An Experimental Valuation of the
Intra-Particle Resistance in Substrate
Transfer to Suspended Zoogloeal  Particles
C. ROBERT BAILLOD, Assistant Professor
Department of Civil Engineering
Michigan Technological University
Houghton, Michigan
W. C. BOYLE, Associate Professor
Department of Civil Engineering
University of Wisconsin
Madison, Wisconsin
INTRODUCTION
Wastewater contains particulate and soluble organic materials suspended or
dissolved in the carriage water. In a treatment system, these constituents may be
removed by a myriad of mechanisms which may be broadly classified as: 1) Gravity
sedimentation, 2) Physical sorption onto a solid surface, and 3) Chemical reaction at
an active surface, or chemi-sorption. The first two mechanisms would predominate
for the removal of particulate materials, whereas the third mechanism would be of
primary importance for the removal of soluble materials. In both sorption mechanisms, however, the organic mass must be transferred to the solid surface before any
physical or chemical adsorption can take place. When the solid surface consists of a
wet, permeable material such as a biological slime, soluble materials may be transferred by molecular diffusion to active sites in the interior of the permeable material.
It is possible that the rate of these mass transfer steps may limit the overall rate of the
removal reaction. The purpose of this paper is to evaluate experimentally the extent
to which the mass transfer process limits the rate at which a soluble organic substrate
is removed from solution by suspended particles of bacterial floe.
LITERATURE REVIEW
In recent years, a significant amount of sanitary engineering research has been
directed toward developing an understanding of the transfer process operative within
waste treatment systems. Although these studies have been primarily concerned with
mass transfer of oxygen, some attention has been paid to mass transfer of organic
substances to fixed films. Wuhrmann (1) applied the theoretical analysis of Gerard
(2) in order to estimate the extent of oxygen diffusion through biological floe.
Noting that wastewater could be considered as very dilute fermentation media, with
the concentrations of the more important substrates being extremely low and
frequently not higher than the oxygen concentration normally carried, he estimated
the glucose concentration at which glucose uptake might become a diffusion controlled reaction to be approximately six times the limiting oxygen concentration of
the floe particle.
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