Document Type

Thesis

Date of Award

5-31-1987

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Basil Baltzis

Second Advisor

Gordon Lewandowski

Third Advisor

Dana E. Knox

Abstract

It is known that two microbial populations competing for a single non-renewable resource in a homogeneous environment with time-invariant inputs cannot coexist in a steady state. The case where two microbial populations exhibiting reversible attachment to the walls of a chemostat compete for a single resource is studied theoretically. Because of the cell's attachment to the walls, the environment is no longer homogeneous. The present study considers the case where the attached cells form no more than a monolayer. The Baltzis-Fredrickson model is used to represent the attachment to the walls. In one system the attachment of cells of the two species is assumed to occur independently; that is, each competitor selectively attaches to a different solid surface in the bio-reactor. In the other system the two species compete for space on a common solid surface. Analytical and numerical results indicate that in most of the cases, the two competitors can coexist in a stable steady state for a wide range of the operating parameter space. In the system where wall attachment occurs independently coexistence is stable if it is meaningful. In the system where the two species compete for wall space, coexistence may become unstable when both species have a strong tendency to attach on the solid surface. In such cases either population can exclude the other; in a chemostat the winner will be decided (and can be controlled) by the composition of the original inoculum.

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