New Developments in Dairy
Waste Treatment
DR.   K.   L.  SCHULZE
Yeomans Brothers Company
1999 North Ruby Street
Melrose Park, Illinois
Dairy wastes and especially cheese wastes are known not only for
being high in B.O.D. but also for having a very high immediate oxygen
demand. As Hoover and Porges stated in 1952 in their study on assimilation of dairy wastes by activated sludge, this demand may be as high
as 1.38 p.p.m. of oxygen per minute. For a 3000 gallon tank this
means that 15.65 grams of oxygen have to be transferred from the air
into the liquid every minute. This much oxygen is contained in 2.2
cubic feet of air. It is easy enough to blow 2.2 cubic feet of air per
minute into the tank; the question is how much of the oxygen actually
gets into solution? Supplying oxygen at such a rate is still one of the
major problems in the aerobic treatment of dairy wastes. Another
problem is the tendency of porous materials used in air diffusion to clog.
Similar problems in the yeast industry in Germany prompted the
writer to try to develop a mechanical aeration unit which would be
highly efficient in the transfer of oxygen into the liquid, non-clogging
and also control foaming.
The apparatus which has been used in the experiments is shown in
Figure 1. It is an application of similar devices which have been and
are used in yeast production. In the center of the round or square
tank there is a rotating hollow shaft of about two inches outside diameter. Fastened to the shaft is the rotor which consists of a hollow disc
with several nozzles at its circumference. Close to and above the rotor
if a down-draft with a funnel shaped distributor, held and centered by
tie rods. The upper end of the down-draft tube is flared out to a
funnel shaped intake port. The liquid level is maintained constant and
its height is determined by the effluent pipe. The intake port of the
down-draft tube is adjustable so that it can be set somewhat below the
liquid level. The raw feed line ends directly above the intake funnel.
The rotor can be seen in Figure 2. It is rotated so that the openings
of the nozzles show backward. This is just one of the many types of
rotors being used.
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