A Model for the Powdered
Activated Carbon-Activated Sludge
Treatment System
BRIAN P. FLYNN, Chemical Engineer
E.I. DuPont de Nemours Co., Inc.
Deepwater, New Jersey 08023
INTRODUCTION
Because of the continuing effort to upgrade the quality of our nation's waterways, it
sometimes becomes necessary for a point source of pollution to be cleansed beyond the
capability of a conventional activated sludge system. Just such a case occurred at Du Pont's
Chambers Works location, situated on the Delaware River estuary at Deepwater, N.J. This
plant is a large multiproduct plant (approximately 2,000 processes) engaging in petroleum
chemical, dye, organic intermediate, elastomeric, and fluorocarbon manufacture. The
wastewater produced from these processes is highly acidic and contains heavy metals,
dissolved dyes, and a myriad of organic compounds. Laboratory work on the wastewater
revealed it to be treatable biologically, but treatment was unstable and insufficiently
effective to meet proposed effluent standards (1).
Consequently, alternative methods of treatment were considered. A physical-chemical
system using a powdered activated carbon slurry contact stage was tried in the laboratory,
but was also found to be inadequate (2). Since the wastewater was then perceived to contain
substantial quantities of biodegradable and adsorbable materials, the removal of either
being inadequate to meet standards, it was decided to attempt to treat the wastewater using
a combination of the two processes: powdered carbon addition to an activated sludge
system. This was successful both in the lab (3) and pilot plant studies (4) performed, with
substantial improvements in effluent BOD, COD, TOC, color and fish toxicity occurring.
The process has been applied to other locations, both domestic and industrial at the plant
scale on a temporary (5, 6) and continuing basis (7). A 30 million gallon per day powdered
activated carbon addition to activated sludge (PACT process) treatment facility is now
under construction at DuPont's Chambers Works, and will be ready for operation in 1976.
Figure 1 illustrates the process. Primary clarified effluent is fed to a completely mixed
activated sludge reactor with fresh (or regenerated) powdered activated carbon. The carbon
is used to adsorb some materials while the bacteria biochemically degrade others. The
carbon and bacteria form a dark, well-flocculated sludge which settles well in the final
clarifier where overflow effluent of tertiary quality is obtained. The system is capable of
being run on the conventional sludge concept by wasting sludge either from the aerator or
clarifier underflow. The wasted sludge can be regenerated to recover reusable powdered
activated carbon.
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