Answer:
Bioremediation relies on stimulating the growth of certain microbes that utilize contaminants like oil, solvents, and pesticides for sources of food and energy. These microbes convert contaminants into small amounts of water, as well as harmless gases like carbon dioxide.
Bioremediation requires a combination of the right temperature, nutrients, and foods. The absence of these elements may prolong the cleanup of contaminants. Conditions that are unfavorable for bioremediation may be improved by adding “amendments” to the environment, such as molasses, vegetable oil, or simple air. These amendments optimize conditions for microbes to flourish, thereby accelerating the completion of the bioremediation process.
Bioremediation can either be done "in situ", which is at the site of the contamination itself, or "ex situ," which is a location away from the site. Ex situ bioremediation may be necessary if the climate is too cold to sustain microbe activity, or if the soil is too dense for nutrients to distribute evenly. Ex situ bioremediation may require excavating and cleaning the soil above ground, which may add significant costs to the process.
The bioremediation process may take anywhere from several months to several years to complete, depending on variables such as the size of the contaminated area, the concentration of contaminants, temperature, soil density, and whether bioremediation will occur in situ or ex situ.
Advantages of Bioremediation
Bioremediation offers numerous advantages over other cleanup methods. By relying solely on natural processes, it minimizes damage to ecosystems. Bioremediation often takes place underground, where amendments and microbes can be pumped in order to clean up contaminants in groundwater and soil. Consequently, bioremediation does not disrupt nearby communities as much as other cleanup methodologies.
The bioremediation process creates relatively few harmful byproducts (mainly due to the fact that contaminants and pollutants are converted into water and harmless gases like carbon dioxide). Finally, bioremediation is cheaper than most cleanup methods because it does not require substantial equipment or labor. By the end of 2018, the United States Environmental Protection Agency (EPA) had brought bioremediation activities to a total of 1,507 sites.
Example of Bioremediation
In 1989, the Exxon Valdez oil tanker ran aground off the coast of Alaska; the tanker ended up spilling approximately 11 million gallons of oil. Around this same time, bioremediation was gaining traction as a viable option for oil cleanups. The EPA and Exxon Mobil Corporation (XOM) both began testing different compounds. Initial tests regarding the effectiveness of bioremediation looked promising.
Between 1989 and 1990, more than 100,000 pounds of fertilizer was applied over more than 2000 applications to the affected areas. By mid-1992, the cleanup was considered complete, and the fertilizer had degraded nearly all the oil compounds.
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