The Application of Oxidation-
Reduction Potential to Biological
Waste Treatment Process Control
W.   WESLEY   ECKENFELDER,   JR.
President, Eckenfelder Associates, Inc.
Ridgewood, New Jersey
JOHN  W.   HOOD
Superintendent of Sewage Treatment
. Ridgewood, New Jersey
This paper represents a report of progress on the investigation of
analytical and control methods to the design and operation of industrial
waste treatment processes, particularly as they relate themselves to
biological treatment. Effective process control should be based upon
analytical methods which are related to the functional operation of
the process and which are simple to perform. In many waste treatment
processes, the O-R Potential may be readily employed as a means of
process control to attain the maximum process efficiency. Considerable
work has been done on the application of the O-R Potential to sewage
treatment process control.3 This work is an extension of these investi¬
gations to the application of the O-R Potential to waste treatment
process control. In many cases, O-R Potential studies may suggest new
approaches to problems of biological oxidation and reduction in process
operation and provide a basis for further research.
The O-R Potential represents the electrical pressure existing in a
liquid as a result of the respective concentrations of oxidant and
reductant present in a substrate. The O-R Potential relationship in
industrial waste treatment is shown in Figure 1. In this respect O-R
Potential is essentially an intensity factor and has been analogously
compared to temperature by several investigators.7 Oxidation may
be defined as a substance taking up negative charges. The potential
difference is determined by the ratio of oxidant to reductant and the
hydrogen ion concentration. While it is not a quantitative measure of
these compounds, it may be assumed to be the relative proportions in
which they exist. The conditions affecting the potential of a biological
medium and the rate of change of potential are: (a) the kind of organism
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