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United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
'W
Research and Development
EPA-60O/S2-84-137 Sept. 1984
SERA Project Summary
Toxicity Treatability of Iron and
Steel Plant Wastewaters:
A Resource Document
B. H. Carpenter, M. R. Branscome, C. W. Westbrook, W. F. Gutknecht, and
A. Gaskill
The full report documents an assess-
ment of the biotoxicity reduction and
concurrent pollutant reduction achieved
by 24 wastewater treatment systems
serving 8 iron and steelmaking process
subcategories. Sampling programs, de-
signed to provide measurements before
and after successive unit treatment
processes, were conducted at seven
plants. Chemical analyses were per-
formed for conventional, priority, and
regulated pollutants. Additional tests
were made to identify other potentially
harmful metals and organics. Bioassays
were performed using both minnows
and daphnia. The results of chemical
analyses were compared with toxic
concentration limits in relating biotoxic-
ity to pollutant concentrations.
Cokemaking wastewater treatment
systems tested that employed single-
stage bioreaction yielded more highly
toxic effluents than did the physical/
chemical treatment. Ironmaking waters
treated to below 2,000 fjg/L total
metals were nontoxic to minnows.
Steelmaking waters after flocculation
and clarification retained toxic levels of
lead and zinc. Hot forming wastewaters
showed low biotoxicity where metal
concentrations were reduced sufficient-
ly. Cold forming wastewaters showed
varying biotoxicities associated with the
levels of oil and grease, organics, and
metals remaining after treatment. Treat-
ment studies for hot coating and pick-
ling wastewaters showed good reduc-
tion of biotoxicity.
This Project Summary was developed
by EPA's Industrial Environmental He-
search 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 infor-
mation at back).
Introduction
Raw wastewaters from iron and steel-
making processes have been shown to
contain potentially biotoxic pollutants.
Outfall compliance data identify toxicities
that persist after currently applied treat-
ments. Treatments have been assessed
for removal of identified and regulated
pollutants, but not for concurrent reduc-
tion of biotoxicity. As part of EPA's
industry-specifictoxicity information pro-
gram, this study develops data on waste-
water toxicity, its treatability, and its
variability from eight iron and steelmaking
process subcategories.
With the cooperation of the plants,
wastewater treatment systems were se-
lected to include eight iron and steel-
making process categories: cokemaking,
ironmaking, steelmaking, continuous cast-
ing, hot forming, pickling, cold forming,
and hot coating. Many technologies in-
cluded in the treatment systems were
representative, to some extent, of BPT,
BAT, or NSPS. Several systems were
chosen to identify possible limitations in
biotoxicity removal. Each study was car-
ried out while the production facility was
operating at rates reasonably represent-
ative of normal production.
Wastewater treatment systems in steel
plants are somewhat unique. While those
studies use many of the unit processes
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inherent in BPT and BAT models, a
complete match, process by process,
seldom exists. Selected systems included
processes that have been shown to
decrease pollutant loadings.
Samples were taken upstream and
downstream of treatment system unit
processes. Composite samples were ob-
tained using automatic samplers except
where work areas were designated haz-
ardous. Composites in such areas were
made from a sequence of grab samples.
Grab samples were also taken to prevent
loss of cyanide, volatile organics, and oil
and grease through degradation that
might occur during composite sampling.
Containers were packed in ice for
immediate delivery to testing laboratories,
and were analyzed within prescribed
holding periods.
Ten percent of the composite samples
taken were split for chemical analyses by
the two laboratories involved, for quality
control purposes. All sampling and ana-
lyzing were done according to a compre-
hensive quality assurance plan prepared
for the study.
Summary and Conclusions
Analytical results indicated that the
wastewaters sampled were generally
representative of their respective process
subcategones. While some raw vyaste-
waters were markedly different from
median values developed previously, the
overall characterizations show typical
subcategory trends.
Toxicity and pollutant reductions affect-
ed by treatments were determined, and
are presented in detail in the full report.
Where treated wastewaters remained
toxic, pollutants with remaining concen-
trations greater than toxic limits previous-
ly determined in other studies are given
here. These are identified as probable
causes. Using this method, little evidence
of synergistic effects was found. That is,
where several toxic pollutants remained
just below their toxic limits, their com-
bined presence did not appear to induce
higher biotoxicity.
Cokemaking
Three treatment systems were studied:
two using single-stage bioreaction (no
nitrification), and one using physical/
chemical treatment.
Plant C's bioreactor feed is first cooled
and diluted with river water. The two
parallel biobasins used 136 aerators.
Retention time was 62 hours. Effluent
was clarified after polymer addition.
Toxicity (LCso) to minnows was reduced
from 0.61 to 3.8; daphnia ECso was not
reduced significantly (<1 to 1.5). Am-
monia, cyanide, and benzo(a)pyrene were
reduced39,6, andO percent, respectively,
and all were above toxic concentrations
in the treated waters.
Plant D's bioreactor feed was diluted
also. Less aeration was used, and reten-
tion time was 32 hours. Bioreactor ef-
fluent passed through a thickener before
discharge. Upsets in operation permitted
carryover of solids, and initial toxicities
were higher than those from later re-
samples. Toxicity to minnows was re-
duced from 0.17 to 32.3; for daphnia,
from 0.16 to 31. Remaining biotoxicity
coincides with concentrations of ammo-
nia, phenol, benzo(a)pyrene, cyanide, and
zinc that exceed toxic limits.
Plant G's treatments include equaliza-
tion, clarification, filtration, carbon ad-
sorption, and alkaline chlorination. Equal-
izer holding time was 24 hours; clarifier
overflow, 0.0037 mVmin; filter flow-
through, 0.045 mVm2 x min; adsorber
flowthrough, 0.09 m3/m2 x min; and
chlorinator detention time, 2.8 hours.
M innow LC50 was reduced from 0.85 to
71.5; daphnia ECso was not reduced, and
remained at 5.3. Residual chlorine, cya-
nides, and copper (extraneously in-
troduced) all exceeded-toxic concentra-
tions in the final effluent.
Ironmaking
Plant A's recycle system uses thicken-
ers (holding time 3.6 hours) with polymer
addition and sludge recycle. Overflow
passes to a cooling tower and makeup.
Slowdown is clarified and chlorinated,
then used for coke quench. No reduction
in biotoxicity to either minnows (21.6) or
daphnia (6.8) was shown. Chlorine and
zinc remained above toxic limits, although
the latter was 98.8 percent removed.
Plant D's treatments included floccula-
tion and thickening, with an overflow rate
of 0.03 mVm2 x min at a flow rate of 56.8
mVmin. Raw and treated waters were
nontoxic to minnows; EC5o's were 42 for
daphnia. Ammonia, lead, and zinc ex-
ceeded criteria or toxic limits.
Steelmaking
Two treatment systems were studied at
Plant A.
That for a suppressed combustion
process used hydroclones, settlers, poly-
mer addition, and thickening (5-hour
holding time). Minnow LCso's were 71 on
treated waters; daphnia EC5o's, 58.6.
Phenol, lead, and zinc were 0, 99, and
99.4 percent removed, respectively, but
still exceeded toxic concentrations. Am-
monia (60 percent removed) at 0.4 mg/L
may have contributed to toxicity.
The system for wet open combustion
used thickening after polymer addition,
and pH adjustment. Slowdown passed
through a second thickener. Minnows
survived in a 65 percent dilution; daphnia
EC50 was >32. Ammonia, lead, and zinc
were 65, 93, and 98 percent removed,
respectively, but remained above toxic
concentrations.
Continuous Casting
Plant B's treatments were: scale pits,
deep bed filters (walnut shells), cooling
towers, and recycle. Raw and treated
water were nontoxic to minnows. Daphnia
were killed in a 60 percent sample.
Ammonia, zinc, and copper were removed
0, 30 and 10 percent, respectively, and
remained slightly above toxic limits.
Plant E's treatment included: scale pits,
deep sand filters, cooling towers, and
recycle. Minnow LCso's were unchanged
at 2.4-2.75; daphnia ECso's remained at
6.2-6.6. Nickel, zinc, and copper were
removed 7, 17, and 13 percent, respec-
tively, but remained above toxic concen-
tration limits.
Hot Strip and Cold Rolling Mills
Plant A treated combined hot and cold
rolling wastewaters using scale pits, oil
skimming, flocculation with alum and
polymer, and clarification (1.6 hours
retention). Then a central treatment was
applied to these and waters from the
slabbing mill. This included scalping with
chlorination and settling basins. Minnows
survived in 64 percent raw and treated,
hot-forming wastewaters; daphnia
showed an EC5oof >32. Residual chlorine
may have contributed to the toxicity.
The cold rolling raw wastewater showed
a minnow LCso of 0.45 and a daphnia ECso
of 8.3. Further increases in toxicity were
shown after sump waters were added.
Tetrachloroethylene, lead, nickel, and
zinc were reduced 0, 65, 26, and 13
percent, respectively, from their above
toxic levels by treatment and dilution (31
times) with hot-forming wastewaters. After
central treatment, the biotoxicities were
essentially the same as those of the raw
hot-forming wastewaters.
Plant D combined slabber and scarfer
wastewaters with those from hot-form-
ing, and applied oil skimming and filtra-
tion using sand and anthracite coal.
Minnow LC50 was 35 on filtered waters;
daphnia, >32. Ammonia, nickel, and zinc
were removed 41,51, and >75 percent.
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respectively, but remained above toxic
concentration limits.
Plant F applied scale pits, settling, oil
skimming, and deep-bed filtration to hot-
forming wastewaters. Neither the raw
nor the treated wastewaters were bio-
toxic. Ammonia, nickel, and zinc were
removed 0, 73, and 89 percent, respec-
tively, but their remaining concentrations
slightly exceeded some toxicity limits.
Slabbing Mills
Plant A's slabbing mill wastewaters
were combined with hot-strip mill waters
for treatment. Raw wastewaters from the
slabbing mill were only slightly toxic to
minnows; the EC5o for daphnia could not
be calculated due to inappropriate choice
of dilutions for the test, but was reduced
by treatment. Ammonia was not reduced
and exceeded toxic limits.
Plant B applied scale pits, polymer
addition, and settling basin with oil
skimming. Raw and treated waters were
nontoxic to minnows and daphnia. Lead
and nickel were reduced 67 and 36
percent, respectively, but remained very
slightly above toxic limits.
Section Mills
Plant A applied scale pits, oil skimming,
clarification, dilution, and cooling. Raw
and treated waters were nontoxic to
minnows; toxicity to daphnia was not
defined. Metals were reduced 97 percent.
Ammonia remained at <0.4 mg/L.
Plant E applied oil skimming, cooling,
and recycle, with blowdown to central
treatment with combined wastewaters.
The waters were not toxic to minnows
and only slightly toxic to daphnia before
and after oil skimming.
Pickling
Plant F (combination acids) applied
neutralization, polymer addition, clarifi-
cation, and dilution to raw wastewaters.
Treated waters were nontoxic to min-
nows, and 75 percent of the daphnia
survived in 100 percent sample. Ammonia
and nickel were reduced 0 and 99.6
percent, respectively, but remained above
toxic limits.
Plant B (hydrochloric acid) combined
these wastewaters with cold-rolling wa-
ters and applied oil skimming, air oxida-
tion, neutralization with lime, and clar-
ification after polymer addition. Minnow
LC5o was reduced from 8.8 to nontoxic;
daphnia, from 90 percent killed in a 6
percent sample to 100 percent killed in a
,95 percent sample. The pH was low after
treatment. Final toxicity may have been
due to additives that were not determined
in the analyses.
Cold Forming
Plant A applied oil skimming, followed
by a central treatment of combined waste-
waters. Raw waters were nontoxic to
minnows, as were treated waters. Daph-
nia ECso was reduced only to 4.2 by
treatment. High oil and grease and other
organics are suspected causes of remain-
ing toxicity.
Plant B's cold-rolling system was dis-
cussed under Pickling, above.
Hot Coating
Plant C applied equalization, neutral-
ization with lime, and clarification with
polymer. The effluent was nontoxic to
minnows and daphnia, although zinc (98
percent removed) remained above toxicity
limits.
Central Treatment
Plant E's combined waters for central
treatment showed a minnow LDSO of 2.4
and an ECso for daphnia of 0.1. Central
treatment applied chrome pretreatment,
cyanide pretreatment, equalization, neu-
tralization with caustic and acid, floc-
culation with polymer, clarification and
surface skimming. Minnows survived 65
percent in a 100 percent sample; daphnia
ECso was 38. Ammonia, chlorine, and
nickel were reduced 0, 0, and 99.5
percent, respectively, but remained above
toxic concentration limits.
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B. H. Carpenter et at. are with Research Triangle Institute, Research Triangle Park,
NC 27709.
David C. Sanchez is the EPA Project Officer (see below).
The complete report, entitled "Toxicity Treatability of Iron and Steel Plant
Wastewaters: A Resource Document," (Order No. PB 84-232 495; Cost:
$13.00, 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:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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