United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-85/001 Apr. 1985
&ERA Project Summary
Evaluation of At-Sea Disposal of
FGC Wastes
C. B. Cooper, R. R. Lunt, I. Bodek, and C. J. Santhanam
This two-volume report is the third in
a series of reports on a continuing EPA
research program on the feasibility of
the disposal of flue gas cleaning (FGC)
wastes in the ocean. Volume 1 gives
results of laboratory-scale chemical
and biological experiments (by Arthur
D. Little, Inc. and the New England
Aquarium's Edgerton Research Labora-
tory) with untreated (unstabilized FGC
wastes designed to provide basic data
on environmental impact potential.
Volume 2 gives results of further chem-
ical and biological tests with a forced-
oxidation (sulfate-rich) FGC waste and
with stabilized FGC wastes.
Results of tests performed to date, as
well as related assessment efforts, indi-
cate that the conventional (concen-
trated-dump) at-sea disposal of un-
stabilized FGC wastes with soil-like
properties on the Continental Shelf ap-
pears to be environmentally undesir-
able, unless contradicted by further
work. Test results also indicate that at-
sea dispersed disposal of sulfate-rich
(and, possibly, sulfite-rich) soil-like
FGC wastes is sufficiently promising to
merit further research. Likewise, re-
sults of this and other programs indi-
cate that conventional or concentrated
disposal of brick-like stabilized FGC
wastes is also promising.
This Project Summary was devel-
oped by EPA's Air and Energy En-
gineering Research Laboratory, Re-
search Triangle Park, NC, 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).
Background
This is the third in a series of reports on a
research program, sponsored by the U.S.
Environmental Protection Agency, on the
feasibility of the disposal of Flue Gas Clean-
ing (FGC) wastes from coal-fired power
plants botft in mines and at sea. The first
two reports presented findings concerning
both in-mine and at-sea disposal. The first
report consisted of issue identification for
future research, based on a review of avail-
able information. The second report includ-
ed results of original physical and chemical
testing as well as additional assessment of
available literature. This report, in two
volumes, describes subsequent investiga-
tions of at-sea disposal by Arthur D. Little,
Inc. (ADD and the Edgerton Research
Laboratory of the New England Aquarium
(NEA).
The first report identified four en-
vironmental impact categories of concern
in the potential at-sea disposal of FGC
wastes from coal-fired power plants: ben-
thic sedimentation, suspended waste in the
water column, sulfite-related toxicity and
oxygen depletion, and trace contaminants.
The second report focused on physical
and chemical investigations of unstabilized
FGC wastes in seawater. Testing and
assessment efforts emphasized three sub-
ject areas: the physical fate of unstabilized
FGC wastes in the water column (i.e., the
hypothetical "column" of water between
the ocean surface and the ocean bottom),
the physical fate of unstabilized FGC
wastes on the ocean bottom, and the
chemical fate of unstabilized FGC wastes in
seawater.
Overall conclusions of the first two re-
ports emphasized the need for case-by-
case analyses of prospective at-sea disposal
of FGC wastes, along with the following
more specific conclusions:
• The conventional disposal of unstabil-
ized FGC wastes with soil-like physical
properties on the Continental Shelf ap-
peared to be environmentally unac-
-------
ceptable, without further contradictory
evidence.
• Problems of at-sea disposal of sulfite-
rich FGC wastes, particularly those re-
lated to oxygen depletion, appeared to
be much greater than the problems
associated with other FGC wastes.
• Disposal options which appeared
promising and worthy of further
research included:
—dispersed disposal of unstabilized
sulfate-rich and stabilized brick-like
FGC wastes on the Continental
Shelf;
— concentrated disposal of brick-like
FGC wastes; and
—disposal of unstabilized sulfate-rich
FGC wastes in the deep ocean.
Part 1 Purpose and Scope
This third phase of the program was
designed to fulfill several research needs
identified in the earlier assessments. Part 1
experiments were designed to study:
1. acute toxicity of unstabilized FGC
wastes to marine water column
organisms;
2. chronic toxicity and substrate suitabil-
ity of unstabilized FGC wastes of
marine benthic organisms; and
3. leaching behavior and bioaccumula-
tion of trace contaminants from FGC
wastes in seawater.
One series of tests consisted of
measurements of the acute toxicity of un-
stabilized FGC wastes to marine zooplank-
ton and finfish, with the wastes maintained
in suspension of the water column. The
second series of tests was conducted in
two parts. First, leaching tests were con-
ducted to determine the amounts of
selected metallic trace contaminants that
could leach from the wastes under different
mixing conditions. Then, 6-week exposure
tests were performed in flow-through
seawater systems with partial FGC waste
substrates and marine benthic plants, in-
vertebrates, and finfish. Organisms and the
water column were monitored for the trace
metals for the duration of the tests. The
wastes tested are shown in Table 1.
Part 1 Results
Suspended Sediment Impacts
The results of toxicity testing with sus-
pended wastes and water-column organ-
isms indicated that there are unlikely to be
significant differences between the water
column impacts of descending, sulfate-rich
FGC wastes and impacts presently experi-
enced in disposal of dredged materials.
Specifically, test results were obtained for
marine/estuarine species with documented
high sensitivity to suspended sediment im-
pacts; i.e., the zooplankton Acartia tonsa
and the filter-feeding fish Menidia menidia.
The toxicity values upon exposure of these
species to suspended sulfate-rich, soil-like
FGC wastes were in the same range as
those obtained by other investigators upon
exposure of the same species to suspen-
sions of various natural soils under com-
parable test conditions.
However, exposure of the same species
to agitated suspensions of sulfite-rich,
unstabilized FGC wastes produced dramat-
ic oxygen depletion and organism mortal-
ity. The latter results suggest that conven-
tional release of descending masses of un-
stabilized, sulfite-rich FGC wastes could
lead to toxic phenomena in the ocean water
column, depending on the degree of attrac-
tion to or voluntary avoidance of the
descending masses by disposal site organ-
isms. Dispersed, rather than conventional,
disposal of these wastes, or disposal fol-
lowing stabilization, are possible means of
mitigating this impact potential.
SuIfite-Related Oxygen
Depletion on the Ocean Bottom
Results of month-long exposure tests
with benthic marine organisms reinforced
earlier concerns over the potential adverse
effects' of sulfite-related oxygen depletion.
In circumstances where unstabilized,
sulfite-rich FGC wastes comprised 25 per-
cent or more of the test tank substrate, fin-
fish agitated the wastes sufficiently to lead
to oxygen depletion and organism mortal-
ity. However, in circumstances where the
wastes comprised smaller areas of the tank
substrate, voluntary avoidance and an I
absence of oxygen depletion and organism
mortality prevailed throughout the tests.
These results suggest that dispersed
disposal combined with voluntary avoid-
ance may provide means of mitigating the
oxygen-depletion impact potential of
unstabilized, sulfite-rich FGC wastes, but
field-scale observations would be needed to
evaluate this possibility.
Trace Contaminant Impacts
The results of the exposure tests con-
cerning leaching, toxicity, and bioaccumu-
lation of trace metals varied for the several
chemicals and wastes investigated. As
shown in Table 2, the exposure conditions
associated with one unstabilized, sulfate-
rich waste resulted in extensive mortality of
experimental invertebrates (clams and
snails), but had no comparable effect on
finfish (flounder). There was no apparent
explanation for the observed toxicity of this
one sulfate-rich waste: the measured levels
of trace metals in the water column were
within the non-toxic range observed by
other researchers working with other com-
parable metal mixtures and the same
marine organisms. Possible explanations in-
cluded the presence of high levels of an
unmeasured chemical (e.g., copper) or the
contamination of the waste sample in some
other manner not detectable by traditional
bulk or trace metal analysis.
There was an absence of toxicity and sig-
nificant bioaccumulation associated with
the leaching of nickel and zinc in tests with
FGC wastes relatively rich in these constitu-
ents (compared with the full range of data
on the FGC wastes). This result suggested
that the levels of nickel and zinc, two trace
contaminants identified as potential pro-
blems in the earlier work, would be likely to
preclude at-sea disposal of FGC wastes.
Results of cadmium and selenium indi-
cated continuing release and bioaccumula-
tion of these chemicals when tested with
some of the experimental FGC wastes in
seawater. These results indicated that fur-
ther testing of FGC wastes relatively rich in
Table 1. FGD Waste Samples Used In Laboratory Testing
Process Source
Dual Alkali
Direct Lime
Direct Lime
Direct Limestone
Direct Limestone
(forced oxidation)
Acid Scrubbing
Sample
Code
DAI
LI
L2
LS2
LS3
G1
Waste Type
Sulfite-Rich (without ash)
Sulfite-Rich (with ash)
Sulfite-Rich (without ash)
Sulfite-Rich (without ash)
Sulfate-Rich (with ash)
Sulfate-Rich (without ash)
Waste Form
Filter Cake
Filter Cake
Filter Cake
Thickener Underflow3
Filter Cake
Centrifuge Cake
Acute
Toxicity
—
—
X
X
—
X
Thirty-Day
Exposure
X
X
—
—
X
—
aSett/ed
-------
these metals would be required to evaluate
fully their long-term impact potential.
Part 1 Conclusions
Overall conclusions regarding the need
for case-by-case disposal evaluations 'and
the technical feasibility of control options
were still considered valid. Other specific
conclusions were:
• The concentrated disposal at sea of
unstabilized FGC waste with soil-like
physical properties still appears to be
environmentally unacceptable, unless
contradicted by further work.
• The problems of disposal of sulf ite-rich
FGC wastes still appear considerable,
but dispersal appears to be a potential-
ly useful control option.
• The potential release of some trace
contaminants remains a valid concern
that could preclude at-sea disposal of
FGC wastes. This concern does not
appear to extend to nickel and zinc.
• Dispersed disposal at sea of all forms
of FGC wastes and concentrated dis-
posal at sea of stabilized brick-like FGC
wastes appear promising.
• Conventional disposal of unstabilized
sulfate-rich FGC wastes in the deep
ocean may be promising, but needs to
be reconsidered after further testing to
determine if the toxicity of one such
waste in this program was an isolated
phenomenon.
Part 1 Recommendations
The more important research needs iden-
tified from these investigations were:
• further bioassay data on sulfate-rich
FGC wastes;
• further leaching and bioassay data on
selected FGC waste trace con-
taminants;
• limited field-scale tests to investigate
avoidance responses and trace con-
taminant update;
• parallel data for stabilized FGC wastes;
and
• continued investigations of any full-
scale field situations where FGC
wastes have entered or been placed in
marine environments.
Part 2 Purpose and Scope
Three of the research needs identified in
the Part 1 study were addressed in Part 2:
1. Development of further bioassay data
Table 2. Animal Morta/ity Record Long- Term Exposure Test
Date Number Organism
Tank No.
Waste
July 3
July 5
July 6
July 7
July8
July 11
July 12
July 20
July 21
July 24
July 25
2
1
1
1
1
2
1
1
1
3
2
1
1
1
1
J
Pseudopleurenectes
Littorina
Mya
Littorina
Mya
Mya
Littorina
Mya
Littorina
Littorina
Littorina
Littorina
Littorina
Mya
Mya
Littorina
Littorina
Mya
1
8
6
6
6
6
6
5
5
6
6
8
6
overflow tank
6
8
overflow tank
Control
Control
LS3a
LS3
LS3
LS3
LS3
LS3
DAI
DA1
LS3
LS3
Control
LS3
LS3
LS3
Control
LS3
July 26
July 27
August 7
1
1
1
1
1
Mya
Littorina
Mya
Littorina
Mya
overflow tank
5
overflow tank
5
overflow tank
LS3
DA1
LS3
DA1
LS3
aSee Table 1 for Waste Sample Code.
on the type of unstabilized sulfate-rich
FGC waste that had been associated
with high levels of organism mortality
in previous testing;
2. Development of further leaching and
bioassay data on selected FGC waste
trace metals in seawater; and
3. Development of chemical and bio-
assay data parallel to that from earlier
studies, this time for a representative
selection of stabilized FGC wastes.
During the timeframe of the investiga-
tions reported in this series, investigations
of at-sea disposal of stabilized FGC wastes
continued at the State University of New
York (S.U.N.Y.) at Stony Brook, under the
sponsorship of various agencies. The
S.U.N.Y. work involves a series of
laboratory and limited field-scale studies of
the physical and chemical characteristics
and ecological impact potential of artificial
reefs made of brick-like, sulfite-rich FGC
wastes stabilized by a modified version of
the Conversion Systems Inc. (CSI) process.
This work, collectively, is referred to as
the Coal-Waste Artificial Reef Program
(C-WARP).
The investigators for this study main-
tained cognizance of the S.U.N.Y. work,
and attempted to design their experiments
so as to complement, rather than duplicate,
that work. In particular, Part 2 focused on
the study of soil-like (rather than brick-like)
stabilized FGC wastes, and sulfate-rich
(forced-oxidation) wastes, neither of which
were studied by S.U.N.Y.
Part 2 Results
Benthic Sedimentation Impacts
The results of the Part 2 thirty-day ex-
posure tests with both unstabilized and
stabilized, soil-like FGC wastes included
observations of voluntary use (in some
cases preferential) of these wastes as
substrates by facultative, benthic marine
organisms which would otherwise inhabit
various or fine-grained natural substrates
(i.e., clams and worms). No examples of
waste avoidance by these organisms were
observed. These observations tend to in-
dicate that the physical characteristics of
soil-like FGC wastes are compatible with
use by facultative marine organisms at
dumpsites set in other fine-grained
sediments. However, there are still no data
to contradict the expectation that fine-
grained, soil-like FGC wastes would prove
unsuitable substrate for indigenous organ-
isms if concentrated on areas of the ocean
bottom that would otherwise be covered by
coarse sand and/or reef substrates.
-------
Sulfite-Related
Oxygen Depletion
The investigation of oxygen depletion by
sulfite-rich stabilized wastes in Part 2 in-
dicated that such depletion would occur
with these wastes, but to a lesser degree
and at a slower rate than previously
measured for unstabilized, sulfite-rich
wastes. Higher slurry concentrations of
stabilized versus unstabilized wastes were
required to produce oxygen depletion, and
the time required to deplete the available
oxygen increased by factors of about two
to five, even at the higher slurry concentra-
tions. No oxygen depletion below 5.8 ppm
was experienced in any of the 30-day ex-
posure tests with sulfite-rich stabilized
wastes. However, the wastes were not sub-
jected to the same degree of bio-turbation
in the Part 2 tests that had prevailed and
proved problematic in Part 1.
Trace Contaminant Impacts
The results of the leaching and biological
exposure testing in Part 2 tended to confirm
(for additional stabilized and unstabilized
FGC wastes) the Part 1 findings with
respect to nickel and zinc, and to indicate
leaching behavior and implications similar
to those for nickel and zinc with respect to
copper. For all three of these metals, the in-
cremental changes in ambient seawater
concentrations were below the levels re-
ported to cause adverse ecological effects
in the marine environment and, in some
cases, resulted in net decrease over
background levels.
There were no apparent waste-related
test organism mortalities in the Part 2 tests.
These results, particularly for the two
wastes that were physically and chemically
comparable, the toxic sample of sulfate-
rich unstabilized wastes used in Part 1, tend
to reinforce the hypothesis that the toxicity
of that Part 1 sample was a relatively unique
phenomenon.
Results for other trace metals, notably
arsenic, cadmium, chromium, and seleni-
um, were inconclusive. There was an ab-
sence of these elements over the 30-day ex-
posure period in the Part 2 tests. However,
the concentrations of these elements were
continuing to rise in one or more test
species at the conclusion of the tests.
Stabilization appeared to reduce the
availability of cadmium for seawater leach-
ing, but appeared to have little or no effect
on the availability of other elements, in-
cluding chromium and selenium.
Part 2 Conclusions
Principal conclusions of this part of the
study were:
• The overall conclusions of the earlier
assessment are still considered valid;
i.e., there remains a need for case-by-
case analyses of prospective at-sea
disposal of FGC wastes and the viabil-
ity of available control options.
• The at-sea disposal of stabilized,
sulfite-rich FGC waste appears to be
environmentally preferable from the
standpoint of sulfite-related oxygen
depletion. Mitigation by dispersed dis-
posal may be feasible and necessary,
but requires field-scale investigation.
• The previously observed incidence of
contamination-related acute or sub-
chronic toxicity associated with one
sample of a sulfate-rich, unstabilized
FGC waste appears to have been
highly waste-specific. Such toxicity
should not be expected for a broad
spectrum of sulfate-rich FGC wastes,
and can be evaluated case-by-case
with required, standard at-sea disposal
bioassays.
• The limited potential for near-term
release and accumulation of copper,
nickel, and zihc from either unstabil-
ized or stabilized FGC wastes appears
unlikely to constrain at-sea disposal of
these wastes.
• The data suggest that leaching of
arsenic, cadmium, chromium, and
selenium appears to be within environ-
mentally acceptable limits for relatively
short-term exposures, but leave open
some questions about the impacts of
prolonged exposure.
• FGC waste stabilization by addition of
lime and fly ash appears to be a poten-
tially effective means of mitigating im-
pacts associated'With the release of
some trace metals (e.g., cadmium) but
not others (e.g., selenium, chromium).
• Disposal options which continue to ap-
pear promising include:
— dispersed disposal of all forms of
FGC wastes on the Continental
Shelf or in the deep ocean;
—conventional or concentrated dis-
posal of stabilized FGC wastes on
the Continental Shelf or in the deep
ocean; and
—conventional or concentrated dis-
posal of unstabilized, sulfate-rich
PQC wastes in the deep ocean.
Part 2 Recommendations
The following research needs were iden-
tified based on Part 2:
• Limited field-scale tests with sulfite-
and metal-rich FGC wastes would be
of value in investigating the impor-
tance of:
1. organism avoidance responses as ^
potentially mitigative of sulfite-re- •
lated toxicity of sulfite-rich FGC
wastes; and
2. longer-term chronic uptake and
toxicity of arsenic, cadmium,
chromium, and selenium leached
from FGC wastes under more repre-
sentative conditions for leaching
and water exchange.
Investigation of any field situations
where FGC wastes have entered or
been placed in marine environments
would contribute to current knowledge
of the subject.
OUSGPO: 1985 — 559-111/10808
-------
C. B. Cooper. R. R. Lunt, I. Bodek. andC. J. Santhanam are with Arthur D. Little,
Inc., Cambridge. MA 02140.
Julian W. Jones is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Evaluation of At-Sea
Disposal of FGC Wastes:"
"Volume 1. Biological Testing and Studies with Untreated Wastes," (Order
No.PB 85-156 180/AS; Cost: $16.00)
"Volume 2. Biological Testing and Studies with Stabilized Wastes," (Order
No. PB 85-156 198/AS; Cost: $11.50)
The above reports will be available only from: (costs subject to change)
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
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Bu's'fFkess
Penalty, fof-Private. Use S300
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U S ENV1R PROTECTION AGENCY
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