Influence of Inorganic Phosphorus Precipitates
of Aerobic Digestion of Activated Sludge
J. GANCZARCZYK, Professor
M. HAMODA, Doctoral Candidate
H. JAKUBIEC, Graduate Student
Department of Civil Engineering
University of Toronto
Toronto, Ontario
INTRODUCTION
Except for the work discussed in a previous paper (1) the influence of iron and
aluminum salts addition on aerobic digestion of organic sludges has not been studied.
However, quite a number of studies have been carried out on the influence of such additions
on activated sludge process performance.
As early as the late 1930's brought a development of the "Niersverfahren" in Germany
and the Guggenheim process in the U.S.A. (2,3). Both these processes were based generally
on an addition of iron salts to wastewater to its biological treatment, and proved quite
successful in treatment of some mixed or industrial wastewater. Dawson and Jenkins (4)
found that the ferrous ion additions to activated sludge caused a suppression of oxygen
uptake in concentrations of 1,000 mg/l, but had very little effect at levels of 100 mg/l.
Intermediate concentrations of iron produced an increase in oxygen uptake, thus indicating
that iron might be useful in increasing biological activity. Also Carter and McKinney (5)
have shown that a higher rate of metabolism in activated sludge process could be achieved
when a proper balance of iron and other nutrients are made available to the
microorganisms.
In 1973 Anderson and Hammer (6) observed that alum addition to activated sludge
process adversely affected higher life forms, but did not affect BOD removal effects. In the
microbiological studies by Unz and Davis (7) it was also found that the activated sludge
containing aluminum hydroxide showed significantly higher numbers of lipolitic,
gelatinolytic and thiosulfate-oxidizing microorganisms, and possibly fewer nitrite-
oxidizing microorganisms, than the control activated sludge. Amoeboid and ciliated
protozoa, but not flagellates, were found less frequently in the alum-dosed aeration tank
than in the control mixed liquor. Similarly, Lin and Carlson (8) have found that the higher
dosages of alum to activated sludge caused damage to the higher forms of microorganism,
and were capable of removing the filamentous growth from activated sludge systems.
LABORATORY EXPERIMENTS
General
This part of the study consisted of 3 series of experiments described in a separate report
(1). In this paper only a more extended discussion of the results received is being presented.
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