United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-87/055 Nov. 1987
&EPA Project Summary
Waste Minimization Audits at
Generators of Corrosive and
Heavy Metal Wastes
M. Drabkin and E. Rissmann
The USEPA is encouraging hazardous
waste generators to develop programs
to reduce the generation of hazardous
waste. To encourage such programs
the Agency's Hazardous Waste Engi-
neering Research Laboratory is sup-
porting the development and evaluation
of a model hazardous waste minimiza-
tion audit procedure. The procedure was
tested in several facilities in the summer
of 1986.
Waste minimization audits (WMAs)
have been carried out in an electric arc
furnace (EAF) specialty steelmaking
complex. These audits were intended
to develop waste minimization options
for two hazardous waste streams at
this facility: corrosive waste and heavy
metals waste. Waste minimization
options considered were in one of three
categories: source reduction, recycling
or treatment (in the same order of
preference).
Application of WMA methodology to
a corrosive waste stream (KO62) gen-
erated at one plant in this complex,
resulted in the development of a pro-
mising recycling option for the recovery
of calcium fluoride (fluorspar) which is
directly usable as a metallurgical flux
(replacing presently purchased material)
in the EAF steelmaking process at this
facility. Savings obtained by using this
option (including $68,000 savings from
a thirty percent reduction in off site
nonhazardous waste disposal, and
$100,000 savings in purchased chemi-
cal costs) were estimated at $168,000
annually, and the proposed .process
could largely use existing process
equipment.
Application of the WMA methodology
to a heavy nnetals-bearing waste (EAF
dust-listed waste KO61) generated at
another plant in the steelmaking com-
plex did not result in any viable source
reduction or recycling options for this
waste. However, a detoxification treat-
ment step proposed for this material is
economically attractive based on pre-
liminary estimates, and bench-scale
development of this option appears
warranted.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH, 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
The U.S. Environmental Protection
Agency (EPA) is expanding its efforts to
promote waste minimization activity in
the private sector by providing technical
assistance to generators of hazardous
waste. As part of this effort, the EPA
Office of Research and Development/
Hazardous Waste Environmental Re-
search Laboratory (ORD/HWERL), Cin-
cinnati, Ohio, is promoting the develop-
ment of a generalized or model waste
minimization audit (WMA) procuedure
and testing this procedure in actual pro-
duction facilities agreeing to cooperate
with the audit teams selected for this
task. Initially, the following four hazardous
wastes were selected by EPA/ORD/
HWERL to be studied in this effort: 1.
Corrosives; 2. Heavy metals; 3.
solvents; and 4. Cyanides.
In the full report, results are presented
of WMAs conducted at generators of
corrosive and heavy metals wastes. A
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specialty steel manufacturing complex
agreed to provide host facilities for the
reported WMA effort. This complex in-
cludes the following plants, which were
audited in the present effort:
An annealing and pickling facility for
finishing stainless strip only. This
facility is designated as Plant No. 1.
Cold rolling, annealing and pickling
facilities for finishing both stainless
and electrical steel product strip.
These facilities are designated as
Plant No. 2.
The melt shop employing electric
arc furnaces (EAFs) for the manu-
facture of stainless and electrical
steels, as well as hot rolling furnaces
for fabricating these steels into pro-
duct strip, and EAF emission col-
lection and cleanup equipment. This
entire facility is designated as Plant
No. 3.
Description of the WMA Protocol
The function of the protocol is to force
the use of a step-by-step procedure for
conducting a WMA at a host site. The
initial WMA protocol was developed in
earlier work and was further refined dur-
ing the present effort. The protocol is
applicable to all three categories of waste
minimization (source reduction, recycling,
and treatment).
The teams employed in carrying out
the audits were composed entirely of
employees of outside consulting/engi-
neering firms. After selection of the host
facility, the following sequential steps
were executed by the audit team:
1. Preparation for the audit
2. Host site pre-audit visit
3. Waste stream selection
4. Host site waste minimization audit
visit
5. Generation of waste minimization
options
6. Preliminary evaluation (including
preparation of preliminary cost esti-
mates) and ranking of options in
three categories (effectiveness, ex-
tent of current use, application
potential)
7. Presentation, discussion and joint
review of options with plant
personnel
8. Final report preparation and pre-
sentation to host site management
This protocol was used to conduct the
WMAs, as summarized below.
Results of the WMA Conducted at
a Generator of Corrosive Waste
Audit at Plant No. 1
Following the selection of Plant No. 1
as a host site for a WMA for corrosive
waste (listed waste K062), a pre-audit visit
was made (and process and waste
treatment operations were directly
observed. The Plant No. 1 facility consists
of a stainless steel strip annealing and
pickling line |or processing 300 and 400
series stainless steels and a pickling waste
water neutralization plant.
Following [annealing of the stainless
steel strip, this material is fed through
the continuous pickling process. The strip
is first treated in a Kolene bath (the latter
a mixture of molten sodium and potassium
hydroxides) at 800ฐFfor initial dissolution
of surface scale on the strip, followed by
water quench^ and rinse tanks to cool and
flush the treated strip, and then a nitric-
hydrofluoric ^cid pickle using a mixture
of 8-10 percent nitric acid and 2-4 per-
cent hydrofluoric acid. Following a water
rinse, the stainless steel strip is coiled
and shipped. Air emissions from the
Kolene treatment and acid pickling tanks
are controlled through the use of fume
scrubbers. Trie following waste waters
are generated in the pickling process:
A Kolene rinse water which is highly
alkaline [and contains sodium and
potassium hydroxides, sodium and
potassium carbonates, and chro-
mates resulting from some oxidation
of the chromium on the steel surface
during the Kolene descaling treat-
ment. Chromate levels are below
200 ppnj, and the spent rinse water
has a pH of about 12. Approximately
45 gallons per minute (gpm) of
Kolene finse water is discharged
from the| process.
Spent HF/HNO3 pickle liquor waste.
This stream is periodically dumped
and replaced with a mixture of fresh
HF/HNO3 and recycled spent pickle
liquor.
Rinsewater from the HF/HNO3
pickling operation. This stream is
generated continuously from the
rinsing operation.
The combined spent pickle liquor
and rinse water waste stream from
the HF/fjINOs pickling operations has
a pH of|about 2 and contains dis-
solved metals, nitrate and fluoride.
The cornbined wastewater stream
flow from the pickling and rinse tanks
averages 150 gpm. Average com-
position of the spent pickle liquor/
rinse water stream over a one-week
operation (which includes a once-
per-week dump of spent pickle liquor
into the combined wastewater
stream) is given as:
Parameter Average Concentration, mg/l
Cr (trivalent)
Ni
Cd
Fe
F
pH
164
47
<0.02
1,110
1,100
-2.0
The Kolene waste rinse water and the
combined spent acid/rinse water waste
stream are treated as follows:
Raw Kolene rinse water is treated in
a mix tank with excess ferrous sulfate
heptahydrate and sulfuric acid with
about 80 minutes retention time.
The ferrous ion reacts with chromate
to reduce hexavalent chromium to
trivalent chromium. The pH of the
treated waste is approximately 4.
The combined spent acid/rinse water
waste and the treated Kolene rinse
water are pumped to a mix tank
where slaked lime is added. The final
pH after lime addition is about 8. The
addition of lime causes the heavy
metals present to precipitate as
hydroxides and the fluoride to pre-
cipitate as calcium fluoride. The re-
sulting mixture of treated wastewater
and precipitated solids is treated in a
second mix tank where coagulant is
added and the stream is then fed to
two 30-foot diameter clarifiers oper-
ated in parallel. The clear overflow
from the clarifiers is discharged to the
outfall (a local creek) meeting the
conditions of an NPDES permit and
the underflow is fed to two vacuum
filters operated in parallel. Non-
hazardous solids recovered from the
filters are disposed of offsite and the
filtrate is recycled to the treatment
process.
During the formal audit phase of this
study at the Plant No. 1 acid pickling
facility, process and waste treatment
operations were intensively studied by
the audit team. The use of various potential
source reduction and recycling options
was reviewed with plant personnel. Plant
No. 1 already recycles part of the spent
acid mixture to the pickling line, thus
reducing fresh acid use. Based on the
audit team's evaluation and discussions
with plant personnel, there did not appear
to be any other significant source reduction
options available.
With respect to recycling, the present
neutralization treatment of the combined
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Plant No. 1 pickling line wastewater
stream (KO62) generates a mixed sludge
for which there is essentially no potential
for reuse. The audit team determined,
however, that the raw waste (the spent
HF/HNO3 pickle liquor/rinsewater dis-
charged from the pickling operation) does
contain a constituent (fluoride ion) that
could be converted into a useful product-
calcium fluoride (fluorspar). The electric
arc furnace (EAF) facility at this steel-
making complex (designated as Plant No.
3) presently purchases about 1,000 tons
per year of fluorspar for use as a furnace
flux material in the steelmaking process.
Current cost for metallurgical grade
fluorspar (approximately 75-80 percent
calcium fluoride) for flux use is $100 per
ton at the plant. The audit team proposed
a waste minimization option for recovery
of calcium fluoride wherein the combined
Plant No. 1 wastewater stream at pH ~2
(excluding the treated Kolene waste) is
treated with slaked lime at a controlled
rate so that pH 2.5 is not exceeded.
Calcium fluoride will precipitate selec-
tively, and at this pH, fluoride solubility
data indicate that a level of 65 ppm
dissolved fluoride will be achieved. With
about 1,100 ppm dissolved fluoride in the
raw wastewater, approximately 95 percent
of the fluoride will precipitate. This is
equivalent to about 1,300 tons per year of
calcium fluoride potentially recoverable
(based on 330 days per year operation),
which more than equals the annual con-
sumption of calcium fluoride (fluorspar
flux) in the EAF operation and Plant No. 3.
Hydroxides of iron, nickel, and chromium
are all highly soluble at pH values below
3.0 and thus would not be expected to
co-precipitate with the calcium fluoride.
The combined spent HF/HNO3 pickle
liquor and rinse water discharge would be
treated in the same waste acid neutraliza-
tion system now used to generate the
neutralized nonhazardous solids dis-
charged off site and NPDES effluent to the
outfall. However, the neutralization would
be done in two stages, thereby effecting
the recovery of a reasonably pure calcium
fluoride in the first stage. After the first
stage of neutralization, the presently
treated Kolene waste would be combined
with the partially neutralized waste pickle
liquor/rinse water stream. The combined
stream would then be neutralized and
discharged to the outfall.
If the above described option were to be
put into operation at Plant No. 1, not only
would the generation rate of sludge from
KO62 treatment be reduced (resulting in a
saving in offsite sludge disposal costs).
but a substantial potential savings in
chemical purchases could be made. Plant
personnel agreed with the audit team that
this was a worthwhile option.
After a recycling option established for
the Plant No. 1 corrosive waste, the pre-
liminary engineering design and cost
estimate for this option was developed. A
preliminary estimate (using 1986 capital
and operating cost data) of the economics
of this recycling option indicates the
following:
Total capital cost
(including new
drying and
briquetting
equipment and
retrofitting of one
existing clarifier
vacuum filter system
to make it corrosion-
resistant at pH 2.5) $300,000
Annual operating cost $ 46,000/yr
Savings due to
replacement of
purchased fluorspar $100,000/yr
Savings due to lower
cost of offsite waste
disposal $ 68,000/yr
Total potential savings $168,000/yr
Estimated payback period 2.5 years
Estimated internal
rate of return (based
on an economic life
of 5 years) 28 percent
Audit at Plant No. 2
Plant No. 2 consists of cold-rolling
equipment to convert raw stainless steel
and electrical steel slabs into strip,
annealing ovens, and a series of six
countercurrent flow pickling lines which
acid pickle stainless and electrical steel
strip produced in the cold-rolling equip-
ment as well as stainless and electrical
hot-rolled steel strip produced in the EAF
raw steel manufacturing facility. Its six
pickling lines use HF, HNO3, H2SO4, and
mixtures thereof and have a total name-
plate capacity of 1,833 tons per day of
processed steel strip.
Emissions from all of the pickle lines
are controlled by use of fume scrubbers.
Following pickling, the treated strip is
wound into coils and shipped.
The six pickle lines generate the fol-
lowing spent pickling acids: dilute spent
sulfuric acid, dilute spent mixed sulfuric-
hydrof luoric acid mixtures and dilute spent
mixed nitric-hydrofluoric acid mixtures
(also containing dissolved iron salts and
traces of dissolved chromium, cadmium,
and nickel), as well as rinse waters con-
taining lower concentrations of these
components. About 313,000 gallons of
spent sulfuric acid, 144,000 gallons of
spent sulfuric/hydrofluoric acid, 12,000
gallons of spent hydrofluoric/nitric acid
pickle liquors and 9.7 million gallons of
rinse water are generated in this facility
per week. The average composition of the
combined waste stream (in terms of critical
metal and non-metal parameters) is as
follows:
Parameter Average Concentration, mg/l
Cr
Ni
Cd
Fe
Fluoride
pH
49
28.5
<0.02
500
39
~2
This stream also contains emulsified and
free fatty oil and grease from the cold
rolling operations at this facility. The
combined wastewater discharge from
Plant No. 2 is sent to a central treatment
facility onsite where it is treated with lime
to effect precipitation of metals as the
corresponding hydroxides and removal of
fluoride as calcium fluoride. The treated
wastewater slurry is then pumped to a
series of onsite large lagoons where the
suspended solids are removed by sedi-
mentation and the treated wastewater is
then discharged to the outfall. The pre-
cipitated solids meet EP-toxicity test levels
for hazardous metals and the treated
wastewater is discharged to a local creek
under an NPDES permit.
During the formal audit phase of this
study at the Plant No. 2 acid pickling
facility, the use of source reduction and/or
resource recovery options was studied by
the audit team. No source reduction op-
tions were identified by the audit team.
Furthermore, the current neutralization
treatment of the combined pickling and
cold-rolling aqueous waste stream (listed
waste KO62) generates a mixed metal
hydroxide-gypsum-calcium fluoride sludge
for which there is no reuse potential. The
key to waste minimization at this plant is
suitable segregation of selected spent
acid wastes before these wastes are
combined at the process building outlet
flume (the latter discharging to a cen-
tralized wastewater neutralization pro-
cess) an option that plant personnel
indicated would be highly disruptive to
plant operations and costly as well. How-
ever, assuming that pickling waste stream
segregation is feasible, the following waste
minimization option is proposed by the
audit team:
As a recycling option segregate an
appropriate amount of waste sulfuric
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acid pickle liquor (13.5 million gallons
per year are potentially available from
three pickling lines).* Two uses for
this material were identified by the
audit team:
Reduction of hexavalent chro-
mium in a bleed stream of venturi
scrubber waste resulting from
scrubbing of EAF dust in Plant
No. 3.
Reduction of hexavalent chro-
mium in the Kolene waste in
Plant No. 1.
Both of these uses presently employ
purchased solid ferrous sulfate
heptahydrate. Recycled sulfuric acid
pickle liquor (containing 5 to 10 per-
cent dissolved ferrous sulfate) is
usable for this purpose.
The technical and economic feasibility
of this recycling option was evaluated by
the audit team. A preliminary estimate
of the economics of this recycling option
indicates the following:
Total capital cost
(including new
tankage, piping, and
pumps, a tank truck
to haul the spent acid
between the various
facilities and suitable
permitting) $255,000
Annual operating cost $ 20,000/yr
Savings due to
replacing purchased
ferrous sulfate
heptahydrate with
waste ferrous
sulfate/sulfuric acid
pickle liquor $ 44,000/yr
Savings due to lower
lime usage for
neutralization at
Plant No. 2 ?..8'.0.9ฐ/yr
Total potential savings $ 52,000/yr
Estimated payback period 8.0 years
The payback period of eight years is
almost three times the usually acceptable
period of three years, making the proposed
project distinctly unattractive from an
economic standpoint. In addition to the
obvious economic disadvantage of this
option, plant personnel are concerned
with the cost and disruption of decoupling
the internal discharge points of this waste
(in the pickling process building) needed
to segregate the appropriate amount of
this waste for recycle. No information was
available from the plant to permit estima-
Bascd on 300 days per year (43 weeks/yr) operation
o( Iho Plant No, 2 acid pickling lines.
tion of the cost of decoupling this waste
quantity from the remaining waste
streams discharged from the facility.
However, sincejthe use of this option does
result in some \X/aste minimization as well
as a small but measurable extension in
the life of the present waste lagoon dis-
posal system (approximately 10 percent
less calcium sulfate and metals-containing
solids would be deposited in the lagoons),
the audit team believes that the option
should continue to be reviewed at Plant
No. 2.
Results of the WMA Conducted at
a Generator of Heavy Metals Waste
During the pj-e-audit visit to this facility
(designated as Plant No. 3) the audit team
became acquainted with process opera-
tions at the EAF melt shop and the wastes
generated from these operations. The
melt shop contains three 165 ton capacity
EAFs used to manufacture 300 and 400
series stainless steels and silicon steels,
as well as orje 175 ton argon-oxygen
decarburizer (ADD) used to further refine
the raw stainless steels. Steels leaving
the furnaces are processed through con-
tinuous casting and hot-rolling operations
to produce coils of strip which are sent to
the acid pickling facility (Plant No. 2) for
final processing. Production of stainless
and electrical steels is approximately
270,000 tons per year.
The pre-audjt visit yielded the following
waste stream faharacterization and treat-
ment information at:
The three EAFs and the AOD at the
melt shop generate about 8,000 tons
per year (TPY) of particulate emissions
(listed wa'ste KO61).
Of these I emissions, approximately
7,000 TPY are removed from the EAF
vent gases using venturi scrubbing;
the remaining 1,000 TPY include
EAF fugitive emissions as well as
emissions removed from AOD vent
gas, and are recovered in a baghouse.
The venturi scrubber slurry is clarified
and filtered with the filter cake, con-
taining about 30 percent water, dis-
charged at the rate of 10,000 TPY.
The combined EAF dust and sludge
(listed waste KO61) leaving the plant
totals about 11,000 TPY and is sent
to offsite hazardous waste landfills
at an annual cost of approximately
$1.0 million.
During the detailed audit phase of this
study at Plant No. 3, the use of source
reduction and/or recycling options for
EAF dust emissions was reviewed with
plant personnel. The following information
was developed which discouraged further
exploration of these waste minimization
options for the K061 waste generated at
the plant:
With the primary steel products of
this facility being 300 and 400 stain-
less grades, there will always be
significant levels of the following
hazardous metals in the EAF dust:
chromium and nickel (because of the
alloying requirements of stainless
steels), cadmium and lead. Contribu-
tions to these metals in the EAF dust
come from the scrap feed as well as
from the alloying additives. These
EAF dust constituents are expected
to always generate levels ofone or
more of these hazardous metals in
excess of the presently allowable
RCRA levels in leachate from the
TCLP procedure (using acetate buf-
fer). Source reduction is therefore
not an available option to the plant.
Plant No. 3 has made a number of
attempts (without success) to recycle
EAF dust to the steelmaking furnaces.
Plant personnel also indicated that
because of the volume of dust gen-
erated and the sensitivity of the steel
product quality to tramp elements in
the recycled dust, it is unlikely that a
large percentage of this waste could
ever be recycled to the process.
With respect to use of the KO61
waste by a metals reclaimer, the
principal ingredient of value (zinc) is
only present to the extent of 8 to 10
percent in the Plant No. 3 EAF dust.
In order for EAF dust to be economi-
cally attractive to reclaimers, it should
have at least 20 percent zinc and
preferably nearer 50 percent. Addi-
tionally, internal recycling of the EAF
dust, which would tend to enrich the
zinc content of the residual material,
is presently not available to Plant No.
3 due to factors discussed above.
No source reduction and/or re-
cycling options appear to be available
to reduce the quantity of KO61 waste
generated by this plant. The last
resort is an alternative treatment
step proposed by the audit team
which appears to be the only option
available for this waste stream and is
summarized as follows:
Plant No. 3 would (1) convert the
material into a nonhazardous waste
using a chemical stabilization tech-
nique (using lime kiln or cement kiln
dust and water blended with the EAF
dust to generate solidification re-
actions and create an essentially
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insoluble matrix), (2) apply to have
the waste delisted by EPA, and (3)
dispose of the delisted material in an
onsite dedicated landfill.
A preliminary estimate (using 1986
capital and operating cost data) of
the economics of this option (for 10-
year onsite disposal) results in the
following:
9 Total capital cost $1.75 million
Annual operating
cost $0.42 million/yr
ฎ Estimated payback period 3 years
Estimated internal
rate of return (based
on an economic life
of 5 years) 20 percent
Present annual
KO61 waste
generation rate 11,000 TPY
Proposed annual
treated K061 waste
generation rate 22,000 TPY
Cost of treatment
and disposal of
waste $35/ton
Annual savings (over
amortized life of
treatment plant and
onsite landfill), if this
option was
implemented $227,000/yr
The disposal cost of KO61 waste using
this treatment option is estimated at
$35/ton of treated waste compared to
$100/ton for the current cost of disposal
of the raw waste even though the treated
waste generation rate has doubled. It is
therefore recommended that this treat-
ment option be pursued further with an
initial bench-scale effort to establish the
appropriate waste stabilization technique.
It should be noted that plant personnel
are in agreement with this assessment of
available waste minimization options.
Conclusions
The following conclusions can be drawn
based on the study summarized herein:
The WMA methodology can be suc-
cessfully applied to the minimization
of hazardous waste, in this case
corrosive waste (KO62), in at least
one industry the specialty steels
segment of the EAF steelmaking
industry. Application of the WMA
protocol to a plant in this industry (a
stainless steel pickling facility in an
EAF steelmaking complex), resulted
in the identification of a technically
and economically feasible recycling
option for the recovery of fluorspar
(calcium fluoride) from a corrosive
waste stream. The fluorspar would
be used internally in place of pur-
chased material. Use of this waste
minimization option results in savings
of $168,000 annually and a 30 per-
cent reduction in final waste disposal
volume.
9 Application of the WMA methodology
to another corrosive waste generated
at another steel pickling facility in
the same steelmaking complex, re-
sulted in the development of a re-
cycling option requiring segregation
of a portion of this waste (waste
ferrous sulfate/sulfuric acid pickle
liquor) for internal recycle replacing
purchased ferrous sulfate heptahy-
drate. However, this option is not
economically feasible and this dis-
advantage outweights the principal
advantage of a small prolongation of
the life of the onsite facility for dis-
posal of neutralization sludge from
present waste treatment.
An attempt to apply the WMA
methodology to another hazardous
waste stream: heavy metals con-
taining EAF dust (KO61) generated
in the EAF steel plant at the same
steelmaking complex, could not be
considered as successful inasmuch
as both of the more preferred waste
minimization approaches (source
reduction and recycling), were not
technically feasible in this case.
However, the identified treatment
approach: detoxification of the waste
by onsite chemical stabilization/
solidification treatment, followed by
onsite disposal in a dedicated landfill,
appears to be worth investigating
further based on the results of a
preliminary technical and economic
evaluation of this option.
It is believed that the on-site audit
(employing the WMA methodology
developed in this study) is a distinctly
useful tool for waste minimization
due to the one-to-one contact with
the industrial waste generators by
qualified engineering professionals
on the audit team.
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This Project Summary was prepared by staff of Versar, Inc., Springfield, VA.
Harry M. Freeman is the EPA Project Officer (see below).
The complete report, entitled "Waste Minimization Audit Report: Case Studies
of Corrosive and Heavy Metal Waste Minimizatioh at a Specialty Steel
Manufacturing Complex," (Order No. PB 88-107 180/AS; Cost: $13.95,
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:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268 !
Unuod States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268 ;
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penally for Private Use S300
EPA/600/S2-87/055
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