&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research -
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-065 August 1982
Project Summary
Powdered Activated Carbon
Adsorption Isotherms for
Selected Tannery Effluents
J. Vuceta and K. V. LaConde
This project was initiated to gain a
better understanding of powdered
activated carbon (PAC) addition to
secondary treatment of tannery efflu-
ents. The purpose of this research was
to obtain sufficient bench-scale data
to select PACs for full-scale testing.
Adsorption isotherms were developed
for COO, BOD, TOC, total and specific
phenols, oil and grease, and total
chromium.
Initially, two raw untreated tanning
effluents, representing two different
tanning subcategories, as classified by
EPA, were tested using six individual
PACs. Three of these carbons were
thus excluded from further testing.
The three remaining carbons (i.e., ICI-
HDC, ICI-HDH, and Nuchar SA-15)
were subsequently tested for the
above parameters on eight additional
tanning effluents (representing a total
of six tanning subcategories).
Final comparisons between the in-
dividual carbons were performed in
terms of their removal efficiencies (at
a dose of 0.3 g/L) and ultimate capac-
ities, using Freundlich adsorption iso-
therms. COD, BOD, and TH A removal
efficiencies of any of the three carbons
at a dose of 0.3 g/L were found to be
up to 30 percent for Tanneries 1,2,4,
5,6,7,8, and 9, while PAC treatment
of effluents from Tanneries 0 and 3
resulted in more than 30 percent
removal of COD and THA.
In terms of ultimate surface capac-
ities for COD, BOD, and THA within
Tanneries 0, 2,3, 7, and 9. all three
carbons exhibited differences equal to
or less than one order of magnitude;
for Tanneries 1, 4, 5, 6, and 8,
differences between ultimate capac-
ities were found to be greater than one
order of magnitude.
The presence and removal by PAC
sorption of the four specific chloro-
phenols considered in these investiga-
tions were examined for Tannery 5
and 7 effluents only.
Comparison of the wastewater char-
acteristics of the four pairs of tanneries
within the same subcategory indicated
no similarities in the concentration of
wastewater constituents. Analysis of
the adsorption data indicated that the
PACs have limited ability to bind COD,
BOD, TOC, THA, chromium, and oil
and grease in tannery effluents. Fur-
thermore, there was no apparent cor-
relation between final effluent charac-
teristics and the nature of the tanning
operations.
Since data on the removal of specific
phenols were insufficient to draw any
general conclusions, the relationship
between PAC dosage and specific
phenols merits further investigation.
However, any future related PAC
research efforts should be conducted
on an effluent-by-effluent basis.
This report was submitted in fulfill-
ment of Contract Nos. 68-03-2678,
WD 7, and 68-03-3028, WA 11. by
SCS Engineers under sponsorship of
the U.S. Environmental Protection
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Agency. This report covers the period
from April 9, 1979, to December 8,
1981, and work was completed in
October 1980.
This Project Summary was devel-
oped by EPA's Industrial Environmen-
tal Research Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Background
Tanneries are pollution-intensive in-
dustrial complexes which generate large
volumes of highly concentrated waste-
water. In implementing Best Available
Technology Economically Achievable
(BATEA) and Best Conventional Pollu-
tant Control Technology (BCT) limita-
tions, the U.S. Environmental Protection
Agency (EPA) has recommended the
use of powdered activated carbon (PAC)
to enhance secondary biological treat-
ment. Several studies have shown that
when PAC is added to aeration basins,
the carbon and microorganisms act
synergistically to remove pollutants
more effectively than conventional sec-
ondary biological treatment systems.
The addition of PAC to activated sludge
systems has reduced aerator and efflu-
ent foam, improved solids settling, in-
creased effective digester capacity,
adsorbed color, and increased the re-
moval of COD, BOD, TOC, and selected
organics.
Under a separate EPA grant (Grant
No. S804504), the A. C. Lawrence
Company was to evaluate the effective-
ness of adding PAC to its activated
sludge system in Winchester, New
Hampshire. This project was funded by
the Effluent Guidelines Division (EGD)
to gain a better understanding of PAC
usage for full-scale testing. The devel-
opment of adsorption isotherms was
initiated under this grant to obtain a
sufficient data base from which to select
PACs for the full-scale testing program.
While the results of these first isotherm
tests are covered in a separate report,
carbon selection, analytical parameters,
and much of the testing protocol were
developed during the early stages of the
grant. The thrust of the project covered
by this report, therefore, was a continua-
tion and an expansion of the work
started under the A. C. Lawrence grant.
In addition, the results of this work were
subsequently used to select PACs for
the full-scale tests in Winchester.
The objectives of this project were:
• To develop adsorption isotherms
for six individual PACs on two raw,
untreated tanning effluents. Par-
ameters to be investigated in-
cluded COD, BOD5, TOC, total and
specific phenols, oil and grease,
and total chromium.
• To select the three best PACs from
the above and develop adsorption
isotherms on eight additional tan-
ning effluents for the parameters
shown.
• Based on the adsorption isotherm
results, to recommend specific
PACs for full-scale testing by the
A. C. Lawrence Company.
In the full project report, the conclu-
sions of this study and the resulting
recommendations are given in Sections
2 and 3. Section 4 outlines sampling,
analytical, and experimental procedures
employed during this study, with more
details contained in Appendix B. Section
4 also contains a brief description of
adsorption isotherm calculations. The
results of this research are presented
and interpreted in the form of adsorption
isotherms in Section 5. More details on
experimental data are given in Appendix
A. Costs of PAC addition to biological
treatment of tannery effluents, estima-
ted from the results discussed in Section
5, are given in Section 6. Finally, for a
better understanding of the processes
which generate the wastes ultimately
sampled. Appendix C provides a brief
description of the subcategories within
the tanning industry.
Conclusions
This section presents the conclusions
of this study, involving the removal of
different constituents from effluents
generated by 10 tanneries, using the
following six activated carbons: ICI-HDC,
ICI-HDH, Nuchar SA-15, Norit FQA,
Westates WO-841, and Amoco PX-21.
For each tannery effluent, all of the
carbons were examined in terms of their
respective ultimate capacities and per-
cent removals of each constituent at
different carbon doses. In the delinea-
tion that follows, the term "ultimate
capacity" implies the theoretical weight
of the constituent adsorbed per unit
weight of carbon when the carbon is in
equilibrium with the surrounding solu-
tion. Ultimate capacities were deter-
mined by the lines of best fit through
each data set by performing a least
squares linear regression using loga-
rithms of the data points. Percent ad-
sorption at different carbon doses was
then calculated from the lines of best fit
by using a computer program based on
the method of flexible polyhedron
search.
PAC
Initial tests were performed with six
activated carbons on Tanneries 0 and 4.
The results revealed that Westates WO-
841 and Norit FQA yield low removal
efficiencies. These carbons were thus
excluded from further testing. Although
Amoco PX-21 is'very efficient m the
treatment of tannery effluents, it was
excluded from further testing, because
it is not commercially available. Conse-
quently, effluents from the other tan-
neries were treated with only three
carbons: ICI-HDC, ICI-HDH, and Nuchar
SA-15.
COD. BOD, and THA
The removal efficiencies of any of the
three carbons at a dose of 0.3 g/L are
illustrated. Removal of COD, BOD, and
THA at the above carbon dose (regard-
less of carbon type) was found to be up
to 30 percent from Tanneries 1, 2,4, 5,
6, 7, 8, and 9, while PAC treatment of
effluents from Tanneries 0 and 3 re-
sulted in more than 30 percent removal
of COD and THA.
Numerical values for COD removal
efficiencies at a 0.3 g/L carbon dose
were found to be in the following ranges:
ICI-HDH, 3 to 17 percent; ICI-HDC, 4 to
18 percent; Nuchar SA-15, 7 to 36
percent. For 7 out of 10 cases (Tanneries
1, 2, 3, 5, 6, 7, 8, and 9), all three
carbons yielded results that differed
only up to 10 percent; for Tanneries 0,4,
and 8, however, Nuchar SA-15 accom-
plished removals that were 14 to 26
percent higher than those with 1C)
carbons.
In the case of BOD, all three carbons
exhibited similar removal percentages
(i.e., within a 10 percent range of
difference) in 5 out of 10 cases (Tan-
neries 1,3,4,7, and 9). For Tanneries 2,
5, 6, and 8, Nuchar SA-15 yielded 10 to
24 percent higher BOD removals than
those accomplished using ICI carbons,
while for Tannery 0, ICI carbons yielded
13 to 18 percent better removals than
those with Nuchar SA-15.
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With regard to THA removals, all three
carbons yielded comparable results
(equal to or less than 5 percent differ-
ence) in 8 out of 10 cases (Tanneries 1,
2, 4, 5, 6, 7, 8, and 9). For Tannery 0,
Nuchar SA-15 was apparently more
effective, removing 11 to 19 percent
more THA compounds than ICI carbons.
In the case of Tannery 3, however, ICI
carbons yielded 28 to 33 percent better
THA removals than Nuchar SA-15.
In terms of ultimate surface capacities,
the following general observations can
be made. The highest ultimate capacity
for COD removal in Tannery 0 effluent
was exhibited by Nuchar SA-15 (0.8 g
COD/g carbon), followed by ICI-HDC
(0.4 g COD/g carbon), and ICI-HDH
(0.15 g COD/g carbon). The ultimate
capacities of these carbons for BOD
removal were found to be in the follow-
ing descending order: ICI-HDC, ICI-HDH,
and Nuchar SA-15, ranging from approx-
imately 0.3 to 0.4 g BOD/g carbon.
Those for THA removal were higher for
Nuchar SA-15 and ICI-HDC (0.08 g
THA/g carbon) than for ICI-HDH (0.04 g
THA/g carbon).
For Tannery 1 effluent, ultimate capac-
ities of all three carbons for the removal
of COD were found to range from
approximately 0.9 to 1.3 g COD/g
carbon, while those for BOD ranged
from 0.75 to 1 g BOD/g carbon. Ultimate
capacities for the removal of THA com-
pounds, however, were estimated to be
lower, ranging from 0.02 to 0.06 g
THA/g carbon.
For Tannery 2 effluent, the ICI carbons
were found to be more efficient for COD
removal than Nuchar SA-15, with ulti-
mate capacities of approximately 0.6
and 0.45 g COD/g carbon, respectively.
In terms of BOD removal, however, ICI
carbons were found to be ineffective for
this particular effluent, with ultimate
capacities ranging from 0.04 to 0.05 g
BOD/g carbon; Nuchar SA-15 exhibited
an ultimate capacity of 0.4 g BOD/g
carbon. Ultimate capacities of all three
carbons for THA removal were estimated
to be approximately 0.04 to 0.05 g
THA/g carbon.
In the treatment of Tannery 3 effluent,
Nuchar SA-15 exhibited the highest
ultimate COD removals (1.2 g COD/g
carbon), while those of both ICI carbons
were estimated to be approximately 0.6
g COD/g carbon. For BOD removal from
this effluent, the experimental data
indicated the following ultimate capac-
ities: ICI-HDC, 0.09; ICI-HDH, 0.04; and
Nuchar SA-15, 0.16 g BOD/g carbon.
Ultimate capacities of all three carbons
for THA removal were approximately
0.3 to 0.4 g THA/g carbon.
At Tannery 4, the highest ultimate
capacity for the removal of COD was
exhibited by Nuchar SA-15 (1 g COD/g
carbon), followed by the two ICI carbons
(0.15 to 0.25 g COD/g carbon). Ultimate
capacities for BOO removal were esti-
mated to be higher for ICI-HDC and
Nuchar SA-15 (0.05 to 0.04 g BOD/g
carbon, respectively) than for ICI-HDH
(less than 0.02 g BOD/g carbon). All
three carbons were found to be quite
ineffective for THA removal; their ulti-
mate capacities ranged from 0.003 to
0.006 g THA/g carbon.
Tests with Tannery 5 effluent revealed
that Nuchar SA-15 had a slightly higher
capacity (0.35 g COD/g carbon) for the
removal of COD-contributing com-
pounds than the ICI carbons(0.1 to0.2g
COD/g carbon). In terms of BOD re-
moval, the ultimate capacity of Nuchar
SA-15 was estimated to be approxi-
mately 1 g BOD/g carbon; those of ICI-
HDC and ICI-HDH were 0.3 and 0.07 g
BOD/g carbon, respectively. The ulti-
mate capacities of all three carbons for
THA removal were found to be approxi-
mately 0.003 to 0.005 g THA/g carbon.
Ultimate capacities of the carbons for
the removal of COD from Tannery 6
effluent were estimated to be approxi-
mately 0.16 (ICI-HDC), 0.1 (ICI-HDH),
and 0.35 g COD/g carbon (Nuchar SA-
15). For BOD removal, ICI-HDC was
found to be essentially ineffective with
an estimated ultimate capacity of less
than 0.03 g BOD/g carbon. The ultimate
capacity of ICI-HDH was found to be 0.2
g BOD/g carbon, and that of Nuchar
SA-15 was approximately an order of
magnitude higher. Ultimate capacities
of all three carbons for the removal of
THA from this particular effluent were
estimated to be in the range of 0.03 to
0.04 g THA/g carbon.
The ultimate capacities of the three
carbons for the removal of COD from
1:10 dilution of Tannery 7 effluent were
estimated to be as follows: ICI-HDC, 0.8
g COD/g carbon; ICI-HDH, 1 g COD/g
carbon; and Nuchar SA-15,0.9 g COD/g
carbon. Ultimate capacities of all three
carbons for BOD removal from the same
dilution of Tannery 7 effluent were found
to be approximately 1 g BOD/g carbon;
those for THA removal ranged from 0.2
to 0.5 g THA/g carbon.
At Tannery 8, the experimental data
revealed that the ultimate capacities of
all three carbons for COD removal
ranged from0.7to 1.4 g COD/g carbon;
those for BOD removal ranged from
0.09 to 0.9 g BOD/g carbon. Saturation
capacities of all three carbons for THA
removal were approximately 0.01 g
THA/g carbon.
For Tannery 9 effluent, the experi-
mental data yielded approximate ulti-
mate capacities of 0.4 to 0.5 g COD/g
carbon for all three carbons. Those for
BOD removal were in the range of 0.3 to
0.4 g BOD/g carbon, while those for
THA were estimated to be approximately
0.5 g THA/g carbon.
It ca'n be generally concluded that
within Tanneries 0, 2, 3, 7, and 9, all
three carbons exhibited differences in
ultimate capacities equal to or less than
one order of magnitude; for Tanneries 1,
4, 5, 6, and 8, differences between
ultimate capacities were found to be
greater than one order of magnitude.
The above observations indicate that
the removals of COD, BOD, and THA
were a function of carbon type and/or
effluent characteristics; differences in
removals may be attributed to factors
such as effluent composition, speci-
ation, total concentration of sorbates,
competition of sorbates for the available
adsorption sites, and carbon surface
characteristics. The specific reasons for
these differences cannot be determined
at the present time.
Specific Phenols
Four specific chlorophenols were
considered in these investigations:
pentachlorophenol, 2,4,5-trichloro-
phenol, tetrachlorophenol, and 2,4-
dichlorophenol. Their presence and re-
moval by PAC sorption were examined
for Tannery 5 and 7 effluents only. All
three carbons essentially removed most
of the identified specific phenols from
Tannery 5 effluent, but had no observ-
able effect on the effluent from Tannery
7.
TOO
Accountable decreases in TOC con-
centrations were observed only at high
carbon doses, indicating low efficiencies
of all three carbons for the removal of
TOC from all effluents tested.
Chromium
Interpretation of the chromium results
was not possible due to the lack of
available information on both chemical
speciation of chromium and detailed
chemical characterization of the respec-
tive effluents.
» US QOVERNMENT PRINTING OFFICE-1982-559-017/0765
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Oil and Grease
All of the PACs tested were essentially
ineffective with respect to oil and grease
removals.
Cost Estimates
The daily cost for PAC addition at
doses of 300 mg/L to an existing
biological treatment system at an as-
sumed flow rate of 100,000 gal/day
was estimated to be approximately $ 125
per day. Higher carbon doses (10 g/L)
would increase daily costs up to $4,250
(for carbon only).
J. Vuceta and K. V. LaConde are with SCS Engineers, Long Beach, CA 90807.
Donald L. Wilson and Brian A. Westfall are the EPA Project Officers/see below).
The complete report, entitled "Powdered Activated Carbon Adsorption Iso-
therms for Selected Tannery Effluents," (Order No. PB 82-227 786; Cost:
$13.50, 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 Officers can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
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Protection
Agency
EPA 335
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Penalty for Private Use $300
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