FEROXSM Biological Update
Microbiological Effect of using Zero-Valent Iron Powder
As a follow up to the article in our Winter newsletter, additional data has been collected regarding the effect of FEROXSM powder on microbiological processes. As part of the monitoring and verification program of a recently installed FEROXSM system, ARS evaluated the potential enhancement to the microbial community as a result of the emplacement of the ZVI powder. ARS had previously postulated that the uniform dispersion of the iron powder into the subsurface would effectively create a highly reducing environment in the aquifer which is conducive to microbiological dehalogenation. Under this project, pre- and post-injection groundwater samples were analyzed for phospholipid fatty acids (PLFA).
The analysis of PLFA is an effective tool for monitoring microbial responses to the environment. Phospholipid fatty acids are found in the membranes of all living cells but decompose quickly upon cell death; therefore PLFA content provides a quantitative measure of the viable microbial biomass present. The PLFA profiles simultaneously contain general information about the phylogenetic identity and physiological status of microbes. In short, PLFA analysis tells us what types and how many of the microbes are present in a system and how they are responding to environmental factors.
Data from the groundwater taken from within and adjacent to our FEROXSM treatment zone showed an increase (from 1.7 x 105 to 4.7 x 105 cells/ml) of biomass within three months after the injection. Both pre- and post-injection PLFA samples contained diverse community structures that were primarily composed of Gram-negative bacteria. This type of bacteria are fast growing and metabolically diverse organisms able to utilize a wide variety of carbon sources and are known to degrade chlorinated solvents by anaerobic dechlorination.
In future newsletters we'll update this topic supporting our hypothesis of the benefits FEROXSM powder has on insitu microbial communities.
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