36    REMOVAL OF PHENOL IN MIXED SUBSTRATE FORM BY A
FIXED FILM PROCESS
Sila Faghani-Shoja, Graduate Assistant
Bruce A. DeVantier, Assistant Professor
Bill T. Ray, Assistant Professor
Echol E. Cook, Professor
Department of Civil Engineering and Mechanics
Southern Illinois University at Carbondale
Carbondale, Illinois 62901
INTRODUCTION
Wastes bearing significant amounts of phenol present a difficult situation for application of biodegradation methods. Phenol can be removed with biological treatment, however inhibition and toxicity
effects due to phenol can be observed at low concentrations. Several investigators1-2 have found
inhibition effects at phenol concentrations exceeding several hundred mg/L for suspended growth
systems even with acclimation to the phenol. High phenol concentration wastes thus provide a
difficult problem in waste removal, for which dilution becomes a necessity. Dilution can be accomplished by simply maintaining a high enough dilution ratio in a mixed reactor, however tank volumes
can become prohibitively large when the flow is large or the phenol concentration is quite high.
An alternative approach used to provide dilution of toxic and inhibitory waste is mixing with
another non-inhibitory substrate waste stream. A number of researchers3"7 using both synthetic and
natural form wastes, have found this to be a viable alternative. The advantages to this approach
beyond simple dilution appear to be that the presence of the non-inhibitory substance allows higher
growth rates and thus greater cell mass, and that the presence of mixed substrate allows a mixed
culture a diversity of substrate degradation pathways.
Removal of phenol at higher feed concentrations can only be accomplished if the biological system
is acclimated to the presence of phenol and has developed the ability to degrade it. As a result the
system is less tolerant to shock loadings. Use of substrate mixing has been found to mitigate some of
the negative effects of changes in phenol concentration upon a microbial population.1 Still, increasingly higher levels of steady phenol consumption will result in a reduction of growth rate and substrate
removal, so that even without shock loading effects and with an acclimated culture, there is some
point of diminishing return for higher phenol loading. Determination of this "optimum" point
requires a good description of the process of substrate self-inhibition for phenol and inhibition by
phenol of growth utilizing the non-inhibitory substrate.
Fixed film growth has not been the primary choice for biological treatment of phenol bearing
waste. The process does however have the ability to handle moderate shock loads, and is relatively
simple to operate in practice. In a laboratory study setting a fixed film growth process allows
resolution of substrate removal locally, and therefore inhibition can be examined in the context of a
spatially varying concentration. The system described in this study is a bench scale fixed film process
fed with a synthetic waste composed of varying amounts of pure phenol and a simple sugar. The
process will be evaluated with regard to its ability to remove phenol at higher concentrations and with
different levels of non-inhibitory substrate (sugar). Determination of local concentration levels at
which inhibition is detected will also be presented.
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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