Chlorinated hydrocarbons, such as PCE and TCE, are among the most recalcitrant environmental contaminants. Degradation mechanisms for these compounds is complex. While there is some evidence of aerobic breakdown, in most situations the predominant metabolic pathways are anaerobic. Also, there are dual-phase requirements for complete remediation to dechlorinated endpoints - such that the process is initiated under anaerobic conditions and completed in the presence of oxygen. ORC can be used at the various oxygen-dependent stages. In some cases, oxygen is needed to specifically inhibit certain reactions - such as the formation of vinyl chloride - a degradation product that is far more dangerous than its source compounds. The issue arises when sites are capped with clay and the resultant anaerobic conditions can promote the generation of vinyl chloride. ORC as a preventative treatment may be appropriate at certain sites. One of the most promising applications for ORC is in the support of various co-metabolic processes In co-metabolism, certain enzymes produced and extruded by microorganisms, degrade chlorinated hydrocarbons. Unfortunately, some of the chlorinated hydrocarbon degradation products, such as " -oxides, are toxic to the microorganisms and they must be constantly be "stoked" with substrates to .intain populations that allow the process to continue. - Recent advances in microbial selection and strain development have opened up the possibilities for bioremediation via these more rapid and efficient co-metabolic processes. Among these are the development of microorganisms that elicit the degratory enzymes more easily and in greater quantity. Also, more importantly, there is promise that epoxide resistant forms may be able to thrive rather than succumb in the presence of these toxic by-products. Co-metabolism may be the reason reductions in PCE and TCE were observed with ORC in laboratory experiments carried out by Retec. The objective of the experiment was to see if ORC could inhibit vinyl chloride formation. In the course of this study the levels of TCE and PCE introduced into the culture environment were both reduced by two thirds in two months - relative to the control. Furthermore, the authors of the study did not rule out direct chemical oxidation as a full or partial mechanism for the observed results. LREG EN ES IS --------------------------------------------------------------------------------------- Bioremediation Products 27130A Paseo Espada, Ste 1407, San Juan Capistrano, CA 92675 Phone: 714-443-3136 Fax: 714-443-3140