Toxicity of Copper to Activated Sludge
K. C. AYERS, Sanitary Engineer
The Mead Corporation
Chillicothe, Ohio
K. S. SHUMATE, Assistant Professor of Civil Engineering
G. P. HANNA, Associate Professor of Civil Engineering
The Ohio State University
Columbus, Ohio
INTRODUCTION
The activated-sludge process as described by Ardern and Lockett in 1914
offered a degree of sewage-treatment not before possible. Continued developments
since then have improved this biological treatment process to the point wnere
operational efficiency can be predictably and consistently kept at a high level,
with due regard and proper compensation for certain environmental, physical, and
chemical conditions. The very fact that the primary agents causing degradation
are bacteria means, however, that the process can be and is upset to varying degrees by anything toxic to the bacterial community.
It has long been recognized that heavy metals can cause deleterious effects
to biological treatment efficiency and many investigators have reported on these
effects, usually as monitored by some external parameter such as reduction in
BOD removal. This paper will not attempt to list the many researchers who have
worked in this area. However, it can be stated that while these concentrations of
the heavy metals causing serious retardation of the bacterial action are fairly established and documented, few investigators have attempted to define the mechanisms causing retardation, or to suggest means of alleviating or preventing deleterious effects when the influent sewage contains toxic concentrations of one or
more of these metals.
The purpose of this paper is to summarize studies carried out at The Ohio
State University in which attempts were made to investigate the actual mechanism causing partial failure of the activated-sludge process due to shock loadings
of copper.
WORK OF PREVIOUS INVESTIGATORS
Previous studies (1,2) have indicated that of the metal ions commonly found
in industrial wastes, copper appears to be one of the most toxic to biological
treatment processes.
Barth et al (3) verified the high toxicity of copper as compared to chromium,
nickel and zinc.   They found that biological processes are more sensitive to copper than to the other ions, both with respect to the concentrations which will give
a significant reduction in aerobic treatment efficiency when fed continuously and
when fed as a four-hr slug dose.
Directo(2) investigated the reactions of the activated sludge process to shock
dosages of copper. Specifically, he studied the effects of copper on sludges having no previous history of copper, and employed a six-hr copper dosage at levels
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