United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-85/060 July 1985
&ER& Project Summary
Alternative Processes for
Treatment of Sinter Plant
Wastewater
Cinthia L. Rudasill, Karl Brantner, and Stephen A. Hall
With the promulgation of Best Avail-
able Technology Economically Achiev-
able (BAT) Effluent Guidelines and
Standards for Iron and Steel Manufac-
turing, a greater degree of treatment
than the clarification process normally
used to achieve best practicable tech-
nology (BPT) standards may be required
for sintering plant blowdown. This study
evaluated the effectiveness of two
treatment alternatives in achieving the
BAT standards: (1) direct filtration,
using a dual media filter; and (2) hydrox-
ide precipitation with lime, followed by
dual media filtration. Evaluation of a
third alternative, alkaline chlorination,
was attempted; but, due to nonrepre-
sentative test conditions, the effort was
abandoned.
The treatment processes were tested,
using two EPA-owned mobile pilot plant
trailers: one contained a clarifier, used
to simulate preclarification; and the
other contained the hydroxide precipi-
tation clarifier, chemical tanks, dual
media filter, and associated equipment.
The limited data generated during the
study indicate that either treatment
alternative tested would produce an
effluent that would meet the promul-
gated BAT standards. Direct filtration is
less expensive and requires less main-
tenance and operator attention than the
hydroxide precipitation/filtration alter-
native.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC 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 in-
formation at back).
Introduction
Under the Effluent Guidelines and
Standards for the Iron and Steel Manu-
facturing Point Source Category promul-
gated May 27, 1982, Best Available
Technology (BAT) effluent limitations for
the Sintering subcategory are based on
applying a higher degree of treatment
than BPT clarification alone. Pilot plant
studies were conducted to evaluate two
treatment alternatives for removal of
selected pollutants for which BAT limita-
tions had been proposed.
NOTE: This study was conducted
before the May 27, 1982, pro-
mulgation of the BAT Effluent
Limitations for the Iron and Steel
Manufacturing Point Source
Category. The basis for the
selection of pollutant parameters
for evaluation of the alternative
treatment systems investigated
in this study was the proposed
guidelines made public in
December 1980. This report has
been updated to indicate the
promulgated guidelines.
The treatment alternatives piloted were:
(1) direct filtration, employing a dual
media pressure filter; and (2) hydroxide
precipitation with lime, followed by dual
media filtration. A third alternative, alka-
line chlorination, was attempted; but, due
to an intermittent production schedule
during this test phase, representative
samples were not collected. The waste-
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water tested was blowdown from the
venturi scrubber and cyclonic mist elim-
inator wet air pollution control system.
Wastewater analyses quantified suspend-
ed solids, fluoride, cyanide, phenols, oil
and grease, and various heavy metals and
priority pollutants.
The major objective of the testing
program was to develop a data base from
which the alternative treatment systems
could be evaluated both individually and
comparatively. The data base was gener-
ated through laboratory analyses of
regularly collected samples and moni-
tored operating conditions during pilot
plant operation. To assess the perfor-
mance of each process, the data was
analyzed for removal of selected pollu-
tants. Capital and operating costs were
developed to assess the economics of
each process application. An overall
comparative evaluation was then made,
based on both performance and econom-
ics.
Summary
Testing Program Description
Trailer-mounted pilot facilities were
used to test two treatment alternatives
for sinter plant blowdown: (1) direct
filtration, using a dual media filter; and(2)
hydroxide precipitation with lime, follow-
ed by dual media filtration. The pilot plant
consisted of two existing EPA-owned
trailers, part of the Mobile Wastewater
Treatment System (MWWTS) designed to
provide treatment for a nominal through-
put of 5 gpm.* Trailer No. 1 contained the
chemical treatment system and filtration
equipment. Trailer No. 2 contained a
clarif ier for preclarification, required since
the influent to the pilot plant was tapped
from the sintering blowdown line prior to
treatment with other waste waters in an
existing on-site clarifier.
Flow trains for the direct filtration and
hydroxide precipitation followed by filtra-
tion treatment alternatives are shown in
Figure 1. Filtration is common to both
alternative BAT treatment models that
were tested in the pilot study. Direct
filtration of sintering blowdown was
evaluated for removal of suspended solids
and other pollutants (e.g., metals, which
may be in particulate—nonsoluble—
form). In the hydroxide precipitation
alternative, filtration of clarified effluent
is a polishing step for removing the metal
hydroxides that are not removed by
clarification.
The filter media consisted of 12 in. of
sand, with a particle size in the range of
0.4 to 0.8 mm, and 24 in. of anthracite,
with a particle size of 1.0 to 1.5 mm. The
hydraulic loading rate to the filter was
kept at approximately 5 gpm/ft2 during
the tests.
Precipitation of heavy metals as hy-
droxides through the addition of lime is a
well-established technology. Lime is
added to raise the pH to a level found to be
the most suitable for optimum precipita-
tion of the metal hydroxides which are of
concern. The metal hydroxide precipitates
form a floe which can entrain particulates,
including other metallic forms, and thus
enhance their removal. In addition to
removing metals, hydroxide precipitation
with lime can also remove fluoride by
providing a source of calcium for precipi-
tation of calcium fluoride.
Although hydroxide precipitation is
relatively simple, it has several limita-
tions. Its effectiveness in removing heavy
metals is a function of the solubility of the
metal hydroxides which, in turn, is a
function of pH and water quality. Thus
removal of heavy metals is limited to the
solubility of the metal hydroxides in the
particular wastewater matrix under con-
sideration. Based on bench scale data
and previous experience with hydroxide
precipitation of heavy metals, the pilot
tests were run at an operating pH of 10. A
slurry of hydrated lime—Ca(OH)2—was
applied to the wastewater in a rapid mix
/. Direct Filtration
tank to maintain a pH of 10. The waste-
water then flowed by gravity to a floccu-
lator/clarif ier for f locculation and settli ng.
Eight-hour composite samples of raw
wastewater (pilot plant influent), clarifier
effluent (during the hydroxide precipita-
tion testing phase), and final (filtered)
effluent were collected automatically and
analyzed for selected pollutant param-
eters.
The analytical work performed for this
study incorporated quality control anal-
yses, including method and reagent
blanks, field replicates, laboratory repli-
cates, standards and spikes. The quality
control data was monitored daily. All
samples received by the laboratory were
logged in and processed immediately
upon receipt to ensure that holding times
were not exceeded.
The selected pollutant parameters for
the sinter plant pilot testing included
suspended solids, pH, fluoride, cyanide,
phenols, oil and grease, and certain heavy
metals and priority pollutants. These
parameters (shown in Table 1)were used
to develop a data base for evaluating the
alternative treatment processes.
Plant Site
Pilot testing was conducted at the
Armco Steel Corporation, Middletown,
Ohio, Works. The sinter plant converts
iron-bearing waste fines into blast fur-
nace feed materials. During the pilot
plant test period, the feed to the sinter
Raw
Wastewater
2. Hydroxide Precipitation With Lime
Dual
-M Media
Filter
Treated
Effluent
Dual \ Treated
Media
Filter J Effluent
(*) Readers more familiar with metric units may use
the conversion factors at the back of this Summary.
Chemical Addition
Flocculation and Clarification
Figure 1. Pilot plant process flow trains.
Filtration
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Table 1. Pollutant Parameters Selected
for Pilot Testing of Sinter Plant
Slowdown
Phenols (4 AAP)
Fluoride
Suspended Solids
Oil and Grease
pH
Fluoranthene
Phenol
Chrysene
Pyrene
Cadmium
Chromium
Copper
Cyanide
Lead
Nickel
Silver
Zinc
plant consisted of approximately 70 per-
cent BOF slag, 15 percent taconite fines,
12 percent blast furnace scrubber sludge,
and 3 percent coke fines.
Waste gases from the sinter plant are
cleaned by a venturi scrubber and cyclonic
mist eliminator. Slowdown, taken directly
from the bottom of the mist eliminator
tank at a rate of 325 gpm, comprises
about 15 percent of the mist eliminator
flow. The balance of the flow is recircu-
lated back to the scrubber.
Results and Evaluation—Summaries of
the direct filtration data and hydroxide
precipitation/filtration data are given in
Tables 2 and 3, respectively. To ensure
representative values, unusually high or
low values have been dropped from the
averages and ranges in these tables.
Priority pollutants that were detected are
given in Table 4.
The promulgated BAT and BPT limita-
tions are given in Table 5.
The two processes were compared with
respect to effectiveness in removal of the
selected pollutant parameters. Direct
filtration was effective in removing all of
the selected pollutant parameters found
to be present in the sinter plant blowdown
in significant quantities. The degree of
chromium and zinc removal varied with
varying levels of soluble chromium and
zinc in the influent. Cyanide, present in
very low levels, was not affected. All of
the BAT and BPT Effluent Limitations
were met by the direct filtration effluent.
Filter operation is simple and easily
controlled, requiring minimal operator
attention. No sludge is produced. The
backwash solids loadthat is intermittently
generated could be recycled to the head
of most existing BPT treatment systems
without any additional treatment.
Hydroxide precipitation followed by
filtration was effective in removing all of
the selected pollutant parameters found
to be present in significant quantities,
except phenols. The degree of chromium
removal varied with the level of soluble
influent chromium. Cyanide, present in
very low levels, was not affected. All of
the BAT and BPT Effluent Limitations
were met by the hydroxide precipitation
and direct filtration effluents. Operation
is straightforward and could be automati-
cally controlled with a high level of
reliability. Operations manpower would
be mainly for lime slurry batching, system
monitoring, and routine maintenance.
The waste sludge which is produced can
be treated and disposed of along with BPT
sludge at most plants by employing
existing BPT facilities.
Both treatment processes performed
well; however, neither performed signif-
icantly better than the other. Hydroxide
precipitation achieved slightly lower
residuals for most parameters than direct
filtration. Direct filtration produced a high
quality effluent at a significantly lower
cost and less operational considerations
and, therefore, best achieved the goals of
BAT.
Because heavy metals in the sinter
plant blowdown were predominantly in
particulate form, direct filtration was
effective in removing them. If significant
quantities of soluble metals had been
present, its effectiveness would have
been considerably less. Therefore, this
evaluation is based on the sinter plant
blowdown that was treated during the
study.
Economic Analysis
Estimated capital costs and operating
costs for the direct filtration and hydroxide
precipitation with filtration processes are
given in Table 6. Construction costs were
developed for treatment facilities de-
7able 2. Direct Filtration Data Summary
Parameter
Suspended
Solids
pH
Fluoride
Phenol
Cyanide
Oil & Grease
Total Cadmium
Total
Chromium
Total Copper
Total Lead
Total Nickel
Total Silver
Total Zinc
Preclarifier Influent (ppm)
Mean Range
1644
7.9
109
0.23
0.07
158
0.017
0.362
0.150
0.490
0.140
0.0130
13
120-5210
7.3-8.6
15-250
0.04-0.60
0.047-0.094
28-310
86
38
—
77
'Except for the Preclarifier, for which fewer samples were taken, the number of samples may vary due to unusually high or low data values which were
dropped from the averages and ranges. Six oil and grease samples were taken at each sampling point.
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Table 3. Hydroxide Precipitation Data Summary
Preclarifier Influent (pprnj Number of Pilot Influent (ppm) Dumber of Clarifier ^fluent (ppm) Number of Filter Effluent (ppm) Number of
Parameter
Suspended
Solids
PH
Fluoride
Phenol
Cyanide
OH&
Grease
Total
Cadmium
Total
Chromium
Total
Copper
Total
Lead
Total
Nickel
Total
Silver
Total
Zinc
Mean
143
7.9
193
0.32
0.03
191
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In developing the cost estimates, an
effort was made to provide a realistic and
representative estimate for implementing
the BAT treatment alternatives. However,
site-specific costs will influence actual
costs for any facility. In addition to these
site-specific costs, a few other costs have
not been included. Construction cost
estimates do not include:
Land acquisition/space allocation
Ancillary facilities
Retrofitting/process equipment
adaptation
Equipment replacement
1.
2.
3.
4.
5. Backup facilities, except those
normally engineered into waste-
water treatment design
6. Utility and yard services
7. Start-up costs
8. Indirect costs (interest during con-
struction, insurance).
Conclusions
Study Conclusions
Results of the pilot studies for treating
sinter plant blowdown indicate that both
direct filtration and hydroxide precipita-
tion followed by filtration are effective in
removing the selected BAT pollutants to
the levels indicated in the effluent guide-
lines and limitations.
Direct filtration significantly reduced
suspended solids, oil and grease, and
heavy metals levels. A slight reduction in
phenols levels was observed. None of the
pollutant parameters for which effluent
limitations have been promulgated ex-
ceeded these limitations.
Hydroxide precipitation followed by
filtration also produced an effluent that
met all limitations.
Influent cyanide concentrations and,
consequently, effluent concentrations
met both the maximum and average BAT
limitations, throughout the study. As
expected, the data showed that neither
process removed cyanide.
Since the pH of the influent wastewater
was fairly high and good removal of
metals, suspended solids, and fluoride
was observed in the preclarifier, the
benefits of raising the pH further by lime
addition were marginal. Optimizing the
clarification step in BPT, by a lower
overflow rate and polymer addition, may
be able to achieve an effluent quality
comparable to that achieved by direct
filtration.
Both treatment trains appear to be
capable of providing the degree of treat-
ment required to meet effluent limita-
tions. Direct filtration, however, is con-
siderably less expensive and requires
less operator attention and maintenance
than hydroxide precipitation followed by
filtration.
Study Constraints and
Limitations
The primary objective of the testing
program was to develop data for alterna-
tive treatment systems as applied to sinter
plant wastewater. Although the treatment
processes that were evaluated in this
study have been previously tested or
applied for the treatment of metal plating
wastewaters and other iron and steel
wastewaters, no data existed for their
application to the treatment of sinter
plant wastewater. The EPA reqgestedthe
development of 12 data points for each
treatment alternative, to be accomplished
by 8-hour composite sampling during 24-
hour per day pilot plant operation. This
approach was taken primarily because of
time constraints. It is important that the
results of the testing program be viewed
in the proper perspective, with due con-
sideration of the limitations attendant to
both the duration and the method of
testing.
Direct Filtration and Hydroxide Precipi-
tation—The data for the two treatment
Table 5. Promulgated BA T and BPT Effluent Limitations
• Average
Effluent
Concentration Limitation
Basis (ppm) (kg/'kkg product)
Maximum
Effluent
Concentration Limitation
Basis (ppm) (kg/kkg product)
Discharge (gal/ ton)
Total Suspended Solids
Oil and Grease
Ammonia (Nj*
Total Cyanide
Phenols
TRC*
Lead
Zinc
pH
75
90
20
20
2.0
0.20
—
0.50
0.55
0.0250
0.00501
0.00501
0.000501
0.0000501
—
0.000125
0.000150
275
50
50
4.0
0.35
0.90
1.5
1.5
0.0751
0.0150
0.0150
0.0010
O.O001
0.00025
0.000375
0.000450
Within the range of 6.0 to 9.0
'Ammonia (N) and Chlorine Residual ITRC) limitations were developed for the alkaline chlorination
alternative only.
Table 6. Summary of Annual Capital and Operating Costs'
Item
Construction Costs
Engineering and Construction Management. 2O%
Contingency, 15% of Construction and Engineering
Total Capital Cost
Amortized Capital Cost (10 yr at 18%)
Annual Operating Costs
Labor
Chemicals
Power
Maintenance (Materials and Labor)
Total
Total Annual Cost
$/1,OOOgal. treated
Hydroxide
Precipitation
571.5OO
1 14.300
85.700
771,500
171,700
70.000
19,000
6,100
7.700
102.800
274,500
$2.51
Direct
Filtration
362,900
72.600
54.400
489,900
109,000
70.000
0
2.000
4.900
76,900
185,900
$1.70
"Based on third quarter of 1981.
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alternatives evaluated were generated
under controlled operating conditions
over 4 days of operation. The test results,
therefore, reflect a very limited range of
influent conditions and pilot plant oper-
ating parameters. Long-term changes in
the raw wastewater composition, tem-
perature, and pH, and variations in treat-
ment plant operation, may produce results
that are different from those observed
during the test period.
Bench tests were conducted with the
objective of pre-establishing certain
operating conditions, primarily chemical
dosage and pH. However, most pilot plant
operating parameters were selected on
the basis of experience to give a practi-
cable and/or reasonably conservative
system, within the constraints of the
existing pilot equipment. Process optimi-
zation was not attempted during the pilot
plant operation.
Comparison of effluent quality achieved
by each treatment alternative with the
BAT limitations was based on average
and maximum values for twelve 8-hour
composite samples of effluent, and not
30-day average and maximum values of
24-hour composites, as would be required
for permit compliance.
In summary, the pilot plant test results
indicate the range of effluent concentra-
tions achievable by the processes tested
with the raw wastewater characteristics
that existed at Armco Steel's sinter plant
during the pilot testing period. The aver-
age and maximum effluent concentra-
tions do not necessarily represent the
levels that can be routinely achieved
industry-wide by a full sized system.
Alkaline Chlorination—A\ka\\r\e chlo-
rination followed by filtration was at-
tempted on the Armco Steel sinter plant
blowdown. The effort was terminated due
to numerous problems and malfunctions
relating to the sinter plant operation.
A field crew was on-site to run the
alkaline chlorination testing in April 1981.
During this time, Armco experienced
many, sudden plant shutdowns. These
unexpected shutdowns caused many
operating problems at the pilot plant. In
addition, due to a strike by ore handlers,
Armco changed from the high lime sinter
burden that is normally used (and which
had been used throughout the study) to a
high iron burden not normally used by the
plant. As a result, representative data
was not collected for the alkaline chlorin-
ation treatment train. The scheduled
move of the pilot trailer to the next test
site prohibited further testing at the
Armco sinter plant to generate the desired
data.
Recommendations
Based on limited data from this study,
optimized BPT clarification to minimize
overflow rates plus polymer addition
followed by filtration is identified as being
most advantageous for the treatment of
sinter plant blowdown. This incorporates
advantages of both processes—the rela-
tively low cost of direct filtration and the
flocculation and additional settling pro-
vided by the hydroxide precipitation
process. It was apparent from the data
that the additional metals removal pro-
vided by the hydroxide precipitation was
due to a reduction in the net residual
suspended solids concentration rather
than the increase in pH since the concen-
trations of soluble metals were virtually
unchanged. Additional testing of this
treatment scheme would provide a more
conclusive data base.
The constraints of short-term piloting
should be recognized. The pilot plant data
base was limited to the wastewater
quality encountered at the time of the
testing and the process operating condi-
tions employed. It was not possible to
develop data for a broad range of waste-
water quality or to optimize process
operation in the short period of pilot
testing. Therefore, augmenting the exist-
ing pilot plant data base with longer term
pilot studies designed to optimize treat-
ment processes and evaluate a reason-
able range of variables (or even full-scale
testing) would be beneficial.
Confirming the data base on a sinter
plant with an acid burden and acid
blowdown would also be beneficial. Many
sinter plants have a blowdown with a pH
that may be as low as 2.0. In such a
system, the makeup of dissolved metals
would be completely different.
Conversion Factors
Although EPA policy is to use metric
units in its documents, certain nonmetric
units are used in this Summary for
convenience. Readers more familiar with
the metric system may use the following
factors to convert to that system.
Nonmetric
ft2
gal.
in.
ton
Times
0.0929
3.785
2.54
907.18
Equals
Metric
m2
I
cm
kg
C. L. Rudasill, K. Brant ner, andS. A. Hall are with Met calf & Eddy, Inc., Boston, MA
02114.
John S. Ruppersberger is the EPA Project Officer (see below).
The complete report, entitled "A It er native Processes for Treatment of Sinter Plant
Wastewater," (Order No. PB 85-211 258/AS; Cost: $10.00. 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:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
U. S. GOVERNMENT PRINTING OFFICE:1985/559-l 11/20605
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United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
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