Paul J. Sturman

Engineering scale-up of in situ bioremediation processes: a review

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.

Measuring antimicrobial effects on biofilm bacteria: from laboratory to field.

Publisher Summary This chapter discusses the key issues in the development of new assays for biofilms and provides a prototype method for growing and evaluating biofilms in the laboratory. The chapter includes two case studies to demonstrate the application of this methodology for evaluating antimicrobial efficacy of biofilms in (1) the household and (2) in an oil production field. The approach to develop acceptable screening tests is to start with an unbiased and repeatable laboratory protocol and then systematically improving the method to reduce the expense and time and developing a practical method without sacrificing the unbiased and repeatable. The chapter shows repeatability of a prototype laboratory biofilm growth, sampling, and analytical protocol using the rotating disk reactor and demonstrates how the rotating disk reactor (RDR) can be used to simulate various field applications. Because biofilm organisms appear to have greater resistance than their planktonic counterparts, it is believed that new standard analytical methods developed specifically for evaluating antimicrobials against biofilms are an essential need in the effort to control biofilm-related problems.

Interspecies competition in colonized porous pellets

Abstract 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 ( μ max = 0.4 h −1 ) and Klebsiella pneumoniae , a non-motile, facultative organism ( μ max = 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 10 9 to 10 6 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.

Predictive modeling for hot water inactivation of planktonic and biofilm-associated Sphingomonas parapaucimobilis to support hot water sanitization programs

Abstract 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.