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Volatile Fatty Acids
Volatile fatty acids (VFAs), also called low molecular weight organic acids, are readily metabolized, highly oxidized, organic substrates. Use of these acids as indicators of biodegradation takes two forms.
The first form is looking for the natural appearance of these acids.1,2 Their natural appearance is unequivocal evidence that biodegradation, through oxidation, has occurred. However, in all but the most extreme environments (exceptions are typically landfills 3 ) concentrations of these acids is extremely low. Further, these acids may take many forms. Detection of that many compounds at those extremely low levels is very difficult and not, to the best of our knowledge, commercially available. The second form is to trace the concentration of these acids when they are added to act as a microbial substrate, particularly to induce methanogenic conditions.4 A primary example is the Regenesis product HRC. It is a sorbitol-based poly-lactate and, upon introduction to the groundwater, it releases lactic acid into the groundwater. This lactic acid is then metabolized, with the primary path being conversion of lactic acid to pyruvic acid and, in turn, the pyruvic acid to acetic acid. Two additional VFA's, butyric and propionic acid are also produced through side channels.5 All five of the acids are analyzed through Microseeps propietary VFA analysis method. Reporting levels are given in Table 1. The method is a proprietary modification of EPA 8015. Table 1. Reporting Limits for the VFA’s analyzed by Microseeps.
1 Cozzarelli,I.M, Eganhouse, R.P. and Baedecker, M.J.; Transformation of Monoaromatic Hydrocarbons to Organic Acid in Anoxic Groundwater Environment, Environ. Geol. Water Sci., 16, pp 135-141, 1990.
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