What is Bioremediation?

Bioremediation is the natural process of cleaning up harmful chemicals in the environment. This is done using microbes that live in the soil or groundwater that like to eat harmful chemicals found in gasoline from oil spills. When these microbes digest these chemicals they change them into water and harmless gases such as carbondioxide.

How does it work?

These microbes must have the right temperature, nutrients (such as fertilizers), and the amount of oxygen presented in the ground water. If these conditions are just right, then the microbes can grow and multiply, and in turn eat more chemicals. When conditions are not right then the microbes grow too slowly or die. They can even create more harmful chemicals. One way to improve conditions for the microbes is to pump air, nutrients, or other substances (such as molasses) underground.  It is possible to add  microbes if they are needed.

The right conditions for bioremediation cannot always be achieved underground. Sometimes, the weather is too cold or the soil is too dense. At these sites, people might dig up the soil to clean it above ground using heaters and soil mixers to improve the growth conditions for the microbes. Once the soil is dug up then nutrients are added to it, also oxygen may be added by mixing it or forcing air through it.  However, oxygen is not always necessary as some microbes function without oxygen at all.  Under the right conditions microbes can "bioremediate" harmful chemicals.

Sometimes mixing soil can cause the harmful chemicals to evaporate before the microbes can eat them. To prevent these chemicals from polluting the air, people mix the soil in special tanks or buildings where chemicals that have evaporated can be collected and treated.

Microbes can help clean polluted groundwater as well as soil. To do this, people drill wells and pump some of the groundwater into tanks. Here, the water is mixed with nutrients and air before it is pumped back into the air. These nutrients and air help the microbes to bioremediate the ground water. Ground water can also be mixed underground by pumping air and nutrients into the wells.

Once the microbes have used up their available "food" source which is the harmful chemicals, they die. 

Is bioremediation safe?

Bioremediation is very safe because it relies on microbes that naturally occur in soil. These microbes are helpful and pose no threat to people at the site or in the community. Microbes themselves won't hurt you, but don't touch the polluted substances!

No dangerous chemicals are used in bioremediation. The nutrients added to make microbes grow are common, household fertilizers found on lawns and gardens. Because bioremediation changes the harmful chemicals into water and harmless gasses, the chemicals are completely destroyed. To ensure that it works the Environmental Protection Agency tests samples of soil and groundwater.

How long does it take?

The time it takes to bioremediate a site depends on a couple of factors, including types and amounts of harmful chemicals present, size and depth of the site, types of soil and conditions present, and whether cleanup occurs above or underground. These factors vary from site to site. It can take a few months or up to several years to bioremediate a site.

Why use bioremediation?

We use bioremediation because it takes advantage of a natural process. Polluted soil and groundwater can be cleaned at the site without having to be moved somewhere else if the right conditions exist ,without having to dig it up or pump air or can be created.   This also allows cleanup workers to avoid contact with the polluted soil and groundwater. It also prevents release of harmful chemicals into the air. Because microbes change harmful chemicals into water and harmless gasses, few if any wastes are created.

Often bioremediation does not require as much equipment or labor as most other methods. Therefore, it is usually cheaper. Bioremediation has successfully cleaned up many polluted sites and is being used at more than 50 sites across the country.

This information was provided by the EPA in the form of a pdf, http://www.epa.gov/swertio1/download/citizens/bioremediation.pdf