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Bioremediation Techniques, Methods & Technology

Instructor: Angela Hartsock

Angela has taught college Microbiology and has a doctoral degree in Microbiology.

In this lesson, we will consider how to boost bioremediation in the environment using nutrients, oxygen, and outside organisms and how to move contaminated soil and water out of the environment into controlled conditions for bioremediation.

The Bioremediation Menu

Humans like options - if you need proof, just walk down the cereal aisle of a grocery store. Even when it comes to bioremediation, we just can't help but come up with different ways to tweak, boost, and advance the technology. Bioremediation at its most basic is the use of living organisms to clean up environmental contaminants.

Bacteria, fungi, and plants have all been used successfully for different types of bioremediation. When we use fungi for bioremediation, we call it mycoremediation. When we use plants, we call it phytoremediation. Otherwise, if we don't specify, then it is mainly bacteria, possibly with the support of fungi and plants. Not to discount the fungi and plants, but bacteria do a lot of the heavy lifting when it comes to bioremediation, so a lot of the methods and technology have been developed with them in mind.

Location, Location, Location

When it comes to bioremediation, location can make a difference. If possible, it is more cost-effective and noninvasive to leave contaminated soil and water in place while bioremediation happens. This is called in-situ bioremediation. But, in some cases when the contaminant is especially toxic or the potential for exposure is too great, the contaminated soil or water must be removed from the environment and treated off-site, still using bioremediation, just changing where it is happening. This method is called ex-situ bioremediation. Within the two categories of in-situ and ex-situ we have additional options.

In-situ Methods

If we just leave everything alone and let nature take its course, so to speak, we call that natural attenuation. But sometimes things need a boost, and there are three main ways we can intervene.

If the organisms we are relying on for bioremediation need some nutrient whose absence is limiting their growth, this can significantly slow down bioremediation. This scenario is kind of like a human with a vitamin deficiency: they aren't as robust, they have difficulty obtaining adequate nutrition and energy, and their growth is impaired: same idea with bacteria, fungi, and plants. So if we know what nutrients our bioremediators are lacking, we can add them to the environment to boost their growth and how quickly they metabolize the pollutant. This process of accelerating bioremediation by supplying key nutrients is called biostimulation.

Did you know that a lot of bacteria and fungi breathe like we do? No, not with lungs of course, but they use similar mechanisms at a cellular level, so they have a similar need for oxygen. In some environments, for example waterlogged soils, oxygen can be limiting. Bioventing is simply adding some air to soils to support bioremediation. A sufficient supply of oxygen ensures an optimal growth rate, and an optimal growth rate ensures rapid breakdown of environmental contaminants.

The whole idea of in-situ bioremediation is to leave everything in its place. This is all good, unless of course there are no organisms present that can break down the contaminant, or maybe they just aren't fast enough. In that case, if we know of an organism that can rapidly remediate the contaminant, we can add the organism to the environment to support bioremediation. Since we are augmenting (adding to or enhancing) the environment with a biological organism we call that bioaugmentation.

Ex-situ Methods

In the event that contaminated soil or water is removed from the environment for ex-situ bioremediation, there is really no reason not to continue to manage or influence the process. That means that some of the methods we already talked about for in-situ bioremediation (like biostimulation, bioventing, and bioaugmentation) are still on the table but since we are managing the whole process at this point, we don't always point it out.

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