Document Type


Date of Award


Degree Name

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


Chemical Engineering, Chemistry and Environmental Science

First Advisor

Basil Baltzis

Second Advisor

Gordon Lewandowski

Third Advisor

Dana E. Knox


It is known that a homogeneous environment having invariant inputs cannot allow for steady state coexistence of any number of pure and simple competitors. However, it has been proven that two pure and simple competitors can coexist at a steady state in two interconnected chemostats, if the conditions are such that they allow a different species to grow faster in each one of the two vessels. It has been also shown that three pure and simple competitors cannot coexist in three interconnected chemostats, even if the conditions are such that a different population could grow faster (have the competitive advantage) in each chemostat. The present study investigates theoretically whether the spatial heterogeneities created by four interconnected chemostats may lead to coexistence of three pure and simple competitors. Computer simulations indicate that there is the domain of coexistence of three species (XYZ) between do-mains of coexistence of two species. If the XYZ domain is between an XY and a YZ region, species Y grows faster than X and Z in two out of the four chemostats, for parameter values leading to XYZ coexistence. It is then concluded that spatial heterogeneities can lead to steady state coexistence of three pure and simple competitors. It is also concluded that N pure and simple competitors cannot coexist in N interconnected reactors; hut one could speculate that if there are N competitors, in order for them to coexist in an environment, this environment must be comprised of two subenvironments each one of which, should be able to maintain N-1 species. In configurations of chemostats then, it seems that one needs 2N-1 vessels. This is a necessary but not sufficient condition. The results for the three species system, are presented in two-dimensional operating diagrams and the effect of parameters on the behavior of the system, is studied to a certain extent.



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