Agitation and Aeration – Section 2

21. In the design of a paddle agitator, the ratio of paddle diameter to tank diameter is normally taken as

A. 0.1
B. 0.8
C. 0.25
D. 0.5

Correct Answer: B. 0.8

22. The oxygen absorption rate can be determined by

A. sodium sulfite oxidation method
B. dynamic gassing out technique
C. direct measurement
D. all of these

Correct Answer: D. all of these

23. Industrial paddle agitators turn at the speed of

A. 20 and 150 rpm
B. 150 and 300 rpm
C. 400 and 800 rpm
D. 1150 rpm

Correct Answer: A. 20 and 150 rpm

24. The dynamic technique is based on the

A. oxygen material balance in an aerated batch fermenter during the growth of microorganisms
B. change of the oxygen concentration
C. oxidation of the sodium sulfite to sodium sulfate
D. oxygen material balance in a fermenter

Correct Answer: A. oxygen material balance in an aerated batch fermenter during the growth of microorganisms

25. The addition of antifoams to an aerated bioreactor will decrease oxygen transfer rates because antifoams

A. increase the tendency of bubbles to coalesce
B. tend to accumulate in the gas-liquid interface
C. reduce the surface tension of the liquid
D. All of the above answers

Correct Answer: D. All of the above answers

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