(Ex Situ Biovault)
TECHNOLOGY DESCRIPTION:
The Ex Situ Biovault, developed by ENSR Consulting and Engineering (ENSR) and Larsen Engineers (Larsen), is a specially designed, aboveground soil pile designed to treat soils contaminated with volatile organic compounds (VOC) and semivolatile organic compounds (SVOC). The biovault is enclosed by a double liner system; the bottom half of the liner contains a leak detection system. The bottom half of the liner is supported by soil berms which serve as side walls.
To construct a biopile, a layer of gravel containing an air distribution system is placed on the bottom liner. The soil to be treated is then placed over the gravel. After placing the soil, a layer of sand containing a second air distribution system is placed on top of the soil. Soaker hoses are also placed on top of the pile. Finally, the top liner is placed on the pile and sealed at all seams. The air distribution systems are designed to control gas flows throughout the pile while the soaker hoses add water and nutrients. A sump is located in the lowest corner of the biovault with a pump that removes the liquids that drain through the soil pile. This liquid is amended with nutrients as needed and recirculated through the soaker hoses. Together, the sump and soaker hoses form the liquid management system (LMS).
One of the control parameters for biovault operation is the rate of air supply. For the SITE demonstration, two identical vaults were constructed. One vault was operated with a continuous supply of air throughout the course of treatment. In the other vault, air was supplied intermittently; as a result, this biovault operated under aerobic and anaerobic conditions.
WASTE APPLICABILITY:
The ex situ biovault is intended to treat soil contaminated with chlorinated and nonchlorinated VOCs, as well as SVOCs. Soil contaminated with VOCs was treated during the demonstration.
STATUS:
ENSR's and Larsen's ex situ biovault was accepted into the SITE Demonstration Program in June 1994. The pilot-scale, multivendor treatability demonstration (MVTD) was jointly sponsored by the New York State Department of Environmental Conservation (NYSDEC), the New York State Center for Hazardous Waste Management, and the SITE Program. The objectives of the MVTD were to (1) generate field data for biological processes, and (2) evaluate the performance of each biological process in meeting NYSDEC cleanup goals.
The demonstration was conducted from July to December 1994 at the Sweden 3-Chapman site in Sweden, New York and coincided with ongoing remediation at the site. The soil at the site was contaminated with elevated levels of acetone, trichloroethene, tetrachloroethene, cis-1,2-dichloroethene, 2-butanone, 4-methyl-2-pentanone, and toluene.
In addition to the ENSR and Larsen process, the following systems were also
demonstrated:
For information on these technologies, refer to the NYSDEC profiles in the Demonstration Program section (completed projects).
The Demonstration Bulletin (EPA/540/MR-95/524) is available from EPA. The Innovative Technology Evaluation Report, which provides more detailed demonstration results, will be available in 1997.
The primary objective of the SITE demonstration was to determine the
effectiveness of the biovaults in reducing the concentrations of six target
VOCs. The results of the ex situ biovault technology demonstration were as
follows:
The biovault process is sensitive to ambient temperatures, and cool temperatures during the operating period may have negatively impacted microbial activity. The developers suggest initiating biovault operation in the spring and discontinuing operation when weather conditions become too cold to sustain microbial activity.
EPA PROJECT MANAGER:
Carolyn Acheson
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7190
Fax: 513-569-7105
TECHNOLOGY DEVELOPER CONTACTS:
Nick Kolak
New York State Department of Environmental Conservation
50 Wolf Road, Room 268
Albany, NY 12233-7010
518-457-3372
Fax: 518-457-7743
David Ramsden
ENSR Consulting and Engineering
3000 Richmond Avenue
Houston, TX 77098
713-520-9900
Fax: 713-520-6802
N. Sathiyakumar
Larsen Engineers
700 West Metro Park
Rochester, NY 14623-2678
716-272-7310
Fax: 716-272-0159