William Stringfellow - Current Research

Research Statement

The major focus of my research is the study of environmental biokinetics.  Microbial activity in both natural and engineered systems is dominated by the balance between growth and decay (cell death). In an open system, the state of the microbial community is determined by the physical and chemical conditions of the environment and is rarely, if ever, limited by availability of microorganisms. The microorganism will grow until the limiting condition is met, whether it is nutrient availability, energy supply, toxicity, or physical parameters such as available surface for attachment or washout conditions.

In engineered systems, the parameters controlling microbial activity can typically be manipulated. The condition of the system is a balance between the inputs and the standing microbial biomass in the system. This balance determines the output from the system. For example, in wastewater treatment, the system is typically maintained in a carbon-limited condition (low carbon-mass to biomass ratio) so that the output (effluent) is carbon free. How the system balances over time and responds to changing conditions is a function of the kinetic relationship between the microbial biomass, the system environment, and the growth limiting condition.  Experimental techniques and modeling are used to determine fundamental kinetic properties of microorganisms and relate those properties to engineering operations with the purpose of achieving specific environmental objectives.