Natural attenuation of petroleum contaminants is the process by which naturally-occurring bacteria break down petroleum hydrocarbons. This biodegradation process typically occurs much more rapidly under aerobic conditions, making a lack of dissolved oxygen one of the most limiting factors of contaminant degradation.
Increasing dissolved oxygen in the zone of saturation can greatly increase the rate of contaminant degradation. Oxygen is often added to the subsurface through air sparging, or the injection of compressed air, into specially-designed wells. Air sparging is typically conducted as continuous prolonged treatment, but is also commonly used in multiple episodic treatment events.
Oxygen Releasing Compounds (ORCs) are specifically-designed to enhance aerobic conditions in saturated soil and the groundwater. They are available from different manufacturers. ERMI has successfully utilized ORCs to increase dissolved oxygen concentrations and enhance aerobic degradation for petroleum site remediation. ORCs are a bioremediation technique that has accelerated petroleum-hydrocarbon degradation and decreased site cleanup time in comparison to natural attenuation. ORCs can also be utilized as a component of a larger remediation strategy.
Application of ORCs can be advantageous enhancements while backfilling a contaminant-source excavation. ORCs are mixed with clean fill material within the saturated zone, providing a continued remedial effect on dissolved contaminant concentrations, generally for up to 12 months following removal of the contaminated soil. ORCs can also be injected using both temporary injection points or permanent injection wells. ORCs can be used to target a variety of contaminants, such as benzene, toluene, ethylbenzene, and total xylenes (collectively known as “BTEX”), and gasoline, diesel, and oil range organics.
ERMI has cost-effectively applied ORCs as a remediation technique on many projects, including open-pit application of both slow-release pelletized form and slurry form, as a stand-alone injection-based strategy, and as a targeted polishing treatment following long-term remediation efforts.
ORCs are one component of the remediation toolkit regularly used by ERMI to reduce cleanup time, minimize site disruption, and/or provide that final push toward achieving cleanup goals.