Microbiol. Bioremediation of explosive contaminated soil ” It has been estimated that there are thousands of explosives-contaminated sites within the United States, and even a greater number in Europe and the Soviet Union.” (2) TNT (2, 4, 6- trinitrotoluene) is one of the most popular explosives used by military forces, and due to improper handling and disposal techniques TNT and its derivatives, have polluted environments to levels that threaten the health of humans, livestock, wildlife and, entire ecosystems. TNT is known to have many health effects on animals as well as humans. As stated by The Agency for Toxic Substances and Disease Registry, “Workers involved in the production of high explosives experienced many harmful health effects as a result of exposure to 2, 4, 6-trinitrotoluene at their jobs.
These effects included disorders of the blood, such as anemia, and abnormal liver function.” (1) Treatment of the contaminated soil has usually been handled through incineration, which is costly and does not always guarantee that the pollutants have been completely destroyed. Therefore new techniques such as bioremediation have been developed as a safe cost effective alternative to treating pollutants such as TNT. (3) Fundamentals of Bioremediation Bioremediation is a new, efficient, environmentally friendly, and low-cost technology, which uses microorganisms to clean up soil contaminated with heavy metals and organic contaminants such as solvents, crude oil, explosives, and other toxic compounds from contaminated environments. Mechanism: Bioremediation works by taking complex organic compounds such as TNT, which are made up of carbon, nitrogen, oxygen, and hydrogen.
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When combined with regular compost ingredients such as manures, sawdust, straw, and fruit and vegetable processing wastes, the explosives become broken down into harmless chemical forms. (3) Bioremediation methods are classified into two categories: Composting, and. Composting: According to the EPA’s Fact Sheet on Composting of Soils Contaminated by Explosives, the process of composting operates as a result of naturally occurring microorganisms breaking down the explosive contaminants in the soil. Using the contaminants as “food,” the microorganisms convert them into harmless substances consisting primarily of water, carbon dioxide, and salts. In addition to this food source, microorganisms require nutrients, such as carbon, nitrogen, phosphorous, and potassium, in order to thrive, digest, and reproduce. To provide these nutrients in sufficient quantities, soil amendments, such as manure and potato waste, are added to the contaminated soil.
(3) The most common type of composting used for bioremediation of TNT contaminated soil is Windrow composting. The US Army Environmental Center report on Cleanup Technology: Bioremediation of Explosives-Contaminated Soil, describes windrow composting as the following. “Windrow composting mixes the soil with compost in long piles known as windrows. To facilitate the microbial growth, amendments such as wood chips, manure, straw, alfalfa, and other agricultural products are added. Windrows are used to facilitate aeration of the compost and are turned periodically using a compost turner.
Moisture content, windrow oxygen level, and temperature are easily monitored. During a field demonstration conducted by USAEC at UMD A, TNT reductions were as high as 99. 7% at 30% soil in 40 days of operation, with the majority of removal occurring in the first 20 days of operation.” (4) Windrow composting is an attractive bioremediation technique due to its relatively low processing costs, and high effectiveness at treating explosive contaminated soil. (4) BioslurryThe EPA Fact Sheet describes the application techniques of bio slurry as “sites requiring greater process control, more complete degradation, or where the cost of importing compost amendments is prohibitive, soil slurry bio treatment or ‘bio slurry’ is a bioremediation option.
... optimum conditions Vermicomposting is much faster than most conventional composting processes. * The percentages of Nitrogen, Potassium, ... nutrient leaching as occurs with conventional thermophilic composting and some less efficient methods of Vermicomposting ... soils; demonstrating the destruction of viable weed seeds through Vermicomposting and the destruction of humane pathogens in contaminated ...
The contaminated materials are mixed into a slurry to allow contact between the microorganisms and the contaminants. Because conditions are optimized for the microorganisms, slurry processes are faster than many other biological processes. The treated slurry is suitable for direct land application, similar to finished compost.” (4) The application of bio slurry has many attractive qualities. It provides for a controlled environment, which is monitored for efficient decomposition of TNT, and since the slurry is contained in tanks it prevents the contaminated soil from leaking back into surrounding soils. Conclusion Bioremediation is a valuable tool in the treatment of contaminated soil. When compared to incineration, with was previously the most common method of breaking down organic matter, bioremediation is less expensive, and less environmentally hazardous.
Incinerating soil will produce ash that in turn will have to be handled as hazardous waste, thus bioremediation converts contaminated soil into a nutrient rich product that is safe for humans and the environment.
1. “Public Health Statement for 2, 4, 6-Trinitrotoluene” web “Overview of Environmental Issues Associated with Residues of Energetic Materials” web main. asp 3. Environmental Protection Agency. 1997.
Innovative Uses of Compost; Composting of Soils Contaminated by Explosives. EPA Fact Sheet. EPA 530/F-97/045. October 1997. web USAEC (US Army Environmental Center).
Cleanup Technology: Bioremediation of Explosives-Contaminated Soil.