Accelerated natural attenuation of MTBE with Oxygen Release Compound (ORC (2004)

Oxygen Release Compound (ORC) is patented formulation of phosphate-intercalated magnesium peroxide that releases oxygen slowly and facilitates the aerobic degradation of a range of environmental contaminants including petroleum hydrocarbons and fuel oxygenates. The history of ORC’s introduction and acceptance represents a model for the evolution of an innovative technology. This statement comes by virtue of the fact that since 1994 ORC has been used on over 8,000 sites worldwide and has been the subject of an extensive body of independent, peer reviewed literature. ORC technology has now been clearly established as a sensible strategy for enhancing natural attenuation on sites where capital and management intensive options are either undesirable or contraindicated. With regard to the range of compounds that can be addressed, the use of ORC began with the remediation of BTEX and TPH groundwater contamination and other successful applications have been made to treat an array of other aerobically degradable compounds such as MTBE. With respect to MTBE, as early as 1996, consultants using ORC noticed that MTBE concentrations decreased at a higher than expected rate. Working on this foundation, a number of subsequent laboratory and field experiments have demonstrated that oxygen can indeed enhance the remediation of MTBE; a concept that has since been verified in other quarters. An overview of 5 years of results will be presented along with a detailed examination of some special cases as featured herein. At a gasoline station near Beaufort, SC, MTBE was detected in the shallow water aquifer near a former UST area. ORC was applied to an anoxic part of the aquifer upgradient of the ditch in a barrier application. Prior to oxygen addition, the deeper wells located closer to the ORC application area contained the highest concentrations of MTBE and the lowest concentrations of dissolved oxygen (DO). The input of MTBE into the ORC treated zone was elevated and constant prior to oxygen addition. One year after ORC was added, MTBE concentrations decreased from 19,600 ppb to <500 ppb (non-detect) while DO increased from 0.4 ppm to 12 ppm, eventually stabilizing at 3.5 ppm. At a U.S. Coast Guard support facility in Elizabeth City, NC, MTBE was detected in groundwater. The release of petroleum constituents was related to the 10,000-gallon fiberglass underground storage tank (UST) and a series of underground transfer lines used to deliver JP-4 and JP-5 jet fuel to the aircrafts at the facility. ORC was applied via direct push technology into both the source area and dissolved plume area. Each ORC application was designed to satisfy oxygen requirements for MTBE and BTEX biodegradation and other naturally occurring oxygen sinks in the aquifer. Post treatment monitoring of the aquifer quality parameters indicated effective enhancement of biological activity and substantial decrease in dissolved MTBE and BTEX concentrations. Maximum MTBE concentrations of 510 ppb in the source area and 390 ppb in the plume area were recorded prior to treatment. The MTBE concentrations in both source and plume areas decreased to below quantifiable limits approximately 3 months after treatment. After seven months, the dissolved MTBE mass was reduced 100%, and subsequent monitoring events have shown no rebound in MTBE concentrations. Introduction As a ubiquitous fuel additive, methyl tert-butyl ether (MTBE), has complicated the remediation and closure of contaminated properties. Regulators, oil companies, and now the public are becoming increasingly concerned about the environmental impact of this and other related ether oxygenates. Several factors responsible for the heightened level of concern include the following: 1) MTBE degrades very slowly under aerobic conditions, 2) it has a very low taste and odor threshold, 3) its toxicity and carcinogenicity profile are largely undetermined and 4) it is highly soluble and does not readily retard on the aquifer matrix. This last feature has compromised