The question of bioaugmentation, or the addition of one or more species of microbes into a system, has been debated since the late 1990’s. AFCEE’s Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents (AFCEE 2004, page 2-17) states that “In practice, microorganisms capable of degrading PCE and TCE to cis-DCE should be considered ubiquitous in the subsurface environment.” This would suggest that degrading down to cis-DCE is pretty much just a balance of electron donors and acceptors for almost all sites. And since cis-DCE can degrade through a number of both aerobic and anaerobic pathways, for most sites,  more...

The question of bioaugmentation, or the addition of one or more species of microbes into a system, has been debated since the late 1990’s. AFCEE’s Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents (AFCEE 2004, page 2-17) states that “In practice, microorganisms capable of degrading PCE and TCE to cis-DCE should be considered ubiquitous in the subsurface environment.” This would suggest that degrading down to cis-DCE is pretty much just a balance of electron donors and acceptors for almost all sites. And since cis-DCE can degrade through a number of both aerobic and anaerobic pathways, for most sites, the issue of adding microbes becomes one of economics rather than of risk. The AFCEE guidance document also discusses evidence that mixtures of microbes capable of complete degradation of PCE to ethene in the absence of Dehalococcoides suggests that specific microbial strains are not necessarily required to achieve complete dechlorination. Site work over the years has bolstered this idea.

But bioaugmentation can play an important role in a remedial approach. Although the indigenous dechlorinating populations may arguably be the most acclimated to a specific site, geochemical conditions may inhibit optimal growth such that sufficient numbers of microbes may not be available to support robust dechlorination. At other times, sufficient quantities of dechlorinating microbes capable of quickly promoting complete dechlorination to ethene may not be present. In these cases, bioaugmentation can be an valuable tool.

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