APPLICATION OF CARRIER/ACTIVATED SLUDGE PROCESS
FOR TREATMENT OF PHENOLIC WASTEWATER
Yongsen Lu, Visiting Scholar
J. J. Ganczarczyk, Professor
Department of Civil Engineering
University of Toronto
Toronto, Canada, M5S 1A4
INTRODUCTION
There are many unanswered questions associated with activated sludge treatment of wastewater in
the presence of solid particles which may affect the process in many different ways. Surface of these
particles may be a supporting medium for some microorganisms, and it is possible that the growth
phase associated with this type of growth may be more physiologically active. These carrier particles
may also possess different sorption characteristics which may differently affect the process kinetics by
increasing local concentration of the metabolic substrates and by storing the excess of the substrates in
cases of shock loading.
To get some better insight into the above situations, extensive laboratory experiments were carried
out on activated sludge treatment of simulated phenolic effluents in the presence of two biomass carriers which differed substantially in their sorption capacity, but both were characterized by a rough
surface, suitable for microbial growth, and by physical strength which prevented any meaningful
changes in their size due to the abrasion. As such carriers, activated carbon and coke were selected,
and the chosen size of their particles was much larger than in the PAC activated sludge process to emphasize the role of the biological growth supporting medium and to make possible an application of
microphotography to study the developed systems (Figure 1). This modification of the activated
sludge process was called the "carrier/activated sludge process."
GENERAL SYSTEMATICS OF BIOLOGICAL SYSTEMS
From a purely physical point-of-view, the biological treatment of wastewater can be divided into
systems operating with the growth of biomass in the form of a suspension or as an attached growth of
a biofilm on a supporting medium (carrier). The suspended growth, in turn, can be divided into
dispersed growth forms, like in aerated lagoons, and flocculating forms, like in many modifications of
the activated sludge process. Also, the biofilm form can vary broadly depending on the type, structure, and size of the supporting media (carrier) surface, among other things (Figure 2).
It appears that on the basis of this general systematics, it is possible to formulate a third group of
biological treatment systems which would be characterized with some features of suspended growth
systems and some other features of supported growth systems, or would contain both forms of the
biological growth. This group of biological treatment systems can be called hybrid growth forms and
will cover such diverse treatment systems as the studied carrier/activated sludge system, fluidized
biological beds, PAC activated sludge and some chemical/biological treatment systems.
In the fluidized beds, the biological growth support media/carrier particles are covered by a
biofilm but at the same time are "suspended" in a fluidized column. In the PAC activated sludge
system, the very small particles of powdered activated carbon are incorporated in a flocculated and
suspended biological growth, but they may also play a role of support for some biological growth
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