The Role of Particulate Substrates in
Biotic Degradation of
Organic Materials
DARRELL L. KING, Assistant Professor
Department of Civil Engineering
University of Missouri
Columbia, Missouri
RAMESHWARD. VERMA, Graduate Student
School of Civil Engineering
Comwell University
Ithaca, New York
INTRODUCTION
Much of what we know about the activity of microbiological communities in
the degradation of organic waste materials is based on studies in which the organic
substrate was glucose present in the dissolved phase. Glucose is not particularly
representative of most organic waste streams and the use of an entirely dissolved
media ignores the early findings of Butterfield (1), Heukelekian (2), ZoBell (3)
and others. Most wastes contain a significant amount of particulate material
which serves as an attachment site for the heterotrophic micorbiota and in many
cases this available surface exerts a marked effect on bacterial activity.
The primary objective of this study was to determine the effects of the physical state of organic media on the metabolism of a complete aerobic community
of microorganisms and on the bacterial portion of that community. The interactions between particulate material and increasing concentrations of dissolved
organic nutrients available to the biota also were considered.
METHODS
The experimental variables used in this study included two biotic communities and two different concentrations of three organic media each with a different physical composition. The study media were composed of varying amounts
of nutrient broth and nutrient agar added to a balanced inorganic solution (4). The
dissolved medium was comprised of nutrient broth and the inorganic solution while
the high particulate medium contained nutrient agar and the inorganic solution.
The low particulate medium contained half as much nutrient broth as the dissolved
medium and half as much nutrient agar as the high particulate solution mixed with
the inorganic micro-nutrient solution. The nutrient broth solution was sterilized
but the nutrient agar could not be autoclaved without destroying its particulate
structure. Preliminary study of nutrient agar solutions indicated that the organisms indigenous to the dry nutrient agar did not exert a significant effect during the 60 hr exposure period used in this study. There was no utilization of pure
agar by the communities used in this study.
The biota used in this study were taken from the aerobic portion of a three-ft
deep laboratory lagoon where the community was comprised of mixed populations
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