TRUTH OR CONSEQUENCES:  BIOLOGICAL FOULING AND OTHER
CONSIDERATIONS IN THE POWDERED ACTIVATED CARBON-
ACTIVATED SLUDGE SYSTEM
Brian P. Flynn, Process Engineer
Francis L. Robertaccio, Senior Process Engineer
E. I. du Pont de Nemours & Company, Inc.
Deepwater, New Jersey 08023
Louis T. Barry, Senior Research Supervisor
Nichols Engineering and Research Corporation
Belle Mead, New Jersey 08502
INTRODUCTION
The direct addition of powdered activated carbon to a biological reactor is a relatively
new concept in wastewater treatment [ 1 ].   As with any new concept, there sometimes
appears obvious contradiction in interpretation of different sets of experimental data.
In the absence of experimental data, opinions based on hypotheses or even conjecture
lead to scepticism or exaggeration.   Quite often, differences in data interpretation, or
opinion in the absence of data, are largely due to the lack of a common understanding
of terms and their inconsistent application.   The purposes of this chapter are:   (a) to
define some terms used to interpret data for this relatively new process with the hope
that they will become commonly understood and (b) to present sound experimental data
that explore the significance of these terms.
EXPLANATION OF PROCESS
Powdered carbon addition to a biological reactor is often referred to as the du Pont
PACT process (U.S. Patent 3,904,518).   The process is illustrated in a general manner in
Figure 1.
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Figure 1.   General illustration of the du Pont
PACT process (U.S. Patent 3,904,518).
FASTI SLIHGE
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The process is uncomplicated and claims the following advantages [ 1-4]:
• Improves effluent water quality beyond the capacilities of conventional biological
treatment in a cost-effective manner;
• enhances treatability of wastewaters that inhibit or toxify biological treatment systems;
• expands the hydraulic capacity of existing treatment plants without redundant expansion of unit processes;
• provides uniform plant operation and effluent quality, especially during periods of
varying organic loads;
• minimizes operating problems inherent in biological treatment such as aerator and
effluent foaming, bulking sludge, difficult secondary solids handling and disposal;
• eliminates ultimate disposal of secondary solids in a process to recover and regenerate
carbon for reuse;
• is compatible with existing treatment plant operations.
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