Browsing by Author "Grunewald, Elliot"

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Biofilm detection in a model well-bore environment using low-field magnetic resonance
(2015-09) Kirkland, Catherine M.; Hiebert, Dwight Randall; Phillips, Adrienne J.; Grunewald, Elliot; Walsh, David O.; Seymour, Joseph D.; Codd, Sarah L.
This research addresses the challenges of the lack of non-invasive methods and poor spatiotemporal resolution associated with monitoring biogeochemical activity central to bioremediation of subsurface contaminants. Remediation efforts often include growth of biofilm to contain or degrade chemical contaminants, such as nitrates, hydrocarbons, heavy metals, and some chlorinated solvents. Previous research indicates that nuclear magnetic resonance (NMR) is sensitive to the biogeochemical processes of biofilm accumulation. The current research focuses on developing methods to use low-cost NMR technology to support in situ monitoring of biofilm growth and geochemical remediation processes in the subsurface. Biofilm was grown in a lab-scale radial flow bioreactor designed to model the near wellbore subsurface environment. The Vista Clara Javelin NMR logging device, a slim down-the-borehole probe, collected NMR measurements over the course of eight days while biofilm was cultivated in the sand-packed reactor. Measured NMR mean log T2 relaxation times decreased from approximately 710 to 389 ms, indicating that the pore environment and bulk fluid properties were changing due to biofilm growth. Destructive sampling employing drop plate microbial population analysis and scanning electron and stereoscopic microscopy confirmed biofilm formation. Our findings demonstrate that the NMR logging tool can detect small to moderate changes in T2 distribution associated with environmentally relevant quantities of biofilm in quartz sand.
Detecting Microbially Induced Calcite Precipitation in a Model Well-Bore Using Downhole Low-Field NMR
(2017-02) Kirkland, Catherine M.; Zanetti, Sam; Grunewald, Elliot; Walsh, David O.; Codd, Sarah L.; Phillips, Adrienne J.
Microbially induced calcite precipitation (MICP) has been widely researched recently due to its relevance for subsurface engineering applications including sealing leakage pathways and permeability modification. These applications of MICP are inherently difficult to monitor nondestructively in time and space. Nuclear magnetic resonance (NMR) can characterize the pore size distributions, porosity, and permeability of subsurface formations. This investigation used a low-field NMR well-logging probe to monitor MICP in a sand-filled bioreactor, measuring NMR signal amplitude and T2 relaxation over an 8 day experimental period. Following inoculation with the ureolytic bacteria, Sporosarcina pasteurii, and pulsed injections of urea and calcium substrate, the NMR measured water content in the reactor decreased to 76% of its initial value. T2 relaxation distributions bifurcated from a single mode centered about approximately 650 ms into a fast decaying population (T2 less than 10 ms) and a larger population with T2 greater than 1000 ms. The combination of changes in pore volume and surface minerology accounts for the changes in the T2 distributions. Destructive sampling confirmed final porosity was approximately 88% of the original value. These results indicate the low-field NMR well-logging probe is sensitive to the physical and chemical changes caused by MICP in a laboratory bioreactor.
In situ detection of subsurface biofilm using low-field NMR: A field study
(2015-09) Kirkland, Catherine M.; Herrling, M. P.; Hiebert, Dwight Randall; Bender, A. T.; Grunewald, Elliot; Walsh, David O.; Codd, Sarah L.
Subsurface biofilms are central to bioremediation of chemical contaminants in soil and groundwater whereby micro-organisms degrade or sequester environmental pollutants like nitrate, hydrocarbons, chlorinated solvents and heavy metals. Current methods to monitor subsurface biofilm growth in situ are indirect. Previous laboratory research conducted at MSU has indicated that low-field nuclear magnetic resonance (NMR) is sensitive to biofilm growth in porous media, where biofilm contributes a polymer gel-like phase and enhances T2 relaxation. Here we show that a small diameter NMR well logging tool can detect biofilm accumulation in the subsurface using the change in T2 relaxation behavior over time. T2 relaxation distributions were measured over an 18 day experimental period by two NMR probes, operating at approximately 275 kHz and 400 kHz, installed in 10.2 cm wells in an engineered field testing site. The mean log T2 relaxation times were reduced by 62% and 43%, respectively, while biofilm was cultivated in the soil surrounding each well. Biofilm growth was confirmed by bleaching and flushing the wells and observing the NMR signal’s return to baseline. This result provides a direct and noninvasive method to spatiotemporally monitor biofilm accumulation in the subsurface.