Date of Award

Spring 1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemical Engineering - (Ph.D.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Samir S. Sofer

Second Advisor

Ching-Rong Huang

Third Advisor

Piero M. Armenante

Fourth Advisor

Basil Baltzis

Fifth Advisor

Peter F. Strom

Abstract

The purpose of this work was to study bio-oxidative destruction of several substrates in an immobilized cell batch bioreactor in recirculation configuration. This system was used in three cases: a series of substrates usually used as monomers, ethylene glycol and its tetramer, and phenol under magnetic irradiation. In addition, kinetic studies were performed and experimental versus predicted results compared.

The substances styrene, methyl methacrylate (MMA), and β-hydroxybutyric acid (HBA), common monomers, were biologically treated using an acclimated mixed microbial community immobilized in calcium alginate gel. A comparison of biodegradation rates (3.3, 9.4, and 15 ppm/hr for styrene, MMA, and HBA, respectively, at 75 ppm starting concentration, with essentially constant biomass concentration) indicates the scale of difficulty in biodegrading these monomers. The results show that styrene, which has a ring structure, as opposed to an open chain structure, is relatively more difficult to biodegrade. These results indicate that biodegradability of a substrate is related to its structure.

Biodegradation of ethylene glycol and tetraethylene glycol was also studied. During the biodegradation of ethylene glycol, qualitative analysis showed that the fairly stable intermediates were formed. One of them was identified as being formaldehyde, which is more toxic than ethylene glycol. Therefore monitoring of the parent compound concentration alone does not always provide adequate information regarding complete mineralization of an oligomer.

Studies on the effect of magnetic fields on the rate of biodegradation were also conducted. It was observed that by applying a magnetic South polar field to the process, biological oxidation is enhanced. A magnetic North field was found to inhibit oxidation.

It was also observed that by acclimating the free microorganisms to the South magnetic field prior to immobilization and by subsequently further applying the South polar field to the gel immobilized microorganisms during oxidation, biodegradation is enhanced to a greater degree. Enhancement of oxidation by up to one order of magnitude was obtained after 10 days when a magnetic South field of 0.15 tesla was applied to the bioreactor. The rate of biodegradation was observed to be a function of magnetic field strength and time of exposure.

A preliminary mathematical model describing the process is presented, along with recommendations for improvement of this bioreactor system.

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