There are an estimated 1 to 2 million underground storage tanks containing gasoline in the United States. Of this number it is estimated that 100,000 to 400,000 are leaking either into the soil or directly into the groundwater. In addition to leaking underground storage tanks, leakage from the subterranean portion of tanks at fuel storage facilities, such as the tank shown below, are contributing to the volume of petroleum hydrocarbons contaminating the subsurface environment.
The United States Environmental Protection Agency (EPA) estimates that roughly 11 million gallons of gasoline per year are lost due to leaking underground storage tanks. Gasoline as well as other fuels contain BTEX which are hazardous compounds regulated by the EPA. These BTEX compounds may comprise greater than 60% of the mass that goes into solution when gasoline is introduced to water.Due to their relatively high solubility, BTEX compounds are the hydrocarbons most frequently reported as groundwater contaminants. Considering that gasoline leaks from underground storage tanks are a major source of groundwater contamination and that almost 50% of the drinking water supply in the United States comes from groundwater wells, there is high potential for drinking water contamination resulting from leaking underground storage tanks.
The United States Environmental Protection Agency (EPA) estimates that roughly 11 million gallons of gasoline per year are lost due to leaking underground storage tanks. Gasoline as well as other fuels contain BTEX which are hazardous compounds regulated by the EPA. These BTEX compounds may comprise greater than 60% of the mass that goes into solution when gasoline is introduced to water.Due to their relatively high solubility, BTEX compounds are the hydrocarbons most frequently reported as groundwater contaminants. Considering that gasoline leaks from underground storage tanks are a major source of groundwater contamination and that almost 50% of the drinking water supply in the United States comes from groundwater wells, there is high potential for drinking water contamination resulting from leaking underground storage tanks.
Once groundwater contamination has occurred, there are numerous techniques available to either contain the pollutant or treat the aquifer. These techniques can range from ex-situ technologies such as excavation and subsequent treatment of aquifer material or pump and treat methods, to physical containment via slurry walls and other impermeable structures, to in situ (a.k.a. intrinsic) remediation via biological and/or chemical transformation of hazardous materials into either less toxic or non-toxic compounds. Of these various techniques, in situ biologically-based remediation has the potential to provide an efficient and cost effective remediation procedure while minimizing site disturbance.
1) Intrinsic bioremediation- The microorganisms which are used for biodegradation are tested for the natural capability to bring about biodegradation. So the inherent metabolic ability of the microorganisms to degrade certain pollutants is the intrinsic bioremediation. The ability of surface bacteria to degrade a given mixture of pollutants in ground water is dependent on the type and concentration of compounds, electron acceptor and the duration of bacteria exposed to contamination. Therefore, the ability of indigenous bacteria degrading contaminants can be determined I laboratory by using the techniques of plate count and microcosm studies. The conditions of site that favour intrinsic bioremediation are ground water flow throughout the year carbonate minerals to buffer acidity produced during biodegradation, supply of electron acceptors and nutrients for microbial growth and absence of toxic compounds.2) Engineered in situ bioremediation- When the bioremediation process is engineered to increase the metabolic degradation efficiency (of pollutants) it is called engineered in situ bioremediation. This is done by supplying sufficient amount of nutrients and oxygen supply, adding electron acceptors and maintaining optimal temperature and pH. This is done to overcome the slow and limited bioremediation capability of microorganisms.
Although there are ways or technique to treat the contamination, I believe it's still best to avoid it. Storage tanks containing gasolines or other harmful chemical should be treated well for they are threat to the environment and to human lives as well.
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