Objective:

The objective of this project is to demonstrate and validate the use of shear-thinning delivery fluid for enhanced delivery of bioremediation amendments at a Department of Defense (DoD) site where chlorinated solvents are present. Specific objectives include: (1) demonstrate that amendments can be delivered into the lower permeability zones of a heterogeneous site using shear-thinning fluid enhanced delivery; (2) quantify the increase in treatment efficiency in terms of the rate and extent of bioremediation for the targeted treatment zone, particularly for the lower permeability zones, and the duration over which the fluid helps maintain suitable dechlorination conditions through diversion of competing electron acceptors and biodegradation of the shear-thinning agent; and (3) determine the cost factors for applying the technology and compare these costs to baseline bioremediation practices.

Technology Description:

In this project, a shear-thinning fluid will be used as an enhanced amendment delivery approach for in-situ bioremediation. A shear-thinning fluid can create a more stable displacement front than is created by injecting water solutions (i.e., standard amendment injection). The result is that the injected fluid will have a greater ability to penetrate lower permeability zones and to deliver amendments directly to these hard-to-treat areas. Matrix diffusion in low-permeability zones has a profound impact on remediation processes, as all flushing-based technologies—including bioremediation—deliver most of their amendments to the transmissive compartments and leave the low-permeability compartments relatively untreated. The field demonstration will include a test cell within a chlorinated solvent source zone where a shear-thinning fluid containing substrate and polymer will be injected. Performance will be monitored using a combination of soil and groundwater samples to determine mass reduction and treatment efficiency in both the transmissive and low-permeability zones, with baseline data provided by a parallel test cell where substrate will be injected without polymer. The experimental design will generate cost and performance data that is directly comparable to standard bioremediation applications.

Expected Benefits:

It is anticipated that this approach will significantly increase the efficiency of source zone bioremediation in heterogeneous settings. Cleanup of chlorinated solvent source zones has proven to be difficult and expensive at DoD sites, in part because drinking water standards are often 2 to 5 orders of magnitude below pretreatment concentrations at sites. A recent project funded by SERDP (ER-1292) evaluated the actual performance of in-situ source zone treatment technologies and showed that the median reduction in source zone concentration was only about one order of magnitude (e.g., 90%). Therefore, improving the performance of source treatment technologies is required to meet the most stringent cleanup objectives. The use of shear-thinning fluids aims to efficiently deliver bioremediation amendments directly to low-permeability zones for which treatment is typically limited when standard amendment delivery processes are utilized. As a result, the technology targets these zones, which serve as long-term contributors to low-level groundwater impacts via back diffusion. In addition, the enhanced amendment delivery can reduce overall treatment cost by decreasing treatment time and promoting efficient bioremediation through the exclusion of competing electron acceptors while potentially serving as a long-term carbon source. (Anticipated Project Completion - 2012) 

Principal Investigator:

Dr. Charles Newell
GSI Environmental, Inc.
2211 Norfolk Street, Suite 1000
Houston, TX 77098
Telephone: (713) 522-6300
Fax: (713) 522-8010
E-mail: cjnewell@gsi-net.com

DoD Liaison:

Ms. Erica Becvar
HQ AFCEE/TDE
Technology Transfer
3300 Sidney Brooks
Brooks City Base, TX 78235-5112
Telephone: (210) 536-4314
Fax: (210) 536-5989
E-mail: erica.becvar@brooks.af.mil