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. 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 bioslurries.
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.
... Contaminated material will still be filled with cement and then contained in the area they are in, none of the material will be incinerated. Then the entire area will be caped off and landscaped for future use The first phase of this was completed in late 2009 while the second stage began in Spring of 2010. (Tar ponds timeline, 2007) (Sydney Tar Ponds, 2012)
In 1998, the company conducted a voluntary partial cleanup of contaminated soils under The Massachusetts Department of Environmental Protection. The process involved excavation and transportation to an off site of about 8,000 cubic yards of the depleted uranium and copper contaminated soil. The cleanup stopped at the end of 1998 when the company decided that the standards set could not be met without excavating a significant amount of material.
This last process is significant not only because it brought dioxin the current notoriety but it also is a chemical process used to make products that were used and are still been used in many applications. These applications include pesticide, herbicide, defoliating agent such as Agent Orange, cleaning agent and electrical insulation. Consequently, human exposure to dioxin is not a recent phenomenon and the dangers of dioxin are not unknown. Only in recent years, especially after the Vietnam War, has the media concentrated on the dangers and impact of dioxin.
The word “remediate” means to solve a problem, so the word “bioremediation” refers to the use of biological organisms to solve an environmental problem. Bacteria, fungi, protists and other microorganisms in a non-polluted environment are constantly breaking down organic matter, and when the soil is polluted, some of the organisms may die, but others will still be able to break down the pollutants. Bioremediation provides organisms that can consume the pollutants with fertilizer, oxygen, and other conditions to encourage the rapid growth of these organisms. They then would be able to break down the organic pollutants at a correspondingly faster rate. There are two general ways in which bioremediation functions. One way is where specific survival conditions of a microorganism living in the soil are enhanced to increase the rate of a pollutant’s degradation. The second way is when specialized microbes are added to degrade the contaminant. This way is less common. For many types of polluted soil, bioremediation provides an excellent method of clean-up, but in some cases the pollutant is toxic even for the microbes. These pollutants include metals such as cadmium or lead, and salts such as sodium chloride. Although it may not work in all cases, bioremediation is considerably easier than other methods because it enhances the functions that the microbes already carry out in the soil. Along with being easier, it can be much less expensive because the soil does not have to be pumped out of the ground for treatment (Environmental Inquiry-Bioremediation). Serratia Marcescens is a bacterium that is commonly used for bioremediation.
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...d trash on the soil in order to keep the soil fresh. My interest would be like find a material to transform those waste or trash as a <>. By that mean, Farmers, instead of buying chemical products to damage the soil, they would use that possibility to keep the soil safe and sound and save money too. Therefore, in order to improve air quality in my community, those disciplines would be highly required. It will also be very good for the safety of the environment.
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... in 1995 showed that native plants and micro-organisms grow naturally in hostile mine environments and how they can be propagated to potentially rehabilitate TSFs and polluted soils. The programme focused on effectiveness of different types of vegetation in groundwater and soil remediation.