The Remediation Technology No Chlorinated Solvent Site Should Be Without
It’s no secret that uncontrolled releases of chlorinated solvents, such as TCE (trichloroethylene) and PCE (perchloroethylene), have affected groundwater at sites around the world. In many cases, these large, persistent underground plumes have posed serious remediation challenges. What is less well known, however, is that new bioaugmentation approaches can often rid groundwater of these solvents faster and more cost- effectively than other technologies.
Better, Faster, and Cheaper—Really!
Bioaugmentation is a specialized approach to bioremediation—cleanup by way of natural bacterial processes that degrade contaminants—in which specific microbes are introduced to the contaminated plume. And for many site managers facing stubborn compounds like PCE and TCE, the fundamental question has been, “Is bioaugmentation right for my site?” Today, the answer is, “Almost always.” When carried out with a new and creative in-situ bioreactor-based approach, bioaugmentation can be both cheaper and faster than other technologies, such as chemical oxidation and thermal remediation. For approximately $10,000 in incremental capital costs, microbes can be used to speed the chlorinated solvent remediation process.
Here's How it Works
In the typical bioaugmentation project, large quantities of microbes are purchased and injected into every well identified for treatment on a given site to remediate the contaminated aquifer in the vicinity of each well. For a site with 25 or 30 wells, the cost of bacteria and injection can run into the hundreds of thousands of dollars.
With the in-situ bioreactor-based approach, however, the bacteria are injected into one or two wells, where they are allowed to grow, reproduce, and develop their own colony—a colony that is now acclimated to the affected aquifer. This usually takes 6 months or less. The water from that initial location, which is now teeming with well-adjusted solvent-degrading bacteria, is then pumped directly or transported in a container to the site’s remaining wells, where the microbes get to work on the solvents in those areas of the aquifer. The groundwater has been preconditioned by adding a food source—such as whey—so that the bacteria can begin working immediately. Perfecting the environment in the additional areas of the affected plume takes about 1 month and there is no lag time if this is done prior to the injection of microbes into the “starter” wells.
This approach essentially creates a cost-effective in-situ bioreactor populated by bacteria that are able to start acting immediately upon being introduced into the groundwater. Its incremental cost of $10,000 is associated with purchasing and injecting into one well a modest quantity of Dehalococcoides spp., an anaerobic organism that thrives on chlorinated solvents. For large sites, the approach is so cost-effective that it is often the best cleanup option.
The Bottom Line
This approach can be thought of as a low-cost insurance policy for your bioremediation project that addresses concerns about whether the site will have the appropriate bacteria. It also avoids the costs of monitoring while waiting to see if complete degradation will occur under typical bioremediation approaches. In fact, the savings in time and monitoring costs will generally cover the incremental cost several times over. With this approach, full-scale in-situ bioreactor bioaugmentation is not only affordable, but almost insignificant in terms of the cost. It should be considered for all your chlorinated solvent sites.