Instrumentation for Research on
Biological Processes
CHARLES W. CRAWFORD, Environmental Engineer
Moore Products Company
Knoxville, Tennessee
KAWI KAMBHU, Graduate Student
JOHN F. ANDREWS,  Professor
Environmental Systems Engineering Department
Clemson University
Clemson, South Carolina
INTRODUCTION
Many of the limitations of previous studies on biological processes used for
waste treatment have been due to the many variables involved, time requirements
for bringing the microbial cultures to steady state, and a lack of control of some
of the more important variables. Most investigators, because of time limitations,
have used only one or two reactors and studied only one or two variables. Consequently, these investigators have frequently been unable to obtain sufficient data
to detect significant interactions between variables. Investigators working with
natural substrates (domestic sewage, industrial wastes) have experienced difficulties because of a lack of knowledge of the composition of the substrates and
changes in character of these substrates with respect to time. Correlation of results from different laboratories has been difficult because of the many different
substrates and experimental procedures used. It appears to the authors tnat significant advances could be made in the solution of these problems by using appropriate instrumentation to accomplish the following: 1) Simultaneous operation of
many reactors thus permitting investigation of more variables in the same laboratory under controlled conditions; 2) Automatic control of important variables by
use of appropriate sensors and control instrumentation; 3) Analysis of substrate and
reaction products by automated wet chemical analyzers, gas chromatographs,
etc.; 4) Automatic collection and formating of data for direct entry into the dig-
tal computer by using a data acquisition system; and 5) Use of the digital computer to reduce data for analysis.
Incorporation of these features into a biological process is shown in Figure 1.
As indicated, several variations of the system are possible. This type of system
would be especially useful in investigating the dynamics of biological processes.
Figure 2 shows a typical aerobic/anaerobic reactor with the associated inputs and
outputs which are of interest. Online sensors and controls are available for many
of these with detailed information being available in the fermentation and instrumentation literature. A photograph of a typical reactor, for which the instrumentation was designed, is given in Figure 3. These are continuous-flow, complete mixing reactors with a liquid volume of 10 liters. Each reactor is equipped
with a variable speed input pump, variable speed turbine stirrer, electronic liquid level controller, air injector, and effluent measuring device. The reactors
are gas-tight so that they can be used for both aerobic and anaerobic investigations.
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