Bioremediation of explosives in contaminated soil
Bioremediation of explosives in contaminated soilBioremediation of Explosives in Contaminated Soil
Abstract
TNT is not the kind of substance that most people think of composting, but it can be done! At several U.S. Army depots, the water used in processing explosives was disposed of through evaporation from unlined lagoons. This has resulted in sediments and soils that are contaminated with TNT (2,4,6- trinitrotoluene) and its derivatives RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) and HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine). One way of cleaning up these sediments is by incinerating them. A less expensive and more environmentally friendly method is "bioremediation," or use of natural biological and chemical processes to degrade the contaminants. That's where composting comes in. TNT, RDX, and HMX are complex organic compounds made up of carbon, nitrogen, oxygen, and hydrogen. When combined with more conventional compost ingredients such as manures, sawdust, straw, and fruit and vegetable processing wastes, the explosives become broken down into harmless chemical forms. The Army is using composting to clean up munitions processing wastes at several of its ammunition plants, including ones in Louisiana, Wisconsin, and Oregon. At the Oregon site, composting is projected to save 2.6 million dollars compared with incinerating the contaminated soils. In addition to saving money, composting will also avoid the need for burning fossil fuels and will produce an end product usable for backfilling, landscaping, or erosion control.
Introduction
Whether people know it or not explosives, such as tnt, are a very important part of their lives. Since World War I, munitions have been manufactured in the United States using a variety of energetic materials, including propellants, explosives, and pyrotechnic (PEP) materials. (Noyes, 1996) Many manufacturing sites contain explosives. As a result they have contaminated soil because of prior and existing operations. These contaminated soils are can be very toxic and mutagenic. It is estimated that the U.S. Army has 40 sites requiring cleanup of explosives-contaminated soils.(Noyes, 1996) Currently, regulatory agencies only approve incineration and composting as decontamination technologies. Incineration was commonly accepted by the public in the late 1980's, but the acceptance of this is now declining. Composting costs can also be high due to the necessary things needed for the composting process. For these reasons the Army has invested in developing and demonstrating other biotreatment technologies. The Army has been searching for alternatives to treat soil and groundwater contaminated with explosives. Contamination of soils has occurred at Army installations where explosives were produced and handled according to practices that were considered standard at the time. These installations require cost-effective techniques to treat large volumes of explosives-contaminated soils. The U.S. Army Environmental Center is using bioremediation - boosting the activity of naturally occurring microorganisms - to eliminate explosive compounds from the soil.(Noyes, 1996) A number of processes are being demonstrated to validate different bioremediation technologies and obtain critical performance information transfer applications to other Army installations. Bioremediation uses nature�s processes with simple technology, costs less...
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