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Dense Non-Aqueous Phase Liquids (DNAPLs) Training Courses
The Dense, Non-Aqueous Phase Liquids (DNAPLs) training courses provide guidance on characterizing, remediating, and monitoring DNAPL source zones.
The environmental problems associated with DNAPLs (dense, nonaqueous phase liquids) are well known: DNAPLs are extremely difficult to locate, small amounts contaminate large volumes, conventional groundwater extraction technologies do not work, and restoration of DNAPL sites to drinking water standards or maximum contaminant levels is considered unattainable. DNAPLs can be treated by implementing one of several or a combination of technologies. Despite the ever-increasing number of field applications of DNAPL removal technologies, many unanswered questions remain regarding the effectiveness of these technologies and how best to measure their performance with respect to site-specific remedial objectives.
This training addresses specific issues dealing with monitoring the performance of various DNAPL source zone remediation technologies. It is based on ITRC's Strategies for Monitoring the Performance of DNAPL Source Zone Remedies (DNAPLs-5, 2004). Performance is discussed in terms of effective and efficient progress toward the project goals. Elements of a robust performance monitoring program are described, including the need to establish appropriate performance goals and metrics well in advance. The applicability and limitations of various performance metrics, including the concept of mass flux, are discussed. Because of these limitations, a converging lines of evidence approach to performance assessment is stressed. While some issues pertaining to DNAPL fate and transport are covered in the document, participants are encouraged to review the material presented in the UK Environment Agency's Illustrated Handbook of DNAPL Fate and Transport in the Subsurface prior to taking the course.
Surfactant/cosolvent flushing involves the injection and subsequent extraction of chemicals to solubilize and/or mobilize dense, nonaqueous phase liquids (DNAPLs). The chemical flood and the solubilized or mobilized DNAPL are removed through extraction wells, and the liquids are either disposed or treated on site. This is a mature technology in the petroleum-engineering field, supported by decades of research and field tests.
Environmental applications have become more common in recent years. The technology has been shown effective for several DNAPL types, including spent degreasing solvents (TCE and TCA), dry cleaning solvents (PCE), heavy fuel oils, and coal tar/creosote. Lab work has demonstrated applicability to PCB-containing mineral oils. The primary appeal of the technology is its potential to quickly remove a large fraction of the total DNAPL mass. Technical challenges include locating and delineating the DNAPL source zone, estimating the initial DNAPL mass and spatial distribution, characterizing the hydraulic properties of the aquifer, delivering and distributing the injected chemicals to the targeted zone, and designing the optimum chemical formulation for a given DNAPL composition and soil type. Typical concerns include the cost of disposal of the effluent, regulatory permitting for underground injection of tracers or flushing agents, the overall impact of unremoved DNAPL, and the expertise of the personnel involved in site remediation.
This training familiarizes participants with ITRC's Technical and Regulatory Guidance for Surfactant/Cosolvent Flushing of DNAPL Source Zones (DNAPLs-3, 2003), which provides technical and regulatory information to help people understand, evaluate and make informed decisions regarding potential surfactant/cosolvent flushing projects. Included are a description of the technology, system operation, performance assessment, regulatory considerations, stakeholder concerns, case studies, and technical references.