Effect of Microbial Metabolic Byproducts on Electrical Properties of Unconsolidated Sediments

Abstract

Recent laboratory and field studies have documented enhanced electrolytic and interfacial electrical properties of unconsolidated sediments due to microbial activity. However the source mechanism of enhanced conduction and polarization is not very well understood. In this regard, laboratory measurements were conducted to investigate the effect of metabolic byproducts of microbial activity (i.e. organic acids and biosurfactants) on low frequency electrical properties of unconsolidated sediments. Uniform sand samples were saturated with different concentrations of individual organic acids (e.g., acetic, butyric, lactic, propionic) and electrical measurements were obtained in the frequency range 0.1-1000 Hz. The same procedure was repeated using different concentrations of natural ionic biosurfactants (aqueous solution of Rhamnolipids). It was observed that the electrolytic and interfacial electrical properties of unconsolidated sands increased with increasing concentrations of organic acids as well as the biosurfactants. A significant increase in the interfacial electrical properties of biosurfactants was observed at concentrations greater than the critical micelle concentration (CMC), which indicates that biosurfactants are highly polarized above the CMC. In addition, the observed magnitude of change in real conductivity was greater (two orders) than the imaginary conductivity component (one order). This indicates that the increase in concentrations of organic acids and biosurfactants increase the electrolytic conductivity to a greater degree than the interfacial conductivity. We conclude that metabolic byproducts of microbial activity can directly impact the electrical properties of unconsolidated sediments with implication of using electrical methods for quantitative assessments of microbial activity which are often required for evaluating the progress of bioremediation processes and microbial enhanced oil recovery.

Meeting Name

19th Symposium on the Application of Geophysics to Engineering and Environmental Problems (2006: Apr. 2-6, Seattle, WA)

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Bio-surfactants; Critical Micelle Concentration (CMC); Electrical Measurement; Electrical Methods; Electrolytic Conductivity; Enhanced Oil Recovery; Field Studies; Frequency Ranges; Interfacial Conductivity; Interfacial Electrical Properties; Laboratory Measurements; Low Frequency Electrical Property; Metabolic Byproducts; Microbial Activities; Propionic; Quantitative Assessments; Rhamnolipids; Source Mechanisms; Unconsolidated Sands; Unconsolidated Sediment; Biomolecules; Bioremediation; Byproducts; Critical Micelle Concentration; Fatty Acids; Geophysics; Metabolism; Organic Acids; Sedimentology; Sediments; Electric Properties

International Standard Book Number (ISBN)

978-1622760657

International Standard Serial Number (ISSN)

1554-8015

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2006 Environmental and Engineering Geophysical Society (EEGS), All rights reserved.

Publication Date

01 Apr 2006

Link to Full Text

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