- Program Areas
- Energy and Water
- Environmental Restoration
- Munitions Response
- Resource Conservation and Climate Change
- Weapons Systems and Platforms
Numerical Modeling of Post-Remediation Impacts of Anaerobic Bioremediation on Groundwater Quality
Anaerobic bioremediation has emerged as an effective technology for aquifers contaminated with chlorinated solvents, chromate, explosives, and other contaminants. Typically, a readily biodegradable, soluble, organic substrate (e.g., molasses, lactate, whey) is flushed through the treatment zone. The substrate ferments to hydrogen and acetate, which support pollutant biodegradation and transformation. Important advantages of this process include: (1) a wide variety of pollutants can be treated to very low levels; (2) energy inputs are low; (3) the primary inputs are renewable materials; (3) no wastes are produced requiring treatment or disposal; (4) worker exposure to contaminants is minimal; and (5) capital and operating costs are low. As a result, anaerobic bioremediation is now one of the most commonly employed technologies for chlorinated solvent remediation.
However, anaerobic bioremediation can result in near- and long-term impacts to groundwater quality. Adverse impacts may occur under certain conditions, including release of dissolved organic carbon, methane, hydrogen sulfide, and a variety of naturally occurring metals and metalloids (e.g., iron, manganese, and arsenic). Preliminary data suggests that many of these contaminants do naturally attenuate. However, the factors controlling the rate and extent of natural attenuation are still poorly understood.
The objective of this project is to develop an improved understanding of the near- and long-term impacts to groundwater quality after implementation of in situ anaerobic bioremediation processes. This will include development and application of a general modeling approach for describing the natural attenuation of important secondary water quality impacts associated with electron donor addition.
In this project, researchers will formulate a general modeling approach appropriate for simulating the natural attenuation of electron donors and associated secondary impacts for a wide range of sites. The model approach and validation will be based on data from three intensively studied field sites--Bemidji Crude Oil Spill, Cape Cod Wastewater Plume, and the Naval Air Warfare Center (NAWC) - West Trenton Chlorinated Solvent Spill. A database of secondary water quality impacts at anaerobic bioremediation sites will be assembled, the secondary plumes analyzed to determine a range of characteristics and natural attenuation mechanisms, and a set of representative case studies identified illustrating important aspects of secondary plume behavior. The validated modeling approach will be used to simulate a series of synthetic plumes corresponding to end-member cases important to assessment, and the simulation results will be used to assess the potential for significant secondary water quality impacts at anaerobic bioremediation sites, based on site characteristics and remediation system design. The results of the model simulations and field monitoring will be integrated to develop a protocol for evaluating the likely extent and duration of secondary impacts at typical sites. The protocol will address extent and duration of impacts, sampling needs, and modeling approaches.
This research will improve understanding of the near- and long-term impacts to groundwater quality after implementation of in situ anaerobic bioremediation approaches and enable practitioners to predict the extent of these impacts and adjust remediation strategies to minimize negative effects. A detailed protocol will be generated for use by project managers, consultants, and regulators in evaluating the duration, extent, and magnitude of secondary water quality impacts and to develop monitoring and management approaches to minimize these impacts. The protocol will document the microbiological and geochemical processes controlling production and attenuation of secondary water quality impacts, typical characteristics of secondary water quality impact plumes, useful approaches for characterizing and monitoring these sites, and data analysis and modeling approaches that can be used to evaluate the likely extent and duration of impacts. (Anticipated Project Completion - 2014)
Points of Contact
Dr. Robert Borden P.E.
North Carolina State University
SERDP and ESTCP
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