Groundwater Cleanup

Quickfinder

In Situ Treatment Techonologies Reduce Site Cleanup Costs (PDF) (2 pp, 129KB, About PDF)

Issue

Groundwater treatment employs many different technologies. Conventional ex situ (removed from source) treatment methods, such as pump and treat, can have substantial operation and maintenance costs and may not achieve cleanup objectives within reasonable time frames, if at all. As an alternative, in situ (at source) processes treat soils and groundwater in place (without removal) with physical/chemical or biological treatment technologies. This approach may be advantageous since the costs of materials handling and some environmental impacts, such as energy use and disruption of the surrounding area, may be reduced.

Scientific Objective

The U.S. Environmental Protection Agency's (EPA) Land Research Program in the Office of Research and Development (ORD) has made significant contributions to exploring innovative solutions to groundwater pollution problems and translating research results into practical applications. Scientists are evaluating the use of in situ treatment at hazardous waste sites and verifying innovative technologies. Research currently focuses on air sparging, thermal treatment, permeable reactive barriers, chemical treatment, bioremediation, phytoremediation, and monitored natural remediation. More information on in-situ treatment technology optimization. More information about site treatment and characterization . Technologies are tested by scientists in laboratories and with pilot-scale demonstration projects.

In situ processes can be used in combination with each other and with more conventional ex situ treatments to enhance their effectiveness. Removal rates and extent vary on the basis of contaminants and site-specific characteristics; contaminant distribution and concentration; co-contaminant concentrations; indigenous microbial populations and reaction kinetics; and soil parameters. Many of these factors are site dependent and can be difficult to manipulate. As a result, in situ treatment may not be uniform throughout the treatment area.

Application and Impact

ORD's evaluation of new technologies and collaboration with EPA's regional offices has reduced remedial costs and improved effectiveness. Research contributions include:

ORD scientists are continuing to investigate the fundamental and applied aspects of In Situ Chemical Oxidation (ISCO). ISCO introduces a chemical oxidant into the subsurface to transform groundwater or soil contaminants into less harmful chemical species. It is currently being used at new and old sites to reduce contaminant mass movement, off-site migration, mass input to pump-and-treat systems, and/or to reduce anticipated cleanup times. More information on in situ chemical oxidation
Scientists collaborate with EPA's regional offices to provide solutions to site-specific problems in states. One example is the Macalloy site in South Carolina. Ferrous sulfate was injected, in combination with sodium hydrosulfite, into a native aquifer formation in the path of a dissolved phase Cr(VI) plume. This pilot study illustrated that this solution provided sustained in situ treatment of dissolved phase Cr(VI) for a period of at least 1,020 days. More information on in situ treatment study (PDF) (1 pg, 16KB, About PDF).
Scientists provide quick-response technical assistance to EPA's regional offices on site-specific problems at Superfund, Resource Conservation and Recovery Act (RCRA), Brownfields, and ecosystem restoration sites. More information about ongoing research efforts can be found here

References

Ground Water Ecosystems Restoration Research Web site

Huling, S.G., & Pivetz, B. In-Situ Chemical Oxidation, Engineering Issue, EPA/600/R-06/072, Washington, DC, 2006.

Khan, F.A. & Puls, R.W. In Situ Abiotic Detoxification and Immobilization of Hexavalent Chromium in the Capillary Fringe Zone. Ground Water Monitoring and Remediation, 2003, 23(1), pp. 77-84.

Su, C., & Puls, R.W. In Situ Remediation of Arsenic in Simulated Groundwater Using Zerovalent Iron: Laboratory Column Tests on Combined Effects of Phosphate and Silicate. Environmental Science & Technology, 2003, 37(11), pp. 2582-2587.

U.S. Environmental Protection Agency. Envirogen Propane Biostimulation Technology for the In Situ Treatment of MTBE Contaminated Ground Water: Innovative Technology Evaluation Report (PDF) (18 pp, 322KB, About PDF) EPA/600/R-02/092, Washington, DC, 2002.

U.S. Environmental Protection Agency. In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites (PDF). (22 pp, 922KB, About PDF). Engineering Issue, EPA/625/R-06/015, Washington, DC, 2006.

Groundwater and ecosystem restoration research publications

Contacts

Robert Puls, Ph.D. (puls.robert@epa.gov), EPA's Office of Research and Development, U.S. Environmental Protection Agency, 580-436-8543

David Burden, Ph.D. (burden.david@epa.gov), EPA's Office of Research and Development, U.S. Environmental Protection Agency, 580-436-8606