Groundwater in certain areas at Aberdeen Proving Ground is contaminated with a mixture of chlorinated solvents including 1,1,2,2-tetrachloroethane, trichloroethene, tetrachloroethene, carbon tetrachloride, and chloroform. In these areas, groundwater discharges through natural wetlands to surface water. The U.S. Geological Survey (USGS) documented that in most of these areas, solvents in groundwater are slowly seeping through the wetlands and biodegrading prior to reaching the surface. However, in certain localized areas, groundwater seeps rapidly to the surface without adequate biodegradation or attenuation. The U.S. Army selected Geosyntec to work with the USGS to develop a bioaugmentation culture and delivery method to treat high velocity seep areas to prevent the discharge of chlorinated solvents to surface water. The goal of the project was to install the treatment technology in a contaminated seep area, monitor technology performance for one year, and document the technology's ability to biodegrade solvents before they discharged to surface water.
Geosyntec's Scope of Services
Geosyntec and USGS worked collaboratively to devise a passive treatment technology that could be installed over the seep areas with minimal disruption to the wetland and with essentially no maintenance requirements. The concept involved the installation of a relatively thin organic mat that could be bioaugmented with a microbial consortium known as WBC-2 capable of biodegrading all the solvents detected in groundwater. Geosyntec and USGS successfully produced several technical innovations, not the least of which was the development of WBC-2 to dechlorinate a variety of chlorinated ethanes, ethenes, and methanes. We also performed engineering design and testing of the bioreactive mat matrix to demonstrate the compatibility of the mat design with WBC-2, and invented and used a solid-state dissolved hydrogen gas detector to monitor hydrogen production in the bioaugmented reactive mat.
Due to our success at this site, Geosyntec was then selected to work in collaboration with USGS to assist them with the groundwater remedy, as part of a Performance Based Contract (PBC) with the Army, to perform a design data gap investigation, designing and installing the bioreactive mat technology and WBC-2 at additional seep areas throughout the study area.
Geosyntec and USGS staff have now installed and bioaugmented this first-of-its-kind mat at multiple locations. One year of monitoring demonstrated that the initial reactive mat achieved contamination concentration reductions in excess of 99% with complete degradation of solvents to ethene, ethane, and methane. WBC-2 was shown to persist in the mat and retain its activity, demonstrating its value as a bioaugmentation culture. Other than removing weeds, the reactive mat required no maintenance and was geotechnically stable in a tidal wetland. The mat continued to remediate groundwater beyond the first year of monitoring with no ongoing maintenance.
The success of the technologies resulted in a Cooperative Research and Development Agreement (CRADA) between USGS and Geosyntec to continue the commercialization of WBC-2 and the reactive mat. One of our employees, then a USGS collaborator, was selected as a finalist for the prestigious Call to Service Award from the Partnership for Public Service for her work on these technologies.