In August 2001, the U.S. Army Corps of Engineers (USACE) initiated full-scale bioremediation of 6,000 yd3 of organic explosive-impacted soil at the Iowa Army Ammunition Plant (IAAP). Daramend® bioremediation was selected due to its low soil bulking, effectiveness in the presence of elevated heavy metal concentrations, and potential cost savings over alternative technologies. Following treatment over an 8-week period, RDX, HMX, and TNT concentrations were reduced by 98.9%, 92.4%, and 93.7%.
Production of conventional ammunition at the IAAP, located near Burlington in southeast Iowa, began in 1941. Past operations resulted in soil and groundwater contamination through the discharge of wastewater containing explosives and explosive byproducts, and through open burning and land disposal of production wastes. Soil at the site is characterized as clayey glacial till amenable to bioremediation. Currently, no technology is in place to address the site’s contaminated ground water.
Daramend bioremediation involves the generation of repeated and sequential anoxic and oxic conditions through the application of organic amendments and powdered iron at low doses (0.5-2% by weight). The amendments are formulated with the specific particle size distribution and nutrient profile needed to create optimal microbiological conditions in the soil. This technology can be applied in-situ to surface soils when contamination does not extend beyond the upper 2-3 ft. For deeper contamination zones, ex-situ applications are employed through a land treatment or aerated windrow process. Land treatment typically is less expensive than aerated windrows; however, windrows often require less space.