New Design for an Activated Sludge
Plant to Treat Milk Wastes
PAUL   M.   THAYER
District Manager
Chicago Pump Co.
Chicago, Illinois
The treatment of milk wastes presents many problems to challenge
the designing engineer. Requirements for a satisfactory solution of
this problem indicate that a plant must be:
(1) Low in first cost, (2) simple to operate so that the plant can
be operated by local unskilled labor, (3) free from odor or other
nuisance, (4) give a high degree of treatment.
A simple type of plant treating the liquid waste and the sludge
resulting therefrom in one operation meets the foregoing requirements.
Recently activated sludge treatment plants of this type were installed
in two milk processing plants in Ohio. They are the George Schell
Creamery, near Germantown, Ohio, Walter A. Rabold and John F.
Surmann, Architects & Engineers; and the Blossom Hill Dairy in
Dayton, Ohio, Steller Engineering Company, Consultants. The latter
installation is of particular interest as it is located in a residential
section. Consequently, the treatment plant must not be unsightly and
must be free from any odor or other nuisance.
The Schell Creamery was designed to process 15,000 pounds of
milk a day. In addition to these dairy wastes, some food waste is intro¬
duced to the system through the operation of a lunchroom in the plant.
All cooling water and other uncontaminated water is disposed of
through a separate sewer.
The waste treatment plant consists of two aeration tanks in series
and one hopper bottom final settling tank. The settled sludge is returned
to the head end of the aeration tank, next to the raw sewage inlet by
means of an air lift. Flow through the plant is by gravity; the total
head loss being approximately eight inches. Air is supplied to the
aeration tanks through Precision diffuser tubes mounted on two swing
units, one in each aeration tank, which permits swinging the tubes out
of the mixed liquor for cleaning or changing without shutting down
operations or draining the tank.  The pipe connecting the aeration tank
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