Cation Toxicity and
Stimulation in Anaerobic Waste Treatment
II.   Daily Feed Studies
IRWIN J. KUGELMAN, Assistant Professor of Civil Engineering
New York University
New York, New York
PERRY L. McCARTY, Associate Professor of Civil Engineering
Stanford University
Stanford, California
INTRODUCTION
During the past 20 years research into the fundamental principles underlying
waste water treatment has increased at a rapid rate. One fundamental principle
which this research has brought forth is that optimum efficiency in a biological
waste treatment system can be attained only when the microorganisms functioning
in the process are provided with an optimum environment. Studies by biologists
over the last century have indicated the fundamental role played by cations in the
metabolic processes of all organisms. Therefore, it is evident that control of the
ionic environment must be practiced in order to insure optimum performance of
biological waste treatment systems.
Until recently, however, the importance of cation effects has been overlooked
in the design of anaerobic waste treatment systems. The neglect of cation effects
has resulted primarily for three reasons: 1) In the past most anaerobic systems have
been called upon to treat domestic sewage sludge. In most cases sewage sludge is
essentially a biological well balanced ionic medium. 2) The anaerobic digestion
systems designed for the treatment of domestic sewage sludge were operated at
rather low organic loadings, and long retention times. Thus deviations from the
optimum ionic environment were not critical. 3) Treatment difficulties which
resulted from an ionic imbalance were ascribed to improper levels of other more
easily recognizable environmental factors such as pH and volatile acids.
In the future, biological waste treatment systems will be called upon more
to handle wastes of an entirely different nature from that of domestic sewage
sludge. In addition, in order to make the process as economical as possible, much
higher organic loading rates and shorter retention times will be desirable. Under
these new conditions consideration of cation effects will undoubtedly become more
critical for the design and operation of anaerobic waste treatment systems.
In order to prepare for these future conditions, a basic investigation of cation
effects in the anaerobic waste treatment process was undertaken. The first phase
of this investigation dealt with the slug addition of cations to active cultures of
acetate fermenting methane bacteria. The results of the first phase were reported
previously (1). The second phase which is reported in this paper deals with cation
effects under daily feed conditions, as would apply more closely to field conditions.
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