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BIOREMEDIATION

ENGINEERING A

BETTER FUTURE

A contaminant should have a relatively high potential of biodegradability in order to be a candidate for bioremediation.

Conditions that affect Bioremediation

In addition to the contaminant's biodegradability, the suitability of a site for bioremediation depends on the site's geology and the contaminant's chemical characteristics. For intrinsic bioremediation, the key site characteristics include consistent groundwater flow throughout the seasons; pH stability; and high concentrations of oxygen, nitrate, sulfate, and/or ferric iron. For engineered bioremediation, the key site characteristics are permeability of the subsurface, uniformity of the subsurface, and relatively low concentrations of nonaqueous-phase contaminants. No single set of site characteristics will favor bioremediation of all contaminants. Some compounds can only be degraded when oxygen is absent, but destruction of others requires that oxygen be present. How the bioremediation system may perform under variable and not perfectly known conditions must also be considered.

What is Bioremediation?

Bioremediation is the natural process of using microorganisms, generally bacteria, to destroy and/or reduce the toxicity of hazardous contaminants in the environment.

In order to operate, the microorganisms require the availability of a variety of materials to generate the energy and nutrients necessary for reproduction. In some cases the natural conditions at the contaminated site provide all the essential materials in large enough quantities that bioremediation can occur without human interventiona process called intrinsic bioremediation.

More often bioremediation requires the construction of engineered systems to supply microbe-stimulating materials -- a process called engineered bioremediation. Engineered bioremediation accelerates the biodegradation process by establishing and maintaining a controlled environment that encourages the growth of the organisms.

When is Bio-Remediation Appropriate?

The first and most important question when considering bioremediation is, "Can the contaminants at the site be biodegraded, either by the organisms at the site or by organisms that could be successfully added to the site?" Some contaminate compounds are more easily degraded than others. In general, petroleum hydrocarbons are the most easily degraded.

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