Browsing by Author "Sturman, Paul J."

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Biofilm process in porous media - practical applications
(1997) Cunningham, Alfred B.; Warwood, B. K.; Sturman, Paul J.; Horrigan, K.; James, Garth A.; Costerton, J. William; Hiebert, Dwight Randall
Biofouling in the oil industry
(2005) Sanders, P. F.; Sturman, Paul J.
Design and fabrication of biofilm reactors
(2020) Goeres, Darla M.; Pedersen, Stephen; Warwood, B. K.; Walker, Diane K.; Parker, Albert E.; Mettler, Madelyn; Sturman, Paul J.
Laboratory biofilm reactors are tools that researchers use to grow biofilms that exhibit characteristics sufficiently similar to the environment of interest. Numerous biofilm reactors that model various fluid dynamics are described in scientific literature, each with its associated list of advantages and limitations. This chapter focuses on the process used to design and fabricate biofilm reactors with the stated goal of generating a commercial product. The process begins with identifying the environment of interest and key attributes the reactor should include or model. A prototype is then designed, built, and tested in the laboratory. Modifications are made based upon laboratory performance until a design is achieved that is affordable, practical, operationally simple, and relevant and that provides repeatable, convincing results. This process was used to design the industrial surfaces biofilm reactor, developed to model cooling tower biofilms but suitable to study biofilms grown under low shear, high gas transfer, and intermittently wet conditions.
Diffusion and reaction within porous packing media: A phenomenological model
(1993-04) Jones, Warren L.; Dockery, Jack D.; Vogel, C. R.; Sturman, Paul J.
A phenomenological model has been developed to describe biomass distribution and substrate depletion in porous diatomaceous earth (DE) pellets colonized by Pseudomonas aeruginosa. The essential features of the model are diffusion, attachment and detachment to/from pore walls of the biomass, diffusion of substrate within the pellet, and external mass transfer of both substrate and biomass in the bulk fluid of a packed bed containing the pellets. A bench-scale reactor filled with DE pellets was inoculated with P. aeruginosa and operated in plug flow without recycle using a feed containing glucose as the limiting nutrient. Steady-state effluent glucose concentrations were measured at various residence times, and biomass distribution within the pellet was measured at the lowest residence time. In the model, microorganism/substrate kinetics and mass transfer characteristics were predicted from the literature. Only the attachment and detachment parameters were treated as unknowns, and were determined by fitting biomass distribution data within the pellets to the mathematical model. The rate-limiting step in substrate conversion was determined to be internal mass transfer resistance; external mass transfer resistance and microbial kinetic limitations were found to be nearly negligible. Only the outer 5% of the pellets contributed to substrate conversion. .
Effects of motility and adsorption rate coefficient on transport of bacteria through saturated porous media
(1993-10) Camper, Anne K.; Hayes, J. T.; Sturman, Paul J.; Jones, Wallace E.; Cunningham, Alfred B.
Three strains of Pseudomonasfluorescens with different motility rates and adsorption rate coefficients were injected into porous-medium reactors packed with 1-mm-diameter glass spheres. Cell breakthrough, time to peak concentration, tailing, and cell recovery were measured at three interstitial pore velocities (higher than, lower than, and much lower than the maximal bacterial motility rate). All experiments were done with distilled water to reduce the effects of growth and chemotaxis. Contrary to expectations, motility did not result in either early breakthrough or early time to peak concentration at flow velocities below the motility rate. Bacterial size exclusion effects were shown to affect breakthrough curve shape at the very low flow velocity, but no such effect was seen at the higher flow velocity. The tendency of bacteria to adsorb to porous-medium surfaces, as measured by adsorption rate coefficients, profoundly influenced transport characteristics. Cell recoveries were shown to be correlated with the ratio of advective to adsorptive transport in the reactors. Adsorption rate coefficients were found to be better predictors of microbial transport phenomena than individual characteristics, such as size, motility, or porous-medium hydrodynamics.
Engineering scale-up of in situ bioremediation processes: a review
(1995-09) Sturman, Paul J.; Stewart, Philip S.; Cunningham, Alfred B.; Bouwer, Edward J.; Wolfram, James H.
To be useful to field practitioners, advances in bioremediation research must be capable of being scaled up from the laboratory to the field. The phenomena which control the rate at which biodegradation proceeds are typically scale-dependent in nature. Failure to understand and account for scale-dependent variables, such as mass transport limitations, spatial heterogeneities and the presence of competing microorganisms, may inhibit the effectiveness of field-scale bioremediation designs. This paper reviews and evaluates the methods available for characterization of the processes effecting bioremediation at scales ranging from the laboratory to the field. Questions facing the field-scale practitioner of bioremediation are addressed in a manner which highlights the current state of research, the reliability of results and the extent to which laboratory-scale research accurately reflects common field conditions. Where gaps or inadequacies exist in our current knowledge or methods, research needs are identified. This review is intended to complement existing work by providing a framework from which to assess the importance of scale of observation to a particular result or conclusion, thereby providing an integrated approach to the scale-up process.
Interspecies competition in colonized porous pellets
(1994-04) Sturman, Paul J.; Jones, Warren L.; Characklis, William G.
Packed-bed bioreactors filled with diatomaceous earth (D.E.) pellets were used to evaluate the effects of competition between inoculated and invading microbial species on the spatial and temporal distribution of microorganisms within an individual pellet. The (D.E.) pellets were cylinders 6 mm in diameter and 5–10 mm long with a mean pore diameter of 20 μm. Bench-scale experiments evaluated competition between two distinct microbial species: Pseudomonas aeruginosa, a motile, obligate aerobe (μmax = 0.4 h−1) and Klebsiella pneumoniae, a non-motile, facultative organism (μmax = 2.0 h−1). Organism growth rate appeared to be more important than motility or order of introduction in determining organism spatial and temporal distribution within the pellets. Pilot-scale experiments used pellets colonized with a pseudomonad growing on chlorobenzene as the sole carbon and energy source. Organic-rich ground water containing benzene, chlorobenzene and a population of indigenous microorganisms was used as feed. Pellet concentrations of the inoculated pseudomonad dropped from 109 to 106 colony forming units (cfu) ml−1 pellet volume over 15 days. These experiments demonstrate that inoculated organisms within porous packing media may undergo significant loss in colonization numbers when faced with competition from faster growing organisms.
Measuring antimicrobial effects on biofilm bacteria: From laboratory to field
(1999) Zelver, Nick; Hamilton, Martin A.; Pitts, Betsey; Goeres, Darla M.; Walker, Diane K.; Sturman, Paul J.; Heersink, Joanna
Monitoring of microbial souring in chemically treated, produced-water biofilm systems using molecular techniques
(2005-04) Kjellerup, B. V.; Veeh, Richard Harold; Sumithrarathne, P.; Thomsen, T. R.; Buckingham-Meyer, Kelli; Frolund, B.; Sturman, Paul J.
The identification of bacteria in oil production facilities has previously been based on culture techniques. However, cultivation of bacteria from these often-extreme environments can lead to errors in identifying the microbial community members. In this study, molecular techniques including fluorescence in situ hybridization, PCR, denaturing gradient gel electrophoresis, and sequencing were used to track changes in bacterial biofilm populations treated with nitrate, nitrite, or nitrate+molybdate as agents for the control of sulfide production. Results indicated that nitrite and nitrate+molybdate reduced sulfide production, while nitrate alone had no effect on sulfide generation. No long-term effect on sulfide production was observed. Initial sulfate-reducing bacterial numbers were not influenced by the chemical treatments, although a significant increase in sulfate-reducing bacteria was observed after termination of the treatments. Molecular analysis showed a diverse bacterial population, but no major shifts in the population due to treatment effects were observed.
Predictive modeling for hot water inactivation of planktonic and biofilm-associatedSphingomonas parapaucimobilis to support hot water sanitization programs
(2016-06) Kaatz Wahlen, L.; Parker, Albert E.; Walker, Diane K.; Pasmore, M.; Sturman, Paul J.
Hot water sanitization is a common means to maintain microbial control in process equipment for industries where microorganisms can degrade product or cause safety issues. This study compared the hot water inactivation kinetics of planktonic and biofilm-associated Sphingomonas parapaucimobilis at temperatures relevant to sanitization processes used in the pharmaceutical industry, viz. 65, 70, 75, and 80°C. Biofilms exhibited greater resistance to hot water than the planktonic cells. Both linear and nonlinear statistical models were developed to predict the log reduction as a function of temperature and time. Nonlinear Michaelis-Menten modeling provided the best fit for the inactivation data. Using the model, predictions were calculated to determine the times at which specific log reductions are achieved. While ≥80°C is the most commonly cited temperature for hot water sanitization, the predictive modeling suggests that temperatures ≥75°C are also effective at inactivating planktonic and biofilm bacteria in timeframes appropriate for the pharmaceutical industry.
Scale-up implications of respirometrically determined microbial kinetics parameters
(1994) Sturman, Paul J.; Sharp, Robert R.; DeBar, J. B.; Stewart, Philip S.; Cunningham, Alfred B.; Wolfram, James H.
Use of soil column test apparatus for evaluation of in situ bioremediation potential
(1990) Jones, Warren L.; Sturman, Paul J.; Ellison, C.; Camper, Anne K.; Inskeep, William P.; Rogers, Robert D.; Cunningham, Alfred B.