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Technology Uses Microbes to Neutralize Pollutants

Technology Uses Microbes to Neutralize Pollutants

Remediation Options Remove Soil Contaminants

BY MEREDITH L. RICHARDS and STEPHEN L. MARSH

Special to the Business Journal

The problem: You’re a successful businessperson, the owner of a busy franchise that happens to sit on land that was previously used as a gas station.

Unbeknownst to you, gasoline storage tanks are still buried beneath your flourishing enterprise and are slowly leaking fuel.

Over the years, the fuel has migrated across the property line, underneath neighboring properties. The contamination is discovered during normal due diligence associated with the sale of the adjacent property.

Catastrophe? Not for some: The table’s been set, and those leaking underground storage tanks are the waiters serving up a feast for millions of hungry microorganisms.

Microorganisms are at the center of an evolving technology called bioremediation, the use of living organisms, including microorganisms and plants, to remove, alter or immobilize environmental contaminants. It is not, however, a new technology, but has been around for years.

Consider the familiar septic tank, which is typically designed to allow effluent to flow from the tank into the surrounding soil, where natural biological activity removes contaminants before the effluent reaches the water table.

So, how does bioremediation work? Like traditional remediation technologies, bioremediation cleans up environmental contaminants. Unlike traditional remediation technologies, the necessary microorganisms are naturally occurring in many soils and they can remove pollutants by using them as a food source.

Microorganisms break pollutants down into less harmful components such as carbon dioxide, methane and water, or by otherwise sequestering the harmful components from the environment. (See Table 1 for a list of microorganisms and their effect on environmental contaminants.) Microorganisms have been successfully used to remediate gasoline, oil, sewage, pesticides, herbicides, wood preservatives, degreasers and dry cleaning chemicals.

Phytoremediation, a cousin of microoganism-based bioremediation, involves the use of plants to remove environmental contaminants. Certain plants, such as poplar trees and mustard, are known to accumulate metals into their shoots and leaves. A common application of phytoremediation, therefore, is to remove heavy metals from soils.

– Advantages, Drawbacks

Traditional remediation technologies often involve extracting contaminants from the subsurface with water or air, or excavating contaminants along with vast amounts of the surrounding soil. Both extraction and excavation have certain drawbacks. Contaminants may bind to certain types of soils, reducing the effectiveness of extraction. Soils are often heterogeneous, causing substances to be extracted at different rates, and often increasing the amount of time needed to complete cleanup of the contaminant. In addition, excavation and disposal of large amounts of contaminated soil can be very expensive.

Bioremediation’s principal advantage over traditional remediation technologies is cost savings. Microorganisms necessary to digest pollutants are already living in many soils. Thus, remediation can take place in the ground, eliminating the cost of excavation and disposal. In-ground remediation also minimizes disruption of aboveground business activities.

However, because it is a natural process, bioremediation can be slower than the physical removal of contaminants. Additionally, naturally occurring bacteria may require a helping hand, in the form of oxygen and nutrients delivered into the soil. Unfortunately, bioremediation often cannot be used if the zone of contamination is expanding, because governmental agencies usually require immediate remedial methods to prevent further spreading of contaminants.

Phytoremediation also has some limitations. For example, plants that have sequestered heavy metals may need to be harvested and disposed of in order to prevent fallen leaves and dying plants from re-contaminating the underlying land.

– Solution Depends Upon Contaminant

The appropriate remediation technology for any particular situation , whether bioremediation, phytoremediation or traditional technologies , depends on the type, extent and dynamics of the pollutants. It also depends upon federal, state and local regulatory requirements, which legal counsel can help navigate.

Researchers are in the process of developing genetically modified microorganisms and plants in which the natural ability to uptake, alter, or stabilize environmental contaminants is enhanced. These technologies will present their own unique issues, such as how to control genetically altered organisms once they are released into the environment.

In the meantime, bioremediation offers another alternative to those facing costly environmental problems.

Richards, originally trained as a biologist, is a member of the Environmental Practice Group at Luce, Forward, Hamilton & Scripps LLP in the San Diego office. Marsh, originally trained as a chemist, is a partner and chair of Luce Forward’s Environmental Practice Group.




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