NMR Imaging of Biofilm Growth in Porous MediaEPA Grant Number: R821268
Title: NMR Imaging of Biofilm Growth in Porous Media
Investigators: Sharma, Mukul M.
Current Investigators: Sharma, Mukul M. , Georgiou, George , Majors, Paul D.
Institution: The University of Texas at Austin
EPA Project Officer: Hiscock, Michael
Project Period: September 1, 1995 through August 1, 1999
Project Amount: $449,760
RFA: Exploratory Research - Chemistry and Physics of Water (1995) RFA Text | Recipients Lists
Research Category: Water , Land and Waste Management , Engineering and Environmental Chemistry
Description:The transport and growth of microorganisms in the subsurface is of relevance to microbial ecology in aquifers and sediments and to the in-situ biodegradation of organic contaminants. In-situ bioremediation (or bioaugmentation) processes have been applied to contaminant sites that contain aliphatic hydrocarbons, aromatics, polycyclic compounds, polychlorinated biphenyls and other organic contaminants. To effectively biodegrade these hazardous chemicals, specific strains of microorganisms need to be provided in-situ at sufficiently high concentrations. Ideal conditions for growth and degradation in the subsurface is a challenging task since the metabolic activity of the cells as measured in fermenters differs significantly from that in a subsurface environment.
A number of studies have been conducted on sand columns to investigate the migration and/or growth of cells in porous media (Fontes, et al., 1991; Sharma, et al., 1985; Taylor et al.., 1990; and Vandevivere et al., 1992). Simulating the growth and migration of the cells in a laboratory environmental is an important step in understanding their behavior in the subsurface. Results from such a study are an essential starting point for any geochemical modeling of the subsurface ecology. In an ideal experiment, the pressure drop, flow rate and the cells and nutrient concentrations in the effluent and influent are monitored as a function of time. This data provides incomplete information about the transport and growth of the biomass in-situ. Withdrawing a fluid sample from sampling ports or monitoring the effluent cell concentration is an erroneous procedure because it ignores the biofilm that may be present on the surfaces of the pores. Indeed in many instances, biofilm growth is the dominant mechanism by which cell populations colonize subsurface environments. There is currently no direct method for monitoring the in-situ cell concentrations in such experiments.
There is, therefore, an urgent need to develop a methodology that will allow us to continuously monitor in-situ cell concentrations in laboratory experiments conducted to simulate the subsurface environment.
Our objective in this proposal is to develop such a methodology. A nuclear magnetic resonance imaging technique is proposed to be developed that will allow us to map in three dimensions the in-situ distribution of biofilms in porous media. In addition data can be obtained on the evolution of the fluid velocity distribution with time as biofilm growth occurs. A brief review of NMR techniques that will be used to locate and identify the cells is provided below. Some preliminary results are provided to demonstrate the feasibility of the idea. Finally, the proposed research tasks are discussed in detail.