Monitoring microbe-induced physical property changes using high-frequency acoustic waveform data: Toward the development of a microbial megascope

Abstract

A laboratory investigation was undertaken to determine the effect of microbe generated gas bubbles in controlled, saturated sediment columns utilizing a novel technique involving acoustic wave propagation.Specifically, the effect of denitrifying bacteria on saturated flow conditions was evaluated in light of the stimulated production of N 2 gas and the resulting plugging of the pore throats. The propagation of high frequency acoustic waves through the sediment columns was used to locate those regions in the column where gas accumulation occurred. Over a period of six weeks, regions of gas accumulation resulted in the attenuation of acoustic wave energies with the decreases in amplitude typically greater 2 than one order of magnitude. The temporal production of N 2 gas was evaluated quantitatively using the stable isotope 15 N in the form of added Na 15 NO 3 . This was done to ascertain the origin (biotic or abiotic) of any produced gas with the results showing a dramatic increase in microberespired 15 N 2 . Hydraulic conductivity (Κ s ) measurements made over the experimental period establish the rate and degree of pore throat blocking with the result being a reduction in Κ s by more than 70 percent. The results were compared to a stimulated but non-inoculated control column which showed neither a decrease in acoustic wave amplitudes nor hydraulic conductivity over the same time-period. Final destructive analysis of one column was performed in order to assess the cell density of denitrifying microbes throughout the column. Cell densities were found to be in close agreement with the stoichiometric predictions made prior to initiation of the experiment. Evaluation of the multiple data sets suggests that microbial gas production is both directly detectable using the high frequency acoustic wave approach and capable of significantly altering saturated flow conditions. i

Acoustic and electrical property changes due to microbial growth and biofilm formation in porous media

“…[6] Most biogeophysical investigations have focused on geoelectrical techniques (see, for example, reviews by Atekwana et al [2006] and Atekwana and Slater [2009]) for the investigation of temporal microbial-induced phenomena. Recent studies have focused on the effect of biogenic gases or microbial mediated mineral precipitation on wave propagation in sands and sediments [e.g., Williams, 2002;Williams et al, 2005;DeJong et al, 2006DeJong et al, , 2010. The present study advances the work of Williams et al [2005] and DeJong et al…”

“…Previous seismic studies have demonstrated that seismic methods are sensitive to the products of microbial activity in porous media, such as the production of biogenic gas [ Williams , 2002] and enhanced biomineralization [ Williams et al , 2005; DeJong et al , 2006]. Based on the fact that mineral precipitation was not induced or enhanced in our current experiment, and no large gas bubble formation was observed on the sides of the biostimulated columns (unlike that of Williams [2002]), we attribute the observed amplitude variation in the biostimulated sample in these experiments to biofilm development. This attribution is based on the observed microbes and biofilms in the ESEM images of samples at locations with enhanced/reduced acoustic attenuation.…”

“…Most biogeophysical investigations have focused on geoelectrical techniques (see, for example, reviews by Atekwana et al [2006] and Atekwana and Slater [2009]) for the investigation of temporal microbial‐induced phenomena. Recent studies have focused on the effect of biogenic gases or microbial mediated mineral precipitation on wave propagation in sands and sediments [e.g., Williams , 2002; Williams et al , 2005; DeJong et al , 2006, 2010]. The present study advances the work of Williams et al [2005] and DeJong et al [2006] by investigating the effect of biofilm formation on the spatiotemporal seismic properties of porous media using an acoustic two‐dimensional scanning method [e.g., Li and Pyrak‐Nolte , 1998; Pyrak‐Nolte et al , 1999] in the absence of enhanced precipitation.…”

Strong-Sludge Gas Retention and Release Mechanisms in Clay Simulants

“…This bacterium was successfully used to produce extensive gas bubbles in a column study (Williams, 2002). Microbiological aspects of the Williams study were conducted under the mentoring of PNNL microbiologist Fred Brockman.…”

Treatability Test Plan for an In Situ Biostimulation Reducing Barrier

“…Recent work has investigated the sensitivity of various geophysical measurements to the injection of amendments and to the associated system transformations. These studies have included the use of Induced Polarization and acoustic methods to track changes in iron mineralogy during sulfate reduction at the laboratory scale (Williams et al 2005a(Williams et al , 2005bNtarlagiannis et al 2005), the use of radar and acoustic methods to detect the onset and evolution of gas at the laboratory and field scales (Williams et al 2003), the use of radar and electrical methods for monitoring changes in pore fluid ionic strength at the laboratory and field scales , and the use of Spontaneous Potential (SP) measurements for characterization of redox conditions at the field scale (Williams et al 2005c).…”