The patented Simplot Anaerobic Biological Remediation (SABRE™) process reduces contamination through on-site bioremediation of soils contaminated with the herbicide dinoseb (2- sec- butyl- 4,6-dinitrophenol) or nitroaromatic explosives. The biodegradation process begins when contaminated soil is placed in a bioreactor and flooded with buffered water. A source of carbon and a nitroaromatic-degrading consortium of anaerobic bacteria are then added to the bioreactor. Anaerobic conditions are quickly established, allowing the bacteria to degrade the target compounds while preventing polymerization of intermediate breakdown products. A photograph of the technology in operation is shown below.
Soil can be treated in above- or in-ground containment ponds. Temperature, pH, and redox potential in the bioreactor are monitored during treatment. A hydromixing system has been engineered to efficiently solubilize the target compound from the soil while maintaining anaerobic conditions. Frequency of mixing depends upon the contaminants present, concentration, soil heterogeneity, and soil type.
This technology is designed to treat soils contaminated with nitroaromatic pesticides and explosives. This contamination most often occurs at rural crop dusting aircraft sites and at ordnance handling and manufacturing facilities.
This technology was accepted into the SITE Emerging Technology Program in January 1990. Based on bench- and pilot-scale results from the Emerging Technology Program, this technology was accepted in the SITE Demonstration Program in winter 1992. Demonstrations for dinoseb and the explosive TNT (2,4,6-trinitrotoluene) were performed at Bowers Field in Ellensberg, Washington and at Weldon Spring Ordnance Works in Weldon Spring, Missouri, respectively. A Technology Capsule describing the dinoseb project (EPA/540/R-94/508a) and an Innovative Technology Evaluation Report describing the TNT project (EPA/540/R-95/529) are available from EPA.
Since then, the process has been evaluated at several other sites. During the winters of 1994 and 1995, two 10-cubic-yard (yd³) batches of soils from Bangor Naval Submarine Base, Washington were treated using the SABRE™ Process. One batch contained TNT, while the other was contaminated with TNT and RDX. Cost savings were realized by using in-ground ponds for bioreactors and efficient mixing. Heaters were also installed to maintain optimum biological activity during the sub- freezing temperatures. Treatment goals were met or surpassed in the 90 days allowed for the project.
A full-scale remediation of 321 yd³ of dinoseb-contaminated soils was completed in October 1995. The site was a former herbicide distributor located near Reedley, California. The treatment was performed in an aboveground containment already existing on site. Concentrations ranging from 40 to 100 milligrams per kilogram were reduced to nondetect after 28 days of treatment. The soil was mixed three times during treatment using a full-scale, expandable hydromixing system.
A larger evaluation was conducted in fall 1996 at Naval Weapons Station - Yorktown. About 500 yd³ of soil were contained in an in-ground pond measuring 86 feet by 150 feet deep. A full-scale hydromixing system was used to periodically slurry the soil and water mixture.
Process optimization work is ongoing. Collaborative projects with the U.S. Army Corps of Engineers Waterways Experiment Station and the U.S. Army Environmental Center are underway.
During the Weldon Spring demonstration, TNT was reduced from average concentrations of 1,500 parts per million (ppm) to an average of 8.7 ppm, for an average removal rate of 99.4 percent. Toxicity testing, which included early seedling growth, root elongation, and earthworm reproduction tests, showed that soil toxicity was significantly reduced. The Weldon Spring demonstration showed the effectiveness of this process even in unfavorable conditions. The treatment time was lengthened by unseasonably cool ambient temperatures. Temperatures in the bioreactor were as low as 4°C; ideal temperatures for the SABRE™ process are 35 to 37°C.
During the Ellensburg demonstration, dinoseb was reduced from 27.3 ppm to below the detection limit, a greater than 99.8 percent removal. Other pesticides were also degraded in this process, highlighting the effectiveness of the process even in the presence of co-contaminants. The process was completed in just 23 days, despite 18°C temperatures.
Bioreactors and Soil Mixing System at a TNT-Contaminated Site in Bangor, Washington
EPA PROJECT MANAGER:
Wendy Davis-Hoover
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7206
Fax: 513-569-7879
TECHNOLOGY DEVELOPER CONTACTS:
Russell Kaake or Tom Yergovich
J.R. Simplot Company
P.O. Box 912
Pocatello, ID 83201
208-235-5620 or 208-238-2850
Fax: 208-235-5699