Dr. Aaron Peacock , Environmental Scientist, Haley & Aldrich (Q3 / Summer 2013)
Most organizations view the redevelopment of formerly contaminated sites as a risky proposition, and for good reason. Despite remediation technologies advancements over the last 30 years, most “remediated” sites still have a low level of residual contamination. Usually this stems from impacted groundwater that may be deep below the surface.
That’s all changed, thanks to the application of biological treatments and intrinsic bioremediation — that is, naturally occurring contaminant-degrading microbes — as a “polishing” technology to complete remediation. Biological approaches to remediation usually include adding oxygen or a microbial food source to stimulate naturally occurring bacterial bioprocesses that destroy a specific contaminant. Environmental firms increasingly are using these techniques at later remediation stages to augment traditional remediation methods. Not only are these new techniques reducing redevelopment risks, but they can also help justify no further action or site closures.
Executives responsible for site selection and management can have ongoing peace of mind, too. As low contamination levels may still be present at a “remediated” site, executives and stakeholders are reassured that biological cleanup will continue to destroy harmful contaminants as long as necessary. This knowledge can ease the concerns that come along with redevelopment and recycling of land resources. Here is a look at the analytical technologies behind this peace-of-mind.
Environmental Molecular Diagnostics (EMDs)
During the past decade, bio-scientists have developed new analytical methods called Environmental Molecular Diagnostics (EMDs). EMDs directly measure various biochemical components of microbes. These tests, which consist of a collection of nucleic-acid (DNA)-based tools that analyze environmental samples, provide clues called biomarkers, which inform environmental professionals about current and future site contaminant degradation. Other EMDs can also help pinpoint the source of contamination. EMD techniques can be more accurate and cost-effective than traditional methods in assessing in situ biodegradation for sites in the final stages of remediation. While EMDs don’t take the place of traditional contaminant analysis, they supplement environmental data sets by providing key information previously not accessible by other tests.
The most popular EMD test among environmental practitioners is the quantitative polymerase chain reaction (qPCR) assay. The qPCR test allows professionals to directly detect and quantify microbial genes from the environment. They can determine direct evidence of the microbe’s contaminant degrading activity at a particular site through the presence and relative quantities of various genes in soil or groundwater.
For example, for an organization considering redeveloping a remediated site that exhibits low-level contamination, the environmental engineer could apply EMDs like the qPCR test to check if microbes capable of “polishing off” the remaining contaminant are present and active. If the qPCR test shows high levels of contaminant degrading microbes, this would serve as evidence that contaminant removal is likely to continue. If, on the other hand, the test shows low numbers of contaminant degrading microbes, the organization would know that they may need to consider more active remediation alternatives before undertaking redevelopment.
At this time, there are several specific qPCR assays for various contaminants such as gasoline, solvents, and metals. This list will grow, and with it the significance of EMDs to the redevelopment and environmental management process. EMDs can provide critical knowledge of how effectively nature is cleaning up and reclaiming formerly contaminated sites. This information can in turn provide stakeholders with a level of comfort when proceeding with redevelopment of a contaminated or formally contaminated site.