Date of Award

Fall 1994

Document Type

Thesis

Degree Name

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

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Samir S. Sofer

Second Advisor

Richard B. Trattner

Third Advisor

Barbara B. Kebbekus

Abstract

The primary purpose of this work is to help define the optimum window of operations for an immobilized cell oxidative bioreactor. The analytical technique employed requires no outside verification (such as G.C. analysis) and is independent of liquid flow rate. Method of aeration has been determined to be an important parameter for optimizing bioreactor efficiency, and optimization of the quantity of hydrogen peroxide added to provide oxygen during bio-oxidation has been investigated. Ammonium hydroxide as a fixed nitrogen source can be used to restore the vitality of the bioreactor under certain conditions.

The effects of several different methods of providing oxygen on bio-oxidation were analyzed. These methods included aeration at the center of the reservoir (18" from the pump inlet leading to the biosupport), aeration near the pump inlet (3" away), and providing oxygen by means of injection of hydrogen peroxide into the reservoir. Generally, aeration nearer to the cylinder led to faster initial rates of biodegradation of the phenol. With hydrogen peroxide, an injection of 0.5 ml of 30% H2O2 (3.8 ppm H2O2) best facilitated the bio-oxidation of 0.5 g phenol, whereas higher amounts caused inhibition.

The use of ammonium hydroxide to speed up slow reaction rates has been demonstrated, with the minimum effective injection determined to be approximately 10 ml concentrated NH4OH (21 ppm). Quantitation using the dissolved oxygen reaction patterns has been briefly discussed. The effect of both dilution and of changing liquid flow rate on baseline dissolved oxygen levels has been analyzed. Also, a guide has been prepared for the recognition of some abnormal dissolved oxygen level patterns for troubleshooting and assessing systemic causes and solutions and general bioreactor operation observations and suggestions have been provided.

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