Section Four
WASTE MANAGEMENT
A. BIOLOGICAL ACTIVITY AND
TOXICITY TESTING
19    THIRTY YEARS OF RESPIROMETRY
Robert M. Arthur, President
Bob Arthur, Manager Technology Development
Arthur Technology
Fond du Lac, Wisconsin 45936
INTRODUCTION
In 1964, when the principal author of this paper presented his first paper on the automated
respirometer, it would have been impossible to predict the many applications of this instrument in
activated sludge wastewater treatment. This first paper entitled "Automated BOD Respirometer" was
presented at the I9th Purdue Industrial Waste Conference.' Today both bench and on-line automated
respirometers are widely used with new biobased operation strategies for process control and troubleshooting, for biosolids and compost testing, to separately measure oxygen use in carbonaceous and
nitrogenous oxidation and much more. Many of the developments of the use of respirometers
occurred from 1964 to 1984 and were described in a paper entitled "Twenty Years of Respirometry"
presented at the 39th Purdue Industrial Waste Conference in 1984.2 The paper presented today will
review the developments from 1984 to the present.
BACKGROUND
As pointed out in the 1964 paper, respirometers were used for research work in biological wastewater treatment for many years prior to 1964. The instruments, however, were delicate, limited in
oxygen transfer, used small sample sizes, and were not automated. The instrument described in the
1964 paper overcame all of these drawbacks and produced an instrument that accurately replicated
what takes place biologically in a full scale activated sludge treatment plant. The instrument, however,
was at best an early prototype of what would be subsequently developed. The automated respirometer
has gone through a number of design changes and three models since that early prototype.
It should be recognized that when the words "automated respirometer" are used in this paper they
always refer to the particular respirometer which incorporates an air lift column for mixing, fine
bubble diffusion for high oxygen transfer, and a volumetric transducer. This instrument, known as
the Arthur Respirometer, was developed by the authors of this paper, and all of the test methods and
operation strategies described in this paper were developed using this type of automated respirometer.
Also, in 1964, few plant operators knew what a respirometer was or what it could be used for. In
fact, the only application discussed in the 1964 paper was in measuring a short term BOD, a test now
used by less than five percent of those using the automated respirometer. It took the next thirty years
for the word "respirometer" to become a part of an operator's vocabulary and a part of routine
operation control.
The 1984 paper described some of the physical changes that took place in automated respirometry
in the twenty year period, 1964-1984. It was during this period that instrument design was directed to
producing an instrument which could be used by plant operators perhaps unskilled in laboratory
techniques. The goal was to make the instrument an operation tool used primarily for process control,
not process monitoring.
In addition to discussing instrument development, the 1984 paper also described the metabolic
process and how respirometry can measure the changes in this process. It described respiration graphs
49th Purdue Industrial Waste Conference Proceedings, 1994 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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