and
.
PURPOSE
This to
and other site the
of and site to a
for to or
121(b) of the
and Act
(CERCLA) the
tion (EPA) to that
and or
to the and
to In which
and the volume, or of
and as a
This the use of con-
for at
and other this is a
and the
and of wetlands are
diverse.
In
and nutrient
and
and The
is
of alt and The for
and of in
of the United In the of
for treatment. The
in
treatment of well
and are in (EPA
et al, 1995, 1989, and and
1993). the use of
to
as mine is not as
This the use of
of
and
In the of
ogy In the has on the of
and mine The
of and the (TVA)
In the
to
The of is in
(1994) and the TVA are
in (1989)
and (1993), mine
by the Colorado of the of
the of of and
and others. Further, (for
and
to on of the
The of in the
is by of iron
and from the of
by At pH, FeS,,
to air to iron and
a pH of 4,0,
can be
by can
suit ur by 1 in
the
(1) 2
H2O -> 2 Fe2* + 4 SO/ + 4 B*
(2)
can the
Iron In 1 to iron by
2,
2H2G
iron in this can
to iron 3) or
an (FeCOHJj) and
tion 4).
(3)
-------
(4) 2 Fe** + 6 H2O -» 2 Fe(OH)3 + 6 H*
The overall reaction for the oxidation of pyrite is the sum
of 1,2 and 4 (reaction 5).
(5) 4 FeS4 + 15 O2 + 14 HZO -» 4 Fe(OH)s + 16 H* + 8 SO4'
At by equation 5, pyrite weathering a
amount of iron and acidity (low pH) to mine drain-
Moreover, in the of
coal mine discharge typically treat water containing high
(50 to 500 milligrams per liter [mg/L]) of iron and low-
to-moderate pH (4 to 7). Figure 1 provides of
both aerobic and anaerobe constructed wetlandi showing the
primary metal removal mechanisms in system. In
aerobic wetlands, the iron is removed primarily by oxidation
followed by precipitation of iron hydroxides (equations 2 and
4) orjarosite, an amorphous iron sulfate.
The removal of by anaerobic constructed is a
complex combination of chemical precipitation, sorptive and
biologically precipitation In
sufate-reducing within the wetlands produce hydro-
gen sulfide that with metals to form insoluble
and slightly soluble The metal
from the solution and are filtered out by
the solid material (substrate) that up the wetland. The
material's ability to support suHate-reducing bacteria
and filter out the metal is important to the effective-
of the anaerobic constructed wetland.
Table 1 the effectiveness of constructed wetland
technology on general contaminant groups for waters.
of within the contaminant are
provided in the For Treatment of
CERCLA Soils and Sludges (EPA 1988b). However, perfor-
mance in this bulletin may not be directly
to all mining or Superfund Numerous
variables including the type of contamination, concentration of
contaminants, alkalinity within the mine drainage, site climate,
and topography will the of the constructed
wetland A thorough characterization of the contami-
nant through chemical analysis and
geoehemical modeling is highly recommended. In addition, a
well and conducted testability study is also recom-
mended.
Constructed wetlands vary in size and complexity depending
on the wastewater stream to be the capacity required,
and the required level of remediation. There are generally
of constructed wetlands:
(FWS), subsurface flow (SF), and
plant (APS) (EPA 1988a). An FWS (Figure 1
top) typically of shallow or with slow
flowing water and life. An SF wetland (Figure 1 bottom)
typically of or channels filled with a
which the flows through rather than
over as in an FWS. An APS is an FWS with
somewhat channels containing floating or suspended
plants such as water hyacinths or microorganisms such as
The different of can be alone, in
combination, or with other technologies to
a variety of treatment
In general, FWS and APS are that remove
primarily by oxidation of iron followed by
precipitation of iron hydroxidei, which to the removal of
other metals. In addition, anaerobic removal of some
may occur in the of the FWS and APS wet-
lands. FWS and APS are most in
removing iron, manganese, and selenium from mine
with moderately low to neutral pH et al.
1 994). Iron is removed as a hydroxide or as previ-
ously Arsenic and selenium are to sorb to
the iron hydroxide as it and out. Manga-
is removed as an the iron has precipi-
and the hydrogen ion concentration lowered to nearty
neutral conditions (Hedin et al. 1 994). Liming or the
of alkalinity to the through an anoxic limestone drain
prior to the FWS the formation of iron hydroxides and
oxides. Aquatic and microorganisms may
also consume acidity (equation 6) of APS through
photosynthetic activity with similar results.
(6) 106 CO2 + 16 NO"3 + HPO4- + 122 H2O + 18 H* —light -»
Lowering the hydrogen ion concentration to a pH of 9.5 or
greater the rate,
thus enhancing manganese removal from most mine drain-
(Bureau of 1 885),
Figure 2 provides a schematic of a wetland
that may include plants. The various of
In Figure 2 can be in a variety of combinations
to achieve the treatment. This FWS design
by TVA of with a natural or con-
subsurface barrier of clay or impervious geotechnical
(Brodie 1993). The shown in Figure 2
an anoxic limestone drain with and shallow ponds,
a rock filter, and an bed (usually limestone)
to mine drainage. As previously mentioned,
the limestone drain the alkalinity of the mine
drainage, thereby enhancing iron hydroxide precipitation in
the pond and marsh. The alkalinity and
of iron allow manganese to form with removal by
precipitation. Additional fe removed in the rock
filter by adsorption to the rock and by
growing on the rock surfaces. Finally, pH is to
regulatory by chemical amendment in the bed
followed by (TSS) removal in the
polishing cell. The various shown in Figure 2 can be
in any combination to site-specific treatment
requirements.
SF wetlands are anaerobic that vary significantly in
size and complexity. Figure 3 a wetland
constructed in an (Frostman 1993).
A of SF wetland was by simply construct-
ing a of berms and using as a material.
Limestone (Figure 3) can be in confunetion with SF
constructed to the alkalinity, and induce
-------
FIGURE 1: AQUATIC CHEMISTRY OF WETLAND SYSTEMS
AEROBIC
ANAEROBIC UPFLOW
Fto* Direettoii
SRB IMsefes Bacteria
So'*!
Bulletin: Constructed Wetlands Treatment
-------
Notes:
a
OMIiMMllllii
Ilssstip*
' ^
Bll]l00S03,ti8O VOlHM!© 0mSD@llIloS
Jri.isJLQ]KiBii3^8Q so3sivols.tete coiopotiiids
Uoms and finana
Qi^nic «5«iridM
Vdatitemrtb
NcMwdatite metab
Bs;i.^«s5
L^
A
A
D
a
A
*
a
A
a
•
•
a
A
a
a
A
D
raqpert opinion E
caj.
G 1903
-------
3:
' LIMESTONE BED
' LATERAL FLOW DISTRIBUTION
PEAT MIXTURE
PEAT MIXTURE
OPEN WATER POOL
% DIRECTION OF WATER FLOW
LIMESTONE BED
r-"-"-"-1 PEAT MIXTURE TREATMENT
COMTAy 1NATED DRAINAGE
— EXTENT OF WETLAND
FLOW DISPERSION
mot*: eewrauoED WEOMfm fan WMER OUAUTY MFROVEMENT, a. MOSHRI, EDITOR, ins
WATER POOL
WATER POOL
4: OF AN SF
70Z.QEOFMMC
GEOQBID
70LGEOFABRIC
PERFORATED EFFLUENT PIPING
TIE TO GEOGRID '
PERFORATED —
INFLUENT HnNQ
7 ai. QEOFABRIC
QEOHET
QEOSYHTHETIC
OAYLIKER
18m.GEOFABRIO
FRCM: CAMP « McKEE, 1993
SUBSTRATi
-------
TABLE 2
iliipHiSt;
Ag
Al
Cd
Co
Cr
Cu
Fe
Hg
Mg
Mn
Mo
NI
Pb
Zo
Ag,S
AIA
CdS
CoS
NF
Cu,S
FeS
HgS
MgS
MnS
Moft
NiS
PbS
ZnS
-9.36
•117.7
-33.6
-19.8
NA
-20.6
-23.3
-11.7
NB
-49.9
-53.8
-17.7
-22.2
-47.7
lxlO-»
ND
1x10-"
7xlO-»
NA
SxlO"4'
8x10-"
2x10'"
ND
3x10-"
ND
3x10-"
3x10-"
2110*
Notes:
NF
NA
ND
Formation constant (from the dementi) from Garrels and Christ 199(1
Not formed
Not applicable
No data
In general, SF are anaerobic that remove
metal contaminants by reaction with hydrogen sulfide pro-
duced by suifate-reducing forming insoluble metal
sulfides. Table 2 provides metal sulfide formation (from the
elements) and solubility product for common mine
drainage contaminants. The more the
formation constant, the stronger the for the metal
sulfide to form. The indicate that all of
form a sulfide, with the of chromium.
Aluminum, cadmium, iron, molybdenum, and zinc
the tendencies to form however, the
aluminum in environments.
Solubility product the strong tendency of the
metal and the sulfide ion to from aqueous solution.
However, solubility product determinations do not consider
metal complexaton and their use may result in misleading
precipitation or solubility predictions. For example, the
solubility products of HgS and PbS by 25 of
magnitude, but their aqueous solubilities may be quite similar
(Stumm and Morgan 1981}. For these the use of an
aqueous geochemical model, such as MINTEQA2, to evaluate
metal speciation and complexation is encouraged. In addi-
tion, metal removal with SF can be mod-
with MINTEQAK, a program for and
anaerobic wetland modeling (Klusman 1993).
The flow of SF is simple. The
treatment may first flow through a bed of
crushed limestone to alkalinity and
induce metals oxidation and precipitation.
The then flows into the wetland cell
where it flows through the substrate. Depending
on the cell design, the can flow either
vertically up or down or horizontally through the
Within the substrate, inorganic
contaminants are precipitated, or
biologically reduced and The
water then flows out of the cell where it
may flow into another cell or polishing pond.
Generally, of 50 to 100 hours
have successfully in SF wetlands.
Maintaining proper flow of the mine drainage
through the may require frequent
adjustment.
This provides for
constructed wetlands previously
evaluated or currently being evaluated. One of
the first to acid mine
drainage the SIMCO (Coshocton
County, Ohio) in 1985. The
of four by small
followed by larger settling ponds.
The total of the is 4,138
(m*) and is planted with (Typha
The are of 15
centimeters (cm) of crushed limestone overlain
with 45 cm of mushroom compost.
Evaluation of the SIMCO conducted by
from Pennsylvania University indicated removal effi-
ciency has over the 8 of operation
(Stark el al. 1994). Iron removal in were
approximately 20 to 50 percent, and 1991 and 1993
from 70 to 100 percent. removal
not however, a comparison of
mean influent and effluent manganese concentrations
is not removed by the SIMCO con-
wetland.
1984 and 1993, the Bureau of monitored 13
constructed to coal mine drainage.
The of the monitoring are in detail by Hedin
et al. (1994). These include wetlands in
combination with anoxic limestone drains, retention ponds,
and modified ditches. In addition, a variety of
evaluated and the most common
during the The determined
dilution is an important within and
must be determined to accurately evaluate metal removal
The results indicate alkalinity in the mine drainage
improves the wetlands removal of iron. For iron
removal 53 in the effluent from the third cell
of the Latrobe wetland (0 alkalinity in drainage) while iron
removal in effluent from the Donegal
wetland 85 percent. The influent to the
6
-------
wetland contained 202 of and both
of limestone and
compost. Finally, the oxygen transfer Is the
in Iron removal and in
constructed
TVA constructed 14 for at
coal Impoundment 1 (IMP1) is one of 12 TVA
wetlands and at the Fabius coal
IMP1 contains four aerobic cells
and covers 5,700 ma. The has a pH of 3.1, iron
of 69 and manganese of
9.3 mg/L Effluent water from IMP1 wetlands
0.9 of 1.8 mg/L of manganese, and a pH
of 6.7. Originally, five were at IMP1 including
broadleaf wool
rush (Juncus
hyemala), and
Today, more than 70 been
in 1MP1 with the cattail, wool grass,
and rice cutgrass the dominant
plant life. In addition, the stream draining the
than five invertebrate the
stream contains more 30 (Brodie
and minnow
The EPA Innovative
is evaluating upflow and downfiow
SF at the Tunnel, Silver Plume,
The demonstration the operation and
of an at the Big 5 Tunnel
Colorado) within the SITE Technology
Program The mine drainage from the
contains elevated of (45 to 90 mg/L) at a
neutral pH. 3 data for both the
first 12 months of operation. The for the first year
indicate the eel removes better than 99
of the zinc contamination in and fall, and the
removal to 70 in the winter. The
cell 70 to 85 the first year.
In addition, of 48-hour toxicity
and
dub/a Indicate both are the toxicity of the mine
The demonstration of the SF
at the Burieigh Tunnel August 1995.
Technology Status
there are several hundred and natural
wetlands treating coal in the United
The of is in
several publications (1989), Moshiri
the of annual of the
Mining and Reclamation and United
Bureau of (United Bureau of
Publication and et al. 1994).
In addition, many constructed to treat
metal mine been built and or are
by EPA, various and In
Colorado, the of Minerals and has
constructed wetland to
In the of Environmental
a professional for
from coal mine and determined constructed
the best available for the treatment
of alkaline or (Hellier et al. 1994).
wetlands treatment is for the
full-scale remedy of the Tunnel drainage.
A state-of-the-art, has been constructed at
the in the Cornwall of
England. The the Jane abandoned tin
levels of cadmium, and
iron. The design of the wetland Is
similar to the shown in Figure 2. The
with an anoxic by an anoxic drain, then
an cell, by an anaerobic cell, and a
filter. Both the anoxic and the anaerobic
cell use to prevent
cells. The has begun a
2-year period.
EPA has a wetland database that
permit, cell
and for 178 municipal wetland
(EPA
BURLEIGH CONSTRUCTED WETL&HBS
SITE DEMONSTRATION
AVERAGE ZINC CONCENTRATIONS IN 1994 AND
Influent
Upiow
Downflo*
faW*&a&a^«**i^^
56.7
0.16
9.7
62.0
0.28
15.4
fegissk\MfeMS,*,SjJi«s
50.4
0.23
11.5
J-^JSB^^^I^™^™^
49.6
0.24
10.1
58.0
0.24
1B.9
66.1
0.48
14.9
57.0
1.1
16.4
56.6
2.8
14.8
62.9
6.8
12.1
63.0
9.0
8.8
56.3
12.1
9.0
58.0
17.4
11.1
Engineering Bulletin: Constructed Wetlands Treatment
-------
Limitations
Constructed wetland typically have land
requirements compared to conventional treatment
Thus, in with high land values, a constructed wetland
treatment may not be Land
relatively close to the of contaminated water is
to avoid transport of contaminated water.
Land that is relatively level the construction of
wetlands, white with and will
make construction more difficult, costly, and potentially
unsafe.
The climate of potential wetland can limit the
effectiveness and operation of the system. Extended
of cold, extreme hot and arid conditions, and frequent
storms or flooding may in operational and
performance problems. cold can a wetland
and substantially the microbial population, rendering ft
ineffective for an extended period thawing. The
water surface and plant life with wetlands
enhance evaporation and evapotranspiration. A constructed
wetland may dry up at a site with low flow
in a hot and arid location. If the wetland is not
for cyclical periods of wet and dry, it may be less
during the wet periods. Constructing wetlands in with
frequent flooding or storms can lead to washout of
or of the microorganisms to toxic
of metal contamination. Extensive engineering controls
to overcome climatic or geographic limitations may eliminate
the cost and maintenance that
wetlands attractive.
Contaminant and concentrations in the treatment
can be limiting for constructed wetland
High concentrations of contaminants may
shorten the effective life of a constructed wetland, which have
a limited life on the volume of the wetland or the
amount of organic in the wetland.
limitations include the number of for adsorption of
inorganic contaminants and the amount of organic nutrients
for biological activity. The wetland is no longer
the are full and the organic matter is exhausted. At this
point, the wetland must be to remove the
High concentrations of in the
treatment stream may the life of a constructed
wetland. Suspended fill and the
pore reducing permeability and preventing
flow through the treatment in
Cost
In general, there are no typical unit of constructed
due to site-specific conditions and treatment
requirements. The of and construction
required will dramatically the cost. The
with FWS typically to coal mine
are per while for SF wetlands
are on volume. and for
constructing various are reported in the literature
(EPA Hammer Moshiri EPA
An of the wetland was reported as
$3.58/m2 to $32.06fnf of wetland in a study of constructed
wetlands for acid mine drainage treatment by TVA
(Brodie 1988). A cost study of wetlands for treating
at coal mines conducted by the United
Bureau of an cost of approximately
$10.00/m2 of wetland (Kleinmann 1995). Construction
of the SF at the Burieigh Tunnel, Silver
Plume, Colorado to be $570 per cubic meter.
that this cost is on wetland volume. This SF is a
highly engineered with multilayer liners; sophisticated
piping, distribution, and collection and a customized
to year-round at high
(9,150 feet sea level).
Constructing involves common construction tech-
niques and which development of a construc-
tion straightforward. Operation and mainte-
nance are comparatively compared to traditional
treatment systems. One cost that is often overlooked is the
cost of and of the (SF) or
and of bottom (FWS). The
can be significant if the or sediment
is allowed to a due to high metal
concentrations. The cost of or
may be by recovery from the material. If
low-cost, level land is constructed could
be an economical treatment method when compared with
other treatment options.
In conclusion, constructed treatment to be
effective In removing from and toxicity in
Construction to build
are inexpensive and readily Compared to
other treatment constructed may
be a cost-effective alternative.
Acknowledgments
This bulletin was for the United Environmen-
tal Protection Agency, Office of and Development
(ORD) National Risk Management Laboratory
(NRMRL), Cincinnati, Ohio by PRC Environmental Manage-
ment, Inc. (PRC), under contract No. 68-CO-0047. Mr.
as the EPA Technical Manager. Mr. •
Terrence Lyons as the EPA Work Assignment Man-
Mr. Routine was PRC's Project This
bulletin was written by Mr. Garry Farmer and Mr.
of PRC.
The following other Agency and contractor personnel have
contributed their time and comments by in the
review or the engineering
bulletin:
Mr. NRMRL
Dr. Robert Hedin, Hedin Environmental
Mr. Knight-Pjfcold and Co.
Dr. Robert Kleinmann, United Bureau of
Ms. Terry Ruiter, PRC
8
-------
REFERENCES
1. Brad!©, G.A., D.A. Hammer, and D.A. Tom LJanovich.
1988. Constructed Wetlands for Acid Drainage Control
in the Tennessee Valley. United Bureau of
Mines Information Circular 9183, pp. 325-331.
2. Brodie, G.A. 1993. Staged, Aerobic Constructed
Wetlands to Treat Acid Drainage: Case History of
Fabius impoundment 1 and Overview of the TVA
Program. Published in Constructed Wetlands for Water
Quality Improvement. G.A. Moshini. Lewis Publishers.
1993.
3. Camp Dresser and McKee. 1993. Clear Creek
Remedial Design Passive Treatment at Burleigh Tunnel
Draft Preliminary Design Technical Memorandum.
June.
4. Cooper, P.P., and B.C. Findlater, Eds. 1990. Con-
structed Wetlands in Water Pollution Control. Proe. Int.
Conf. on the Use of Constructed Wetlands in Water
Pollution Control. Pergamon Press, Oxford U.K.
5. Eger, P. 1992. The Use of Sulfate Reduction to
Remove Metals From Acid Mine Drainage. Paper
presented at the 1992 American Society for Surface
Mining and Reclamation Meeting. Duluth, MM, June 14-
18.
6. Frostman, J.M. 1993. A Peat/Wetland Treatment
Approach to Addic Mine Drainage Abatement. Pub-
lished in Constructed Wetlands for Water Quality
Improvement. G.A. Moshiri. Lewis Publishers. 1993.
7. R.M. and C.L. Christ. 1990. Solutions, Minerals
and Equilibria. Jones and Bartiett, Boston.
8. Gusek, J.J., J. T. Gormley, and J.W. Sheetz. 1994.
Design and construction of pilot-scale passive
treatment systems for acid roek drainage at metal
mines. Proc. Society of Chemical Industry Symposium.
Chapman and Hall, London.
9. Hammer, D.A. 1989. Constructed Wetlands for
Wastewater Treatment. Lewis Publishers. Chelsea,
Michigan.
10. Hedin, R.S., R.W. Narin, and R.L.P. Kleinmann. 1994.
Passive Treatment of Coal Mine Drainage. United
Bureau of Mines Information Circular 9389.
11. Hellier, W.W., Giovannitti, E.F., and P.T. Slack. 1994.
Best Professional Judgement Analysis for Constructed
Wetlands as a Available Technology for the
Treatment of Post-Mining Groundwater Seeps. United
Bureau of Mines Publication SP 06A-94.
12. Kfeinmann, R, 1995. Personal communication between
Marie Kadnuck (PRC) and Robert Kleinmann.
13. Klusman, R.W. 1993. Computer Code to Model
Constructed Wetlands for Aid in Engineering Design.
Report to United Bureau of Mines, Contract
J0219003.
14. Moshiri, G.A. 1993. Constructed Wetlands for Water
Quality Improvement. Lewis Publishers. Boca Raton,
Florida.
15. Reed, S.C., R.W. Crites, and E.J. Middlebrooks. 1995.
Natural Systems for Waste Management and Treat-
ment, 2nd Edition. McGraw-Hill, New York.
16. Stark, L.R., P.M. Williams, S.E. Stevens, Jr., and D.P.
Eddy. 1994. Iron Retention and Vegetative Cover at
the SIMCO Constructed Wetland: An Appraisal Through
Year Eight of Operation. United Bureau of Mines
Publication SP 06A-94.
17. Staub, M. and R.R.H. Cohen. 1992. A Passive Mine
Drainage Treatment System as a Bioreaetor. Treatment
Efficiency, PH Increase and Sulfate Reduction in Two
Parallel Reactors. Paper presented at the 1992
National Meeting of the American Society For Surface
Mining Reclamation, Dulirth, MN. June 14-16, 1992.
18. Stumm, W. and J.J. Morgan. 1981. Aquatic Chemistry.
John Wiley and Sons, Inc. New York, New York.
19. United States Bureau of Mines. 1985. Control of Acid
Mine Drainage. Information Circular, 1C 9027.
20. United Environmental Protection Agency (EPA).
1988a. Constructed Wetlands and Aquatic Plant
Systems for Municipal Wastewater. EPA/625/1-88/022.
1988.
21. EPA. 1988b. Technology Screening Guide for Treat-
ment of CERCLA Soil and Sludges. EPA/540-2-88/
OU4. 1988. pp. 86-89.
22. EPA. 1993. Handbook for Constructed Wetlands
Receiving Add Mine Drainage. EPA/5401 R-93/523.
September 1993.
23. EPA. 1994. Wetlands Treatment Database. EPA/600/
6-94/002. June 1994.
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Environmental
(G-72)
Cincinnati, OH
Official
Penalty for Private Use
$300
& PAID
EPA
No. G~35
EPA/540/S-96/501
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