Mass Transfer is seen when there is mixing between two components of varying
concentrations. A good example is a small amount of dye being dropped into a bucket
of water. Mass Transfer processes are responsible for the movement of the dye
through the water until equilibrium is reached.1
This is very important when we are
attempting to grow aerobic microbes in media. When the oxygen is bubbled through
the fermenter tank, there will be high concentrations of oxygen near the bubbles but
low concentration everywhere else in the tank. Since oxygen concentration is such avital component of aerobic metabolism, it is essential that there is good transfer of
oxygen across the gas/liquid interface. The Sparger delivers this oxygen. One problem
with gas/liquid interfaces is the formation of foam. The impeller that serves to break
up the foam generally relieves this.