The Occurrence of
Fungi in Activated Sludge
WILLIAM BRIDGE COOKE, Mycologist
Biological Treatment Research Activities
Cincinnati Water Research Laboratory
Federal Water Pollution Control Administration
Cincinnati, Ohio
WESLEY O. PIPES, Professor
Sanitary Engineering Department
Northwestern University
Evanston, Illinois"
INTRODUCTION
Lackey and Dixon (1) stated that "activated sludge frequently contains branching fungi" and listed "fungi, unid. " as members of populations observed in four
of the 11 Hays Process contact aeration treatment plants studied. This was the
only report on fungi in activated sludge found by Cooke (2) in a literature survey
on fungi in polluted water and sewage. Cooke (3,4) included isolates of filamentous fungi in lists published in 1957 and 1963, and Cooke et al. (5), included
yeast isolates in a list published in 196Q.
In 1958, Cooke and Ludzack (6) reported on the predacious fungus Zoophagus
insidians which had invaded experimental activated sludge units to the detriment
of an experiment on cyanide waste treatment at Cincinnati, Ohio. Later, Pipes
(7), and Pipes and Jenkins (8) reported on experiences with this organism at Richmond, California. Pipes (7) also indicated that several species of nematode trapping fungi were also found in activated sludge.
Hawkes (.9) observed that fungi are seen in activated sludge, but stated the
"fungi do not become established in the sludge" because of unfavorable habitat
factors and competitive levels of other organisms. Exceptional situations in which
fungi do become established include those where "favorable" oxygen, pH and nitrogen levels aid the fungi in maintaining populations competitively with bacteria and protozoans. Jones (10,11,12) found that iGeotrichum candidum is an
important sludge bulking organism. Pipes (13) reviewed the published work on the
relationship on the activated sludge process to the fungi and other organisms occurring there. He noted that a better knowledge of ecological relationships could
lead to a more efficient use of kinetic theory, and thus increase the effectiveness
of the biochemical approach to sewage treatment.
OBJECTIVES
In separate studies the authors of this paper have found that fungi are present
in sewage treatment systems. This has been noted both as a result of plating
samples and watching growth on agar and in liquid culture, and as a result of microscopic examination of sludge floe. If fungi can be detected so readily, are
they not more common than the literature indicates? And if so, do they not contribute to the process of removal of organic matter from sewage? This report is a
start toward finding answers to these questions.   If fungi are part of a population
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