SOLUBLE COD REMOVAL IN A
FLUIDIZED-BED BIOLOGICAL REACTOR
John E. Butts, Project Engineer
Envirosphere Company
New York, New York
John E. La Padula, Project Engineer
Hydroscience, Inc.
Westwood, New Jersey 07675
Karen A. Sanderson, Project Manager
Lawler, Matusky, & SkeUy Engineers
Tappan, New York 10983
INTRODUCTION
Biological waste treatment systems which stabilize organic wastes depend on a heterotrophic bacterial population to utilize the carbon source for ceUular respiration and synthesis.
This paper describes a novel modification of this process which provides a vast biological surface area, and thereby increases the amount of contaminants that can be removed in a given
volume of reactor.
This process employs a fluidized-bed principle utilizing sand grains as a support medium
for biological growth. A fluid containing a contaminant is passed upward through a cylindrical reactor at a sufficient velocity to cause the fluidization of the entire medium. During
transport, the heterotrophic organisms covering the sand grains utilize pure oxygen to reduce
the wastewater's organic components to carbon dioxide and water and produce new ceUs.
Fluidization aUows for a better contact between the waste to be treated and the biological
mass in the system. The resulting liquid detention time is typicaUy one to two orders of magnitude less than that of other treatment processes because of the capabUity of this system to
maintain a vast biological population. In addition, increased flow rates can easUy be used
with insignificant head losses in a fluidlzed bed.
The utUization of the upflow, fluidized-bed biological reactor for carbon removal is a
direct extension of the denitrification bench-scale work performed by Beer, Jeris and Mueller
[ 1] and the plant study reported by Jeris and Owens [2]. Jeris and Owens [2] reported consistent 99% nitrate removals at flux rates as high as 24 gpm/ft2 (1 m/min), detention times
of 6.5 min, and loading rates of approximately 335 lb of nitrate/1000 ft3 (152 kg/28 m3) of
reactor volume.
Because of this success in the area of denitrification, the authors have extended the applications of the fluidized biological bed to the removal of organic carbon.
THEORY
Any biological waste treatment system is in essence a continuous fermentation process.
While the overall reactions carried out may be quite different (e.g., anaerobic vs aerobic conditions), the processes of microbial growth and energy utUization are simUar [3].  Many attempts have been made to apply established rules of continuous fermentations to the special
case of waste purification [4-7]. The "established rules," however, have their base in certain
ceUular biochemical reactions. This fact was elucidated by researchers Drs. Michaelis and
Menton [8] upon the formulation of their enzyme kinetic theory.
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