United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA-600/S2-83-009 Apr. 1983
Project Summary
Considerations in Granular
Activated Carbon Treatment
of Combined Industrial
Wastewaters
M. D. Piwoni, C. C. Lin, and W. H. Vick
This project was initiated to investi-
gate competitive adsorption
phenomena and their potential impact
on the feasibility of treatment of
combined industrial wastewater
effluents by granular activated carbon
(GAC). Bench-scale laboratory and field
site studies were conducted to evaluate
the extent of competitive adsorption in
GAC columns.
Laboratory studies examined
competitive adsorption of toxic organic
chemicals from simple deionized and
complex combined industrial
wastewater effluent matrices.
Chemicals, selected from a list of those
previously identified as occurring in the
wastewater. were chosen to represent a
broad range of structural and chemical
characteristics. These compounds were
spiked into the test matrices. Results
indicated substantial suppression of
adsorption, and, in some cases, the
occurrence of desorption, of some
components by other components of
the test matrix.
Unspiked wastewater was run
through scaled-up GAC columns in
field studies. Fractionation of the
columns and analysis of the fractions
revealed a transport pattern through the
column that, in general, reflected the
observations made during the
laboratory studies using spiked
matrices.
This Project Summary was developed
by EPA's Robert S. Kerr Environmental
Research Laboratory, Ada. OK, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
GAC column treatment has been under
consideration by the U.S. Environmental
Protection Agency (EPA) Effluent Guide-
lines Division as a feasible alternative for
removing low levels of toxic organic
compounds from complex industrial waste-
water effluents. Although the effective-
ness of GAC treatment has been clearly
demonstrated in drinking water applica-
tions, questions remain as to the appli-
cation of this methodology to considerably
more complex matrices. Competition for
adsorption sites between toxic organic
components and other organics in the
matrix could reduce the removal
efficiency for compounds of concern. The
result would be premature column break-
through, and, consequently, more
frequent carbon regeneration.
This study examined competitive
adsorption and its significance in treating
complex wastewaters. Bench-scale
laboratory and field studies were
conducted to evaluate the phenomena
and to determine the suitability of con-
ventional parameters for monitoring
column breakthrough.
Conclusions
1. Competition for adsorption sites on
the carbon surface results in
certain organic solutes being
retained on the column at the
expense of other organics. In some
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cases, low affinity organics were
desorbed from the carbon resulting
in effluent concentrations in
excess of influent levels.
2. The success of certain-organics in
competing for adsorption sites is
related to their aqueous solubility
and their relative column influent
concentrations. Low solubility
components showed the highest
affinity for the carbon although
lower affinity compounds at higher
relative influent concentrations
are more effective competitors.
3. The presence of the nondescript
organic matrix in the wastewater
substantially lowered carbon
capacity for spiked components
when the latter were added to the
wastewater at relatively low(5/ym)
concentrations. At higher (100/urn)
concentrations, little effect on
carbon capacity, compared to deion-
ized water systems, was observed.
4. The shape of the breakthrough
curves for the organics studied
varied considerably. Some
components exhibited a sharp
increase in column effluent con-
centration after initial appearance
in the effluents while, at the other
end of the spectrum, other
components increased slowly in
concentration as the column run
progressed. Such diversity in
column breakthrough patterns
complicates the task of column
monitoring.
5. The breakthrough patterns for
chemical oxygen demand (COD)
and total organic carbon (TOC)
were similar, showing a rapid
initial breakthrough to greater than
50 percent followed by a slow
climb to total breakthrough.
6. The column breakthrough points of
the spiked organics were not
reflected by any inflections in the
COD or TOC curves. Under these
study conditions, TOC and COD
reflected changes in the total
organic content of the effluent,
thus they were unresponsive to
changes in specific compound
concentrations.
7. Movement of components of
interest within carbon columns
receiving unspiked wastewater
was generally in accord with
predictions based on the results of
the spiked components studies.
8. The complexity of adsorption from
combined industrial wastewater
effluents makes modelling of the
system for specific component
removal difficult if not currently
impossible.
Recommendations
1. The competitive adsorption
patterns observed in this study
need to be generalized to all types
of organic compounds requiring
removal from wastewaters. Future
studies should address structural
and chemical property correlations
to carbon column capacity as well
as the magnitude of effects of
influent concentration differences.
2. The magnitude of the effect of the
nondescript background organic
materials present in industrial
effluents must be better defined.
3. Column monitoring when removal
of specific toxicant organics is
required will not be possible using
TOC or COD. Unless more refined
surrogate monitoring techniques
are developed, monitoring of
specific components by gas
chromatography will likely be
required.
The EPA author M. D. Piwoni is with the Robert S. Kerr Environmental Research
Laboratory, Ada, OK 74820; C. C. Lin is with the University of Texas, Dallas, TX
75080, and; W. H. Vick is with Science Applications, Inc., LaJolla, CA 92038.
Fred M. Pfeffer is the EPA Project Officer (see below).
The complete report, entitled "Considerations in Granular Activated Carbon
Treatment of Combined Industrial Wastewaters," (Order No. PB 83-164 475;
Cost: $ 17.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
ftU.S. Government Printing Office: 1983-659-017/7026
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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