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Oxygen transfer in a fermenter Liu, Ming-Shen

Abstract

The effects of initial pH and the presence of solid particles on the growth rate of Thiobacillus ferrooxidans were studied in shake-flask apparatus. In addition, the effect of the ferrous iron substrate concentration on the specific growth rate of the bacteria was studied using both batch and continuous culture techniques. The effects of oxygen tension on the oxygen uptake rate of the bacteria were also examined. The critical oxygen tension and the saturation constant were found to be 6.5 and 4.5 mmHg respectively. When the oxygen tension was below 4.5 mmHg the bacteria ceased their metabolic activity. The equation that best described the oxygen uptake activity of T. ferrooxidans was found to be, [Chemical Formula]. A method for determining the saturation oxygen solubility in the culture medium is proposed. This value in 9K medium was found to be 6.68 milligrams per liter (in equilibrium with the humid air at 35C). The effect of total iron concentration on this value was also examined. A statistical curve rectification method for calculating K[sub L]a values from a dissolved oxygen concentration-time trace is proposed. Since the proposed method utilizes data directly from oxygen tension-time traces rather than from modified or limited data, it is believed to be more reliable than other techniques in use. The effects of solid pulp densities of up to 20% on K[sub L]a in an agitated tank were studied. An increase in solid pulp density was found to decrease slightly the K[sub L]a value of the system. The equation best correlating K[sub L]a values under various operational conditions is, K[sub L]a = 1.78 x 10⁻⁶(p)⁻[sup 2.84](N)[sup 2.65](V[sub s])[sup 0.57] The addition of the solid particles, although it did not affect the K[sub L] value, was found to reduce the interfacial area of the system, thus reducing the value of K[sub L]a.

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