Biochemical Oxidation of Dairy
Wastes , Isolation and Study of
Sludge Microorganisms
LENORE JASEWICZ and NANDOR PORGES
Eastern Regional Research Laboratory
U. S. Department of Agriculture
Philadelphia 18, Pennsylvania
Microorganisms are important in the disposal of dairy and other
wastes. Treatment methods utilize the activities of microbes, and conditions satisfactory for growth and reproduction must be considered in
designing disposal units. For example, a simple treatment of dairy waste
by rapid biochemical oxidation (13) was developed from laboratory
aeration studies in which the activities of the sludge microorganisms
were followed. The reduction in oxygen demand was shown to occur
in four phases (14). First there was the removal or purification of
soluble substances; concomitantly, there was storage of material in the
sludge cells; then there occurred oxidative conversion of stored material
to cell material; and finally, endogenous respiration digested the cell
material.
Curiosity concerning the organisms that have the ability to rapidly
reduce oxygen demand and to cause these changes in aerated sludge-
milk mixtures led to the study presented herein. Investigations were specifically directed toward isolating and identifying the microorganisms
most prevalent in an aerated dairy sludge that had been continually
used in the laboratory. The original seed, obtained from an aerobic
process at a local dairy, was propagated in the laboratory by daily
simulated milk-waste feedings.
Although the biology of waste disposal systems has been studied,
little is known about the organisms associated with the aerobic disposal
of dairy waste. Hotchkiss (9) made bacteriological studies of raw sewage
and of effluents from the Imhoff tank, filter beds, and settling beds of a
municipal system and classified the bacteria according to their physiological activity such as proteolytic, sulfur cycle, and nitrogen cycle forms.
Gaub (6) enumerated and identified the bacteriological population of a
sewage disposal plant and showed the predominance of intestinal forms.
Studies of sewage purification conducted by Butterfield   (3),  Butter-
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