61    PACKED-ENTRAPPED-MIXED MICROBIAL CELL PROCESS
FOR REMOVAL OF PHENOL AND ITS COMPOUNDS
P. Y. Yang, Professor
T. S. See, Graduate Research Assistant
Department of Agricultural Engineering
University of Hawaii at Manoa
Honolulu, HI 96822
INTRODUCTION
The biodegradation of hazardous wastes by conventional-biological treatment systems has been
reviewed by Grady.' It was observed that most of the conventional-biological systems were capable of
degrading toxic-organic materials. The removal of toxic pollutants by primary treatment, chemical
clarification, trickling filter, activated sludge, aerated lagoon, and facultative lagoon have been
evaluated by Hannah, et al.2 It was concluded that the activated sludge process provided the best
removal of conventional pollutants as well as toxic priority pollutants. Regarding the response of
phenol-acclimated activated sludge process to quantitative shock loading, it was concluded by Rozich
and Gaudy3 that design of a slow specific growth rates (higher solid retention time, SRT) are essential
for systems that undergo shock loadings. Similarly, anaerobic suspended cell systems have potential to
degrade toxic organics if acclimation of microbial cells to the organics and longer SRT's are
provided.4
Immobilized microbial cell systems have been increasingly used in the bioconversion processes,
including the production of food, beverages, pharmaceuticals, macromolecules such as organic acids
and amino acids, other industrial chemicals, and fuels such as alcohol, methane and hydrogen.
Biological wastewater treatment is within the category of bioconversion processes. Immobilized cell
systems, such as biofilms, have been widely used for decontamination and methane production. This
type of process is particularly suitable for the treatment of non-conventional or toxic wastewater,
which requires a longer cell or solid residence time. Under conditions that would have caused washout
of the free cells, immobilized cells could still be retained in the reactor;5 i.e., SRT could be increased
by immobilization of cells.
Phenol and phenolic compounds have been considered as toxic organics and tend to be prevalent in
the industrial wastewater streams. Studies on the application of immobilized pure culture and systems
for synthetic phenolic wastewater treatment were reported.6,7,8,9,10 The application of immobilized
pure culture characteristic in the actual wastewater treatment process. Application of immobilized
(entrapped) mixed culture cell for phenol and phenol related compounds was previously
reported.11,12,13 These compounds could be successfully treated. However, the effectiveness of
absorbed and entrapped mixed microbial cells for the treatment of phenol was not thoroughly
compared14 and required further investigation.
Protection of groundwater and clean-up for hazardous wastes/wastewater including pesticide
wastes and pesticide contaminated water have become two of the major concerns of the USEPA and
the states; certainly Hawaii is no exception.
Carbaryl (phenol related compound) is the most extensively used carbamate pesticide.15 It has been
found in groundwater and is on the EPA National Groundwater Survey List.16 The detoxification of
carbaryl using pure culture isolated from soil to describe the differences in each of the decomposition
process was investigated.17 It was concluded that the mixed cultures of soil microbes were more
effective in transforming carbaryl than in pure cultures. Thus, the packed-entrapped-mixed microbial
cell process was proposed to investigate its removal. This treatment process attempts to provide an
effective degradation of phenol and its related compound (such as carbaryl) from water and wastewater systems.
45lh Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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