United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory _- _ ,
Ada OK 74820 '/i~v
Research and Development
EPA-600/S2-82-076 Sept. 1982
Project Summary
Powdered Carbon-Activated
Sludge—Filtration Processes
for Petroleum Refinery
Wastewater
J. S. McBride, A. T. Knecht, S. A. Sevan, D. J. Muhlbaier, and F. M. Pfeffer
The purpose of this research program
was to determine the effect of the
addition of powdered activated carbon
(PAC) to petroleum refinery activated
sludge systems. Both bench-scale and
full-scale tests were performed. A
wide range of PAC concentrations and
sludge ages were evaluated.
Bench-scale activated sludge sys-
tems were designed and constructed.
The bench-scale units were initially
operated to determine the conditions
for the full-scale test. Additional
bench-scale tests were carried out to
evaluate conditions impractical to
meet during the full-scale testing.
Similar results were obtained during
the full-scale and bench-scale tests. A
moderate enhancement of COD re-
moval was observed. PAC addition
had little effect upon the removal
efficiency of other contaminants or
the toxicity of undiluted effluents. An
economic analysis of PAC addition
was carried out.
This Project Summary was devel-
oped by EPA's Roberts. Kerr Environ-
mental Research Laboratory, Ada,
OK, 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
The 1974 EPA effluent limitations
guidelines for the petroleum refining
industry proposed that best available
treatment economically achievable
(BATEA) be secondary treatment fol-
lowed by filtration and granular activated
carbon (GAC) treatment. GAC adsorption
equipment and operations including
regeneration are costly; consequently,
cost-effective BATEA alternatives to
GAC have been of considerable interest
to both EPA and industry. The addition
of powdered activated carbon (PAC) to
the activated sludge treatment system
is such an alternative for improving
performance and effluent quality.
The purpose of this study was to
establish the effectiveness of adding
commercially available PAC to a full-
scale refinery activated sludge treat-
ment system which was currently
meeting effluent permit limitations.
Both bench-scale and full-scale studies
were carried out. The main purpose of
the bench-scale studies was to estab-
lish the conditions to be evaluated
during the full-scale test. In addition,
bench-scale reactors were operated at
conditions that were impractical to meet
during the full-scale testing.
Conclusions
1. The results from the bench-scale
units were similar to those
obtained from the full-scale units
when operated under similar
conditions.
2. PAC addition resulted in the
moderate enhancement of COD
removal. During the bench-scale
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testing, the effluent COD from
the PAC units was 11 -33 percent
less than from the control units.
This corresponds to a 2-6 percent
improvement in COD removal
efficiency in the PAC units based
upon the overall COD loading.
During the refinery test, the
effluent COD from the PAC unit
was 18 percent less than from
the control which corresponds to
a 2 percent improvement in the
overall removal efficiency of
COD.
3. PAC addition resulted in a small,
but statistically significant, en-
hancement of the removal of oil
and grease. During the bench-
scale tests, the oil and grease in
the effluents from the PAC units
were 0.5 to 2.0 mg/l less than in
the control effluents. During the
refinery test, the oil and grease
concentration was 0.6 mg/l less
in the PAC effluent than in the
control effluent.
4. PAC addition had little effect
upon the removal efficiencies of
TOC, phenol, or phosphorus.
5. PAC addition resulted in higher
effluent suspended solids and
ammonia concentrations during
the refinery test.
6. PAC addition had little effect
upon the removal of priority
pollutants or the fish toxicity of
the undiluted effluents during
the refinery test.
7. PAC addition did result in in-
creased sludge compactability
and sludge settling rates.
8. PAC is abrasive and its use
during the refinery test resulted
in increased wear of sludge
i ecycle pumps. It may be neces-
;ary to modify sludge handling
equipment to prevent the adverse
(iffects of abrasion when PAC
iiddition programs are imple-
mented.
9. "he mixing requirements of PAC
iiludge are greater than conven-
tional sludge. As was demon-
i trated during the refinery test, it
nay be necessary to provide
< dditional mixing to maintain the
I'AC sludge in suspension.
10. " he mechanism of PAC enhance-
i tent appears to be simple ad-
sorption. Biological regeneration
(f the PAC surface did not seem
occur.
11. I the PAC addition program that
\ vas evaluated during the refinery
test were implemented, the
c nnual cost is estimated to be
* 603,500. This corresponds to a
cost of $7/additional Ib COD
removed and $104.95/additional
I > oil and grease removed.
12. h comparing the results of this
study to results obtained in other
Official Business
Penalty for Private Use $300
0000329
At,
recent refinery wastewater PAC
studies, it becomes apparent that
the effect of PAC addition depends
upon the circumstances of the
particular application. It should
not be assumed that PAC addition
will have a similar effect at all
refineries. The suitability of PAC
treatment should be tested in a
bench-scale or pilot-scale study
prior to adoption of a full-scale
PAC program.
Recommendations
1. Since all refinery systems are not
equally amenable to PAC treat-
ment, future work should focus on
what influent characteristics or
operational factors control the
effectiveness of PAC addition.
2. No evidence was found for the bio-
regeneration of the PAC surface.
Since other workers have claimed
that bio-regeneration does occur,
future work should focus on the
mechanism of PAC enhancement
to determine under what conditions
bio-regeneration occurs.
J. S. McBride, A. T. Knecht, S. A. Bevan. and D. J. Muhlbaier are with Atlantic
/?/ :hfield Company, Harvey. IL 60426; the EPA author F. M. Pfoffer (also the
EPA Project Officer, see below) is with the Robert S. Kerr Environmental
Research Laboratory, Ada, OK 74820.
The '.omplete report, entitled "Powdered Carbon-Activated Sludge—Filtration
Processes for Petroleum Refinery Wastewater,"(Order No. PB 82-252 933;
Co|sf: $10.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
The $PA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
Ada. OK 74820
United States
Environmental Protection
Agency
Center for Environr
Information
Cincinnati OH 452
lental Research
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