First production-level bioremediation of explosives-contaminated soil in the United States.

Umatilla Army Depot Activity (UMDA) near Hermiston, Oregon was the location of the first production-level bioremediation of explosives-contaminated soil in the U.S. Soil from munitions washout lagoons contained high concentrations of TNT (2,4,6-Trinitrotoluene) and RDX (Hexahydro-1,3,5-trinitro-1,3,5- triazine) as well as HMX (Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). In addition to these primary contaminants, laboratory tests were performed for Tetryl (Methyl-2,4,6-trinitrophenylnitramine), 4-Am-DNT (4-Amino-2,6-dinitrotoluene), 2-Am-DNT (2-Amino-4,6-dinitrotoluene), 2,4 DNT (2,4-Dinitrotoluene), 2,6 DNT (2,6-Dinitrotoluene), 1,3,5-TNB (1,3,5-Trinitrobenzene), 1,3,-DNB (1,3-Dinitrobenzene) and NB (Nitrobenzene) during the pilot-scale treatability tests. The clean-up goal established by the Record of Decision (ROD) was 30 mg/kg each for TNT and RDX. Degradation progress was monitored using immunoassay field screening Methods SW 846,4050 and 4051. Confirmational analysis consisted of EPA Method 8330. Treatment time on a 2,700 cubic yard batch (810 cubic yards of soil) was 10-12 days. A composting technique developed by the Army Environmental Center and implemented by Bioremediation Service, Inc., Portland, Oregon was used at the site. Agricultural waste products (or amendments including cow manure, chicken manure, potato waste, sawdust and alfalfa) were blended with the contaminated soil during treatment. Specialized soil turning equipment mixed the compost for optimum biological action and homogeneity. Homogeneity of the compost mix ensured rapid degradation of all contaminants. Physical and chemical properties were closely monitored to ensure that thermophilic bacteria played a dominant role in the degradation process. Nearly 5,000 cubic yards of soil have been successfully treated, and more than 70% of all analyses indicate non-detectable levels of both TNT and RDX. The U.S. Army Corps of Engineers estimates that over $2.6 million is being saved using bioremediation at Umatilla.